The AISI Direct Strength Method for Cold-Formed Steel Design:A Practicing Engineer's Introduction

Thin cold-formed steel (CFS) structural members in building construction can be designed using one of several approaches: the "effective-width" plate buckling concept, the Direct Strength Method, or through implementation of a full finite element analysis. While a finite element analysis gives the most complete picture of member behavior, the effort involved in its use and implementation often limits its use to academic or forensic applications. Traditionally, CFS members have been designed using the effective width approach, but the development of the Direct Strength Method (DSM) represents an exciting new tool for use in determining cold-formed steel member capacity. As the steel building industry adjusts to DSM and finite strip analysis, knowledge of how members are analyzed and how strength is determined using this process is critical in giving the practicing engineer the tools to judge the appropriateness of a given computer-based solution for the actual conditions. The goal of this paper is to introduce the practicing engineer to the concepts behind finite strip analysis and show how its results are employed in determining strengths using the Direct Strength Method.