Test Results: HC Beam for the Knickerbocker Bridge AEWC Report Project 671 September 2009

Transcription

1 Test Results: HC Beam for the Knickerbocker Bridge September 2009 Submitted by: Thomas Snape Robert Lindyberg, Ph.D., P.E.

2 The AEWC Advanced Structures & Composites Center conducts all testing in accordance with strict standards of precision and accuracy. The following test methods performed for, HC Beam testing for Knickerbocker Bridge, are within AEWC s ISO accredited field of testing. Thus, the results of these tests are internationally recognized and accepted. ASTM D696 Standard Test Method for Coefficient of Linear Thermal Expansion of Plastics Between 30 C and 30 C with a Vitreous Silica Dilatometer. ASTM D790 Standard Test Methods for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials ASTM D2344 Standard Test Method for Short-Beam Strength of Polymer Matrix Composite Materials and Their Laminates ASTM D2584 Standard Test Method for Ignition Loss of Cured Reinforced Resins ASTM D3039 Standard Test Method for Tensile Properties of Polymer Matrix Composite Materials ASTM D4255 Standard Test Method for In-Plane Shear Properties of Polymer Matrix Composite Materials by the Rail Shear Method ASTM D6641 Standard Test Method for Determining the Compressive Properties of Polymer Matrix Composite Laminates Using a Combined Loading Compression (CLC) Test Fixture This test report is issued with the authority of: Thomas Snape, Research Engineer

3 Table of Contents 1. Background Test Program Full-Scale Structural Test of HC Beam Beam Fabrication & Setup Instrumentation Placement of Arch and Deck Concrete Test Description Structural Test Sequence: Coupon Test Description Durability Test Description Concrete Test Description Test Results Arch Pour Strains at Mid-span Strains in Composite Cross-Tie Spacers Mid-span Deflections Deck Pour Strains at Mid-span Mid-Span Deflections Initial Static Shear Test Optical Measurement of Web Shear Initial Static Bending Test Strains at Mid-span Mid-Span Deflection Bending Fatigue Test Static Bending Test with Full Factored Load Strains at Mid-Span Mid-Span Deflection Final Static Shear Tests Final Bending Test Load to Failure Coupon Test Results ASTM D696 Coefficient of Linear Thermal Expansion (CLTE) ASTM D790 Flexural properties under 3-point bending load ASTM D3039 Tensile properties ASTM D6641 Compressive properties under axial load ASTM D2584 Fiber fraction (ignition loss) ASTM D4255 In-plane shear properties Material Specifications Durability Test Results ASTM D790 Flexural properties under 3-point bending load ASTM D3039 Tensile Properties ASTM D2344 Short-beam strength ASTM D4255 In-plane shear properties Summary of Durability Study Results Concrete Test Results... 48

4 4 Conclusions Appendix A: Drawings for HC Beam superstructure in Knickerbocker Bridge Appendix B: Knickerbocker Bridge Test Beam Drawings Appendix C: Composite Cross-Tie Spacers and Spacer Test Appendix D: Mechanical Property Test Detail Appendix E: Special Provisions Document for Hybrid Composite Beam... 82

5 1. Background In 2009, the Maine Department of Transportation (MDOT) intends to begin replacement of the Knickerbocker Bridge, using the hybrid-composite HC Beam system, manufactured by Harbor Technologies of Brunswick, ME. The new Knickerbocker Bridge will be an eight span, 540 ft long bridge carrying the Barter s Island Rd. from the mainland to Hodgdon Island over an inlet of the Sheepscot River in the town of Boothbay, ME. The HC Beam technology consists of a fiber-reinforced polymer (FRP) shell that contains a hollow form for a parabolic arch and tension reinforcement (typically prestressing steel strand) on its bottom (tension) face. The FRP shell is fabricated with the tension steel in a controlled shop environment and then shipped to the bridge site where it is installed on its bearings. The hollow arch is then pumped full of a self-consolidating concrete (SCC) which hardens into the beam s compression reinforcement (Figure 1). ` Figure 1: Diagram of the HC Beam. Before it is installed in the Knickerbocker Bridge, MDOT requires that one HC Beam unit (with cast-in-place concrete deck) be laboratory tested to confirm its strength, stiffness, and durability. 2. Test Program The HC Beam test program for the Knickerbocker Bridge consists of three parts: 1. Full-scale test of an HC Beam unit. 2. Material-level coupon tests for the composite skins of the HC Beam 3. Material-level coupon tests for composite skins of the HC Beam subject to ultra-violet (UV) light exposure. AEWC Advanced Structures & Composites Center Page 1 of 95

6 2.1 Full-Scale Structural Test of HC Beam Figure 2 shows a typical cross-section of the proposed Knickerbocker Bridge. Figure 2: Typical cross-section of the proposed Knickerbocker Bridge. The laboratory test program for the HC Beam included fabricating one beam unit, setting it up in the AEWC Lab, filling the arch with concrete, and then casting a concrete deck (see Figure 3). Figure 3: Knickerbocker Bridge test beam cross-section. AEWC Advanced Structures & Composites Center Page 2 of 95

7 2.1.1 Beam Fabrication & Setup One (1) full-scale HC Beam test specimen was manufactured by Harbor Technologies, Inc to specifications for the 70 ft HC Beams to be used in the interior spans in the Knickerbocker Bridge (see test beam drawings, Appendix B). To facilitate test setup, both ends of the specimen were fabricated as per Detail 3 At Abutments shown in the Knickerbocker Bridge design drawings (Appendix A). Both sides of the test specimen contained the FRP Top Plate for Exterior Beams as shown in Section A-A on the same page of the drawings. AEWC received the HC Beam specimen (less concrete) from Harbor Technologies on February 9, Upon receipt, the beam was placed on the laboratory floor for installation of internal instrumentation. The beam was then shimmed to achieve specified camber of 4.4 in., and the beam cover was fastened on top of the beam with Plexus adhesive and screws. Steel shear connectors were positioned by AEWC personnel through holes pre-drilled in the cover by Harbor Technologies, under the direction of HC Bridge personnel. After the shear connectors were in place, AEWC placed the beam on 29 in. high concrete supports, supported over the full beam width and 12 in. bearing length on a 1 in. thick neoprene pad. The HC beam span was ft, c/c bearings. When placed, the beam deflected under its self-weight (empty weight 5000 lbs) approximately 1.15 in., bringing the camber to 3.25 in. before placement of the arch concrete. AEWC Advanced Structures & Composites Center Page 3 of 95

8 2.1.2 Instrumentation Table 1 lists the instrumentation placed on the HC Beam. Items 1-35 are strain gages; items are displacement gages (linearly-variable displacement transducers), and items are the load and position indicators for the Instron hydraulic actuator. Figure 4 is a diagram showing the placement of the instrumentation on the beam. Figure 4: Instrumentation locations AEWC Advanced Structures & Composites Center Page 4 of 95

9 Table 1: Instrumentation list for Knickerbocker Bridge Test Beam. ID: Application: Location Type 1 Tension Strand in bottom of beam At bearing C/L CEA W Tension Strand in bottom of beam 102.5" from brg C/L CEA W Tension Strand in bottom of beam 205" from brg C/L CEA W Tension Strand in bottom of beam 307.5" from brg C/L CEA W Tension Strand in bottom of beam At beam mid-span CEA W Transverse on top of foam spacer 30" from beam end CEA W Transverse on bottom of foam spacer 30" from beam end CEA W Transverse on top of foam spacer 17 ft from beam end CEA W Transverse on bottom of foam spacer 17 ft from beam end CEA W Tension strand in bottom of arch At end CEA N Tension strand in bottom of arch At quarter point CEA N Tension strand in bottom of arch At mid-span CEA N Tension strand in bottom of arch At quarter point CEA N Tension strand in bottom of arch At end CEA N Embedded in concrete at top of arch At end EGP Embedded in concrete at top of arch At quarter point EGP Embedded in concrete at top of arch At mid-span EGP Embedded in concrete at top of arch At quarter point EGP Embedded in concrete at top of arch At end EGP On shear connector First one at end CEA W On shear connector Fourth from end CEA W On shear connector Seventh from end CEA W On shear connector Seventh from end CEA W On shear connector Fourth from end CEA W On shear connector First one at end CEA W On concrete deck surface At quarter point N2A-06-20CBW On concrete deck surface At quarter point N2A-06-20CBW On concrete deck surface At mid-span N2A-06-20CBW On concrete deck surface At mid-span N2A-06-20CBW On concrete deck surface At quarter point N2A-06-20CBW On concrete deck surface At quarter point N2A-06-20CBW On beam frp web - top At mid-span CEA W On beam frp web - top At mid-span CEA W On beam frp web - bottom At mid-span CEA W On beam frp web - bottom At mid-span CEA W LVDT under beam At support 37 LVDT under beam At load span point 38 LVDT under beam At mid-span 39 LVDT under beam At load span point 40 LVDT under beam At support 41 Instron Load 42 Instron Position AEWC Advanced Structures & Composites Center Page 5 of 95

