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Chatzikonstantinou, Nikoleta; Makarios, Triantafyllos
doi: 10.1002/tal.70131pmid: N/A
The present paper deals with the analytical and numerical solution of the motion equation of a single degree of freedom (SDoF) oscillator with damping and negative stiffness (NS) due to seismic excitation at its base. The resulting solution shows that the structure's response displacement increases exponentially; thus, practically, there is no vibration. Moreover, a well‐known numerical procedure is selected to be modified in order to be suitable for the calculation of the response of the abovementioned NS‐SDoF oscillator. Specifically, an appropriate modification of the central difference method is presented, taking into account the damping and NS of the oscillator. The effectiveness of this proposed procedure is examined by comparing the extracted results to those obtained through the exact mathematical solution. The accuracy and precision of the proposed modified numerical method are investigated through numerical examples by comparing the results obtained with the analytical process. The results show that the new modified numerical method, as well as the analytical one, led to similar results; thus, the modified central difference method can be efficiently and safely used for the calculation of the response of NS‐SDoF systems.
doi: 10.1002/tal.70087pmid: N/A
Two additional deformation mechanisms—local shear and axial extensibility of the walls—have recently been incorporated into the analysis of coupled shear walls to overcome the lack of accuracy of classical continuous models. Although several generalized continuous models and solution techniques have been proposed, they usually entail high computational costs and require advanced user expertise. In this paper, a three‐field CTB beam—constructed from the parallel coupling of an extensible Timoshenko beam and a shear beam—is employed to derive, for the first time, simple and directly applicable analytical expressions for estimating the fundamental frequency and the global critical buckling load of uniform one‐bay coupled shear walls, both symmetric and asymmetric. Using a subsystem‐based approach, the static lateral displacement is decomposed into three independent subsystems: a bending–shear beam, a bending beam, and a shear beam. Approximate eigenvalue expressions are derived for each subsystem with sufficient accuracy, enabling direct evaluation of their natural frequencies and critical loads. These eigenvalues are then combined through Dunkerley's principle to obtain conservative global estimates of the generalized three‐field CTB beam response. To improve predictive accuracy, correction factors are introduced for both dynamic and stability analyses, keeping the estimates within acceptable engineering tolerances. A thorough parametric study encompassing a wide range of structural behaviors confirms the suitability of the proposed analytical solutions for practical applications. Maximum deviations remain within ±3.87% for the dynamic case and ±5.33% for the buckling case, providing a reliable and low‐complexity alternative for preliminary structural design.
Dar, Mohammad Adil; Baba, Suhail Ahmad; Zakir, Mohammad; Dar, A. R.
doi: 10.1002/tal.70130pmid: N/A
Cold‐formed steel (CFS) beams are made by cold‐working steel sheets or strips to produce precise profiles and dimensions, and they are well‐known for their material efficiency, cost‐effectiveness, and versatility in modern engineered structures, such as modular and prefabricated systems. CFS sections are often used in the construction of industrial facilities, residential buildings, and low‐ to mid‐rise commercial structures due to their high strength‐to‐weight ratio, which allows for minimal material utilization while maintaining structural performance and resilience. Despite these benefits, multiple buckling modes govern the structural behavior of CFS components. Therefore, limiting such buckling deformations in thin‐walled sections is critical for achieving superior efficiency and adaptability in construction practice. This work discusses a test program designed to restrict local buckling deformations in CFS built‐up I‐sections with rectangular compression flanges using a variety of sustainable lightweight fillers. For the first time, bamboo poles, repurposed steel tubes, and timber blocks were utilized as lightweight fillers to prevent local buckling in the compression zone. These fillers were chosen with sustainability in consideration, as all three are either renewable, repurposed, or have a reduced environmental footprint, making them ideal for eco‐friendly and adaptable construction applications. The performance output in the form of peak load, type and magnitude of buckling failure, stiffness, moment capacity, capacity‐to‐weight ratio, and test moment‐to‐yield/plastic moment ratios were evaluated to determine the effectiveness of the various composite stiffening techniques used. Further, the theoretical strengths were also quantified and compared with the test strengths. The test findings suggested that all of the sustainable composite stiffening techniques successfully enhanced the flexural performance of CFS built‐up beams with rectangular compression flanges, although to varying degrees. These findings contribute to expanding the limited dataset available on such lightweight built‐up beams and highlight their potential for construction efficiency, adaptability to evolving functional needs, and long‐term sustainability in modern structural systems.
doi: 10.1002/tal.70133pmid: N/A
The structural utilization of waste sintered bricks is currently restricted by the inherent defects of recycled brick aggregates, such as low strength and high variability. To address this issue, this study proposes a novel mixed recycled concrete‐filled double‐skin steel tube (MRCFDST) column with a square‐in‐square section, which utilizes a dual‐confinement mechanism to enhance the performance of brick‐aggregate concrete. A comprehensive investigation involving axial and eccentric compression tests on six specimens, along with finite element analysis (FEA), was conducted to evaluate the effects of the recycled aggregate replacement rate (r), load eccentricity (e), and sectional form. Experimental results indicate that the dual confinement effectively mitigates the brittleness of brick aggregates, ensuring a ductile failure mode dominated by the local buckling of steel tubes even at a 100% replacement rate. While the ultimate bearing capacity decreased by 14.1% and 34.2% as r increased from 0% to 100% and e increased from 0 to 40 mm, respectively, the hollow sandwich configuration exhibited an 11.2% higher bearing capacity compared to the solid section equivalent. Furthermore, a validated FEA model was developed, achieving high prediction accuracy with an average experimental‐to‐calculated ratio of 0.978. Based on the parametric analysis, a practical calculation method for the bearing capacity of MRCFDST accounts for the confinement factor is proposed. This study demonstrates that the proposed double‐skin configuration effectively “upgrades” low‐quality recycled materials for load‐bearing structural applications.
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