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SUMMARY The design approach for tall steel moment frame structures with viscous dampers entails sizing steel members per code-level strength forces, and sizing viscous dampers to limit storey drifts. This method has been used extensively in new and retrofi t applications. This methodology has resulted in structures that have longer periods than those using the code-designed approach, are economically competitive and have excellent performance in design-level earthquakes. However, the effi cacy of this design in extreme events is not well understood because of the lack of limit states data for dampers and the absence of a fi eld or analytical database of such structures subjected to large earthquakes. Mathematical modelling of viscous dampers with limit states was developed, correlated with experimental results and then used to analyse 10-storey archetypes. This analysis showed that the design had satisfactory performance during extreme seismic events. There were signifi cant improvements in reducing collapse hazard by using an enhanced damper design with an increased damper safety factor. Copyright © 2010 John Wiley & Sons, Ltd.

Fluid viscous dampers are used to control story drifts and member forces in structures during earthquake events. These elements provide satisfactory performance at the design-level or maximum considered earthquake. However, buildings using fluid viscous dampers have not been subjected to very large earthquakes with intensities greater than the design and maximum considered events. Furthermore, an extensive database of viscous damper performance during large seismic events does not exist. To address these issues, a comprehensive analytical and experimental investigation was conducted to determine the performance of damped structures subjected to large earthquakes. A critical component of this research was the development and verification of a detailed viscous damper mathematical model that incorporates limit states. The development of this model and the laboratory and simulation results conclude good correlation with the new model and the damper limit states and provide superior results compared with the typical damper model when considering near collapse evaluation of structures.