10 2.1.3 Placement of Arch and Deck Concrete On February 12, 2009, the arch cavity was filled with self-consolidating concrete (SCC) with a design compressive strength (fc ) of 6000 psi., following a concrete mix specification provided by HC Bridge and approved by the Maine Department of Transportation (MDOT). At the time of the concrete placement, eight concrete test cylinders were cast arch concrete. Strain measurement of the beam web due to the load of the wet concrete was measured at mid-span using the strain gages placed on and within the beam. In addition AEWC s Aramis 3D optical deformation measurement system was used to measure strain at mid-span, and deflections at mid-span were also measured. The arch concrete was allowed to cure before addition of the bridge deck. During the curing period, the rebar and formwork for the deck were placed. After tests on the arch concrete test cylinders confirmed that the arch concrete strength has reached at least 4000 psi, the concrete deck was poured and leveled on February 24, 2009 using a 4350 psi Class A concrete mix specification provided by HC Bridge and approved by MDOT. Eight concrete test cylinders were made from the deck concrete mix. After cylinder testing confirmed that both the arch concrete and deck concrete had reached their full design strength (6000 psi and 4350 psi, respectively) testing began Test Description The specified static design load is the Modified HL-93 Load (HL %) plus Impact, with live load distribution applied. In addition, superimposed dead loads must be applied. Beam selfweight and deck weight were adequately simulated by the test specimen (see Figure 2 and Figure 3). The three-axle, HL-93 truck is impractical to reproduce in the lab, especially for a cyclic load fatigue test. A 4-point static load test that will apply approximately the same bending moment profile as the specified test load was proposed for the static shear, static bending, and fatigue bending tests. Table 2 describes the moment and shear effects from the specified static design loads. Figure 5 shows the shear diagram for the recommended (4-point) static shear test load, compared to shear diagram for the specified (3-axle) static test load. Figure 6 shows the moment diagram for the recommended (4-point) static moment test load, compared to moment diagram for the specified (3-axle) static test load. Table 2: Static Test Loads (Recommended load in last row) for test beam with ft span. Load Description Max Shear 1 Max Moment HL-93 Truck Load (undistributed) 72 kip, 3-axle truck 58.6 kips kips-ft Modified HL-93 Truck (undistributed) 90 kip, 3-axle truck 73.3 kips k-ft HL-93 Lane Load k/ft lane loading 19.7 kips k-ft Modified HL-93 + Impact (33%) Modified Truck Load + Lane Load with 33% Impact applied to Truck Load only 117.1kips 1950 k-ft Distributed Live Load Lanes/Beam for Moment 0.52 Lanes/Beam for Shear 60.9 kips 698 k-ft Interior, 70 ft Girders Superimposed Dead Load Superimposed dead load: 221 lbs/ft Future wearing surface: 90 lbs/ft 10.1 kips 193 k-ft Water Main = 19 lbs/ft Total Static Design Load Excludes girder self-weight and deck dead 71 kips 891 k-ft 1 Max Shear at a distance d from centerline end support (d = total depth girder + deck). AEWC Advanced Structures & Composites Center Page 6 of 95

11 Load Description Max Shear 1 Max Moment Recommended Static Test Load for Bending Moment (Figure 6) Recommended Static Test Load for Shear (Figure 5) load, as the test specimen fully simulates these 4 point load centered at mid-span Load-span = 14 ft Two load points at 32.8 kips each Total load = 65.6 kips 4-point load, with one axle 3.4 ft inside end support. Load Span = 14 ft Two load points at 45 kips each Total Load = 90 kips 32.8 k 891 k-ft 76.3 kips k-ft After setup, instrumentation, and casting of the concrete arch and deck, the following tests were performed. 1) Initial Test (Shear): The beam was loaded to simulate the shear load and stresses induced in a single beam under the specified design load. A four-point loading configuration was used, with a total load of 90 kips (two 45 kip point loads), with a load span of 14 ft and one axle spaced 3.4 ft from the centerline of the end support (See Table 2 and Figure 5). During the static test, deflections and strains were recorded from initial pre-load to the full static test load. The shear strain was measured on an area of the side of the beam near one of the supports using an Aramis 3D optical deformation measurement system. 2) Initial Static Test (Moment): The beam was loaded to simulate the bending moment and stresses induced in a single beam by the specified design load. A four-point loading configuration was used, with a total load of 65.6 kips (two 32.8 kip point loads), centered at mid-span, with a load span of 14 ft (See Table 2 and Figure 6). During the static test, deflections and strains were recorded from initial pre-load to the full static test load. See Table 1 and Figure 5 for loads and moment diagrams. 3) Fatigue Test (Moment): Following the initial static test, the beam was loaded to simulate the cumulative effects of bending moment and stresses induced in a single beam for 2 million cycles of the specified fatigue design load. A four-point loading configuration was used with a load span of 22 ft centered at mid-span. The actuator applied minimum load of 16.6 kips (two 8.3 kip point loads), simulating superimposed dead load, and a maximum load of 41.4 kips (two 20.7 kip point loads) simulating the fatigue truck + superimposed dead load. At approximately 100,000 load-cycle intervals, the fatigue loading was paused, and the beam was loaded to the full static load, measuring deflections and strains. In this manner, potential cumulative damage caused by the fatigue loading will be tracked. See Table 3 and Figure 7 for the fatigue test loads. AEWC Advanced Structures & Composites Center Page 7 of 95

12 k 45 k 3.4 ft 14 ft ft Shear (kips) Total Static Design Load (Excluding Girder & Deck Self Weight) Recommended 4-point Load Distance Along Span (ft) Figure 5: Shear Diagram Comparison Table 3: Fatigue Test Load (Recommended load in last row) for test beam with ft span. Load Description Max Moment HL-93 Truck Load (undistributed) HL-93 + Impact (15%) Distributed Live Load C820Superimposed Dead Load Total Fatigue Design Load Recommended Fatigue Test Load for SDL Bending Moment (Figure 3) Recommended Fatigue Test Load for Total Fatigue Bending Moment (Figure 3) 72 kip, 3-axle truck Front axle spacing = 14 ft; Rear axle spacing = 30 ft Modified Truck Load + Lane Load with 33% Impact applied to Truck Load only Lanes/Beam for Moment Interior, 70 ft Girders Superimposed dead load: 221 lbs/ft Future wearing surface: 90 lbs/ft Water Main = 19 lbs/ft Excludes girder self-weight and deck dead load, as the test specimen fully simulates these 4 point load centered at mid-span Load-span = 22 ft Two load points at 8.3 kips each Total load = 16.6 kips 4 point load centered at mid-span Load-span = 22 ft Two load points at 20.7 kips each Total load = 41.4 kips kips-ft 798 k-ft 286 k-ft 193 k-ft 478 k-ft 193 k-ft k-ft 478 k-ft AEWC Advanced Structures & Composites Center Page 8 of 95

13 Moment Diagrams (Distributed LL + Impact) k 32.8 k ft ft 14 ft ft ft Moment (k-ft) Bending Moment from Specified Static Design Load (Distributed): HL % + Impact (33%) Recommended Static Test Load: 4- point with 32.8 k axle loads spaced 14 ft Distance Along Span (ft) Figure 6: Loads and moment diagram for bending static load Moment Diagrams (Distributed LL + Impact) min =8.3 k max = 20.7 k min =8.3 k max = 20.7 k ft 22 ft ft Moment (k-ft) Bending Moment Superimposed DL Recommended 4-point fatigue minimum load Bending Moment from HL-93 fatigue truck + Impact + SDL Recommended 4-point fatigue maximum load Distance Along Span (ft) Figure 7: Loads and moment diagram for bending fatigue load Structural Test Sequence: Following was the sequence for the structural tests of the HC Beam: AEWC Advanced Structures & Composites Center Page 9 of 95

