Experimental studies of lipped channel beams subject to web crippling under two-flange load cases

Lipped channel beams (LCBs) are commonly used as flexural members such as floor joists and bearers in the construction industry. These thin-walled LCBs are subjected to specific buckling and failure modes, one of them being web crippling. Despite considerable research in this area, some recent studies have shown that the current web crippling design rules are unable to predict the test capacities under end-two-flange (ETF) and interior-two-flange (ITF) load conditions. In many instances, web crippling predictions by the available design standards such as AISI S100, AS/NZS 4600 and Eurocode 3 Part 1-3 are inconsistent, i.e., unconservative in some cases, although they are conservative in other cases. Hence, experimental studies consisting of 36 tests were conducted in this research to assess the web crippling behavior and capacities of high-strength LCBs under two-flange load cases (ETF and ITF). Experimental results were then compared with the predictions from current design rules. Comparison of the ultimate web crippling capacities from tests showed that the design equations are very unconservative for LCB sections under the ETF load case and are conservative for the ITF load case. Hence, improved equations were proposed to determine the web crippling capacities of LCBs based on the experimental results from this study. Current design equations do not provide the direct strength method (DSM) provisions for web crippling. Hence, suitable design rules were also developed under the DSM format using the test results and buckling analyses using finite-element analyses.