Numerical and analytical methods for the design of beam-column sub-assemblies with composite deck slab

Abstract

A finite element numerical model is used to estimate the force displacement backbone curve of steel moment frame beam-column-joint subassemblies tested at large scale under repeated cyclic loading with different composite deck slab configurations. The slab configurations included: no-slab; fully isolated slab; two configurations for detailing the slab near the region between the column flanges; and a full depth reinforced slab. Then, a simple analytical model was developed so that designers can estimate the likely peak strength due to slab effect. This analytical model considers the common deformation modes and the strength hierarchy. It was found that the finite element numerical model captured the backbone envelope of experimental tests done on different slab configurations for the bare frame, isolated slab and full depth slab configurations, but overestimated the strength at larger displacements for the other configurations due to difficulty in considering the slab modes of failure. The simple analytical model considered the nonlinear deformation modes of steel beam plastic hinging, concrete crushing both outside the column flange and within the beam flanges, slab shear fracture between the column flange tips, slab longitudinal and lateral reinforcement yielding as it carried the subassembly moments and transferred forces between the steel frame and the slab, and shear stud deformation. The proposed analytical model matched the experimental strengths and failure modes. The proposed finite element model is suitable for research, and the analytical model matched the experimental results, and is suitable for consideration in design.