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CONTENTS
Volume 36, Number 5, November 2025
 

Abstract
Lightly reinforced concrete walls with a single-layer of reinforcement have been frequently used as the lateral load-resisting system of industrialized and low-cost housing. The drift capacity of these walls is related to the tensile strain demand of the vertical rebars. The current approach for evaluation of this strain demand considers in-plane deformations only. Therefore, the effect of out-of-plane deformation and consequently the parameters controlling its development, such as the wall thickness, are not incorporated in the minimum reinforcement ratio requirements. This paper investigates the effect of out-of-plane deformation on the deformation capacity of thin, lightly reinforced structural walls. For this purpose, a numerical modeling approach, verified against existing experimental results, has been used to conduct parametric studies on the boundary zones with different dimensions and rebar ratios. The results show progression and recovery of significant out-of-plane deformation (before the development of out-of-plane instability) during in-plane loading of relatively thin walls and consequently a noticeable increase in strain demand of vertical bars, which would reduce the walls' deformation capacity. Also, the correlation between the rebar ratio and cross-sectional dimension of the boundary zone and anticipated rebar plastic strain is investigated, and importance of three-dimensional response assessment of slender shear walls with single-layer reinforcement is emphasized.

Key Words
out-of-plane deformation; singly reinforced; strain demand; structural walls

Address
Hamed Allahyari: BARSU Consulting Engineers, Urmia, Iran
Saeed Tariverdilo and Changiz Gheyratmand: Faculty of Engineering, Urmia University, Urmia, Iran
Farhad Dashti: ZURU Tech HK Ltd, Tsim Sha Tsui, Hong Kong

Abstract
Using an analytical approach based on the Galerkin method, a study on the static buckling behavior of functionally graded (FG) laminated shells reinforced with carbon nanotube (CNT) and carbon fibers is presented in this paper. The shapes considered are plate, cylindrical, spherical, elliptical-paraboloidal, and hyperbolic-paraboloidal shells. The variation of the volume fraction through the thickness of the shell is linear, while the percentage of CNT is distributed linearly over all layers of the shell in a constant manner according to four types of configuration: UD, FG-X, FG-O, and FG-V. The influences of various geometrical and material factors on the static buckling of shell structures were then examined using a parametric study.

Key Words
buckling; carbone nanotube, fiber reinforced composite; Galerkin approach; HSDT; shell structures

Address
Tayeb Kebir: 1) Artificial Intelligence Laboratory for Mechanical and Civil Structures and Solid, Department of Mechanical Engineering, University Centre of Naama, P.O. Box 66, Naama 45000, Algeria, 2) Laboratory of Materials and Reactive Systems, Faculty of Technology, University of Sidi Bel Abbes, Algeria
Fatima Zohra Kettaf: Department of Mechanical Engineering, University of Sciences and Technology Mohamed Boudiaf Oran, Algeria
Ahmed Amine Daikh and Thanh Cuong-Le: Center for Engineering Application & Technology Solutions, Ho Chi Minh City Open University, Ho Chi Minh City, Vietnam
Soumia Benguediab: Department of Civil Engineering and Hydraulic, University of Saida, Algeria
Amin Hamdi and Hani M. Ahmed: Department of Civil Engineering, Faculty of Engineering, King Abdulaziz University, Jeddah, Saudi Arabia
Abdelouahed Tounsi: 1) Center for Engineering Application & Technology Solutions, Ho Chi Minh City Open University, Ho Chi Minh City, Vietnam, 2) Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia, 3) Material and Hydrology Laboratory, Faculty of Technology, Department of Civil Engineering, University of Sidi Bel Abbes, Algeria
Mohamed Benguediab: Laboratory of Materials and Reactive Systems, Faculty of Technology, University of Sidi Bel Abbes, Algeria
Mohamed A. Eltaher: 1) Faculty of Engineering, Department of Mechanical Design and Production, Zagazig University, Zagazig, Egypt, 2) Faculty of Engineering, Department of Mechanical Engineering, King Abdulaziz University, Jeddah P.O. Box 80204, Saudi Arabia

Abstract
This study investigates the under-researched effects of initial geometric imperfections on blast-induced nonlinear transient responses in axially moving graphene platelet reinforced metal foam (GPLRMF) plates. The Halpin-Tsai model and mixing rules determine equivalent physical parameters for various GPL distribution patterns. Nonlinear governing equations are derived via Kirchhoff plate theory and discretized using Galerkin's method with simply supported boundaries. Model validation is performed against established literature. The fourth-order Runge-Kutta method solves the transient response numerically. Parametric analysis examines seven key factors: GPL distribution patterns, weight fraction, porosity distribution/coefficient, blast intensity, damping coefficient, and geometric imperfections. Results demonstrate that initial imperfections significantly influence the plate's dynamic behavior under blast loading.

