Strengthening strategies have become extremely efficient as demonstrated in recent scientific works and real field applications. The recent calamitous events focused the interest on existing masonry structures. In the common practice the strengthening strategies are performed improving the load capacity of existing structural elements. However, especially for slender masonry elements like as arches and barrel vaults, the increase of load capacity may not be the only and optimal approach. The ductility capacity represents an important aspect that should be taken into account in a strengthening strategy. A great number of applications is performed without relying on and assessing the ductility of the strengthened elements. This approach could promote deleterious effects on the structural behavior due to the brittle behavior provided by excessive amount of strengthening. Furthermore, a strengthening strategy must respect the compatibility with the masonry substrate especially for heritage applications.

The present paper focuses on the out-of-plane behavior of slender masonry elements strengthened with FRP or FRCM systems. A parametrical analysis was performed and results, in terms of bending moment–curvature diagrams and ultimate curvatures were analyzed in dimensionless form. The behavior of strengthened masonry is independent on the type of stress–strain constitutive relationship of composite, depending on mechanical fiber reinforcement ratio, ω. It is very important for practical applications when an overestimation of the effective amount of reinforcement is designed. In this sense the type of composite can be optimized, especially for poor masonry, where higher ω could promote brittle behaviors. At low ω, the type of the stress–strain constitutive relationship becomes a key aspect (e.g. linear or bi-linear strongly correlated to the type of composite: FRP or FRCM). Furthermore, the impact of the axial load both on the ductility capacity and on the load capacity becomes negligible at high values of ω. The results, provided in a dimensionless form, constitute the basis for a valid support to the design of interventions using composites on masonry structures.

This work represents a preliminary study to highlight some issues often overlooked in the strengthening of masonry structures, based on direct application of available design guidelines. It is the basis for future development of normalized approaches to perform targeted experimental validations and optimize the design of strengthening systems.

正如最近的科学研究和实际应用所证明的那样，加强策略已变得极为有效。最近发生的灾难性事件使人们对现有的砖石结构产生了兴趣。在通常的实践中，执行加固策略来提高现有结构元件的承载能力。但是，特别是对于细长的砖石结构（例如拱门和桶形拱顶），增加承载能力可能并不是唯一且最佳的方法。延展能力是加强战略中应考虑的重要方面。在不依赖和评估增强元件的延展性的情况下执行大量应用。由于过量的强化作用使材料变脆，因此这种方法可能对结构行为产生有害影响。此外，加强策略必须考虑与砌体基材的兼容性，特别是对于遗产应用。

本文着重于用FRP或FRCM系统加固的细长砖石构件的平面外行为。进行了参数分析，并以无量纲形式分析了弯矩-曲率图和极限曲率的结果。砌体的性能取决于复合材料的应力-应变本构关系的类型，具体取决于机械纤维的增强比ω。设计出高估有效加固量的方法对于实际应用非常重要。从这个意义上说，可以优化复合材料的类型，尤其是对于砌体较差的情况，在这种情况下，较高的ω可能会促进脆性。在低ω时，应力-应变本构关系的类型成为关键方面（例如 线性或双线性与复合材料的类型紧密相关：FRP或FRCM）。此外，在高的ω值下，轴向载荷对延展能力和载荷能力的影响都可以忽略不计。结果以无量纲形式提供，为使用砌体结构上的复合材料为干预设计提供了有效支持。

这项工作是一项初步研究，着眼于在直接应用现有设计准则的基础上，强调在加强砌体结构中经常被忽略的一些问题。它是将来开发标准化方法以执行目标实验验证和优化强化系统设计的基础。