Abstract
This study presents and studies the application of normalized Modified Bouc-Wen model to capture the nonlinear hysteretic behavior of viscoelastic dampers under cyclic loading. Six different tests were conducted on viscoelastic dampers with different frequencies and amplitudes to evaluate their energy dissipation performance. The model considers strength and stiffness degradation effects using a normalized form to capture nonlinear hysteretic behavior based on applied loading and energy dissipation. Since identifying Modified Bouc-Wen parameters from the experimental results is a challenging task due to the complexity and interdependence of the parameters in the model formulation, the Particle Swarm Optimization (PSO) algorithm was applied. The first stage involved exploring a wide range of parameter values to identify reasonable value ranges, and the second stage applied refined bounds to improve accuracy. The calibrated model was validated by comparing its results with experimental hysteresis curves, confirming good agreement in both stress-strain response and energy dissipation. Furthermore, various machine learning regression models were trained using measurable input parameters. The output variables were the remaining Modified Bouc-Wen parameters derived from PSO-based optimization. Among the tested machine learning models, Gradient Boosting achieved the best performance, effectively estimating the Bouc-Wen parameters and reliably predicting the overall hysteretic behavior. SHAP analysis was conducted to interpret the model, indicating that stiffness and amplitude were the most influential features in estimating the Modified Bouc–Wen parameters.
Address
Seungho Chun: Department of Global Smart City, Sungkyunkwan University, Suwon, Republic of Korea
Mohammad Mahdi Javidan: Global Frontiers of Resilient EcoSmart City, Sungkyunkwan University, Suwon, Republic of Korea
Yang Xiang: School of Civil Engineering, Tongji University, Shanghai, China
Jinkoo Kim: Department of Global Smart City, Sungkyunkwan University, Suwon, Republic of Korea
Abstract
Structural design requires reliable life evaluation. This study employs an approach based on the second law of thermodynamics and entropy generation to assess damage and predict the lifespan of metallic workpieces under uniaxial creep loading. The Norton method was used to calculate initial creep strain rates, followed by determining entropy generation rates and cumulative entropy to quantify damage. The results aligned well with experimental data, demonstrating that entropy generation at the end of the secondary creep stage is stress- and temperature-independent and can be considered a material characteristic. The entropy growth rate increased significantly upon entering the tertiary creep region, mirroring the creep strain rate trend. Stress and temperature influenced entropy generation and damage, with higher stress or temperature accelerating damage propagation. Normalized entropy diagrams were developed and matched with normalized lifetimes across various stress and temperature conditions, revealing material-specific, stress- and temperature-independent correlations. These findings highlight the applicability of entropy-based models for reliable creep life prediction in metals.
Key Words
creep; damage; entropy generation method; finite element model; uniaxial loading
Address
Mostafa Jalalizadeh: Department of Mechanical Engineering, Iran University of Science & Technology, Iran
Hadi Khoramishad: Adhesively Bonded and Sandwich Structures Research Laboratory, School of Mechanical Engineering,
Iran University of Science and Technology, Narmak, 16846-13114, Tehran, Iran
Abstract
This paper presents a unified quasi-C1-PIM formulation for high-fidelity static and dynamic analysis of beams and plates with arbitrary cross-sections. The formulation integrates a novel eight-node quadrilateral element that achieves quasi-C1 continuity through an averaged dual-path interpolation scheme, enabling smooth stress fields without post-processing. Discretizing the cross-section with a quadrilateral mesh and constructing the threedimensional (3D) displacement field reduces the original problem to a one-dimensional (1D) formulation along the structural axis. An adaptive meshfree point interpolation method (PIM) with a tunable support-domain parameter n0 is employed as the axial solver, facilitating efficient p-convergence. The proposed method is systematically validated through a series of benchmark problems, including a rocket thrust frame, an L-shaped plate on an elastic foundation, thin-walled beams, composite beams, and frame structures under static and dynamic loading. The results exhibit excellent agreement with high-fidelity 3D finite element models while reducing the system degrees of freedom by 85-95% and achieving up to 3.7x speedup and 61% memory reduction at comparable accuracy levels. Parametric studies confirm stable convergence with respect to cross-sectional mesh refinement, axial node density, and the support-domain parameter. By combining geometric generality, inherent stress smoothness, and computational efficiency, the quasi-C1-PIM framework provides a unified and reliable 1D numerical approach for analyzing complex beam and plate structures.
