ABSTRACT
In the paper the seismic response of two-dimensional and three-dimensional structures with surface foundation is studied, for the case in which some parts of the foundation may uplift during the earthquake (”unilateral” contact conditions). The analyses are carried out by a computer program based on an algorithm proposed by the authors. Due to the variable support conditions the problem is nonlinear, but at each time step only the unknown displacements at the foundation are considered by using an elimination technique of the internal degrees of freedom. The contact-impact conditions at the foundation are also properly taken into account. A parametric numerical analysis of several 2D and 3D structures under characteristic excitations is carried out. The response of each structure is studied for unilateral and also bilateral (fixed) contact conditions at the foundation. The structures are subjected to static vertical loads in conjunction with the dynamic seismic excitation. Some interesting results and conclusions obtained from the parametric analysis of the seismic response of buildings that may uplift during an earthquake are presented.
