The effects of viscous dampers on the reliability of steel structures using a PIF index

Abstract

A new comparative performance measure based on a structure's seismic fragility curve is introduced. This factor, called the performance improvement factor (PIF), was used to compare the seismic performance and reliability of two structures. Using the PIF, the efficiency of viscous dampers on the behaviour of a weak mid-rise steel structure was investigated. A prototype five-span 12-storey steel frame was equipped with three patterns of viscous dampers and their seismic performance was studied. The distribution of dampers along the height of the structure was optimised in three hazard levels using a genetic algorithm and the structure was subjected to 12 ground motion records scaled to levels of 50%, 10% and 2% probability of exceedance in 50 years. The objective function of the optimisation process was defined to achieve immediate occupation, life safety and collapse prevention performance levels at each of the three considered hazard levels. The performance of the primary and rehabilitated structures was investigated using fragility curves and the PIF. A larger PIF indicates a more effective improvement in seismic performance and structural reliability. The results indicate that the suggested method is an effective approach to study and compare the seismic reliability of steel structures.