Using loadings provided by the bridge designer, geotechnical engineers estimate foundation movements and report their findings to the bridge designer. The bridge designer will then design the structure to accommodate the anticipated total and differential movements to satisfy post-construction bridge performance requirements and to mitigate future maintenance issues. However, the current AASHTO LRFD Bridge Design Specifications do not provide clear criteria for movement limitations. The Specifications indicate that “the tolerable movement criteria shall be established by either empirical procedures or structural analyses or by consideration of both”. The bridge designer needs clear criteria and guidance to ensure more efficient bridge designs while protecting the short- and long-term integrity of structures.

The objectives of this research were to (1) develop procedures to determine the acceptable levels of bridge foundation movements based upon superstructure tolerance to total and differential movements considering service and strength limit states, and (2) propose revisions to the AASHTO LRFD Bridge Design Specifications. Foundation movement limits include vertical, horizontal, and rotational movements. Geotechnical assessment of foundation total and differential movements is not required.

the research agency’s final report that documents the entire research effort is available as NCHRP Web-Only Document 245: Bridge Superstructure Tolerance to Total and Differential Foundation Movement.