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CONTENTS
Volume 35, Number 1, January 2025
 

Abstract
In order to analyze the bending behavior of functionally graded carbon nanotubes (CNT)/fiber-reinforced composite laminated shells, an analytical solution based on the Galerkin technique is proposed. The mathematical formulations are generated based on higher-order shear deformation theory. Various geometrical schemes of shells are analyzed. Three distribution patterns of fibers are examined, FG-X, FG-O and FG-V, in addition to the uniform distribution (UD). The CNTs volume fraction is constant and evenly distributed throughout all shell layers. The virtual work principle is employed to derive the equilibrium equations. The influence of CNTs and fibers proportion, fibers distribution patterns, geometrical parameters and various boundary conditions on the deflection of CNTs/F-RC shells is investigated in detail.

Key Words
bending; CNTs/Fiber reinforced composite; Galerkin method; higher-order shear deformation theory; shells

Address
Ahmed Amine Daikh: 1) Artificial Intelligence Laboratory for Mechanical and Civil Structures, and Soil, University Center of Naama, P.O. Box 66, Naama 45000, Algeria, 2) Laboratoire d'Etude des Structures et de Mécanique des Matériaux, Département de Génie Civil, Faculté des Sciences et de la Technologie, Université Mustapha Stambouli B.P. 305, R.P.29000 Mascara, Algérie
Mohamed A. Eltaher: 1) Department of Mechanical Design & Production, Faculty of Engineering, Zagazig University, P.O. Box 44519, Zagazig, Egypt, 2) Department of Mechanical Engineering, Faculty of Engineering, King Abdulaziz University, P.O. Box 80204, Jeddah, Saudi Arabia

Abstract
Over the past few years, there has been an increasing emphasis on assessing structures in harsh environments to guarantee their safety and longevity. Nevertheless, precisely modeling the behavior of corroded elements and estimating their capability is still a major hurdle. Current models often depend on oversimplified assumptions, such as the uniform distribution of corrosion in steel bars, which can result in inaccurate forecasts of structural behavior. Through numerical and experimental studies, this research attempts to integrate recent findings on the corrosion distribution of steel bars with structural element modeling by introducing a modified beam-column element in OpenSees. For this purpose, different stochastic distributions of corrosion associated with steel bar area reduction were incorporated into the element by modified fiber modeling formulation. This study also considered the impact of transverse bars on element modeling, which further increased the results' accuracy. The accuracy of the proposed element was evaluated by comparing the modeling results with laboratory observations. The results indicated that the proposed element with suggested area reduction models considerably increases the modeling accuracy compared to the existing techniques based on even corrosion distribution.

Key Words
corroded RC members; failure probability; fiber beam-column element; OpenSees; probability distribution

Address
Behrouz Akbarian Reshvanlou: Structural Engineering Division, Department of Civil Engineering, University of Zanjan, Zanjan, Iran
Kiarash Nasserasadi and Jamal Ahmadi: Structural Health Monitoring Research Lab, Department of Civil Engineering, Faculty of Engineering, University of Zanjan, Zanjan, Iran

Abstract
This research paper deals with the analysis of buckling and free vibration of cross-ply laminated composite plates on elastic foundations. A refined plate theory based on the undetermined integrals terms is presented, which leads to reducing the unknown number to four instead of five or more unknowns used in the other theories. In the current theory, a function of shear with a hyperbolic form is employed, so the parabolic transverse shear stresses variation through the plate's thickness is obtained, and the zero shear stress conditions at the plate's top and bottom surfaces are satisfied. Therefore, the present formulation does not need shear correction factors. Pasternak elastic foundation mathematical model is considered in the formulation. The motion equations are determined using the virtual work principle, and the Navier approach is utilized to obtain the closed form solutions of cross-ply laminated plates. The fundamental frequencies and buckling loads are predicted by determining the eigenvalue problem. The present results are discussed and validated with results predicted using other previously published models.

