Behaviour of Beam-to-tubular Column Connections under Extreme Loading Conditions

Abstract

Whilst the moment-rotation behaviour of typical connection configurations has been extensively examined in previous studies, there is a relative lack of information on the performance under more generalised loading conditions, particularly in relation to semi-rigid connections to tubular columns. To this end, this research aims to provide fundamental information that would enable an extension of the assessment and design of semi-rigid tubular column connections to loading scenarios involving significant axial or shear actions. In particular, the thesis focuses on the behaviour of two cost-effective semi-rigid open beam-to-tubular column alternatives: i) blind-bolted angle connections and ii) reverse channel connections with angles. The work involves experimental investigations, detailed numerical simulations and analytical studies, as well as application-oriented studies. Firstly, two experimental investigations that are concerned with the behaviour of beam-to-tubular column connections under predominant axial and shear loads respectively are presented. The experimental set-up, connection configurations and material properties are introduced followed by a detailed account of the results and observations from the tests. The main behavioural patterns are identified and their effect on the connection performance is discussed. Subsequently, detailed three-dimensional finite element models are constructed by means of the nonlinear program ABAQUS, and their results are validated against the experimental data obtained in this research in addition to that provided from previous bending tests conducted at Imperial College London. Complementary component-based mechanical models for both blind-bolted and combined channel/angle connections are also suggested and described. Various component characteristics including tension and compression load-displacement relationships as well as load-displacement expressions in shear are proposed. The findings offer information which is of direct relevance to strength prediction in conventional design procedures, as well to more involved characterisation of stiffness, capacity and ductility for modelling and assessment purposes, particularly under extreme loading conditions. In the concluding part of the thesis, the component-based models are employed, together with detailed finite element simulations, to illustrate the applicability of the proposed connection models under a number of possible load combinations involving bending and/or shear actions. As an example of application of the suggested models in frame analysis under extreme loading, selected frame and beam simulations are carried out under idealised pseudo-static conditions representing column removal and floor-on-floor collapse situations. Finally, the findings of the thesis are summarized and a number of possible future research areas are highlighted.