Numerical Investigation of Cleavage Fracture in Welded Connections of Steel Moment Resistant Frames

"This study applies an advanced micro-mechanics model of cleavage fracture in ferritic steels to examine the behavior of welded, moment resistant steel frames of the type widely constructed prior to the 1994 Northridge earthquake. The Weibull stress model for cleavage, coupled with 3-D analyses of connections containing crack-like defects, provides a quantitative estimate of the cumulative failure probabilities with increasing beam moment. The 3-D models incorporate the complete geometry of a welded joint (access holes, shear tabs, continuity plate, weld geometry, backup bars). A set of previously conducted, 15 full-scale tests on T-connections of the pre-Northridge design (A36 beams, A572 columns, E70T-4 welds, backup bars left in place) provide fracture moments to calibrate parameters of the Weibull stress model. This study initially considers quasi-static loading typically imposed in large-scale testing of the connections. Once calibrated, the model is used here to examine the importance of welding induced residual stresses in the lower-flange weld, the effects of stronger (A572) beams and modified access hole geometries, and a variety of proposed changes in the weld detail (backup bars, fillet reinforcements). The model predicts the cumulative failure probability for these various configurations. Using this same approach, the simplified ""pull-plate"" specimen is examined from a fracture mechanics viewpoint as a suitable replacement for full connection testing to evaluate alternative welding details. The study concludes by investigating the increased probability of cleavage fracture due to dynamic loading rates of the levels expected during a strong seismic event."

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Civil Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Matos, Carlos Gustavo

Contributors dc:contributor

• Dodds, Robert H., Jr.

• Engineering, Civil

Language dc:language

eng

Identifier

(MiAaPQ)AAI3023138

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/83167