STRENGTHENING NEEDED TO IMPROVE THE SEISMIC PERFORMANCE OF COLLAPSE AT THE SITES OF TEHRAN
Keywords:Performance levels, collapse, strength, site, nonlinear analysis
One of the performance levels of residential buildings is to avoid the global collapse of the building against maximum ground excitations. However, some common regulations for designing such structures, especially those that design such structures with force approaches instead of performance ones, do not require structural control at this level. Due to such issues, the need to increase the rigidity of the structure to control the performance levels mentioned in the structure is considered necessary. In this study, using the analytical approach, through incremental dynamic analysis, the nonlinear behavior of 4 moment frames in both intermediate and special ductility is estimated, then using fragility curves corresponding to the levels of collapse performance, fragility curves are plotted. Then, using the empirical approach and considering the difference in hardness of the four frames according to their pushover curve, the median and deviation changes from the criterion of nonlinear analysis response criteria, for each difficulty, are plotted. In the next step, for 6 different sites in terms of geotechnical and seismicity, probabilistic evaluation was performed to identify sites that have a higher probability of collapse than the acceptable level for these frames. For collapsible frames, the stiffness changes required to reduce the probability of structural collapse to an acceptable extent have been calculated according to the obtained curves. The results show that in the northern and southern constructions of Tehran, short rise intermaediate moment frames to provide protection against the possibility of collapse against maximum ground excitations should provide an increase in earthquake hardness of about 35% through permitted methods.