NCHRP 12-40 [Final]
Fatigue Criteria for Modular Bridge Expansion Joints
| Project Data
||Lehigh University |
||Robert J. Dexter|
This product of this study is performance-based specifications for the fatigue design of modular bridge expansion joints. In addition to the proposed fatigue design specification and commentary, a proposed fatigue test specification and commentary, and fatigue design examples were produced.Modular bridge expansion joints are designed to accommodate large longitudinal expansion and contraction movements of bridge superstructures. In addition to supporting wheel loads, a properly designed modular joint will prevent water and debris from draining onto the underlying superstructure and substructure. Many premature failures of modular bridge expansion joints can be attributed to fatigue problems. Expansion joints are subjected to more load cycles than other superstructure elements, but the load types and magnitudes, and fatigue-stress ranges that are applied to these joints have not been well defined. Additionally, sufficient data have not been available on field measurements and laboratory testing of fatigue-critical joint details. Neither the AASHTO Standard Specifications for Highway Bridges nor the AASHTO LRFD Bridge Design Specifications include fatigue design criteria for these joints. Because of this lack of data and guidance, modular bridge expansion joints in the United States are designed by their suppliers using proprietary techniques.The objective of this research was to develop performance based specifications and supporting commentary for the fatigue resistant design of modular bridge expansion joints for consideration by the AASHTO Highway Subcommittee on Bridges and Structures. The researchers identified critical parameters that influence fatigue performance of modular bridge expansion joints and the predominant causes for fatigue failure of in-service joints. Using field tests of modular bridge expansion joints they were able to assess behavior under static and dynamic truck loading and define critical stress locations. Fatigue criteria were developed through laboratory testing. These activities culminated in specific proposals to ensure the design of durable modular bridge expansion joints. The findings of this study are documented in NCHRP Report 402, Fatigue Design of Modular Bridge Expansion Joints.