# Parametric Analyses of the Response of Masonry Walls with Reinforced Plaster
## 3 Numerical Simulations
### Retrofitted Masometry--Plaster Reiforcement  
The relative contribution of reinforced plaster to the overall load-bearing capacity of masonry can be significant, especially for thin masonry walls of poor quality. The reinforcement of the plaster plays a significant role in improving the tensile strength and the ductility of a specimen. The conventional approach considers the use of steel nets as reinforcements, but, in the recent past, several alternatives have been proposed, using innovative materials as polymers, carbon or glass fibers, and fiber meshes [43; 44]. A different concept of overlay strengthening systems involves fiber-reinforced concrete plaster [45; 46], which avoids the use of reinforcement nets and has the advantage of developing diffuse crack patterns with reduced crack width.  
A numerical comparison was performed to evaluate the effect of the steel net on the retrofitted wall, while also considering the use of steel fibers as alternatives to conventional steel reinforcement (Figure 23).  
The ductility of the fibers has a significant reinforcing effect after cracks are initiated in the matrix (i.e., concrete plaster) and their use significantly increases the fracture energy \(\mathrm{G_{f}}\) of the material. The fracture energy is a fundamental parameter that controls the behavior of a material after the limit strength is reached. For a certain value of plaster tensile strength, increasing the \(\mathrm{G_{f}}\) means improving the material's ductility, and greater ductility increases the resistance against crack growth. The value of \(\mathrm{G_{f}}\) used in the simulation for the fiber-reinforced concrete was 800 N/m (in the reference configuration, the plaster had \(\mathrm{Gf}=80\) N/m), which corresponded to a very low steel-fiber content (about 0.2%), although significantly higher values may also be reached by increasing the fiber volume (for instance, 20,000 N/m with 1% fiber content) [47; 48].  
Figure 22: Out-of-plane displacement along the diagonal for different numbers of anchors: (**a**) at peak load, (**b**) at failure.  
From Figure 23 it is evident that the use of the steel net increased the load carrying capacity and deformability of the wall with respect to the configuration without reinforcement. A similar effect in terms of capacity was obtained by using the fiber-reinforced concrete plaster, which showed less ductility in the post-peak response than the steel net.  
The damage pattern of the tension at the peak load and at failure are reported in Figures 24 and 25. The absence of reinforcement caused the formation of a main crack localized along the diagonal, whose width increased significantly after the peak load. The use of the steel net made possible the spread of damage over a wider area, by means of multiple small cracks. After the peak, the cracks increased in number and some damage close to the loading shoes was evident, together with the punching of the connectors. With the use of the fiber-reinforced concrete, at the peak load, the plaster cover showed limited damage, which was mainly localized close to the loaded corners. At collapse, this damage in the corners became even more evident, and the punching of the anchors was also detected. Unlike the two previous configurations, no diagonal cracks are observed.  
Figure 23: Load–displacement curves without reinforcement, with steel-net reinforcement and with fiber-reinforced plaster.  
Figure 24: Damage pattern at the peak load for different configurations of reinforcement: (a) no reinforcement; (b) steel net; (c) fiber-reinforced plaster.  
Overall, the use of steel nets is fundamental to avoid localized damage and makes it possible to significantly increase the capacity of retrofitted walls, as well as guarantying a certain resistance and ductility after the peak load. The use of steel-fiber concrete may be evaluated as a valid alternative to steel reinforcement to obtain analogous load-carrying capacity and more limited damage.