EVALUATION OF DESTRUCTIVENESS OF EARTHQUAKE MOTIONS BY COLLAPSE BASE SHEAR COEFFICIENT SPECTRA

The evaluation of destructiveness of earthquake ground motions is one of the most important subjects in the field of earthquake engineering. Peak ground acceleration (PGA) or velocity (PGV) has been used to evaluate the intensity of ground motions. Response spectra have also been used to get more information about the relationship between structural response and ground motions. However, they often do not correlate well with the structural damage. Therefore other methods taking into account the inelastic behavior of structures are proposed, e.g. elasto-plastic response spectra, evaluation taking into account of energy concept. An effective and general method, however, has not yet been found. In this paper, we propose a collapse base shear coefficient Cc and a Cc spectrum (Cc vs. T ). In order to estimate Cc, the structure is idealized as a SDOF system considering P-∆ effect. The Cc is the maximum yield base shear coefficient when the model structure collapses because of the P-∆ effect and the collapse is assumed to happen when the rotation angle reaches π/2. The Cc spectrum shows a good accordance with the damage extent of structures caused by many previous earthquakes.