Research On Seismic Response Of Light-Steel On Frame Structure

Adding-stories technology is a good measure to expand housing area. At present, the technology of light steel adding-stories is gradually becoming an extensively applied form in reinforcement and reconstruction of buildings. In this thesis adding-stories reconstruction project of a four-storey frame structure office building is analyzed with ANSYS software. It emphatically analyzes the structure inherent property before and after adding-stories and the displacement variation under excitations of the earthquake waves, which has important reference value and practical significance to rebuild similar structures with adding-stories.To reflect dynamic variations of structure better, this thesis gives the method of choosing seismic waves correctly, based on actual site classification. As a basic parameter structure dynamic analysis, damping has a great influence on the veracity of structure dynamic analysis results. Therefore, According to the relevant information, it identifies the damping ratio value of steel structures with adding stories, proves that using Rayleigh damping in structures with adding light-steel stories is practical, and comes to the calculation formula of damping parameters.This article carried on the modal analysis to frame structure and whole structure after adding steel stories, which obtained inherent characteristics such as structural frequency. The results showed that the first three mode shapes of frame structure controlled the biggest earthquake response of structure, but from the forth to fifth mode shape could not be ignored, so at least five mode shapes are concerned in structure analysis. The natural vibration period of whole structure become longer than original frame structure and it has some functions to the earthquake. Three mode shapes of whole structure were very close to that of frame structure, so its vibration mode depended on vibration mode of frame structure. Then based on structure inherent characteristic the time history analysis of structure was made. The results showed that under three earthquake waves maximum displacement of whole structure after adding-stories was bigger than that of original frame structure, and it appeared at later time. The displacement increase of adding-stories structure was larger than that of the front four floors.The connection position between frame structure and adding-stories structure became weak layer, which are the weak and strengthened part in seismic design.