Effect of seismic sequences on fragility of Iranian code-conforming shear wall RC buildings

Estimating the vulnerability rate of urban textures in seismic incident following a major earthquake (aftershocks) is crucial in decision making and crisis management. For this purpose, it is necessary to calculate the vulnerability of buildings due to the successive incidents and to use them in the vulnerability estimation for probable future aftershocks. Seismic fragility in reinforced concrete buildings with shear wall affected by a secondary incident due to seismic continuity is calculated in this paper.

The studied buildings have 4, 8 and 15 floors. Opensis software was used for nonlinear analyzes. For this purpose, twenty seismic sequences which presented in previous valid studies were used. Seismic fragility curves to collapse level following increasing nonlinear time history analysis were estimated; for this, numerical models of studied constructions following the first incident damage were analyzed.

According to the results, in addition to present the seismic fragility of reinforced concrete sheets with shear wall and the effect of the first incident amount on this parameter, the changing process of this index due to Iran 2800 Standard Change in three recent editions has been studied; the results showed that the probable demolishing of studied frames affected by the second incident, is significantly increased if the frame were damaged in first incident.

It is essential to consider the aftershock impacts on damaged structures under the first incident in order to risk management and decrease the damages. The results of this study showed that increasing the amount of demolishing due to main earthquake the probability of the structure collapse will increase significantly following the aftershock. On the other hand, recent editions of Iranian seismic guidelines in choosing design method, has a significant impact on the reduction of aftershock damages.