PRACTICAL NONLINEAR ANALYSIS FOR SEMI-RIGID STEEL FRAMES

Methods for taking into account semi-rigid connection effects in steel frame analysis, and practical models of connection moment versus rotation curve are introduced. A three-dimensional beam-column element, based on refined plastic hinge model, is developed to represent the combined nonlinear effects of geometry, material and connection on the behavior of semi-rigid frames. Second-order effects and shear deformation of the frame are captured through stability functions. Tangent modulus and a parabolic function are used to account for the gradual yielding along the length and across the section. Kishi-Chen power model and the modified beam element method are used to describe the nonlinear behavior of semi-rigid connections. Using the User Programmable Features (UPFs) of ANSYS program, the element routines have been developed and successfully incorporated into ANSYS program. Comparing with experimental results, the proposed element can give reasonably good prediction of the load-displacement behaviour of semi-rigid frames. The analytical results are in accordance with those obtained when connections are modeled by COMBIN39 element.