Key Words
arbitrary cross-section beams; dimensional reduction; point interpolation method; quasi-C1 continuity; smooth stress analysis; unified beam-plate formulation
Address
Guanghui He: School of Intelligent Construction, Shanghai Technology and Innovation Vocational College, 925 North Renmin Road, Shanghai, 201620, China; Shanghai Songjiang Industry-Education Integration Research Center, Shanghai Open University, 288 Guoshun Road, Shanghai, 200433, China; Central Research Institute of Shanghai Construction Group, Shanghai Construction Group, 700 Xinjunhuan Road, Shanghai, 201114, China
Xiaowei Li: School of Intelligent Construction, Shanghai Technology and Innovation Vocational College, 925 North Renmin Road, Shanghai, 201620, China; Shanghai Songjiang Industry-Education Integration Research Center, Shanghai Open University, 288 Guoshun Road, Shanghai, 200433, China
Xinkui Li: Central Research Institute of Shanghai Construction Group, Shanghai Construction Group, 700 Xinjunhuan Road, Shanghai, 201114, China
Abstract
The rapid development of high-speed railways has promoted the widespread use of dual-use long-span cable-stayed bridges for crossing large rivers and valleys. However, the complex loading conditions associated with these structures introduce significant uncertainties in track geometry evolution, posing challenges for reliability assessment and potentially affecting the safety and performance of railway operations. To address these challenges, this study establishes an integrated finite element model of a dual-use long-span cable-stayed bridge with ballastless track. The model is used to simulate the evolution of track geometry under different loading conditions, showing that long-wave vertical track irregularities exhibit multiple peaks, with the maximum deviations generally occurring near the bridge towers. A reliability assessment framework based on point estimation and higher-order moment theories is proposed to quantitatively assess the reliability of track geometry under the combined effects of highway loads, train loads, and temperature variations. The findings provide a systematic understanding of track geometry behavior on dual-use cable-stayed bridges and offer a robust methodological basis for ensuring the safety, reliability, and operational efficiency of high-speed railway systems on complex bridge structures.
Address
Xunyi Yin: State Key Laboratory of Safety, Durability and Healthy Operation of Long Span Bridges, Nanjing, Jiangsu, 211189, China; School of Civil Engineering, Central South University, Changsha, Hunan, 410075, China; Department of Geotechnical Engineering, Tongji University, Shanghai, 200092, China
Weiqi Zheng: State Key Laboratory of Safety, Durability and Healthy Operation of Long Span Bridges, Nanjing, Jiangsu, 211189, China; School of Civil Engineering, Central South University, Changsha, Hunan, 410075, China
Chao Lin: School of Civil Engineering, Central South University, Changsha, Hunan, 410075, China
Yonghong Yang: School of Civil Engineering, Central South University, Changsha, Hunan, 410075, China; Shanghai-Hangzhou Railway Passenger Dedicated Line Co. Ltd., Shanghai, 200030, China; Shanghai State Railway Engineering Construction Management Co. Ltd., Shanghai, 200030, China
Xingwang Sheng: School of Civil Engineering, Central South University, Changsha, Hunan, 410075, China
Abstract
This study evaluates the performance of GPC modified with NiTi Shape Memory Alloy (SMA) fibers and waste rubber crumb (WRC) at elevated temperatures. For this purpose, in addition to the unreinforced concrete, mix designs with 0.25% and 0.5% of SMA and 10% WRC were designed and subjected to different tests at ambient temperature, 150oC, 400oC, 600oC and 900oC. It was concluded that at ambient temperature, SMA increases the compressive strength by 10.7%, while WRC reduces it by 27%. Moreover, at 150oC, SMA0.5 exceeded its ambient strength by 2.8%, while the other specimens experienced a decrease in strength. Then, with increasing temperature, all samples experienced a decrease in compressive strength. In addition, splitting tensile strength of the fiber specimens at ambient temperature increased up to 36%, but at 400oC decreased by about 20%, while this decrease was 48% in GPC, and the WRC experienced a decrease of about 21% at 400oC. Furthermore, the flexural strength increased by 7% with the addition of SMA, but WRC caused a 13% decrease in strength. Overall, SMA provides effective crack bridging and thermal damage reduction at all temperatures, while WRC compromises strength.
Address
Muhammed Maleknia, Morteza Jamshidi, Morteza Biklaryan: Department of Civil Engineering, Cha.c., Islamic Azad University, Chalus, Iran
Rahmat Madandoust: Department of Civil Engineering, University of Guilan, Rasht, Iran
Abstract
This paper investigates the nonlinear low-velocity impact response of an axially moving functionally graded (FG) conical shell. The nonlinear equations of motion are derived based on Reddy's shell theory and von Kármán geometric nonlinearity. With simply supported boundary conditions, the time histories of deformation and contact force are solved numerically by combining the fourth-order Runge‑Kutta method with the Galerkin technique, and the impact force is determined using the modified Hertzian contact model and Newton's second law. A key finding regarding the optimal volume fraction is that an intermediate ceramic content minimizes the central deflection under low-velocity impact, indicating a trade-off between stiffness and energy absorption. Additional numerical results reveal several key findings: (1) Increasing the prestress reduces the maximum central deflection while having negligible effect on the peak contact force, indicating an enhanced energy dissipation capability. (2) A larger damping coefficient accelerates the return to equilibrium after impact but only slightly decreases the maximum deflection. (3) Raising either the impactor radius or its initial velocity increases the peak deflection and contact force; however, a larger radius prolongs the contact time, whereas a higher initial velocity shortens it. (4) The axial motion speed of the conical shell affects the deflection more significantly than the contact force, suggesting that contact stiffness remains nearly unchanged. (5) The semi-vertex angle of the conical shell has a weak influence on the impact response. (6) Increasing porosity or the functionally graded index (i.e., reducing ceramic content) reduces structural stiffness, leading to larger contact displacements.
