Continuous Reinforced Concrete Beams Strengthened with Fabric-Reinforced Cementitious Matrix: Experimental Investigation and Numerical Simulation

This paper aims to examine the nonlinear flexural behavior of continuous RC beam specimens strengthened with fabric-reinforced cementitious matrix (FRCM) composites through experimental testing and numerical modeling. A total of nine two-span RC beam specimens were constructed and tested. Test parameters included the type of FRCM (carbon (C-FRCM) and polyparaphenylene benzobisoxazole (PBO-FRCM), location of strengthening (sagging and hogging regions) and number of FRCM layers (two and four layers). Test results indicated that sagging strengthening resulted in a strength gain in the range of 17 to 29%, whereas hogging strengthening increased the load capacity by 9 to 17%. The use of C-FRCM resulted in a higher strength gain than that provided by PBO-FRCM composites. Specimens strengthened with PBO-FRCM exhibited, however, higher ductility and deformational capacity than those of their counterparts strengthened with C-FRCM. Doubling the number of FRCM layers resulted in no or insignificant increase in the load capacity but reduced the beam ductility. Specimens strengthened in the sagging regions exhibited moment redistribution ratios of 13 to 26% between the hogging and sagging regions. Insignificant moment redistribution was recorded for the specimens strengthened in the hogging region. Three-dimensional (3D) numerical simulation models, with and without an interfacial bond-slip law at the fabric–matrix interface, were developed. The inclusion of the bond-slip law in the modeling had an insignificant effect on predicted response. Although the models tended to underestimate the deflection, the predicted load capacities were within a 12% error band. Numerical findings were in agreement with those obtained from laboratory testing.

Experimental Characterization of Masonry Panels Strengthened with NFRCM

In the last years, the interest in eco-sustainable composites has consistently increased. Such innovative materials are actually a promising sustainable solution for structural strengthening since they can be an alternative to petroleum‐based materials, which are frequently used for masonry retrofitting. This work describes an experimental campaign dedicated to investigating the behavior of Fabric-Reinforced Cementitious Matrix (FRCM) with natural fibers (NFRCM) made with eco-sustainable materials. Experimental tests are performed on unreinforced masonry panels (URM) and reinforced ones (RM), for characterizing their mechanical behavior. URM samples are compared with RM ones accounting for their response under shear actions.

Statistical analysis of the bonding properties of the fabric-reinforced cementitious matrix for strengthening masonry structures

The fabric-reinforced cementitious matrix (FRCM) has been extensively studied and applied for the strengthening of masonry structures. Special attention needs to be given to the bonding properties between the FRCM and masonry substrate for strengthening applications. This paper presents a statistical analysis of the bonding properties based on the available literature. First, the collected test results were discussed in terms of the interfacial failure mode. Second, the factors influencing the ultimate bond load were analysed based on the different failure modes, and a corresponding prediction formula was further determined via regression analysis for interfacial debonding and slippage failures. Then, the characteristic values of the ultimate bond load were determined via a probabilistic method. Finally, the fracture energy for the slippage failure at the fabric-matrix interface was analysed, and a corresponding prediction formula was obtained via regression analysis. Additionally, some of the collected test results present higher dispersion due to the large variability of the FRCM material properties and the differences in the testing procedures used by different institutions. More studies are needed to improve the reliability of the proposed procedure.

Experimental Research on Bond Behaviour of Fabric Reinforced Cementitious Matrix Composites for Retrofitting Masonry Walls

Fabric reinforced cementitious matrix (FRCM) composites, also known as textile reinforced mortars (TRM), an inorganic matrix constituting fibre fabrics and cement-based mortar, are becoming a widely used composite material in Europe for upgrading the seismic resistance of existing reinforced concrete (RC) frame buildings. One way of providing seismic resistance upgrading is through the application of the proposed FRCM system on existing masonry infill walls to increase their stiffness and integrity. To examine the effectiveness of this application, the bond characteristics achieved between (a) the matrix and the masonry substrate and (b) the fabric and the matrix need to be determined. A series of experiments including 23 material performance tests, 15 direct tensile tests of dry fabric and composites, and 30 shear bond tests between the matrix and brick masonry, were carried out to investigate the fabric-to-matrix and matrix-to-substrate bond behaviour. In addition, different arrangements of extruded polystyrene (XPS) plates were applied to the FRCM to test the shear bond capacity of this insulation system when used on a large-scale wall.