Behavior of screw connections in sheathed cold-formed steel walls

Abstract

This paper presents a study on the behavior of screw connections in sheathed cold-formed steel (CFS) walls. A finite element (FE) model with solid elements was developed to investigate different failure modes. Suitable solution techniques, element types, mesh sizes, screw modeling, and geometric and material non-linearity were considered in model development. Since the behavior of the sheathing boards is similar to that of other quasi-brittle materials, the Concrete Damage Plasticity (CDP) model was used to model the material behavior using both classical plasticity and continuum damage mechanics. Uniaxial experimental tests were performed on fiber-cement board samples to define material parameters used in the CDP model. The load displacement behavior, ultimate strength, and failure modes obtained from the developed FE model were validated against available experimental results on walls sheathed with cement or gypsum boards. The validated FE model was then used to perform parametric study to investigate the effect of different design parameters on the connection behavior. These parameters are: board type and thickness, CFS profile thickness, screw diameter, screw length, and edge distance. The results of the parametric study were used to develop a design equation for the screw connection strength using nonlinear regression analysis.