14 1. Static shear test: 4-point bending using recommended static load (90 kip total) 2. Static moment test 4-point bending using recommended static load (65.6 kip total) 3. Fatigue test 4-point bending using recommended fatigue load (min = 16.6 kip total; max = 41.4 kip total) 4. Static moment tests using 60.5 kip load to be performed after every 100,000 cycles of fatigue loading to determine if any deterioration from fatigue loading is occurring. 5. Upon completion of 500,000 fatigue cycles, a draft report summarizing the test results to date will be submitted to MDOT. 6. At the completion of 2 million fatigue cycles, a final 4-point static test will be performed to load the beam to failure, or up to 280,000 lbs, which ever occurs first. 2.2 Coupon Test Description Harbor Technologies provided two samples of flat laminate material. One panel represented the laminate used in the sides, or web, of the beam shell. The other panel represented the laminate used in the beam cover. Each witness panel was laid up and infused at the same time as the corresponding beam parts, using the same resin batches. The following tests were performed in the AEWC mechanical testing laboratory on specimens prepared from the witness panels: ASTM D696 Coefficient of linear thermal expansion (0 and 90 ) ASTM D790 Flexural properties under 3-point bending load (0 and 90 ) ASTM D3039 Tensile properties under axial load (0 and 90 ) ASTM D6641 Compressive properties under axial load (0 and 90 ) ASTM D2584 Fiber fraction (ignition loss) ASTM D4255 In-plane shear properties of polymer matrix composite materials 2.3 Durability Test Description Exposure to sunlight and moisture is known to have degrading effects on the mechanical properties of vinyl ester resin based composites. Ultraviolet (UV) radiation from direct sunlight is potentially the most damaging environmental element to the resin (Signor, Chin). To offset these effects, the resin used to manufacture the FRP shell of the HC Beams for the Knickerbocker Bridge will contain a UV inhibitor additive, as well as an opaque pigment. A durability test was performed to investigate the effectiveness of these protective measures. Two (2) 24 in. x 24 in. test panels (with a layup matching the web of the HC Beam) containing the UV inhibitor and pigment were fabricated by Harbor Technologies and shipped to AEWC for accelerated weathering durability testing. The panels were arbitrarily identified as Panel 1 and Panel 2. Principal direction was not indicated on either panel. Each panel was cut in half along an arbitrarily chosen orthogonal axis. One half of each panel was placed in a QUV accelerated weathering tester (see Figure 8). The QUV uses alternating cycles of UV and moisture to simulate the effects of sunlight, rain, and dew. The UV exposure is achieved using UVA 340 lamps. These lamps produce a spectrum of long wave UV light in a distribution with a mode of 343 nm wavelength. This closely approximates the UV radiation coming from exposure to direct AEWC Advanced Structures & Composites Center Page 10 of 95

15 sunlight (see Figure 9). The moisture cycles are done with the lamps off, and achieved by creating a high humidity and high temperature atmosphere on the test surface of the specimens. The back sides of the specimens are exposed to the room atmosphere. This results in condensation of the humidity on the test surfaces. Figure 8: QUV accelerated weathering testers at AEWC Figure 9: Spectral power distributions of UVA-340 llamp and sunlight The accelerated weathering treatment was conducted in two steps: 1. The samples were first exposed to 169 hours of constant UV 83%, 65 C. 2. The samples were next subjected to12 hour cycles consisting of 4 hours condensing 50 C and 8 hours UV 60 C. This treatment cycle is the same as Cycle 1 listed in Table X2.1 Common Exposure Conditions of ASTM G154. AEWC Advanced Structures & Composites Center Page 11 of 95

16 The sample from Panel 1 was removed after 1000 hours of the second treatment step. The sample from Panel 2 was removed after 2361 hours of the second treatment step. The unexposed halves of both panels were stored at room temperature and relative humidity, out of direct light. These samples did not receive any treatment, other than the aging, from time of manufacture to time of testing. Specimens were prepared from each half of Panel 1 and Panel 2 to perform mechanical property testing of the laminate. Within a panel, specimens from both halves were cut aligned to the same orthogonal direction. However it is not known if the chosen direction is aligned with the principal direction of the glass reinforcement in the laminate. The following mechanical tests were performed on the specimens prepared from the durability test panels: ASTM D790 Flexural properties under 3-point bending load ASTM D3039 Tensile properties under axial load ASTM D2344 Short-beam strength of polymer matrix composite materials and their laminates ASTM D4255 In-plane shear properties of polymer matrix composite materials 2.4 Concrete Test Description Eight 6 diameter test cylinders each were cast from the concrete batches used to fill the beam arch and cast the deck. Compressive strengths of the specimens were determined following ASTM C39. Compressive modulus was determined following ASTM C Test Results 3.1 Arch Pour Strains at Mid-span Figure 10 shows the strains measured at the mid-span of the HC Beam under the full fluid weight of the SCC arch concrete (approximately 125 lbs/ft distributed load). This data shows that the neutral axis of the HC beam is approximately 5.59 in. above the extreme bottom fiber. Calculations by John Hillman of Teng Associates place the estimate the neutral axis at 7.67 in. above the extreme bottom fiber. There are likely two explanations for this difference: 1. The horizontal wings and top plate at the top of the HC Beam unit were not continuous along the length. Splice plates were used to connect these sections, but these were not effective in transferring load along the top plate and wings longitudinally from one section to another. Load transfer was finally achieved when the beam deflected enough that the sections came into direct, compressive contact. 2. The top plate of the HC Beam experienced a considerable amount of elastic buckling, due to its low flexural stiffness and the high compressive load on this section. In future beams, this top plate will need to be stiffened considerably, as this type of elastic buckling could potentially result in beam instability and failure under the fluid load of the arch concrete. AEWC Advanced Structures & Composites Center Page 12 of 95

17 3.1.2 Strains in Composite Cross-Tie Spacers Strain gages were placed on the composite cross-tie spacers that were designed to restrain the webs of the HC Beam against the fluid load of concrete (see Appendix C). Two of these crossties were instrumented on their top and bottom tie (see diagram of cross-tie design, Appendix C), and strains were recorded throughout the concrete pour (Figure 11). Strains ranged from to for the tie nearest the support (& under the greatest fluid load), and as high as for the tie 17 ft from the support. Strains appeared to fluctuate significantly under the positive pressure of the pumping concrete. While further analysis is required to determine the actual load experienced by the cross-ties during the arch concrete pour, it is clear that they were under significant load and provided restraint that prevented the beam webs from expanding outward under the fluid pressure of the concrete Mid-span Deflections During the arch concrete pour, mid-span deflection was measured using a linearly-variable displacement transducer. After the full load of concrete was pumped, and all equipment was removed, the measured mid-span deflection was 1.68 in. under the 125 lb/ft fluid load of the arch concrete. The deflection estimated in the design calculations was 2.65 in., but this did not consider the stiffness contribution of the wings on the top of the beam. With the full contribution of the wings, the calculated mid-span deflection is 1.52 in., which is about 10% less than the measured deflection. The reason for this is likely due to the local buckling in the beam top plate and the limited continuity of the top plate and wings as described above. Figure 10: Mid-span strains in HC Beam under fluid load of arch concrete. AEWC Advanced Structures & Composites Center Page 13 of 95

