FINITE ELEMENT ANALYSIS OF SEMI-RIGID COMPOSITE FRAMES UNDER VERTICAL LOADS

To study the effects of moment-rotation characteristics of connections and load magnitude on the behavior of composite frames, nonlinear finite element method is presented considering the effects of the moment-rotation characteristics of beam-to-column connections, composite action of slab and geometric nonlinearity. The stiffness matrixes of structures and fixed-end forces of members are modified by introducing an end-fixing factor. The results indicate that the moment-rotation characteristics of connections affect the forces and deformations of the composite frames, while the load magnitude has no significant effect in the range of 0.143< r0<0.727. In addition, the effects of semi-rigid connection and composite action of slab on the behavior of steel frames must be properly considered in design. The proposed finite element method can be used in practice.