Shear-flexural strength mechanical model for the design and assessment of reinforced concrete beams

Abstract

A conceptual model for the prediction of the shear-flexural strength of slender reinforced concrete beams with and without transverse reinforcement is presented. The model incorporates the shear transferred by the un-cracked concrete chord, along the crack's length, by the stirrups, if they are, and, in that case by the longitudinal reinforcement. After the development of the first branch of the critical shear crack, failure is considered to occur when the stresses at any point of the concrete compression chord reach the assumed biaxial stress failure envelope. A physical explanation is provided for the evolution of the shear transfer mechanisms, and the contribution of each one at ultimate limit state is formulated accordingly. Simple equations are derived for shear strength verification and for designing transverse reinforcement. The method is validated by comparing its predictions with the results of 1131 shear tests, obtaining very good results in terms of mean value and coefficient of variation. Because of its accuracy, simplicity and theoretical consistency, the proposed method is considered to be very useful for the practical design and assessment of concrete structures subjected to combined shear and bending.

Keywords::

• reinforced concrete
• concrete beams
• design
• shear strength
• assessment
• shear failure

Acknowledgements

This work has been developed under the framework of the Research Projects ‘BIA2012-36848’ and ‘BIA2012-31432’, both funded by the Spanish Ministry of Economy and Competitiveness (MINECO) and co-funded by the European Regional Development Funds (ERDF). A part of this investigation was developed during the stay of Prof. A. Marí at the Faculty of Engineering of the University of Porto (FEUP), funded by the Spanish Ministry of Education, Culture and Sports through the National Human Resources Mobility Program of the R&D National Plan (project PRX12/00341).