# Experimental Study on Shear Strengthening of RC Beams with an FRP Grid-PCM Reinforcement Layer
## 2 Experimental Study on Reinforcement Range  
### Test Programme  
There are three types of specimens with different CFRP grid-PCM reinforcement ranges in Series A, including the control beam N0 with no reinforcement, and the specimen RWC5 that is reinforced by a CFRP grid of CR5 type on the web only, while the remaining RHWC5 is similar to RWC5 but the reinforcement range covers both the web and the haunch, as indicated in Table 1.  
Figure 3 shows the manufacturing process for the specimens. Initially, concrete beams with an I-shaped profile were produced and then cured for 28 days. Subsequently, original beams were polished by vacuum blasting for surface treatment before the CFRP grid was attached to the lateral surface of the concrete beam, with rivets used as temporary anchorage. Finally, in order to avoid the occurrence of dehydration phenomenon, primer mortar was sprayed or painted prior to PCM shotcrete. Grade HRB 335 steel bars with a diameter of 10 mm and spaced at an interval of 250 mm were used as stirrups, where the calculated stirrup reinforcement ratio was 0.38%. The compressive and tensile steel bars of Grade HRB 335 with a diameter of 32 mm were placed in the upper and bottom \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Type**} & \multicolumn{2}{c}{**Existing Sample**} & \multicolumn{2}{c}{**Reinforcement Portion**} & \multirow{2}{*}{**Reinforcement Range**} & \multirow{2}{*}{**Thickness of**} \\  & **Stirrups, mm** & & & & \\  & & **Sars, mm** & & & \\ \hline N0 & & & & & \\ RWC5 & HRB335 & HRB335 & - & - & - \\ RHWC5 & D10@250 & D32 x 4 & CRS (150 x 50) & Web & 15 \\  & & & Haunch + Web & 15 \\ \hline \hline \end{tabular} Note: (1) RWC5 means reinforcement in web with a CFRP grid of type CR5, and RHWC5 means reinforcement in haunch and web with a CFRP grid of type CR5; (2) the FRP grid is embedded in PCM with a thickness of 15 mm at each side. (3) HRB-X means the strength class of steel bars; D-X means the steel bar with a diameter of X mm; @-X means the interval of stirrups is X mm.  
\end{table} 
Table 1: Details of the beam specimens of Series A.  
Figure 3: The manufacture process of specimens: (**a**) Concrete cast; (**b**) Original concrete beam; (**c**) Vacuum blast; (**d**) CFRP grid installation; (**e**) Primer mortar spray; (**f**) PCM shotcrete. region to resist the compressive and tensile force, respectively. The tensile steel reinforcement ratio calculated in this series (i.e., Series A) was 4.48%, the purpose of which is to ensure a higher flexural capacity than shear capacity, resulting in the typical shear failure prior to flexural failure in the end. Further, the shear span ratio of 2.75 in all specimens, which meets the demand of GB 50010-2010 [58], guarantees the occurrence of shear-compression failure which is regarded as one of typical shear failure modes. The design methods of reinforcement ratios with respect to steel bars and FRP grids mentioned before are introduced by GB 50010 [58], and they are determined by the following equations. \[\rho_{\text{web}}=\frac{A_{\text{web}}}{b_{\text{web}}\cdot s} \tag{1}\]  
\[\rho_{\text{w}}=\frac{A_{\text{w}}}{b_{\text{web}}\cdot h_{0}} \tag{2}\]  
where, \(\rho_{\text{web}}\), \(\rho_{\text{w}}\) are defined as the shear and tensile reinforcement ratio (i.e., the corresponding steel bars and FRP grids in this paper), respectively; \(s\) is defined as the spacing of the shear reinforcement; \(b_{\text{web}}\) and \(h_{0}\) are defined as the cross-sectional width and effective depth of the specimens, respectively; and \(A_{\text{w}}\) and \(A_{\text{web}}\) are defined as the total cross-sectional area of the tensile reinforcement and shear reinforcement at a spacing of s, respectively. A ready-mix normal concrete for casting and a kind of cementitious inorganic material called PCM for shotcrete were provided by local companies.