BACKGROUND

The American Association of Highway and Transportation Officials (AASHTO) LRFD Bridge Design Specifications (BDS) currently contain limited design criteria for disc bearings. The BDS requirements are predominately based on NCHRP Project 10-20A, “High-Load, Multi-Rotational Bearings: Design, Materials, and Construction” initiated in 1986 and published in 1999 as NCHRP Report 432: High-Load Multi-Rotational Bridge Bearings.  At the time, only one company manufactured disc bearings and testing samples of their product were limited.  Since 1999, multiple companies manufacture disc bearings and industry standards have progressed. 

Due to the limited research, bridge designers are reliant on disc bearing manufacturers’ unique in-house designs, which introduces uncertainties that may result in nonuniform reliability and performance. Renewed consideration of high-load multi-rotational (HMLR) disc bearings would likely result in a more thorough and robust design approach. Research is needed to update the current practice for the design, fabrication, and construction of disc bearings.

OBJECTIVE

The objective of this research is to develop design procedures and acceptance testing methods and criteria for HLMR disc bearings for highway bridges. It shall be applicable to all design limit states.

Accomplishment of the project objective will require at least the following tasks.

TASKS

PHASE I—Planning

Task 1. Conduct a literature review on the design and the acceptance testing of HLMR disc bearings. The review shall include published and unpublished documentation and research conducted through the NCHRP; Federal Highway Administration; other national, state, and local agencies; and international organizations.

Task 2. Synthesize the results of the literature review to identify knowledge gaps related to the research objective. These gaps should be addressed in the final product or the recommended future research, as budget permits.

Task 3. Propose the research plan to be executed in Phase II to achieve the research objective. At a minimum, the research plan shall include:

• Development of a theoretical model to describe the response of the bearings to loads as a function of geometry and material properties. 
• Development of an experimental program with laboratory tests to calibrate any coefficients in the model and to verify with reasonable accuracy the behavior of bearings. 
• Development of testing procedures for predicting long-term performance of the HMLR disc bearing.
• A list of design examples to demonstrate the use of the design procedures. The design examples shall cover a range of bridge geometry.
• A plan for coordinating with domestic manufacturers of HLMR disc bearings.

Task 4. Prepare Interim Report No. 1 that documents Tasks 1 through 3 and provides an updated work plan for the remainder of the research. The updated plan must describe the process and rationale for the work proposed for Phases II through IV.

PHASE II—Execution

Task 5. Execute the research plan according to the approved Interim Report No. 1.

Task 6. Develop design procedures and acceptance testing methods and criteria for HLMR disc bearings. 

Task 7. Prepare Interim Report No. 2 that documents Tasks 5 and 6 and provides an updated work plan for the remainder of the research. The updated work plan must describe the process and rationale for the work proposed for Phases III and IV.

PHASE III—Draft AASHTO Deliverable

Task 8. Revise the proposed design procedures and acceptance testing methods and criteria for HLMR disc bearings after consideration of the panel’s review comments.

Task 9. Develop draft language that may be considered by the AASHTO Committee on Bridges and Structures for inclusion in its next update of the AASHTO LRFD Bridge Design Specifications and AASHTO LRFD Bridge Construction Specifications (hereafter called AASHTO Deliverable).

Task 10. Prepare design examples according to the approved Interim Report No. 2.

Task 11. Prepare Interim Report No. 3 that documents Tasks 8 through 10 and provides an updated work plan for the remainder of the research. The updated work plan must describe the process and rationale for the work proposed for Phase IV.

PHASE IV—Final Products

Task 12.  Revise the AASHTO Deliverable and design examples after consideration of the panel’s review comments.

Task 13. Submit the draft final deliverables including (1) the AASHTO Deliverable, (2) a final report that documents the entire research effort, (3) design examples, and (4) a stand-alone technical memorandum titled “Implementation of Research Findings and Products.” 

STATUS: A research agency has been selected for the project. The contracting process is underway.