Abstract:
This thesis aims to find a new weld sizing criterion for the steel construction industry in
New Zealand. Current standards, such as NZS 3404, ANSI/AISC 360-16, and Eurocode 3 use a
factor of 0.6 to calculate weld capacity from the weld metal’s ultimate tensile strength (UTS).
This difference between weld capacity and UTS is thought to have arisen from the need for a
large factor of safety to ensure welds perform correctly during an earthquake. The events in
Christchurch proved that this criterion was able to work as intended.
Several papers have been published by P. Dong from University of Michigan, and
alongside other researchers, they investigate a new definition of weld shear strength by using a
traction stress-based method. This new method not only allows realistic angles of weld fracture
to be investigated, but also different weld geometries such as partial penetration butt welds.
Ongoing research at HERA is showing how this welding technique is a more economical option
than larger fillet welds with similar performance.
For this thesis a range of sample types were statically tested until failure. UTS of several
weld metals was found and then compared with transverse shear results to see if 0.6 is indeed
correct. It was found that if the results from the standardized transverse shear samples was used,
this ratio could be increased to 1.0. But if the results from cruciform joint samples was used,
which still load the weld in a transverse direction but with a higher stress concentration, required
the ratio to be 0.8 for welds that could be welded with a single pass, and decreased further to
0.75 for large welds with 3 passes.
Two types of partial penetration butt weld (PPBW) geometries were compared to a
comparatively sized fillet weld. These tests showed the PPBWs were the best performers, with
all PPBWs surviving testing compared to only 33% of fillet welds.
