الفهرس | Only 14 pages are availabe for public view |
Abstract ABSTRACT Corrosion of steel reinforcement in aggressive environments can cause considerable damage in reinforced concrete (RC) structures. Fiber reinforced polymer (FRP) bars have emerged an alternative to steel for RC elements subjected to those environments, Its non-corrosive nature has turned the attention of many researchers to carry out several studies on different types of FRP products. Through a vast research, several standards also have been formulated. In this regard, a new combination of FRP materials is examined in this study and its properties have been derived. Carbon fiber and glass fibers fuse in this study to form a new hybrid rebar. In order to improve the structural performance of GFRP reinforced concrete member, one alternative solution have been proposed, such as using a hybrid reinforcement (CFRP rods and GFRP bars) as a main reinforcement. Carbon fiber provides even higher tensile strength and more elastic modulus than steel. These are advantageous features of using carbon fiber in a structural point of view but not in economics, since its price is almost ten times higher than glass fiber. The concept of “hybridization” was arisen for the FRP rebar to overcome their shortcomings. The mechanical properties of FRP bars can yield to large crack widths and deflections. As a result, the design of concrete elements reinforced with FRP materials is often governed by the serviceability limit states (SLS). This study investigates the behavior of flexural and serviceability conditions of concrete beams reinforced with FRP bars and hybrid bar under static loads through theoretical and experimental analysis each measuring 150 x 250 x 2036 mm. All the studied beams tested under four-point loading. The main variables considered in the study are the concrete grade; the reinforcement ratio and the hybridization ratio CFRP to GFRP (ACFRP /( ACFRP +AGFRP)). Deformations on the concrete and on the reinforcement and crack width and spacing are measured and analyzed. The ABSTRACT 2 experimental results are discussed and compared to some of the most representative prediction models of deflections and cracking for steel and FRP RC. Results showed that, in general Hybrid rebar showed a superior performance in comparison with GFRP. A discussion on the main aspects of the SLS of FRP RC is introduced. The influence of the different parameters affecting the stresses in materials, maximum crack width and the allowable deflection is studied and analyzed. It is reported that at a cross-section level, for lightly reinforced members, the crack width limitation results are more restrictive than the stresses in concrete. However, for sections with high reinforcement ratios, the predominant restriction is the concrete stress. Because SLS result determining for the design of FRP RC beams, a methodology is presented for the design of FRP RC at the serviceability requirements. Crack pattern, final modes of failure, load carrying capacity, service load, CFRP rod, GFRP and steel tensile strain, mid span deflection, concrete strain, crack spacing, and the crack width were recorded. The comparison between the predicted values of cracking and ultimate loads, midspan deflection and the maximum crack width estimated using some of the available formulae found in literature and the corresponding experimental results are also presented in this thesis |