Beam Bridge: Middle and West Spans. A thesis presented to. the faculty of. In partial fulfillment. of the requirements for the degree

Transcription

1 Destructive Testing of a Full-Scale 43 Year Old Adjacent Prestressed Concrete Box Beam Bridge: Middle and West Spans A thesis presented to the faculty of the Russ College of Engineering and Technology of Ohio University In partial fulfillment of the requirements for the degree Master of Science Jonathan M. Huffman March Jonathan M. Huffman. All Rights Reserved.

2 2 This thesis titled Destructive Testing of a Full-Scale 43 Year Old Adjacent Prestressed Concrete Box Beam Bridge: Middle and West Spans by JONATHAN M. HUFFMAN has been approved for the Department of Civil Engineering and the Russ College of Engineering and Technology by Eric P. Steinberg Associate Professor of Civil Engineering Dennis Irwin Dean, Russ College of Engineering and Technology

3 3 ABSTRACT HUFFMAN, JONATHAN M., M.S., March 212, Civil Engineering Destructive Testing of a Full-Scale 43 Year Old Adjacent Prestressed Concrete Box Beam Bridge: Middle and West Spans Director of Thesis: Eric P. Steinberg A 43 year old, three span prestressed concrete adjacent box beam bridge ( ) in Washington Court House, Ohio, needed to be replaced and was considered to be a good candidate for full scale destructive field testing to better understand how this type of bridge behaves under varying magnitudes of damage. Three magnitudes of damage were created on the spans of the bridge for comparison. However, the scope of this study only covers the center and west spans. Each span was then subjected to loading to monitor how load was transferred to other beams and until the span was unable to resist any additional load to determine the overall capacity of each span. All beams of the bridge were instrumented with strain gages to record strains as well as string potentiometers to observe deflections of the beams as the spans were loaded. It was observed the capacity of each span was also comparable to the estimated capacity of each span with the applied damage. It was concluded that the bridge does behave well as a system and that the transverse tie rods and shear keys were able to transfer load to adjacent beams. To validate the results of the destructive testing on the severely damaged west span, a comprehensive finite element model was created. The strain and deflection results from

4 4 the finite element analysis were compared with the results recorded during the testing of the west span. The model of the damaged bridge span adequately represented the results of the west span testing. Approved: Eric P. Steinberg Associate Professor of Civil Engineering

5 5 ACKNOWLEDGMENTS I would like to thank Dr. Eric Steinberg for his invaluable supervision and support throughout my time at Ohio University. I would also like to thank Dr. Shad Sargand, Issam Khoury, and my fellow graduate students and staff members at Ohio University; if not for their efforts this research project would have been possible. Dr. Richard Miller and Tyler Stillings at the University of Cincinnati also deserve acknowledgement for their efforts on this project. I would also like to thank Steve Luebbe and the staff at the Fayette County Engineer s office, especially Larry Dean. Without their help on this project it would not have been possible to complete. Finally, I would like to thank my family and friends who have help me through my graduate studies for without their help and support none of this would have been possible.

6 6 TABLE OF CONTENTS Page Abstract...3 Acknowledgments...5 List of Tables...9 List of Figures...1 Chapter 1: Objectives...16 Chapter 2: Background...17 Chapter 3: Bridge Testing FAY Instrumentation Instrumentation Locations Strain Gages String Potentiometers Loading Load Frame Loading Locations Hydraulic Cylinders Loading Methods Damaged West Span...45 Chapter 4: Finite Element Modeling Parts...47

7 7 4.2 Materials Damage Interactions Loads Boundary Conditions Transverse Tie Rods...6 Chapter 5: Bridge Testing Analysis Center Span Single Cylinder Loading Strain Readings Deflection Readings Center Span Simultaneous Loadings Strain Readings Deflection Readings West Span Single Cylinder Loading Strain Readings Deflection Readings West Span Simultaneous Loading Strain Readings Deflection Readings Comparison of the Center Span to the West Span Chapter 6: Finite Element Results of the West Span Strain Comparison...127

8 8 6.2 Deflection Comparison...13 Chapter 7: Conclusions Chapter 8: Recommendations References...139

9 9 LIST OF TABLES Page Table 3.1: Beams Loaded by Cylinders...42 Table 4.1: FEM Material Properties...5 Table 4.2: Material properties of the damaged sections...55 Table 4.3: Varied interaction properties, μ and K c...57 Table 5.1: Cylinder and Total Applied Load to Center Span...8 Table 5.2: Cylinder and Total Applied Load to West Span...19

10 1 LIST OF FIGURES Page Figure 2.1: Spalling on LIC (Gulistani, 21)...18 Figure 2.2: Canadian bridge elevation and cross-section views (Scanlon & Mikhailovsky, 1987)...2 Figure 2.3: Korean bridge cross-section (Oh, Kim, & Lew, 22)...22 Figure 2.4: Naping bridge elevation and cross-section views (Zhang, et. al., 211)...23 Figure 2.5: RC slab bridge plan and elevation (Miller, et. al., 1994)...24 Figure 3.1: FAY Figure 3.2: Bridge cross-section...28 Figure 3.3: Abutment anchor details as specified in the bridge drawings...29 Figure 3.4: Pier anchor details as specified in the bridge drawings...29 Figure 3.5: Center span instrumentation locations...32 Figure 3.6: West span instrumentation locations...33 Figure 3.7: KM-1AT strain transducer and WFLM LT strain gage...34 Figure 3.8: Installed strain gage and strain transducer...35 Figure 3.9: Assembled string potentiometer frame...36 Figure 3.1: Load frame assembly...38 Figure 3.11: Assembled frame and DYWIDAG THREADBAR Anchor installation...39 Figure 3.12: Hydraulic cylinder installed onto the load frame...4 Figure 3.13: Center span load locations...41 Figure 3.14: West span load locations...43 Figure 3.15: Location of damage on the west span (plan view)...46

11 Figure 3.16: Location of damage on the west span (cross-section view)...46 Figure 4.1: Beam cross-section...48 Figure 4.2: Solid section cross-section...48 Figure 4.3: Reinforcement cross-section...48 Figure 4.4: Shear key cross-section...48 Figure 4.5: Mesh resolution of a beam...49 Figure 4.6: Compressive stress-strain curve...52 Figure 4.7: Tensile stress-strain curve...53 Figure 4.8: Assembled cross-section...58 Figure 4.9: User defined node sets for the load locations...59 Figure 5.1: Raw and filtered data for strain gage 5EB...62 Figure 5.2: Strain readings on Line EB for Cylinder 1-2 loading on the center span...66 Figure 5.3: Strain readings Line EB for Cylinder 4-5 loading on the center span...67 Figure 5.4: Strain readings on Line EB for Cylinder 7-8 loading on the center span...68 Figure 5.5: Strain readings Line ET for Cylinder 1-2 loading on the center span...69 Figure 5.6: Strain readings on Line ET for Cylinder 4-5 loading on the center span...7 Figure 5.7: Strains on instrument line ET for Cylinder 7-8 loading on the center span...7 Figure 5.8: Strains on Line DT for Cylinder 1-2 loading on the center span...71 Figure 5.9: Strains Line DT for Cylinder 4-5 loading on the center span...71 Figure 5.1: Strains on Line DT for Cylinder 7-8 loading on the center span...72 Figure 5.11: Deflection results on Line ET for Cylinder 1-2 loading on the center span

12 Figure 5.12: Deflection results on Line ET for Cylinder 4-5 loading on the center span...75 Figure 5.13: Deflection results on Line ET for Cylinder 7-8 loading on the center span...76 Figure 5.14: Deflection results on Line DT for Cylinder 1-2 loading on the center span...77 Figure 5.15: Deflection results on Line DT for Cylinder 4-5 loading on the center span...77 Figure 5.16: Deflection results on Line DT for Cylinder 7-8 loading on the center span...78 Figure 5.17: Strain results on Line EB for the simultaneous loading on the center span...82 Figure 5.18: Strain results on Line ET for the simultaneous loading on the center span...84 Figure 5.19: Strain results on Line DT for the simultaneous loading on the center span...85 Figure 5.2: Deflection results on Line ET for simultaneous loading on the center span...86 Figure 5.21: Deflection results on Line DT for simultaneous loading on the center span...87 Figure 5.22: Strain readings on Line AB for Cylinder 1-2 loading on the west span...89 Figure 5.23: Strain readings on Line AB for Cylinder 4-5 loading on the west span...9 Figure 5.24: Strain readings on Line AB for Cylinder 7-8 loading on the west span...91 Figure 5.25: Strain readings on Line AT for Cylinder 1-2 loading on the west span...93 Figure 5.26: Strain readings on Line AT for Cylinder 4-5 loading on the west span...94 Figure 5.27: Strain readings on Line AT for Cylinder 7-8 loading on the west span...95 Figure 5.28: Strain readings on Line BB for Cylinder 1-2 loading on the west span

13 Figure 5.29: Strain readings on Line BB for Cylinder 4-5 loading on the west span...97 Figure 5.3: Strain readings on Line BB for Cylinder 7-8 loading on the west span...98 Figure 5.31: Strain readings on Line BT for Cylinder 1-2 loading on the west span...99 Figure 5.32: Strain readings on Line BT for Cylinder 4-5 loading on the west span...1 Figure 5.33: Strain readings on Line BT for Cylinder 7-8 loading on the west span...11 Figure 5.34: Deflection readings on Line AT for Cylinder 1-2 loading on the west span...13 Figure 5.35: Deflection readings on Line AT for Cylinder 4-5 loading on the west span...14 Figure 5.36: Deflection readings on Line AT for Cylinder 7-8 loading on the west span...15 Figure 5.37: Deflection readings on Line BT for Cylinder 1-2 loading on the west span...17 Figure 5.38: Deflection readings on Line BT for Cylinder 4-5 loading on the west span...17 Figure 5.39: Deflection readings on Line BT for Cylinder 7-8 loading on the west span...18 Figure 5.4: Strain results on Line AB for the simultaneous loading on the west span...11 Figure 5.41: Strain results on Line AT for the simultaneous loading on the west span Figure 5.42: Strain results on Line BB for the simultaneous loading on the west span Figure 5.43: Strain results on Line BT for the simultaneous loading on the west span Figure 5.44: Deflection results on Line AT for the simultaneous loading on the west span

14 Figure 5.45: Deflection results on Line BT for the simultaneous loading on the west span Figure 5.46: Strain comparison of Lines EB and AB while Cylinder 2 was applying load Figure 5.47: Strain comparison of Lines EB and AB while Cylinder 5 was applying load Figure 5.48: Strain comparison of Lines EB and AB while Cylinder 8 was applying load Figure 5.49: Deflection comparison of Lines ET and AT while Cylinder 2 was applying load Figure 5.5: Deflection comparison of Lines ET and AT while Cylinder 5 was applying load Figure 5.51: Deflection comparison of Lines EB and AB while Cylinder 8 was applying load Figure 5.52: Strain comparison of Lines ET and AT while all cylinders were applying load Figure 5.53: Deflection comparison of Lines EB and AB while all cylinders were applying load Figure 5.54: Load vs. Deflection plots for the Center and West Spans Figure 6.1: Strain comparison of the finite element model and experimental results for the west span while loaded by Cylinder 2 (AB and BB Lines) Figure 6.2: Strain comparison of the finite element model and experimental results for the west span while loaded by Cylinder 5 (AB and BB Lines) Figure 6.3: Strain comparison of the finite element model and experimental results for the west span while loaded by Cylinder 8 (AB and BB Lines)...13 Figure 6.4: Deflection comparison of the finite element model and experimental results for the west span while loaded by Cylinder 2 (A and B Lines) Figure 6.5: Deflection comparison of the finite element model and experimental results for the west span while loaded by Cylinder 5 (A and B Lines)

15 Figure 6.6: Deflection comparison of the finite element model and experimental results for the west span while loaded by Cylinder 8 (A and B Lines) Figure 7.1: Transverse tie rod exposed during west span collapse Figure 7.2: Shear key exposed during west span collapse

16 16 CHAPTER 1: OBJECTIVES The objective of this study was to determine how the precast prestressed concrete adjacent box beam bridges behave as a system with varying degrees of damage. To achieve this objective two bridge spans of equal length were subjected to destructive testing. The destructive testing consisted of loading the bridge and observing strains and deflections on each beam. On the west span, damage was generated on several of the interior beams. The damage consisted of making an approximately 2 deep cut into the bottom of three interior beams. These cuts passed through the bottom row of prestressed strands in each beam (14 strands per beam). The center span was left undamaged to act as a control. The results from the testing of each span were analyzed to determine how the prestressed adjacent box beam bridge span performed as a system and how the damaged beams affected the behavior of this system. In order to validate and better understand the results from the destructive testing of the west span, finite element modeling was utilized to construct a model that accurately emulates the behavior of the prestressed box beams as a system to validate experimental results from the damaged span.

17 17 CHAPTER 2: BACKGROUND The use of prestressed precast concrete adjacent box beam bridges became a prevalent solution for many state departments of transportation (DOTs) when spanning lengths of 2 up to 8. However, box beam bridges have been used to span lengths less than 2 and greater than 8. Currently, two-thirds of the state DOTs use some style of box beam bridge because of the economic advantages associated with these bridges. (Russell, 211). However, the most prevailing drawback with this style of bridge is the efficiency of the grouted shear key. Shear keys along with a transverse tie rod system are designed to transfer live load between adjacent beams. During the life of the structure, it is common for the shear keys to crack under live loads. This leads to cracking of the wearing surface and salt laden water is able to penetrate between box beams. Over time the chloride in the salt causes corrosion of the transverse tie rods holding the beams together. Corrosion of the prestressed strands in the beams can also occur, leading to cracking and spalling of the concrete and decreased flexural strength (see Figure 2.1). Several studies have been conducted across the United States and around the world on individual prestressed box beams taken from decommissioned bridges. These studies were designed to investigate the dimensions, material properties, flexural behavior, and ultimate capacity of the individual beams (Labia, et. al., 1997,Naito, et. al., 26, Camino, 21, and Gulistani, 21). From these tests, the behavior of individual beams with differing degrees of degradation can be estimated. However, the behavior of the prestressed box beams as a system can only be speculated because the prestressed concrete adjacent box beam system has rarely been tested.

