Seismic excitation, which results in large horizontal relative displacements, may cause collisions between two adjacent structures due to insufficient separation distance between them. Such collisions, known as earthquake-induced structural pounding, may induce severe damage. In this paper, the case of pounding between two adjacent buildings is studied by the application of single degree-of-freedom structural models. Impact is numerically simulated with the use of a nonlinear viscoelastic model. Special attention is focused on calculating values of impact forces during collisions which have significant influence of pounding-involved response under ground motions. The results of the study indicate that the impact force time history is much dependent on the earthquake excitation analyzed. Moreover, the peak impact forces during collision depend substantially on such parameters as gap size, coefficient of restitution, impact velocity, and stiffness of impact spring element. The nonlinear viscoelastic model of impact force with the considered relation between the damping coefficient and the coefficient of restitution has also been found to be effective in simulating earthquake-induced structural pounding.

The effect of higher modes of vibration on the total non‐linear dynamic response of a structure is a very important and unsolved problem. To simplify the process the static non‐linear pushover analysis was proposed associated with the capacity spectrum method, utilising a load pattern proportional to the shape of the fundamental mode of vibration of the structure. The results of the pushover analysis, with this load pattern, are very accurate for structures that respond primarily in the fundamental mode. But when the higher modes of vibration become important for the total response of the structure, this load pattern loses its accuracy. To minimise this problem a new multimode load pattern is proposed based on the relative participation of each mode of vibration in the elastic response of a structure subjected to an earthquake ground motion. This load pattern is applied to the analyses of symmetric frames as well as to stiffness asymmetric and mass asymmetric irregular building frames, under seismic actions of distinct orientations, permitting to draw significant conclusions.

This study focuses on preventing collisions between structuresduring seismic excitation based on gap size. Several approximatedequations in order to estimate separation distancebetween buildings are collected and evaluated to measure gapsize in order to avoid impact between them when large lateraldisplacements occurred due to earthquake. Artificial neuralnetworks are utilized to estimate the required distance betweenstructures. The majority of building codes suggest separationdistances based on maximum lateral displacements of eachbuilding or height of buildings in order to provide safety gapsize between them. Subsequently, researchers have proposedseveral equations to predict the critical distance. In currentstudy, some MDOF models are equivalently modelled and optimumgap size between buildings is approximately estimatedand finally a new equation for separation distance is suggestedand the accuracy of formula is numerically investigated.

Insufficient separation distance between adjacent buildings may lead to serious damages during earthquakes due to structural pounding. The best way to prevent collisions is to provide sufficiently large separation distance between structures. In this paper, the periods of two closely spaced linear and nonlinear buildings have been investigated so as to accurately assess the minimum in‐between separation gap. A new equation to calculate the effective periods of inelastic buildings has been proposed, and its effectiveness has been verified through numerical analysis. The results of the investigation conducted for inelastic buildings with different number of stories indicate that the proposed formula allows us to prevent earthquake‐induced structural pounding by ensuring an adequate value of seismic gap.

This paper provides an overview on some experimental activities developed by the authors, that represent a research group from European countries which has been cooperating for the last few years on common theoretical and laboratory activities, within the framework of some European or National research projects. Highlights are presented in the paper focusing on experimental researches including the design, set up and testing of different control devices, executed on shaking table facilities and equipments available at the Universities of Naples, Porto and Lisbon.

Structural pounding during earthquakes may cause substantial damage to colliding structures. The phenomenon is numerically studied using different models of collisions. The aim of the present paper is to propose an effective formula for the impact damping ratio, as a parameter of the impact force model used to study different problems of structural pounding under seismic excitations. Its accuracy has been verified by four various approaches. Firstly, for the case of collisions between two structural elements, the dissipated energy during impact has been compared to the loss of kinetic energy. In the second stage of verifications, the peak impact forces during single collision have been analyzed. Then, the accuracy of different equations have been verified by comparing the impact force time histories for the situation when a concrete ball is dropped on a rigid concrete surface. Finally, pounding between two structures during earthquakes has been studied. The results of the analysis focused on comparison between dissipated and kinetic energy show relatively low errors between calculated and assumed values of the coefficient of restitution when the proposed equation is used. In addition, the results of the comparison between experimentally and numerically determined peak impact forces during single collision confirm the effectiveness of the approach. The same conclusion has been obtained for the whole impact time history for collision between a ball and a rigid surface. Finally, the results of the comparative analysis, conducted for pounding between two structures during an earthquake, confirm the simulation accuracy when the proposed approach is used. The above conclusions indicate that the proposed formula for impact damping ratio, as a parameter of impact force model for simulation of earthquake-induced structural pounding, is very effective and accurate in numerical simulations in the case of different scenarios.