Evaluation of the changes in the structure’s dynamic properties on the seismic forces during the vibration process

Abstract

The aim of this research paper is to study the changes occurring in the structure dynamic properties during the vibration process and its effect on the values and distributions of seismic forces in order to obtain the real behavior of the structure under the impact of seismic loads. The proposed method is based on the method of normal forms, the method analyzes the structure during the period of vibration according to specific time steps and determines all the changes occurring in the structure. A reinforcement concrete frame was studied according to the proposed method and the results were compared with the method of pushover. The results shows that due to the changes in the dynamic properties of the structure, different values and distribution of seismic forces are obtained at every moment in time, eventually the end seismic behavior and collapse mechanism are different from the results predicted from other seismic analysis methods, which depend on an elementary distribution of the forces depending on the vibration modes of the structure in the elastic stage. The proposed method provided the possibility of accurately calculating seismic forces and seismic behavior of the structure beside performing seismic analysis using real soil motion diagrams.