Predicting the shear–flexural strength of slender reinforced concrete T and I shaped beams

• Shear-flexural strength mechanical model extended T- and I- beams.
• Compression chord, cracked web, longitudinal and transversal reinforcement contributions.
• The model considers the compression flanges contribution which may be relevant.
• Failure by propagation of the shear crack across the compression chord or by web crushing.
• Proposed equations valid for design and assessment without the need of iterating.

A mechanical model previously developed by the authors for the prediction of the shear–flexural strength of slender reinforced concrete beams with rectangular cross-section with or without stirrups has been extended to beams with T and I cross-sections. The effects of the section shape on each shear transfer action have been identified and incorporated into the corresponding equations. General expressions for strength verification and transverse reinforcement design have been derived. The contribution of the flanges to the shear strength is accounted for by means of an effective shear width, which depends on the section geometry and on the longitudinal reinforcement ratio. The effect of the vertical confinement stresses introduced by the shear reinforcement on the concrete web is also considered. The expressions derived are valid, as particular cases, for beams with inverted T or rectangular cross sections. The proposed equations have been checked with experimental results available in the literature, obtaining very good results. The simplicity, straightforwardness of application and the accuracy of the method make it suitable for daily engineering practice.