Structural steel framing is an excellent system for providing building structures the ability to arrest collapse in thernevent of extreme damage to one or more vertical load carrying elements. The most commonly employed strategy tornprovide progressive collapse resistance is to employ moment-resisting framing at each floor level so as to re-distributernloads away from failed elements to alternative load paths. Design criteria commonly employed for thisrnpurpose typically rely on the flexural action of the framing to redistribute loads and account for limited memberrnductility and overstrength using elastic analyses to approximate true inelastic behavior. More efficient designrnsolutions can be obtained by relying on the development of catenary behavior in the framing elements. However, inrnorder to reliably provide this behavior, steel framing connections must be capable of resisting large tensile demandsrnsimultaneously applied with large inelastic flexural deformations. Moment connections prequalified for use inrnseismic service are presumed capable of providing acceptable performance, however, research is needed to identifyrnconfirm that these connection technologies are capable of reliable service under these conditions. In addition, somernrefinement of current simplified analysis methods is needed.
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