A comparative study of flexural behavior of reinforced masonry walls strengthened with near-surface mounted FRP bars or externally bonded FRP sheets

Abstract eng:
Strengthening is a common process of upgrading the capacity of structural elements to carry additional loads. Out-of-plane flexural behavior of reinforced masonry walls, strengthened with Near-Surface Mounted (NSM) Fiber Reinforced Polymer (FRP) bars or Externally Bonded (EB) FRP sheets and subjected to cyclic loading, was experimentally investigated. Twelve reinforced masonry walls were built for this study. Identical reinforced masonry walls in their unstrengthened form were used as control specimens. Five specimens strengthened using NSM and five specimens with EB were tested. These reinforced walls were strengthened using CFRP and GFRP bars which were placed near the surface (NSM). Also a single ply and a 2-ply wet laid up GFRP in addition to CFRP laminate were used as external reinforcement (EB). A constant reinforcement ratio (ρ) for mild steel was used. The walls were tested in four-point bending with an effective span of 1.12 m between the supports, and subjected to cyclic load with loading rate 1.27 mm/min. This investigation examines the effect of different parameters related to FRP type and amount, and bond pattern (stack and running). The impact of these parameters on the ductility and strength capacity of out-of-plane strengthened wall was evaluated. The force-displacement relationship of the walls and the associated strains in the reinforcement bars and FRP composite were monitored throughout the tests. Different modes of failure occurred in the strengthened reinforced walls, including a punching shear failure through the concrete block, as well as a rupture of FRP and debonding of FRP reinforcement from the masonry substrate.

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