An adequate theory for the shear strength of reinforced concrete structures

Abstract

Traditional shear design procedures for concrete structures rely on empirical equations derived from laboratory experiments and lack the type of adequate theory that forms the basis of flexural design. As shear resistance depends on so many variables and because laboratory tests do not cover the full practical range of parameters, empirical shear design equations can result in structures with inadequate shear strength. Recent failures of such structures have highlighted the need for shear design provisions solidly based on an adequate theory. This paper introduces such a theory and explains the simple design models derived from the theory, which include a strut-and-tie model for disturbed regions and a sectional model for flexural regions. These models form the basis of the shear provisions on the 2004 Canadian standard for the design of concrete structures. In the current paper, results from nine major experimental series are compared with predictions from the new shear provisions and with predictions from the shear provisions of the Eurocode and the American Concrete Institute code. It is demonstrated that the new shear design provisions are capable of predicting the shear strength of reinforced concrete members and prestressed concrete members with considerably greater reliability.

Shear-flexural strength mechanical model for the design and assessment of reinforced concrete beams subjected to point or distributed loads

“…In any case, the inclination of the cracks is affected by the longitudinal and transverse reinforcement ratios ρ and ρ w , respectively, which influence the strains state. However, as observed by other researchers [18], in general this influence is moderate, being the effect of longitudinal reinforcement ratio more important [19]. Therefore, although the angle of the compression struts change, the horizontal projection of the critical shear crack does not change as much, since the increment of longitudinal reinforcement ratio increases and neutral axis depth, x.…”

Shear enhancement in RC beams with multiple point loads

“…The design strength at the bottom end of strut III is taken as f csb = 0.6f cd when using EC2 and is calculated as follows when using the MCFT approach of Collins et al [1,19,20]. (26) where  is a capacity reduction factor which is taken as 1.0 in the strength assessments of this paper.…”

“…The failure mechanism, and hence shear resistance of reinforced concrete beams depends in a complex fashion upon the shear span to effective depth ratio (a/d), loading arrangement and flexural reinforcement strain [1]. However, EC2 [2] and its UK precursor BS8110 [3] make the simplifying assumption that shear resistance is independent of a v /d (where a v is the clear shear span (see Fig.…”

A novel approach for evaluating the concrete shear strength in reinforced concrete beams

“…A new trend in evaluating the concrete shear strength is to relate shear strength to the strain in the longitudinal reinforcement [Vecchio and Collins, 1986;Bentz, et al, 2006;Collins et al, 2007; CSA Committee A23.3, 2004;AASHTO, 2008;Muttoni and Ruiz, 2008]. In these studies, the shear resistance, !…”