Innovative detailing for shear in concrete using high performance materials

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Existing shear design models for reinforced concrete use a stress-based compositional approach to member strength, from both a concrete contribution and from a shear reinforcement contribution based on a truss analogy.  These models limit the maximum strength of the shear reinforcement permitted in design, in order to limit crack widths at failure.  Maximum spacing of the shear reinforcement is defined by empirical rules based on an assumed angle for the internal truss.  Limited studies since the 1960's have shown that safe designs are possible when either of these criteria are relaxed.  Improved capacity models for shear that directly consider both the shear reinforcement strains and spacing, will permit economical and safe use of modern, durable reinforcement materials as stirrups.     This study will investigate influences on shear capacity from the longitudinal spacing of shear reinforcement, through laboratory and numerical studies.  Shear reinforcement arrangements representative of new construction will be considered, along with shear dowel configurations suitable for rehabilitation applications.  The influence of higher stirrup strains at failure, resulting from the use of high strength steel or fibre reinforced polymer materials, will also be considered.  A special emphasis in experimental investigations will be placed on configurations where little existing test data is available, including large members with wide reinforcement spacing.     Non-linear numerical models, the new test data, and a critical examination of existing design methods will permit development of a new strain-based shear design approach which can account for stirrup spacing, in combination with the stirrup mechanical properties.  This model will permit more innovative detailing to occur in practice, for members with sparsely spaced high performance reinforcing materials.  Furthermore, the ability to predict the capacity of existing members will be improved, thereby minimizing unnecessary and costly rehabilitation.