optimal retrofit level

Several types of steel-framed structures now require seismic retrofitting as a result of changes in their usage or modifications in seismic codes. During the last two decades, viscous dampers have been widely used for seismic rehabilitation of buildings because of their ease of application and significant reductions in structural response. The main objective of this research is to present a new comprehensive design process for seismic rehabilitation with non-linear viscous dampers and to introduce the concept of Optimal Retrofit Level (ORL) to control steel buildings. In this article, the inter-story drift as an important parameter of structural response is employed to estimate the failure cost and determine the limit state. Three-, nine- and twenty-story benchmark buildings are used to evaluate the proposed methodology. These buildings have considerably different dynamic properties. The earthquake records corresponding to three levels of seismic hazard are also applied for time-history analysis in order to investigate the trustworthiness of results obtained for zones with different seismicity. The numerical results indicate that the suggested method is able to drop lifecycle costs and creat an equilibrium between rehabilitation costs and failure costs after seismic rehabilitation.