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CONTENTS
Volume 52, Number 3, August 10 2024
 

Abstract
In this scientific work, an analytical solution for the dynamic analysis of cross-ply and angle-ply laminated composite plates is proposed. Due to technical issues during the manufacturing of composite materials, porosities and microvoids can be produced within the composite material samples, which can carry on to a reduction in the density and strength of the materials. In this research, the laminated composite plates are assumed to have new distributions of porosities over the plate cross-section. The structure is modeled using a simple integral shear deformation theory in which the transverse shear deformation effect is included. The governing equations of motion are obtained employing the principle of Hamilton's. The solution is determined via Navier'sapproach. The Maple program is used to obtain the numerical results. In the numerical examples, the effects of geometry, ratio, modulus ratio, fiber orientation angle, number of layers and porosity parameter on the natural frequencies of symmetric and anti-symmetric laminated composite plates is presented and discussed in detail. Also, the impacts of the kinds of porosity distribution models on the natural frequencies of symmetric and anti-symmetric laminated composite plates are investigated.

Key Words
anti-symmetric; laminated, frequencies; porosity; shear deformation

Address
Hayat Saidi:Hayat Saidi, Abdelouahed Tounsi, Fouad Bourada, Abdelmoumen Anis Bousahla. Abdeldjebbar Tounsi and Firas Ismail Salman Al-Juboori

Abdelouahed Tounsi:1)Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria
2)Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran,
Eastern Province, Saudi Arabia
3)Department of Civil and Environmental Engineering, Lebanese American University, 309 Bassil Building, Byblos, Lebanon

Fouad Bourada:Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria

Abdelmoumen Anis Bousahla:Laboratoire de Modélisation et Simulation Multi-echelle, Université de Sidi Bel Abbes, Algeria

Abdeldjebbar Tounsi:Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria

Firas Ismail Salman Al-Juboori:Faculty of civil Engineering, University of Malaysia Phang

Abstract
This paper presents a three-dimensional displacement-based formulation to investigate the free vibration of functionally graded nanoplates resting on a Winkler-Pasternak foundation based on the nonlocal elasticity theory. The material properties of the FG nanoplate are considered to vary continuously through the thickness of the nanoplate according to the power-law distribution model. A general three-dimensional displacement field is considered for the plate, which takes into account the out-of-plane strains of the plate as well as the in-plane strains. Unlike the shear deformation theories, in the present formulation, no predetermined form for the distribution of displacements and transverse strains is considered. The equations of motion for functionally graded nanoplate are derived based on Hamilton's principle. The solution is obtained for simplysupported nanoplate, and the predicted results for natural frequencies are compared with the predictions of shear deformation theories which are available in the literature. The predictions of the present theory are discussed in detail to investigate the effects of power-law index, length-to-thickness ratio, mode numbers and the elastic foundation on the dynamic behavior of the functionally graded nanoplate. The present study presents a three-dimensional solution that is able to determine more accurate results in predicting of the natural frequencies of flexural and thickness modes of nanoplates. The effects of parameters that play a key role in the analysis and mechanical design of functionally graded nanoplates are investigated.

Key Words
free vibration; functionally graded nanoplate; nonlocal elasticity theory; three-dimensional formulation; winkler-pasternak foundation

Address
Mahsa Najafi:Advanced Materials and Computational Mechanics Lab., Department of Mechanical Engineering, University of Zanjan, 45371-38791, Zanjan, Iran

Isa Ahmadi:Advanced Materials and Computational Mechanics Lab., Department of Mechanical Engineering, University of Zanjan, 45371-38791, Zanjan, Iran

Vladimir Sladek:Institute of Construction and Architecture, Slovak Academy of Sciences, 84503, Bratislava, Slovakia

