Validation of Design Recommendations for Integral‐Abutment Piles

Abstract

Because integral‐abutment bridges decrease the initial and maintenance costs of bridges, they provide an attractive alternative for bridge designers. The objective of this project is to develop rational and experimentally verified design recommendations for piles in these bridges. Field testing consists of instrumenting two bridges in Iowa to monitor air and bridge temperatures, bridge displacements, and pile strains. Core samples are also collected to determine coefficients of thermal expansion for the two bridges. Design values for the coefficient of thermal expansion of concrete and revised temperature ranges for the deck and girders of steel and concrete bridges are recommended. A girder extension model is developed to predict the longitudinal bridge displacements caused by changing bridge temperatures. The pile is idealized as an equivalent cantilever. The frame model better predicts both the longitudinal displacement and weak‐axis pile strains. A lateral frame model is presented to predict the lateral motion of skewed bridges. Two alternatives for the pile design are reviewed: the first alternative, the more conservative, includes thermally induced stresses; the second neglects thermally induced stresses but allows for inelastic redistribution of forces.