Science & Technology, Physical Sciences, Optics
It can readily be seen that when subject to a uniformly distributed load, a prismatic steel reinforced concrete beam with constant longitudinal and transverse reinforcement percentages is inherently inefficient. By following simple optimisation routines it is possible to design beams whose flexural and shear capacities reflect the requirements of their loading envelope, with such elements tending to be non-prismatic. Research at the University of Bath has developed simple methods for the creation of such elements to offer material and embodied carbon savings of up to 40%. However, the shear behaviour of such variable section steel reinforced concrete beams has previously been an area of confusion for designers, who must often rely on empirical relationships derived from prismatic beam tests. This paper presents the results of new tests undertaken at the University of Bath on tapered concrete beams designed using both BS EN 1992-1-1 (2004) and the compressive path method, in which digital image correlation was used to analyse the specimens. Using the 'MatchID' program, strain distributions in each of the specimens during loading were plotted, with the results allowing important comparisons to be drawn between the various design methods. The DIC technique was subsequently used to verify new proposals for the shear design of non-prismatic concrete beams, which aim to provide improved guidance for designers of optimised concrete structures.