13 th World Conference on Earthquake Engineering Vancouver, B.C., Canada August 1-6, 2004 Paper No. 1708 GUIDELINES FOR SEISMIC ASSESSMENT OF DAMAGED BUILDINGS Paolo BAZZURRO 1 , C. A. CORNELL 2 , Chuck MENUN 3 and Maziar MOTAHARI 4 SUMMARY Structural post-earthquake functionality is conventionally evaluated by trained engineers via visual inspection of the damage. A building is tagged “Green” (unrestricted access), “Yellow” (restricted access), or “Red” (no access) according to the severity of the observed damage. Whether the damage implies an actual decay in safety level of the building occupants during aftershocks is essentially left to judgment. We propose to use engineering analyses performed prior to an earthquake to determine the level of degradation in building safety implied by several different damage states. We use the loss of capacity (in ground motion terms) associated with each damage state as the quantitative measure of degradation. The likelihood that an aftershock will exceed a specific (reduced) capacity provides an objective criterion for assigning the appropriate tagging condition to that damage state. This knowledge can help engineers decide on the appropriate occupancy status should a given damage state be observed during an inspection after an earthquake. This methodology has another practical application. The same engineering analyses can also identify the level of mainshock ground motion expected to produce any damage state. Because a damage state can be associated with a tagging condition as explained above, this procedure also identifies the mainshock ground motion level that is expected to drive the intact building into a given tagging condition. Hence, after appropriate consideration of uncertainty in building response and capacity, one can use this information to develop fragility curves for green, yellow, and red tags, and for collapse of the intact building. A convolution of such fragility curves with the building site seismic hazard provides an estimate of the frequency of future building access restrictions and collapse. Such information is valuable when estimating the likelihood of loss of functionality of a critical facility or downtime of a building for expected loss estimation purposes. INTRODUCTION A few references are available in the literature (e.g., ATC-20 [1], and FEMA 352 [2]) that present procedures for post-earthquake evaluation of buildings. In all the cases post-earthquake decisions regarding short-term occupancy of buildings rest solely on engineering judgment exercised by professionals that visually inspect the facility in the aftermath of the damaging event. So far little 1 Manager Engineering Analysis, AIR Worldwide Co., 388 Market Street, Suite 610, San Francisco, CA, USA. E-mail: pbazzurro@air-worldwide.com 2 Professor, Dept. of Civil and Environmental Engrg., Stanford University, Stanford, CA, USA 3 Assistant Professor, Dept. of Civil and Environmental Engrg., Stanford University, Stanford, CA, USA. 4 Former Ph.D. Student, Dept. of Civil and Environmental Engrg., Stanford University, Stanford, CA