Interface forces in composite steel-concrete structure

In this paper a solution to the bending problem of reinforced concrete slabs stiffened by steel beams including creep and shrinkage effect is presented. The adopted model takes into account the resulting in-plane forces and deformations of the plate as well as the axial forces and deformations of the beam, due to combined response of the system. The analysis consists in isolating the beams from the plate by sections parallel to the lower outer surface of the plate. The forces at the interface, which produce lateral deflection and in-plane deformation to the plate, lateral deflection and axial deformation to the beam, are established using continuity conditions at the interface. The creep and shrinkage effect relative with the time of the casting and the time of the loading of the plate is taken into account. The solution of the arising plate and beam problems which are non-linearly coupled, is achieved using the Analog Equation Method (AEM). The adopted model, compared with those ignoring the in-plane forces and deformations, approaches the actual response of the plate-beams system more reliably. Moreover, it permits the evaluation of the shear forces at the interfaces, the knowledge of which is very important in the design of composite steel-concrete structures. The resulting deflections are considerably smaller than those obtained by other models.