A Study On The Cracking Behavior Of Gfrp Reinforced Concrete Beams

During the last years, the use of GFRP bars as internal reinforcement in concrete structures, gained more and more attention, as a good and sometimes a better alternative to steel reinforcement especially in corrosive situations and in aggressive environment. GFRP bars, which are fibers with high resistance immersed in a polymer resin matrix, with high tensile resistance and also resistant to corrosion, give better results regarding the tensile strength of the concrete structures, but due to their low elastic modulus and the poor bond with the concrete, as compared to steel reinforcing bars, the use of GFRP results in greater deflections and larger crack width under service loads.This paper aims to investigate the cracking behavior of GFRP reinforced members and their design based on SLS method as it represents the most problematic one, focusing on the cracking of GFRP reinforced beams. The work presented here includes the results from 4 GFRP beams tested. During the loading the cracks visible to the naked eye were marked with a pencil and photographed, creating a complete framework of the crack development in the beams until their destruction. The data related to the size of the cracks, the reductions, and the curvature of the beam as a function of loading, are recorded by the MGC device and elaborated in the form of graphs. Experimental data were analyzed and integrated in appropriate charts and are compared to predicted calculations based on American Code ACI 440.1R -06

SLS design of FRP reinforced concrete beams based on different calculation of effective moment of inertia

In this paper, reference is made to the key features of ACI, EC2 and other models, regarding SLS calculations of FRP reinforcement concrete and the comparison with steel reinforcement concrete formulas, especially focusing on deflection. Mechanical characteristics of FRP materials, such as lower elastic modulus, lower ratio between Young’s modulus and the tensile strength, lower bond strength of FRP bars and concrete, compared to steel reinforcement, make that SLS results determine the design of FRP reinforced concrete, based on the serviceability requirements. Different parameters influences affect the stresses in materials, maximum crack width and the allowed deflections. In this study we have calculated only the deflections of FRP-RC beams. Concrete beams reinforced with glass-fiber (GFRP) bars, exhibit large deflections compared to steel reinforced concrete beams, because of low GFRP bars elasticity modulus. For this purpose we have used equations to estimate the effective moment of inertia of FRP-reinforced concrete beams, based on the genetic algorithm, known as the Branson’s equation. The proposed equations are compared with different code provisions and previous models for predicting the deflection of FRP-reinforced concrete beams. In the last two decades, a number of researchers adjusted the Branson’s equation to experimental equations of FRP-RC members. The values calculated were also compared with different test results. Also it is elaborated a numerical example to check the deflection of a FRP-RC beam based on various methods of calculation of effective moment of inertia and it is made a comparison of results

A Study on Tibiofemoral Joint Contact Area Stresses using Finite Element Method

The joints of the human body act as mechanical or building structures joints. Joints connect different segments by enabling the movement of these segments. The design of a joint that provides durability or static support differs from that one which provides only movement. Joints of the human body, as organic joints, are considered more complex than other types of joints. Finite element models help to comprehend the knee structure behavior under the action of dynamic and static loads. Deformations in the articulating cartilage and the distribution of loads from meniscus provide data to understand the effect of loads in different part s of the knee. This study aims to calculate the stresses in the contact area of the tibiofemoral joint, using the finite element model. During this process, it will be an approximation of geometric shape of the femur, tibias and articulating cartilage to their real shape, taking into account the physic-mechanical characteristics of their components. The study, based on results of numerical calculations, aims to provide practical recommendations for dimensioning the tibiofemoral articulating cartilage and for the quality of the materials, to be used in knee prosthesis industry