18 18 Figure Spalling on LIC (Gulistani, 21) With an adequate knowledge of how individual beams behave, more extensive testing of the prestressed concrete box beams as a system was required to sufficiently understand the true behavior of these bridges. Non-destructive studies have been completed where adjacent prestressed concrete box beam bridges were loaded with trucks. However, these tests were limited by the magnitude of load that could be applied to the bridges because they were still in service. In 1993, a study was completed using truck loading on four prestressed box beam bridges in Ohio (Huckelbridge, et. al., 1993). The bridges were instrumented and the strains and deflections for each beam were monitored under several truck loadings. The relative strains and deflections between adjacent beams were monitored to determine how the loads from the trucks were distributed from beam to beam.

19 19 The behavior of prestressed concrete adjacent box beam bridges became a concern when a fascia beam of the Lakeview Drive Bridge collapsed onto Interstate 7 in Washington County, Pennsylvania on December 27 th of 25. Beams from this bridge were extensively studied by the University of Pittsburg and Lehigh University (Harries, et. al., 26, and Naito, et. al., 26). The Ohio Department of Transportation also acted on the concerns surrounding prestressed concrete box beam bridges because of the number of these bridges used in the state of Ohio. According to the Ohio Bridge Inventory (OBI) in 26, Ohio had 5,668 adjacent prestressed concrete box beam bridges in service. This makes up 17.1% of the bridges in the state of Ohio (ODOT, 26). In the United States, precast prestressed concrete box beam bridges make up about 16.7% of the nation s bridge inventory (Russell, 211). The Ohio Department of Transportation contracted with Ohio University and the University of Cincinnati to perform a forensic investigation and destructive testing on prestressed concrete box beams taken from a decommissioned bridge in Licking County, Ohio (Steinberg & Miller, 211). The dimensions, material properties, condition, flexural behavior, and ultimate capacity of the individual beams removed from the bridge were investigated. From these tests, it was concluded that further testing of prestressed box beam bridges as a system should be performed to better understand the behavior of these bridges. There have only been a few full-scale destructive tests conducted on bridges as a system. These tests are uncommon because the cost and time associated with decommissioning and testing a bridge to failure. There is no evidence suggesting that a

20 2 full-scale destructive test of an adjacent prestressed concrete box beam bridge has ever been conducted. In September of 1984, a full-scale destructive test was completed on a 34 year old continuous three span reinforced concrete bridge (Scanlon & Mikhailovsky, 1987). The bridge consisted of five tee beams of varying depth with a 1 slab deck. It should be noted that the design specifications showed a 7 slab deck. However during inspection in the field, it was determined that the slab was actually 1 thick. The approach spans of the bridge where 4 long while the center span was 6 long (see Figure 2.2). Figure 2.2 Canadian bridge elevation and cross-section views (Scanlon & Mikhailovsky, 1987) The indeterminacy of the bridge was eliminated by removing the load on the abutment bearing pads using hydraulic jacks. The load on the hydraulic jacks was known

21 21 which made the indeterminate system determinate. The bridge was then loaded in twophases. The first phase consisted of placing precast concrete sections on the center span until a total load of kips was achieved. The second phase involved applying additional vertical load to the reaction at the end of the beams to increase the total load to kips. Deflections were measured on the bridge using a level with an accuracy of.4. Theoretical moment capacities were calculated for yield and ultimate tensile stresses for the bridge cross-section. The yield moment capacity was well below the measured maximum moment. However, the ultimate moment capacity was nearly equal to the measured moment. From the testing results, it was concluded that the bridge behavior under extreme loading conditions was highly ductile. It was also concluded, the ultimate capacity of the tensile reinforcement was reached before crushing of the compression flanges occurred. Full-scale destructive testing was also completed on a single end span of a 3 year old, 12 span, prestressed concrete I-girder bridge on the Seoul-Pusan highway in Korea (Oh, Kim, & Lew, 22). Each span was simply supported and approximately 98 5 long. Four prestressed I-girders were used for each span. The 7 concrete slab was cast in place with a median in the center to separate the lanes (see Figure 2.3).

22 22 Figure Korean bridge cross-section (Oh, Kim, & Lew, 22) Strain gages were installed on the concrete of the girders and slab. The concrete surrounding the reinforcement on the girders and slab was removed and strain gages were also installed on the reinforcement. Concrete with similar strength as determined from the bridge was then used to patch the areas where the concrete was removed to install the strain gages. Also, strain gage rosettes were placed on intermediate diaphragms of the bridge. Linear variable differential transformers (LVDTs) were also placed beneath each girder to measure deflection. The bridge was loaded in four locations. The locations were configured to simulate a standard Korean truck loading. Once the bridge was loaded and the beams started cracking, the load was removed and crack gages were installed over the cracks to measure the width of the cracks as the bridge was reloaded. The failure of the bridge began with the crushing of the curb, followed by crushing of the deck. This particular bridge had a design service live load of approximately 71 kips and the I-girders themselves did not fail and an applied load of 969 kips was reached. It was concluded from these results, that the margin of safety specified when designing bridges should be reconsidered to acquire a more realistic and economical design.

23 23 Another full-scale destructive test of a reinforced concrete bridge was conducted on the Naping Bridge (Zhang, et. al., 211). This bridge was a 43 year old, three span, simply supported, two lane bridge, located on Province Road 29 in the Hunan Province of China. The bridge spanned 131 3, with three equal spans of Each span consisted of six reinforced concrete inverted channel beams with six diaphragms and transverse connections per beam see (Figure 2.4) CL Figure Naping bridge elevation and cross-section views (Zhang, et. al., 211) The bridge was instrumented with strain gages and vibrating wire extensometers to measure strains in the concrete and on the steel reinforcement. Also, deflections were measured using electronic displacement meters, dial indicators, and digital levels. The bridge was loaded using a two-axle truck, a three-axle truck, and 12 hydraulic jacks. The hydraulic jacks were positioned to apply load at the same location as the two and three axle trucks. The load applied by the hydraulic jacks was 1.33 to 3.8 times the load exerted by the trucks. It was concluded that the bridge capacity was higher than expected given the degradation of the beams. The degradation included concrete cracking, spalling, and corrosion of the steel reinforcement. A load 3.8 times the three-axle truck

24 24 load was needed to obtain the maximum deflection criteria in the particular design code used in China. A full-scale destructive test was also conducted on a 38 year old, three span, decommissioned reinforced concrete (RC) slab bridge (Miller, et. al., 1994). The exterior spans of the bridge were 32 long while the interior span was 4 long (see Figure 2.5). Figure 2.5 RC slab bridge plan and elevation (Miller, et. al., 1994) The bridge was instrumented to measure displacement, rotation, distortion, and strain in the reinforcement. The bridge was loaded using hydraulic cylinders placed in locations to simulate an HS2-44 truck loading. The bridge was loaded in half-truck increments (16 kips). The bridge was loaded in cycles and the final loading cycle on the

25 25 bridge reached a load of 72 kips at which point the bridge failed suddenly. The load at failure was the equivalent of 22 HS2-44 trucks. From these results, it was concluded that the bridge did not warrant decommissioning. Also, linear and non-linear finite element (FE) analyses were performed for the bridge. The purpose of the FE analysis was to compare the two FE analysis methods to the commonly used effective-strip method. It was concluded that the FE analysis methods were considerably more accurate when estimating the capacity of the bridge (Miller, et. al., 1994). The use of non-linear finite element modeling (FEM) is frequently used in modeling the behavior of reinforced concrete. The advantages of non-linear FEM are that the linear and non-linear behavior concrete can be accurately modeled. Concrete is generally made up of cement and aggregate, which both display linear stress-strain behavior. However, concrete as a composite of the two does not. Concrete will behave linearly at low stress levels (<3-4% of ultimate). The non-linear behavior at higher stress levels is due to micro cracking at the interface of the cement and aggregate (MacGregor & Wright, 25). With non-linear FEM, the effects of micro and macro cracking in the concrete are included in the analysis. Non-linear FEM can be a useful tool to model reinforced concrete but has been limited because of large computational requirements. With the advancement of computer technologies, the needed computational resources to use FEM on large reinforced concrete structures with minimal simplification of geometric and material properties are now available without the use of a super computer.

26 26 In non-linear FEM there are many variables that influence the accuracy of a reinforced concrete model. In order to correctly evaluate the failure mechanism(s) of a particular reinforced concrete structure, element type, mesh size, load step, convergence criteria, presence or absence of bond-slip, and material properties should be appropriately chosen (Balakrishnan, et. al., 1988). When modeling the concrete material, several characteristics of the concrete should be considered. This includes cracking criteria, tension stiffening, tension softening, compression hardening, compressive ductility, compression softening, multi-directional cracking, relation of shear stiffness to cracking, and multi-axial stress conditions (Balakrishnan, et. al., 1988). Smeared cracking is a method commonly used for modeling post-cracking behavior in concrete. Smeared cracking simplifies the compressive and tensile behavior of the concrete into piece-wise linear stress-strain curves. These curves account for the compression hardening and softening as well as loss of tensile strength upon cracking. The actual cracking in the concrete is not tracked in a smeared cracking model. Once the criterion for cracking has been met for a particular element, the appropriate material properties are applied to the individual element. The effect of the crack is considered smeared throughout the element. The altered material property of the element will also change the stresses in the surrounding elements which may or may not cause additional elements to crack.

27 27 CHAPTER 3: BRIDGE TESTING Bridge in Fayette County, Ohio was selected for full-scale destructive testing because the bridge failed a visual inspection and was deemed for replacement. However, there was minimal degradation of the interior beams of the bridge, and the bridge had three spans of equal length. This allowed for controlled damage to be applied to two spans and one span left in its original condition so the behavior of each span under varying levels of controlled damage could be compared. In order to perform the full-scale destructive testing on the 43 year old, three span prestressed concrete adjacent box beam bridge, an applicable experimental procedure was developed. This procedure consisted of installing strain gages and string potentiometers on each beam at two locations along the length of the beams. Load was applied to each bridge span using three large steel frames with a hydraulic cylinder in the center. The load applied on the bridge was measured using pressure transducers installed on the hydraulic cylinders. Using the strain, deflection, and applied load readings taken during testing, the behavior of each span as a system of adjacent box beams was observed FAY FAY (see Figure 3.1) was a 43 year old, three span, prestressed concrete adjacent box beam bridge located on Washington-Waterloo Rd. northeast of Washington Court House, Ohio. All of the spans were specified in the plans as 47 1 long with a 15 left forward skew. Each span consisted of nine prestressed box beams held together with a combination of transverse tie rods and shear keys (see Figure 3.2). The beams

28 were joined to the abutments and piers using dowel rods that were grouted in during construction (see Figures 3.3 and 3.4). 28 Figure FAY Figure 3.2 FAY cross-section

29 29 Figure Abutment anchor details as specified in the bridge drawings Figure Pier anchor details as specified in the bridge drawings

30 3 The transverse tie rods were one inch in diameter, approximately six feet long and were threaded on both sides. These tie rods were installed at locations of and 3.74 from the west end of the beams, and because of the 15 skew, each tie rod only connected two beams together. During construction, the transverse tie rods were used to pull the beams firmly together and during the life of the structure the transverse tie rods assist in the transfer of live load from beam to beam. The cross-section of the beam was solid where the transverse tie rods were located. However, the length of the solid diaphragm was not specified in the bridge drawings. A square indentation was also precast in the beam which accommodated a steel bearing plate for the transverse tie rods. When the shear keys of the bridge were grouted, the indentation for the bearing plate was also filled with grout. The grout in the indentation minimizes the void between beams and holds the tie rods in place which transferred load more efficiently. As specified in the bridge drawings, dowel rods one inch in diameter, and 15 long were placed into two holes in the beam and abutment/pier. The two inch dowel holes in the beams were precast and the inch and a quarter diameter holes in the pier and abutment were drilled eight inches deep once the beams were set and the transverse tie rods had been tensioned. The dowel bars were then set into the holes and grouted using Class C concrete. Two dowel bars were placed at both ends of each beam for a total of four dowel bars per beam.

31 Instrumentation Each beam was numbered for each span from south to north and typically instrumented with four strain gages and two string potentiometers. All of the data from the instrumentation was read and recorded using an Optim MegaDAC data acquisition system, and a sample rate of 1Hz was used for all instrumentation. In some cases, the degradation on the fascia beams prevented the installation of a strain gage and/or strain potentiometer. The strain gages were mounted on the top and bottom of each beam to record the tensile and compressive strains. The string potentiometers were installed on the top of the beams and the deflection of each beam was monitored Instrumentation Locations The strain gages and string potentiometers were installed at two locations along the length of each beam, the first location was 22 (A and E instrument lines) from the end of the beam and the second was located 36.5 (B and D instrument lines) from the end of the beam. These locations were carried over from truck load testing of the bridge where the continuity of the bridge was examined. The locations were determined from a spreadsheet developed to calculate shear and moment for a three span continuous bridge, the location of the maximum positive moment was approximately 22 from the end of the beam and the corresponding inflection point was located at approximately 36.5 from the same end. The 22 location also provided space to apply load to the midspan in order to generate large moments. Strain gages were typically mounted on the top and bottom of each beam at corresponding locations. Figures 3.5 and 3.6 show the numbering of the

32 32 beams and location of the strain gages and string potentiometers on the top of the beams for the center and west span, respectively. It should be noted that strain gages were also installed at the same locations on the bottom of the beams. On the west span strain gages also installed on the bottom flanges of Beams 2, 3, and 4 at the edge of the beam. These gages were installed to monitor the strain relation near the longitudinal joints. Figure Center span instrumentation locations

33 33 Figure West span instrumentation locations Strain Gages Two types of strain gages were utilized on each span. The compressive strains on Beams 2, 3, 5, 6, 7, and 8 were measured with KM-1AT strain transducers (see Figure 3.7) on the A and E instrument lines of the center and west spans. The KM-1AT consists of four strain gages that are 35Ω gages and were wired in a full bridge configuration. All remaining applicable locations were instrumented with WFLM LT strain gages (see Figure 3.7). These gages were 12Ω electrical resistance strain gages with 6.56 of lead wire and a weather proof coating. The electrical resistance strain gages were wired in a quarter bridge configuration.

