Dynamic Analysis and Behavior of Infilled Frames Under Seismic Loading

Abstract eng:
-This paper presents a numerical method based on a straight forward linear finite element response spectrum method for the analysis of infilled R.C.C. frames subjected to earthquake excitation. The Finite element method has been used to develop stiffness matrix and consistent mass matrix of infilled frame.Finite Element Method(F.E.M.) is more correct method of analysis of infilled frame than equivalent strut method which has traditionally been used by most of the researchers for analysis of infilled frames. Consistent mass matrix is diagonalized by using Hinton E., Rock T. and Zienkiewicz O.C.( H.R.Z.)method[25] as diagonal mass matrix derived from consistent mass matrix is more sophisticated than a lumped mass matrix. This type of diagonal mass matrix gives more accurate mode shapes and the frequencies of structure. The stiffness matrix and diagonal mass matrix are put into dynamic equation of motion and this dynamic equation is solved by using a subroutine based on Jacobi’s iteration method. By solving the dynamic equation, eigen values and eigen vectors are obtained. These eigenvalues and eigenvectors are used in response spectrum method of analysis to calculate seismic loads (one vertical, one horizontal and a moment) at each nodal points. These seismic loads are then applied on each node and principle stresses at gauss points and deflections at nodal points in infill panels are obtained by static analysis. The above procedure is implemented into a computer program which is developed by the author using Fortran-77 This program has been used to solve 17 cases of bare and infilled frames ranging from three story to seven story in order to assess the effect of different factors such as the presence of infill panels, the height of structure, infill material, panel thickness, rectangularity ratio. Results show that infill panels have a great effect on the behavior of structures.

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