Effect of Sizes and Positions of Web Openings on Strut-and-Tie Model of Deep Beams

Abstract

The trend towards high-rise concrete structures has placed an increased importance on the design of reinforced concrete deep beams. Deep beams also have useful applications in foundations and offshore gravity type structures. Numerous design models for deep beams have been suggested, however even the latest design manuals still offer little guidance for the design of deep beams in particular when complexities exist in the beams like web openings. A method commonly suggested for the design of deep beams with openings is the strut-and-tie model which in the present study is developed through topology optimisation of continuum structures. During the optimisation process, both the stress and displacement constraints are satisfied and the performance of progressive topologies is maximised. In all, eight concrete deep beams with web openings are optimised and compared in an attempt to examine the effect of sizes and positions of web openings on the strut-and-tie models. Through comparison with published experimental crack patterns, the study confirms the effectiveness of the optimisation technique in developing the strut-and-tie model representing the load transfer mechanism in concrete deep beams under ultimate load, which in turn would assist detailed design of such structural elements.