Curvature Method to Detect Location and Depth of a Plastic Zone in Frame Members during an Earthquake

This paper presents a new method for detecting beam and frame damage caused by an earthquake. Despite comprehensive investigations on structural damage detection, which mostly have focused on damage detection of elastic structures, the present study deals with nonlinear damage detection in structures. Furthermore, in the proposed method, only measurements of the damaged structures during an earthquake are required and the measurement of undamaged structure is redundant. The proposed method is based on the use of curvature of beams in order to detect plastic zones. To evaluate the efficiency of this method, the beams with different boundary conditions and mass distributions as well as a one-bay singlestory moment frame were modeled in OpenSees software and exposed to the accelerations of Cape, Chichi, and El Centro earthquakes. The curvature vectors calculated using data from acceleration recording points were utilized to detect the place and severity of the damage. Furthermore, in an attempt to reduce costs of actual damage detection, the number of accelerometers were reduced using the cubic spline method of interpolation. Finally, an experimental study was operated to show the effectiveness of the proposed method to determine the length and depth of plastic zones with reasonable accuracy.