Structural behaviour of improved WUF-B joints with longitudinally profiled plates

Abstract

In this paper, an improved type of beam-to-column joint was proposed to enhance the material efficiency and structural behaviour of typical welded unstiffened flange-bolted web (WUF–B) joints, where the thickness of the flange on the beam was varied using longitudinally profiled (LP) plates. LP plates are plates manufactured to various thickness along the rolling direction to optimise their design under different loading distributions. Three full-scale beam-to-column WUF-B joints with LP plates were designed and tested under cyclic load. Different thickness change ratios and lengths of the variable thickness were considered in the specimen design. The obtained moment-rotation curves and the failure modes of the specimens were reported. Compared with a conventional WUF-B joint, it was found that the moment capacity of the joints can be significantly improved as a consequence of higher material efficiency. As WUF-B joints tend to fail from brittle weld metal fractures, micromechanical fracture model of cyclic void growth model (CVGM) was incorporated in the numerical models developed herein to predict the joint failure. A subsequent parametric study was carried out, considering a range of LP flange lengths and thickness change ratios as an extension of the tests. It was found that designing the improved WUF-B joints with a short LP flange length and a high thickness change ratio can enhance the plastic rotation capacities and avoid brittle failure.