Soil structure interaction of integral abutment bridges

Elimination of the bearings and expansion joints in the superstructure of integral abutment bridges offers the advantage of reducing the initial and life cycle costs of the structure. However, such elimination may have an adverse effect on the displacement demand at the pile-abutment connection and on the earth pressures on the abutment wall due to the thermal expansion/contraction cycles of the bridge. These adverse effects have resulted in regulations that impose restrictions on the maximum length and skew angle of integral abutment bridges. This research consisted of a deep analysis of the problem by considering soil-structure interaction. The approach was multifaceted as it included experimental and numerical analysis. The experiments consisted of laboratory tests and large-scale filed tests, as well as monitoring of full-scale bridges already instrumented in Indiana. A new soil constitutive model was developed as part of the study. The model was validated and calibrated based on the laboratory and field experiments, and then used as part of a parametric analysis to provide recommendations for the design limits of integral abutment bridges. Parametric analysis was conducted using the verified calibrated constitutive model to examine the effect of different parameters on the performance of integral abutment bridges. The following parameters were investigated to develop recommendations for the design of integral abutment bridges: bridge length, skew angle, foundation stiffness, abutment wall stiffness, concrete shrinkage, and the sequence of loading. The parametric study results indicated that the maximum length and skew angle for integral abutment bridges with medium to stiff soils in the foundations could be 500-ft and 60o, respectively. The analyses indicated that the stiffness of the foundation had an adverse effect on the displacement demand on the piles for long bridges (\u3e1000ft) on soft foundation soils