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Volume 50, Number 4, February 25 2024

The network theory studies interconnection between discrete objects to find about the behavior of a collection of objects. Also, nanomaterials are a collection of discrete atoms interconnected together to perform a specific task of mechanical or/and electrical type. Therefore, it is reasonable to use the network theory in the study of behavior of super-molecule in nanoscale. In the current study, we aim to examine vibrational behavior of spherical nanostructured composite with different geometrical and materials properties. In this regard, a specific shear deformation displacement theory, classical elasticity theory and analytical solution to find the natural frequency of the spherical nano-composite structure. The analytical results are validated by comparison to finite element (FE). Further, a detail comprehensive results of frequency variations are presented in terms of different parameters. It is revealed that the current methodology provides accurate results in comparison to FE results. On the other hand, different geometrical and weight fraction have influential role in determining frequency of the structure.

Key Words
complex networks; mathematical simulation; mechanical behavior; nanotechnology

Nacer Rahal: 1)Department of Civil Engineering, Mustapha Stambouli university, Mascara, 29000, Algeria 2)4Laboratory of mechanical structure and construction stability, USTO, Oran 31000 Algeria

Abdelaziz Souici:1)Department of Civil Engineering, Mustapha Stambouli university, Mascara, 29000, Algeria 2)4Laboratory of mechanical structure and construction stability, USTO, Oran 31000 Algeria

Houda Beghdad:Department of Civil Engineering, Mustapha Stambouli university, Mascara, 29000, Algeria

Mohamed Tehami:1)Department of Civil Engineering, University of Sciences and Technology, Oran, 31000, Algeria 2)4Laboratory of mechanical structure and construction stability, USTO, Oran 31000 Algeria

Dris Djaffari:Department of Civil Engineering, University Ahmed Draia of Adrar, an Advanced Institute for Science and Technology, Algeria

MohamedSadoun:Department of Civil Engineering, Mustapha Stambouli university, Mascara, 29000, Algeria

Khaled Benmahdi:Department of Civil Engineering, Mustapha Stambouli university, Mascara, 29000, Algeria

The research comprehensively studies the axial compression performance of T-shaped concrete-filled thin-walled steel tubular (CTST) long columns after fire exposure. Initially, a series of tests investigate the effects of heating time, load eccentricity, and stiffeners on the column's performance. Furthermore, Finite Element (FE) analysis is employed to establish temperature and mechanical field models for the T-shaped CTST long column with stiffeners after fire exposure, using carefully determined key parameters such as thermal parameters, constitutive relations, and contact models. In addition, a parametric analysis based on the numerical models is conducted to explore the effects of heating time, section diameter, material strength, and steel ratio on the axial compressive bearing capacity, bending bearing capacity under normal temperature, as well as residual bearing capacity after fire exposure. The results reveal that the maximum lateral deformation occurs near the middle of the span, with bending increasing as heating time and eccentricity rise. Despite a decrease in axial compressive load and bending capacity after fire exposure, the columns still exhibit desirable bearing capacity and deformability. Moreover, the obtained FE results align closely with experimental findings, validating the reliability of the developed numerical models. Additionally, this study proposes a simplified design method to calculate these mechanical property parameters, satisfying the ISO-834 standard. The relative errors between the proposed simplified formulas and FE models remain within 10%, indicating their capability to provide a theoretical reference for practical engineering applications.

Key Words
after fire; axial compressive load; experimental investigation; finite element analysis; residual bearing capacity; T-shaped concrete-filled thin-walled steel tubular long column

Xuetao Lyu:Advanced and Sustainable Infrastructure Materials Group, School of Transportation and Civil Engineering & Architecture, Foshan University, Foshan, Guangdong 528000, China

Weiwei Wang:School of Architectural Engineering, Guangzhou Vocational and Technical University of Science and Technology, Guangzhou, Guangdong 510550, China

Huan Li:Centre for Infrastructure Monitoring and Protection, School of Civil and Mechanical Engineering, Curtin University, Kent Street, Bentley, WA 6102, Australia

Jiehong Li:Centre for Infrastructure Engineering and Safety, School of Civil and Environmental Engineering,
The University of New South Wales, Sydney, NSW 2052, Australia

Yang Yu:Centre for Infrastructure Engineering and Safety, School of Civil and Environmental Engineering,
The University of New South Wales, Sydney, NSW 2052, Australia

In this paper, vibration and energy absorption characteristics of a nanostructure which is composed of two embedded porous annular/circular nanoplates coupled by a viscoelastic substrate are investigated. The modified couple stress theory (MCST) and the Gurtin-Murdoch theory are applied to take into account the size and the surface effects, respectively. Furthermore, the structural damping effect is probed by the Kelvin-Voigt model and the mathematical model of the problem is developed by a new hyperbolic higher order shear deformation theory. The differential quadrature method (DQM) is employed to obtain the out-of-phase and in-phase frequencies of the structure in order to predict the dynamic response of it. The acquired results reveal that the vibration and energy absorption of the system depends on some factors such as porosity, surface stress effects, material length scale parameter, damping and spring constants of the viscoelastic foundation as well as geometrical parameters of annular/circular nanoplates. A bird's-eye view of the findings in the research paper offers a comprehensive understanding of the vibrational behavior and energy absorption capabilities of annular/circular porous nanoplates. The multidisciplinary approach and the inclusion of porosity make this study valuable for the development of innovative materials and applications in the field of nanoscience and engineering.

