A New Relationship for Determining the Impact Force between Two Adjacent Structures Considering Building Pounding

Insufficient separation distance between two adjacent buildings can cause to collision when large lateral displacements are accrued due to seismic excitation. The impact force between structures induces many serious damages, which is called building pounding. In this study, pounding between two dynamic models is investigated and the impact force is numerically calculated. The impact is simulated based on special elements, including spring and dashpot, and the impact force and dissipated energy during the impact are determined. Both mentioned parameters depend significantly on the impact velocity, spring stiffness and the value of damping. For this purpose, the impact velocity of collision is parametrically measured and subsequently, coefficient of restitution is automatically determined. Furthermore, the impact damping ratio and nonlinear stiffness of spring are calculated to evaluate the impact between models. Finally, a new equation is presented to determine the value of damping and the accuracy of formula is confirmed, which is verified by three various approaches. In the first stage, an experimental test is considered and the peak impact force is extracted when a concrete ball is dropped on a rigid concrete surface. On the other hand, a numerical simulation is similarly assumed and the suggested formula is used to determine the peak impact force during collision. Then, the results of the peak impact forces between experimentally and numerically analyses are compared, which shows both are close to each other. Secondly, an estimated impact between two bodies has been studied. The results of the analysis are also compared between the dissipated and kinetic energies during impact. The comparisons indicate relatively low errors between the calculated and assumed values of the coefficient of restitution when the proposed equation is used. Finally, a value of the coefficient of restitution is selected and an impact is simulated to show hysteresis loop. The enclosed area of each loop is calculated as the dissipated energy and compared with the energy absorption. The above three comparisons show that the proposed formula is very effective and the accuracy of the impact force, calculated by the suggested formula as a parameter of the impact force model, is also acceptable.