Abstract
Researchers are actively investigating the potential for utilizing alternative materials in construction to tackle the environmental and economic challenges linked to traditional concrete-based materials. Nevertheless, conventional laboratory methods for testing the mechanical properties of concrete are both costly and time-consuming. The limitations of traditional models in predicting the tensile strength of concrete composited with geopolymer have created a demand for more advanced models. Fortunately, the increasing availability of data has facilitated the use of machine learning methods, which offer powerful and cost-effective models. This paper aims to explore the potential of several machine learning methods in predicting the tensile strength of geopolymer concrete under different curing conditions. The study utilizes a dataset of 221 tensile strength test results for geopolymer concrete with varying mix ratios and curing conditions. The effectiveness of the machine learning models is evaluated using additional unseen datasets. Based on the values of loss functions and evaluation metrics, the results indicate that most models have the potential to estimate the tensile strength of geopolymer concrete satisfactorily. However, the Takagi Sugeno fuzzy model (TSF) and gene expression programming (GEP) models demonstrate the highest robustness. Both the laboratory tests and machine learning outcomes indicate that geopolymer concrete composed of 50% fly ash and 40% ground granulated blast slag, mixed with 10 mol of NaOH, and cured in an oven at 190°F for 28 days has superior tensile strength.

Key Words
geopolymer concrete; reinforced concrete; supervised learning algorithms; tensile strength

Address
Ibrahim Albaijan:Mechanical Engineering Department, College of Engineering at Al-Kharj, Prince Sattam Bin Abdulaziz University, Al Kharj 16273, Saudi Arabia

Hanan Samadi:IRO, Civil Engineering Department, University of Halabja, Halabja, 46018, Iraq

Arsalan Mahmoodzadeh:IRO, Civil Engineering Department, University of Halabja, Halabja, 46018, Iraq

Danial Fakhri:IRO, Civil Engineering Department, University of Halabja, Halabja, 46018, Iraq

Mehdi Hosseinzadeh:1)Institute of Research and Development, Duy Tan University, Da Nang, Vietnam
2)School of Medicine and Pharmacy, Duy Tan University, Da Nang, Vietnam

Nejib Ghazouani:Department of Civil Engineering, College of Engineering, Northern Border University, Arar 73222, Saudi Arabia

Khaled Mohamed Elhadi:1)Civil Engineering Department, College of Engineering, King Khalid University, Saudi Arabia
2)Center for Engineering and Technology Innovations, King Khalid University, Abha 61421, Saudi Arabia

Abstract
This work presents experimental and numerical investigations on the flexural performances of composite deep-deck plate slabs. Seven deep-deck plate slab specimens with topping concrete were fabricated; the height of the topping slab as well as presence and type of shear connector were set as the main variables to perform bending experiments. The flexural behaviors of the specimens and composite behaviors of the deck plate and concrete were analyzed in detail. The contributions of the deck plate to the flexural stiffness and strength of the slab were identified through finite element (FE) analysis. FE analysis was carried out using the validated FE model by considering the varying bond strengths of the deck plates and concrete, thickness of the deck plate, and types and spacings of the shear connectors. Based on the results, the degree of composite of the deep-deck plate was examined, and a flexural strength equation for the composite deck plate slabs was proposed.

Key Words
deep-deck plate; degree of composite; finite element analysis; flexural performance; shear connector

Address
Inwook Heo:Urban Safety and Security Research Institute, University of Seoul, 163 Seoulsiripdae-ro, Dongdaemun-gu, Soeoul 02504, Republic of Korea

Sun-Jin Han:Department of Architectural Engineering, Jeonju University, 303, Cheonjam-ro, Wansan-gu, Jeollabuk-do, Republic of Korea

Khaliunaa Darkhanbat:Department of Architectural Engineering, University of Seoul, 163 Seoulsiripdae-ro, Dongdaemun-gu, Soeoul 02504, Republic of Korea

Seung-Ho Choi:Department of Fire and Disaster Prevention Engineering, University of Seoul, 163 Seoulsiripdae-ro, Dongdaemun-gu, Soeoul 02504, Republic of Korea

Sung Bae Kim:The Naeun Structural Engineering, 1310-1311, 21, Yangpyeong-ro 22-gil, Yeongdeungpo-gu, Seoul, Republic of Korea

Kang Su Kim:Department of Architectural Engineering and Smart City Interdisciplinary Major Program, University of Seoul, 163 Seoulsiripdae-ro, Dongdaemun-gu, Soeoul 02504, Republic of Korea


