Within the framework of sustainable development in the construction sector, the valorization of industrial waste in concrete formulation has emerged as a strategic approach to reducing production costs while minimizing environmental impact. This research presents a comparative study investigating the effects of waste plastic fibers derived from recycled PET strapping and steel fibers recovered from tire waste on the properties of high-performance concrete. To achieve this objective, the physical, mechanical, and durability properties of high-performance concrete mixtures incorporating 0.5% and 1% of recycled strapping fibers and recycled steel fibers were examined and compared with those of high-performance concrete containing conventional steel fibers. The experimental results revealed that the incorporation of recycled steel fibers progressively decreased the workability of high-performance concrete, whereas recycled strapping fibers enhanced it. Moreover, fiber-reinforced high-performance concrete exhibited higher compressive and flexural strengths, particularly when conventional steel fibers and recycled steel fibers were used, while recycled strapping fibers had an insignificant effect on flexural strength. Specifically, the compressive strength increased by 22.40%, 21.85%, and 7.63% for high-performance concrete incorporating steel fibers, recycled steel fibers, and recycled strapping fibers, respectively. The findings also indicated that recycled fiber incorporation reduced drying shrinkage of high-performance concrete. However, the resistance to acid attacks was reduced.
Electrode selection and deposition sequence can affect the mechanical, microstructural, and corrosion characteristics of shielded metal arc welding (SMAW) joints. This study investigated four E6013/E7016 root-cap combinations, namely E6013-E6013, E6013-E7016, E7016-E6013, and E7016-E7016, for welding 8 mm SS400 steel using a two-pass single-V-groove joint. The welded joints were evaluated by liquid penetrant testing, tensile testing, Vickers microhardness, optical microscopy with ImageJ-based phase estimation, and potentiodynamic polarization in 3.5 wt. % NaCl solution. No clear surface-breaking cracks were detected. E6013-E6013 produced the highest ultimate tensile strength of 464.37 ± 0.87 MPa, whereas E7016-E7016 exhibited the highest yield strength of 331.47 ± 18.09 MPa. The highest weld-metal hardness was obtained with E7016-E6013 at approximately 205.80 HV0.3. All conditions exhibited ferrite-dominant microstructures, with E7016-E7016 showing the highest weld-metal ferrite fraction of 76.14 ± 4.47%. E7016-E7016 also provided the highest corrosion resistance, with the lowest corrosion rate of 0.00550 mm/year. Overall, E6013-E6013 provided a favourable balance of tensile strength, hardness uniformity, microstructural consistency, and corrosion resistance, while E7016-E7016 exhibited superior corrosion resistance.
This study investigates the fire performance of uniform and graded thin-walled square steel columns under Hydrocarbon fire conditions. A sequentially coupled FE model in ABAQUS is employed to assess the effect of wall thickness (9 mm and 13 mm), thickness grading, longitudinal stiffeners, and diaphragm systems under a constant axial load ratio of 10% of squash load. A total of 28 configurations is analysed for both thicknesses, including uniform and graded square sections with and without internal reinforcement (i.e., stiffeners and/or Diaphragms). Structural performance is evaluated using developed compressive axial force, buckling time resistance (BTR) and failure time resistance (FTR). The results reveal that increasing wall thickness significantly improves fire performance, with normalized improvements of up to 135%, 56%, and 88% in compressive axial force, BTR, and FTR, respectively. Moreover, thickness grading consistently enhances both BTR and FTR, with clear advantages observed at higher thickness. Longitudinal stiffeners are identified as the most effective strengthening technique, while the benefits of grading within stiffeners diminishes as thickness increases. In contrast, diaphragms contribute insignificantly to structural performance. These findings indicate that fire response of thin-walled square steel columns is governed by local plate buckling, and stiffeners are being effective than diaphragms reinforcement.
This study examines the effect of preheating temperature (N/A, 150 °C, 250 °C, and 350 °C) on the mechanical performance and microstructural evolution of SMAW-welded ASTM A36 steel. Welding was performed under controlled conditions using E7016 and E7018 electrodes, and joint properties were evaluated through tensile testing, Vickers hardness profiling, and metallographic analysis in the WM, HAZ, and BM regions. The ultimate tensile strength remained relatively stable (443-446 MPa), whereas yield strength and ductility varied with preheating temperature. The 250 °C condition yielded the highest yield strength (315.68 MPa) and the most uniform hardness distribution, indicating moderated cooling behaviour. Microstructural analysis revealed a refinement-stabilisation-coarsening trend with increasing preheat, with 250 °C producing the most homogeneous ferrite-pearlite structure, while 350 °C promoted grain coarsening and softening.
This paper presents a modified initial parameter method for deterministic interval estimation of critical loads in axially compressed variable-stiffness rods. In the present study, the term "interval" refers to the range bounded by lower and upper estimates obtained from inscribed and circumscribed piecewise-constant geometric approximations of continuously varying cross-sections. The method approximates continuously varying cross-sections by inscribed and circumscribed piecewise-constant segments, providing reliable upper and lower bounds without requiring closed-form solutions. The formulation is applicable to both conservative and follower-load problems under various boundary conditions. Numerical examples for conical and smoothly varying rods demonstrate monotonic convergence of the estimates, with relative deviations below 1-3% for refined discretization. The proposed framework provides a computational tool for stability analysis of structural elements with variable stiffness and establishes rigorous deterministic lower and upper bounds that may serve as a baseline for subsequent uncertainty or reliability analyses. The present study is restricted to linear elastic rod theory; extension to elastoplastic behaviour is considered as a possible direction for future research.