18 :24 AM 11:57 AM 12:31 PM 1:04 PM 1:37 PM 2:11 PM 2:44 PM Strain Cross-tie top: 30 in. from support Cross-tie bottom: 30 in. from support Cross-tie top: 17 ft. from support Cross-tie bottom: 17 ft. from support Time Figure 11: Strains measured in cross-ties during arch concrete placement. Following the arch concrete pour, mid-span deflection data was gathered for the next four days. A plot of this data is shown in Figure 12. Immediately following the arch pour, the initial midspan deflection stabilized at approximately 1.68 in.. Approximately 6 hours after the pour, midspan deflections began to decrease, eventually rebounding to 1.15 in. 16 hours after the pour. It is unlikely that this phenomenon is due to water evaporation, as the concrete mix was entirely contained within the beam, with little exposure to the air. Rather, the initial decrease in midspan deflections appears to be the result of an initial expansion of the concrete at the beginning of its cure cycle. Approximately 16 hours after the pour, beam deflections began to increase again, eventually surpassing the initial deflection of 1.68 in. Ninety-four hours after the pour, the rate of deflection change had stabilized, although the mid-span deflection at this time was in. This was likely due to concrete shrinkage, which caused the HC Beam to deflect due to the fact the majority of the concrete is above the neutral axis in the compression region of the beam. AEWC Advanced Structures & Composites Center Page 14 of 95

19 Mid-span Deflection for HC Bridge - Knickerbocker Bridge Beam Deflection due to pouring of arch concrete Time (hr) Deflection is relative to empty beam before pouring arch concrete (Time =0) Arch concrete pouring started 11:25 AM on 2/12/2009 and was completed in about 30 minutes. Mid-span deflection measure using LVDT attached to bottom surface of beam. Deflection (in) Figure 12: Mid-span deflection under fluid load of arch concrete (hours after pour). 3.2 Deck Pour Strains at Mid-span Figure 13: Mid-span strains in HC Beam under fluid load of deck concrete. Figure 13 shows the strains measured at the mid-span of the HC Beam and concrete arch under the full fluid weight of the deck concrete (350 lbs/ft distributed load). The data shows that the neutral axis of the beam is approximately in. above the extreme bottom fiber of the beam. AEWC Advanced Structures & Composites Center Page 15 of 95

20 Calculations by John Hillman of Teng Associates place the estimate the neutral axis at in. above the extreme bottom fiber. The likely reason for the difference is that the arch concrete was not fully cured at the time of the deck pourand had not reached its full modulus of elasticity Mid-Span Deflections During the deck concrete pour, mid-span deflection was measured using a linearly-variable displacement transducer. After the full load of concrete was pumped, and the equipment was removed, the measured mid-span deflection was 1.44 in. under the 350 lb/ft fluid load of the deck concrete. The deflection estimated in the design calculations was 1.75 in. Following the deck concrete pour, mid-span deflection data was gathered for the next three days. A plot of this data is shown in Figure 14. Over the 72 hours following the arch pour, the initial mid-span deflection stabilized at approximately 1.44 in. immediately after the pour. Approximately 6 hours after the pour, mid-span deflections began to decrease, eventually rebounding to 1.03 in. 14 hours after the pour. At this time, beam deflections began to increase again, eventually surpassing the initial deflection of 1.44 in. Seventy-seven hours after the pour, the rate of deflection change had stabilized, although the mid-span deflection at this time was 1.8 in. Similar to the arch concrete pour, this was likely due to concrete shrinkage. Mid-span Deflection HC Bridge - Knickerbocker Bridge Beam Deflection due to pouring of deck concrete Deflection (in) Time (hrs) Deflection is relative to beam before pouring deck concrete (Time =0) Deck concrete pouring started 10:30 AM on 2/24/2009 and was completed in about 40 minutes. Mid-span deflection measure using LVDT attached to bottom surface of beam Figure 14: Mid-span deflection under fluid load of deck concrete (hours after pour). 3.3 Initial Static Shear Test On March 11, 2009, the initial static shear test was performed. The beam was loaded under the configuration shown in Figure 5, page 8, with deflections measured and the support face, 1/3 span, and mid-span, and strains measured in the steel shear connectors (4 th connector from the AEWC Advanced Structures & Composites Center Page 16 of 95

21 end and the 7 th connector from the end). Figure 15 shows the load-deflection plot, and Figure 16 shows the load-shear connector strain plot. Both figures show the loading and unloading cycles, indicating final deflections and strains following the completion of the test. Load (lbs) 105, ,000 95,000 90,000 85,000 80,000 75,000 70,000 65,000 60,000 55,000 50,000 45,000 40,000 35,000 30,000 25,000 20,000 15,000 10,000 5, in. from centerline support 1/3 span from centerline support Midspan Final Deflections End: in. 1/3 span: in. Midspan: in Displacement (in.) Figure 15: Load vs. deflection under static shear test (see test configuration: Figure 5, page 8). AEWC Advanced Structures & Composites Center Page 17 of 95

22 Load (lbs) Shear Connector - 4th from end Shear Connector - 7th from end Final Strains 4th connector from end: th connector from end: Strain (in/in) Figure 16: Load vs. strain in shear connectors under static shear test (see test configuration: Figure 5, page 8). The data from the static shear test shows that the HC beam carried a load of nearly 100,000 lbs, producing a shear of approximately 85 kip (20% higher than the design shear see Table 2, page 5) without permanent deflection or strain in its most highly-stressed shear connectors. Beam behavior was essentially linear throughout the test Optical Measurement of Web Shear Deformation of the side of the beam during the shear load test was measured using an Aramis 3D Optical Deformation Measurement System. The center of the 12 by 12 measurement area was located 22" inboard of bearing centerline. The Aramis strain data was analyzed, and a load vs. maximum strain plot is shown in Figure 15. AEWC Advanced Structures & Composites Center Page 18 of 95

23 100,000 90,000 Load vs. Shear Strain HCB Knickerbocker Bridge Beam Shear Load Test - March 11, ,000 70,000 60,000 Load (lb) 50,000 40,000 30,000 20,000 10, Shear Strain (Engineering strain, deg) Figure 17: Load vs. shear strain results from Aramis optical measurement 3.4 Initial Static Bending Test Immediately following the static shear test, the load beam and hydraulic actuator were reconfigured for the bending static test, as shown in Figure 6, page 9. The beam was loaded to 65.6 kips, with deflections and beams strains measured throughout the test Strains at Mid-span Figure 18 shows the strains measured at the mid-span of the HC Beam under the initial static bending load of 65.6 kips. AEWC Advanced Structures & Composites Center Page 19 of 95

24 Figure 18: Strains measured at mid-span under initial static load of 65.6 kips (see load configuration Figure 6, page 9) The data in Figure 18 shows that the neutral axis of the beam is approximately in. above the extreme bottom fiber of the beam. This is in good agreement with calculations by John Hillman of Teng Associates, which place the neutral axis at 31.4 in. above the extreme bottom fiber Mid-Span Deflection Figure 19 shows the load-deflection plot generated from the initial static bending test. The plot shows linear behavior from initial load to the maximum load of 65.6 kips, with a maximum deflection of approximately 3.1 in. at mid-span. The apparent flexural stiffness (EI) of the beam was calculated using the following equation: 2 2 P b(3l 4b ) EI = yms 48 Where: P = slope of the load / mid-span deflection plot y MS l = support span b = horizontal distance from a support to nearest load point AEWC Advanced Structures & Composites Center Page 20 of 95

25 For the initial static bending test, the slope of the load/deflection plot was 21,315 lb/in. The support span (l) was 820.5, and the support to load point distance (b) was The calculated flexural stiffness (EI) for the beam is 2.31x10 11 lb-in Load (lb) Initial Bending Test Deflection (in) Figure 19: Load vs. mid-span deflection under initial static bending test (see load configuration Figure 6, page 9). 3.5 Bending Fatigue Test Following the initial static bending test, the load-span of the beam was reconfigured into the bending fatigue test configuration (see Figure 7, page 9), and cyclic testing began with a maximum load of 41.4 kips, and a minimum load of 16.6 kips, simulating the moment produced by an AASHTO HL-93 fatigue load truck. The load cycling rate was set at 1 Hz. Periodically the cyclic loading was stopped and the test was reconfigured into the static bending test configuration (see Figure 6, page 9) and the static bending test was repeated to a load of 65.6 kips. Fatigue load cycling was stopped after 2,000,000 cycles. Figure 20 shows the mid-span strain data for the initial bending test plotted with the data from the bending test performed after 2,000,000 cycles. Figure 21 shows the load-deflection data plotted for all the tests. The results from the individual tests were so alike that the plots in Figure 21 are not discernable from one another. AEWC Advanced Structures & Composites Center Page 21 of 95

