Byfield, M.P. and Paramasivam, S.
The prevention of disproportionate collapse using catenary action
At COST Action C26: Urban Habitat Constructions under Catastrophic Events.
30 - 31 Mar 2007.
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Disproportionate collapse occurs when the removal of load bearing members (one or more columns, or load bearing walls) causes localized structural damage which leads to further loss of load bearing members and, ultimately, to the collapse of whole or part of the structure. The accidental load, carried by the removed column can be transferred to nearby columns either by beam action or by catenary action. Simple connections such as fin plate, double angle web cleat and flexible end plate connections are routinely assumed to be com-pliant with the tying force design method, which aims to ensure that column loads are redistributed via cate-nary action in the event of damage. This is feasible only if the joints have sufficient ductility as well as tensile strength. Semi-rigid and rigid connections redistribute the column loads through beam action, provided that the connections have sufficient rotation capacity. This investigation demonstrates that the beam-column joints (simple and semi-rigid connections) in many designs have insufficient ductility to successfully bridge dam-aged columns. In simple (nominally pinned) connections, a couple can develop between beam flange and col-umn due to insufficient joint ductility. The resulting prying action is shown to cause early joint fracture and subsequently to lead to progressive failure. In semi-rigid connections, the beam remains elastic and the con-nections plastify, leading to early joint failure.
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