STRUCTURAL DAMAGE ASSESSMENT USING RESPONSE MEASUREMENTS (EARTHQUAKE)

A technique is presented to assess seismic damage in existing structures using information readily obtainable from structural response records. Accelerograms are about the only type of response records currently available for real world structures following strong-motion earthquakes. Using the methodology as presented herein, these records are analyzed to estimate the force-deformation response at intervals along the height of the structure. The estimation scheme used in this study fits the response of a spring-mass model of the structure to the structural motions incrementally through time. Advantages of this method include the simplicity of the calculations and the lack of pre-imposed mathematical restrictions on the force-deformation response. Information available in the force-deformation response is used in several damage functions to obtain a quantitative measure of the condition of the structure. A new damage function is proposed and developed for this purpose, that is expressed in terms of the range and number of cycles of inelastic response of the structure during an earthquake. Postulated advantages of this function include simplicity and generality of its application. This function and an existing maximum deformation/cumulative dissipated energy damage function are used to evaluate the condition of several damaged multi-story reinforced concrete test structures. The resulting quantitative measures of structural damage are correlated with descriptive damage classifications of the type: safe, lightly damaged, damaged, and critically damaged. Based on these correlations, the damage functions as used herein produce meaningful measures of the damage condition of the structures. Results from this assessment technique can be used independently or in conjunction with other available information in damage analyses. The practical usage of this assessment technique is demonstrated by using the acceleration records of the Imperial County Services Building. This extensively instrumented 6-story reinforced concrete building was significantly damaged during an actual earthquake. Based on the values obtained for the damage indices discussed herein, the first floor of the structure was judged overall to be lightly damaged after the earthquake. This assessment is reasonable with respect to the physical damage observed in the structure.