## 4 Estimation of Enhanced Shear Strength  
The shear strength observed in the tests are compared with those predicted using design equations. ACI 549.4R-13 [39] provides that shear strength of masonry walls strengthened with Fabric Reinforced Cement Matrix (FRCM) is calculated by combining the contribution of the masonry and the FRCM composite material, respectively, as follows  
\[V_{n}=V_{m}+V_{f} \tag{2}\]  
where \(V_{n}\), \(V_{m}\) and \(V_{f}\) are the nominal shear strength, the contribution of the masonry, and the contribution of the FRCM composite material. The FRCM is a kind of mortar reinforced with grid type mesh, while SFRM is mortar reinforced with steel fibers. In spite of difference between the two types of reinforcement, the shear strength of masonry walls strengthened by SFRM is supposed to be calculated using Equation (2) considering that both FRCM and SFRM are essentially the same material for strengthening masonry walls. Figure 17: Damage state after the termination of diagonal tension tests. (**a**) CP. (**b**) CB0. (**c**) CB1.3. Figure 18: Damage state of masonry prisms with SFRM overlay removed. (**a**) RB1.3. (**b**) CB1.3. The masonry prisms failed in the diagonal tension failure mode as shown in Figures 17 and 18. For such a case, the shear strength of the masonry wall, \(V_{m}\), can be calculated using Equation (3) proposed by [PERSON] et al. (2005) [PERSON] et al. (2005) for the diagonal tension failure  
\[V_{m,dt}=\frac{tan\theta+\sqrt{21.16+tan^{2}\theta}}{10.58}\times f^{\prime}_{ t}\times A_{n} \tag{3}\]  
where \(\theta\) is the angle between horizontal and main diagonal of the wall, \(A_{n}\) is the net area of the cross section of the masonry wall (mm\({}^{2}\)), and \({f^{\prime}}_{t}\) is the tensile strength of the masonry calculated as \(0.67\times\sqrt{{f^{\prime}}_{m}}\) and \(0.5\times\sqrt{{f^{\prime}}_{m}}\), in which \({f^{\prime}}_{m}\) is the compressive strength of the masonry (MPa), for red clay bricks and concrete bricks, respectively (MPa), in accordance with [PERSON] et al. (2008) [PERSON] et al. (2008) [PERSON] et al. (2008). However, diagonal tension test result for masonry prisms without strengthening was used for \(V_{m}\) instead of calculation by Equation (3), considering the tensile strength of bricks has much uncertainty. From the peak load in the diagonal tension test, only the component parallel to the horizontal joints in the masonry prism was decomposed and assigned to \(V_{m}\). On the other hand, Equation (3) was used to calculate the contribution of the SFRM overlay to the shear strength, denoted by \(V_{f}\). In [PERSON] et al. (2015) [PERSON] et al. (2015) [PERSON] et al. (2015), masonry prisms were strengthened with mortar overlay reinforced by mesh, and the contribution of mortar overlay except mesh was calculated using Equation (3). This is a reasonable approximation when the mortar joints between bricks are relatively strong and the failure is governed by masonry units such as bricks. The tensile strength of SFRM in Figure 6 was used for \({f^{\prime}}_{t}\) in Equation (3). In addition, [PERSON] et al. (2017) [PERSON] et al. (2017) [PERSON] et al. (2017) conducted experiments on the diagonal tension strength and out-of-plane flexural strength for masonry walls strengthened with FRCM, and proposed Equation (4) to calculate the contribution to the shear strength by FRCM  
\[V_{ECC}=t_{ECC}\Big{(}zf^{\prime}_{yECC}+0.18\sqrt{f^{\prime}_{ECC}}L\Big{)} \tag{4}\]  
where \(V_{ECC}\) is the shear strength of the engineered cementitious composite (ECC) section (kN) and was used as shear strength of the SFRM in this study, \(t_{ECC}\) is the thickness of the overlay (mm), \(z\) is the lever arm assumed as 0.87 times the length of the specimen (mm), \(f^{\prime}_{yECC}\) and \(f^{\prime}_{ECC}\) are the tensile and compressive strengths of the overlay, respectively (MPa), and \(L\) is the length of the wall (mm).