Probabilistic evaluation of seismic design parameters of RC frames based on fragility curves

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 employed for various probability parameters. These diagrams are utilized to demonstrate when a coefficient or a number of parameters are used to improve the performance level of a structure. Moreover, it guarantees that the probability of exceedance of the damage limit state decreases, as expected. These diagrams can further illustrate the effect of uncertainty of design parameters. After introducing fragility curves and the application procedure, the effect of the uncertainty of the PGA is displayed and discussed. The results reveal that by increasing the global ductility capacity (R), the probability of damage exceedance is decreased; however, an increase in importance factor (I) for hospital buildings versus office buildings, cannot guarantee a decrease in the probability of damage exceedance. The PGA randomness results reveal that considering PGA uncertainty does not mean that the probability of damage exceedance will be increased in general cases.