Abstract

Fabric Reinforced Cementitious Matrix (FRCM) and Composite Reinforced Mortar (CRM) systems are used as Externally Bonded Reinforcements (EBR) in civil and historical construction. These materials are made by fibrous reinforcement, in forms of dry (FRCM) or cured (CRM) meshes embedded in a cementitious/hydraulic lime matrix. At present, this technology is considered very promising in the field of structural strengthening, retrofitting and repair existing structures. This is true especially in those cases of masonry and historical buildings, due to the specific criteria of conservation and compatibility with the substrate that need to be fulfilled. These materials, in fact, results more compatible with masonry substrate because of the inorganic matrix, instead of polymeric resin used for the well-known FRP systems (Fiber Reinforced Polymers). The recent use of these new materials in civil engineering needs appropriate and complete guidelines, that regard not only the design aspects but also the durability features. This paper presents the results of a large experimental program focused on the durability of FRCM and CRM systems and their single components, in different alkaline environments. For the whole experimental campaign, the samples have been immersed into three different alkaline solutions, for four exposure times (500, 1000, 2000 and 3000 hrs). In addition, in order to study the different accelerating effects due to temperature, three different temperatures were maintained during the ageing periods: 23°C, 40°C and 70°C. The results about the mechanical characterization of residual properties are discussed in order to highlight the influence of alkaline environments on the mechanical properties of single elements and the whole strengthening systems that were tested herein.

Abstract

Reinforced concrete (RC) structures deteriorate over time and therefore, need to be strengthened. Despite the fact that RC structurtes have a decent fire rating, the performance of the strengthening system under fire exposure needs to be evaluated. One of the main restrictions associated with Fibre Reinforced Polymer (FRP) systems is their poor resistance to high temperatures, which originates from the combustible polymer matrix. Therefore, Fibre Reinforced Cementitious Matrix (FRCM) systems have been introduced due to their improved performance during fire exposure. The potential of Poly-paraphenylene-ben-zobisoxazole (PBO) FRCM to strengthen circular RC columns is evaluated using a nonlinear finite element analysis (FEA). The commericial software ABAQUS is used to develop 3D FE models to investigate the axial performance of the strengthening system. The modeling approach is performed by first conducting a thermal analysis to generate the nodal tempertaures. The second step of the model includes a displacement-controlled loading condition with imported nodal temperatures from the first model. The temperature dependent material properties are incorporated in both models. The modeling approach is validated against published literature and a parametric study is conducted on PBO FRCM strengthened and unstrengthened columns heated at durations of 1, 2, and 4 hours following the ASTM standard fire temperature-time curve. Results indicated a decrease in the axial capacity and stiffness of the strengthened and unstrengthened columns upon heating. Moreover, an increase in the columns' ductility due to the increase in temperature was observed. A decrease in ultimate strength of up to 78 and 68% was observed for the unstrengthened and strengthened columns respectively.

Abstract

This paper aims at investigating the in-plane shear response of FRCM-strengthened masonry walls. To this end, available results of experimental tests are collected, accounting for the masonry substrate made with bricks and mortar joints and several FRCM materials applied with different strengthening configurations. The contribution of the composite material to the masonry wall shear capacity is evaluated. The influence of some geometrical and mechanical parameters on the shear strength of the retrofitted walls is assessed. Available analytical design formulations are implemented to the database and commented.

Abstract

In most historic masonry structures, curved geometries, such as arches or vaults, are key structural components to the overall building stability. Therefore, it is crucial to assess their safety level with respect to changes in the boundary conditions (increased loads or settlements). If the safety level of the structure needs to be enhanced, a strategy to intervene and retrofit structural members is represented by the use of Fabric Reinforced Cementitious Matrix (FRCM) systems. These types of externally bonded composite materials, made of high-strength textiles embedded in inorganic matrices, are proven to be a particularly advantageous strengthening solution for curved masonry structures. Even though limit analysis approaches such as Thrust Network Analysis (TNA) have been widely used to assess structural stability, their use in a retrofitting framework is seldom explored. This paper proposes an automated procedure to design the FRCM reinforcement required in masonry structures based on an initial TNA assessment analysis. To perform these analyses, a nonlinear programming problem is implemented and solved to compute the minimum reinforcement required for stability. These quantities are then used to design the FRCM reinforcement according to existing regulations. Finally, the load-bearing capacity of the reinforced structure can be re-evaluated for different load cases ensuring that the structure is safe. The effectiveness of the proposed approach is benchmarked against laboratory tests and demonstrated on arched structures.

Abstract

Abstract

Abstract

Abstract

Abstract

Abstract