Ayman M. Okeil, Ph.D., P.E. Steve Cai, Ph.D., P.E.

Transcription

1 Ayman Okeil, Ph.D., PE Ayman M. Okeil, Ph.D., P.E. Steve Cai, Ph.D., PE Steve Cai, Ph.D., P.E. Louisiana State University 2009 Louisiana Transportation Conference (Feb. 9, 2009) 1

2 Motivation Monitored Bridge Monitoring System Installation Preliminary Data Lessons Learned Summary and Conclusions Acknowledgements

3 3 Slab-on-girder systems are one of the most feasible alternatives in bridge construction Precast prestressed girders have a large market share within this alternative Simply-supported spans are known to be problematic because of: deterioration near joints due to deicing agents high maintenance costs riding quality Constructing continuous spans has been a goal of engineers for quite some time

4 4 Continuous spans eliminate many of the problems associated with expansion joints They also allow engineers to achieve longer span lengths using the same cross section The detailing of the continuity diaphragm has been a research subject for years due to some shortcomings that were observed in continuous bridges NCHRP Project (Miller et al. 2004) surveyed continuity details already in service and made recommendations based on experimental and analytical investigations

5 5 Positive moments at intermediate supports can be caused by live loads on far away spans Deflections B.M.D.

6 6 Long-term effects (creep, temperature gradients, etc.) 250 Girder End Moment Casting Continuity Cracking Moment caused by temperature gradient Moment due to creep and temperature gradient Time (days) Application of SDL

7 7 Based on their study, including experimental and analytical investigations, an NCHRP Report (No. 519) was published with a recommended detail and design procedure (Miller et al. 2004)

8 8 One of the recommendations of NCHRP Report 519 is to cast the diaphragm when the girders are at least 90 days old. (Miller et al. 2004)

9 9 The John James Audubon Bridge in Louisiana is a major project that involves 8 bridges including a cable-stayed major span over the Mississippi River It was contracted as a design-build project (

10 10 The project designer chose to adopt the new NCHRP 519 detail, which is different than the continuity detail currently used in Louisiana One of the bridges is over a railway track, and hence, one segment used Bulb Tee girders (BT-72) The bents were also skewed to accommodate the railway track Both choices (BT-72 and skew) were not within the scope of NCHRP Project Thus it was deemed necessary to monitor the performance of the detail in these configurations

11 Motivation Monitored Bridge Monitoring System Installation Preliminary Data Lessons Learned Summary and Conclusions Acknowledgements

12 12 BRIDGE #2 Five Bulb-T girders (BT-72) Cast-in-place deck (7.5 ) 38'-0" 7.5" G1 G2 G3 G4 G5 4 x 8'-3" = 33'-0"

13 13 BENT 23 BENT 24 51'-0" 102'-0" 89'-0" BRIDGE #2 Three skewed spans Two positive moment continuity details (antisymmetric) Focus on one (Bent 24) BENT 25 BENT 26

14 14 BENT 24 Three girders will be monitored to study effect of skew G4 G5 G3 G2 G1 BENT 24

15 15 Midspan Symmetry allows monitoring three girders G4 G5 G3 G2 G1 BENT 24 G1 G5, G2 G4 102'-0" BENT 25

16 16 Performance of positive moment detail; especially hairpin bars at girder ends. Hairpin bars #5

17 Motivation Monitored Bridge Monitoring System Installation Preliminary Results Lessons Learned Summary and Conclusions Acknowledgements

18 18 Desired Features Two sensor groups Embedded Surface mounted Robust Strains Displacements Rotations Crack widths Gaps Data retrieval Wireless Automated Redundant Multiple sensors Multiple methods

19 76 sensors (with room for 20 more capacity: 96) 3VW 1EC 3VW G5 1TM 2ES 1DM 2ES 1TM G4 G3 3VW 1EC 3VW 3VW G2 1TM 2ES 1DM 3VW 2ES 1TM 3VW 2ES 3EC 2ES 3EC G1 3VW 1EC 3VW 3VW 1TM 2ES 1DM 2ES 1TM 2ES 3EC BENT 24 EC: sisterbar strain gage (12) ES: strandmeter strain gage (18) BENT 25 VW: strain gage (30) TM: tiltmeter (6) DM: displacementmeter (3) CM: crackmeter (7) 19

20 20 At Joint 1EC At Midspan 1EC SENSOR LEGEND 1ES 1EC Strrandmeters (VW 4410) 2ES 2ES 1ES 1EC Sisterbars (VW 4911) 4 Sisterbars Strain Gages 6 Strandmeter Strain Gages 10 Sensors per girder

