Articles

Shear Resistance Mechanism and Shear Resistance Prediction of UHPC Strengthened T-beams

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Abstract

This is an accepted article with a DOI pre-assigned that is not yet published.

Ultra-high performance concrete (UHPC) is being increasingly used as repair materials for deficient reinforced concrete structural elements. Given its remarkable tensile properties, UHPC can provide durable repairs exempt of macrocrack in serviceability limit state as well as significant gain in resistance at ultimate limit state. However, its strengthening effect on structures is generally neglected due to the lack of applicable analytical models that can accurately predict the ultimate resistance of strengthened elements. In that context, an experimental research project was carried out at Polytechnique Montreal to investigate the shear behavior of reinforced concrete T-beams strengthened with lateral or U-shape UHPC layers. The data collected with digital image correlation (DIC) and internal instrumentation allowed to quantify the strengthening effect of the UHPC layers and to characterize the shear resistance mechanism of strengthened T-beams. The presentation will first describe shear tests conducted on UHPC strengthened T-beams. The load- displacement curves and DIC analysis will highlight the structural behavior observed according to the UHPC thickness layer and presence of anchors. The presentation will then introduce a new analytical model, based on forces equilibrium and the modified compression field theory (MCFT), that predict the shear resistance of T-beams. Lastly, the presentation will show the model validation using DIC strain measurement in the shear span and the ultimate shear capacity of strengthened T-beams. The model provides an accurate estimation of the ultimate shear strength and is capable to distinguish contributions of reinforced concrete, stirrups and UHPC in the shear resistance mechanism.

Keywords: T-beams, UHPC lateral layer, UHPC U-shape layer, UHPC thickness, anchors, shear mechanism, analytical model, model validation

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