Articles
Engineering Structures (18737323)340
This study presents an innovative approach for deconstructable external semi-rigid composite beam-to-column joints (DECJs) under cyclic loading featuring friction-grip bolted shear connectors, central reinforcing bars, and prefabricated geopolymer concrete slabs. The proposed design aimed to enhance deconstructability and sustainability by inserting central reinforcing threaded bars through column flanges, allowing for the disassembly of joint elements after their service life. Five full-scale external steel-concrete composite joints were designed and tested under cyclic loading to assess their seismic performance, focusing on failure modes, slip, moment-rotation responses, ductility, stiffness, energy dissipation, and strength degradation. The variables are the reinforcement ratio for central reinforcing bars, the diameter of bolted shear connectors, and the presence of steel fiber in geopolymer concrete (GPC) slabs. The experimental results showed that the use of bolt shear connectors, central threaded bars, and steel fiber-reinforced GPC slabs in DECJs significantly enhances the rotation capacity approximately 2–2.7 times higher than that provided by EC4. The proposed DECJ enhances the moment capacity and ductility of the joints, making them suitable for seismic applications. Moreover, it provides joint deconstructability, reduces the carbon footprint of the system, and effectively predicts the moment capacity of specimens, aligning with observed failure modes. Finally, a simple design model for estimating the moment capacity of the joints is proposed using the component-based modeling approach. © 2025 Elsevier Ltd
Journal of Constructional Steel Research (0143974X)235
This study offers a 3D finite element modeling (FEM) and parametric analysis of a novel extended endplate beam-to-column semi-rigid deconstructable external composite joint (DECJ) under cyclic loading. This innovative DECJ is created by connecting the precast geopolymer concrete slab to the top flange of a steel beam using bolted shear connectors, and inserting threaded central reinforcing bars into the column flanges to enhance the demountability of the entire system. The FEM was developed using ABAQUS software and verified against the experimental study results to analyze the structural behavior and failure modes of the proposed DECJ system. The study investigates the effect of various parameters, including the diameter of bolted shear connectors, the degree of shear connection, the ratio of central reinforcing bars, the thickness of the endplate, the thickness and strength of the geopolymer concrete slab, and the bolt diameters of the connection zone. The findings suggest that to prevent the failure of bolted shear connectors, the optimal shear connection degree of approximately 73 %–90 % and the concrete slab thickness of 80-120 mm should be maintained. Additionally, the central reinforcing bar ratio is preferred to be around 0.98 % to avoid the failure of shear connectors and reinforcing bars. Furthermore, the ratio of endplate thickness to connection zone bolt diameter should be between 0.64 and 0.82 to reduce the fracture risks of connection zone bolts. Finally, a new predictive equation is proposed to determine the plastic moment capacities of DECJs with precast concrete slabs, demountable bolted shear connectors, and demountable central reinforcing bars under cyclic loading. © 2024
Case Studies in Construction Materials (22145095)22
The significance of finding industrial waste solutions in the construction industry plays a crucial role in the quest for environmental conservation. To reduce the carbon footprint, this research has focused on developing solutions. This study assesses the mechanical properties of water-cured alkali-activated slag concrete (AASC) prepared using a one-part activator, where the dry alkali activator is pre-mixed with slag before water addition. The mix is then reinforced with three types of steel fibers, namely deformed steel fibers (DSF), recycled tire steel fiber (RTSF), and hybrid steel fiber (HSF) at varying volume fractions (0.5 %, 0.75 %, and 1.0 %). Numerous characteristics, including workability, compressive strength, flexural strength, splitting tensile strength, flexural toughness, and SEM observations in short-term, and stress-strain response under uniaxial compression, modulus of elasticity, peak strain and energy absorption in long-term were assessed. According to the test results, compressive strength was largely unaffected by fiber addition, with DSF at 1 % volume (DSF1) achieving the highest strength (58.51 MPa at 28 days). Conversely, optimal compressive strength for RTSF was observed at 0.5 % volume. On the other hand, the concrete mixes' splitting tensile, and flexural strengths increased with the addition of steel fibers achieving maximum values at 1 % DSF. The addition of steel fibers transformed the stress-strain response of one-part AASC mixes from brittle to ductile, with HSF specimens at 1 % volume (HSF1) exhibiting a 50 % increase in strain related to peak stress compared to the reference. Remarkably the HSF1 mix achieved a 421 % increase in toughness at 365 days compared to the reference mix. The DSF1 mix at 28 days and HSF1 at 365 days achieved the highest energy absorption capacity. Overall, the inclusion of 1 % DSF, RTSF, and HSF fibers enhanced the mechanical properties of one-part AASC, with DSF providing the most significant improvements at 28 days. © 2024 The Authors