Key Words
axial motion; blast pulse load; GPLRMF plate; initial geometric imperfection; nonlinear transient responses

Address
College of Mechanical and Vehicle Engineering, Chongqing University, Chongqing 400044, China

Abstract
Numerical modelling of gabion is challenging. Few studies analyzed and compared the fundamental mechanical properties between gabion and concrete. This paper employs discrete element methods (DEM) and introduces clusters to simulate the initiation and development of aggregate cracks. Basic element models for concrete and gabion are established, and numerical parameters are calibrated experimentally. Subsequently, this paper investigates the failure modes and mechanical properties of concrete and gabion under uniaxial compression loading. Results indicate that, for concrete, peak particle contact forces occur at the axial compression ratio (ACR) corresponding to its peak load, while force distribution in gabion is more dispersed. The force within concrete is one order of magnitude higher than that in gabion. The failure of concrete specimens involves both shear and tensile failure, with shear failure dominating initially and then transitioning to tensile failure (critical threshold is found at ACR=1.44%). In contrast, the failure of gabion is characterized by shear failure only. Furthermore, the energy required for gabion failure is significantly greater than that for concrete failure, indicating superior ductile behavior. This paper fills the research gap and serves as a reference for future numerical studies involving concrete and gabion structures.

Key Words
DEM; energy-absorption capacity; failure mode; force chain distribution; mechanical properties

Address
Gongning Liu, Huijian Zhang, Qiuyang Liu, Junling Si: School of Civil Engineering, Key Laboratory of Transportation Tunnel Engineering, Ministry of Education, Southwest Jiaotong University, No. 111, North Section, Second Ring Road, Jinniu District, Chengdu, Sichuan Province, 610031, China
Kai Liu: Department of Civil and Environmental Engineering, Louisiana State University, Baton Rouge, LA, USA
Hamed Gholizadeh Touchaei: Langan Engineering and Environmental Services, Inc., Parsippany, NJ, USA
Hossein Moayedi: 1) Institute of Research and Development, Duy Tan University, Da Nang, Vietnam, 2) School of Engineering & Technology, Duy Tan University, Da Nang, Vietnam

Abstract
Concrete is a fundamental material in civil engineering structures, known for its mechanical and behavioral characteristics, which often result in cracking post-construction. Understanding and predicting the fracture toughness of concrete is critical for ensuring the safety and durability of infrastructure, especially under dynamic loading conditions. In fracture mechanics, the stress intensity factor is compared with toughness rather than stress and strength, influenced by numerous geometric and physical parameters, and must be determined using experimental specimens. Compressive strength is a unique attribute of cementitious materials, universally applicable to all concrete structures and easily measured post-construction through coring tests. This study addresses the significant gap in dynamic toughness predictions based on stochastic calculations by proposing a novel modeling approach using meta-heuristic methods. The goal is to accurately estimate the fracture toughness of Ultra-High Performance Cementitious Composite (UHPCC) concrete from its compressive strength, thereby providing engineers with a reliable tool to enhance structural integrity. We collected extensive experimental data and conducted a comprehensive statistical analysis, employing 27 parameters to approximate the fracture toughness of UHPCC concrete using several advanced algorithms: genetic algorithm, artificial neural network, support vector machine, multivariate regression, gene expression algorithm, time series, and particle swarm optimization. Among these, the Gene expression programming algorithm (GEP) was identified as the most accurate model, yielding RMSE, MAE, VAF, MAPE, and R2 values of 0.41, 0.06, 98.88, 0.33, and 0.99, respectively. Furthermore, a multi-parameter sensitivity analysis based on GEP revealed that the unconfined compressive strength of the samples had the most significant impact on the dynamic toughness prediction model, with a sensitivity analysis rate of 333. This approach not only enhances the predictive accuracy but also contributes to the advancement of resilient and durable infrastructure. These findings offer a rapid and reliable method for predicting the fracture toughness of UHPCC concrete, providing a valuable tool for structural engineers to design and assess concrete structures under dynamic loading conditions.

