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- Type of Document: M.Sc. Thesis
- Language: Farsi
- Document No: 53781 (09)
- University: Sharif University of Technology
- Department: Civil Engineering
- Advisor(s): Bakhshi, Ali; Kashani, Hamed
- Abstract:
- The development of the methods to evaluate the seismic resilience of communities, infrastructures, and structures has attracted many researches. To estimate the resilience with accuracy, developing a model that can simulate the events during the recovery time is very important. For the same, modelling the aftershocks with their accumulative effects on the damaged buildings during the recovery time has been the main focus of the current study. The proposed approach to simulate the aftershocks’ effect utilizes the Monte-Carlo sampling, in which each sample includes the two following steps. The first step is the simulation of the cumulative damage caused by the mainshock-aftershocks sequence before any repairing operation. At the second step, the repairing operations and the aftershocks’ effect during repairing time will be considered. This step will be terminated when the building is completely recovered. Each sample starts with the main-shock occurrence generated by a hazard model, which is developed based on the Synthetic Stochastic Earthquake scenario predictive model. In each sample, one of the faults is activated based on the normalized occurrence rate, while the probability of rupture is considered uniform along the activated fault. The starting rupture point is considered as the place where the mainshock happens. Then, based on the mainshock characteristics, the aftershocks’ number, moment magnitude, and occurrence time are obtained. The case study model is a typical model of Tehran’s’ schools 4 stories buildings, that has steel braced frame. The building’s structure is modelled 3 dimensionally using PERFORM 3D software. In this model the braces have nonlinear behavior. The peak drift ratio, peak floor velocity, and acceleration for each building's principal direction are determined as a demand parameter after each event. By using the fragility curves developed in FEMA P-58, the probability of each damage state for all components of the structure will be obtained as a function of demand parameter. The economic loss is then determined based on the description of each damage state and the operations required to recover the damaged components to the intact condition. In the second step, the sample continues by simulation of the operations to repair the structure during the recovery period. It is assumed that aftershocks occur after the structural repair has been finished; however, in the case of repairing non-structural elements, the residual time to the next aftershock should be considered. The functionality function used to determine the resilience is developed based on the ratio of economic loss to the replacement cost. In this study, the effect of aftershocks has been considered in the recovery period, then the functionality of the building and resilience loss factor has been calculated for three scenario groups. The first group has 18 aftershocks that 7 of them occur before repair starts on day 100, and the mean of moment magnitude for mainshock is 5.3 Richter. In the second group, the total number of aftershocks is 25; 6 of them occur in the first 100 days, and the third group has 30 aftershocks that 3 of them occur before repair starts. In the second and third groups, the mean of moment magnitude equals 5.8 and 6 Richter, respectively. The results indicate that when the aftershocks are considered in the analysis, the building's functionality decreases before the repair. It is found that the increase in the aftershocks numbers and their intensity leads to decrease in the building's functionality. For all groups, neglecting the aftershocks' effect can lead to a 70% error in the structure's value of functionality before repair starts. Moreover, the mean recovery time approximately exceeds twice of recovery time without consideration of aftershocks. Among the three groups of components that could affect the building's total loss, the non-structural groups have the most considerable contribution. The resilience loss factor is equal to 0.16 when only the mainshock is applied to the building. In contrast, if the effects of aftershocks are incorporated in the analysis, this factor increases to a value of 0.21, indicating a 30% increase in the building's loss factor
- Keywords:
- Aftershocks ; Probabilistic Modeling ; Fragility Curve ; Resilience Index ; Repairing ; Recovery ; Resilience Enhancement
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