No abstract

The aim of this experimental study was to investigate the behaviour of reinforced concrete (RC) T-section beams that were strengthened by carbon fibre reinforced polymer (CFRP) plates. Six specimens, one of which was the control specimen and five of which were the shear deficient test specimens, were strengthened with side-bonded and t -jacketed CFRP plates. Unidirectional and bidirectional CFRP sheets were used as strengthening material. Distinct CFRP type, CFRP arrangement, number of sheet layers and wrapping schemes were the variables that were investigated during the experimental programme. The main objective of the study was to obtain ductile flexural behaviour from the shear deficient RC T-section beams. Debonding reduces the strengthening potential of the externally bonded CFRP thus obstructs structures to meet the expected requirement from strengthening materials. To block debonding, mechanical anchorages were used at the end regions of CFRP plates. Test results confirmed that all performance CFRP arrangements differ from type and wrapping scheme improved the strength and behaviour of the specimens in different level significantly. Nevertheless, specimens that were strengthened with t -jacketed bidirectional CFRP showed better strength and behaviour than the remaining specimens. To verify the reliability, test results were compared with results of ACI-440 design code and Concrete Society TR55. Notation a shear span d effective height of the cross-section f c compressive strength of concrete L length of the beam M cal calculated moment capacities of specimens M exp experimental moment capacities of specimens V exp: experimental shear forces of specimens V cal: calculated shear forces of specimens å CU maximum strain of concrete ö diameter of reinforcement Conversion factors 1 mm ¼ 0 . 039 in 1 mm 2 ¼ 0 . 00152 in 2 1 kN ¼ 0 . 2248 kips 1 MPa ¼ 145 lbf/in 2

INTRODUCTION Various strengthening materials and techniques were carried out all over the world in the last two decades, from a considerable need of repairing and retrofitting of existing structures. It is obvious that steel plates and fibre reinforced polymers (FRP) are the two most popular external shear-strengthening materials. Carbon fibre reinforced polymer (CFRP) may provide more economical and technically superior alternative to the traditional methods. CFRP sheets are cost-effective, durable, have good corrosion resistance, are non-magnetic, have excellent fatigue behaviour, ease of handling and installation, are tailorable, present minimal disruption to the structure function and have a high strength to weight ratio. Numerous studies have been undertaken in the structural flexural strengthening area. [1-3]. However, the shear strengthening studies of reinforced concrete (RC) beams by the use of CFRP have been limited and must certainly be expanded [3-6]. Many of the previous studies on shear strengthening were related to the effectiveness of CFRP as a shear strengthening material. Moreover, effects of parameters on the behaviour of shear deficient beams were examined in literature [7-9]. These parameters are shear span to depth ratio (a/d), composite materials strength and ratio, compressive strength of concrete, yield strength of shear and longitudinal reinforce-Letter