The design which considering the safety and the economicalrespect of structure during earthquake is required of the comprehension of inelastic dynamic behavior of structures. But, we must make an investment in much time and effort for analysis of inelastic dynamic behavior of structures. So, many study has been carried out for searching more simple model of inelastic behavior of structures.
In this study, inelastic dynamic analysis of plane steel frame which is subject to gravity load has been carried out. As a result, large gravity load is forced to make plastic hinges not only both end span but also midspan. It has been proved that one must consider the plastic hinge of midspan in order to represent the collapse mechanism and dynamic response of structure accurately.
