Modeling Slab Contribution in Frame Connections

Abstract

Contribution of monolithic floor slabs to the negative (hogging) flexural resistance of beams in reinforced concrete frames may inadvertently affect the hierarchy of failure unless it is considered during the design. A qualitative model simulating participation of slabs to the behavior of beams is developed by establishing the kinematic relations between beam deformations and the state of strain in the slab. The slab is idealized as a membrane element by using a network of rigid links and flexible springs connecting the slab bars to the supporting beams. Support displacements of the rigid links, such as reinforcement slip, twist, weak axis rotation, and elongation of the transverse beams are considered. Reasonable correlation of test data from interior and exterior slab-beam-column subassemblies is possible. The computed responses were most sensitive to the assumed length of plastic hinge, and to a lesser degree, to the distribution of longitudinal strains within the plastic hinge. In the range of low deformations, results are somewhat sensitive to the assumed initial transverse beam stiffness. Available expressions for establishing length of plastic hinge seem sufficient. © ASCE.