VALIDATION OF ANALYTICAL MODELS FOR THE ASSESSMENT OF BRICK-INFILLED RC FRAMES STRENGTHENED WITH FRPS

Numerous modern seismic codes including Eurocode 8 provide rules to avoid possible adverse impact of the presence of masonry infills in concrete buildings or unbraced steel or composite structures.These adverse effects include damage of columns in contact with strong infills, reduction of the clear column height because of partial contact with masonry along height, planwise and heightwise irregularity.However, codes emphasize on the design of new structures, while little information is provided on modeling of masonry infills.Conversely, when the seismic upgrading of existing structures is performed with those methods that have received wider application in engineering practice, i.e., strengthening of columns and beams with reinforced concrete (RC) jackets or Fiber Reinforced Polymers (FRPs), construction of additional RC shear walls and construction of diagonal steel elements, any beneficial effect of masonry infills is usually ignored.The present research examines the effectiveness of strengthening existing RC frames with the application of FRP sheets on their brick-infill walls.This recently proposed method uses the advantageous mechanical properties of FRPs and is characterized by relatively low cost and ease of implementation compared to other aforementioned available retrofit schemes.A multi-strut masonry panel element is used to simulate the nonlinear response of the infill wall, while the FRP contribution to the response is modeled with a tension tie.Experimental results available in the literature for a scaled reinforced concrete frame are used to calibrate the parameters of the numerical model.Comparisons are made between the analytically and the experimentally derived results, and the effectiveness of the retrofit scheme is assessed.Also a simple method to modify the lateral stiffness of masonry infills to account for the presence of openings is addressed.