Rehabilitation of Double-Tee Bridges

Sponsors:

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

Project Funds: $160,000 ($85,722 from SDDOT and $74,278 from MPC)

Year: 2015-2017

Personnel:

PI: Nadim Wehbe, PhD, PE

Co-PI: Mostafa Tazarv, PhD, PE

Graduate Research Assistant: Lucas Bohn

Industry Collaborators/Donors: Lafarge North America, Headed Reinforcement Corp., Journey Group Construction, Insteel Wire Products, Co., and Forterra Pipe & Precast, LLC.

Project Summary:

Among several bridge girder types, precast double-tee girders are common on county bridges in South Dakota because of the ease of construction, the reduced construction time, and the potentially lower overall cost. However, the longitudinal joints of these bridges are rapidly deteriorating with many needing replacement before the expected 75-year service life. Research was conducted at South Dakota State University (SDSU) to develop, construct, and evaluate the performance of rehabilitation methods on this type of bridge.

Current detailing between adjacent double-tee bridge girders consists of discrete welded steel connections. Wehbe et al. (2016) showed that this longitudinal joint detailing is insufficient for fatigue, service, and strength loading, thereby significantly reducing the lifespan of these type of bridges. Currently, there are more than 700 double-tee girder bridges in South Dakota incorporating this joint detailing.

Twenty joint detailing alternatives for the rehabilitation of the longitudinal joint of double-tee girder bridges were proposed in the present study. Of the 20 alternatives, continuous joint details were selected for further study since they offer minimal durability issues. Ultra-high performance concrete (UHPC) and latex modified concrete (LMC) were selected as the filler materials because of their improved strength and durability.

Thirteen large-scale beam tests were carried out to investigate the performance of the selected joint rehabilitation details and to select the best for large-scale testing. Subsequently, two joint concepts, “pocket” and “continuous”, were developed and analytically investigated using linear finite element analyses to optimize the selected joint detailing.

A full-scale 40-ft long double-tee bridge consisting of two interior girders was constructed using conventional longitudinal joint detailing then initially tested under fatigue loads. Subsequently, the bridge was rehabilitated using the two proposed details, “pocket” joint with UHPC and “continuous” joint with LMC each incorporated on half the length of the bridge. The rehabilitated specimen was first tested under 500,000 cycles of the AASHTO Fatigue II loading followed by an additional 100,000 of the AASHTO Fatigue I load cycles. Stiffness tests were performed to monitor the degradation of the bridge. Finally, the specimen was monotonically tested to failure. No significant damage beyond initial shrinkage cracks in LMC was observed throughout the fatigue testing. In addition, the stiffness of the bridge did not degrade. No damage or yielding of the reinforcement in the joint was observed throughout the strength testing. The rehabilitated bridge met all the AASHTO limit state requirements indicating sufficient performance. Overall, both rehabilitation methods are structurally viable alternatives for rehabilitation of double-tee bridge girders to extend their life for another 75 years. However, only UHPC should be used as filler material. The rehabilitation cost of a double-tee bridge with pocket detailing will be only 30% of the bridge replacement cost.

Project Work Plan:

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

Task 2: Interview SDDOT and construction company personnel in South Dakota for feasible rehabilitation concepts.

Task 3: Review bridge inspection data, including condition, pavement type, location, and chloride use, for in-service double-tee bridges in South Dakota.

Task 4: Perform literature review for possible concepts for rehabilitating the longitudinal joint, including joint designs, construction methods, and estimated cost for each method.

Task 5: Prepare and submit a technical memorandum that describes existing double-tee bridges by age, condition, and sufficiency rating notes, proposes feasible rehabilitation methods, estimates implementation costs, and recommends rehabilitation on double-tee bridges where applicable.

Task 6: Meet with the project technical panel to discuss the results of the literature review and technical memorandum and have the panel decide which concept(s) to advance to the testing phase.

Task 7: Prepare a technical memorandum detailing joint designs, construction methods, and a complete instrumentation and testing plan for technical panel review.

Task 8: Upon approval of the plan by the technical panel, proceed with construction and instrumentation of test girders, providing the technical panel at least two weeks’ notice to allow technical panel members to observe the construction and instrumentation.

Task 9: Perform ultimate and fatigue loading of rehabilitated girders, providing the technical panel at least two weeks’ notice to allow technical panel members to observe the testing.

Task 10: Compare test results to results of the original and improved joint designs of SD2013-01 to draw conclusions on constructability, structural performance, and cost.

Task 11: Prepare a marketing brochure for local government highway officials including rationale for rehabilitation, guidance for determining when rehabilitation is appropriate, and a description of how rehabilitation is achieved.

Task 12: 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 13: Make an executive presentation to the SDDOT Research Review Board at the conclusion of the project.

Publications:

Tazarv, M., Bohn, L., Wehbe, N. (2019). “Rehabilitation of Longitudinal Joints in Double-Tee Bridges,” Journal of Bridge Engineering, ASCE, ASCE, DOI: 10.1061/(ASCE)BE.1943-5592.0001412, Vol. 24, No. 6, 14 pp (Link).
Bohn, L., Tazarv, M., Wehbe, N. (2019) “Rehabilitation of Longitudinal Joints in Double-Tee Girder Bridges.” North Dakota State University - Upper Great Plains Transportation Institute, Fargo: Mountain-Plains Consortium (MPC), MPC Report No. 19-398, 106 pp (Link).
Bohn, Lucas Michael, "Rehabilitation of Longitudinal Joints in Double-Tee Girder Bridges" (2017). MS Thesis, South Dakota State University, 232 pp (Link).