Seismic Response Analysis Of Infilled Frame Structure Based On Observation Of Strong Aftershocks In Wenchuan Earthquake

The infilled frames are the common structure system. Existing researches show that the infilled walls have great influences on the capacity, stiffness and deformation Behavior of the frames. It is unsafe to ignore the effect of the infilled walls, So it is necessary to take the effect of the infilled walls into account in the seismic design of the frame in the building structures.Infilled walls as non-structural components of construction, its existing change property index of frame. Under earthquake, because of existing infilled walls, lots of earthquake failure modes which are different from bare frames happened.This paper took certain infilled frame which encountered 5.12 Wenchuan earthquake and strong aftershocks as an example, and made observation results of Ms 6.4 strong aftershocks as reference datum, seismic response analysis was done in four different finite element models. Made comparisons between results of numerical simulation analysis and observation results of Ms 6.4 strong aftershocks, to find a proper finite element model, and discussed reduction factor of structural period in Seismic Design Code. Some conclusions could provide reference for design and analysis of infilled frame structure.(1) Observation of strong aftershocks. Observation of Wenchuan strong aftershocks response was made for infilled frame which locates in Sichuan Kuangshan Machinery Group Corporation in Jiangyou County, 37 observation data of strong aftershocks were attained, including the largest Ms 6.4 strong aftershocks that happened on twenty-fifth,May,2008.The paper combined with observation data of strong aftershocks, Author described seismic damage of the infilled walls, and analyzed related reasons and failure mechanism.(2) Considering effects from infilled walls, finite element models were determined, and made observation results of Ms 6.4 strong aftershocks as reference datum. The simplified models of four kinds of infilled frames are compared and are made evaluation. According to structural fundamental period of the real frame, to modify structural models, therefore suggestion of modified formulas was given. The finite element models are built according to the modified frame mode.(3) The stiffness effect induced by the infill walls makes the natural period of the frames decrease, which makes the earthquake forces put on the structures increase. The modification coefficient of the natural period will directly effect the reaction of the reinforced concrete frames under the earthquake. Comparison periods of models, author discussed reduction factor of structural period in Seismic Design Code, suggestion of modification coefficient of the natural period was given.(4) Considering infilled walls and frame work together, seismic response analysis of the models was made, explored the seismic performance in infilled wall and frame work together. Infilled walls increase global stiffness of infilled frame, when it encounters earthquake, infilled walls will be damaged firstly, the infilled walls become the first seismic defense line of the infilled frame. Inputing observation data of Ms6.4 strong aftershocks to make time history analysis, floor drift, floor shear force and floor stiffness of infilled frame are larger than bare frame under the same working conditions, it demonstrates that infilled walls also have a bad effect on frame structure.