Effect of weld details on the ductility of steel column baseplate connections

Results from six two-thirds scale tests on moment-resisting steel column base plates are presented. The test specimens incorporate Complete joint Penetration (CJP) and Partial joint Penetration (PJP) weld details between the column and the base plate. The test data indicate that both details are resilient to fracture and sustain inelastic column hinging to story drift ratios of 6%-9%, which exceeds the typical acceptance criteria of 4% drift ratio for seismically detailed special moment frames. In five of the six tests, fractures initiated in the Heat Affected Zone (HAZ) at the fusion line between the weld and column flange. In the sixth test, fractures initiated at the inside face of the column flange at the upper edge of the weld access hole of the CJP weld detail. Contrary to the initial expectations, the specimens with the PIP welds exhibited higher displacement ductility than those with CJP welds. This is attributed to the fillet reinforcing that strengthens the PJP welds and enables them to sustain stresses and strains necessary to fully develop yielding in the column flanges. The test data further support the adequacy of the FEMA 350 provisions for determining the required strength of the welds based on the probable moment demand with the material overstrength factor of R-y = 1.1 and strain hardening factor of C-pr = 1.2. (C) 2008 Elsevier Ltd. All rights reserved.