Full-range behaviour of double web angle connections

Abstract

This paper presents recent experimental and analytical investigations on the full-range flexural behaviour of double web angle connections. Experiments were carried out on bolted double web angle connections with two different configurations featuring three and five bolt rows, respectively. For each connection configuration, five nominally identical specimens were tested to investigate the variability of connection behaviour, including joint stiffness, ultimate resistance and ductility, thereby making a total of ten tests. All tests were conducted well into the post-ultimate range until complete failure of the connection, examining the full-range connection response. The load transferring mechanism of the connection was dynamically changing, partly because the presence of bolt hole clearance caused certain bolts to be initially inactive, only to later become active in transferring load from the beam, and partly because when the beam bottom flange came into contact with the column flange under large connection rotation, the centre of rotation changed causing the compressive load transferred at the bottom bolt rows to unload and reverse. To capture the above complicated changes of load transferring mechanisms and thus capture the full-range behaviour of a bolted web angle connection, an advanced mechanical model was proposed. The model is based on the Component Method, and adopts a decision tree to track the evolution of the load-transferring mechanism of the connection, including the bearing state of each bolt, either under tensile or compressive load, the potential presence of contact between the beam bottom flange and the column flange, and the plastic deformation of the critical connection components. The proposed model was applied to the tested connections with excellent agreement observed between the model predictions and the experimental results. Not only producing full-range force-displacement curves that are very close to the experimental curves, the proposed model also provides useful information about the internal state of the connection, which was not obtainable from the tests.