Analyzing and designing for substructure movement in highway bridges: an LRFD approach

Schopen, Dustin
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University of Delaware
Movement of bridge substructures can adversely affect the strength and serviceability of bridge superstructures. Research concluded in 1985 utilized field and analytical studies to create tolerable bridge movement limits. Because the limits were determined based on the design and loading provisions of the American Association of State Highway and Transportation Officials (AASHTO) Standard Specifications for Highway Bridges, there was a need for the previous research to be reproduced and updated based on the provisions of the AASHTO Load and Resistance Factor Design (LRFD) Bridge Design Specifications. Simple two-dimensional analytical models and models of actual in-service highway bridges were analyzed in order to study the effects of differential vertical movement. The results obtained from the analyses suggested that, in general, the reserve moment capacities of bridge girders are sufficient to resist the additional stresses caused by differential settlement of bridge substructures. Despite the ability of most bridges to tolerate small magnitudes of differential vertical substructure movement, expected movements should be accounted for during the design process to ensure that safety and reliability are maintained. A method of calculating the effects of anticipated differential settlements was determined. It is recommended that force effects associated with anticipated differential vertical movements of substructures be included in the design of bridge girders.