Development of Steel Moment-Resisting Knee-Braced Frame for Multi-Storey Buildings

Moment-resisting frames (MRFs) are one of the most reliable and widely used structural systems against earthquake and wind loads which provide remarkable ductility capacity. Two types of MRFs, i.e. concrete MRFs and steel MRFs, have been developed and implemented in the construction industry during the past few decades. However, there are a number of drawbacks associated with steel moment-resisting frames, rendering them less popular compared to their concrete counterparts. This is why concrete MRFs dominate in many large Canadian cities such as Toronto, Vancouver, Montreal and Edmonton. First, due to lack of sufficient stiffness, steel MRFs undergo large lateral displacements in case of mid- and high-rise buildings. Second, the labor costs required for welding, weld inspection and erection are high. Moreover, they require pre-qualified complicated rigid connections with Complete Joint Penetration (CJP) groove welds, which makes their construction even more difficult and expensive. In order to provide a solution to the foregoing challenges, this research aims to assess the performance of an innovative steel modular lateral load resisting system, with a particular focus on high-rise buildings in Canadian steel industry. In this system, concentrated rigid connections are replaced with simple shear connections which in turn lead to the removal of CJP welds. Also, sufficient lateral stiffness is provided through application of stocky or buckling restrained knee braces. Modules, typically consisting of a column as long as three stories and beam stubs, are prefabricated in the shop and then carried to the site. It is expected that this modular system will increase the construction speed, while significantly reducing the amount of required labor, welding and weld inspection costs. Furthermore, this system is expected to be successfully implemented in construction of mid and high-rise buildings in Canada.