26 Table 4 contains the flexural stiffness (EI) calculated from the load-deflection data for each of the tests. As seen from the data, there were no significant changes in strains through the mid-span or in flexural stiffness after 2,000,000 load cycles. Figure 20: Strains measured at mid-span under initial static load of 65.6 kips, and following 2,000,000 fatigue load cycles (see load configuration Figure 6, page 9) AEWC Advanced Structures & Composites Center Page 22 of 95

27 Load (lb) Initial Bending Test After 99,000 fatigue cycles After 202,000 fatigue cycles After 291,000 fatigue cycles After 427,000 fatigue cycles After 509,000 fatigue cycles After 600,000 fatigue cycles After 826,000 fatigue cycles After 1,000,000 fatigue cycles After 1,109,000 fatigue cycles After 1,429,000 fatigue cycles After 1,622,000 fatigue cycles After 1,789,000 fatigue cycles After 2,005,000 fatigue cycles Deflection (in) Figure 21: Load vs. mid-span deflection for all static bending tests under load of 65.6 kips (see load configuration Figure 6, page 9) Table 4: Apparent stiffness calculated from bending tests Fatigue load cycles completed Apparent stiffness (EI) Cycles (lb-in2) Initial 2.31E+11 99, E , E , E , E , E , E , E+11 1,000, E+11 1,109, E+11 1,429, E+11 1,622, E+11 1,789, E+11 2,005, E+11 AEWC Advanced Structures & Composites Center Page 23 of 95

28 3.6 Static Bending Test with Full Factored Load On April 14 the last fully instrumented static bending test was performed. The loading configuration was the same as for the initial static bending load test (see Figure 6, page 9) except that the full factored load of 133 kips was applied. The photo in Figure 22 was taken during the test Strains at Mid-Span Figure 22: Setup for static bending test with full factored load The mid-span strains measured during bending at the 133 kip load are shown in Figure 23. AEWC Advanced Structures & Composites Center Page 24 of 95

29 Figure 23: Strains measured at mid-span under static bending load of 133 kips Mid-Span Deflection Figure 24 shows a plot of the load vs. deflection at mid-span. This plot shows the loading and unloading cycles. The flexural stiffness (EI) for the beam was calculated for this test data over the load range of kips and found to be 2.33x1011 lb-in2. This load range was selected for the EI calculation so that the result can be compared to those found for the previous static bending tests which were loaded to 65.5 kips, and which are contained in Table 4. AEWC Advanced Structures & Composites Center Page 25 of 95

30 140, , , , ,000 90,000 Load (lb) 80,000 70,000 60,000 50,000 40,000 30,000 20,000 10, Deflection (in) Figure 24: Load vs. Deflection for static bending with full factored load of 133 kips 3.7 Final Static Shear Tests On April 14 the final static shear tests were performed. Two tests were performed. The loading configuration for both tests was the same as for the initial shear load test (see Figure 5, page 8) except different loads were applied. For the first test the full factored load of 135 kips was applied. Figure 25 shows the load vs. deflection measured on the half of beam under the shear load. Figure 25 shows the load-deflection plot, and Figure 26 shows the load-shear connector strain plot. Both figures show the loading and unloading cycles. After the shear load test to 135 kips was completed, the deflection measurement instrumentation was removed to perform a final static shear load test to the maximum capacity of the test actuator. The load for this test reached kips without any visible failure of the beam. AEWC Advanced Structures & Composites Center Page 26 of 95

31 140, , , , ,000 90,000 Load (lb) 80,000 70,000 60,000 50,000 40,000 30,000 20,000 10,000 7" from centerline support 1/3 span from centerline support Mid-span Displacement (in) Figure 25: Load vs. deflection under static shear test load of 135 kips AEWC Advanced Structures & Composites Center Page 27 of 95

32 140, , , , ,000 90,000 Load (lb) 80,000 70,000 60,000 50,000 40,000 30,000 20,000 10,000 Shear Connector - 4th from end Shear Connector - 7th from end Strain (in/in) Figure 26: Load vs. Strain for full factored shear load test 3.8 Final Bending Test Load to Failure Following the final static shear load tests, the loading arrangement was reconfigured to the static bending load arrangement for a final static bending test with the intent to fail the beam if possible. Deflection instrumentation was not connected during this test. The beam held a load of 209 kips before failure. Figure 27 shows a plot of the load vs. actuator displacement during the test. This actuator displacement is not a true measure of the beam deflection but the plot provides some insight into how the beam carried the load up to failure. Failure occurred when the anchoring of the tension reinforcement broke free in the south end of the beam. AEWC Advanced Structures & Composites Center Page 28 of 95

33 250, , ,000 Load (lb) 100,000 50, Actuator Displacement (in) Figure 27: Load vs. actuator displacement during the final bending test - loaded to failure AEWC Advanced Structures & Composites Center Page 29 of 95

34 Figure 28: Failed anchoring of tension reinforcement 3.9 Coupon Test Results Table 5 contains a list of the equipment used for the mechanical property tests of the panels representing the beam web and cover laminates. The equipment is identified by AEWC equipment ID numbers, and the dates that the tests were performed are included. Table 5: Test dates and equipment list for coupon tests Test method ASTM D790 ASTM D3039 ASTM D2344 ASTM D4255 Property type Flexural Tension Short Beam In-plane shear Date 6/3/2009 5/22/2009 5/26/2009 6/9/2009 Test machine Load cell Test fixture Caliper Micrometer Other Aramis 395 Aramis The following sections contain descriptions of how the tests were performed and summaries of the results. Full tables containing all test data are contained in Appendix D. AEWC Advanced Structures & Composites Center Page 30 of 95

35 3.9.1 ASTM D696 Coefficient of Linear Thermal Expansion (CLTE) The coefficients of linear thermal expansion for the cover and web laminates were determined following ASTM D696 Standard Test Method for Coefficient of Linear Thermal Expansion of Plastics Between 30 C and 30 C with a Vitreous Silica Dilatometer. The dilatometer used for this procedure consists of two concentric fused-quartz tubes. The outer tube has one closed end and is mounted vertically in a holding fixture, open end up. The specimen is placed in the bottom of the outer tube. The inner tube, which is closed on both ends, is placed inside the outer tube, capturing the specimen between the ends of the tubes. A digital indicator is mounted on the holding fixture and measures the position of the top of the inner tuber relative to the outer tube. Temperature changes are applied to the specimen by immersing the lower ends of the tubes in cooling or warming baths (nominally -30 C and +30 C, respectively). The apparatus is first placed in the cooling bath and the digital indicator reading recorded after the specimen has come to temperature equilibrium (determined by no change in the indicator reading). Following that, the apparatus is placed in the warming bath. After the specimen has come to temperature equilibrium, the indicator reading is recorded. The apparatus is again placed in the cooling bath and the measurement is repeated. The coefficient of linear thermal expansion (α) over the temperature range used is calculated as: α = ΔL L ΔT 0 Where: α = average coefficient of linear thermal expansion per degree Celsius ΔL = Change in length of test specimen due to hearing or to cooling L 0 = length of test specimen at room temperature ΔT = temperature difference, C, over which the change in length of specimen is measured α is calculated for the heating cycle and again for the cooling cycle. The average of these values is the CLTE that is reported for a given specimen. The test specimens were ½-inch wide and 2.5- inches long. Table 6 lists the results of the CLTE test results obtained for the beam cover and web laminates. Table 6: ASTM D696 CLTE Test Results Material Specimen CLTE / C Cover - 0 Test E-05 Test E-05 Average 1.13E-05 Cover - 90 Test E-05 Test E-06 Average 1.04E-05 AEWC Advanced Structures & Composites Center Page 31 of 95

