International Concrete Abstracts Portal

Current design methods for predicting deflections and crack widths at service load in concrete structures reinforced with steel bars may not be necessarily applicable in those reinforced with fiber reinforced polymer (FRP) bars. In this paper, methods for predicting deflections and crack widths and spacing of glass fiber reinforced polymer (GFRP) reinforced concrete beams were proposed. In order to use the effective moment of inertia for concrete beams reinforced with FRP bars, the effect of reinforcement ratios and elastic modulus of the FRP reinforcement were incorporated in Branson’s equation. This paper also presents a new equation to predict crack width. Six concrete beams reinforced with different GFRP reinforcement ratios were tested. Deflections and crack widths were measured and compared with those obtained by the proposed models. The comparison between the experimental results and those predicted was in good agreement.

This paper summarizes research findings on the use of carbon fibre reinforced polymer (CFRP) sheets for shear strengthening of pretensioned AASHTO bridge girders. The research includes an experimental program conducted at the University of Manitoba using scale models of pretensioned concrete girders in composite action with the deck slab. Seven ten meter long beams were strengthened with three different types of CFRP sheets using ten different configurations and were tested to failure at each end. The paper describes the experimental program, test results, failure mechanisms and the effectiveness of each configuration of CFRP sheets. A rational model is introduced to define the contribution of the CFRP sheets to the shear resistance in addition to the contributions provided by the stirrups and the concrete for I-shaped pretensioned concrete members. Test results are used to verify the proposed model.

A series of R.C. beams were strengthened with carbon-fiber-reinforced plastic (CFRP) laminates and tested in an experimental program to study the influence of the cross-sectional area of the CFRP laminates on the shear capacity of the strengthened beam. The used technique enhances the flexural capacity of the original beam but at the same time may decrease the shear capacity. The strengthened beams are noticed to behave and fail through various modes. Also a general modified equation is proposed to predict the load carrying capacity of the strengthened beams taking into account all the existing parameters. The results obtained using the modified equation are discussed and evaluated according to the obtained experimental results.

Increasingly, existing concrete structures are being assessed as having insufficient capacity in shear; the development of an efficient and durable means of upgrading such structures is becoming of utmost importance. An exciting solution is the use of tensioned non-laminated carbon fiber reinforced plastic (CFRP) straps as active (stressed) external shear reinforcement for concrete. The use of an active system has several advantages over a passive (unstressed) reinforcement system. In particular, the prestressed CFRP straps provide confinement and enhance the performance of the concrete. Details of a series of tests carried out on a concrete beam strengthened using these novel CFRP shear reinforcing elements are presented. The strain in each of the straps was measured during testing and valuable insight into the shear behaviour of the concrete beam was gained. It was found that the strengthened beam had a much higher shear capacity than the predicted resistance of an equivalent unstrengthened beam.

This paper presents the results of an experimental investigation on the response of continuous reinforced concrete (RC) beams with shear deficiencies, strengthened with externally bonded carbon fiber reinforced polymer (CFRP) sheets. The experimental program consisted of nine full-scale, two-span, continuous beams with rectangular cross section. The tested beams were grouped into three series. Three beams, one from each series, were not strengthened and taken as reference beams, whereas, six beams were strengthened using different schemes. The variables investigated in this study included the amount of steel shear reinforcement, amount of CFRP, wrapping schemes, and 900/00 ply combination. The experimental results indicated that the contribution of externally bonded CFRP to the shear capacity of continuous RC beams is significant and is dependent on the tested variables. In addition, the test results were used to validate shear design algorithms. The proposed algorithms show good correlation with the test results and provided conservative estimates