Inelastic dynamic analysis of tall buildings

The importance of inelastic action of frame structures subjected to strong ground motions has been recognized by engineers for many years. However, the dynamic analysis of buildings undergoing inelastic deformations requires the solution of many theoretical problems, as well as the development of computer software which makes such analyses economically feasible in a design office–in spite of the extraordinary amount of computation involved. In this paper, some of the principal theoretical problems are briefly described. These are the load-deformation relationship, yield capacity reduction, ductility, P– δ effect, viscous damping, panel zone distortions, numerical integration techniques, energy analysis and the effect of non-structural elements. Special consideration is given to questions associated with the practical implementation of this theory. These questions arose during the development of a computer program, called NLDYN, capable of analysing the non-linear dynamic behaviour of tall buildings in an engineering office environment. The capabilities of this computer program are illustrated with the results of the analysis of a 60 storey office building currently under construction in downtown Los Angeles.