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.

This paper describes the Joffre Bridge project where Carbon Fiber Reinforced Polymer (CFRP) was used as reinforcement for a portion of the concrete deck-slab is reinforced with reinforcement. The Joffre bridge, located over the St-François River in Sherbrooke, Quebec, Canada, consists of five longitudinal spans with length varying from 26 to 37 meters. Each span consists of a concrete deck supported by five steel girders at 3.7 meters. This spacing constitutes the highest span using FRP reinforcement. A Part of the concrete deck slab (7.3 m x 11.5 m) and a portion of the traffic barrier and the sidewalk was reinforced with Carbon and Glass Fiber Reinforced Polymer (FRP ) reinforcement. In addition, four FRP reinforced full-scale one-way concrete slabs were laboratory tested under static and cyclic loading, in order to optimize the design process. The bridge was extensively instrumented with different types of sensors, including integrated fiber optic sensors in FRP reinforcement that were integrated into the FRP reinforcement. The results of the laboratory study, in terms of deflection and crack-width versus applied load, as well as the results of calibrated loads, using heavy trucks, are also presented in this paper.

This paper presents an evaluation method of contribution of continuous fiber sheet to shear capacity of RC members. Different from mild steel, CF sheet is completely elastic up to breaking point without any yielding phenomena. CF sheet works effectively in shear strengthening of concrete members when it is glued on concrete. To evaluate shear contribution of CF sheet rationally, it is necessary to consider bonding and peeling-off behavior of CF sheet. In this paper, we formulate a constitutive model for the interfacial zone between CF sheet and concrete according to the uniaxial test results. Based on this computational model, we propose the evaluation system for shear capacity of RC member retrofitted with CF sheets. The applicability of the proposed method is verified with test results of RC beams.

In this paper, the crack propagation along FRP-concrete interface of FRP-strengthened concrete structures is analyzed by using nonlinear fracture mechanics, in which the concept of mode II fracture is applied to describe the interfacial fracturing behavior by means of a cohesive crack model with a local shear stress-slip relationship. Two types of the shear stress-slip relationship were proposed, and have been implemented with the mixed finite element methods to perform numerical simulations. A simulation for a simple shear test is carried out to verify the interface crack model. It is found that the interfacial fracture energy is the most important parameter for the bond behavior and the ultimate load can be expressed in terms of the fracture energy. The finite element numerical results agree with the theoretical derivation. Choosing different bond strength and shear stress-slip relationship may influence the effective bond length between FRP sheets and concrete. In addition, an example of a FRP-strengthened concrete beam is also analyzed, in which the composite behavior is significantly dependent on the bond strength of strengthened beam, and the debonding propagation and the failure load due to debonding may also be expressed with fracture energy. The fact that cracks are localized or distributed, for plain concrete beams without reinforcing steel bars, is regarded to be affected by bond strength, interfacial fracture energy, concrete tensile strength and mode I fracture energy of concrete.