Research on Chloride Penetration Resistance of Hybrid Fiber Reinforced Self-Compacting Concrete
The properties of chloride penetration of hybrid fiber reinforced self-compacting concrete (SCC) were investigated in this study. The results show that the chloride penetration resistance of concrete can be improved by single incorporation either carbon or cellulose fibers. The concrete chloride diffusion coefficient DRCM of 12-cm length carbon SCC with fiber content of 1.7, 2.72, and 3.4 kg/m3 decreases by 10.3, 25.5, and 18.2% compared to reference concrete without any fibers, respectively. Moreover, the concrete chloride diffusion coefficient DRCM of cellulose SCC with fiber content of 1.2, 1.6, and 2.0 kg/m3 decreases by 18.8, 22.4, and 26.7% compared to reference concrete, respectively. Based on the results of orthogonal experimental design, the chloride diffusion coefficients DRCM of hybrid fiber reinforced SCC are listed in order of importance, as follows: length of carbon fiber > content of carbon fiber > content of cellulose fiber; furthermore, the hybrid of 2.72-kg/m3 carbon fiber with length of 12 mm and 2.0-kg/m3 cellulose fiber exhibits the most significant effect on chloride diffusion coefficients DRCM of SCC.
Flexural behavior of self-compacting concrete reinforced with different types of steel fibers
The aim of the present work is to investigate the flexural behavior of self-compacting concrete reinforced with straight and hooked end steel fibers at levels of 0.5%, 1.0% and 1.5% and compare it to normally vibrated concrete (NVC). The laboratory tests were determined according to RILEM TC 162-TDF recommendation. The flexural behavior of SCC appeared to be comparable to NCV, where the increase of fibers volume ratio cause the increase in prepeak and post-peak parameters of SCC. Nevertheless, the type of steel fibers influences much this dependency. Based on the performed analysis, the flexural tensile strength of SFR-SCC can be described with the formulas used for SFRC. The equation proposed to predict the deflection-CMOD relationship of SCC fits into the coefficient of variation of the formula for NVC. However, the SCC achieves the maximum crack mouth displacement for lower deflections than NVC. The article contains also the analysis of the fracture energy of SCC with a formula to describe it.
Evaluation of buckling load and dynamic performance of steel shear wall retrofitted with strips made of shape memory alloy
One of the most imperfections of the steel shear wall is out of plane displacements that cause severe damage in both structural and non-structural elements. In this paper, the effects of shape-memory alloys on steel shear walls are investigated. First, a numerical analysis using the finite element method in ABAQUS software has been carried out according to an experimental test. The results of the numerical analysis have been verified with experimental results. Next, shape-memory alloy fibers have been added vertically and horizontally to various parts of the steel shear wall. The results show that retrofitting with the shape-memory alloy reduces the out-of-plane displacement of the steel shear wall under both cyclic and seismic loadings. Besides, the buckling load in the steel shear wall increases when it is retrofitted with the shape-memory alloy. Also, the total out-of-plane movement (accumulated absolute displacements) of the steel shear wall and non-structural damage are controlled by the characteristic of a shape-memory alloy material called “super-elastic”.