Abstract:
Cold-formed steel sections used in floor systems are vulnerable to web crippling, and with increasing span
lengths, they are likely to fail under combined web crippling and bending action. A numerical study was
therefore undertaken to investigate the combined web crippling-bending interaction behaviour of unlipped
channel sections used as bearers in floor systems with fastened supports. Web crippling finite element models
developed and validated by the authors in a recent study were extended to investigate the behaviour of unlipped
channels under combined action of web crippling and bending while new finite element models were developed
for bending and validated using available experimental results. All three types of finite element models were used
in a detailed parametric study to obtain the capacities of 12 unlipped channel sections made of G250 and G450
steels under pure and combined web crippling and bending actions. Comparison of the combined web crippling
and bending capacities obtained from finite element analyses with the interaction equations in three cold-formed
steel design standards, AISI S100, AS/NZS 4600 and Eurocode 3 Part 1.3, showed that the current design
equations are accurate for 50 mm bearing length. However, they can also be used to predict the combined web
crippling-bending capacities conservatively for bearing lengths of 100 and 150 mm. A new design equation with
a suitable capacity reduction factor was then proposed to improve the accuracy of predicting the mid-span load
capacity of channel sections subject to combined web crippling and bending actions.
