Finite Element Modeling of Cold-Formed Steel Composite Open-Web Joists with Simplified Slab Representation

This study develops and validates a finite element (FE) modeling framework, implemented in ABAQUS, for reliability assessment of composite open-web steel joists (OWSJ), examining four different joist configurations whose top chord, bottom chord, and web members consist of both hot-rolled and cold-formed steel. The joists were modeled using S4R shell elements, while composite action was captured by explicitly modeling the concrete slab and representing the steel deck using simplified rebar elements embedded within the slab. Shear studs were modeled using CONN3D2 connector elements to simulate slip and load transfer between the slab and top chord. Nonlinear geometric and material behavior was included to capture yielding, buckling, and post-buckling response. Model predictions demonstrated strong agreement with available experimental and analytical benchmarks, validating the proposed modeling strategy. The results show that the shell-based composite modeling approach provides an efficient and reliable tool for system-level evaluation and reliability analysis of composite OWSJ assemblies across multiple joist configurations.