Behavior of Infill Masonry Walls Strengthened with FRP Materials

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Title: Behavior of Infill Masonry Walls Strengthened with FRP Materials
Author: Lunn, Dillon Stewart
Advisors: Dr. Sami Rizkalla, Committee Chair
Dr. Abhinav Gupta, Committee Member
Dr. Rudolf Seracino, Committee Member
Abstract: Collapse of unreinforced masonry (URM) structures, including infill walls, is a leading cause of property damage and loss of life during extreme loading events. Many existing structures are in need of retrofit to bring them in compliance with modern design code provisions. Conventional strengthening techniques are often time-consuming, costly, and add significant weight to the structure. These limitations have driven the development of alternatives such as externally bonded (EB) glass fiber reinforced polymer (GFRP) strengthening systems, which are not only lightweight, but can be rapidly applied and do not require prolonged evacuation of the structure. The objective of this research program was to evaluate the effectiveness of strengthening infill masonry walls with externally bonded GFRP sheets to increase their out-of-plane resistance to loading. The experimental program comprises fourteen full-scale specimens, including four un-strengthened (control) specimens and ten strengthened specimens. All specimens consisted of a reinforced concrete (RC) frame (which simulates the supporting RC elements of a building superstructure) that was in-filled with solid concrete brick masonry. The specimens were loaded by out-of-plane uniformly distributed pressure in cycles up to failure. Parameters investigated include the aspect ratio, the strengthening ratio, the number of wythes, and the type of FRP anchorage used. The type of FRP anchorage was found to greatly influence the failure mode. Un-strengthened specimens failed in flexure. However, strengthened specimens without overlap of the FRP onto the RC frame failed due to sliding shear along the bed joints which allowed the walls to push out from the RC frames in a rigid body fashion. In the case where GFRP sheets were overlapped onto the RC frames, the aforementioned sliding shear caused delamination of the GFRP sheets from the RC frames. Use of steel angles anchored along the perimeter of the walls as shear restraints allowed these walls to achieve three times the service load without any visible signs of distress. GFRP strengthening of infill masonry walls was found to be effective, provided that proper anchorage of the FRP laminate was assured.
Date: 2009-05-05
Degree: MS
Discipline: Civil Engineering

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