34 34 Figure KM-1AT strain transducer and WFLM LT strain gage In order to mount the instrumentation to the spans, the asphalt wearing surface on the bridge was removed at the instrumentation lines to expose the top flange of the box beams. Grinding wheels were then used to smooth the surface of the concrete beams at the strain gage locations. The surface was then wiped with a wet cloth to remove any large particulates. If any voids were present, a layer of TML strain gage adhesive type PS was first placed at the gage installation site to create a smooth surface. Once all gage locations were properly prepared, a layer of the adhesive was applied to the concrete. Immediately after the adhesive was applied to the concrete, the strain gages were placed on the adhesive and aligned longitudinally along the center of each beam (see Figure 3.8). After the adhesive had sufficiently cured, duct tape was placed over the strain gages and

35 35 lead wires for protection. The KM-1AT strain transducers were attached to the top flange of the beams using a metal bracket that was secured to the beams with concrete anchor screws (see Figure 3.8). Figure Installed strain gage and strain transducer String Potentiometers The string potentiometers used were UniMeasure model PA-2-DS-L5M. The range of these string potentiometers was 2 and the excitation voltage used was 1V. The string potentiometers were installed along the same instrumentation lines as the strain gages. The string potentiometers were mounted to the top of each beam near the strain gages. This allowed the deflection of each beam to be monitored for the absolute deflection of each beam as well as the relative deflection of adjacent beams to be observed.

36 36 A steel frame was constructed to hold the string potentiometers above the beams, this frame allowed for the absolute deflection of individual beams to be measured without being influenced by the movement of the bridge during loading. Mounting on the top side of the span also protected the string potentiometers from being damaged if concrete spalled and fell from the beams during testing. The frame consisted of two W-shaped beams that spanned the length of each span outside of the fascia beams and were anchored to the abutment/pier. Mounted on top of the two W-shapes were two tube sections that spanned transversely across the bridge at the instrument line locations. The string potentiometers were mounted upside down from the tube sections. The end of the string potentiometers were then connected to eyelets that were embedded in the middle of the top flange of each beam (see Figure 3.9). Figure Assembled string potentiometer frame

37 Loading Each span of the bridge were loaded using three independent load frames. The frames spanned the length of the span and were anchored to the abutments/pier. A hydraulic cylinder installed in the center of the load frame applied load approximately at the center of the span. Each span was loaded by each frame individually to monitor how load was transferred transversely across the bridge. Each span was also loaded by all three frames simultaneously until the ultimate capacity of the span was reached Load Frame The three load frames were constructed using steel W-shapes. The load frames consisted of two 5 long W36x26s which were supported at each end by two 4 long W33x118s. A 25 ton capacity crane was used to place the W36x26s on top of the W33x118s (see Figure 3.1). Bolts were placed through all of the members and tightened to secure the six piece assembly (see Figure 3.1).

38 38 Figure Load frame assembly To anchor the frames, 4 diameter holes were drilled through the piers and abutments. Then 1¾ diameter DYWIDAG THREADBAR Anchors were lowered in the holes from the top of the W33x118s of the load frame to the bottom of the piers/abutments. A 6 x6 x2 plate was placed at the top and bottom of the anchor bars. Nuts were then screwed tight on the anchor bars to secure the frames to the bridge supports (see Figure 3.11).

39 39 Figure 3.11 Assembled frame and DYWIDAG THREADBAR Anchor installation Once the frames were anchored to the bridge, hydraulic cylinders were installed at the center of each load frame between the two W36x26s (see Figure 3.12). The cylinders were held to the load frame using two 2 diameter bolts. To resist any lateral torsional buckling or separation of the two W36x26s during loading, steel angles were welded to the W36x26s in the field after the frames were assembled. Two angles were welded to the top side of the bottom flange at third points of the W36x26s and another angle iron was welded to the top side of the top flange near the center of the W36x26s.

40 4 Figure Hydraulic cylinder installed onto the load frame Loading Locations With the load frames completely assembled, two 4 long W6x26s were placed beneath each cylinder to act as spreader beams. The spreader beams distributed the load across two beams, with a 4 x1 distribution footprint. This eliminated the chance of punching through the top flange of the beams during load testing. The cylinders were labeled using the beam number in which most of the footprint from the spreader beams was distributed. On the center span, the load frames were positioned where load was applied from the west pier. The first cylinder (Cylinder 2) applied load to beams 1, 2, and 3. The

41 41 second cylinder (Cylinder 5) applied load to beams 4, 5, and 6. The third cylinder (Cylinder 8) applied load to beams 7, 8, and 9. The spreader beams were positioned so that the footprint of the load was applied at the same angle as the skew of the bridge. Figure 3.13 shows a schematic of the load locations for the center span. Table 3.1 gives the beams that were loaded by each cylinder for the center and west spans. The percentages presented in Table 3.1 are based on the contact area of the spreader beams. Figure Center span load locations On the west span, the load frames were positioned where load was applied 24 4 from the west end of the beams. The first cylinder (Cylinder 2) applied load on Beams 1 and 2. The second cylinder (Cylinder 5) applied load of beams 4, 5, and 6. The third cylinder (Cylinder 8) applied load to beams 7 and 8. The percentage of load applied to each beam based on the contact area is also provided in Table 3.1. Again, the spreader

42 42 beams were positioned so that the footprint of the load was applied at the same angle as the skew of the bridge. Figure 3.14 provides a schematic of the load locations for the west span. The load locations of the west span slightly differ from the load locations on the center span because the coring locations for the anchors were altered to avoid hitting the piles beneath the west abutment. Table Beams loaded by each cylinder on the center and west spans and percentage of contact area of the spreader beams on each beam Center Span West Span Cylinder 2 Cylinder 5 Cylinder 8 Beam # Contact % 16% 72% 12% 28% 72% - Beam # Contact % 8% 77% 15% 2% 76% 4% Beam # Contact % 8% 79% 13% 21% 79% -

43 43 Figure West span load locations Hydraulic Cylinders The hydraulic cylinders were controlled using a displacement controlled loading system for safety reasons. This system consisted of a programmable logic controller (PLC) which was attached to three servo valves and three string potentiometers. String potentiometers were installed on each of the cylinders to measure the stroke of the cylinder as it applied load. The desired magnitude of displacement on the cylinder was input into the PLC, which then opened the servo valves. The servo valves regulated the pressure of the hydraulic fluid in the hydraulic hoses. The pressure in the hoses was increased until the input magnitude of displacement was recorded by the string potentiometer on the hydraulic cylinder. The PLC then stopped the servo valve from increasing the pressure of the fluid in the hose. The pressure in the hydraulic hose was

44 44 generated by an electric hydraulic pump that was powered by a diesel powered generator with 22V three-phase capabilities. The load being applied to the span by each hydraulic cylinder was measured using pressure transducers. The pressure transducers were connected to the hydraulic hoses at inlet and outlet of each cylinder. This measured the inlet and outlet pressure of the hydraulic fluid in the cylinder and from these pressures the applied load was calculated Loading Methods The center and west spans of the bridge were loaded using two loading methods. The first method was to load each cylinder individually and investigate how the load was transferred transversely across the bridge at each loading location by measuring strains and deflections. For this method six loading conditions were used. The first three loading conditions consisted of loading Cylinder 8 to approximately 5 kips and removing the load. This procedure was repeated with Cylinder 5 and Cylinder 2. The remaining loading conditions were similar to the first three, but the load applied by each cylinder was increased to a total of approximately 1 kips. The load increments varied since the cylinder displacement was input into the PLC and not the load step. For the second loading method, all three cylinders applied load simultaneously. This loading method was used to determine the behavior of the span at extreme load conditions and the ultimate capacity of the span. Each span was loaded using all three cylinders until the span was unable to resist any additional load. This load was the ultimate capacity of the span. For this method Cylinder 8 was loaded to approximately

45 45 5 kips, then Cylinder 5 was loaded to approximately 5 kips, and similarly Cylinder 2 was loaded to approximately 5 kips, totaling a load of approximately 15 kips on the span. Once all cylinders were loaded to approximately 5 kips the same process was repeated until all cylinders were applying a load of approximately 1 kips, 3 kips total. It should be noted that it was difficult to load each cylinder equally because the loading was displacement controlled. With the displacement held constant on one cylinder and as load was applied using another cylinder, the load on the other cylinders would decrease because the entire span was being displaced Damaged West Span In order to study the effects of damaged beams on the behavior of the span as a system, damage was created on the west span. The damage was created using 4 diameter cutting wheels. Using the cutting wheels, an approximately 2 cut was made in the bottom flange of Beams 4, 5, and 6. The cut was across the entire width of these beams. This cut also cut the bottom row of prestressed reinforcement in each of the cut beams (14 strands). Beams 4, 5, and 6 were cut at two locations, 23 9 and 26 9 from the west abutment. The beams were cut in two locations to sufficiently remove the tensile capacity of the bottom row of strands. Figure 3.15 is a schematic of the damage locations on the plan view of the west span and Figure 3.16 shows the damage on the cross-section.

46 46 Figure Location of damage on the west span (plan view) Figure Location of damage on the west span (cross-section view)

47 47 CHAPTER 4: FINITE ELEMENT MODELING A finite element model was used to analyze the damaged west span of the bridge. A standard model was constructed in Abaqus/CAE 6.1. The prestressed concrete box beams were modeled using a smeared cracking method with the reinforcement modeled as embedded steel elements. Modeling the concrete using a smeared cracking method is the predominate approach used in three-dimensional modeling of concrete (Barzegar & Maddipudi, 1997). The model of the damaged bridge span consisted of nine beams with solid sections and longitudinal reinforcement, eight shear keys, springs to model the transverse tie rods and dowel rods, applied loads at the location of cylinders, and boundary conditions that represented the abutment and pier Parts The cross-sections of the precast concrete box beams, solid sections, prestressed reinforcement, conventional reinforcement, and shear keys of the west span of the bridge were drawn in the Abaqus/CAE to the specifications provided in the bridge design drawings. The solid sections of the precast beams were drawn separately to make meshing the two parts possible in a practical manner. Once the cross-sections were drawn, the parts were extruded 574 (47 1 ) in the longitudinal direction. The sketches created in Abaqus/CAE for the beam, solid section, shear key, and reinforcement parts are shown in Figures 4.1, 4.2, 4.3, 4.4 respectively. The scale in Figure 4.2 and 4.4 are larger to show the details of the solid section and shear key which appear inside the beam at specific locations and the upper corners of the cross-section (Figure 4.1).

48 48 Figure Beam cross-section Figure 4.2 Solid section cross-section Figure Reinforcement cross-section Figure 4.4 Shear key cross-section Each part was meshed independently, the cross-section of the beam was seeded to yield an approximate mesh resolution of three inches, and the beam was also seeded along its length every six inches. A three inch seed was required on the beam crosssection to ensure the mesh shape was within the set angle constraints. The beam was then meshed using a sweep mesh control, creating 7,81 elements for each beam. The cross-section of the shear key was partitioned and seeded with a 1.5 inch seed to meet the angle limits of the element shape. The shear key was similarly seeded with a six inch seed along the length of the part. The shear key was meshed using a sweep mesh control, and 2,496 elements were created for each shear key. The steel reinforcement cross-

49 49 section was also seeded so that the cross-section of each bar/strand would be a single element. To maintain consistency, the reinforcement was also seeded with a six inch seed along the length of the part. This allowed the nodes of the reinforcement elements to be accurately embedded into the concrete beam. Embedment is discussed in greater detail in the interaction section. The steel was also meshed using a sweep mesh control and 2976 elements were created for the reinforcement for a single beam. An illustration of the mesh resolution of a single box beam can be seen in Figure 4.5. Figure Mesh resolution of a beam 4.2. Materials The elastic concrete material properties were modeled by defining the Young s modulus and Poisson s ratio for the concrete. Several cores taken from the east span of the bridge were tested, and from these results a concrete strength of 1ksi, a Poisson s ratio of.2, and a unit weight of 147 pcf were used in modeling the material properties of the beams and shear keys (Setty, 211). The solid sections of each beam were assigned

50 5 the same material properties as the corresponding beam. It should be noted that a concrete compressive strength of 1 ksi was not used for all of the concrete parts. A complete list of the material properties for each part is provided in Table 4.1. The compressive strength of each concrete part was changed to improve the model behavior in comparison with test results. The plastic concrete material properties were defined using a concrete smeared cracking model. To define the concrete smeared cracking material properties, post-yield compressive and tensile stress-strain relations were defined, as were failure ratios for the concrete. Table FEM Material Properties Property Part f c (ksi) E (ksi) ν Ratio 1 Ratio 2 Ratio 3 Ratio 4 Beam Beam Beam Beam Beam Beam Beam Beam Beam Shear Key Shear Key Shear Key Shear Key Shear Key Shear Key Shear Key Shear Key

51 For the compressive stress-strain relationship, a list of compressive stresses and the associated plastic strains were input. To define the tensile stress-strain relation, a list of 51 the tensile stress after cracking to tensile stress at cracking ratios ( ), and the corresponding strain after cracking to strain at cracking ratios ( ) were input. Equations were developed that allowed all parameters of the post-yield compressive and tensile stress-strain relationships to be defined by setting a single concrete compressive strength. These equations were developed by combining equations and relationships discussed in Reinforced Concrete, Mechanics and Design (MacGregor & Wright, 25) as well as relationships provided in the Abaqus Analysis User s Manual (Dassault Systemes Simulia Corporation, 21). The equations and relationships are listed in Eqns. 1-7: Young s Modulus: (Eqn. 1) Where: Factored Compressive Strength: (Eqn. 2) Compressive Strain at Yield: (Eqn. 3) Tensile Strength: (Eqn. 4) Tensile Strain at Yield: (Eqn. 5) Compressive Stress at Failure: (Eqn. 6) Compressive Strain at Failure:

52 52 (MacGregor & Wright, 25) Tensile Strain at Failure: (Eqn. 7) (Dassault Systemes Simulia Corporation, 21) The compressive and tensile stress-strain diagrams in Figures 4.6 and 4.7 represent the limits of the concrete smeared cracking material properties. The relationships in the stress-strain diagrams were derived from relationships discussed in the Abaqus Analysis User s Manual (Dassault Systemes Simulia Corporation, 21). Compressive Stress-Strain Diagram σ c, ksi ε c, in/in Figure Compressive stress-strain curve

53 53 Tensile Stress-Strain Diagram σ t, ksi ε t, in/in Figure Tensile stress-strain curve Four failure ratios were defined for the smeared cracking concrete material method. For this model, the default values were used for ratios 1, 3, and 4. Ratio 2 was changed to allow for quicker convergence in the full analysis of the bridge model. The failure ratios are defined as follows in the Abaqus/CAE User s Manual: Ratio 1- Ratio of the ultimate biaxial compressive stress to the uniaxial compressive ultimate stress. The default value is Ratio 2 - Absolute value of the ratio of uniaxial tensile stress at failure to the uniaxial compressive stress at failure. The default value is.9. Ratio 3 - Ratio of the magnitude of a principal component of plastic strain at ultimate stress in biaxial compression to the plastic strain at ultimate stress in uniaxial compression. The default value is Ratio 4 - Ratio of the tensile principal stress value at cracking in plane stress, when the other nonzero principal stress component is at the ultimate compressive stress value, to

54 54 the tensile cracking stress under uniaxial tension. The default value is.33. (Dassault Systemes Simulia Corporation, 21) The prestressed and conventional reinforcement material properties were defined the using the same material properties. The reinforcement was modeled as an elastic material with a Young s modulus of 29, ksi, and a Poisson s ratio of Damage The damage was modeled on beams 4, 5, and 6 by taking a three inch long crosssection from the beams at the location of the damage and replacing the concrete smeared cracking material properties with an elastic material that had a relatively low Young s modulus and a high Poisson s ratio. The Young s modulus and Poisson s ratio differed for each damaged section. Table 4.2 presents the material properties used in the damaged sections. Sections labeled (A) are the material properties for the cross-section modeling the cut made 23 8 from the west abutment and sections labeled (B) are the properties for the cross-section modeling the cut made 27 from the west abutment. These values differ significantly in the damaged cross-sections to model the behavior observed in the results from the west span testing. Also the 14 prestressed strands of the bottom row in the damaged beams were cut so that these strands were not present in the 3 damaged crosssections. The material in the damaged sections models the formation of a plastic hinge when the load is applied to the bridge model. Manipulating these damaged sections allowed the strain discontinuity between the damaged and undamaged beams to be accurately modeled.

