Web crippling design of cold-formed high strength steel SHS and RHS at elevated temperatures

Abstract

This study investigates the web crippling capacities of cold-formed high strength steel (CFHSS) hollow structural section members at elevated temperatures. A numerical investigation on square and rectangular hollow sections (SHS and RHS) undergoing web crippling was performed at various temperatures from 21 °C to 1000 °C. Finite-element (FE) models were firstly developed to replicate the available web crippling tests on CFHSS SHS and RHS members. After validation, extensive parametric studies with 784 specimens covering all four codified web crippling load cases in the current cold-formed steel design specifications were performed. The reductions of web crippling capacities at elevated temperatures were compared against the corresponding yield strength and elastic modulus reduction factors of the materials. The suitability of available web crippling design provisions in current codes of practice and literature to CFHSS sections at elevated temperatures was evaluated. Comparison results reveal that the direct strength method (DSM) previously proposed by the authors at ambient temperature could be extended to elevated temperature conditions and would provide rather consistent and reliable predictions than other existing provisions. A modified DSM is put forward in this paper and it is found that the modified DSM is suitable for web crippling design of the CFHSS sections at both elevated and ambient temperatures, and moreover, can also be used for cold-formed stainless steel SHS and RHS of various grades. Therefore, the modified DSM is recommended to be used for web crippling design of CFHSS and stainless steel SHS and RHS at elevated and ambient temperatures.