Inelastic Vibration Phase Theory for Seismic Pounding Mitigation

Abstract

Pounding between closely spaced structures can be a serious hazard in seismically active metropolitan areas. One of the key issues is estimating the required separation distance to avoid or reduce pounding of adjacent structures that vibrate either elastically or inelastically. Series of dynamic time history analyses can estimate this distance by obtaining the maximum relative distance of the adjacent structures. However, this paper proposes an alternative and more attractive method, called the “spectral difference (SPD) method,” based on a spectrum approach. The method accounts for phasing associated with vibration of adjacent structures, defined as “vibration phase.” The paper also proposes simplified rules to predict the inelastic vibration phase, and demonstrates the accuracy of the SPD method for a variety of adjacent building pairs and earthquakes. Unlike the time history analysis method, the SPD method clarifies the effects of various parameters on the relative displacement through a closed-form solution. The SPD method is also useful for various relative displacement problems between adjacent structures, such as bridges. It is more accurate than the current code calculation method that ignores the vibration phase.