Varying Lateral Stiffness and Improve Response Using FRP Retrofitting of RC Structures Under Seismic Excitation

Abstract

R.C structures have a certain age after which they are not safe to use. They deteriorate over time and become unsuitable for the purpose they were built for. R.C structures could be in the form of beams, columns, footings, slabs, girders, pylons etc but the scope of this project is limited to beam-column joint only. Retrofitting techniques are of various kinds that are used in industry with both advantages as well as drawbacks. Retrofitting techniques are more suitable, especially for a country like Pakistan, where weak economy and high inflation rate are prevalent. Retrofitting techniques are only used when the structure has not been completely damaged. Instead of replacing damaged structures, effective techniques of repairing can result in time saving and minimal cost. Fiber Reinforced polymers (FRP) is relatively new class of complex materials which has demonstrated itself effective and efficient for the advancement and repair of new and decayed structures in development industry. Due to its high quality to weight proportion, FRP's and have been broadly utilized as a part of created nations for retrofitting and other support activities. Even though in Pakistan, this innovation should be featured. Most of the designers and consultancy firms are hesitant to utilize this innovation likely on the grounds that they have enough trust in established strategies. What are FRPs? These have been utilized in the construction industry for the making of roofs for parking lots and other light-weight temporary structures. The FRPs are now being used in the construction industry where the buildings are prone to earthquakes of high intensity. The FRPs are being utilized in the retrofitting of the damaged buildings that have been affected under earthquakes. The FRPs don’t add to the compressive strength of the concrete but they add sufficiently to the flexural strengths of the concrete, improve overall strength of the concrete, lessen the reinforcement requirement of the steel, increase the ductility (post cracking), increase the abrasion resistance of concrete. There are many other types of fiber reinforced polymers that are available in the market, some of them include as CFRP, BRRP and GFRP. We utilized FRPs in our project because of the reason that it is easily available in the market at low cost. Moreover, our project is to strengthen the column-beam connection under the seismic excitation. Several samples were made of concrete cylinders. There compressive strengths as well as flexure strength of the controlled, single, double and triple wrapped cylinders were measured. The tests of cylinders clearly showed a important improvement in the lateral stiffness of the concrete cylinders. The results obtained during our experimentation would be further discussed in this paper. The objective of this project is to present a cheaper solution of retrofitting/repair damaged beams. One possible option is to repair the damaged sections using Fiber Reinforced Polymers.