Abstract
This paper is the first in a series of articles dealing with the study and analysis of imperfections in thin-walled, coldformed steel sections with modified cross-sectional shapes. A study was conducted, using 3D scanning techniques, to determine the most vulnerable geometric imperfections in the profiles. Based on a review of the literature, it has been determined that few researchers are studying thin-walled sections with modified cross-sectional shapes. Each additional bend in the section potentially generates geometric imperfections. Geometric imperfections significantly affect the resistance to loss of stability, which is crucial when analyzing thin-walled structures. In addition, the most critical locations along the length where these imperfections occur were determined. Based on the study, it was found that geometric imperfections cause a reduction in critical load. It should be noted that the tests performed are preliminary studies, based on which a program of further research will be developed. In addition, the article presents the current state of knowledge in the authors' field of interest. The future objective is to ascertain if these imperfections could potentially contribute positively to structural integrity. This enhanced understanding may pave the way for novel methodologies in structural engineering, wherein imperfections are viewed not solely as flaws but also as elements that could enhance the end product.

Key Words
3D scanning; experimental tests; FEM; imperfections; thin-walled structures

Address
Aleksandra M. Pawlak:Division of Strength of Materials and Structures, Poznan University of Technology, Jana Pawla II 24, 61-131 Poznan, Poland

Tomasz A. Górny:Division of Strength of Materials and Structures, Poznan University of Technology, Jana Pawla II 24, 61-131 Poznan, Poland

Michal Plust:Division of Strength of Materials and Structures, Poznan University of Technology, Jana Pawla II 24, 61-131 Poznan, Poland

Piotr Paczos:Division of Strength of Materials and Structures, Poznan University of Technology, Jana Pawla II 24, 61-131 Poznan, Poland

Jakub Kasprzak:Division of Strength of Materials and Structures, Poznan University of Technology, Jana Pawla II 24, 61-131 Poznan, Poland

Abstract
This paper presents an analytical solution for correctly predicting the Lateral-Torsional Buckling critical moment of simply supported castellated beams, the solution covers uniformly distributed loads combined with compressive loads. For this purpose, the castellated beam section with hexagonal-type perforation is treated as an arrangement of double "T" sections, composed of an upper T section and a lower T section. The castellated beam with regular openings is considered as a periodic repeating structure of unit cells. According to the kinematic model, the energy principle is applied in the context of geometric nonlinearity and the linear elastic behavior of materials. The differential equilibrium equations are established using Galerkin's method and the tangential stiffness matrix is calculated to determine the critical lateral torsional buckling loads. A Finite Element simulation using ABAQUS software is performed to verify the accuracy of the suggested analytical solution, each castellated beam is modelled with appropriate sizes meshes by thin shell elements S8R, the chosen element has 8 nodes and six degrees of freedom per node, including five integration points through the thickness, the Lanczos eigen-solver of ABAQUS was used to conduct elastic buckling analysis. It has been demonstrated that the proposed analytical solution results are in good agreement with those of the finite element method. A parametric study involving geometric and mechanical parameters is carried out, the intensity of the compressive load is also included. In comparison with the linear solution, it has been found that the linear stability underestimates the lateral buckling resistance. It has been confirmed that when high axial loads are applied, an impressive reduction in critical loads has been observed. It can be concluded that the obtained analytical solution is efficient and simple, and offers a rapid and direct method for estimating the lateral torsional buckling critical moment of simply supported castellated beams.

Key Words
castellated beams; Galerkin's method; lateral-torsional buckling; tangential stiffness matrix

Address
Saoula Abdelkader:1)Department of Civil Engineering, University of Ibn Khaldoun, BP 78 Zaaroura, 14000 Tiaret, Algeria 2) Laboratoire de l' Ingenierie Mecanique, Materiaux et Structures-LIMMaS. Universite de Tissemsilt. Ben Hamouda BP 38004 Tissemsilt, Algeria

Abdelrahmane B. Benyamina:1)Department of Civil Engineering, University of Ibn Khaldoun, BP 78 Zaaroura, 14000 Tiaret, Algeria 2) Laboratoire de l' Ingenierie Mecanique, Materiaux et Structures-LIMMaS. Universite de Tissemsilt. Ben Hamouda BP 38004 Tissemsilt, Algeria

Meftah Sid Ahmed:Laboratoire des Structures et Materiaux Avances dans le Genie Civil et Travaux Publics,
Universite Djillali Liabes, Sidi Bel Abbes, Algerie

