Ground Motion Prediction Equation for Optimal Combination of Spectral Displacements as the intensity measure for short-period buildings using Iranian strong ground motion records

Important parameters of strong ground motions in a site in terms of potential damage to structures can be represented by an intensity measure parameter. One of the intensity measures that is widely used in the quantitative representation of earthquake intensity in earthquake engineering is the spectral acceleration at the first-mode period of the structure. Recent studies have shown that the use of this parameter as an intensity measure may lead to high dispersion in predicting the nonlinear response of buildings. For this purpose, using intensity measures with higher sufficiency and efficiency has been received attention in recent years. One of these intensity measures that has been proposed in recent research is the optimal combination of spectral displacements. Approximately, the first-order Taylor series expansion can be used to derive an attenuation relationship for this intensity measure based on the existing relationships for spectral accelerations. However, the derivation of an independent attenuation relationship for this intensity measure in order to reduce the calculation error is inevitable. For this purpose, a ground motion prediction model was proposed for this intensity measure. In developing the attenuation relationship, more than five hundred and fifty pairs of accelerograms were used, which were recorded in 284 earthquakes with a magnitude of 4 to 7.6 and at distances of less than 100 km in different regions of Iran. The proposed model has been investigated by examining the residual values against magnitude and distance as well as its application in comparison with other attenuation relationships.