International Concrete Abstracts Portal

This paper presents an experimental study into the structural response ofGlass Fiber Reinforced Polymers Reinforced Concrete (GFRP-RC) tension members. Theinfluence of concrete strength, reinforcement ratio and bar diameter on tensionstiffening is investigated by testing elements in direct tension. Using bars speciallymanufactured with internal strain gauges, typical strain patterns occurring betweencracks during direct tension tests were measured and bond stresses derived, therebyobtaining the information for modeling tension stiffening behavior of GFRP-RC. Anincrease in the tension stiffening behavior with decrease in reinforcement ratio andincrease in concrete strength was observed. No appreciable change in tensionstiffening was recorded with changes in bar diameter at constant reinforcement ratio.This paper also discusses the limitations that may be encountered in modifying currentmodels to represent the tension stiffening effect of GFRP-RC.

The main objective of this study was to develop a nonferrous hybridreinforcement system for concrete bridge decks by using continuous fiber-reinforced-polymer (FRP) rebars and discrete randomly distributed polypropylene fibers. Thishybrid system has the potential to eliminate problems related to corrosion of steelreinforcement while providing requisite strength, stiffness, and desired ductility, whichare shortcomings of the FRP reinforcement system in reinforced concrete structures.The overall study plan includes (1) development of design procedures for an FRP/FRChybrid reinforced bridge deck system; (2) laboratory studies of static and fatigue bondperformances and ductility characteristics of the system; (3) accelerated durability testsof the hybrid system; and (4) static and fatigue tests on full-scale hybrid reinforcedcomposite bridge decks. This paper presents the results relating to the flexuralbehavior of the polypropylene-fiber-reinforced-concrete beams reinforced with FRPrebars.Test results indicated that with the addition of fibers, the flexural behavior wasimproved with an increase of ductility index by approximately 40% as compared to theplain concrete beams. Crack widths of FRP/FRC were found to be smaller than those ofFRP/plain concrete system and the values predicted by the current ACI 440 equations.Furthermore, the compressive failure strains of concrete in FRP/FRC beams exceed thestrain of 0.0040 mm/mm.

This paper presents the results of a finite element analysis for threedifferent bridges that have been recently constructed and tested in North America. Inthese bridges, different types of reinforcement (steel and FRP reinforcing bars) wereused as reinforcement for the concrete deck slabs. Two bridges, Magog Bridge andCookshire-Eaton Bridge, are located in Quebec, Canada, while the third one,Morristown Bridge, is located in Vermont, USA. The three bridges are girder-type withmain girders made of either steel or prestressed concrete. The main girders were eithersimply or continuously supported over spans ranging from 26.2 to 43.0 m. The deckwas a 200 to 230 mm thickness concrete slab continuous over spans of 2.30 to 2.8 m.Different types, sizes, and reinforcement ratios of glass and carbon FRP reinforcingbars were used. Furthermore, the three bridges are located on different road orhighway categories, which mean different traffic volumes and environments. Thebridges were tested for service performance using calibrated truckloads. The results ofthe field load tests were used to verify the finite element model. Comparisons showedthat FEM can predict the behavior of such elements. Then, the model was used toinvestigate the effect of the FRP reinforcement type and ratio on the service andultimate behavior of these bridge decks. According to the findings, a proposedreinforcement ratio was recommended and verified using the FEM to meet the strengthand serviceability requirements of the design codes.

The punching shear capacity of concrete slabs reinforced with three-dimensional fiber-reinforced polymer (FRP) double-layer reinforcement cagescomposed of glass fiber-reinforced pultruded grating elements has been investigatedusing full-scale experimental tests and a number of different analytical models. Testspecimens were full-scale prototype bridge deck slabs with varying end restraint andsupport conditions, differing dimensions, and two different FRP bar fiber lay-ups. Thetests results were compared with the punching shear models in ACI 318, ACI 440,Eurocode 2, BS 8110, CEB-FIB MC90, JSCE, and a number of models proposed in theliterature specifically for FRP reinforced slabs. Based on this investigation a newempirical model has been developed to predict the punching shear capacity of doublelayer grids having either restrained or simply supported edges and including anoverlapping splice. The model is shown to give reasonably good predictions for bothsimply supported and restrained slabs.

This paper presents an analytical investigation conducted to study theflexural behavior of reinforced concrete beams strengthened with various Near-SurfaceMounted (NSM) Fiber-Reinforced Polymers (FRP) reinforcements. The materials used inthis investigation included carbon-fiber-reinforced-polymer (CFRP) rebars and strips,and glass fiber-reinforced-polymer (GFRP) rebars and strips. The analysis included theeffects of strengthening on the serviceability and ultimate limit states as well the effectof tension stiffening. The effectiveness of NSM FRP rebars and strips was examined andcompared to externally bonded (EB) FRP strips and sheets using the same material typeand axial stiffness. Results from the analytical models were compared with thoseobtained from experimental studies. The analytical results agree very well with thoseobtained from the experimental results. It was found that the analytical model couldeffectively simulate the behaviour of the reinforced concrete beams strengthened withvarious NSM FRP and EB FRP reinforcements. Using the same axial stiffness of FRP tostrengthen reinforced concrete beams, the beams strengthened with NSM FRPreinforcement achieved higher ultimate load than beams strengthened with EB FRPreinforcement. This result is due to the high utilization of the tensile strength of the FRPreinforcement.