Key Words
buckling; cross-ply laminated plates; elastic foundation; free vibration

Address
Nasrine Belbachir: 1) Civil Engineering Department, Faculty of Sciences and Technology, Abdelhamid Ibn Badis University, Mostaganem, Algeria, 2) Material and Hydrology Laboratory, Engineering Department, Faculty of Technology, Civil University of SidiBel Abbes, Algeria
Abdelouahed Tounsi: 1) Material and Hydrology Laboratory, Engineering Department, Faculty of Technology, Civil University of SidiBel Abbes, Algeria, 2) YFL (Yonsei Frontier Lab), Yonsei University, Seoul, Korea, 3) Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia
Mohammed A. Al-Osta: 1) Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals,
31261 Dhahran, Eastern Province, Saudi Arabia, 2) Interdisciplinary Research Center for Construction and Building Materials, KFUPM, 31261 Dhahran, Saudi Arabia

Abstract
This study focuses on enhancing concrete's mechanical strength and reducing its environmental impact through the integration of carbon fiber (CF) into Self-Compacting Concrete (SCC). Experimental trials included varying CF weights (0.2%, 0.4%, 0.6%, 0.8%, and 1.0%), assessing fresh and hardened concrete properties, and evaluating durability factors such as Acid Attack and Water Absorption, along with embodied carbon. Incorporating CF mitigates sagging and improves durability over time. Optimal improvements were observed with 0.6% CF, resulting in a significant 20.21% increase in compressive strength and a notable 58.38% enhancement in split tensile strength. Using Response Surface Methodology (RSM), a model was developed to optimize CF integration. Carbon fiber improves concrete by reinforcing the matrix, reducing micro-cracks, enhancing strength, and preventing segregation. In hardened concrete, it acts as secondary reinforcement, increasing strength and durability by reducing permeability. This lowers water absorption and improves resistance to acid attacks. Additionally, it reduces embodied carbon, lessening environmental impact while maintaining structural integrity. This study enhances our understanding of carbon fiber's benefits in concrete, guiding future development.

Key Words
carbon fiber; embodied carbon; mechanical properties; RSM; sustainability

Address
Arivumani V: Department of Architecture, Sigma College of Architecture, Anducode - 629168, Tamilnadu, India
Thiru S: Department of Mechanical and Materials Engineering, University of Jeddah, Jeddah - 21959, Kingdom of Saudi Arabia
Sivarethinamohan R: Department of Management Studies, Symbiosis Centre for Management Studies, Constituent of Symbiosis International Deemed University, Bengaluru - 560100, Karnataka, India
Hemavathi S: Department of Civil Engineering, K Ramakrishnan College of Technology, Trichy - 621112, Tamilnadu, India

Abstract
At present, the dynamics research of beams is mostly limited to free vibration and forced vibration, and the research on nonlinear transient response is little, and no one has studied the nonlinear transient response of beams with initial geometric imperfection under pulse loads. Based on this fact, the transient response characteristics of graphene platelet reinforced metal foams (GPLRMF) beams with initial geometric defects are discussed for the first time in this paper. Firstly, three kinds of graphene platelet (GPL) distribution patterns and foam metal porosity distribution patterns were considered, and the material properties were calculated by means of micromechanical models and mixture diffusion rules, and then, considering initial geometric defects, a dynamic model was established based on Euler-Bernoulli beam theory and von-Kármán nonlinear theory. Then, based on the Hamilton principle, the motion equation of the GPLRMF beam is derived. Finally, the corresponding transient response curve is obtained using the fourth-order Runge-Kutta method. In the study, the convergence of the model is verified to ensure the rationality and accuracy of the analysis results. In addition, a detailed study is conducted, including the distribution patterns and coefficients of porosity, the dispersion and weight fraction of GPLs, pulse load parameters, initial geometric imperfections and damping coefficient.

Key Words
blast pulse load; GPLRMF beam; initial geometric imperfection; nonlinear transient responses

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

Abstract
Nonlinear forced vibration analysisof a sandwich beam is investigated using the higher-order shear deformation theories (HSDT's). The sandwich beam is consists of viscoelastic core insert between two Functionally Graded Material layers. Viscoelastic properties are considered according to the Kelvin-Voigt viscoelastic model for isotropic materials. In the analysis, both normal and shear deformations are considered in the core by using the higher-order zig-zag theories. The method of multiple scales is coupled with a one mode Galerkin's procedure for a simply supported beam to achieve analytical frequency amplitude relationships for superharmonic resonance. Parametric study is conducted by considering various geometrical and material parameters, employing HSDT's and first-order deformation theory. The results reveal the effect of the slenderness of the sandwich beams on the hardening changes. In the other hand the results demonstrate the importance of the generic parameter "n" to reduce as far as possible the amplitude responses of the sandwich structures in superharmonic vibration case.

