Web crippling experiments of high strength lipped channel beams under one-flange loading

Abstract

Web crippling is often a critical design problem in cold-formed steel flexural members. Lipped channel beams (LCBs) are commonly used as floor joists and bearers in the construction industry and are often subjected to concentrated loads. Design capacity predictions from most of the cold-formed steel design standards such as AISI S100 [1], AS/NZS 4600 [2] and Eurocode 3 Part 1-3 [3] are empirical, developed based on past experimental studies. They were found to be either unconservative or conservative in most cases. Inconsistencies in design capacity predictions are considered to be due to the fact that the specimen length and support conditions pertaining to the test set-up varied among past experimental studies. In 2008, American Iron and Steel Institute introduced a standard test method for conducting web crippling studies [4]. However, limited web crippling studies have been conducted to date for LCB sections under EOF and IOF load cases. Therefore a detailed experimental study consisting of 36 tests was conducted to investigate the web crippling behaviour of high strength cold-formed steel LCB sections under EOF and IOF load cases based on the AISI web crippling standard test method. This paper presents the details of this experimental study of LCBs unfastened to supports, using which it proposes suitable modifications to the current unified web crippling design equation. It also presents suitable direct strength method based design equations and associated predictive equations for elastic bucking and yield loads of LCBs under EOF and IOF load cases.