Interactions in a nonlocal isotropic thermoelastic solid with diffusion due to thermal source in frequency domain Belay Fikadu Gerba, Parveen Lata and Satya Bir Singh
Abstract; Full Text (1426K) .	pages 313-325.	DOI: 10.12989/csm.2025.14.4.313

Abstract
This study investigates the dynamic behaviour of nonlocal thermoelastic solid with diffusion subjected to thermal source, with a focus on the influence of angular frequency on the material. To examine this we consider nonlocal thermoelastic solid with diffusion. The governing equations are solved in the frequency domain to analyse the frequency-dependent response of the nonlocal thermoelastic solids with diffusion. Our findings are that angular frequency significantly effects the normal stress, shear stress, mass concentration and temperature change. The study highlights the importance of angular frequency in determining the stress, temperature and concentration fields in nonlocal thermoelastic diffusive solids under concentrated load. The results offer valuable insights for applications in advanced materials science, microscale and nanoscale engineering and dynamic load analysis, where it is crucial to understand the combined effects of nonlocality, thermoelasticity and diffusion.

Key Words
angular frequency; diffusion; Fourier transformation; nonlocal; stress; thermal; thermoelastic

Address
Belay Fikadu Gerba, Parveen Lata and Satya Bir Singh: Department of Mathematics, Punjabi University, Patiala, 147002, India

Analytical and numerical study of composite twin-girder bridge decks with adhesive connectors and composite reinforcement Benferhat Rabia, Hassaine Daouadji Tahar, Abbes Boussad, Bensatallah Tayeb, Rabahi Abderezak and Abbes Fazilay
Abstract; Full Text (2270K) .	pages 327-345.	DOI: 10.12989/csm.2025.14.4.327

Abstract
This study conducts both analytical and numerical investigations of composite twin-girder bridge decks. It combines numerical solution with analytical solutions to assess the structural behavior. Traditional steel shear connectors are replaced by adhesives, with a focus on the interfacial slip caused by this innovative assembly method. The study also evaluates the interfacial stresses in the steel girders, which are strengthened with composite materials to improve structural performance. The results demonstrate that a bracing system combining crossed diagonals and two parallel bars effectively reduces interfacial slip and stresses, thereby enhancing the stability and durability of composite twin-girder bridge decks.

Key Words
analytical and numerical investigations; bracing system; composite twin-girder bridges; interfacial slip; interfacial stresses

Address
Benferhat Rabia, Hassaine Daouadji Tahar, Bensatallah Tayeb, Rabahi Abderezak: Department of Civil Engineering, Ibn Khaldoun University of Tiaret, Algeria; Laboratory of Geomatics and Sustainable Development LGéo2D, University of Tiaret, Algeria
Abbes Boussad, Abbes Fazilay: Laboratory Materials and Mechanical Engineering MATIM, University of Reims Cedex 2, France

Column buckling under stochastic three-dimensional material properties: A stochastic finite element analysis Diem Dang Nguyen, Hien Duy Ta, Dan Sy Dao and Hung Duy Nguyen
Abstract; Full Text (2270K) .	pages 347-369.	DOI: 10.12989/csm.2025.14.4.347

Abstract
This study develops a Stochastic Finite Element Analysis approach integrating a numerical integration method and a perturbation method to analyze the buckling response of columns subjected to three-dimensional (3D) stochastic material variations. The proposed method discretizes the 3D random field of Young's modulus into fundamental random variables. The method is further enhanced with perturbation techniques, supporting the estimation of important statistical descriptors, including the expected value, coefficient of variation (COV), and standard deviation of the critical buckling load. The accuracy of the Stochastic Finite Element Analysis is validated via Monte Carlo simulations (MCs) implemented with the conventional Finite Element Method (FEM), while spectral expansion techniques are employed to create random instances for the 3D stochastic field model. The results demonstrate that for small spatial correlation lengths, local material fluctuations are effectively averaged due to stochastic homogenization, leading to lower variability in the critical buckling load. Conversely, an expansion of the correlation length results in heightened variability in the critical load, reflecting the impact of stochastic variability of material properties. Among the spatial directions, the characteristic correlation distance along the column's longitudinal axis has the most significant influence on the uncertainty of the critical buckling load, as axial stiffness directly governs the global stability of the structure. Furthermore, the study reveals an approximately linear correlation between the COV of the critical buckling load and that of the elastic modulus, suggesting that material randomness can serve as a predictor of structural stability variability.

