Modeling issues in nonlinear dynamic finite element analysis of steel-concrete composite frame structures subjected to seismic excitation

Frame finite element models permit obtaining, at moderate computational cost, significant information on the dynamic response behavior of steel–concrete composite (SCC) frame structures. As an extension of conventional monolithic beam models, composite beams with deformable shear connection were specifically introduced and adopted for the analysis of SCC beams, in which the flexible shear connection allows development of partial composite action influencing structural deformation and distribution of stresses. The use of beams with deformable shear connection in the analysis of frame structures raises very specific modeling issues, such as the characterization of the cyclic behavior of the deformable shear connection and the assembly of composite beam elements with conventional beam–column elements. In addition, the effects on the dynamic response of SCC frame structures of various factors, such as the shear connection boundary conditions and the mass distribution between the two components of the composite beam, are still not clear and deserve more investigation. The object of this paper is to provide deeper insight into the natural vibration properties and nonlinear seismic response behavior of SCC frame structures and how they are influenced by various modeling assumptions.