Special-Shaped Concrete-Filled Steel Tube (SCFST) columns have a higher bearing capacity, ductility, and energy absorption compared to other columns. Due to their special shape, the columns can be utilized in different parts of the building without protrusion of member. In L-shaped CFST columns, this study investigated the effect of various parameters (such as yield stress of the steel wall, characteristic strength of the concrete, height of the column, thickness of the steel wall, and geometry of the stiffeners) on the eccentric load-bearing capacity. In other words, the bearing capacity has been measured based on the optimal performance of these columns under the effect of axial and eccentric loads. Also, the ratio of load-to-weight (p/w) has been considered. Load-displacement diagrams and the weight of steels used in different columns are compared. Based on the obtained results, the changing of the thickness and strength of the steel wall has a significant effect on increasing the bearing capacity. Whereas, the concrete strength has a lesser impact on the bearing capacity of the columns. The column with greater thickness performs better than the column with less thickness in terms of ductility and energy absorption capacity under eccentric loading.
Immediate dimensional changes during loading are critical characteristics that must be thoroughly understood to ensure the long-term durability and performance of concrete. In the current study, the effects of fixed bacterial content and different macro-synthetic fibre mechanical properties and fibre percentages on concrete dimensional changes were evaluated using 34 mixed designs. The influence of low-and high-strength macro-synthetic fibre with nine contents ranging from 0% to 4% on M40 concrete was investigated with and without calcium carbonate precipitation of Bacillus subtilis activity at a cell concentration of 105 cells/ml. The ANSYS package was used to compute the homogenized properties of the composite materials, such as the elastic modulus, shear modulus, and Poisson's ratio. For validation, the numerical results showed good agreement with the analytical results of the dilute distribution model and the Mori-Tanaka model. Compared to the reference conventional concrete, the results showed that adding bacteria and 2% high-strength macro-synthetic fibre simultaneously improved elasticity, shear moduli, and Poisson's ratio by 17.89%, 15.16%, and 3.30%; however, low-strength macro-synthetic fibres caused 3.54%, 1.32%, and 2.98% reduction, respectively. Overall, high-strength macro-synthetic fibre improves the properties of bacterial concrete composite for a variety of structural applications when compared to other traditional concrete.
This study evaluates the performance, curing age importance and strength increment efficiency of using Empty Fruit Bunch of Oil Palm Fibre (EFBOPF) in structural concrete through a statistical model. The prediction was carried out using some concrete structural parameters (properties) through a one-way Analysis of Variance (ANOVA) model. These parameters include density, tensile and compressive strengths, and durability. The influences of EFBOPF on concrete density, compressive strength and durability were examined using 150 x 150 x 150 mm (for density and compressive strength) and 100 x 100 x 100 mm concrete cubes (for durability). Also, the strength performance of EFBOPF in concrete against tensile splitting and cracks was determined using 150 x 300 mm cylindrical concretes. The compressive strengths were evaluated at 28 days; tensile strengths at 28, 90 and 120 days; and durability performance was assessed at 28 and 90 days. All these parameters were tested using a Universal Testing Machine, weighing balance and durability testing apparatus. The results of the experiments were modelled with ANOVA. In the process of modelling, the correlations among the percentage of EFBOPF included, curing age, and the rate of concrete's strength increment were predicted. In accordance with ANOVA's prediction, the compressive strengths of concrete were greatly enhanced at 0.2 and 0.4% of EFBOPF. In addition, the split tensile strengths and durability capacity of EFBOPF-concrete were efficiently increased at 1.0% and 0.8-1.2% of EFBOPF inclusion, accordingly. The results of the modelling proved that EFBOPF increased the concrete strengths against compressive and tensile failures efficiently. Also, it was evident that EFBOPF enhanced the durability performance of concrete greatly. Although the application of EFBOPF in concrete as well as curing have great impacts on the hydration process of the concrete and its high strength yielding capacity. However, its capacity to increase the concrete's strengths does not depend on the rate of EFBOPF included or the long curing ages of concrete but depends on the reinforcement strength of EFBOPF used.
The ductility of reinforced concrete columns can be significantly influenced by the configurations and material properties of the confining bars. Extensive research is required to comprehend the limitations on yield strength imposed by certain building codes, particularly concerning high-strength reinforcement. AS 3600:2017 and ACI 318-19 codes restrict the yield strength of confinement reinforcement to 800 MPa and 700 MPa, respectively. This study investigates the ductility of reinforced concrete columns using five different confining bar configurations, two concrete compressive strengths (30 MPa and 50 MPa), two longitudinal reinforcement yield strengths (420 MPa and 500 MPa), and four transverse reinforcement yield strengths (420 MPa, 500 MPa, 700 MPa, and 1000 MPa). The diameter of the confining bars is adjusted to meet the required area estimates from ACI 318-19 and AS 3600:2017 codes. Additionally, finite element analysis is conducted using the 3D-NLFEA package. The results demonstrate the safety and adequate ductility provided by high-strength steel in reinforced concrete columns. Furthermore, a simple formulation for column ductility, which integrates the confining bar configurations, is proposed based on the numerical study.
May Accepted: ABSTRACT: A novel approach for assessing the structural health of cables in cable-stayed bridges, under varying load patterns, was presented. The method aimed to evaluate cable conditions by utilizing phase space analysis while minimizing traffic disruptions and reducing the necessity for extensive sensor deployment. Through comprehensive numerical investigations on the Manavgat cable-stayed bridge, the efficacy of the proposed method was demonstrated. For this purpose, the time-domain responses of the deck were utilized. The combination of Change in Phase Space Topology (CPST) and Mahalanobis Distance (MD) indices was applied to detect cable damage by discerning nuanced deviations in phase space trajectories. The results revealed that both the MD and CPST indices exhibited impressive accuracy in identifying damage severity and location. To emphasize the robustness of the phase space-based damage detection method, a comparative analysis between the CPST and modal parameters was conducted. At the 10% damage level, the accuracy of CPST increased by 84.5% compared to the first mode frequency of the structure in load state 1. It highlighted the high sensitivity of CPST in cable damage detection.
