Characterization of shear deformations in reinforced concrete members without shear reinforcement

The load-carrying capacity of many reinforced concrete structures is governed by shear failures, occurring before reaching the flexural capacity of the member. For redundant systems, such as slabs subjected to concentrated loads, local shear failures (typically initiated at locations with highest shear forces) can however occur after redistributions of internal forces due to the propagation of the shear cracks. Such process can depend upon the development of shear strains and the softening response of the member and can be stable or unstable. A suitable understanding and modelling of the complete shear response of reinforced concrete, including its deformations both for its pre-and post-peak branches, is thus instrumental for a consistent and comprehensive analysis of the shear response and strength of redundant elements.Such topic has received little attention in the past and analyses of redistributions of internal forces in concrete structures are often performed on the basis of refined flexural models, but coarse considerations for shear strains (typically elastic laws). This situation is a consequence of the lack of consistent experimental measurements on the shear deformations of reinforced members both before and after reaching the maximum shear capacity. Currently, however, the advent of refined measurements techniques such as Digital Image Correlation allows for an accurate tracking of the shear strains and for a fundamental understanding of its development. In this paper, taking advantage of such techniques, a comprehensive approach for determining the shear strains and their distribution across the depth of a section is presented. This approach allows reproducing accurately the development of shear strains and to predict the load-carrying capacity of redundant systems. The model is validated with selected test data and is considered as an effort to contribute to future numerical implementations of reinforced concrete shell models with realistic out-of-plane responses.