Sustainable applications of cold-formed steel structures: portal frames

This chapter considers the analysis and design of cold-formed steel portal frames. A literature review of tests on cold-formed steel joints is first presented. The requirement in beam idealization for cold-formed steel portal frames to take into account both the semirigidity and the finite connection length is shown through comparisons against full-scale test results. In the case of joints formed through the web, a reduced strength as a result of the bimoment in the section is demonstrated. For practical small-sized frames, however, serviceability design is more important, to avoid tearing of the cladding at the gable end frames caused by load returned to the gables as a result of stressed skin. The effect of stressed-skin action for portal frames with small spans is shown. For such frames, a three-dimensional stressed-skin frame analysis should be used for design purposes. Finally, performance in fire conditions is described, suggesting the potential advantages of fire protection to the side rails.