To study fatigue of defective welds, beam-column joints were cyclically loaded at MWD Central Laboratories. However, local buckling occurred in the beam
flanges during the first few cycles at displacement ductilities 2.25-2.6. Despite the buckling, the peak resisted load had a maximum of 15% reduction after 10 cycles at these ductilities, and the hysteresis loops showed little change
in shape. Nevertheless, because steel frame structures can be expected to sustain a ductility demand of about 4/SM or 6, there is clearly some doubt as to whether the strength of a system already buckling at a DF < 3 would be maintained under
the design earthquake. The 310 UB 40 beam tested complied with the current NZ Steel Code, which required no stiffeners in this case.