Hybrid fiber reinforced concrete (HFRC) is based on a multilevel-reinforcement material design that improves both the compressive strength and tensile strength. Investigations of the mechanical performance of HFRC with two types of steel fibers were conducted experimentally. The investigated parameters were the volume fractions of the short steel fibers and long steel fibers. The compressive strength, tensile strength, and flexural strength of the HFRC were researched. The group with volume fractions of 1.5% for the long steel fibers and 0.5% for the short steel fibers exhibited the best flexural strength. The synergetic effect clearly was improved by combining different types of steel fiber. Four HFRC deep beams and one reinforced concrete (RC) deep beam were conducted to consider the shear behavior of these beams. The primary variables included the volume fraction of steel fibers and the web reinforcement ratio. The shear behavior was evaluated based on the cracking pattern, load-deflection behavior, and shear capacity. All of the beams failed due to the formation of diagonal cracks. The results indicated that hybrid fibers contribute greatly to the shear behavior of deep beams. The hybrid fibers led to the formation of multiple diagonal cracks in the deep beams and enhanced the damage tolerance. With the same web reinforcement ratio, the ultimate load and deformation of the HFRC deep beams were better than those of the RC deep beam.
Summary An innovative double steel concrete (DSC) composite walls were developed to enhance constructability and lateral load resistance of buildings. In order to research the seismic behavior of DSC composite walls, experimental study was carried out. The high‐strength concrete and high axial load were considered. The failure mode, hysteresis behavior, lateral load‐carrying capacity, deformation, and energy dissipation of the composite walls under different testing parameters were observed. All specimens failed in a flexure behavior, with steel plate buckling and concrete compressive crushing in the bottom of composite walls. The pinching behavior was not significant for hysteresis loops of composite walls. Moreover, the lateral load‐carrying capacity and ductility coefficients increased significantly with spacing of constraining bolts and stiffeners decreased. In addition, the calculation method of the lateral load‐carrying capacity of DSC composite walls was proposed, with the consideration of force equilibrium and moment equilibrium. The finite element (FE) method was performed to analyze the failure process of the specimens with the cyclic load. The concrete damage plastic model was selected to simulate the damage progress of concrete. Validation of the FE models against the experimental results showed good agreement. The effect of different parameters was analyzed with FE models.
A constitutive model of confined ultra-high-performance concrete (UHPC) was developed based on the theoretical and regression analyses. This constitutive model could be applied to finite element analysis (FEA) according to the comparison of plastic damage analysis and load–displacement curves. A total of 25 stirrup-confined UHPC columns were created through FEA modeling. The variables included stirrup spacing, stirrup configuration, steel fiber volume, and longitudinal reinforcement ratio. The load–displacement curves and the plastic damage region of the UHPC columns were illustrated and analyzed. Moreover, parametric analysis was conducted to evaluate the effects of the aforementioned parameters. The improvement in the bearing capacity and ductility of the UHPC columns resulting from the reduction in stirrup spacing and increase in steel fiber volume indicated that the columns were significantly influenced by the stirrup spacing, stirrup configuration, and steel fiber volume.
An innovative double steel concrete (DSC) composite wall was developed to enhance constructability and lateral load resistance of buildings. Three low-aspect ratio DSC composite walls were constructed and tested to study the shear behavior. Under different testing parameters, the failure modes, hysteresis behavior, lateral load resisting capacity, deformation, and energy dissipation of the composite walls were observed. The results showed that all specimens failed in shear behavior with steel plate buckling and concrete compressive crushing. The pinching behavior was obvious for hysteresis loops of composite walls. Moreover, the lateral load resisting capacity and deformation were significantly affected with axial compression ratio and steel ratio. Beyond that, the ductility coefficients of specimens reached 3.30. The finite element (FE) method was performed to analyze the failure process of the specimens with cyclic analysis. The concrete damage plastic model (CPDM) was selected to simulate the damage progress of concrete. Validation of the FE models against the experimental results showed good agreement.
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