| Steel-concrete composite structures have been widely used in the past decades because of the benefits of combining the two construction materials. With the rapid growth in application of composite systems, the need for reliable analysis and design tools is more evident. Design of composite structures using the limit state philosophy requires a thorough understanding of inelastic behavior. This is especially true in seismic design since structures are expected to respond inelastically during a strong seismic event. However, the inelastic behavior of composite members and systems is not yet well understood, and design provisions for composite structures have generally been extrapolated from provisions for traditional reinforced concrete or steel structures (for example, ACI-318 1995 and AISC-LRFD 1993).; Composite decks, consisting of reinforced concrete slabs and steel girders are well known examples of modern composite constructions. Partial restraints at the interface of the concrete slab and the steel girder have significant effects on the strength and stiffness of the composite decks. The present work considers the nonlinear analysis of frame structures with composite floor systems. Due to the significant effect of deformable shear connectors on the behavior of composite beams, the study is mostly focused on developing new composite beam elements capable of accounting for this effect. The study has lead to developing finite element models for reinforcing bars with partial connection, as well.; Three different composite beam elements are presented, including displacement-based, force-based and Hellinger-Reissner mixed finite elements. The elements consist of two beam components connected by an interface. The interface, which is idealized by a continuous spring model, is introduced to account for the effect of deformable shear connectors. Several numerical studies are carried out to compare the performance of the force-based element with that of the displacement-based element. Numerical results demonstrate that the force-based element is far more accurate than the displacement-based element. |
