Robustness of light steel frames and modular construction

The robustness or structural integrity of light steel framing and modular constructions is important because these are relatively new structural forms, in which the components have different forms of inter-connectivity in comparison with primary steel frames. There is an increased need to understand the sensitivity of these forms of construction to so-called accidental actions, including terrorist threats. Various forms of construction using light steel and modular technologies are identified and their implications for robustness are reviewed. A series of stressed skin tests on modular constructions is presented. These show that modules are able to span as deep beams with one longitudinal support removed with minimal displacements, indicating that the torsional stiffness of the ‘box’ provides a high level of robustness. Removal of a corner support again demonstrates the role that torsional action of the box plays in redistributing loads away from damaged sections of a structure. For light steel framing, multiple inter-connections provide robustness by tying action and alternative load paths in the event of one or more elements being severely damaged. For modular construction, a scenario-based approach is required in which modules are selectively removed and the horizontal and vertical forces in the connections between the modules can be calculated explicitly.