EVALUATION OF THE DYNAMIC ANALYSIS REQUIERMENTS IN THE SEISMIC CODE OF IRAN

The seismic code of Iran (code ۲۸۰۰) requires dynamic analysis, for Buildings over ۸۰ m high, or those with irrigularities in plan. Two accelerograms have been suggested to perform dynamic analysis, ignoring the soil condition and the regional seismisity. The code is not explicit on wether the nonlinear behaviour is allowed, or the structure should be analysed linearly. The results of preliminary linear dynamic analyses indicate that the seismic behaviour depends on parameters such as the yield level and ductility. A dynamic nonlinear program was developed to investigate the effect of ductility on the seismic response of structures. Structures with varying frequency were subjected to the Tabas, Naghan, and Manjil earthquakes. The discrepancy between the results and the static seismic forces were enousmas, and the structures needed high amount of ductilities to stand the real earthquake excitations. For normallu designed structures, the required ductility was calculated. It has been shown that the required ductility for a structure depends on the type of earthquake, the fundamental period of the structure, and the lateral strength at each storey level. As a result of these analyses, ductility spectra were calculated, from which one can estimate the amount of ductility that a building requires when subjected to a particular earthquake.