Key Words
forced nonlinear vibration; functionally graded material; higher-order shear theories; Kelvin-Voigt viscoelastic model; multiple scale method; perturbation method

Address
Hadj Youzera: Laboratoire d'Etude des Structures et de Mécanique des Matériaux, Département de Génie Civil, Faculté des Sciences et de la Technologie, Université Mustapha Stambouli B.P. 305, R.P. 29000 Mascara, Algérie
Sid Ahmed Meftah: Laboratoire des Structures et Matériaux Avancés dans le Génie Civil et Travaux Publics, Université DjillaliLiabes, Sidi Bel Abbes, Algérie
Abdelouahed Tounsi: 1) Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia, 2) Department of Civil and Environmental Engineering, Lebanese American University, 309 Bassil Building, Byblos, Lebanon
Khaled Mohamed Khedher: Department of Civil Engineering, College of Engineering, King Khalid University,Abha 61421, Saudi Arabia
Mohamed Abdelaziz Salem: Department of Mechanical Engineering, College of Engineering, King Khalid University, Abha 61421, Saudi Arabia
Murat Yaylaci: 1) Department of Civil Engineering, Recep Tayyip Erdogan University, 53100, Rize, Turkey, 2) TurgutKiran Maritime Faculty, Recep Tayyip Erdogan University, 53900, Rize, Turkey, 3) Murat Yaylaci-Luzeri R&D Engineering Company, 53100, Rize, Turkey

Abstract
Latex modified concrete (LMC) possesses improved cracking strength and higher durability characteristics than concrete without latex. LMC overlays are typically used to increase the service life of bridge decks. On the other hand, the increasing use of high-performance concrete (HPC) in bridge deck slabs might affect the performance of LMC overlays due to the considerable difference between LMC and HPC characteristics. In this study, numerical analysis was performed using 2D linear Finite Element (FE) model coupled with Monte-Carlo simulation to examine the effect of the characteristics of the substrate, including differential shrinkage, overlay-to-substrate stiffness ratio, and cracking capacity on the probability of cracking (POC) and the probability of delamination (POD) of LMC bridge deck overlays. In addition, 3D nonlinear FE model was constructed to assess the effect of interface cracks on the structural response of bridge deck. It was found that high differential shrinkage strains and high stiffness differences between LMC and HPC can increase tensile stresses at the interface. The probability of cracking and delamination is governed by the tensile strength of the bridge deck substrate and crack development at the interface reduces the stiffness of bridge deck significantly.

Key Words
finite element model; high performance concrete; latex modified concrete; Monte-Carlo simulation; overlays; probability of cracking

Address
Eslam M. Soliman: Civil Engineering Department, Assiut University, Assiut, 71516 Egypt
Kyoung-Kyu Choi: School of Architecture, Soongsil University, 369 Sang-doro, Dongjak-gu, Seoul, 06978 South Korea
Mahmoud M. Reda Taha: Gerlad May Department of Civil, Construction, and Environmental Engineering, University of New Mexico, Albuquerque, New Mexico 87131-0001, USA

Abstract
Deterioration components (DCs) of reinforced concrete columns are important for the seismic performance assessment of reinforced concrete (RC) structures. DCs in RC columns includes: plastic chord rotation from yield to cap (Ɵp), post-capping plastic rotation capacity from the cap to point of zero strength (Ɵpc), and normalized energy dissipation capacity (lambda). This paper investigates several machine learning (ML) algorithms for the prediction of DCs, referred to as ML-DCs, based on the results of 255 experimental tests conducted on reinforced concrete columns from 1973 to 2002. Also in this research, for the prediction of DCs, a learning-based prediction model is developed in a stacking ensemble framework, that is the training of several different basic models and their combination through the training of a meta-model to make a final prediction based on predictions made by the basic models. AdaBoost, Random Forest (RF), Support Vector Regression (SVR) and XGBoost algorithms are base learners. Among the ML algorithms, stacking ensembles showed the best results with a correlation coefficient (R2) of 0.778 for Ɵp, 0.703 for Ɵpc, and 0.809 for lambda. The results of ML algorithms indicate that the ML models are more effective than the empirical relationships that are based on the experimental results.

Key Words
artificial intelligence; concrete columns; deterioration components; machine learning; moment-rotation curves; stacking model

Address
A.Khoshkroodi and H.Parvini Sani: Department of Civil Engineering, Zanjan Branch, Islamic Azad University, Zanjan, Iran
M.Sadeghi: Centre for Mathematical Plasma Astrophysics (CmPA), KU Leuven, Celestijnenlaan 200B bus 2400, B-3001 Leuven, Belgium

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