The role of beam-to-column connection in the prevention of progressive collapse of steel-frame buildings

Abstract

The results of an investigation into the characteristics of catenary action and their effects on structures are reported here. There are five aspects presented in this thesis: a literature review on progressive collapse and beam-to-column connections; an exact analysis of catenary action of truss; nonlinear finite element analyses of different post-column removal performance as a function of the original and retrofitted beam-to-column connection geometries; comparison of different behaviours of different beam-to-column connection geometries; and the minimisation of the strengthening plate weight for the retrofitted structures. This thesis demonstrates that when a column is removed, the bending moment will decrease significantly as the catenary tensile force and the plastic deformation increase in the beams connected to the damaged column. This thesis also shows that when a column is destroyed by a blast, the failure strain will be reached at the simple beam-to-column joint. To enhance the survival capability of the steel framed structures subjected to terrorist blast, retrofitting schemes were proposed for strengthening the joints of tall steel framed structures, ensuring the full development of catenary action. This thesis simulates the post-column removal behaviour of the original and the strengthened structures by means of the ABAQUS finite element package. For this purpose, sophisticated two- and three-dimensional models of catenary action are developed. Through comparing different results of the original and the strengthened structures from a column removal, the advantages of the proposed retrofitting schemes have been demonstrated. This thesis investigates the relative advantages and shortcomings between two different retrofitting schemes and compares the proposed retrofitting schemes with other moment beam-to-column connections used for new construction. For the same resisting capacity of the retrofitted structure, the Vertical Plate Scheme will require much more material than the Flange Plate Scheme. But the Vertical Plate Scheme still has its advantages. The Vertical Plate Scheme does not require the removal of the floor slab and easier to conduct than the Flange Plate Scheme. Finally, it is demonstrated that the sizes of strengthening plates can greatly change the overall behaviour of the retrofitted structures; with the reduction of the strengthening plate sizes, the stress and strain will increase and the structure will experience elastic stage and elasto-plastic sequentially. This thesis minimises the thickness and the length of the strengthening plates by the exact analytic method for simple structures and the finite element method for complicated structures.

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ORCID for Antonios Zervos: orcid.org/0000-0002-2662-9320

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