مهندسی عمران شریف (Aug 2019)
OPTIMAL PERFORMANCE-BASED SEISMIC DESIGN OF SHEAR BUILDINGS USING ENDURANCE TIME METHOD
Abstract
Recently, with progress in earthquake engineering and design of structures, the performance-based seismic design is becoming more popular. However, finding the optimum structure that satisfies the performance limitation of this method is a hard task. In this study, the applicability of endurance time method in optimal performance-based design is evaluated using uniform deformation theory. First, shear building structures are optimized for a set of records, representing a specified seismic hazard level using time-history analysis and uniform deformation theory. This is done for a different number of stories ranging from 5 to 15. In addition, different target ductilities are used for uniform deformation procedure ranging from 1 to 8. Sets of ground motions used in this study are obtained from the SAC project and represent different seismic hazard levels. The results show that the optimized structure for a specific seismic hazard level does not necessarily show appropriate performance at other seismic hazard levels.However, the performance of optimized structures for another set of ground motions with the same seismic hazard level is satisfactory. Consequently, using a try-and-error process, the structure's performance is improved to a certain extent; however, it is not yet ideal and also the stiffness of the structure increases. This process is time-consuming and insufficient for engineering application. Therefore, endurance time method is utilized to find optimal structures with a proper performance at different seismic hazard levels. ETA40g acceleration functions are used since they are more compatible with the ground motions used before. The results of endurance time method are compared with those obtained for ground motions. It is shown that the results of endurance time analysis are consistent with those obtained from time history analysis of the set of records. Distribution of story shears and deformations are compatible in two methods. Finally, an effective technique is presented in which the structural performance is simultaneously improved at all seismic hazard levels.
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