New design rules for lipped channel beams subject to web crippling under two-flange load cases

摘要

Lipped channel beams (LCBs) are commonly used as floor joists and bearers in the construction industry. These thin-walled LCBs are subjected to specific local and global failures, one of them being web crippling. Several experimental and numerical studies have been conducted in the past to study the web crippling behaviour and capacities of different cold-formed steel sections under different concentrated load cases. However, due to the nature of the web crippling phenomenon and many factors influencing the web crippling capacities, capacity predictions given by most of the cold-formed steel design standards are either unconservative or conservative. Therefore a detailed experimental study was conducted to study the web crippling under End Two-Flange (ETF) and Interior Two-Flange (ITF) load cases based on the new AISI 5909 standard web crippling test method. Finite element models were developed and validated using the test results. These models were then used in a detailed parametric study to investigate the web crippling capacities of a wide range of LCB sections including different sectional geometric parameters such as section depth, inside bent radius, thickness and bearing length. This paper presents the details of the numerical study of LCBs subject to web crippling under ETF and ITF load cases. Using the extensive web crippling capacity data obtained from both numerical and experimental studies, improved unified web crippling design equations were developed. Suitable web crippling design rules were also developed under the direct strength method format.