Analytical Model for Predicting Response and Flexure-Shear Resistance of Composite Beams Combining Reinforced Ultrahigh Performance Fiber-Reinforced Concrete and Reinforced Concrete

Abstract

The addition of an external layer of reinforced ultrahigh performance fiber-reinforced concrete (R-UHPFRC) on top of reinforced concrete (RC) floor slabs and bridge decks is an emerging technique for strengthening RC structures. As an additional reinforcement, a layer of R-UHPFRC significantly increases the maximum resistance and deformation capacity of RC elements, thus creating a composite element that herein is referred to as RU-RC elements. This paper presents an elastic-plastic fictitious RU-RC composite hinge model for the damage caused by flexural and flexure-shear cracks in the RC element of the composite members. The model accounts for the nonlinear interaction of the two elements due to intermediate-crack-induced debonding (ICD) zone in the near-interface concrete. The model determines the force-deflection response and force in the RU-RC composite tension chord. Furthermore, the contribution of the R-UHPFRC element and the shear resistance envelope of the member are calculated. Comparison with available experimental results shows that the model can accurately predict the member response, resistance and failure mode. A simplified formulation for the shear resistance of the composite members is proposed. The models in this paper are needed for the design of the structural behavior of RC beams strengthened with R-UHPFRC.

Strengthening of reinforced concrete beams using ultra high performance fibre reinforced concrete (UHPFRC)

“…7 was adopted for a characteristic size equal to 2mm [31]. This model is in agreement with the model proposed by Habel et al [27] and adopted by Bruhwiler [26] and Noshiravani and Bruhwiler [28]. According to this model, the behaviour of UHPFRC is modelled with an elastic behaviour up to initiation of the microcracking followed by a second linear part in to the phase of strain hardening with multiple microcracking.…”

“…The findings presented in the previous studies are mostly focused on the mechanical properties of UHPFRC, and there are other published studies on strengthening applications [24][25][26][27][28][29][30][31]. Farhat et al [24] examined beams strengthened with UHPFRC strips.…”

“…Combination of UHPFRC with reinforcing steel bars for the rehabilitation of existing concrete elements was examined by Habel et al [27] and this technique was found to be quite promising, since the existing structures were efficiently strengthened and their resistance and their ultimate moment were considerably increased [27]. An analytical model for elements strengthened with combined UHPFRC and steel bars was proposed by Noshiravani and Brühwiler [28] together with a simplified formulation for the shear resistance of the composite members [28]. Magri et al [30] investigated the combination of UHPFRC with Textile Reinforced Mortar (TRM) and increment of maximum load capacity and ductility of the examined specimens was observed [30].…”

Shear strengthening of reinforced concrete beams using prefabricated ultra‐high performance fiber reinforced concrete plates: Experimental and numerical investigation

“…There are other published studies on strengthening RC structures using casting UHPFRC layers or jackets in situ . Habel et al investigated the flexural performance of composite concrete‐UHPFRC elements.…”

“…There are other published studies on strengthening RC structures using casting UHPFRC layers or jackets in situ. [18][19][20][21][22][23][24][25][26][27] Habel et al 18 investigated the flexural performance of composite concrete-UHPFRC elements. In this study, three configurations for the optimum performance of the composites elements were proposed.…”