55 55 Table Material properties of the damaged sections Part Young s Modulus (ksi) Poisson s Ratio Beam 4 Damage (A) 6.3 Beam 4 Damage (B) 3.3 Beam 5 Damage (A) 4.3 Beam 5 Damage (B) Beam 6 Damage (A) 1.3 Beam 6 Damage (B) 14.3 UC* - Material properties were not changed and were the same as the beam 4.4. Interactions The interaction between the concrete beam and the reinforcement was modeled as an embedment constraint. Embedding the elements of the reinforcement in the concrete elements is a computational effective method to accurately model the effect of the reinforcement on the surrounding concrete elements (Barzegar & Maddipudi, 1997). The embedment constraint embeds a group of user defined non-host elements into a group of user defined host elements. The sets of steel reinforcement were defined as non-host elements and the individual beams were defined as the host elements. When a group of non-host elements is embedded in a group of host elements, the translational degrees of freedom of the non-host elements are taken away where the nodes of the non-host elements coincide with the nodes of the host elements. The translations at each degree of freedom of nodes of the host elements are then placed on the nodes of non-host elements. This assumes there is non-slip bonding between the concrete and reinforcement. Slip and non-slip bonding in embedded steel reinforcement was investigated by Barzegar and Maddipudi and it was concluded that taking into account bond-slip did not significantly

56 change global behavior (Barzegar & Maddipudi, 1997). This particular embedment type 56 is solid element embedded into solid element. This will result in a more accurate modeling of the concrete-reinforcement interaction as opposed to modeling the reinforcement as shell or membrane elements. However, using shell or membrane elements is more computational economical. The outer perimeter surfaces of the solid sections were tied to the inner perimeter surfaces using a surface to surface tie constraint. This constraint bonds the two surfaces together absolutely. This models a perfect bond between the two surfaces, and since the actual solid sections were precast monolithically with the beams this is an appropriate method to bond the two surfaces. The interaction between the concrete beams and the shear keys was modeled using a surface to surface contact. First the surfaces of the shear keys and beams that come into contact were defined as contact pairs. Both the tangential and normal behavior of the contact properties were defined. The friction formulation was defined in the tangential behavior. The type of friction formulation used was Penalty. With the Penalty friction formulation, the friction coefficient for the interaction varied to better model the behavior of the span. (MacGregor & Wright, 25), the shear stress limit was set at 1.5 ksi, and the maximum elastic slip was define as 1% of the characteristic surface dimension. The pressure-overclosure in the normal behavior was selected to be linear and the contact stiffness also varied to better model the behavior of the span. The contact stiffness restrains the nodes of the two contacting surfaces from penetration into one

57 another until the value defined as the contact stiffness is reached. The values used for the friction coefficient and contact stiffness for each interaction are listed in Table Table 4.3 -Varied interaction properties, μ and K c Interaction Friction Coefficient, μ Contact Stiffness, K c Beams 1&2 Shear Key Beams 2&3 Shear Key Beams 3&4 Shear Key Beams 4&5 Shear Key Beams 5&6 Shear Key Beams 6&7 Shear Key Beams 7&8 Shear Key Beams 8&9 Shear Key In Figure 4.8, the assembled interaction between the beams and reinforcement, the constraint tying the solid section to the beams, as well as the assembled interaction between the beams and shear keys can be observed. It can be seen in Figure 4.8 where the reinforcement has been embedded into the beams and the shear keys are in contact with the beams.

58 58 Embedded longitudinal reinforcement Beam/Shear key contact interaction Figure Assembled cross-section 4.5. Loads In the damaged bridge span model, surface nodes which lied on the top surface of the beams within the location of the cylinder loadings were defined in sets for each of the three cylinder locations. For the Cylinder 8 loading condition 49 nodes were defined as the Cylinder 8 set. Similarly for the Cylinder 5 and Cylinder 2 loading conditions, 56 nodes were defined in sets for each of the Cylinder 5 and Cylinder 2 node sets. The Cylinder 8 node set has fewer nodes than the other loading sets because nodes were only selected if they were within the footprint of the load applied to the west span. There were fewer nodes available for the Cylinder 8 node set. Defining node sets at the locations of the actual cylinder locations allows for accurate modeling of the behavior of the load applied in the destructive testing of the bridge span. Once the sets were defined, the desired magnitude of load to be applied to the model was divided by the number of nodes for that cylinder node set and concentrated point loads were applied at each node of the

59 node set in the negative vertical direction. Figure 4.9 provides a sketch showing the load applied at the node sets for all of the cylinders Cylinder Cylinder Cylinder Figure User defined node sets for the load locations 4.6. Boundary Conditions To model the abutment and pier of the damaged bridge span, a combination of support conditions and springs were used. For the abutment, a node set was defined 18 from the west end of the beam on the bottom surface of the beam. This node set contained 13 nodes per beam, and a complete translational restraint was defined for these nodes in the transverse direction. The complete translation restraint, restricts the node from any displacement in the defined direction of the restraint. The purpose of this restraint was to aid in mathematical convergence of the model and had minimal influence on the results of the model. The effects of the abutment on the translations of the span

60 6 longitudinally and vertically were accounted for using springs. Strict support conditions, such as complete translational restraints, were not used because this also caused mathematical convergence problems. These springs were placed 18 from the west end of the beam and tied the defined nodes to a theoretically fixed surface. Since the location of the dowel rods was relatively close to the edge of the abutment, these springs were also used to account for the effect of the dowel rods on the span. This was done to avoid causing an area of concentrated stresses at the end of the beams because of too many supports in such a concentrated area. These springs were defined to resist translation in the vertical and longitudinal directions. The stiffness of the springs was assigned individually for each beam to allow for differences in the influence of the dowel bars on each beam. The effects of the pier were modeled similar to how the abutment was modeled. However, the location of the node sets for the complete transverse translational restraint and springs was located 12 from the opposite end of the beam to Transverse Tie Rods To aid in the transfer of loads transversely across the bridge, transverse tie rods were installed on the bridge during construction. Transverse tie rods were installed to pull the beams together during construction and hold the beams together throughout the life of the bridge. The transverse tie rods were modeled in the damaged bridge span with springs. The adjacent nodes of adjacent beams at the location of the transverse tie rods were tied together using springs. This spring caused the force due to the translations in the

61 61 transverse, vertical, and longitudinal directions of one node to be transfer to the adjacent node on the adjacent beam. The reaction of the springs when the span was loaded resulted in a concentrated force on the nodes where the springs were applied. This reaction allowed for the development of a normal force required for the tangential behavior in the interaction between the shear keys and beams.

62 62 CHAPTER 5: BRIDGE TESTING ANALYSIS Once the testing was completed, all of the data was filtered using a frequency impulse response (FIR) 6Hz low-pass filtering program developed at Ohio University. The data was filtered to remove any external noise at or above 6Hz from the data. Figure 5.1 displays the raw and filter data for the strain gage located on the bottom of beam 5 on the E line for the center span. Figure Raw and filtered data for strain gage on the bottom of beam 5 on the E line for the center span

63 Center Span Single Cylinder Loading The single cylinder loading tests were performed to monitor the transfer of load between beams while loading the span with a single cylinder. Strains and deflections were monitored for each beam at multiple locations while an individual cylinder applied load to the bridge. Two magnitudes of loading were completed for each cylinder. The testing applied approximately 5 kips and then 1 kips to the span. For simplicity, the results from the two tests for each cylinder were combined. Relative strains were measured on top and bottom flanges of each applicable beam at two locations. Strains on the bridge prior to strain gage installation were not measured. The results for each test file were initialized at the beginning of each test. Prior to each test, a balance of the electrical resistance strain gages in a quarter bridge configuration was performed by the data acquisition system. An additional initialization was performed on all of the instrumentation to account for the initial readings of the strain transducers and string potentiometers. The time range of the test data where no load was applied to the span was observed. This time range was used to find the initial reading for each instrument. An average value was found for each instrument reading within this time range and this was considered the initial reading. The relative instrument readings at the remaining loads were found by subtracting the average initial value from the recorded instrument reading. The KM-1AT required that a calibration coefficient be applied to each strain reading from the strain transducers. The calibration coefficient for each instrument is given in the specifications provided by TML. The string potentiometer data was

64 64 converted from millivolts to inches using the sensitivity for each string potentiometer. The string potentiometer sensitivity is a conversion factor specified by the manufacture to convert the recorded millivolt readings into readings in inches. Once all of the data was initialized, the load versus time plot was used to determine time periods where the applied load remained constant (plateaus). The time ranges for each plateau was observed and recorded. These time ranges were then used to find the average reading for each instrument during the load plateau. This procedure was used for each test file for the single cylinder loading tests. corresponding magnitudes of load to be compared. This allowed for the results at The strain results on multiple instrument lines and deflection results on multiple instrument lines were compared Strain Results In several of the figures illustrating the strain profiles for the various loading procedures for the single cylinder load testing, the strain profiles were not consistent throughout the entire test. The difference in strain behavior was caused by the order in which the bridge was loaded. Initially, each individual cylinder applied load of approximately 5 kips to the span. The load applied by a cylinder was removed before the next cylinder applied a load of approximately 5 kips to the span. Once the single cylinder testing was completed for the 5 kips loadings for each cylinder, the process was then repeated to a load of approximately 1 kips. The testing conducted between the 5 and 1 kip tests for a single cylinder may have caused seating and/or shifting of the load

65 65 transfer aspects of the span. This caused a slight change in the distribution of the strain in the span between tests. Figure 5.2 shows the tensile strain data for the strain gages located on the bottom flange of each beam on instrument line E (Line EB). These strain values were observed when Cylinder 2 was applying load on the center span. The strain values displayed in Figure 5.2 are for each load plateau selected from the loading data for Cylinder 2. In the figure, the loaded beams were subjected to the largest strain. However, the remaining beams were also subjected to strain. This displays that load was transferred transversely across the span. Beam 8 displays negative strain values at the lower loads. A combination of initializing the strain gage readings and the noise filtering can account for the small negative results. There was a smaller strain reading for Beam 2 at the 138 kip load than the preceding strain profiles suggest. This may be from a separation of the shear key(s) which would cause Beams 1 and 3 to carry additional load. This may also be caused by transverse cracking occurred on the bottom flange of the beam on both sides of where the strain gage was mounted. A combination of cracking of the shear key and the bottom flange of the beam may also have occurred causing the decreased load transfer to Beam 2. The 59 kip strain results were taken while unloading the cylinder. The results from this loading closely match the strain results taken while 55 kips were applied to the bridge.

66 66 Strain, με Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam 1 21 kips 38 kips 49 kips 55 kips 138 kips 59 kips Position, ft Figure 5.2 Strain readings on Line EB for Cylinder 2 loading on the center span The results for the tensile strain readings taken on Line EB while Cylinder 5 was applying load to the center span are presented in Figure 5.3. The beams to which the load was applied experienced the greatest strain. The loaded beams experienced an average of 55% of the total strain on the span and the remaining beams experienced an average of 45% of the total strain. In Figure 5.3, the distribution of strain transversely across the beams shows that the system of beams transfers load throughout the width of the span. The increase in strain in Beams 1 and 9 can be explained by the condition of these beams. The exterior beams of this span had considerably more degradation than the interior beams.

67 67 Strain, με Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam 1 1 kips 24 kips 48 kips 66 kips 8 kips 9 kips 111 kips Position, ft Figure 5.3 Strain readings Line EB for Cylinder 5 loading on the center span Figure 5.4 displays the tensile strain results for Line EB while Cylinder 8 was applying load to the center span. Similar to the previous loadings, the beams where the load was applied experience the highest strain. The beams where load was not applied also experience strain. This is an indication that load was transferred to these beams through the shear keys and transverse tie rods. The results of these tests seem to mirror the results presented in Figure 5.2 when the other side of the bridge was loaded. Beam 8 has a spike in strain that is not shown by Beam 2 in Figure 5.2. The absence of a spike in strain of Figure 5.2 may be because the asphalt overlay which was not removed from Beams 1, 2, and 3.

