On the Method to Evaluate the Post-earthquake State of Collapsed Structures and Its Applications to Numerical Analyses

Devices to control the direction of structural collapse during earthquakes have been proposed in recent years where a rigid block or a chain is placed in between the column and the beam of a structure to asymmetrically accumulate the inelastic response, leading the collapse in the designated direction. The effectiveness of such devices has been verified by numerical and experimental studies, where symmetric simple structures were targeted. To assess the effectiveness of such devices on asymmetric or eccentric structures, on the other hand, an appropriate method to capture their collapsed state is desired. This study proposes a new method to capture the direction of collapse and the amount of deformation of target structures. Moreover, by employing Open Dynamic Engine (ODE), a three-dimensional time-history analysis that can simulate the collapse of structures consisting of rigid bodies, the proposed method is verified. In this method, the structural members are virtually divided into elements based on the unit weight and the movement of each element is measured as the vector before and after earthquakes. The origin of the vectors is then moved to concentrate at the origin to integrate their direction and displacement. The information of the direction is expressed as the percentage of the accumulated masses of the elements normalized by the total mass of the structure while the information of the displacement is shown as the color map. This graphical mapping can render the state of collapse, expressing the direction and displacement in a simple manner. The proposed method is applied to the results of the time-history analysis in case of structures with and without the collapse direction control devices, which successfully shows the quantitative differences between them. This method is a promising tool to evaluate the state of the collapse of various types of structures.