Modeling the effects of residual stresses on defects in welds of steel frame connections

• Published in: Engineering structures Vol. 22; no. 9; pp. 1103 - 1120
• Main Authors: Matos, C.G, Dodds, R.H
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Ltd 01.09.2000; Elsevier
• Subjects: Applied sciences; Building structure; Buildings; Buildings. Public works; Construction (buildings and works); Eigenstrains; Exact sciences and technology; External envelopes; Finite elements; Joints; Metal structure; Residual stresses; Stress-intensity factors; Stresses. Safety; Structural analysis. Stresses; Welding; Finite elements; Residual stresses; Welding; Eigenstrains; Stress-intensity factors; Metallic structure; Structural design; Eigenmode; Geometrical properties; Frame construction; Stress strain; Connection crossing; Finite element method; Three dimensional model; Stress intensity factor; Numerical simulation; Beam column structure; Weld defect; Residual stress
• ISSN: 0141-0296; 1873-7323
• DOI: 10.1016/S0141-0296(99)00055-3

This work describes an eigenstrain approach to impose realistic residual stress fields on 3-D finite element models for the lower-flange welds of the type found in large, beam-column connections. The 3-D models incorporate the full geometry of a pull-plate specimen designed to reduce the cost of testing full connections while retaining essential features of the fracture prone, weld region. The 3-D analyses examine pull-plate configurations with a variety of geometric parameters for both through-width and semi-elliptical cracks in the weld root pass. The numerical results include tables of values for the non-dimensional “geometry” factors ( Y) needed to compute stress intensity factors. The residual stress fields generated by the proposed eigenstrain functions closely match those computed using 2-D, thermo-mechanical simulation of the welding process. Stress intensity factors, obtained from corresponding J-integral computations, show clearly the significant fracture toughness demand from residual stresses prior to application of the structural loads. An alternative design for a grooved backup bar shows considerable promise to reduce fracture toughness demands by re-positioning the weld root pass below the beam flange and thus outside the primary load path. Analyses here indicate approximately a 65% reduction in K I -values for tension loading in the flange.