36 Web - 0 Test E-05 Test E-05 Average 1.16E-05 Web - 90 Test E-05 Test E-05 Average 1.78E ASTM D790 Flexural properties under 3-point bending load The flexural properties of the cover and web laminates were determined following ASTM D790 Standard Test Methods for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials. The test performed was a three-point bending test. Figure 29 shows a typical equipment setup to perform D790 bending. Specimens were placed in the fixture with the tool side of the laminate down on the supports. Load was applied at a constant crosshead speed. The span between the supports and the rate of load application are calculated as functions of the specimen thickness. Load and crosshead displacement data were recorded continuously during the tests. The crosshead displacement recorded during the test was used to determine the specimen deflection. The maximum load that each specimen carried before it failed was used to calculate the maximum bending stress, which is reported as the flexural strength. The maximum bending stress was calculated as follows: 3PL σ b = 2 2bd Where: σ b = stress in outer fibers at mid-span (psi) P = maximum load carried by specimen (lb) L = support span (in) b = specimen width (in) d = specimen depth (thickness in) The flexural modulus of elasticity (MOE) was calculated from the slope of the load vs. deflection relationship. The slope was obtained from the initial portion of each test where the specimen exhibits elastic response to the load. For the results reported here, this slope was taken over the range from zero deflection, up to approximately 10% of ultimate deflection. The flexural MOE was calculated using this equation: 3 L m E B = 3 4bd Where: E B = modulus of elasticity in bending (psi) L = support span (in) AEWC Advanced Structures & Composites Center Page 32 of 95

37 b = specimen width (in) d = specimen depth (thickness in) m = slope of the initial straight-line portion of the load-deflection curve (lb/in) Table 7 contains a summary of the flexural test results and test conditions for the beam cover and web laminates. Figure 29: ASTM D790 test arrangement AEWC Advanced Structures & Composites Center Page 33 of 95

38 Table 7: ASTM D790 Flexural Properties Test Results Specimens Flexural Strength Flexural MOE Thickness Number of specimens Support Span Loading Rate (ksi) (Msi) (in) (in) (in/min) Cover - 0 Average Std. Dev COV 17.8% 5.8% 1.6% Cover - 90 Average Std. Dev COV 9.9% 8.6% 1.7% Web - 0 Average Std. Dev COV 7.1% 13.3% 3.0% Web - 90 Average Std. Dev COV 3.9% 8.7% 1.3% ASTM D3039 Tensile properties The tensile properties of the cover and web laminates were determined following ASTM D3039 Standard Test Method for Tensile Properties of Polymer Matrix Composite Materials. The standard D3039 tensile specimens of 10 long x 1 were prepared for this test. To perform the tests, 2 of each end of the specimens were clamped in the hydraulic grips of the Instron machine, leaving a 6 gauge section. The tensile load was applied at a constant crosshead speed. The strains over the gauge section during the tests were measured using the Aramis system as the axial tensile loads were applied. The ultimate tensile strength (UTS) for each test was calculated at the maximum load the specimen held before failing, divided by the average cross-sectional area of the gauge section. σ = UTS P MAX A Where: σ UTS = ultimate tensile strength P MAX = maximum load A = average cross-sectional area of specimen at gauge section AEWC Advanced Structures & Composites Center Page 34 of 95

39 The strain data collected by the Aramis system was used to plot the stress vs. strain relationship for each test. The tensile modulus of elasticity (MOE) for each test was computed as the slope of the stress-strain plot over the strain range of in/in to in/in. Δσ E = Δε Where: E = tensile modulus of elasticity (MOE) Δσ = difference in applied tensile stress over the range of strain Δε = the range of strain (in this case nominally 0.002) Table 8 contains a summary of the tensile test results and test conditions for the beam cover and web laminates. Table 8: ASTM D3093 Tensile Properties Test Results Specimen UTS MOE Thickness Number of specimens Loading Rate (ksi) (Msi) (in) (in/min) Cover - 0 Average Std. Dev COV 3.3% 3.6% 2.7% Cover - 90 Average Std. Dev COV 8.0% 3.2% 2.2% Web - 0 Average Std. Dev COV 2.2% 3.7% 2.2% Web - 90 Average Std. Dev COV 1.8% 2.2% 1.8% ASTM D6641 Compressive properties under axial load The compressive strengths of the cover and web laminates were determined following ASTM D6641 Standard Test Method for Determining the Compressive Properties of Polymer Matrix Composite Laminates Using a Combined Loading Compression (CLC) Test Fixture. The test for compressive properties was performed using a combined loading compression (CLC) test fixture (see Figure 30). Using this method, the compressive force is applied to the AEWC Advanced Structures & Composites Center Page 35 of 95

40 specimen by a combination of end loading and shear loading. The gauge length where the compression failure is expected to occur is defined by the gap between the upper and lower sets of clamping blocks. The test specimens prepared for this test were ½ wide and 5.5 long. The gauge length was ½. The compressive load was applied by the Instron machine using a constant crosshead speed until the specimen failure. The failure areas were examined to verify that a proper compression failure occurred, otherwise the test data would not be used. The compressive strength is calculated from the maximum load that the specimen holds before failure, according to the following equation: σ = UCS P MAX A Where: σ UCS = ultimate compressive strength P MAX = maximum compressive load A = cross-sectional area of specimen at gauge section Figure 30: ASTM D6641 Combined loading compression (CLC) test fixture Table 9 contains a summary of the compressive test results and test conditions for the beam cover and web laminates. AEWC Advanced Structures & Composites Center Page 36 of 95

41 Table 9: ASTM D6641 Compressive Strength Test Results Specimen Thickness Compressive Strength Number of specimens Loading Rate Avg. (in) (ksi) (in/min) Cover - 0 Average Std. Dev COV 2.8% 6.6% Cover - 90 Average Std. Dev COV 2.0% 8.7% Web - 0 Average Std. Dev COV 2.9% 3.1% Web - 90 Average Std. Dev COV 2.5% 6.0% ASTM D2584 Fiber fraction (ignition loss) The fiber mass fractions of the cover and web laminates were determined following ASTM D2584 Standard Test Method for Ignition Loss of Cured Reinforced Resins. The test results are summarized in Table 10. The fiber fraction of the laminates was determined by preparing 1 x 1 square specimens of the samples. The specimens were weighed to g and then placed in a muffle furnace at 565 C. After the resin was completely burned, the residue from the specimens was cooled to room temperature in a desiccator and then weighed. For laminates of glass reinforcement and organic resins, the weight of the residue can be considered to be the weight of the glass. The fiber fraction is then calculated as follows: Weight of residue Fiber Fraction (%) = x 100 Weight of specimen AEWC Advanced Structures & Composites Center Page 37 of 95

42 Table 10: ASTM D2584 Fiber Fraction Test Results Specimen Fiber Fraction (%) Cover 1 cover 79.9% 2 cover 79.0% 3 cover 78.7% Average 79.2% Std. Dev 0.63% COV 0.79% Web 4 web 64.0% 5 web 63.8% 6 web 63.9% Average 63.9% Std. Dev 0.09% COV 0.14% ASTM D4255 In-plane shear properties The in-plane shear properties of the cover and web laminates were tested following Procedure B of ASTM D4255 Standard Test Method for In-Plane Shear Properties of Polymer Matrix Composite Materials by the Rail Shear Method. Procedure B of ASTM D4255 is performed using a three-rail shear fixture (see Figure 31). The specimen is prepared as a 5.5 W x 6 H rectangle with nine holes positioned to allow passage of the threaded fasteners of the fixture. The threaded fasteners are torqued nearly to their yield point, clamping the specimen between the vertical rails of the fixture. The outer two rails are fixed to the base of the fixture. The Instron test machine applies load to the center rail which loads the specimen in in-plane shear in the spaces between the middle and outer rails.. Figure 31: ASTM D4255 Three-rail shear specimen and fixture with specimen mounted AEWC Advanced Structures & Composites Center Page 38 of 95

43 The specimens were all loaded to failure. In order to be able to determine the in-plane shear strength of the laminate, it is necessary for the laminate to fail in shear. For all of the beam web and cover specimens tested (as well as for the durability test specimens), the failure mode was not in-plane shear. Instead, the specimens slipped between the rails and failed in bearing against the fasteners of the fixture. This problem often occurs when the laminates contain off-axis reinforcement. In this case, both the web and cover laminates contain plus and minus 45 fibers. Although the ultimate shear strength of these laminates was not determined by these tests, we know that the specimens held the applied load in shear at least to the point that they began to slip in the fixture. The load at which this occurred for each specimen was estimated by careful examination of the load-displacement plots shown in Figure 32. These load values ranged from 10,500 lb to 15,600 lb. The shear stress at these loads was calculated using this equation: P τ = 2A Where: τ = in-plane shear stress P = load applied to middle rail A = cross sectional area of specimen between rails It must be emphasized the shear stress values that are reported are not mechanical properties of the laminates. They are only an estimate of the shear stress the laminate was under before the specimen started to slip. It is felt that the true ultimate shear strengths are much higher based upon the plots shown in Figure 32. AEWC Advanced Structures & Composites Center Page 39 of 95

