Design of cold-formed stainless steel channels undergoing web crippling

Abstract

The web crippling failure of cold-formed steel members occurs primarily due to concentrated bearing loads. There have been many investigations on this typical failure, especially for structures fabricated from carbon steel. The results of these investigations have been incorporated into the recent web crippling design provision for cold-formed carbon steel (CFCS) in the current American Iron and Steel Institute (AISI) Standards (2016). In contrast, the web crippling design provision for cold-formed stainless steel (CFSS), as found in Australian/New Zealand (AS/NZS) Standards (2001) and American Society of Civil Engineers (ASCE) specification (2002), are not based on experimental investigations. Instead, they are extensions of a CFCS specification. Unfortunately, the incoming ASCE (2021) that will replace the ASCE (2002) still incorporates the web crippling design provision from AISI (2016) for areas such as channel sections.

Several studies have evaluated the current web crippling design provisions in AS/NZS (2001), ASCE (2002), and Eurocode 3 (EC3) Part 1.4 (2015). Those studies mainly focused on CFSS hollow sections and a few other cross-sections fabricated from a single SS grade. So far, there has been no study investigating plain channel sections fabricated from various stainless steel (SS) grades concurrently. Moreover, the previous studies examined the web crippling design of different SS grades separately. Unlike the past studies, this study simultaneously investigated the web crippling that occurs in CFSS plain channels made from various SS grades.

The web crippling investigation in this study comprised 196 experimental tests and 1904 numerical simulations. The tested specimens were fabricated from austenitic (EN 1.4404) and lean duplex (EN 1.4162) SS grades. Six loading cases obtained from the literature were considered, various flange restraint conditions were implemented, and the effect of a web hole located concentric to the load-bearing plate was also examined.

The results obtained from the experimental tests were used to validate the numerical simulations, which confirmed their accuracy. The experimental and numerical investigation results were compared with the existing and the proposed web crippling design rules. Results obtained from other studies were incorporated into the assessment of design rules. Based on the reliability analysis, the proposed web crippling design rules applicable for various SS grades considered in this study are more conservative and reliable than the existing design rules.