Sharif Digital Repository

In this paper a new approach to risk based seismic assessment of structures is proposed based on acceptable risk levels. In this approach, the probabilistic seismic vulnerability, predicted lifetime of structure, importance and knowledge factors are considered in the evaluation process. Park & Ang damage index is used to quantify damage states of structure. By performing several incremental dynamic analyses, all damage states of structure from minor to heavy and collapse are considered under all possible ground motions. The structural risk level and the necessity of seismic retrofit measures are specified by seismic risk index of structure. This probabilistic performance based method is... 

Probabilistic seismic analysis of structures with incremental dynamic analysis (IDA) is a widely used method to offer comprehensive evaluation of the seismic performance of structures. Although IDA is a powerful computer-intensive method, it is really a time-consuming procedure. Accordingly, in this study, for coping with this problem, significant motion duration is used instead of total motion duration. This truncation can significantly reduce the computational effort and time. In order to determine the influence of truncation, fragility curves and their mean annual frequencies (MAF) in each limit state are used with two different damage indices, namely modified Park & Ang and maximum... 

There are many parameters utilized to obtain a more reasonable performance for structures under earthquake excitations in seismic provisions. General considered parameters in seismic provisions are: PGA, importance factor (I) and typical inherent overstrength and global ductility capacity (R). It is well recognized that the main characteristic of the design of structures under seismic excitation is probabilistic rather than deterministic; therefore, it should be determined if whether the probability of structural damage decreases when such parameters change in the design of structures. In this paper, fragility curves are developed in order to evaluate these parameters. Fragility curves are... 

Different values have been assigned to the ratio of the deflection amplification factor (Cd) to the response modification factor (R) for a specified force-resisting system in the seismic design provisions while the same application is defined for it. An analytical study of the seismic responses of several reinforced concrete frames subjected to a suite of earthquake records performed in this research indicate that the stories’ overstrength and stiffness distribution along the structural height can affect local deflections more than global ones. Therefore, the Cd/R ratio is calculated based on the ratio of both maximum inelastic to maximum elastic displacements and... 

One of the main challenges in earthquake risk mitigation nowadays is the seismic performance assessment of existing buildings that were not designed according to modern building code standards and the development of effective techniques to retrofit these structures. In this paper seismic performance of an existing 5-story RC frame building which is typical building stock in central region of Tehran retrofitted by three methods (Concrete jacketing, Steel jacketing, CFRP wrapping) is investigated by developing fragility curves. Corresponding Fragility curves are constructed for three structural damage limit states, collapse prevention (CP), Life Safety (LS) and immediate occupancy (IO) and... 

In this paper, a practical method is developed for performance-based design of RC structures subjected to seismic excitations. More efficient design is obtained by redistributing material from strong to weak parts of a structure until a state of uniform deformation or damage prevails. By applying the design algorithm on 5, 10 and 15-storey RC frames, the efficiency of the proposed method is initially demonstrated for specific synthetic and real seismic excitations. The results indicate that, for similar structural weight, designed structures experience up to 30% less global damage compared with code-based design frames. The method is then developed to consider multiple performance objectives... 

In order to estimate the seismic demands at the performance level, the inelastic behavior of concrete structures should be considered. Incremental dynamic analysis (IDA) based on a nonlinear response time history analysis (NL-RHA) is considered to be the most accurate method in seismic demand calculations. However, modal incremental dynamic analysis (MIDA), based on the equivalent single-degree-of-freedom (SDF) oscillator, is also often used in studying structural engineering performances. As the MIDA method has usually not been applied to reinforced concrete (RC) structures, in this study an attempt is made to investigate the performances of RC frames and to compare the results obtained...