Fracture Mechanics-Based Design of Column Splices with Partial Joint Penetration Welds

Abstract

Design standards in the United States mandate the use of complete joint penetration (CJP) welds for welded column splices (WCS) in high-seismic regions. However, recent experiments suggest that economical partial joint penetration (PJP) welds (which have a cracklike flaw) provide acceptable performance if high-toughness materials are used with large weld penetration. To generalize these findings, a fracture mechanics-based method is proposed for the seismic design of WCS with PJP welds. In support of the design method, four scientific components are presented: (1) finite element fracture mechanics (FEFM) simulations that simulate 25 WCS connections; (2) design equations based on results of the FEFM simulations; (3) Monte Carlo simulation to characterize the uncertainty in the strength determined by the design equations; and (4) reliability analysis to calibrate resistance factors that provide acceptable levels of safety. Trends in the resulting resistance factors and component reliabilities are discussed, and the variability in WCS strength arising from modeling uncertainty (i.e., due to regression fitting of design equations) is determined to be dominant. Simplified guidelines for prescriptive design of WCS connections with PJP welds are presented. In addition to the proposed design equations and resistance factors, a major outcome is the demonstration of a flaw-tolerant design approach based on fracture mechanics. Limitations of the approach are discussed.