Mechanical Efficiency of Locally Available Bonding Materials Used for Strengthening of Steel Structures using carbon fibers reinforced polymers (CFRP)

Abstract

The main goal of this research is to evaluate the mechanical efficiency of the locally available bonding materials in Egypt used to bond carbon fibers to the surface of different steel elements for repair and strengthening purposes. To achieve this goal a review of previous studies and an experimental investigation were carried out and were illustrated in details throughout the different chapters of this thesis. The literature review included the repair and strengthening techniques of steel structures, focusing on the technique using carbon fiber reinforced polymers (CFRP), indicating its advantages, disadvantages, mechanical properties, methods to improve the CFRP-Steel connection and the durability of FRP-Steel connections. Five case studies were also discussed of steel structures repaired and/or strengthened by CFRP. The experimental study carried out in this research was divided into two stages. The first stage was to investigate the efficiency of the aforementioned bonding materials by testing specimens in tension, single shear, and double shear. The first stage was carried out on two commonly used materials in the Egyptian market, denoted to as I and II bonding materials throughout the study. Also two types of carbon fibers were considered and combinations were made with the bonding materials. The experimental results obtained in this stage were used to establish the efficiency of these two bonding materials with carbon fiber laminates on steel members. In the first stage material (I) recorded better performance in all tests, thus it was used in the second stage. The second stage of the experimental work investigated the efficiency of the selected CFRP and bonding material, based on the results of the first stage, in the repair and strengthening of full scale steel beams. Four full scale steel beams were tested. The first beam, denoted to as (CL), was the control beam. The second beam, denoted to as (ST), was a steel beam strengthened by carbon fibers using the best bonding material as mentioned before. The third one, denoted to as (RP), was a steel beam with a cut in the lower flange and was repaired using the same carbon fiber laminates and bonding materials mentioned before. The last beam, denoted to as (FS), was a steel beam fully cut and fully spliced by CFRP. The experimental results of the second stage indicated that using CFRP improved the mechanical properties of the steel beams by improving the ultimate strength values and the overall stiffness values of the tested beams.