A direct performance based seismic design method for irregular structures

Abstract

The problem of designing structures to achieve a specified performance limit state has gain interest in seismic design practice. Currently, some methodologies have been proposed in order to take into account for inelastic behavior of the structures in design phases; in that sense, a performance limit state can be provided. However, most of these approaches are iterative processes and depend, in some cases, on the experience of the designer. Otherwise, they are based on the concept of equivalent structures, only adequate for regular structures. In this paper, a direct performance based seismic design methodology for irregular structures with damage control is proposed. This method is based on the superposition of two elastic analyses. The strength of the method is the selection of local damage regions (hinges) intentionally chosen by the designer. This distribution of hinges defines the zones where damage is allowed and the desired failure mechanism in the design. A combination of dynamic modal-spectral analyses using a damage parameter (¿) to control the damage intensity in the plastic hinges and the non-structural damage through allowable displacement or drifts. The methodology will be presented for planar frame structures presenting vertical irregularities. Furthermore, the effects of higher modes of vibrations is highlighted.