ABSTRACT
In the 1994 Northridge and 1995 Kobe earthquakes, traditional welded rigid beam-column connections used in steel moment resisting frames (MRFs) suffered premature brittle fracture in the beam to column flange welds. Alternative systems such as the “dog bone” localized beam reduction system (Roeder 2002) have since been developed, which typically avoid weld failure by forcing plastic hinges to form in the beam away from the column face to dissipate energy through ductile deformation. While effective in providing safety and preventing collapse, they are associated with irrecoverable plastic deformation causing heavy economic losses both in the post-disaster repair, and downtime due to building closure and business interruption. Downtime costs may often exceed the direct costs associated with physical damage. The economy of a society can thus be severely disrupted with long lasting effects, particularly in highly developed regions. As a consequence there has been a shift towards low damage systems, which not only prevent collapse, but enable restoration of full functionality following a major earthquake with minimal repair required. Among the systems currently under research are post-tensioned steel tendon (Herning et al., 2009), and shape memory alloy systems (DesRoches et al., 2010).
