Investigation of the flexural strength of cold-formed steel C-section using computational and experimental method

The use of cold-formed steel (CFS) as structural materials has gained popularity because of its high strength-to-weight ratio. In the Philippines, the demand to use it as structural member has increased recently. However, verification of its actual strength is not extensively studied in the country. CFS as a structural member is usually required to be designed as ductile. However, it was discovered in the initial phase of the study that CFS with higher strength but with brittle behavior is also being commercially distributed in the country. The objective of this study is to investigate the flexural strength of CFS made of these steel materials with the use of computational and experimental method. The computational method covers the calculation of the theoretical flexural strength based on the NSCP provisions while the experimental method covers the actual flexural strength based from the four-point bend test. A total of 24 specimens of back-to-back C-sections of different thicknesses and lengths were tested. Additional finite element modelling (FEM) was also conducted using ANSYS. The main failure modes were distortional (DB) and lateral-torsional buckling (LTB). For the ductile CFS, DB and LTB were observed in 86.1% and 13.9% of specimen population, respectively. While for the brittle CFS, DB and LTB were observed in 75.0% and 25.0%, respectively. Moreover, it was also found that the NSCP strengths were lower than the experimental strengths. The FEM results were close to the experimental results thus validating the experimental results. It was determined that a modification factor of 0.60 can be used for the brittle CFS NSCP strength to achieve similar results as the ductile CFS