21 21 3VW 3VW SENSOR LEGEND 1TM 1TM Tiltmeter (VW 6350) 1DM 9 Strain Gages 2 Tiltmeters 1 Crackmeter 12 Sensors per girder Strain Gages (VW 4000) Crackmeters (VW 4420)

22 22 The monitoring system will capture : Girder End Rotations Tiltmeters Differential rotations Continuity Strains in Hairpin Bars Strain gages End forces and moment Continuity Strains in PS Strands Strain gages Stresses and moments Continuity Girder Gap Displacement meters Continuity

23 23 The monitoring system will also provide information about : Prestressing Losses Strain gages Stresses and moments Differential Shrinkage Strain gages Temperature Gradients Built-in thermistors Distribution Factors Strain gages Requires instrumenting G4 and G5

24 Motivation Monitored Bridge Monitoring System Installation Preliminary Data Lessons Learned Summary and Conclusions Acknowledgements

25 25 Embedded sensors All girder sensors have been installed (2 glitches) All deck sensors have been successfully installed Surface-mounted sensors: All were successfully installed (last week) Survival rate = 100%

26 CY Data Intermittent Manual Readings All Data July 2008 August September October November December January 2009 Girder Casting CY Logger Disconnected Girder Replacement Deck Pour System Complete Embedded Installation #1 Embedded Installation #2 Surface Installation

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28 Sisterbars Strandmeters

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33 Motivation Monitored Bridge Monitoring System Installation Preliminary Data Lessons Learned Summary and Conclusions Acknowledgements

34 Phase I (Casting Yard) Only 18 sensors were connected Data for 32 days after casting

35 Phase II (Bridge Site) Completed last month (January 9, 2009) 100% sensor survival System testing is underway to eliminate any kinks Data mining algorithms are being developed (spreadsheets will no do) Goal: Full automation of data collection and processing

36 Girder Bottom Opening DM Displacement, (in) Displacement, (in) Displacement, (in) Temperature, T ( o F) /05/ /14 01/19 01/26 02/02 02/09 Date, t /05/ /14 01/19 01/26 02/02 02/09 Date, t /05/ /14 01/19 01/26 02/02 02/09 Date, t /05/ /14 01/19 01/26 02/02 02/09 Date, t

37 Girder End Relative Rotations TM Slope, θ (deg.) Differential Slope, (θ left - θ right ) /19/ /26 02/02 02/09 Date, t

38 Girder End Strains ES Strain (µε) /19/ /17 08/14 09/11 10/09 11/06 12/04 01/01/ /29 Day, t

39 Midspan Strains (bottom) ES Strain (µε) /19/ /17 08/14 09/11 10/09 11/06 12/04 01/01/ /29 Day, t

40 Temperatures (Midspan G3) Temperature, T ( o F) Temperature, T ( o F) /19/ /17 08/14 09/11 10/09 11/06 12/04 01/01/ /29 Date, t Deck Girder (top) 20 06/19/ /17 08/14 09/11 10/09 11/06 12/04 01/01/ /29 Date, t Temperature, T ( o F) Girder (bottom) 20 06/19/ /17 08/14 09/11 10/09 11/06 12/04 01/01/ /29 Date, t

41 Motivation Monitored Bridge Monitoring System Installation Preliminary Data Lessons Learned Summary and Conclusions Acknowledgements

42 The experience gained from this project show the importance of : Thorough planning of every single step in the process to avoid missing chances Open channels of communication between all parties (casting yard, contractor, designer, owner, supplier) Sensor and wiring protection (100% survival rate) Data management is a serious issue. Spreadsheets will not do because of the enormity of the recorded data Data mining algorithms is the solution

43 Motivation Monitored Bridge Monitoring System Installation Preliminary Data Lessons Learned Summary and Conclusions Acknowledgements

44 The findings of this study (so far) can be summarized in the following : A new monitoring system has been designed to study the long-term performance of NCHRP 519 continuity detail in a new configuration (skew, Bulb-T) The system has been installed and is currently running Preliminary data from the casting yard has been collected and is currently being analyzed Data collection from the completed system started last month (Jan. 9, 2009) Data analysis started

45 The authors gratefully acknowledged the financial support provided by the Louisiana Transportation Research Center (LTRC Project No. 08-1ST) and Louisiana Department of Transportation and Development (State Project No ). The input and support of the following is also gratefully acknowledged: Hossein Ghara, P.E. (LADOTD) Paul Fossier, P.E. (LADOTD) Walid Alaywan, P.E. (LTRC) Randy Young (LTRC) Jeremy Adkins (Dunham Price) Eric Hebert (Dunham Price) Scott Aschermann (BDI) Jeff Schulz (BDI) Dante Luis (LTM Managers) Wayne Marchand (LTM Managers) Zach Jopling (Boh Bros.) G.J. Schexnayder (Boh Bros.)

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