The Effect Of Infilled Walls On Seismic Behaviors Of RC Frame Structures

Reinforced concrete infill wall frame structure can provide larger space for activities and has always been widely used in multi-story building in our country.Conventionally,infill wall,as the non-structural component,does not bear horizontal load,but all the study of seismic damage shows that the infill wall interacts with frame structure.Therefore,we should focus on the interaction between infill wall and frame structure,not simply considering the infill wall as non-structural component.Combined with the previous studies,the main work of this paper is as follows:(1)In the background of a six-story reinforced concrete infill wall frame structure,according to the principle of equivalent stiffness,different models of the infill wall based on the equivalent diagonal bracing were established.Through the modal analysis,comparing the pure frame structure with the infill wall frame structure,we could explore the rationality of current standard for the period reduction coefficient of the frame structure.(2)Different models of infill wall were analyzed by using response spectrum analysis and time-history analysis.Under frequent earthquake,infill wall could provide large lateral stiffness and effectively reduce the lateral displacement of the structure.It also bore most of the horizontal load and played a good effect of energy dissipation.Under seldom earthquake,the stiffness effect of infill wall were decreased,but the infill wall could still bear a part of the horizontal load and control the lateral displacement of the structure to some degree.Vertical irregular arrangement of infill wall highlighted the weak layer of the frame structure,which did great harm to aseismic design.(3)Pushover analysis was conducted on the pure frame structure and infill wall frame structure.Through the distribution and development of plastic hinge on the beam and column,the infill wall effectively restrained the development of plastic hinge.But plastic hinge rapidly developed on the floor without infill wall,which aggravated damage of the weak layer.According to analyzing the performance point of the three vertical irregular arrangement of infill wall models,we got the most unfavorable arrangement.(4)Improvement program was proposed for the most unfavorable arrangement.Through observing the interlayer displacement angle,performance point and plastic hinge of the models,the effectiveness of Improvement program was verified by applying nonlinear time history analysis and pushover analysis.(5)The effects of different Infill wall materials on seismic performance of frame structure were investigated.The results show that the light-weight infill wall occupies obvious advantages on controlling displacement of the structure under the elastic analysis and the light-weight infill wall shows good seismic performance on the vertical irregular arrangement of infill wall.Under rare earthquake,the heavy brick wall caused the frame structure to bear more horizontal load.Once the infill wall is damaged,the pure frame structure will dissipate all the energy by deformation,which also does great harm to aseismic design.Therefore,the selection of light-weight infill wall material is more consistent with the concept of seismic fortification.