Key Words
dynamic toughness; fracture mechanics; mechanical properties; meta-heuristic algorithms; UHPCC concrete

Address
Department of Mining Engineering, Faculty of Engineering, University of Kashan, Kashan, Iran

Abstract
In recent years, the utilization of structural members made of concrete-filled steel tube (CFST) sections has increased due to their positive effect on the system's performance. In addition, there is a need to find sustainable and environmentally friendly materials that make a successful step toward saving environmental resources and reducing pollution. In this study, the two approaches were combined by the utilization of recycled aggregates forming what is known as geopolymer recycled aggregate (GRA) CFST columns. A novel definition of the confinement level was proposed for CFST square columns with a new relationship between the residual load coefficient and the confinement level. The nonlinear finite element analysis (NLFEA) method was used to examine the behavior of GRACFST columns. The investigated parameters include the following: (i) recycled aggregate replacement ratio (R%) as 0, 50, and 100, (ii) infill concrete strength (30, 45, and 65 MPa), and (iii) width-to-thickness ratio (B/t) as (52.0, 32.0, 23.4, and 18.7). It was found that increasing the (R%) maximized the benefit of increasing the steel tube thickness for high-strength concrete compared to reversed behavior for normal-strength geopolymer concrete. In addition, the proposed levels definition and the introduced relationship between the confinement level and the ratio between the residual and the ultimate load capacities were real and accurate as evidenced by the validation against literature with +-10% error.

Key Words
CFST columns; confinement; GRA; residual load coefficient; sustainability

Address
Department of Civil Engineering, Faculty of Engineering, Jordan University of Science and Technology, PO Box 3030, Irbid 22110, Jordan

Abstract
Existing reinforced concrete (RC) structures are subjected to continuous deterioration and changes in their use, along with being exposed to various environmental conditions. Generally, RC structures could be subjected to high temperatures where their material is exposed to significant deterioration that affects their structural performance, and the need for strengthening is increased. Four strengthening configurations are introduced in this study to substitute for the resulting loss in the slab's mechanical characteristics due to the high temperatures and opening creation within the slab surfaces. A total of twenty-five RC slabs were simulated with (1100x500x120) mm3 dimensions. Square openings were created within the RC slabs with three values (100, 150, and 200) mm corresponding to opening ratios of (2.0, 4.5, and 8.0)%, respectively, subjected to four temperature values (23, 200, 400, and 600) oC. One specimen was left without heat damage or strengthening, twelve were heat-damaged at different temperatures, and the remaining twelve were strengthened using carbon fiber-reinforced polymers (CFRP). Slabs were simulated using the nonlinear finite element analysis (NLFEA) with four four-point loading procedures. Results showed that openings have a negative effect on the behavior of the RC slabs, with a significant enhancement recorded by the CFRP strengthening method.

Key Words
CFRP sheets; elevated temperatures; flexural behavior; NLFEA; sectional analysis; slab opening

Address
Department of Civil Engineering, Faculty of Engineering, Jordan University of Science and Technology, PO Box 3030, Irbid 22110, Jordan

Abstract
To determine the effect of carbon nanotube (CNT) on cement hydration, this study defines the hydration mechanism of CNT-cement composites and presents a model, in the form of a simple equation, for predicting the initial and long-term compressive strengths of the CNT-cement composites. The hydration acceleration effect of CNTs is modeled by extending the CEMHYD 3D model to the nanoscale. This approach provides a method for modeling the initial microstructure that can be applied during the cement hydration process. The impact of CNTs on cement hydration reactions is analyzed numerically using the proposed method for microstructure formation. The numerical analysis results are applied to the simple model for predicting compressive strength based on hydration, and the hydration acceleration effect of CNTs is approximately 10%. The hydration analysis model for predicting compressive strength is based on the Parrot and Killoh model. Reflecting the hydration acceleration effect of CNTs, the model is configured to predict initial and long-term compressive strengths because of increased hydration levels. The proposed model reflects the hydration acceleration effect of CNTs, enables compressive strength prediction, and has high accuracy. Model validation is demonstrated by comparing experimental results of CNT-blended mixtures. The experimental results comprised comparisons of the compressive strength values of CNT-blended mixtures from 1-day to 1-year of age. The CNT-cement composite hydration analysis model demonstrates high accuracy in its predictions. Especially, long-term strength can be forecasted with an error margin of just 3%.

Key Words
cement hydration; CNT-cement composites; CNT; compressive strength; long-term strength; prediction model

Address
KICT (Korea Institute of Civil Engineering and Building Technology), Goyang-si 10223, Republic of Korea

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