Ductility Research of Reinforced Concrete Beams Strengthened with CFRP

Abstract

Recently Carbon Fiber Reinforced Polymer (CFRP) is used to strengthen structural parts of reinforced concrete bridges. Nowadays, the research in this area is not so deep and mature although lots of experts all over the world have done a great deal of tests and theory analysis about strengthening the reinforced concrete beams by using CFRP. Especially, there is no further research on the ductility of RC beams strengthened with CFRP. This paper is based on our past research, to test and discuss the ductility of RC beams strengthened with CFRP. A series of RC beams were strengthened with CFRP and tested. According to comparison of the P~V curves, mid-span deflection, cracking load, strain within different teams, the authors analyze the ductility of the beams. It shows that the ductility of RC beams using the CFRP can be decreasing. This phenomenon must be paid attention in the construction. Finally, some conclusion and future works are given. IntroductionThe structure will go into elastic and plastic deformation when in the intense earthquake situation. Compared with the elasticity, the deformation of plasticity is too large to make the structure crack, and debond or even damage. On the other hand, because of the decreasing of structure stiffness on the elastic and plastic state, the period of self-oscillation increases. It changes the earthquake reacting characteristic of the structure. The non-elasticity un-recoverable distortion may consumes the input earthquake energy and decreases the affection of earthquake on the structure. On the nonlinear state, whether the structure is damaged or not is decided by the deformation of plasticity or dissipation energy instead of the intensity. Because one can not use the intensity condition to evaluate the anti-earthquake ability of the structure. To efficiently use the dissipation energy ability of the structural nonlinear deformation, at the same time, avoiding the damage caused by over large intense loss, over big plastic deformation and over long crack, it is

Fatigue lives of RC beams strengthened with CFRP at different temperatures under cyclic bending loads

“…The relevant factors r in Eqs (10) to (12) were separately 0.76, 0.84 and 0.86. P max (kN) was the maximum value of cyclic loads, and N (cycle) was the fatigue life of the test beam.…”

“…Research results showed that besides of same mechanical behaviour, fibre laminates (Carbon Fibre Laminates (CFLs), Aramid Fibre Laminates and High Strength Glass Fibre Laminates) had the features of variable size, saving material, short construction period and low cost. The features of fibre laminates have been confirmed in highway old bridges strengthening 11–14 . Concerning about temperature variations of practical bridge service environment in subtropical areas such as South China, this paper discusses the fatigue lives of RC beams strengthened with CFL from experimental studies and theoretical analyses in different environmental temperatures under cyclic bending loads.…”

“…The features of fibre laminates have been confirmed in highway old bridges strengthening. [11][12][13][14] Concerning about temperature variations of practical bridge service environment in subtropical areas such as South China, this paper discusses the fatigue lives of RC beams strengthened with CFL from experimental studies and theoretical analyses in different environmental temperatures under cyclic bending loads.…”

Experimental Study on the Fatigue Properties of RC Beam Strengthened by Prestressed CFL

“…More researches showed that the fatigue behavior of RC beams strengthened with CFRP/GFRP is mainly controlled by the stress level applied on the main reinforcements [4][5][6] . El-Tawil et al developed a model to describe the static and fatigue behavior of RC beams strengthened with CFRP [7] . The results were exactly suitable to the static behavior and the trend of fatigue behavior, but they were different with the results and the experimental data derived [3][4] .…”

OS4-3-2 Flexural Rigidity Evolvement RC Beams Strengthened with Carbon Fiber Laminate under Cyclic Bending Loads

“…There are many factors which can affect the failure of the RC beams strengthened with CFL, such as the CFL thickness and modulus of elasticity, the concrete compressive strength and the stress level et al Flexural rigidity is an important material parameter which can describe the fatigue behavior of the strengthened structures [8] . Yao et al proposed a structural damage cumulative model to describe the damage and fracture process of the strengthened beams [9] .…”