International Concrete Abstracts Portal

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.

Large-scale (80%) tests were conducted on one "as-built" and four composite jacketed rectangular flexural bridge spandrel columns to assess the effectiveness of different retrofit schemes using fiber reinforced polymer composite jackets. Retrofit challenges were in (1) the unknown response of the inclined interface between spandrel column and the arch rib and (2) the behavior of the column reinforcement lap splice located at the top of the spandrel column pedestal. Three of the four FRP retrofit systems only addressed the lap splice region, where as the fourth system connected the column jacket to the arch rib to improve the column/arch rib interface response. Final damage patterns and failure modes showed that only the latter scheme improved the seismic response whereas the other systems resulted in a sliding failure mode without improving the displacement capacity which for the prototype bridge response is less desirable than the original “as-built” lap splice debonding failure. All retrofit schemes successfully clamped the column reinforcement lap splice above the column pedestal construction joint. The tests showed that fiber reinforced polymer composite jacketing systems clearly can be installed without affecting the overall geometry or appearance of the structure, and emphasizes the importance of designing retrofit strategies to control the mode of failure. Retrofitting of one weakness without considering the next mode of failure can lead to ineffective and poor designs.

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.