# Hybrid Fibres as Shear Reinforcement in High-Performance Concrete Beams with and without Openings
## 2 Experimental Work
### Beams Dimensions, Details and Preparation Testing Procedure  
Six high-performance concrete beams with dimensions of 2500 \(\times\) 400 \(\times\) 200 mm were made. The beams had an effective span of 2300 mm and the span-to-depth ratio was 5.75. The tension steel reinforcement consisted of two \(\phi\)22 mm deformed steel bars, equivalent to the reinforcement ratio of 0.01, whereas the compression steel reinforcement for the B1 and BO1 \(\div\) BO3 beams consisted of two \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Material** & **Symbol, Unit** & **B1** & **B2** & **B3** & **BO1** & **BO2** & **BO3** \\ \hline Cement CEM 1 52.5R & C, (kg/m\({}^{3}\)) & 596 & 596 & 596 & 596 & 596 & 596 \\ Silica fume & M, (kg/m\({}^{3}\)) & 59.6 & 59.6 & 59.6 & 59.6 & 59.6 & 59.6 \\ Granoidiorite 2/8 mm & A, (kg/m\({}^{3}\)) & 990 & 990 & 990 & 990 & 990 & 990 \\ Quartz sand 0.05/2 mm & S, (kg/m\({}^{3}\)) & 500 & 500 & 500 & 500 & 500 & 500 \\ Superplasticiser & SP, (l/m\({}^{3}\)) & 20 & 20 & 20 & 20 & 20 & 20 \\ Water & W, (l/m\({}^{3}\)) & 196 & 196 & 196 & 164 & 164 & 164 \\ \hline Steel fibre & ST, (kg/m\({}^{3}\)) & – & 39 & 78 & – & 78 & 117 \\  & V\({}_{\rm ST}\), (\%) & – & 0.5 & 1 & – & 1 & 1.5 \\ \hline Polypropylene fibre & PP, (kg/m\({}^{3}\)) & – & 0.25 & 0.5 & – & 0.5 & 1 \\ VPP, (\%) & – & 0.025 & 0.05 & – & 0.05 & 0.1 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Mixture proportions. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Beam** & **Slump** & **Compressive** & **Splitting Tensile** & **Flexural Tensile** & **Modulus of** \\
**Notation** & **(mm)** & **Strength (MPa)** & **Strength (MPa)** & **Strength (MPa)** & **Elasticity (GPa)** \\ \hline B1 & 120 & 113.8 & 5.0 & 8.2 & 38.74 \\ B2 & 111 & 106.6 & 9.9 & 8.9 & 32.40 \\ B3 & 102 & 111.0 & 11.0 & 9.4 & 39.42 \\ BO1 & 116 & 117.0 & 6.5 & 7.8 & 38.99 \\ BO2 & 95 & 110.6 & 10.5 & 9.1 & 37.25 \\ BO3 & 88 & 106.4 & 10.7 & 9.6 & 39.22 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Properties of concrete. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Reinforcement** & **Nominal** & **Modulus of** & **Yield** & **Ultimate** & **Ultimate** \\
**Diameter** & **Elasticity** & **Strength** & **Strength** & **Tensile** \\
**(mm)** & **(GPa)** & **(MPa)** & **(MPa)** & **Strength (\(\sim\))** \\ \hline Tension bar & 22 deformed & 203 & 475 & 644 & 0.105 \\ Compression/diagonal bar & 12 deformed & 199 & 456 & 642 & 0.097 \\ Stirrup & 6 plain & 193 & 302 & 454 & 0.085 \\ Steel fibre & 1 hook-ended & 200 & – & 1100 & – \\ Polypropylene fibre & 0.03 straight & 3.5 & – & 350 & – \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Reinforcement properties. \(\phi\)12 mm deformed steel bars with 90\({}^{\circ}\) hooks. All the beams were tested under a shear span-to-effective depth ratio of 2.0 with a cover equal to 20 mm. The details of the stirrup spacing for the B1 and BO1 beams are shown in Figure 1. Beam B1 was designed to fail in shear mode. The loads corresponding to the yielding of main steel bars and shear failure were calculated according to EC-2 [50] to be 336.5 kN and 232.0 kN, respectively. Beams BO1 \(\div\) BO3 had two square openings, one in each shear span, with dimensions of 140 \(\times\) 140 mm. The ratio of the opening size to beam effective depth was 0.38. It was large so as to cause a sizable reduction in the shear capacity. The opening centre was located 617 mm from the support position. Moreover, the opening was designed outside the line of the critical diagonal crack and the opening edge was placed exactly on the boundary of the shear and flexural zones. This made it possible to evaluate the hybrid fibre efficiency as shear reinforcement. [PERSON] et al. [60] indicated that the use of diagonal reinforcement is an effective method in crack control of RC beams with openings. In this study, they were strengthened with internal steel bars consisting of two \(\phi\)12 mm diagonal bars around the opening.