School of Civil and Environmental Engineering

Ph.D. Thesis Defense Announcement

EFFECTS OF MULTIPLE WELD REPAIRS ON A709 STEELS

By MATTHEW L. PHILLIPS

Advisor:

DR. RYAN J. SHERMAN

Committee Members: DR. DONALD WHITE (CEE), DR. LAUREN STEWART (CEE), DR. EDVARD BRUUN (CEE), DR. SHUMAN XIA (ME)

Date and Time: March 30, 2026. 2pm EST Location: SEB 122 / Virtual Link

ABSTRACT
Welding is used extensively throughout steel bridge fabrication. Considerable care
is taken to ensure the welds are sound, but rejectable defects are occasionally
identified during fabrication and must be repaired, with some requiring multiple
repair attempts to resolve. Currently, there is no limit on the number of repair welds
allowed before a member is rejected, leading to concerns about the behavior and
longevity of repaired joints and potentially costly disputes between owners and
fabricators over the acceptance or rejection of members containing repaired joints.
The objective of the current study is to determine the effects of multiple weld repairs
on the material properties and fatigue life of complete joint penetration (CJP)
welded joints made from A709 Grades 50W and HPS70W steels. An experimental
program comprising material characterization and fatigue testing has been
developed to accomplish the objective. Material characterization tests were
conducted on plate specimens that were welded and repaired between zero and five
times. Large-scale flexural fatigue tests were conducted on built-up members with
3/4" and 1-1/2" thick flanges that have multiple butt-splice CJP welds that have been repaired between zero and five times. The material characterization tests showed
that the number of weld repairs has little effect on the ductility, yield/tensile strength,
and impact energy of the joint, with all joints meeting the strength requirements of
the steel bridge industry. The fatigue tests showed no discernible trend between the
fatigue life of the joint and the number of weld repairs, and all joints met or exceeded
the design-life predictions from AASHTO and displayed scatter similar to that
observed in historical data. Ultimately, the findings from this dissertation indicate
that no repair weld limits should be imposed for material property or fatigue life
concerns; however, repair weld limits required for quality control purposes should
still be considered.