Performance of Masonry Wall Retrofitted Using Cfrp Sheets and Anchors

Abstract eng:
Different strategies can be used to repair, rehabilitate and strengthen existing structures. Techniques based on Carbon Fiber Reinforced Polymer (CFRP) materials appear to be innovative alternatives to traditional solutions because of their high tensile strength, light weight, and ease of installation. Due to bending and/or shear effects, CFRP sheets may lose adherence with the concrete surface, however the use of CFRP anchors allows reaching their full tensile capacity. Sliding between courses occurs often when the masonry wall interface has no internal reinforcement. A masonry wall with hollow concrete blocks with internal reinforcement was tested under constant axial load and cyclic lateral loads and rotation was restrained at top and bottom to produce double curvature deformation. The masonry wall length and height were 72in and thickness 7.6in. Diagonal shear cracks, toe crushing of the bottom of both corners of the masonry wall, and sliding at the base were presented. The rehabilitation of the masonry wall was divided into two phases. The first phase consisted of adding a reinforced concrete ring above the base foundation to encase the two badly-damaged bottom courses of CMU, reducing the aspect ratio L/H from 1 to 0.78. The partial retrofitted wall was tested to assess its condition. The second phase consisted of CFRP sheets attached on the wall surface with the strip aligned a diagonal direction to produce a tension brace or tie, being the CFRP sheets attached to the wall surface by epoxy and CFRP anchor which were installed at the ends of the sheets. Each diagonal tie had different amount of CFRP material in order to evaluate two different repair patterns. It was found that the rehabilitated masonry wall was less stiff than the existing elements even though the aspect ratio was reduced because the concrete ring applied at first phase of rehabilitation. However the retrofitted masonry wall had higher shear capacities, increasing more 60% compared with the as-built wall; and the values of drift at peak load were comparable. It was noticed as well considerable sliding displacement occurred at the top of the strengthened wall. Sliding at top was about 50% of the total lateral displacement, shorter that 70% from the as-built wall. Sliding at bottom of the wall was not significant. Performance of the masonry wall and the applied CFRP materials during the laboratory tests are explained.

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