A force-based model for composite steel-concrete beams with partial interaction

This paper presents a new force-based beam-column element for the nonlinear analysis of composite steel-concrete beams with partial interaction. The element is made up of three components: (a) a fiber beam-column element that models the behavior of the steel girder, (b) a fiber beam-column element that models the behavior of the concrete deck, and (c) a bond element that models the transfer of forces between the steel and concrete elements through shear connectors. The model neglects uplift and frictional effects. The fiber beam-columns are force-based elements that depend on force interpolation functions. A linear bending moment and a constant axial force serve as the interpolation functions. An important factor that favors the use of force-based elements in modeling composite structures is their ability to treat any type of distributed element loads. Distributed element loads are applied internally in a continuous manner by force superposition at the control sections. The state determination of these elements is based on an iterative solution that determines the element resisting forces and stiffness matrix. The bond element is a spring-type element that assumes a linear bond stress variation along the length. The nonlinear behavior of the composite element derives entirely from the constitutive laws of the steel, the concrete and the shear connectors. The paper concludes with a correlation study to investigate the validity of the model. Good agreement between analysis and experimental results was observed.