68 68 There were not any gages mounted on the bottom flanges of the beams on instrument line D. Mounting gages on the bottom of the center span was difficult because this span was over a creek and a snooper truck was required to install the gages. Strain, με Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam 1 14 kips 28 kips 38 kips 42 kips 55 kips 8 kips 9 kips Position, ft Figure 5.4 Strain readings on Line EB for Cylinder 8 loading on the center span The compressive strain results for the strain gages located on the top flange of each beam on instrument line E (Line ET) are displayed in Figures 5.5, 5.6, and 5.7. There were not any strain gages installed on the top flanges of Beams 1, 2, and 3 because the asphalt overlay was left on these beams to study if the pavement provided any significant additional benefit to the system. Also, there was not a strain gage installed on Beam 9 of this instrument line because the concrete on the top flange was severely degraded. The lack of available strain gage installation sites for this instrument line makes the strain

69 69 distribution across the span at this instrument line difficult to determine. This was also the case in Figures 5.8, 5.9, and 5.1. In these figures, the compressive strain results for the strain gages installed on the top flanges of the beams on instrument line D (Line DT) are provided. Strain, με Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam Position, ft Figure 5.5 Strain readings Line ET for Cylinder 2 loading on the center span kips 38 kips 49 kips 55 kips 138 kips 59 kips 3

70 7 Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam 1 Strain, με Position, ft Figure 5.6 Strain readings on Line ET for Cylinder 5 loading on the center span kips 24 kips 48 kips 66 kips 8 kips 9 kips 111kips 3 Strain, με Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam 1 14 kips 28 kips 38 kips 42 kips 55 kips 8 kips 9 kips Position, ft Figure Strains on instrument line ET for Cylinder 8 loading on the center span

71 71 Strain, με Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam 1 21 kips 38 kips 49 kips 55 kips 138 kips 59 kips Position, ft Figure Strains on Line DT for Cylinder 2 loading on the center span 3 Strain, με Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam 1 1 kips 24 kips 48 kips 66 kips 8 kips 9 kips 111kips Position, ft Figure Strains Line DT for Cylinder 5 loading on the center span 3

72 72 Strain, με Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam Position, ft Figure Strains on Line DT for Cylinder 8 loading on the center span kips 28 kips 38 kips 42 kips 55 kips 8 kips Deflection Readings The load plateaus used for deflection results correspond to the load plateaus selected for the strain results from the same loading test. Displayed in Figure 5.11 are the deflection results for instrument line E while Cylinder 2 was applying load to the center span. Deflections were measured on the top flange of each beam. It is evident in the deflection results presented in Figure 5.11 that the center span was working as a system. At the maximum loading for this test, 138 kips, the loaded beams Beam 1, 2, and 3 had the largest deflection response (-.57 for Beam 1). However, Beam 9 still had a deflection of This displays that the center span is deflecting as a system of beams.

73 73 Beams 1 and 2 display similar deflections throughout this test, this behavior could be because of the poor condition of Beam 1 or that Beam 1 was an exterior beam. This behavior is also an indication of how the transverse load distribution system is working. Beam 1 has less stiffness compared to Beam 2, however the relative deflection between the two beams is minimal even at large loads. The transverse load distribution system, composed of the transverse tie rods and shear key, is causing additional deflection of Beam 1 as Beam 2 deflects. This behavior is also evident in the strain results presented in Figure 5.2. Beam 1 experiences relatively larger strain than Beam 2, even when more load was being applied to Beam 2 than Beam 1. Beam 1 experiences more strain than Beam 2 because Beam 1 likely had a lower stiffness.. Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam Deflection, in kips 38 kips 49 kips 55 kips 138 kips 59 kips Position, ft Figure 5.11 Deflection results on Line ET for Cylinder 2 loading on the center span

74 74 Presented in Figure 5.12 are the deflection results for Line ET while Cylinder 5 was applying load to the center span. Similar to previous observation, the beams loaded by the cylinder deflect the most. Once again, the results display that the center span behaves as a system of beams. The deflection profile for Line ET resembles the behavior observed in the distribution of strain for Line ET in Figure 5.3. However, the north side of the span (Beams 6, 7, 8, and 9) experienced slightly larger deflections than the south side (Beams 1, 2, 3, and 4). The opposite trend was observed in the strain data displayed in Figure 5.3. This trend may be explained by the effects of the asphalt overlay that was left Beams 1, 2, and 3. Asphalt does not have higher flexural strength relative to concrete but it appears that the asphalt overlay may have caused a shift in the location of the neutral axis of the beams on the south side of the center span. The location of the neutral axis was shifted towards the top flange of the beams relative to the beams where the asphalt overlay was removed. This would cause the strain readings taken on the bottom flange of the beams on the south side of the span to be larger than expected relative to the deflection results observed in Figure This may not be the only factor causing the unusual trend in the strain and deflection results. A combination of factors could also affect the relationship between the strain and deflection results such as the asphalt allowing more longitudinal distribution of the load.

75 75. Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam Deflection, in Position, ft Figure 5.12 Deflection results on Line ET for Cylinder 5 loading on the center span kips 24 kips 48 kips 66 kips 8 kips 9 kips 111kips 3 Displayed in Figure 5.13 are the deflection profiles for Line ET. In these tests Cylinder 8 was applying load to the center span. The distribution of deflection from the north side (Beam 9) to the south side (Beam 1) of the center span from these tests is similar to a mirror image of the results presented in Figure The deflection behavior of the center span was consistent for all magnitudes of applied load. Throughout the deflection results presented in Figure 5.13, the beams which deflect the most deflect approximately three times as much as the beams with the smallest deflections. This shows that the center span deflected as a system when the north side of the span was loaded.

76 76. Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam Deflection, in Position, ft Figure 5.13 Deflection results on Line ET for Cylinder 8 loading on the center span kips 28 kips 38 kips 42 kips 55 kips 8 kips 9 kips 3 The results presented in Figures 5.14, 5.15, and 5.16 are the deflection profiles for instrument line DT. There was not a string potentiometer installed on Beam 9 for this instrument line because the concrete of the top flange of Beam 9 at this location was severely degraded. These results display similar behavior as the results presented in Figure 5.11, 5.12, and However, these deflection profiles have a smaller magnitude because these deflection results were monitored 14.5 closer to the west pier than the deflections for Line ET. The deflections observed on Line ET are approximately one and a half times larger than the deflections for Line DT for Beams 1-8. This shows that the center span also deflected consistently along the length of each beam when the span experiences load at multiple locations.

77 77. Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam Deflection, in kips 38 kips 49 kips 55 kips 138 kips 59 kips Position, ft Figure 5.14 Deflection results on Line DT for Cylinder 2 loading on the center span. Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam Deflection, in kips 24 kips 35 kips 48 kips 66 kips 8 kips 9 kips 111kips Position, ft Figure 5.15 Deflection results on Line DT for Cylinder 5 loading on the center span 9 6 3

78 78. Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam Deflection, in kips 28 kips 42 kips 38 kips 55 kips 8 kips 9 kips Position, ft Figure 5.16 Deflection results on Line DT for Cylinder 8 loading on the center span 5.2. Center Span Simultaneous Loading Simultaneous loading of all cylinders was conducted to determine the behavior of the center span under extreme load conditions as well as the ultimate capacity of the span. This procedure consisted of applying load to each span with all of the cylinders simultaneously and monitoring the strains and deflection of each beam at the locations previously discussed. The results of the simultaneous loading test consisted of multiple test files. This was done to reduce the size (in bytes) of each file. Load remained nearly constant while these files were saved. Prior to each test file starting, the electrical resistance strain gages in the quarter bridge configuration were balanced by the data acquisition system. The balancing re-zeroed the strain reading for each gage. In order to have continuous strain

79 79 data, the results in each test file were combined into one large file to simplify the data analysis processes. This required the final strain reading of each test for each strain gage to be added to the corresponding strain readings in the proceeding test. The balancing performed by the data acquisition only affected the readings of the electrical resistance strain gages. The calibration coefficient for the strain transducers and the sensitivities for the string potentiometers were also applied to the readings of the appropriate instrumentation as previously discussed. Once the data file for the complete test consisted of properly formatted continuous data for all of the instrumentation, a data initialization process was conducted on each of the instrument readings. This process consisted of taking an average initial reading for each instrument when no load was applied to the span by the cylinders. The average initial readings were then subtracted from the continuous readings to arrive at the final data. Similar to the single cylinder loading tests, periods of constant applied load (plateaus) were observed and recorded. Average instrument readings were found for each time period. These readings were then plotted for each instrument to show the behavior of the span under extreme loading conditions Strain Readings During the simultaneous loading testing of the center span, very large loads were applied onto the span. A maximum load of 467 kips was applied to the center span through all three cylinders before the span was unable to resist any additional load.

80 8 When the span was subject to large magnitude of load, tensile cracking occurred in the bottom flanges of the beams. When a crack occurred at a location of a strain gage, the readings of the gage became invalid. The large loading also caused the crushing in the top flange of the beam. When the portion of the beam where the strain gage was installed experienced crushing, any further readings from the strain gage were invalid. When the readings of a strain gage changed dramatically, it was assumed that location of the beam experienced either cracking or crushing and the remaining data from that particular gage was considered invalid. Table 5.1 displays the load applied by each cylinder and the total load applied on the center span during the simultaneous load testing. These loads correspond to the strain and deflection results presented in Figures 5.17, 5.18, 5.19, and 5.2. Table 5.1 Cylinder and Total Applied Load to Center Span Applied Load (kips) Cylinder 2 Cylinder 5 Cylinder 8 Total

81 81 Figure 5.17 displays the strain data for instrument Line EB for the simultaneous loading of the center span. Because of cracking in the beams, strain readings were only valid up to a total loading of 28 kips on the center span. The strain profiles presented in Figure 5.17 differ from the strain results of the single cylinder loading test because the beams experiencing the most applied load have lower strain values relative to other beams, especially at higher loads. Note that at the 152 kip loading the loads were approximately the same on all of the cylinders, but at the 28 kip loading more load was being applied by Cylinder 2. The strain results follow this trend if Beams 2, 5, and 8 are negated. This is caused by the tensile cracking of the bottom flange of the loaded beams around the strain gage locations. This tensile cracking may cause the concrete around the cracks to experience less strain because the strain is being transferred to the reinforcement and a stiffer portion of the beam.

82 82 2 Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam 1 Strain, με kips 152 kips 28 kips Position, ft Figure Strain results on Line EB for the simultaneous loading on the center span The strain results for instrument line ET that were obtained during the simultaneous load testing are presented in Figure The 395 kip and 377 kip loadings were taken after the ultimate capacity of the center span was reached. Once the ultimate capacity was reached, the bridge was unable to carry additional load, and as the span was forced to deflect more, the capacity of the span was diminished. The 166 kip and 118 kip loadings were taken while load was being removed from the span. As previously discussed, strain gages were not installed on instrument line ET on Beam 1, 2, 3, and 9. It is difficult to observe the entire behavior of the bridge because of the lack of strain readings. However, the behavior of the beams that were instrumented can be studied. As the load applied to the center span is increased, Beam 6 experiences the most strain. This behavior is unusual because the majority of the load applied (based

83 83 on the contact area) by Cylinder 5 is exerted on Beam 5. In addition, the load from the other cylinders was relatively close in magnitude to the load from Cylinder 5. At some point in the loading procedure, Beam 5 was damaged and was unable to carry as much load as the adjacent beams. With Beam 5 unable to carry as much load, the load was then transferred to the adjacent beams by the shear keys and transverse tie rods. This trend also appears on Beams 7 and 8. With closer inspection of the strain data for Beam 8 throughout all of the loading procedures it becomes evident that Beam 8 was more degraded than the adjacent beams. The strain for Beam 8 for each test doesn t change as much as would be expected relative to the other beams, especially when a majority of the Cylinder 8 loading was applied to Beam 8. This behavior shows that Beam 8 had a lower load capacity than the other beams because it was unable to withstand the higher loads and consequently more load was transferred to the beams with higher load capacities. The lowered capacity of Beam 8 could have been caused by several factors which include cracking of the shear keys adjacent to Beam 8 during the service life of the bridge. The cracking of the shear key would allow salt laden water to penetrate between the beams which could lead to corrosion of the steel reinforcement and cracking of the concrete. The adjacent Beam 9 may also have a lower load capacity which is common in the fascia beams because of increased exposure to the elements. The strain profiles for instrument line DT, observed during the simultaneous loading procedure are presented in Figure These strain profiles are similar to the results presented in Figure 5.18 with smaller magnitude. The smaller magnitude may also be the

84 reason for the more consistent values across the width of the center span at this instrument line compared the Beam 6 shown in Figure Strain, με Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam kips 152 kips 28 kips 298 kips 332 kips 367 kips 426 kips 45 kips 395 kips 377 kips 166 kips 118 kips Position, ft Figure Strain results on Line ET for the simultaneous loading on the center span

85 85 5 Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam 1 Strain, με kips 152 kips 28 kips 298 kips 332 kips 367 kips 426 kips 45 kips 395 kips 377 kips 166 kips 118 kips Position, ft Figure Strain results on Line DT for the simultaneous loading on the center span Deflection Readings The deflection results for instrument line ET are presented in Figure 5.2. These results are for the simultaneous load testing. Technical difficulties were experienced with the string potentiometer mounted to Beam 5 during the simultaneous loading test which resulted in unusable data for the deflection of Beam 5 on instrument line ET. It appeared from the readings given by the string potentiometer instrumented on Beam 5 that the wiring had been damaged which affected the data from this string potentiometer. The deflection profiles displayed in Figure 5.2 were consistent throughout the loading procedure. Beam 8 had a slightly larger deflection than the adjacent beams which reiterates the conclusion that Beam 8 was degraded. Once the ultimate capacity of the span was reached, the deflections of Beams 1 and 2 increased relative to the previous

86 86 loading results. The increase in deflection could be from several reasons. A failure of the shear key between Beams 2 and 3 would cause the increased deflection of Beams 1 and 2. Also, if the capacity of Beams 1 and 2 was reached this could cause an increased in deflection. Without strain data for these beams the cause of the increase in deflection can only be speculated. Figure 5.21 presents the deflection profiles for instrument line DT during the simultaneous loading procedure. The poor condition of Beam 9 made mounting a string potentiometer to the top flange of the beam problematic. Therefore, a string potentiometer was not mounted to Beam 9. These profiles are similar to the results presented in Figure 5.2 with a smaller magnitude. Deflection, in. Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam kips 28 kips kips kips 367 kips kips 45 kips kips kips 166 kips kips Position, ft Figure 5.2 Deflection results on Line ET for simultaneous loading on the center span

87 87. Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam 1 Deflection, in Position, ft Figure Deflection results on Line DT for simultaneous loading on the center span kips 28 kips 298 kips 332 kips 367 kips 426 kips 45 kips 395 kips 377 kips 166 kips 118 kips 5.3. West Span Single Cylinder Loading The west span strain and deflection data for the single cylinder loading and the simultaneous tests was initialized and analyzed in the same manner as the center span data. Controlled damaged was applied to Beams 4, 5, and 6 to study how the behavior of the span was affected by damaged beams Strain Readings Figure 5.22 displays the tensile strain results for instrument line AB while only Cylinder 2 was applying load to the west span. On this instrument line strain gages were also mounted to the edges of Beams 2, 3, and 4. The strain readings observed for the strain gages on the adjacent edges of Beams 2 and 3 were lower than the corresponding

88 88 gages located at the center of these beams. The strains were lower on the edges of the beams because there was a strain discontinuity where the beams meet the shear key. This would also account for the significant decrease in strain distribution between Beams 2 and 3. The gage installed on the north edge of Beam 3 experienced technical problems and therefore the data provided by this gage was not useful. Similar to the center span, Beam 9 of the west span was severely degraded and a strain data for this beam was not usable. Beam 2 experienced the largest strain of the beams on this instrument line, which is what is expected because it was subjected to the largest loading based on the contact area of Cylinder 2. However, Beam 7 usually experienced larger strains than the three damaged beams even though the load was applied closer to the damaged beams. This shows that the damaged beams had a lower load capacity relative to the adjacent undamaged beams and therefore the load transfer system transferred more load to the stiffer beams.

