In the context of green building and sustainable urban development, understanding the mechanical behavior of structural components like concrete-filled steel tube (CFST) columns is crucial due to their improved load-bearing capacity, energy efficiency, and optimized material usage, which enhance structural resilience and sustainability. This research addresses the complex development of confining stress and its impact on the concrete core (CC) behavior within these columns, which are essential for urban infrastructure. Through extensive numerical studies, this study proposes a model to estimate the confining stress in axially loaded CFST short columns. Study findings reveal that the confinement effectiveness is influenced by variables such as compressive strength (CS) of the concrete, cross-sectional shape, and depth-to-wall thickness percentage. Additionally, the confinement is also significantly affected by the yield strain of steel ε_y/ε_c to the peak strain of unconfined concrete ε_c. A three-dimensional finite element model (FEM) was built for the simulation of the columns’ nonlinear behavior and was rigorously validated against experimental data. This model aids in the design and implementation of more efficient and resilient urban structures, supporting the principles of sustainable construction. The study underscores the importance of structural integrity in sustainable urban development and provides valuable insights for improving the design of green building materials.

In this article, wave propagation of the sandwich composite beam with tunable electro-rheological (ER) fluid core is investigated. The sandwich composite beam is made of three layers consisting of the basic layer, ER fluid core, and the limiter layer. ER fluid core embedded withindoors the basic and limiter layers. The upper and lower layers are constructed of the elastic materials. Hamilton’s principle is utilized for deriving the governing equations of motion. Using an analytical solution, the wave frequency and the phase velocity can be gathered by solving eigenvalue problem. Moreover, the effect of different parameters such as electric field, core-to-top layer thickness ratio, and thickness of ER core is investigated on the wave dispersion characteristics.

The present research explores the behavioral characteristics of concrete produced with recycled carpet fibers and micro-silica additives, examined under both room temperature (25 °C) and high-temperature conditions (200 °C and 600 °C). Carpet fibers were incorporated into the mixtures at volume ratios of 0.5%, 0.75%, and 1%, and experimental investigations were carried out to determine the compressive strength, tensile resistance, and elastic modulus of the re-sulting composites. Unlike previous studies that examined fibers or micro-silica separately and primarily under ambient conditions, this work is original in combining recycled carpet fibers with micro-silica and assessing their synergistic effects under elevated temperatures (200 °C and 600 °C) through laboratory-scale testing of cubes, cylinders, and beams. The study highlights the combined use of recycled carpet fibers and micro-silica to enhance mechanical strength while preserving performance under thermal exposure, an aspect overlooked in earlier research. This dual focus enhances understanding of both mechanical behavior and sustainability, offering practical guidelines for structural applications. The results show that incorporating 0.5% carpet fibers with 10% micro-silica achieved the highest performance, improving CS by 21% compared with the reference mix. Higher fiber contents (0.75% and 1%) reduced performance due to poor fiber dispersion and bonding. At elevated temperatures, both compressive and tensile strength decreased, with the tensile strength exhibiting a more pronounced reduction due to fiber degradation. Furthermore, using 0.5% recycled carpet fibers promotes sustainability by diverting non-biodegradable waste from landfills and reducing the need for virgin materials, thereby lowering the environmental footprint of concrete production.