International Concrete Abstracts Portal

Design guidelines for reinforced concrete structures (RC) with fibre reinforced polymers (FRP) use the concept of partial safety factors to ensure that structural safety is attained. However, when partial safety factors are used for the design of FRP RC structures, the structural reliability levels are not known. It is very important that structural reliability targets are met, in particular when there is a change in the predominant mode of failure. Furthermore, the resistance-capacity margins between various failure modes are not known. The work reported in this paper investigates these safety-related uncertainties. The notional structural reliability levels of two FRP RC beams are evaluated for the flexural and shear failure mode. The resistance-capacity margins for these two failure modes are also evaluated. Finally, the effect of the partial safety factors on the type of the expected failure mode is investigated.

The goal of this research is to evaluate the immediate deflections of concrete beams reinforced by carbon FRP grids with various fiber placement designs. Manufacturing and testing various FRP grid designs are the first steps toward the long-term goal of developing FRP reinforcement with optimized strength and serviceability performance. Four grid designs with stiffnesses that ranged from 47.1 kN/mm to 33.6 kN/mm, as determined from stand-alone tensile tests, were used as reinforcement in concrete beams and tested in flexure via three-point loading. The flexural results are in good agreement with the deflections as determined from a modified version of the ACI 318 flexure equations.

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.