89 89 Strain, με 27 Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam kips kips kips 17 8 kips kips kips Position, ft Figure 5.22 Strain readings on Line AB for Cylinder 2 loading on the west span The tensile strain profiles for instrument line AB while Cylinder 5 was applying load to the west span are presented in Figure Similar to the previous strain results for the gages installed on the edges of the Beams 2 and 3, there was a decrease in strain readings between these beams because of the shear key. The effect of the damaged beams, Beams 4, 5, and 6, is more evident while Cylinder 5 was applying load to the west span because the load was applied to the damaged beams. The damaged beams experience lower strains than the adjacent beams even when the load was applied directly to the damaged beams. These lower strain values show that there was a plastic hinge developing at the damaged sections of Beams 4, 5, and 6. The hinge formed because the steel reinforcement carried a majority of the tensile strains of the damaged beams. When the

90 9 reinforcement yielded, the damaged beams were unable to resist any addition tensile stresses. It seems that the hinges began developing between the loadings of 42 kips and 73 kips. Once the 73 kip load was reached, the damaged beams did not experience a significant change in strain as additional load was applied to the span. The additional load appeared to be transferred to the adjacent undamaged beams. Strain, με Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam 1 1 kips 24 kips 42 kips 73 kips 87 kips 1 kips Position, ft Figure 5.23 Strain readings on Line AB for Cylinder 5 loading on the west span Figure 5.24 displays the tensile strain results for Line AB while Cylinder 8 applied load to the west span. As would be expected, the loaded beams experienced the largest strains. There was a significant decrease in strain between Beams 6 and 7 because of the condition of Beam 6. The transfer of load through the damaged beams was not as evident in Figure 5.24 as in previous figures, but the strain values of the beams on the opposite

91 91 side of the span from the load were larger than the strains recorded for the damaged beams. This trend is similar to the trend observed in Figure 5.22 when the opposite side of the west span was loaded. After studying Figures 5.22, 5.23, and 5.24, it appears the damage did not affect Beam 4 as much as the other damaged beams. Beam 4 experienced larger strains in all three cylinder loadings relative to Beams 5 and 6. Again, the strain gages on the edges of Beams 2 and 3 show that there was a decrease in strain distribution between these beams even at lower magnitudes of strain. Strain, με Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam 1 17 kips 31 kips 42 kips 52 kips 9 kips 14 kips Position, ft Figure 5.24 Strain readings on Line AB for Cylinder 8 loading on the west span The compressive strain results for instrument line AT while Cylinder 2 was applying load to the west span are displayed in Figure On instrument line AT, the poor condition of Beams 1 and 9 prohibited the installation of a strain gage. The strain

92 92 distribution across the west span for this loading case displays a consistent behavior throughout the loading procedure. The strain readings from Beam 2 shown in Figure 5.25 were considerably low when compared to the corresponding tensile strain for Beam 2 on instrument line AB shown in Figure This could have been caused by corrosion of the top flange of Beam 2 as well as poor adhesion of the strain gage to the concrete. Similar to Figure 5.22, Beam 7 experiences larger strains than the adjacent Beams 5 and 6 even though the load is applied closer to these beams. This may be because of the damage applied to Beam 4, 5, and 6. This shows that the load was still transferred through the damaged beams and the undamaged beams are carrying more of the load than the damaged beams. The plastic hinge effect previously discussed was not as evident on this instrument line. However, the damaged beams did experience lower strain relative to the adjacent undamaged beams. The plastic hinge effect wasn t clearly presented because these gages were installed on the top flange on the beams and the damage was applied to the bottom flanges of the box beams. The lower strain values observed on the damaged beams was still caused by damaged applied to Beams 4, 5, and 6. The damage created on these beams caused a shift in the location of the neutral axis and a decrease in tensile capacity of the beams. This would lead to a decrease in the compressive strain experienced by the damaged beams.

93 93 Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam 1-2 Strain, με kips 55 kips 62 kips 8 kips 97 kips 14 kips Position, ft Figure 5.25 Strain readings on Line AT for Cylinder 2 loading on the west span Figure 5.26 displays the compressive strain results for Line AT while Cylinder 5 was applying load to the west span. As previously discussed, again Beam 2 exhibits much smaller strain readings than would be expected given the tensile strain readings for Beam 2 shown in Figure Similar to previous results, damaged Beams 5 and 6 exhibit smaller strains than the adjacent beams when the load was directly applied to Beams 4, 5, and 6. As previously discussed, these results show the damage applied to Beam 4 did not have as large of an effect on the beams load capacity as the other damaged beams. It seems that the damage created on Beams 5 and 6 caused the entire section to form a plastic hinge because both the tensile and compressive strains are much lower than the strains of the adjacent beams. However, the damage created appears to have only affected the tensile strain of Beam 4. This confirms the conclusion that the remaining

94 tensile strains are carried by the steel reinforcement because the compressive strain continues to increase in Beam Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam Strain, με kips 24 kips 42 kips 73 kips 87 kips 1 kips Position, ft Figure 5.26 Strain readings on Line AT for Cylinder 5 loading on the west span The compressive strain results for Line AT while Cylinder 8 applied load to the west span are displayed in Figure The strain behavior observed in this figure is similar to the distribution on the tensile strain presented in Figure The loaded beams experience the most strain, however the compressive strains recorded on the damaged beams are greater than the strain observed on the beams on the opposite of the load. This displays that the formation of the plastic hinge has not occurred in the entire cross-section of Beams 5 and 6 as was observed in Figure This behavior shows that the plastic hinge effect on the entire cross-section occurs when higher loads were carried by the

95 damaged beams as was the case when the damaged beams were loaded directly in Figure Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam Strain, με Position, ft Figure 5.27 Strain readings on Line AT for Cylinder 8 loading on the west span kips 31 kips 42 kips 52 kips 9 kips 14 kips 3 Figure 5.28 shows the tensile strain data for instrument line BB while Cylinder 2 was applying load to the west span. The strain gage instrumented on Beam 3 of this instrument line failed to balance during testing and consequently the data for this instrument was invalid. The strain profiles displayed in Figure 5.28 differ from the tensile strains presented for Line AB. The difference in these strain profile was caused by discontinuities in the beams cross-section. Instrument line BB was located on the other side of the solid section of the adjacent box beams and the transverse tie rods. This would cause a more uniform distribution of the strain transversely across the bridge. The

96 discrepancies could also have been caused by non-uniform material properties throughout the length of the beams. 96 Strain, με Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam 1 42 kips 55 kips 62 kips 8 kips 97 kips 14 kips Position, ft Figure 5.28 Strain readings on Line BB for Cylinder 2 loading on the west span Displayed in Figure 5.29 are the tensile strain profiles for instrument line BB while Cylinder 5 was applying load to the west span. As previously observed in Figures 5.23 and 5.26, the strains recorded on the damaged beams are lower than the strain observed on the undamaged beams. The effect of the plastic hinge is also evident in these strain profiles, the strains in damaged Beams 4 and 5 does not significantly change once 73 kips was applied to the west span by Cylinder 5. This shows that the damage applied to these beams affected the entire beam and not just the section of the beam where it was

97 damaged. The other damaged beam, Beam 6, also presents effects of the damage at this location. However, it is not as evident as the strain behavior displayed by Beams 4 and Strain, με Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam 1 1 kips 24 kips 42 kips 73 kips 87 kips 1 kips Position, ft Figure 5.29 Strain readings on Line BB for Cylinder 5 loading on the west span The tensile strain profiles for instrument line BB while Cylinder 8 applied load to the west span are presented in Figure 5.3. Because the location of the transverse tie rods were within a close proximity to this instrument line the strain was more efficiently distributed across the west span at this location. The effect of the damaged beams also is not as intense as seen in previous figures because Line BB was further away from the loading and damage locations. However, Beam 5 still demonstrates a decreased load capacity relative to the adjacent box beams. The behavior of Beam 8 is also peculiar in this loading case. Beam 8 was subjected to a majority of the loading from Cylinder 8

98 98 based on the contact area but the strain values measured on Beam 8 on this instrument line are significantly lower than the adjacent Beam 7 and are also among the smallest strain values measured across the entire instrument line. This anomaly could be caused by degraded concrete at or around the location of the strain gages. It is unlikely the gage was installed incorrectly because strain readings were recorded and display consistent behavior throughout the testing procedure Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam 1 17 kips 31 kips 42 kips 52 kips 9 kips Strain, με Position, ft Figure 5.3 Strain readings on Line BB for Cylinder 8 loading on the west span Displayed in Figure 5.31 are the compressive strain profiles for instrument line BT while Cylinder 8 was applying load to the west span. Similar to other instrument lines, strain gages were not installed on Beams 1 and 9 of this instrument line because of the poor condition of the top flange of these beams. The strain distribution displayed in

99 99 Figure 5.31 resembles the strain distribution exhibited in Figure 5.25 for instrument line AT. The only difference in the strain distribution behavior is the distribution of strain between Beams 2 and 3. It appears that there was degradation to the shear keys on both sides of Beam 3 because the beam has lower strain readings as would be expected relative to the strain readings of the adjacent box beams. Beam 2 experiences relatively the same strain on Line BT as Line AT. This is somewhat unusual because the gage on line BT was further away from the loading location relative to Line AT. It seems that Beam 2 carried the additional load that was unable to be carried by Beam 3 due to the damage. This trend shows that even away from the location of the loading that load was transferred to beams with higher load capacities. Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam 1-1 Strain, με kips 55 kips 62 kips 8 kips 97 kips 14 kips Position, ft Figure 5.31 Strain readings on Line BT for Cylinder 2 loading on the west span

100 1 Figure 5.32 presents the compressive strain results for instrument line BT while Cylinder 5 was applying load to the west span. The strain behaviors presented in Figure 5.32 are similar to the strain behaviors presented for instrument line AT in Figure As previously discussed Beam 3 appears to have a lower load capacity at this location relative to the adjacent box beams. This decreased capacity caused Beam 2 to carry addition load. This is evident because the strain values recorded from Beam 2 on Line BT are higher than the magnitudes of strain observed on Beam 2 for Line AT. This trend is unusual because Line BT was further away from the location of the load than Line AT. Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam 1-1 Strain, με kips 24 kips 42 kips 73 kips 87 kips 1 kips Position, ft Figure 5.32 Strain readings on Line BT for Cylinder 5 loading on the west span

101 11 The compressive strain results for instrument line BT while Cylinder 8 was applying load to the west span are shown in Figure The strain behavior observed in Figure 5.33 differs from strain results shown in Figure 5.27 for Line AT. The majority of the load based on the contact area was applied to Beam 8. However, Beam 8 experienced one of the lowest strain values relative to the readings of the other strain gages on this instrument line. This inconsistency of strain distribution along the length of Beam 8 was likely caused by a decreased load capacity between the instrument lines which developed over the 43 year life of the structure. Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam 1 Strain, με kips 31 kips 42 kips 52 kips 9 kips 14 kips Position, ft Figure 5.33 Strain readings on Line BT for Cylinder 8 loading on the west span

102 Deflection Readings Similar to the center span, the deflection results for the west span during the single cylinder testing were found using the load plateaus that were used for the strain results. Figure 5.34 displays the deflection profiles of Line AT while Cylinder 2 was applying load to the west span. The difference in the deflection behavior of Beam 4 after the 55 kips loading was because the 42 kip and 55 kip results were taken while the west span was loaded to approximately 5 kips by Cylinder 2 and the remaining results were taken from the 1 kip loading procedure for this cylinder. During the 1 kip loading processes Beams 4 and 5 deflect together. In general, the deflection profiles presented in Figure 5.34 are what would be expected with the loading applied to Beams 1 and 2. The loaded beams deflected the most relative to the remaining beams. However, all of the remaining beams deflect, generally slightly less than the preceding beam from the loading location. This shows that even with Beams 4, 5, and 6 having being damaged, the west span still deflected as a system. The deflection results shown in Figure 5.34 do not correspond to the compressive strain values presented in Figure 5.25 for the same instrument line. The inconsistency between the strain and deflection profiles was caused by the damage created on Beams 4, 5 and 6. It appears that the capacity of the damaged beams has been decreased which resulted in lower recorded strains on the damaged beams. However, because the beams are tied together as a system with transverse tie rods and shear keys the beams deflect as a system. This additional deflection of the damaged beams was most likely rigid body

103 motion of the damaged beams caused by the formation of a plastic hinges at the locations of the damage on Beams 4, 5, and Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam Deflection, in kips 55 kips 62 kips 8 kips 97 kips 14 kips Position, ft Figure 5.34 Deflection readings on Line AT for Cylinder 2 loading on the west span The deflection results for instrument line AT while Cylinder 5 was applying load to the west span are presented in Figure Similar to other loading procedures, the deflection profiles presented show that the west span deflects as a system with the loaded beams deflecting the most and the remaining beams deflect slightly less relative to the preceding beam from the loading location. The inconsistency between the strain and deflection readings for this loading procedure is also evident while observing Figure 5.26 and Figure This inconsistency was caused by the decreased load capacity of the damaged beams and the consequent rigid body motion of the damaged beams as

104 14 previously discussed. It should be noted that Beams 3 and 4 have similar magnitudes of deflection while the west experienced a load of 73 kips from Cylinder 5 and when the applied load increased to 87 kips the beams deflected in a manner similar as seen at the lower magnitudes of load.. Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam Deflection, in Position, ft Figure 5.35 Deflection readings on Line AT for Cylinder 5 loading on the west span kips 24 kips 42 kips 73 kips 87 kips 1 kips 3 Figure 5.36 shows the deflection results for instrument line AT while Cylinder 8 was applying load to the west span. As was observed in previous deflection results for the west span, the west span deflects similar to what would be expected. The loaded beams experience the largest deflection relative to the non-loaded beams. The non-loaded beams also deflected slightly less than the preceding beam relative to the location of the loading. This trend in each of the loading cases for this loading procedure shows that the

105 15 west span deflected as a system with no bias to where the load was applied. Similar to the behavior of Beams 3 and 4 observed in Figure 5.35, Beams 3 and 4 have similar magnitudes of deflection while 14 kips was applied to the west span by Cylinder 8. This behavior occurs at a higher load applied by Cylinder 8 than was applied by Cylinder 5 when the behavior occurred at 73 kips. This may mean that the load carried by the Beams 3 and 4 was similar and the total load applied to the bridge differs because of the location of the loading. Similarly to the rigid body motion of the damaged beams already discussed there was an inconsistency between the strain and deflection results while Cylinder 8 was applying load to the west span.. Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam Deflection, in Position, ft Figure 5.36 Deflection readings on Line AT for Cylinder 8 loading on the west span 9 17 kips 31 kips 42 kips 52 kips 9 kips 14 kips 6 3

106 16 The deflection results for instrument line BT are presented in Figures 5.37, 5.38, and 5.39 while Cylinder 2, Cylinder 5 and Cylinder 8, respectively, were applying load to the west span. The deflection results presented in these figure show similar behavior to the deflection results shown for instrument line AT in Figures 5.34, 5.35, and However, the magnitudes of the deflections shown for Line BT are smaller than the deflections reported for Line AT because line BT was further away from the location of the loading. The irregularities observed from the deflection results for Line AT are not as apparent for the deflection readings from instrument line BT. This was probably because instrument line BT was further away from the location of the loading and the applied damage. Also, there were solid sections and transverse ties rods were located between instrument lines AT and BT. The transverse ties rods would cause any irregularity in the defection profile to be mitigated.

