Fiber Beam-Column Model Considering Slab Spatial Composite Effect for Nonlinear Analysis of Composite Frame Systems

A fiber beam-column model considering the slab spatial composite effect for nonlinear analysis of composite frame systems is proposed and implemented in a general commercial finite element (FE) package. A conventional fiber beam-column model of composite beams is first developed and the computational procedure of this model is presented. A hysteretic law which can consider the strength degradation attributable to repeated reversals of unloading and reloading is proposed to more reasonably and accurately trace the actual complex nonlinear behavior of the concrete material. Furthermore, the formulas for calculating the effective flange widths at two critical limit states are combined with the conventional fiber model so that an improved fiber model, which can reasonably consider the slab spatial composite effect, is realized through the modification of the uniaxial constitutive laws of slab reinforcement and concrete. Finally, the simulations of several tested composite frame structures show that the proposed model can reasonably trace the complex slab spatial composite effect of composite frame systems. (C) 2013 American Society of Civil Engineers.