The most widely used material after water is the concrete composite. However, it is commonly accepted that concrete is weak in tension compared to its compression, therefore, conventionally, it is usually reinforced with steel rebars. Recently, reusing of waste plastic materials has become a norm among researchers whom used it in different forms in improving some mechanical properties of the concrete such as impact and tensile strength. However, using PET plastic strips as a replacement of main steel rebars is a novel idea. Therefore, in this study the experimental laboratory work is conducted to investigate the possibility of using waste plastic strips as a replacement of the main reinforcement steel bars to promote the flexural capacity of concrete beams at 28 days. For this purpose, a total number of 10 beams were casted with dimensions of (200mm x 200mm x 1200mm) to investigate the effects of using waste plastic strips in enhancing the bending capacity of the beams. The results showed that the incorporation of the plastic strips can improve the load carrying capacity and toughness of the concrete beams compared to unreinforced concrete beams.
Effects of various elevated heating temperatures on mechanical properties of normal concrete containing recycled tire rubber as a fine aggregate (RTRFA) has been investigated in this paper. Five different concrete mixes were prepared in the laboratory. In each mix Ordinary Portland Cement, natural coarse and fine aggregate, water and RTRFA are used with fine aggregate replacement ratios (0%, 6%, 12%, 18% and 24%) by weight. In the laboratory, 60 cylindrical specimens (100mm diameter × 200mm high) and 60 cubic specimens (150×150×150mm 3) were prepared. The concrete specimens were exposed to four different heating temperatures: Control (Not heated), 200, 400, and 600°C, and tested according to British standards to observe the postheating mechanical properties. These properties included density and mass loss, split tensile strength and compressive strength. The results showed a linear decrease in compressive strength with higher temperature degrees and percent replacement of fine aggregate by RTRFA. Moreover, the concrete's tensile strength fluctuated as it increased at 6% of rubber replacement then linearly declined at further replacement rates. Finally, some crucial conclusions of heating rubberized concrete have been drawn.
To increase the capacity load carrying of the beams, post tensioned metal straps are fully wrapped around the beams in their tensile zone in this study. In total four normal R.C beams with the depth of 160 mm, height of 240 mm and total length of 2100 mm are cast and tested under four-point load testing. The number of variables is kept to minimum of two which are the number and location of the straps. It is found that using post tensioned metal straps fully wrapped around the beams can increase the load-carrying capacity of the beams by 36% at least and 39% at a max. The main factor in influencing the rate is the location of the straps. A complete guide on using the material along with its application on the beams are explicitly described in the paper.
Fracture analysis of reinforced concrete deep beam strengthened with carbon fiber-reinforced polymer (CFRP) plates was carried out. The present research aimed to discover whether crack propagation in a strengthened deep beam follows linear elastic fracture mechanics (LEFM) theory or nonlinear fracture mechanics theory. To do so, a new energy release rate based on nonlinear fracture mechanics theory was formulated on the finite element method and the discrete cohesive zone model (DCZM) was developed in deep beams. To validate and compare with numerical models, three deep beams with rectangular cross-sections were tested. The code results based on nonlinear fracture mechanics models were compared with the experimental results and the ABAQUS results carried out based on LEFM. The predicted values of initial stiffness, yielding point and failure load, energy absorption, and compressive strain in the concrete obtained by the proposed model were very close to the experimental results. However, the ABAQUS software results displayed greater differences from the experimental results. For instance, the predicted failure load for the shear-strengthened deep beam using the proposed model only had a 6.3% difference from the experimental result. However, the predicted failure load using ABAQUS software based on LEFM indicated greater differences (25.1%) compared to the experimental result.
Fracture analysis of reinforced concrete deep beam strengthened with carbon fiber-reinforced polymer (CFRP) plates was carried out. The present research aims to find out whether the crack propagation in a strengthened deep beam follows linear elastic fracture mechanics (LEFM) theory or nonlinear fracture mechanics theory. To do so, a new energy release rate based on nonlinear fracture mechanics theory was formulated on the finite element method and the discrete cohesive zone model (DCZM) was developed in deep beams. To validate and compare with numerical models, three deep beams with rectangular cross-sections were tested. The code results based on nonlinear fracture mechanics models were compared with experimental results and ABAQUS results carried out based on LEFM. The predicted values of initial stiffness, yielding point and failure load, energy absorption, and compressive strain in the concrete obtained by the proposed model were very close to the experimental results. However, the ABAQUS software results have greater differences with the experimental results. For example, the predicted failure load for the shear-strengthened deep beam using the proposed model has only 6.3% differences compared to the experimental result. However, the predicted failure load using ABAQUS software based on LEFM has greater differences (25.1%) compared to the experimental result.
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