Recent Advances in the Straps/Strips Technique for Out-of-plane Strengthening of Load-bearing Masonry Walls

Abstract

As is well known, the main contribution of the FRP strips to the strength of load-bearing walls is an improvement in the in-plane strength. This paper deals with the possibility of applying the FRP strips in way to modify the strengthening mechanism of the FRP reinforcing system, from an in-plane to an out-of-plane strengthening mechanism. In order to achieve this goal, a second reinforcement system – derived from the CAM system (Active Confinement of Masonry) – provides connections between the FRP strips placed on the opposite sides of the wall. This new strengthening technique – called the straps/strips technique – establishes a stiffness constraint that forces the opposing FRP strips to behave like two flanges of an FRP I-beam embedded in the wall. Consequently, the use of FRP strips also improves the flexural strength of the wall. The present paper briefly summarizes the results obtained in previous works with the straps/strips technique and proposes an improvement of this strengthening technique, based on some weak-points emerged in the early experimentations. The paper also shows the results of a further experimental test, performed with the improved straps/strips technique. Finally, the similarity between FRP strips with transversal connection and concrete wythes of a sandwich panel with flexible connectors leads to interpret the behavior of the ideal I-beam in terms of composite action established between the FRP strips. This paves the way for analytical modeling of the straps/strips technique.

Strengthening of Un-Reinforced Brick Masonry Walls Using Epoxy Mortar

“…In some cases, alteration/modifications in existing masonry structures due to change in purpose and usage of building also demand strengthening of masonry walls subjected to increased gravity loads. Strengthening / retrofitting of existing masonry structures may be done by many well-known techniques such as using Fiber-Reinforced Polymer (FRP) composite (ElGawady et al, 2006;Marcari et al, 2007 ;Wei et al, 2007;Mahmood and Ingham, 2011;Bui and Limam, 2014;Mazzotti et al, 2015;Ramaglia et al, 2020), steel strips and bars (Farooq et al, 2014;Triwiyono et al, 2015;Ferretti et al, 2020;El-Salakawy et al, 2020;Yao et al, 2021), shotcrete (Lin et al, 2015;Ghezelbash et al, 2020) and fiber reinforced cement plastering (Luccioni and Rougier, 2011;Arisoy et al, 2015;Deng et al, 2019;Codispoti et al,2015). Although these common methods of strengthening masonry have many successful application cases, most of these techniques have some disadvantages such as time consumption in application, reduction in available space, disturbance of occupancy, adverse effects on aesthetics.…”