107 17. Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam Deflection, in kips 55 kips 62 kips 8 kips 97 kips 14 kips Position, ft Figure 5.37 Deflection readings on Line BT for Cylinder 2 loading on the west span. Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam Deflection, in kips 24 kips 42 kips 73 kips 87 kips 1 kips Position, ft Figure 5.38 Deflection readings on Line BT for Cylinder 5 loading on the west span 9 6 3

108 18. Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam Deflection, in Position, ft Figure 5.39 Deflection readings on Line BT for Cylinder 8 loading on the west span 9 17 kips 31 kips 42 kips 52 kips 9 kips 14 kips West Span Simultaneous Loading Similar to the center span, simultaneous loading was conducted on the west span. Large loads were applied to west span by all of the cylinders simultaneously and a maximum load of 367 kips was reached. The ultimate capacity of the west span was considered to be 367 kips because when this loading was reached the west span was unable to resist any additional load. However, after this loading was reached additional displacements were applied to the span but the total load resisted by the span decreased. Shown in Table 5.2 are the loads applied by each cylinder and the total applied load throughout the simultaneous loading procedure. The 35 kip and 322 kip total applied loads occurred after the ultimate capacity of the west span was reached while still continuing to load the span.

109 19 Table Cylinder and Total Applied Load to West Span Applied Load (kips) Cylinder 2 Cylinder 5 Cylinder 8 Total Strain Readings The tensile strain results for instrument line AB during the simultaneous loading procedure of the west span are shown in Figure 5.4. Similar to simultaneous loading procedure of the center span, the strain results for this instrument line are only shown for the loadings up to 34 kips. This is because after a total load of 34 kips was reached, cracking of the bottom flange of several of the beams invalidated data recorded from the strain gages on those beams. The plastic hinging effect previously discussed for the single cylinder loading of the west span is also evident in Figure 5.4. Throughout the entire simultaneous loading procedure the damaged beams were unable to withstand high magnitude tensile strains. The decreased load capacity of Beams 3 and 7 are also apparent in this figure. Between the 21 kip and 251 kip loading, strain in Beam 7 dropped off dramatically. This same behavior occurred on Beam 3 between the 251 kip and 34 kip loadings. This behavior may be caused by the increase in load carrying demand on these beams. The increase demand was due to the decreased capacity of the

110 11 damaged beams (Beams 4, 5, and 6). It can be expected that the beams adjacent to the damaged beams would be the first beams to reach ultimate capacity due to high load levels. Strain, με Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam 1 1 kips 21 kips 251 kips 34 kips Position, ft Figure Strain results on Line AB for the simultaneous loading on the west span Displayed in Figure 5.41 are the compressive strain results for instrument line AT during the simultaneous loading procedure of the west span. As previously discussed for the single cylinder testing of the west span, the damage applied to Beams 4, 5, and 6 did not seem to affect the behavior of Beam 4 relative to the behavior of Beams 5 and 6. However, it is still apparent that the damage has caused a decreased load carrying capacity of Beam 4. Once a total loading of 251 kips was reached, it appears that the Beams 5 and 6 experienced a plastic hinging effect throughout the entire cross-section of

111 these beams at the location of instrument line A. Also, it appears that the capacity of the damaged beams continues to decrease after a total applied load of 251 kips was reached. 111 Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam Strain, με kips 21 kips 251 kips 34 kips 367 kips 35 kips 322 kips Position, ft Figure Strain results on Line AT for the simultaneous loading on the west span The tensile strain results for instrument line BB during the simultaneous loading procedure of the west span are displayed in Figure There is not any strain results presented for the 322 kip loading on this instrument line because of the cracking of the bottom flange on the beams at this location. As discussed for instrument Line AB the decreased load capacity of the damaged beams is very evident once a total applied load of 21 kips was reached because there was no significant change of the strain values for the damaged beams. Similar to the strain results for instrument line AB, it appears that the beams adjacent to the damaged beams carry the addition load that the damaged beams

112 were unable to resist. Once again, it seems as if the capacity of the damaged beams decreases more after a total applied load of 251 kips was achieved. 112 Strain, με Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam 1 1 kips 21 kips 251 kips 34 kips 367 kips 35 kips Position, ft Figure Strain results on Line BB for the simultaneous loading on the west span Presented in Figure 5.43 are the compressive stain results for instrument line BT during the simultaneous loading procedure of the west span. Similar to the strain results presented in Figure 5.41 for instrument line AT, the plastic hinge effect of the entire cross-section once a total applied load of 251 kips was reached was displayed on in the strain readings for this instrument line. Also, the beams adjacent to the damaged beams seem to carry the majority of the load as indicated by the higher strain values recorded for these beams relative to the other beams of the west span. As discussed for the strain

113 results of previous instrument lines, the capacity of the damaged beams appears to decrease more when a total applied load of 251 kips was attained. 113 Strain, με Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam kips 21 kips 251 kips 34 kips 367 kips 35 kips 322 kips Position, ft Figure Strain results on Line BT for the simultaneous loading on the west span Deflection Readings The deflection results for instrument line AT during the simultaneous loading procedure of the west span are shown in Figure In general, the deflection profiles of the west span on this instrument line are uniform across the width of the span. The maximum deflection recorded for this span was approximately -4.2 on Beam 5. Once the load applied by Cylinder 5 was increased too much higher magnitudes relative to the other cylinders, the center of the span begins to deflect more which is displayed in the results for the 34 kip loading. It appears in the deflection profiles presented that there

114 was a separation between Beams 8 and 9. The separation of these beams could be caused by a failure of the shear key Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam Deflection, in kips 21 kips 251 kips 34 kips 367 kips 35 kips 322 kips Position, ft Figure Deflection results on Line AT for the simultaneous loading on the west span Figure 5.45 shows the deflection results for instrument line BT during the simultaneous loading procedure of the west span. The deflection profiles presented in this figure are mostly uniform across the width of the west span. These deflection profiles are similar to the profiles displayed in Figure 5.44 for instrument line AT. However, these deflections results are more uniform across the west span relative to the results for Line AT. The deflections are more uniform because these deflections were recorded further away from the loading and damage location which may cause discontinuities in the deflection profiles. There were transverse ties rods and solid

115 115 sections also located between Line AT and Line BT which would also cause the deflection profiles to be more uniform across the width of the span at this instrument line. Also similar, is the separation between Beams 8 and 9 which may have been caused by a failure of the shear key between the two beams.. Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam Deflection, in kips 21 kips 251 kips 34 kips 367 kips 35 kips Position, ft Figure Deflection results on Line BT for the simultaneous loading on the west span 5.5. Comparison of the Center Span to the West Span To determine how the damage applied to the west span affected the behavior of the span, the strain results for instrument line AB were compared to the strain results for instrument line EB of the center span. These instrument lines were selected because the strain gages on the bottom flanges of the beams were the most critical and had the most consistent results. Also, the gages of these instrument lines were closest to the location

116 116 of the loading. Strain results for each span were selected when similar magnitude and location of load was being applied. The strain results while Cylinder 2 was applying load to the center span and the west span are presented in Figure It can be observed in this figure that the damage beams experience less strain than the corresponding undamaged beams of the center span. Also, the undamaged beams of the west span experience larger strains than the corresponding beams of the center span. This behavior shows that when beams within a span are damaged the beams that have higher load capacity will carry more of the load, relative to the damaged beams. This means that the transverse load transfer system can adequately transfer loads across the bridge span even when the span has damaged beams. Strain, με Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam 1 24 EB-38 kips AB-42 kips EB-55 kips AB-55 kips Position, ft Figure 5.46-Strain comparison of Lines EB and AB while Cylinder 2 was applying load 9 6 3

117 117 The strain results for instrument lines EB and AB for the center and west span, respectively, while Cylinder 5 was applying load to the spans are compared in Figure The effect of the damaged beams on the overall span behavior is the most evident at this loading location because the load was applied directly to the damaged beams. When higher loads were applied to the spans it can be seen that the loaded damaged beams of the west span experienced significantly less strain than the loaded undamaged beams of the center span. The beams of the center span experience a strain distribution transversely across the span similar to what would be expected, with the loaded beams experiencing the largest relative strain values with each adjacent beam experiencing slightly less strain. The only exception to this behavior occurred in the fascia beams of the center span with were severely degraded on the external web of the beams. However, this was not the case for the west span which had the three damaged interior beams. For this span the damaged beams experienced less strain relative to the adjacent undamaged beams. This behavior shows that the west span was able to transfer load transversely across the span even though three of the interior beams were subjected to severe damaged.

118 118 Strain, με Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam 1 EB-24 kips AB-24 kips EB-48 kips AB-42 kips EB-8 kips AB-87 kips Position, ft Figure 5.47-Strain comparison of Lines EB and AB while Cylinder 5 was applying load The strain results for instrument lines EB and AB while Cylinder 8 was applying load to the respective spans are displayed in Figure The results compared in this figure show that the damaged beams of the west span did not have as great of an effect on the load transfer behavior of the span when the load is not applied near the damaged beams. The damaged beams of the west span did experience less strain relative to the corresponding undamaged beams of the center span. However, the difference in the strain experienced by these beams can be considered insignificant relative to the total strain experienced by the entire west span. In general, the center and west spans have similar transverse strain distributions when the undamaged beams were loaded even with three damaged beams on the west span.

119 119 Strain, με Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam Position, ft Figure 5.48-Strain comparison of Lines EB and AB while Cylinder 8 was applying load 9 EB-28 kips AB-31 kips EB-42 kips AB-42 kips EB-9 kips AB-9 kips 6 3 Figure 5.49 displays the deflection results for instrument lines ET and AT of the center and west span, respectively. In this figure the deflection results were taken while Cylinder 2 was applying load to the center and west spans. When comparing the deflections from the undamaged center span to the deflections of the damaged west span it unusual that the west span experiences relatively less total deflection. However, the difference in deflections between corresponding beams of each span was actually very small. This unusual behavior may be explained by the difference in boundary conditions. On the center span, the beams were supported at each end by the two piers. As specified in the bridge drawings the beams of the center span were supported 17¼ along each end of the beams. The beams of the west span were supported by the west pier and west abutment. The supported length of the east side of the beams of the west span is the same

120 12 as the center span, however, on the west side of the beams where supported at a length of 21 by the abutment. Nevertheless, it is more important to observe the tendencies of each span to deflect as a system rather than the magnitude of the deflection because the difference in magnitude is very small. Relative to the west span, the center span deflects more as a system transversely across the bridge when the south side of the bridge was loaded. The change in magnitude between adjacent beams is smaller on the center span, relative to the deflections of the west span. However, the west span also generally has a uniform distribution of deflection transversely across the span and the difference in magnitudes of the deflections of corresponding beams of the center and west spans are very small. Since the west span had three damaged interior beams it would be expected that the damaged beams would deflect much more relative to the adjacent undamaged beams. However, it seems that the entire span was deflecting as a system even with damaged beams.

121 121 Deflection, in Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam Position, ft Figure Deflection comparison of Lines ET and AT while Cylinder 2 was applying load 9 6 EB-38 kips AB-42 kips EB-55 kips AB-55 kips 3 Presented in Figure 5.5 are the deflection results for both the center and west spans as Cylinder 5 applied load to these spans. The results shown are for instrument lines ET and AT of the center and west spans, respectively. As discussed before, at lower magnitudes of applied load, the center span deflects more relative to the west span and this may be caused by a difference in boundary conditions. The deflection results shown in Figure 5.5 show that the center and west spans had similar deflection profiles. This reiterates the idea that even with three severely damaged interior beams in west span the span behaved as a system. Meaning that even with an extremely decreased load capacity in three of the beams, the load transfer system of the west span was able to distribute the load to beams able to carry the load resulting in similar deflection behavior as the undamaged center span carried the load.

