Evaluation of Pounding Effect on Seismic Response of Bridges under Soil-Structure Interaction

In order to reduce the cost and time of seismic analyses, as well due to lack of deep understanding of structural characteristics and the acting forces, usually, simplified assumptions are applied in structural modeling that could lead to unrealistic responses. Some of these simplified assumptions in bridge modeling are ignoring the pounding phenomenon and soil-structure interaction. Therefore, in the present study, by modeling three 3-span bridges, with different periods of frequency, the pounding effect, which happens in the gap between two parts of the deck and/or the deck and the abutments, on seismic responses of bridges under the near and far field accelerograms, was investigated. Also, the effect of dynamic properties of bridge and soil-structure interaction on pounding phenomenon was studied by calculating the parameters of maximum pounding force and number of impacts. Results showed that considering the pounding effect reduces the maximum displacement due to limiting the movements of the deck such that some of the piers remain within the elastic phase. Minimum and maximum reduced-displacements in different bridges were 31% and 48%, respectively. On the other hand, modeling the soil-structure interaction effect increased the values of maximum displacement (40%) and maximum pounding force (45%), as compared to that of fixed-base model. Also, the analysis of results in terms of the type of earthquake indicated that the near field earthquakes lead to greater responses in the bridges than the far field earthquakes.