FRP Strengthened Brick-Infilled RC Frames: An Approach for their Proper Consideration in Design

A considerable number of existing buildings in seismic prone countries has been constructed either based on earlier concepts for seismic design or without applying seismic provisions. As a consequence, their seismic upgrade is a matter of concern. In urban environments, these structures usually consist of reinforced concrete (RC) frames with brick infill walls. Their strengthening with traditional methodologies, such as concrete jackets and shear wall construction, often results in operation interruption and high cost. The present research examines the complex response of RC frames and brick infill walls strengthened with Fibre Reinforced Polymers (FRP), a recently proposed retrofit scheme that becomes attractive because of its low cost and ease of implementation. Instead of the commonly used pair of compression struts that models the infill wall, a multiple strut masonry panel element model with advanced constitutive laws is applied for the representation of the nonlinear response of the infill wall, while a tension tie is used to consider the FRP sheets contri- bution on the response. The parameters of the wall and the FRP elements that are used in the numerical model are cali- brated against experimental results available in the literature for two-storey, one-bay reinforced concrete frames subjected to cyclic loading. The effectiveness of this innovative technique is presented considering the response of the masonry in- filled RC frame with and without retrofit. By comparison of the results, conclusions are drawn concerning design proce- dures.

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