EARTHQUAKE DAMAGE ASSESSMENT FOR RC PIERS BY TIME-FREQUENCY ANALYSIS CONSIDERING ENTIRE BRIDGE

Abstract

In this study, the previously proposed earthquake damage assessment method for reinforced concrete (RC) piers was verified through seismic response analysis of an entire bridge. The method measures the acceleration histories at the bottom and top of the pier during earthquakes to estimate the ratio of the initial natural frequency to the lowest natural frequency during earthquakes using time-frequency analysis since it is related to earthquake damage. The previous study verified the method through numerical analysis and shaking table test results of a single pier. However, since the actual pier is connected to the adjacent pier and abutment via the girder, it is important to consider the dynamics of the entire bridge. Therefore, this study verified the method through numerical analysis of the entire bridge. It was found that the method can detect damage to each pier when accelerations in the bridge axis direction are used because the natural frequency only changes for a damaged pier. On the other hand, the method cannot detect which pier is damaged and can only detect if any piers are damaged when accelerations in the direction perpendicular to the bridge axis are used since the natural frequency changed even for undamaged piers. It was verified that the difference between the two directions was caused due to the constraint conditions of the bearings.