Abstract
In this paper, weakly bonded ultra-high-strength steel bars (UHSS) were used as longitudinal reinforcement in recycled aggregate concrete shear walls to achieve resilient performance. The study evaluated the repairability and hysteresis performance of shear walls before and after retrofitting. Quasi-static tests were performed on recycled aggregate concrete (RAC) and steel fiber reinforced recycled aggregate concrete (FRAC) shear walls to investigate the reparability of resilient shear walls when loaded to 1% drift ratio. Results showed that shear walls exhibited drift-hardening properties. The maximum residual drift ratio and residual crack width at 1% drift ratio were 0.107% and 0.01 mm, respectively, which were within the repairable limits. Subsequently, shear walls were retrofitted with bonded X-shaped CFRP strips and steel plates wrapped at the bottom and retested. Except for a slight reduction in initial stiffness, earthquake-damaged resilient shear walls retrofitted with a composite method still had satisfactory hysteresis performance. A revised damage assessment index D, has been proposed to assess of damage degree. Moreover, finite-element analysis for the shear wall before and after retrofit retrofitting was established in OpenSees and verified with experimental results. The finite element results and test results were in good agreement. Finally, parametric analysis was performed.

Key Words
carbon-fiber-reinforced polymers; damage assessment; hysteresis performance; resilient shear walls; retrofit

Address
Jianwei Zhang:Key Laboratory of Urban Security and Disaster Engineering of the Ministry of Education, Beijing University of Technology, Beijing 100124, China

Siyuan Wang:Key Laboratory of Urban Security and Disaster Engineering of the Ministry of Education, Beijing University of Technology, Beijing 100124, China

Man Zhang:Key Laboratory of Urban Security and Disaster Engineering of the Ministry of Education, Beijing University of Technology, Beijing 100124, China

Yuping Sun:Department of Architecture, Graduate School of Engineering, Kobe University, Kobe 657-8501, Japan

Hongwei Wang:Key Laboratory of Urban Security and Disaster Engineering of the Ministry of Education, Beijing University of Technology, Beijing 100124, China


Abstract
Analyzing thermoelastic, elastoplastic, and residual stresses is pivotal for deepening our insights into material characteristics, particularly in the engineering of advanced materials like functionally graded materials (FGM). This research delves into these stress types within a thick-walled sphere composed of Al-SiC FGM, employing a detailed successive approximation method (SAM) to pinpoint stress distributions under varied loading scenarios. Our investigation centers on how the sphere's structure responds to different magnitudes of internal pressure. We discover that under various states— thermoelastic, elastoplastic, and residual—the radial stresses are adversely impacted, manifesting negative values due to the compressive nature induced by internal pressures. Notably, the occurrence of reverse yielding, observed at pressures above 410 MPa, merits attention due to its significant implications on the sphere's structural integrity and operational efficacy. Employing the SAM allows us to methodically explore the nuanced shifts in material properties across the sphere's thickness. This study not only highlights the critical behaviors of Al-SiC FGM spheres under stress but also emphasizes the need to consider reverse yielding phenomena to maintain safety and reliability in their application. We advocate for ongoing refinement of analytical techniques to further our understanding of stress behaviors in various FGM configurations, which could drive the optimized design and practical application of these innovative materials in diverse engineering fields.

Key Words
elastoplastic; residual stress; stress distribution; thermoelastic; thick-walled sphere

Address
Thaier J. Ntayeesh:Faculty of Mechanical Engineering, College of Engineering, University of Baghdad Baghdad 10071, Iraq

Mohsen Kholdi:Faculty of Mechanical Engineering, Department of Solid Mechanics, University of Kashan, Kashan 87317-51167, Iran

Soheil Saeedi:Faculty of Mechanical Engineering, Department of Solid Mechanics, University of Kashan, Kashan 87317-51167, Iran

Abbas Loghman:Faculty of Mechanical Engineering, Department of Solid Mechanics, University of Kashan, Kashan 87317-51167, Iran

Mohammad Arefi:Faculty of Mechanical Engineering, Department of Solid Mechanics, University of Kashan, Kashan 87317-51167, Iran

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