Experimental bond tests on masonry panels strengthened by FRP

A review on the bond behavior of FRP composites applied on masonry substrates

“…Nevertheless, when load-slip curves coming from bond tests on bricks and on masonry prisms are compared, a significant difference can be found between these two types of substrates. In fact, experimental curves obtained from masonry prisms presented several discontinuities or jumps during the debonding part of the tests, with a typical saw-tooth shaped curve, where load drops are associated with the periodic alternation of bricks and mortar joints on the substrate [10,27,[44][45][46]. This particular behavior was mainly observed analyzing load-slip curves and confirmed by local strain gauges readings during tests execution; several numerical models [39,44,[47][48][49] were then developed in order to validate experimental outcomes and to better understand this phenomenon, assuming different interface laws for bricks and mortar joints.…”

“…The typical behavior of FRP composites applied on masonry substrates, when analyzing force-slip curves, considering bond lengths longer than the effective one, is mainly described by an ascending almost linear branch until the onset of debonding process, followed by a nearly horizontal plateau [10,14,25,27] up to the complete detachment of the composite reinforcement. This behavior could be defined as similar to that observed on bond tests performed on concrete substrates.…”

“…Experimental works on FRP composite materials bonded to historic masonry are also discussed in [16,27]: results showed that GFRP reinforcement usually reveals a cohesive debonding failure with detachment of a thin layer of substrate, usually thicker in correspondence of the mortar joints. The failure mechanism of ancient masonry elements when strengthened by CFRPs is properly analyzed in [25], where the debonding mechanism was divided into two main typical failure modes: a first mode characterized by a thick and irregular layer of substrate detached with a wedge of masonry at the free end and a second failure mode with a thinner layer of detached materials, both related to the penetration depth of the glue into the substrate.…”

Minimal Mass Design of Strengthening Techniques for Planar and Curved Masonry Structures

“…We assume a tensile strength σ b equal to 376.13 MPa, which corresponds to an average value of the bond strengths of the FRP and FRCM reinforcements of masonry structures analyzed in [7,8], respectively (we employed formula (5.6) of [21] to estimate such a strength). Fig.…”

“…Nowadays, it is a common practice to reinforce such structures by applying tensile reinforcements made of traditional materials, such as steel, or innovative high-strength materials [4,5,6]. Strips and/or meshes of materials like Fiber Reinforced Polymers (FRP) or Fabric Reinforced Cementitious Matrix (FRCM) composites are often bonded to masonry structures to improve their mechanical properties [7,8,9]. However, it is worth remarking that such strengthening techniques, when improperly used, may lead to an excessive over-strength of the reinforced structure, and reduced 'cracking-adaptation' capacity [10].…”