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CIB Conferences

Abstract

Previous studies have shown that compressive arch action (CAA) is a key load-resisting mechanism in beam–column sub-assemblages subjected to column removal, while current design practice commonly relies on flexural capacity based on plastic theory. This paper presents a comparative study of CAA and flexural capacity for five two-dimensional precast and post-tensioned concrete beam–column sub-assemblages tested under a middle column removal scenario. Flexural capacity is determined based on plastic theory of fully fixed double-span beams. The results show that the ultimate flexural capacity of prestressed specimens is significantly lower than that of the non-prestressed specimen, despite all specimens being designed to have comparable flexural capacity under normal conditions. This reduction is mainly attributed to smaller positive yield moments caused by reduced bottom reinforcement when the beam designed with post-tensioned tendon. In contrast, all specimens exhibit substantial enhancement in ultimate resistance due to CAA, promoted by thick beam sections and the development of axial compression. Prestressed specimens demonstrate significantly greater CAA enhancement than the non-prestressed specimen, owing to the great axial compression forces induced by prestressing.

Keywords

Column removal scenario, precast and post-tensioned concrete structure, compressive arch action

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