Seismic retrofit of a high-rise steel moment-resisting frame using fluid viscous dampers

The Tall Building Initiative project of Pacific Earthquake Engineering Research Center has been expanded to investigate the seismic performance and possible retrofit of existing tall buildings. A candidate 35-story steel building with representative details from the early 1970s was analyzed following several guidelines, which revealed a wide range of potential inadequacies. Thus, a two-level retrofit approach was examined that focused on achieving the collapse prevention limit state under the major basic safety earthquake (BSE-2E) hazard level prescribed by ASCE 41. This paper focused on a Level-2 retrofit that used fluid viscous dampers to augment Level-1 retrofits. For this approach, feasible damper locations and overall effective damping ratios were first evaluated through a series of preliminary studies, and then a two-phase design method was used to refine the distribution and mechanical properties of the dampers. Thorough assessments of the refined design were carried out following several design guidelines, including ASCE 41, FEMA 351, and FEMA P-58. The results indicated that the proposed retrofit method of using fluid viscous dampers could achieve the retrofit goal and provide a cost-effective means of improving the structural behavior and reducing economic losses in a major seismic event.