Time-Dependent Behavior of Continuous Composite Integral Abutment Bridges

Integral abutment bridges provide bridge engineers with an economical and attractive design alternative to traditional bridges with thermal expansion joints. Very limited design and construction guidelines are available and no unified design procedures exist, hence there is a lack of enthusiasm to adopt integral abutment bridges for long spans. Time-dependent effects of creep, shrinkage, and temperature on composite superstructure, soil pressure from abutment backfill, and soil-substructure-superstructure interaction are the main parameters governing the design. Analytical models and numerical procedures are developed for predicting instantaneous linear and nonlinear time-dependent long-term behavior of continuous composite integral abutment bridges. The redistributions of moments due to temperature gradient, creep, shrinkage, and restraints provided by abutment foundation and backfill have been considered in the analysis. The substructure system is modeled as discrete springs for translational and rotational degrees of freedom. A numerical design example is illustrated showing the deformations and stresses due to time-dependent effects on a continuous composite deck due to typical sustained loads and compared with those of the conventional bridge system on seat-type abutments. The axial forces and moments on the piles supporting the abutment were used to analyze the behavior of the laterally loaded piles. Recommendations are presented for the analysis and design of integral abutment bridges.