Seismic Upgrade of an Existing Tall Building by Different Energy Dissipation Devices

摘要

The Pacific Earthquake Engineering Research (PEER) Center has expanded its Tall Building Initiative (TBI) program to include the seismic performance of existing tall buildings. A 35-story steel moment resisting frame, designed in 1968, and had representative details of buildings between 1960 to 1990 was selected for detailed seismic evaluation in the framework of Performance Based Earthquake Engineering (PBEE). It was identified that the case study building failed to meet the performance objectives suggested by ASCE 41-13, and had a number of seismic vulnerabilities that endangered its structural integrity at two basic safety earthquake hazard levels (BSE): BSE-1E and BSE-2E. Therefore, exploration of retrofit strategies and their cost-effectiveness are fostered. In this paper, three kinds of supplemental energy dissipation devices are investigated to upgrade the seismic performance of the case study building, including fluid viscous dampers (FVDs), viscous wall dampers (VWDs) and buckling restrained braces (BRBs). The retrofit design started by selecting locations to install supplemental devices. Then the total effective damping ratios needed to achieve the target roof displacements in two directions were estimated based on a damping scale factor (DSF). One retrofit strategy by using FVDs was investigated as a first trail, and the mechanical characteristics of each damper device were calculated based on the overall effective damping ratio and the story wise distributions of dampers. Next, other two retrofit strategies by using VWDs or BRBs were investigated. Sizing of different devices at one location was performed following the principle of equal energy dissipation. The effectiveness of each strategy to meet the retrofit intent of ensuring structural stability at BSE-2E were compared. Moreover, probabilistic damage and loss analysis were conducted using Performance Assessment Calculation Tool (PACT) to relate the structural responses to economic losses. After a detailed examination, it was found that upgrading the case study tall building using FVDs was the most effective retrofit strategy to control structural responses, and reduce damage and economic losses after BSE-2E events.