A COMPARATIVE STUDY ON RETROFITTING OF REINFORCED CONCRETE BUILDING USING STEEL BRACING AND INFILL WALL

Abstract

For different reasons, such as changes in service conditions, environmental conditions, seismic code, or low quality of operation, it may become necessary to upgrade or strengthen an existing building. Many techniques may used to retrofit concrete structures on a local or global basis. The main objective of this study is to compare steel bracing and infill wall intervention techniques for retrofitting RC buildings. Four, seven, and ten storey moment-resisting frames of medium ductility class were designed according to ES-EN 2015 for high seismicity region (Zone V), to study the effect of infill wall and steel bracing on seismic response of RC buildings by comparing with bare frame, masonry infill wall and steel bracing (concentric X-bracing) were introduced at the corner bays of the ground floor separately. The modeling and design of the building were done by using ETABSv18.1.1 structural design and analysis software. Linear dynamic and nonlinear static (pushover) analyses were conducted to evaluate the seismic response of the building. From the linear dynamic analysis it was found that, adding infill wall to the bare frame reduces top floor displacement by 8%, 6%, and 2%, the maximum drift at the critical storey of the building by 6%, 6% ,and 2%, and increases the average lateral stiffness of the building by 13%, 10%, and 5 %,adding steel bracing to the bare frame reduces the top floor displacement by 21%, 20% ,and 12%, the maximum drift at the critical storey of the building by 13%, 24%, and 11% ,and increases the average lateral stiffness by 64%,58 %, and 57% ,for G+3, G+6, and G+9 buildings respectively. From the conducted nonlinear analysis, the pushover curve shows that both retrofitting techniques increases the lateral load-carrying capacity and they change the pattern and order of plastic hinge formation in the building, by preventing plastic hinges from developing in the columns at lower stories. The lateral load carrying capacity was increased by 6.76% for infilled frame, and by 21.09% for braced frame. As the height of the building increases infill wall is found to be not as effective as steel bracing