Key Words
buckling; elasticity; finite element method (FEM); stability; stochastic analysis

Address
Diem Dang Nguyen, Hien Duy Ta, Dan Sy Dao: University of Transport and Communications, Ha Noi, Viet Nam
Hung Duy Nguyen: Helmut Schmidt University/University of the Federal Armed Forces Hamburg, Germany

open access
Unsteady gas dynamics modeling for leakage detection in parallel pipelines Ilgar G. Aliyev, Konul A. Gafarbayli, Ahad J. Mammadov and Mammadrzayeva Firangiz
Abstract; Full Text (1441K) .	pages 371-393.	DOI: 10.12989/csm.2025.14.4.371

Abstract
This study presents a novel analytical framework for modeling unsteady gas dynamics in parallel pipeline systems under leakage conditions. The proposed method introduces a time-dependent leakage mass flow rate function, G(t)=KxP1xe−Bt, which dynamically captures the temporal decay of leakage based on real-time inlet pressure measurements. This functional form allows for a more physically consistent and mathematically tractable representation of gas loss compared to conventional constant-rate or stepwise models. The pipeline system is partitioned into three regions relative to the leakage point, and closed-form pressure solutions are derived using Laplace transform techniques. These expressions enable direct estimation of the leakage location through inverse pressure profiles, eliminating the need for computationally intensive iterative schemes. The analytical model is further validated against representative benchmark scenarios, demonstrating good agreement with literature-based results. A comparative analysis underscores the model's ability to localize leakage using minimal sensor data while preserving interpret ability-an essential feature for deployment in industrial environments. The approach provides a lightweight yet robust alternative to purely numerical or machine learning-based solutions and offers potential integration into real-time monitoring systems. This work contributes to the field by unifying gas dynamic principles, sensor-assisted modeling, and analytical solution strategies to enhance the reliability and speed of leak detection in modern gas transport infrastructures.

Key Words
analytical modeling; Laplace transform; leakage detection; pressure function; real-time diagnostics; unsteady gas flow

Address
Ilgar G. Aliyev: Head of Operation and Reconstruction of Buildings and Facilities Department, Azerbaijan University Architecture and Construction, Baku, Azerbaijan
Konul A. Gafarbayli, Ahad J. Mammadov, Mammadrzayeva Firangiz: Department of Land Reclamation and Water Resources Construction, Azerbaijan University Architecture and Construction, Baku, Azerbaijan

Taking into account the inertia terms in lengthwise fracture analysis of moving bars Victor I. Rizov
Abstract; Full Text (1330K) .	pages 395-412.	DOI: 10.12989/csm.2025.14.4.395

Abstract
As known, when structural members and components perform motion with acceleration they are subjected to influence of inertia terms. These terms play an important role when assessing different aspects of the behavior of engineering structures. This paper treats the problem of the lengthwise fracture behavior of continuously inhomogeneous bars which move in horizontal direction and at the same time rotate around a longitudinal axis. Particular attention is paid to the problem of determining the inertia terms that act upon the bars. Since the bars under consideration are continuously inhomogeneous in both longitudinal and transversal directions, the mass per unit area change continuously along the length and thickness of the bars. The inertia terms also change continuously in the length and thickness directions. The bars have non-linear elastic behavior. The parameters of the non-linear constitutive law used in this paper change continuously along the bars length and thickness. The integral J is applied for analyzing the lengthwise fracture in the bars under the forces of inertia. The strain energy release rate (SERR) is derived for verification of the integral J. The effects of the parameters of the laws for motion of the bars on the lengthwise fracture are evaluated and reported in form of diagrams presenting the change of the integral J. Assessments of the influence of the change of the mass per unit area and the parameters of the constitutive law along the length and thickness of the bars on the lengthwise fracture are made too.

Key Words
acceleration; inertia terms; law of motion; lengthwise crack; material inhomogeneity; moving bar

Address
Victor I. Rizov: Department of Technical Mechanics, University of Architecture, Civil Engineering and Geodesy, 1 Chr. Smirnensky Blvd., 1046-Sofia, Bulgaria