44 30,000 25,000 20,000 Load (lb) 15,000 10,000 5,000 Cover-01 Cover-02 Cover-03 Web-01 Web-02 Web Acutuator Displacement (in) Figure 32: Load vs. displacement plots from D4255 tests for beam cover and web specimens An Aramis system was used to record the strain data during the D4255 tests. Each specimen had two areas which are placed in shear loading. Figure 33 shows a typical example of the shear strain that Aramis computed during one of the tests. The magnitudes of the strains determined on each side of the middle rail are averaged to obtain the test result. The test data combined with Aramis analysis provided a relationship between stress and strain for each specimen. The shear modulus for each test was determined over the strain range of to , and was determined to be the slope of the stress-strain plot over this range. The equation is as follows: Δτ G = Δγ Where: G = shear modulus of elasticity Δτ = difference in applied shear stress over the range of strain Δγ = the range of strain (in this case nominally 0.004) AEWC Advanced Structures & Composites Center Page 40 of 95

45 Figure 33: Aramis visualization of shear strain during ASTM D4255 test The results from the in-plane shear load tests for the beam cover and web laminates are contained in Table Material Specifications Table 11: ASTM D4255 Shear Properties Test Results Shear Stress at point specimen slipped in fixture Shear Modulus Specimen (psi) (Msi) Cover_01 10,433 (No data) Cover_02 9, Cover_03 8, Average 9, Web_01 8, Web_02 7, Web_03 5, Average 6, Std. Dev COV 9.2% Material specifications for the FRP shell of the hybrid-composite beam where included in the Special Provisions document for the Knickerbocker Bridge replacement (Appendix E). Table 12 contains a list of the mechanical properties that were in the specifications and that were included in the test program. All of the material specifications listed in the Special Provisions are listed as minimum values. The test results listed in Table 12 are the means of the values obtained from mechanical testing. Note that the specification for the coefficient of thermal expansion was AEWC Advanced Structures & Composites Center Page 41 of 95

46 listed as 9.0 x 10 6 in/in/ F; this is believed to be a typographical error and it is assumed that the actual specification is 0.9 x 10-6 in/in/ F. Property Table 12: Summary of laminate specifications and test results Specification Test Results Beam Web Beam Cover ASTM Avg / Pass/ Avg / Units Test Minimum Cov (%) Fail Cov (%) Method D3039- Tensile strength ksi 07 Longitudinal / 2.2 Pass 57.3 / 3.3 Pass Transverse / 1.8 Pass 46.0 / 8.0 Pass Tensile modulus of D3039- Msi elasticity 07 Longitudinal / 3.7 Fail 3.24 / 3.6 Pass Transverse / 2.2 Fail 2.85 / 3.2 Fail Compressive strength ksi D6641 Longitudinal / 3.1 Pass 45.8 / 6.6 Pass Transverse / 6.0 Pass 35.6 / 8.7 Pass Shear strength (1) psi D (1) (1) Pass Shear modulus Msi D / -- Pass 1.79 / 9.2 Pass Coefficient of thermal expansion In./in./ o F D x See -5 See 2.1 x x 10 text text (Longitudinal) Glass content % by weight D / 0.79 Pass 79.2 / 0.14 Note (1): The values reported as shear strength are the shear stresses computed from the loads at which the specimens began to slip in the test fixture. Actual shear strengths are higher. The ultimate tensile and compressive strengths for both the beam web and cover laminates easily met the minimum requirements of the specification. The tensile moduli results were low, however, except for the cover in the longitudinal direction. This means that the empty FRP shell (no deck or concrete in arch cavity) might be less stiff than thought. If so, deflections from self weight and from fluid loads during the pouring of the arch concrete could be greater than anticipated. In the completed beam, the FRP shell has little influence on the beam stiffness as the steel tension and concrete compression reinforcements are the main structural components. Shear modulus test results exceeded the specification. Ultimate shear strength could not be determined but it is likely that the laminate properties exceed the specification. The beam web specimens carried an average of 6993 psi shear stress before slipping in the test fixture, and based on the information in Figure 32, it is believed that ultimately shear strength is much higher. The table of material specifications in the Special Provisions document lists a minimum value for the coefficient of linear thermal expansion (CLTE). Logically, a specification on CLTE should be a maximum value. In that case, the CLTE values determined for the beam cover and web laminates do not meet the specification (Note that the CLTE test values shown in Table 6 have Pass / Fail Pass AEWC Advanced Structures & Composites Center Page 42 of 95

47 the standard units of expansion per C, while the value in Table 12 have been converted to expansion per F). The glass fiber contents of the beam cover and web witness panels exceeded the minimum specification of 60% Durability Test Results The result of the weathering treatment on the durability test panels showed some visible fading or discoloration of the surface. Some erosion of the surfaces was also visible with fibers becoming exposed. Figure 34 shows a comparison of the two halves of Panel 2. Figure 34: Durability test Panel 2 surface, un-exposed half on left, exposed half on right Table 13 and Table 14 contain lists of the equipment used for the mechanical property tests of the durability test panels. The equipment is identified by AEWC equipment ID numbers, and the dates that the tests were performed are included. Results summaries for each of the tests performed on specimens prepared from Panel 1 and Panel 2 are contained in the following subsections. Full tables of all data collected from this testing is contained in Appendix D. As explained in section 2.3, the principal fiber orientations were not known for these panels, therefore the test results should not be compared between panels. It is only valid to compare results of the un-exposed half of each panel to its matching exposed half. Table 13: Test dates and equipment list for coupon tests of durability test Panel 1 Test method ASTM D790 ASTM D3039 ASTM D2344 ASTM D4255 Property type Flexural Tension Short Beam In-plane shear Date 6/3/2009 5/22/2009 5/26/2009 6/9/2009 Test machine Load cell Test fixture Caliper Micrometer Other Aramis Aramis AEWC Advanced Structures & Composites Center Page 43 of 95

48 Table 14: Test dates and equipment list for coupon tests of durability test Panel 2 Test method ASTM D790 ASTM D3039 ASTM D2344 ASTM D4255 Property type Flexural Tension Short Beam In-plane shear Date 6/22/2009 6/12/2009 6/22/2009 6/24/2009 Test machine Load cell Test fixture Caliper Micrometer Other Aramis Aramis ASTM D790 Flexural properties under 3-point bending load The flexural properties of the durability test panel laminates were determined following ASTM D790 Standard Test Methods for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials. The tests were conducted and results computed in the same manner as described in section Table 15 contains a summary of the test results. Panel Panel 1 - Unexposed Panel 1 - Exposed Panel 2 - Unexposed Panel 2 - Exposed Table 15: ASTM D790 test results for durability test panels Ult. Bending Flexural Number of Support Loading Thickness Stress MOE specimens Span Rate (ksi) (Msi) (in) (in) (in/min) Average Std. Dev COV 5.8% 3.9% 2.2% Average Std. Dev COV 7.2% 8.5% 2.4% Average Std. Dev COV 6.4% 7.4% 2.1% Average Std. Dev COV 3.8% 5.5% ASTM D3039 Tensile Properties The tensile properties of the durability test panel laminates were determined following ASTM D3039 Standard Test Method for Tensile Properties of Polymer Matrix Composite Materials. AEWC Advanced Structures & Composites Center Page 44 of 95

49 The tests were conducted and the results computed in the same manner described in section The test results are summarized in Table 16. Table 16: ASTM D3039 Tensile property test results for durability test panels Panel UTS MOE Thickness Number of specimens Loading Rate (ksi) (msi) (in) (in/min) Panel 1 - Unexposed Average Std Dev COV 3.5% 3.7% 1.0% Panel 1 - Exposed Average Std Dev COV 3.5% 4.5% 2.2% Panel 2 - Unexposed Average Std Dev COV 1.5% 1.8% 1.5% Panel 2 - Exposed Average Std Dev COV 2.1% 2.2% 1.4% ASTM D2344 Short-beam strength The short-beam strength of the durability test panels was determined following ASTM D2344 Standard Test Method for Short-Beam Strength of Polymer Matrix Composite Materials and Their Laminates. The test performed was a three-point bending type loading using the fixture shown in Figure 29, but using a support span. The short support span promotes a shear type of failure in the specimen, as opposed to the longer span of ASTM D790 which is designed to obtain bending failure. The results of the test are reported as short beam strength, which is calculated as follows: P Short beam strength = A Where: P = maximum load observed during test A = cross-sectional area of specimen Table 17 contains a summary of the test results. AEWC Advanced Structures & Composites Center Page 45 of 95

