This paper presents a nonlinear finite element model to investigate the behavior of hybrid Fiber Reinforced Polymers and steel reinforcement. Different types of Fiber Reinforced Polymers; CFRP and GFRP; were used along with steel rebars in the studied concrete beams. The study was conducted using the nonlinear finite element program ''ANSYS". Nonlinear material models for the components of the concrete beam were used in the three dimensional finite element models. The outcomes got from finite element analysis were confirmed against experimental results. A broad parametric study was conducted to explore the effect of replacing steel reinforcement by different types of FRP bars. The study showed that the contribution of steel rebars to FRP rebars in concrete beams improved beam ductility and eliminated the unfavorable brittle failure of the concrete beam. In addition, it is better to use steel rebars as top reinforcement in concrete beams with hybrid reinforcement. In hybrid GFRP/steel reinforced concrete beams, a significant reduction in stiffness and a noticeable increase in the beams' deflection after the initiation of first crack and yielding of steel reinforcement were observed. On the other hand, in hybrid CFRP/steel reinforced concrete beams showed a better performance during cracking initiation and propagation.
Our present study aims to investigate the optimal use of waste tire rubber as a fine aggregate in concrete and their sensitivity to high temperature effect. Five different concrete compositions were prepared: a reference concrete (RC) made with natural fine aggregate (sand) and coarse aggregate (dolomite) and four concrete mixes with replacement rates of 4%, 8%, 12% and 16% of sand by crumb rubber from waste tires. For the effect of elevated temperature: Similar specimens were exposed to a period of 4 hours to temperature of 70°C, to study the effect of high daily temperature, and a period of 2 hours for both temperatures 200° C and 400° C to study the effect of fire. After cooling down to ambient temperature, the compressive strength, flexural strength and the splitting tensile strength were measured and compared with the values that obtained before fire exposure. The inhand study indicates a gradual decrease in compressive, splitting and flexural strengths of concrete for partial substitution of crumb rubber aggregate in concrete. In addition, more decrease in these strength values are resulted after exposing the similar specimens to high temperature. While the inclusion of rubber particles reduces the rate of compressive strength loss at high temperature.
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