Sponsors:  

South Dakota Department of Transportation, Mountain-Plains Consortium (MPC) – University Transportation Center (UTC) 

Project Funds:  $164,125 ($89,880 from SDDOT and $74,245 from MPC)

Year:  2016-2018

Personnel:  

PI:  Mostafa Tazarv, PhD, PE

Co-PI:  Junwon Seo, PhD, PE

Co-PI:  Nadim Wehbe, PhD, PE

Graduate Research Assistant:  Sandip Rimal; Brian Kidd (supervised by Dr. Seo)

Industry Collaborators/Donors:  Corr Construction Services, Inc;  Forterra Pipe & Precast, LLC;  GeoTek Engineering & Testing Services, Inc. 

Project Summary:

The most common type of bridge on South Dakota (SD) local roads is prestressed double-tee (DT) girder bridge.  More than 700 DT bridges are currently in-service in the state.  The SD local transportation system carries millions of dollars of agricultural products to market, connects people, and provides access to farms, state parks, and recreational sites.  

Load rating of damaged bridges is challenging mainly because of a lack of information regarding the capacity and load distribution of damaged components.  Successful execution of the project will result in a reliable load rating method in which the effect of different damage types and condition states on load rating parameters such as live load distribution factors and capacities will be quantified.  Accurate load rating of double-tee girder bridges could ultimately allow for maximum use of existing structures while providing safe travel to the public and preserving the bridge investment.

Both field and laboratory testing will be conducted to understand the live load distribution and dynamic load allowance specific to DT and to accurately calculate the actual capacity of deteriorated bridges with various distress conditions.  A load rating guideline based on the inspection data and visual damage in DT bridges will be developed to further help engineers to rate those bridges in a timely and accurate fashion.

Project Work Plan:

Task 1:  Meet with the technical panel to review project scope and work plan. 

Task 2:  Review literature nationwide pertaining to load rating bridges using visual inspections and instrumentation. 

Task 3:  From bridge inventory data supplied by SDDOT, summarize the prevalence of distress types and severity on double tee bridges in South Dakota. 

Task 4:  Propose a methodology to associate load ratings with visible distress type and severity. 

Task 5:  Assess the need for load testing girders removed from an existing double tee bridge to more accurately associate load ratings with visual inspections.  

Task 6:  Develop a field experiment plan that proposes bridges to be tested, instrumentation, load test vehicle(s), and procedures for load testing and visual inspection. 

Task 7:  Submit a technical memorandum and meet with the project technical panel to present the results of Tasks 2-6 and obtain approval for the field experiment plan. 

Task 8:  Upon approval of the plan by the technical panel, install instrumentation at the selected bridges, providing the technical panel at least two weeks’ notice to allow them to observe the installation. (A member of the SDDOT or local authority must be on site during all activities on bridge sites.) 

Task 9:  Perform visual inspections and load testing at selected bridge sites, providing the technical panel at least two weeks’ notice to allow them to observe the testing. 

Task 10:  Analyze load testing results and develop recommendations for load ratings on tested bridges. 

Task 11:  Perform load testing on salvaged girders for an existing double tee bridge.

Task 12:  Analyze load testing results on salvaged girders to develop recommendations for ultimate capacities and load ratings.

Task 13:  Submit a technical memorandum and meet with the project technical panel to present the results of Task 8-12. 

Task 14:  Using data from the field experiment, refine the method that associates bridge load ratings to visual distress and describe the method’s applicability and expected accuracy. 

Task 15:  Submit a technical memorandum and meet with the project technical panel to present the results of Task 14. 

Task 16:  Develop a guidance document briefly summarizing the work performed in this study and presenting techniques to estimate structures’ load rating through visual inspection. 

Task 17:  In accordance with Guidelines for Performing Research for the South Dakota Department of Transportation, prepare a final report and executive summary of the research methodology, findings, conclusions, and recommendations. 

Task 18:  Make an executive presentation to the SDDOT Research Review Board at the conclusion of the project. 

Publications:

1. Rimal, S., Kidd, B., Tazarv, M., Seo, J., and Wehbe, N. (2020). “Methodology for Load Rating Damaged Double-Tee Girder Bridges,” Journal of Bridge Engineering, ASCE, Vol. 26, No. 1, 13 pp. (Link) .

2. Rimal, S., Kidd, B., Tazarv, M., Seo, J., and Wehbe, N. (2019). “Methodology for Load Rating Double-Tee Bridges.” North Dakota State University - Upper Great Plains Transportation Institute, Fargo: Mountain-Plains Consortium (MPC), MPC Report No. 19-389, 232 pp. (Link).

3. Rimal, S. "Methodology for Load Rating Double-Tee Bridges," MS Thesis, South Dakota State University, 234 pp., (Link).

Salvaged Double-Tee Girders for Strength Testing

Two bridges in Rapid city, which were in line for replacement, were inspected in July 2017.  Two deteriorated double-tee girders, one 50-ft long and one 30-ft long, were selected for strength testing.  These two 5-yr old girders were removed from the bridge and were shipped to the Lohr Structures Laboratory at South Dakota State University.  The two girders were tested monotonically to failure.

Results of Salvaged Double-Tee Girders for Strength Testing

50-ft Girder

The girder failed by failure of the flange at the midspan.  Several flexural cracks were observed before failure.  However, the girder did not meet the AASHTO limit state requirements.  

Results of Salvaged Double-Tee Girders for Strength Testing

30-ft Girder

The girder failed by by significant reduction in the load carrying capacity.  Several flexural and shear cracks were observed before failure.  However, the girder did not meet the AASHTO limit state requirements.