122 122 Deflection, in Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam Position, ft Figure Deflection comparison of Lines ET and AT while Cylinder 5 was applying load 9 6 EB-24 kips AB-24 kips EB-48 kips AB-42 kips EB-8 kips AB-87 kips 3 The deflection results for instrument lines ET and AT for the center and west span while Cylinder 8 was applying load to each span are displayed in Figure Similar to the results presented in Figures 5.49 and 5.5, the center span deflected slight more than the west span and the reason for this were previously discussed. In this figure it can be observed that while the each span was loaded on the north side of the bridge that each span deflected in a similar manner. This trend shows that the center and west spans were behaving as systems. When comparing the deflection profiles of the undamaged center span to the damaged west span at each loading location it was shown that the west span was able to transfer load from and even through the damaged interior beams. Also, each

123 span had the capacity to carry the applied load and was also able to distribute the load transversely so that all of the beams contributed in carrying the applied load. 123 Deflection, in. Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam EB-28 kips AB-31 kips -.3 EB-42 kips AB-42 kips -.35 EB-9 kips AB-9 kips Position, ft Figure Deflection comparison of Lines EB and AB while Cylinder 8 was applying load The strain results for instrument lines ET and AT of the center and west spans while all of the cylinders were applying load to each span is presented in Figure The distribution of loads applied by the cylinders are provided in Tables 5.1 and 5.2. Instrument lines ET and AT were used for this comparison because the results from the gages on the bottom flange of the beams were often invalid because of the large tensile strains. This figure shows how each span transferred load while being loaded at multiple locations. As expected from previous results the damaged beams of the west span experience considerably less strain than the corresponding undamaged beams of the

124 center span and the beams adjacent to the damaged beams to the north side of the bridge experienced much larger strains than the corresponding beams of the center span. 124 Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam 1 Strain, με ET - 28 kips AT - 21 kips ET kips AT - 34 kips ET kips AT kips Position, ft Figure Strain comparison of Lines ET and AT while all cylinders were applying load Figure 5.53 shows the deflection results for instrument line AT and BT of the center and west span, respectively. These results were taken while the bridge was loaded by all three cylinders. Contradictory to what was presented for the single cylinder loading, in this loading case the west span deflected relatively more than the center span especially at large applied loads. The deflection profiles of each span are similar throughout the entire load procedure. At the maximum load of 367 kips there was a separation between Beams 8 and 9 which is apparent in the results. The deflection of the west span at the ultimate

125 125 load of 367 kips was approximately larger than the deflection experienced by the corresponding beams of the center span. This increased deflection across the entire span shows that the west span even under ultimate loading conditions with three severely damaged beams deflected as a system showing that the load transfer system had an adequate capacity to carry any load that normal truck traffic could apply to the bridge. This is also true for the center span which was undamaged and had an ultimate capacity of 467 kips. Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam Deflection, in ET - 28 kips AT - 21 kips ET kips AT - 34 kips ET kips AT kips Position, ft Figure Deflection comparison of Lines EB and AB while all cylinders were applying load Presented in Figure 5.54 is the load versus deflection plots for the center and west spans. In this figure, the total applied load was plotted against the average beam

126 126 deflection for each span. It seems that the spans behave similarly up to a total applied load of 15 kips. The center span was able to carry a total applied load of 467 kips and had a corresponding average deflection of approximately 4.2. The average maximum deflection was approximately 6.8 and the average permanent deflection was approximately 2.6. The west span had an ultimate capacity of 367 kips and had a corresponding average deflection of approximately 3.2. The average maximum deflection was approximately 3.9 and the average permanent deflection was approximately 1.2. These results show that the undamaged center span was more ductile than the damaged west span. West Span Center Span Figure 5.54 Load vs. Deflection plots for the Center and West Spans

127 127 CHAPTER 6: FINITE ELEMENT RESULTS OF THE WEST SPAN A finite element model of the west span was created using Abaqus/CAE 6.1. This model took into account the damage created on the west span as well as the material properties of the beams acquired from testing. The boundary conditions of the west span were also included in the model. The model included the effects of the abutment, pier, dowel rods, and the continuity effects of the connection between the west and center spans. Once an accurate finite element model was produced, the strain and deflection results output by the model were compared to the results of three selected loading cases obtained during the destructive testing of the west span. The loading cases selected were taken from the single cylinder loading of the west span. The first loading case was when Cylinder 2 was applying 62.3 kips, the second was when Cylinder 5 was applying 72.7 kips, and the final loading case was when Cylinder 8 was applying 51.9 kips Strain Comparison Figure 6.1 shows the comparison of the strain results acquired from the finite element model to the experimental results of the destructive testing done on the damaged west span. A strain comparison for the results of both instrument lines, AB and BB, while Cylinder 2 was applying 62 kips to the west span are shown in Figure 6.1. It can be seen that the finite element model closely simulates the strain distribution behavior of the west span while the south side of the span was loaded. The finite element model emulates the higher strains on the loaded beams, as well as the significant drop in strain on the damaged beams. The behavior of the beams adjacent to the damaged beams and away of

128 128 from loading, in this case Beams 7 and 8, having larger strain than the damaged beams was also emulated with the finite element model. The average difference in strain between the finite element model and the experimental results for instrument lines AB and BB was 9.29 με Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam 1 Exp.-AB FEM-AB Exp.-BB FEM-BB Strain, με Position, ft Figure Strain comparison of the finite element model and experimental results for the west span while loaded by Cylinder 2 (AB and BB Lines) Displayed in Figure 6.2 is the strain comparison of the finite element model to the experimental results for instrument lines AB and BB while Cylinder 5 was applying 73 kips to the west span to the west span. Figure 6.2 shows that the finite element model was able to accurately imitate the strain distribution behavior of the damaged west span when load was applied to the damaged beams of the west span. This included the behavior where the loaded damaged beams experienced lower relative strain values than

129 the adjacent undamaged beams. The average difference in strain between the finite element model and the experimental results for instrument lines AB and BB was 3.1 με Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam 1 Exp.-AB FEM-AB Exp.-BB FEM-BB Strain, με Position, ft Figure 6.2 Strain comparison of the finite element model and experimental results for the west span while loaded by Cylinder 5 (AB and BB Lines) Presented in Figure 6.3 is the strain comparison of the results from the finite element model and the experimental testing of the west span while 52 kips was applied to the west span by Cylinder 8. In this loading case, the finite element model was able to mimic the strain behavior of the loaded beams. However, the larger relative strain of the beam adjacent to the damaged beams and opposite of the loading was not achieved. Despite the finite element model being unable to model this strain distribution, the general strain distribution across the entire span provided by the finite element model closely resembles

130 13 the results obtained during destructive testing. The average difference in strain between the finite element model and the experimental results for instrument lines AB and BB was 8.72 με Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam 1 Exp.-AB FEM-AB Exp.-BB FEM-BB Strain, με Position, ft Figure Strain comparison of the finite element model and experimental results for the west span while loaded by Cylinder 8 (AB and BB Lines) Deflection Comparison Similar to the strain distribution behavior of the west span, the deflection profiles provided by the finite element model were also compared to the corresponding deflection results from the experimental testing of the west span. Figure 6.4 provides a comparison of the deflection results from the finite element model to the results from the destructive testing of the west span while Cylinder 2 was applying load to the span. The deflection results yielded by the finite element model

131 131 were larger relative to the experimental deflection results for the beams that were in close proximity to the loading location and the opposite was true for the beams away from the loading. This behavior may be explained by the assumption made for the model that the material properties of the beams were uniform throughout the entire beam. The model does not take into account any unknown discontinuities in the material properties of the beams. The magnitudes of the deflections are also small which makes matching the deflection results more difficult. The average difference between the deflection results of the finite element model and the experimental results was.4 while the span was loaded by Cylinder 2. Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam 1 Strain, με Exp.-A FEM-A Exp.-B FEM-B Position, ft Figure Deflection comparison of the finite element model and experimental results for the west span while loaded by Cylinder 2 (A and B Lines)

132 132 Similar to when the span was loaded by Cylinder 2, Figure 6.5 shows that the deflection results found using the finite element model were larger than the experimental results when Cylinder 5 was applying load to the west span. Again, this behavior may be caused by the assumptions made when developing the finite element model. The results provided by the finite element model offer a reasonable approximation of the general deflection profile. The average difference between the deflection results of the finite element model and the experimental results while Cylinder 5 was applying load to the span was.42. Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam Strain, με Exp.-A FEM-A Exp.-B FEM-B Position, ft Figure Deflection comparison of the finite element model and experimental results for the west span while loaded by Cylinder 5 (A and B Lines)

133 133 Shown in Figure 6.6 is the comparison of the finite element deflection results to the experimental deflection results from the destructive testing of the west span. Similar to the previous results presented from the finite element model, the finite element model yielded results where the loaded beams exhibit larger magnitudes of deflection than the experiment results when the span was loaded by Cylinder 8. The deflection results from the finite element model for the beams away from the load were significantly closer to the deflections from the experimental testing. The average difference between the deflection results of the finite element model and the experimental results was.33 while the span was loaded by Cylinder 8. Beam 9 Beam 8 Beam 7 Beam 6 Beam 5 Beam 4 Beam 3 Beam 2 Beam Strain, με Exp.-A FEM-A Exp.-B FEM-B Position, ft Figure Deflection comparison of the finite element model and experimental results for the west span while loaded by Cylinder 8 (A and B Lines)

134 134 CHAPTER 7: CONCLUSIONS Once the testing and analysis procedures for the prestressed precast concrete adjacent box beam bridge were completed it was concluded that a system of adjacent box beams connected with transverse tie rods and shear keys can act as a system. The center span of FAY behaved at a system by distributing load throughout all of the beams of the span when only a few of the beams were loaded. This trend of load distribution transversely across the span was evident even when concentrated loads much larger than realistic loads the span would have be subjected to while in service. In order to obtain a system behavior from adjacent box beams, it is critical that the transverse tie rods and shear keys, designed to transfer load to adjacent beams are appropriately installed so the integrity of these elements are not compromised by deterioration. The west span of FAY was severely damaged to study the effects of damaged beams on the overall behavior of the span as a system. The testing of this span revealed that even with three severely damaged beams, the span was able to withstand loads much higher than would actually be applied to the span during service. When load was applied to the three damaged beams, the strain results demonstrated that load was still transferred to the adjacent beams. The strain results also indicated that the beams adjacent to those with damage carried more load than the loaded damaged beams. This behavior further emphasizes the importance of the transverse tie rods and shear keys. After the west span was loaded until it collapsed, a visual inspection was done on several of the transverse tie rods that were exposed from the collapse. These transverse ties rods

135 135 showed minimal to no corrosion after a 43-year service life (Figure 7.1). Several shear keys were also exposed when the bridge collapsed. These shear keys however, did not exhibit shear failure. The shear keys were and had debonded from the beams (Figure 7.2). Figure 7.1 Transverse tie rod exposed during west span collapse

136 136 Figure 7.2 Shear key exposed during west span collapse It has also been shown through the use of finite element modeling that the general behavior of prestressed concrete bridges can be accurately predicted. This means that additional bridges can be modeled as full-scale bridges without geometric simplifications using finite element modeling, given that actual material properties and the dimensions of the bridge are known. With the aid of finite element modeling useful information about the general bridge behavior can be achieved with less evasive testing procedures.

137 137 CHAPTER 8: RECOMMENDATIONS Now that it has been determined that the transverse tie rods play a vital role in adjacent box beams acting as a system, further research should be done to determine how the transverse tie rods themselves behave while in service. This study should entail instrumentation of the transverse tie rods to determine what kind of stresses the tie rods are experiencing under conventional loadings on the bridge. Installation techniques of transverse tie rods should also be explored. How the tie rods are installed will determine how they behave and how effectively load is transferred to adjacent beams. Proper installation is also important in preventing corrosion of the transverse tie rods. Since corrosion of adjacent box beam systems is an established problem encountered, how corrosion affects the performance of the transverse tie rods should be examined for tie rods with differing degrees of corrosion. With the advancement in computational technologies, creating full-scale models of existing reinforced concrete bridges using finite element modeling is achievable and has proved to be an accurate way to assess general bridge behavior and performance. Now that these technologies are available, finite element modeling should be used to evaluate additional bridges. One problem encountered during the destructive testing of the prestressed precast adjacent box beam bridge was that it was very difficult to measure the load being applied to each beam by the hydraulic cylinders. Alternative methods of loading and load measurement should be investigated. It was also difficult to measure a constant magnitude loading due to the creeping of the beams and load distribution behavior of the

138 bridge. This should be taken into account when attempting to study the behavior of beam systems. 138

139 139 References Balakrishnan, S., Elwi, A. E., & Murray, W. D. (1988, July). Effect of Modeling on NLFE Analysis of Concrete Structures. Journal of Structural Engineering, 114(7), Barzegar, F., & Maddipudi, S. (1997). Three-Dimensional Modeling of Concrete Structures. II: Reinforced Concrete. Journal of Structural Engineering, Camino Trujillo, S. J. (21). Analytical Evaluation of Damaged Prestressed Concrete Box Beams Bridge Girders. Masters Thesis, Ohio University, Russ College of Engineering and Technology. Dassault Systemes Simulia Corporation. (21) Defining Plasticity. In Abaqus/CAE User's Manual. Providence, Rhode Island, USA. Dassault Systemes Simulia Corporation. (21) Concrete Smeared Cracking. In Abaqus Analysis User's Manual. Providence, Rhode Island, USA. Gulistani, A. A. (21). Forensic Investigation of Prestressed Concrete Box Beams from LIC-31 Bridge. Masters Thesis, Ohio University, Russ College of Engineering and Technology. Harries, K. A., Gostautas, R., Earls, C. J., & Stull, C. (26). Full-scale Testing Program on De-commissioned Girders from the Lave View Drive Bridge. FHWA-PA-26-8-EMG1, University of Pittsburg, School of Engineering. Huckelbridge, A., El-Esnawi, H., & Moses, F. (1993). An Investigation of Load Transfer in Multi-Beam Prestressed ox Girder Bridges. Report No. FHWA/OH- 94-2, Case Western University, Department of Civil Engineering. Labia, Y., Saiidi, M. S., & Douglas, B. (1997, Sept-Oct). Full-Scale Testing and Analysis of 2-Year-old Pretensioned Concrete Box Girders. ACI Structural Journal, MacGregor, J. G., & Wright, J. K. (25). Reinforced Concrete (4 ed.). Upper Saddle River, New Jersey: Pearson Education Inc. Miller, R. A., Aktan, A. E., & Shahrooz, B. M. (1994). Destructive Testing of Decommissioned Concrete Slab Bridge. Journal of Structural Engineering, 12(7), Naito, C., Sause, R., Hodgson, I., Pessiki, S., & Desai, C. (26). Forensic Evaluation of Prestressed Box Beams from the Lake View Drive Bridge over I-7. Lehigh University. ODOT, O. D. (26). The Ohio Bridge Inventory. Ohio. Oh, B., Kim, K., & Lew, Y. (22, March-April). Ultimate Load Behavior of Post- Tensioned Prestressed Concrete Girder Bridge through In-Place Failure Test. ACI Structural Journal,

140 Russell, H. G. (211). Adjacent precast concrete box-beam bridges: State of practice. PCI Journal, Scanlon, A., & Mikhailovsky, L. (1987). Full-scale loac test of three span concrete highway bridge. Can. J. Civ. Eng., 14, Setty, C. J. (211). Truck Test of a 43-year-old Prestressed Concrete Adjacent Box Beam Bridge. Masters Thesis in Progress, Ohio University, Russ College of Engineering and Technology. Steinberg, E., & Miller, R. (211). Structural Evaluation of LIC Box Beams with Advanced Strand Deterioration. Interim Report - Phase I, Ohio University, Department of Civil Engineering. Zhang, J., Peng, H., & Cai, C. S. (211, March/April). Field Study of Ovlerload Behavior of an Existing Reinforced Concrete Bridge under Simulated Vehicle Loads. Journal of Bridge Engineering,

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