Bearings are a relatively small component of bridge structures, but they are critical for safety and proper long-term performance.  The bearings must support the weight of a bridge as well as adjust for thermal expansion and contraction, traffic loads, and extreme events such as earthquakes and high winds.  Bearing failures can result in hazards to the traveling public, traffic delays, and costly damage to the bridge.  Therefore, accurate bearing design is critical to ensure the best and most economical bearing will be specified.

The AASHTO LRFD Bridge Design Specifications (BDS) currently contain minimal design criteria for disc bearings. The BDS requirements are predominately based on NCHRP Project 10-2A, “High-Load Multi-Rotational Bearings” initiated in 1986 and published in 1999. 

Due to the limited design specifications, bridge designers are dependent on disc bearing manufacturers’ unique in-house designs.  This uncertainty means that disc bearing designs may not be finalized until well into the construction of a bridge.  At such a late stage, field changes to accommodate the bearings are costly and disruptive.  Not only can incomplete design specifications result in substantial interruption during construction, they leave the owner uncertain about the long-term performance of the bearings.  There is currently limited means to determine how existing bearings perform over time, especially with increasing traffic volume cycles and loadings. A predominant bearing manufacturer estimated that 15,000 bridges in North America currently use their disc bearings.  Hence, the impact of flawed long-term performance could be significant.

The objective of this research is to develop design procedures and acceptance testing methods for high-load multi-rotational disc bearings.

The final products of this project will be (1) guidelines for all aspects of designing disc bearings, (2) guidelines for the acceptance criteria for owners and designers to specify when purchasing bearings, and (3) ballot-ready language for AASHTO to consider related to AASHTO LRFD BDS regarding disc bearing design and acceptance testing.