A UNIFIED MATRIX APPROACH FOR NONLINEAR-ANALYSIS OF STEEL FRAMES SUBJECTED TO WIND OR EARTHQUAKES

An efficient nonlinear approach is presented in this paper in matrix f orm for the analysis of the static and dynamic response of steel frame s subjected to horizontal loads arising from wind or earthquakes. This approach is particularly suitable for developing a computer program f or evaluating ultimate capacities of buildings in steel frames. The st iffness matrix equations for basic elements of steel frames are first outlined in the paper. The effects of geometric nonlinearity, material nonlinearity and shear deformation are considered in the proposed sti ffness matrices for beam and column elements. Next, the stiffness equa tions of the extended column elements with panels attached and extende d hybrid beam elements attached to both connections and panels are est ablished to consider the effects of shear deformation of panels and fl exibility of beam-to-column connections. Then the nonlinear behaviour of an arbitrary steel frame with flexible connections and deformable p anels can be analysed by simply assembling all the stiffness matrix eq uations of the panel elements, extended column elements and extended h ybrid beam elements of the frame to form the overall stiffness equatio n of the entire frame. Finally, the robustness, accuracy and efficienc y of the proposed approach are demonstrated through several numerical examples.