Seismic Performance of Masonry Infill Walls Retrofitted With CFRP Sheets

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Title: Seismic Performance of Masonry Infill Walls Retrofitted With CFRP Sheets

Author(s): M. Saatcioglu, F. Serrato, and S. Foo

Publication: Special Publication

Volume: 230

Issue:

Appears on pages(s): 341-354

Keywords: concrete frames; ductility; earthquakes; fiber reinforcedpolymer (FRP); infill walls; masonry walls; retrofitting; seismic retrofit

Date: 10/1/2005

Abstract:
A significant portion of existing building stock that was constructed prior tothe enactment of modern seismic design provisions consists of gravity-load-designedreinforced concrete frames, infilled with unreinforced masonry walls. These structuresare susceptible to extensive seismic damage when subjected to strong earthquakesand require retrofitting in order to comply with the provisions of current building codes.Experimental investigation of gravity-load-designed reinforced concrete frames, infilledwith concrete block masonry, has been conducted to develop a seismic retrofit strategythat involves the use carbon fiber reinforced polymer (CFRP) sheets. Two half-scaleconcrete frames, infilled with masonry walls were tested with and without seismicretrofitting. The retrofit technique consisted of CFRP sheets, surface bonded on themasonry wall, while also anchored to the surrounding concrete frame by means ofspecially developed CFRP anchors. The frame-wall assemblies were tested underconstant gravity loads and incrementally increasing lateral deformation reversals. Theresults indicate that infilled frames without a seismic retrofit develop extensivecracking in the walls and frame elements. The elastic rigidity reduces considerablyresulting in softer structure. The failure may occur in non-ductile frame elements,especially in columns. Retrofitting with CFRP sheets controls cracking and increaseslateral bracing, improving the elastic capacity of overall structural system. Theretrofitted specimen tested in the current investigation showed approximately 300%increase in lateral force resistance, promoting elastic response to earthquake loads asa seismic retrofit strategy. Experimental observations and results are presented in thepaper.