SEISMIC STRENGTHENING OF A MID-RISE REINFORCED CONCRETE FRAME USING CFRPs: AN APPLICATION FROM REAL LIFE Tan, Mustafa T&uuml / mer M.S., Department Of Civil Engineering Supervisor: Prof. Dr. G&uuml / ney &Ouml / zcebe Co-Supervisor: Assoc. Prof. Dr. BariS Binici May 2009, 162 pages FRP retrofitting allows the utilization of brick infill walls as lateral load resisting elements. This practical retrofit scheme is a strong alternative to strengthen low to mid-rise deficient reinforced concrete (RC) structures in Turkey. The advantages of the FRP applications, to name a few, are the speed of construction and elimination of the need for building evacuation during construction. In this retrofit scheme, infill walls are adopted to the existing frame system by using FRP tension ties anchored the boundary frame using FRP dowels. Results of experiments have previously shown that FRP strengthened infill walls can enhance lateral load carrying capacity and reduce damage by limiting interstory drift deformations. In previous, analytical studies, a detailed mathematical model and a simplified version of the model for compression struts and tension ties was proposed and verified by comparing model estimations with test results. In this study, an existing 9-storey deficient RC building located in Antakya was chosen to design and apply a hybrid strengthening scheme with FRPs and reduced number of shear walls. Linear elastic analysis procedure was utilized (force based assessment technique) along with the rules of Mode Superposition Method for the reftrofit design. FRP retrofit scheme was employed using the simplified model and design was conducted such that life safety performance criterion is satisfied employing elastic spectrum with 10% probability of exceedance in 50 years according to the Turkish Earthquake Code 2007. Further analytical studies are performed by using Modal Pushover and Nonlinear Time-History Analyses. At the end of these nonlinear analyses, performance check is performed according to Turkish Earthquake Code 2007, using the strains resulting from the sum of yield and plastic rotations at demand in the critical sections. CFRP retrofitting works started at October 2008 and finished at December 2008 for the building mentioned in this study. Eccentric reinforced concrete shearwall installation is still being undertaken. All construction business is carried out without evacuation of the building occupants. This project is one of the first examples of its kind in Turkey. Keywords: CFRP, Carbon Fiber Reinforced Polymers, Masonry Infill Walls, Reinforced Concrete Infill Walls, Mid-Rise Deficient Structures, Turkish Earthquake Code 2007, Modal Pushover Analysis, Nonlinear Time History Analysis, Linear Elastic Building Assessment

<p> A moment resisting frame is one of the most commonly used lateral load resisting system in modem structures because it is suitable for low and medium rise buildings and industrial structures. It can be designed to behave in a ductile manner under seismic loads. </p> <p> Masonry infills have traditionally been used in buildings as partitions and for architectural or aesthetic reasons. They are normally considered as non-structural elements, and their effect on the structural system has been ignored in the design. However, even though they are considered non-structural elements, there is mounting evidence that they interact with the frame when the structures are subjected to lateral loads Infill walls have been identified as a contributing factor to catastrophic structural failures during earthquakes. Frame-infill interaction can induce brittle shear failures of reinforced concrete columns by creating a short column. Furthermore, infills can over-strengthen the upper stories of a structure and when they fail a soft first storey is created, which is highly undesirable from the earthquake resistance standpoint. </p> <p> There is a need for an efficient and accurate computational model to simulate the nonlinear hysteretic force-deformation behaviour of masonry infills, which is also suitable for implementation in time-history analysis of large structures. The aim is to develop a simplified advanced and cost-effective model for nonlinear time history analysis and seismic design of masonry infill frame structures. </p> <p> The objective of this research was to develop a practical and economical technique applicable for global analysis of general three-dimensional reinforced concrete infilled frames under lateral loads. Novel finite element model for the infill and the surrounding frame was developed using a special finite element configuration to represent the masonry panel. Some prescribed failure planes in different directions were defined depending on the common failure mode of masonry panels. Moreover, some of contact elements were used on the failure planes to connect among the panel elements, and between the panel elements and the boundary reinforced concrete frame. Different material models were used to represent the behaviour of concrete, reinforcing steel, mortar joints and inclined saw-tooth cracks in the infill panel. Different material models were used to describe the behaviour through and perpendicular to the prescribed failure planes. The proposed model and the used material models were described in details in the first part of this research. </p> <p> The proposed finite element model was verified against experimental and analytical results previously published by others. Different frames configurations, reinforcing details, boundary conditions and material properties were consider in that section to verify the capability of the proposed model to simulate the behaviour of different frames. The overall behaviour "Load-deflection relationship", failure point and failure mode were compared with the experimental and analytical results. Satisfactory agreement with the previously published results was obtained. </p> <p> The study investigates the capability of the proposed model to simulate the behaviour of infilled frames subjected to cyclic loads. Hysteretic loops obtained by using the new model were verified against experimental and analytical results and good correlation were obtained. The failure modes and crack patterns were compared with the experimental results and good agreements were obtained. The proposed model failed to capture some shear cracks in the RC frames as per the experimental results. </p> / Thesis / Doctor of Philosophy (PhD)