50 Table 17: ASTM D2344 Short-beam strength test results for durability test panels. Panel Short Beam Number of Support Loading Thickness Strength specimens Span Rate (psi) (in) (in/min) Panel 1 - Unexposed Average Std. Dev COV 4.8% 3.1% Panel 1 - Exposed Average Std. Dev COV 4.9% 3.7% Panel 2 - Unexposed Average Std. Dev COV 3.4% 4.1% Panel 2 - Exposed Average Std. Dev COV 6.6% 1.8% ASTM D4255 In-plane shear properties The in-plane shear properties of the durability test panel laminates were tested following ASTM D4255 Standard Test Method for In-Plane Shear Properties of Polymer Matrix Composite Materials by the Rail Shear Method. The tests were conducted in the same manner as described in section The ultimate in-plane shear stresses could not be determined from these tests for the same reasons explained in section The shear stress that the specimens carried before slipping in the test fixture is not reported for these tests as it provides no useful information for evaluating the effects of the weathering treatment. The shear modulus properties of the durability test specimens were computed in the same manner as described in section Table 18 contains a summary of the tests results that were obtained. AEWC Advanced Structures & Composites Center Page 46 of 95

51 Table 18: ASTM D4255 Shear Properties Test Results Panel Shear Modulus Number of specimens (Msi) Panel 1 Unexposed Average Std. Dev COV 11.1% Panel 1 - Exposed Average Std. Dev COV 0.3% Panel 2 - Unexposed Average Std. Dev COV 11.3% Panel 2 - Exposed Average Std. Dev COV 8.9% Summary of Durability Study Results Table 19 contains a summary of the average test results for each of the tests performed for the durability study. The exposed half of Panel 1 received the following treatment: hours of constant UV 83%, 65 C hours of 12 hour cycles consisting of 4 hours condensing 50 C and 8 hours UV 60 C. This treatment cycle is the same as Cycle 1 listed in Table X2.1 Common Exposure Conditions of ASTM G154. The exposed half of Panel 2 received the same treatment, except that the second step (alternating UV and moisture cycles) was extended to a total of 2361 hours. AEWC Advanced Structures & Composites Center Page 47 of 95

52 Table 19: Summary of Durability Test Results In-Plane Shear ASTM D4255 Short Beam Strength ASTM D2344 Panel Treatment Tensile Properties ASTM D3039 Flexural Properties ASTM D790 UTS MOE UBS MOE Modulus (ksi) (Msi) (ksi) (Msi) (Msi) (psi) Panel 1 Un-exposed Panel 1 Exposed Change after treatment +7.8% +8.2% +8.0% +7.5% -5.7% +3.4% Panel 2 Un-exposed Panel 2 Exposed Change after treatment +3.9% +10.4% +13.4% +13.2% +10.2% +15.3% 3.11 Concrete Test Results Compressive strengths of the specimens were determined following ASTM C39. Compressive modulus was determined following ASTM C469. Table 20 contains a summary of the test results. Table 20: Concrete Test Results Specimen Description Date Cast Date Tested Days Cured Ult. Comp. Strength Compressive MOE (psi) (Msi) 671-Arch-1 SCC concrete arch 2/12/2009 2/23/ Arch-2 SCC concrete arch 2/12/2009 2/23/ Arch-6 SCC concrete arch 2/12/2009 3/9/ Arch-7 SCC concrete arch 2/12/2009 3/9/ Arch-2 SCC concrete arch 2/12/2009 3/13/ Arch-5 SCC concrete arch 2/12/2009 3/13/ Deck-2 Deck concrete 2/24/2009 3/9/ Deck-3 Deck concrete 2/24/2009 3/9/ Deck-4 Deck concrete 2/24/2009 4/28/ Deck-7 Deck concrete 2/24/2009 4/28/ AEWC Advanced Structures & Composites Center Page 48 of 95

53 4 Conclusions Following are the conclusions from this study: 1. HC Beam shell construction: Overall, the composite HC Beam performed well curing during the critical period of the arch concrete placement. However, following are significant improvements that should be made to insure the performance and safety of this product: a. The composite wings on the top plate should used on both sides of all beams. Currently, the design drawings only call for these wings on the exterior face of the fascia beams. During placement of the arch concrete, these wings provided substantial stiffness and stability to the test beam. Production beams should include this feature, unless further testing and analysis is performed to demonstrate that they are unnecessary to maintain the structural integrity of the beam during the arch concrete pour. b. Considerable local buckling was observed in the top plate during the placement of the arch concrete. In order to maintain beam stability and integrity during this pour, the top plate will need to be stiffened considerably. c. The splicing technique used to transfer load across the joint in the top plate and wings was largely ineffective, buckling under load until the joint closed in compression. If possible, the top plate and wings should be infused in one segment equaling the full beam length, and then adhesively bonded and mechanically fastened to the beam. d. The composite cross-ties appeared effective in restraining the beam webs during placement of the arch concrete, although some ties may have been stressed excessively. Closer spacing of the ties is recommended to insure that the beam webs do not bow outward during concrete placement. 2. HC Beam Camber: Initial deflections under the fluid load of the arch concrete and the fluid load of the deck concrete were in general agreement with the design calculations. However, immediately prior to static testing, the beam had a negative camber of approximately 1 3/8 in. at mid-span, which was a result of the following: a. The camber equations did not consider the self-weight of the beam, which deflected approximately 1.15 in. under its own weight prior to placement of the arch concrete. b. Shrinkage of the arch concrete and the deck concrete after placement resulted in additional deflections: shrinkage of the arch concrete resulted in a 30% increase from the initial mid-span deflection, and shrinkage in the deck concrete resulted in a 15% increase from the initial mid-span deflection. Prior to fabrication of the bridge girders, camber equations and methodology should be closely reviewed, and new camber requirements specified. 3. Initial Static Tests: Initial static shear and bending tests demonstrate that the HC Beam is linear-elastic under the design loading conditions, and that the analytical model developed by John Hillman is accurate in predicting beam behavior under service loads. 4. Fatigue Tests: Following 2,000,000 fatigue bending cycles, no deterioration or degradation was observed in the beam when loaded to its bending service load capacity. AEWC Advanced Structures & Composites Center Page 49 of 95

54 5. Final Static Tests: The last fully instrumented static shear and bending tests were performed up to full factored design loads. For both of these tests the response of the HC Beam as shown by the load vs. deflection data was the same as for the initial tests performed before the fatigue bending cycle, except that the final static tests were taken to higher loads. 6. Durability Tests: For almost all of the mechanical properties that were measured, the average strength and/or stiffness values increased after the weathering treatment. The only exception was the in-plane shear modulus for panel 1, which saw a 5.7% average decrease, but this difference is smaller than the typical COV for the shear modulus results in this study. The results suggest that the use of the UV inhibitor and pigment in the resin did a good job of limiting the degradation from weathering to just the surface of the laminate. The increases in most properties that were measured are likely due to the effect of resin post-curing resulting from the exposure treatment. References: 1. Signor, A.W., Chin, J.W., Effects of Ultraviolet Radiation Exposure on Vinyl Ester Matrix Resins: Chemical and Mechanical Characterization, Building Materials Division, National Institute of Standards and Technology, Gaithersburg, MD, 2001 AEWC Advanced Structures & Composites Center Page 50 of 95

55 Appendix A: Drawings for HC Beam superstructure in Knickerbocker Bridge AEWC Advanced Structures & Composites Center Page 51 of 95

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60 Appendix B: Knickerbocker Bridge Test Beam Drawings AEWC Advanced Structures & Composites Center Page 56 of 95

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65 Appendix C: Composite Cross-Tie Spacers and Spacer Test AEWC Advanced Structures & Composites Center Page 61 of 95

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