Factorial experimental design was adopted in this investigation to assess the combined effects of the following factors on workability and compressive strength: (a) water to cement ratio (W/C), (b) total aggregate to cement ratio (TA/C), (c) fine to total aggregate ratio (FA/TA), and (d) hot-weather conditions in terms of concrete mixture temperature at placement and curing conditions. The experimental data was thereafter subjected to regression analysis to develop reliable models for predicting workability in terms of the slump and compressive strength of a concrete mixture. Results of this study indicate that lowering the concrete mixture temperature at placement alone, as recommended in the codes of practice, does not eliminate the adverse effect of hot weather on compressive strength.
The objective of this study is to conduct a finite-element (FE) numerical study to assess the effect of size on the shear resistance of reinforced concrete (RC) beams strengthened in shear with externally bonded carbon fibre-reinforced polymer (EB-CFRP). Although a few experimental studies have been done, there is still a lack of FE studies that consider the size effect. Experimental tests are time-consuming and costly and cannot capture all the complex and interacting parameters. In recent years, advanced numerical models and constitutive laws have been developed to predict the response of laboratory tests, particularly for issues related to shear resistance of RC beams, namely, the brittle response of concrete in shear and the failure modes of the interface layer between concrete and EB-CFRP (debonding and delamination). Numerical models have progressed in recent years and can now capture the interfacial shear stress along the bond and the strain profile along the fibres and the normalized main diagonal shear cracks. This paper presents the results of a nonlinear FE numerical study on nine RC beams strengthened in shear using EB-CFRP composites that were tested in the laboratory under three series, each containing three sizes of geometrically similar RC beams (small, medium, and large). The results reveal that numerical studies can predict experimental results with good accuracy. They also confirm that the shear strength of concrete and the contribution of CFRP to shear resistance decrease as the size of beams increases.
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