Soil-foundation interaction effects in bridges with monolithic column-superstructure connection

Soil-structure interaction is of great significance in seismic design and assessment of reinforced concrete (RC) bridges. Recent research studies indicate that foundation-pier interaction effects may considerably alter the seismic response of R.C. bridges by partly mitigating the deformation demands in the piers at the expense of some permanent residual deformation of the foundation. The main objective of the present work is to investigate the impact of soil-structure interaction effects on the response of R.C. bridges and bridge piers, through the implementation of detailed F.E models. For this reason, extensive pushover analyses were conducted for the pier substructure (foundation-pier assembly) using sophisticated plasticity constitutive models to represent structural and soil material behavior. Typical soil conditions and bridge configuration types of highway overcrossings were studied in order to quantify the expected damages on critical elements and the vulnerability of the entire bridge system. Recognizing that the column-bent is the critical structural element that controls the stability of the entire system, and should therefore maintain its ability to sustain significant deformations, the contribution of soil-structure interaction effects is examined and evaluated with reference to soil properties and structural system type. From the analytical results it is shown that foundation soil compliance may alleviate under conditions the column-bent deformation demands, as the rotating pile-foundation provide an additional resistance mechanism.