Finite Element Models for Thin-Walled Steel Member Connections

The behavior of connections associated with the thin-walled steel members is distinctly different from that of hot-rolled steel connections, primarily because of the flexibility of the plates. A typical cold-formed steel structural construction may entail such numerous connections. The incorporation of large number of such connections in an analysis and design, using sophisticated finite element models, is very tedious and time consuming and may present computational difficulties. The objective of this investigation is to create simplified, yet reasonably accurate, finite element models for the analysis of screw connections and bolted connections associated with thin-walled sheet steel construction. The primary plates were modeled using quadrilateral shell elements, and nonlinear stress-strain relationship was established based on experiments. The fasteners were modeled as an elastic medium. The plate-to-plate interactions and the plate-to-screw interactions were incorporated using contact elements. The study considered two finite element models of different complexity. The performance of these models was established through comparisons with the corresponding experimental results. The finite element analysis results exhibit reasonably good agreement with the test results in terms of connection stiffness, screw tilting, end curling, and average longitudinal strain. The recommended simplified connection model is capable of reproducing the behavior of sheet steel screw and bolt connections. 1. Introduction Welding and mechanical fastening are the two most common types of connections in steel construction. Though thin-walled steel members, such as cold-formed steel structural members, may be welded together, mechanical connections are convenient and economical and, thus, are widely used in light-weight steel construction. The mechanical fasteners may be screws, bolts and nuts, blind rivets, short pins, and so forth. Figure 1 shows a sample of thin-walled sheet steel lap connection that is under consideration in this paper. The behavior of screw connections and bolt connections associated with the thin-walled steel members is distinctly atypical primarily because of the flexibility of the plates. Tilting of fasteners in the hole, pullover of the screws, distortion of the sheet metal around the hole in tension, and so forth contribute to this distinction as well. Previous studies [1–5] on such screw connections and bolted connections experiencing various failure modes were experimental investigations as well as finite-element-based numerical analytical