Abstract :
[en] Adjacent buildings subjected to seismic excitations collide against each other when the separation distance is not large enough to accommodate the displacement response of the structures relative to one another. As shown by field observations and by numerical models, seismic pounding can cause severe damage on the affected structures. While these undesirable effects can be prevented by providing adequate separation distances, implementation of generous separations is not possible in metropolitan areas because of maximization of land usage. First, an extensive review of the current state-of-the-art on pounding and on mitigation with a connector linking adjacent structures is made. The only conclusion shared by the researchers is that the effect of pounding on the response of the structure is a very complex one, depending on various parameters of the structures and the characteristics of the ground motion. Due to high complexities of the pounding problems, assumptions have to be made. Most of the researchers have used single-degree-of-freedom systems but this model cannot represent the formation of a storey mechanism or the impact between slab and column. Another assumption generally made is to model linear structure. However, the author found that when pounding occurs, a structure entering in the plastic domain cannot generally be adequately represented by an elastic model.Various assumptions and restrictions are applied to these models. Non-linear direct time history analyses are realized with three artificial accelerograms. The problem has been reduced to a two-dimensional one. The interaction between soil and structure has been neglected. The structures studied have been designed according to Eurocodes [EC8, EC2] for a peak ground acceleration of 0,4g, 0,25g and 0,10g. Beams and columns are idealized as distinct elements and all inelastic deformations are considered concentrated at their two ends (point hinge models). Contact points are known a priori and located at each slab of the buildings. The Kelvin model, a spring and a dashpot used in combination with a gap element, is used in SAP 2000 program to simulate the pounding phenomenon.The pounding effects are first studied. The study concerns adjacent structures having same and different total height and (non)aligned floor levels. It was found difficult to give rules to anticipate the response of the adjacent buildings. This is due to the complex but necessary non-linear behaviour of pounding and structures. In short, pounding amplifies the displacements and the shear action effects of the impacted buildings. These effects can lead to serious damage caused by P-Delta effects or by shear brittle failure. As expected, pounding phenomenon is found to be very dangerous for buildings having non-aligned floor levels.The second part of the work studied the use of connections between adjacent buildings. The study consists in exploring problems and solutions in order to provide guidance to designers. Following the numerical simulations, a practical guide is presented to assist engineers in the choice of the adequate type and properties for the reconnection with reference to the characteristics of the structures submitted to pounding and to their stand-off distances.
