Assessment of the seismic performance of structures designed based on uniform ductility pattern

Abstract

In seismic design procedure, the idea of considering uniform inelastic behavior for all stories displaces materials from unnecessary locations to stories needed for damage reduction and leads to a more economic design. In this paper, a parametric study was done to assess the seismic performance of structures designed based on uniform ductility pattern. For this purpose, three artificial records whose response spectrums were matched to the codified design spectrum, were considered. Using an iterative procedure, the tuned strength patterns were obtained for a number of models with various natural periods, ductility ratios, behavior coefficients and stiffness distributions. It can be seen that the strength of stories corresponding to uniform ductility pattern decreases in all stories in comparison with distribution recommended by Standard-2800 especially for middle stories and the total strength of structures as a weight index decreases. Also, a new equation was developed by regression analysis to determine the coefficient of story strength. Assessment of the performance of the structures with tuned story strength distribution under real ground motions showed less dispersion for ductility pattern in comparison with structures which were designed according to Standard-2800. Also, it was seen that if the amplitude of the earthquake response spectrum is larger than the design spectrum, the dispersion of the ductility values over the stories increases significantly. The situation becomes critical for lower stories when the amplitude of the earthquake response spectrum is larger than the design spectrum at periods higher than the fundamental period of the structure. D D