Nonlinear Deformation Identification during Occurrence of Earthquake in Steel frame Structures utilizing Time-Frequency Method

摘要

In high risk earthquake-prone regions, it is very probable that a structure collapses after experiencing some moderate earthquakes, although it can tolerate each of earthquakes separately. Main reason of this incident would be occurrence of minor damage resulting from cumulative effects of earlier earthquakes. In steel structures, nonlinear deformation may happen during yielding event. In spite of the other events related to damage like complete demolishing of an element or occurrence of sever cracks in concrete structures, identification of yielding event by comparing characteristics of structure before and after earthquake is impossible. Furthermore, the response of such structure is combination of nonstationary excitation and nonlinearity behavior of structures. In this study, using acceleration response of the structure analyzed by time frequency method, an innovative Nonlinear Deformation Index (NDI) has been developed to show this kind of nonlinearity. Results show that identification of nonlinear behavior would be practical utilizing prescribed NDI.