Key Words
coupled annular/circular nanoplates; Differential quadrature method (DQM); energy absorption; out-ofphase and in-phase vibrations; size and surface effects

Guangli Fan:Xi'an Siyuan University, Xi'an, Shaanxi,710038, China

Maryam Shokravi:Department of Education, Mehrab High School, Saveh, Iran

Rasool Javani:Department of Civil Engineering, Jasb Branch, Islamic Azad University, Jasb, Iran

Suxa Hou:Department of Civil Engineering, Malaysia University, Malaysia

Prefabricated partially-encased composite (PEC) structural component is widely used in construction industry due to its superior structural performance and easy assembly characteristic. However, the solid web in traditional PEC components tends to split concrete into two halves, thus potentially reduces structural integrity and requires double concrete pouring. To overcome the above disadvantages, a new PEC beam with open-web π-shaped steel is proposed in this paper. Four open-web PEC beams with varying sectional height, flange thickness and web void rate were constructed and tested under flexural loads. During experimental tests, all beams exhibited typical flexural failure modes with strong moment capacities and excellent ductility. Owing to the unique construction form of web opening, steel-concrete bonding properties were enhanced and very small relative steel-concrete slips were observed. Experimental results also showed that the flexural capacity of such PEC beams increased with the increase of the sectional height and flange thickness, while was not affected by the web void rate. At last, a flexural capacity formula of the open-web PEC beam was proposed based on the whole section plastic rule. The formula results agreed well with experimental results.

Key Words
flange thickness; flexural capacity; open-web π-shaped steel; Partially-Encased Composite (PEC) beams; prediction formula; sectional height; web void rate

Liusheng Chu and Yunhui Chen:School of Civil Engineering, Zhengzhou University, 450001, Zhengzhou, China

Jie Li:Sanda University, 201209, Shanghai, China

Yukun Yang:Shanghai Jieyi Architectural Consulting Firm, 202150, Shanghai, China

Danda Li and Xing Ma:University of South Australia, SA 5095, Adelaide, Australia

This paper studies the free vibration behavior of trapezoidal shaped coupled double-layered graphene sheets (DLGS) system using first-order shear deformation theory (FSDT) and incorporating nonlocal elasticity theory. Two nanoplates are assumed to be bonded by an interlayer van der walls force and surrounded by an external kelvin-voight viscoelastic medium. The governing equations together with related boundary condition are discretized using a mapping-differential quadrature method (DQM) in the spatial domain. Then the natural frequency of the system is obtained by solving the eigen value matrix equation. The validity of the current study is evaluated by comparing its numerical results with those available in the literature and then a parametric study is thoroughly performed, concentrating on the series effects of angles and aspect ratio of GS, viscoelastic medium, and nonlocal parameter. The model is used to study the vibration of DLGS for two typical deformation modes, the in-phase and out-of-phase vibrations, which are investigated. Numerical results indicate that due to Increasing the damping parameter of the viscoelastic medium has reduced the frequency of both modes and this medium has been able to overdamped the oscillations and by increasing stiffness parameters both in-phase and out-of-phase vibration frequencies increased.

Key Words
DLGS; free vibration; general boundary conditions; trapezoidal plate; viscoelastic medium

S. Abdul Ameer:Department of Automobile Engineering College of Engineering/Al-Musayab University of Babylon, Iraq

Abbas Hameed Abdul Hussein:Ahl Al Bayt University Kerbala, Iraq

Mohammed H. Mahdi:College of pharmacy, Ahl Al Bayt University Kerbala, Iraq

Fahmy Gad Elsaid:Biology Department, College of Science, King Khalid University, Asir, Abha, Al-Faraa, P.O. Box: 960-Postal Code: 61421, Saudi Arabia

V. Tahouneh:School of Mechanical Engineering, University of Tehran, Tehran, Iran

The construction industry, one of the biggest producers of greenhouse emissions, is under a lot of pressure as a result of growing worries about how climate change may affect local communities. Geopolymer concrete (𝐺𝑃𝐶) has emerged as a feasible choice for construction materials as a result of the environmental issues connected to the manufacture of cement. The findings of this study contribute to the development of machine learning methods for estimating the properties of eco-friendly concrete, which might be used in lieu of traditional concrete to reduce 𝐶𝑂2 emissions in the building industry. In the present work, the compressive strength (𝑓𝑐 ) of 𝐺𝑃𝐶 is calculated using random forests regression (𝑅𝐹𝑅) methodology where natural zeolite (𝑁𝑍) and silica fume (𝑆𝐹) replace ground granulated blast-furnace slag (𝐺𝐺𝐵𝐹𝑆). From the literature, a thorough set of experimental experiments on 𝐺𝑃𝐶 samples were compiled, totaling 254 data rows. The considered 𝑅𝐹𝑅 integrated with artificial hummingbird optimization (𝐴𝐻𝐴), black widow optimization algorithm (𝐵𝑊𝑂𝐴), and chimp optimization algorithm (𝐶ℎ𝑂𝐴), abbreviated as 𝐴𝑅𝐹𝑅, 𝐵𝑅𝐹𝑅, and 𝐶𝑅𝐹𝑅. The outcomes obtained for 𝑅𝐹𝑅 models demonstrated satisfactory performance across all evaluation metrics in the prediction procedure. For 𝑅 2 metric, the 𝐶𝑅𝐹𝑅 model gained 0.9988 and 0.9981 in the train and test data set higher than those for 𝐵𝑅𝐹𝑅 (0.9982 and 0.9969), followed by 𝐴𝑅𝐹𝑅 (0.9971 and 0.9956). Some other error and distribution metrics depicted a roughly 50% improvement for 𝐶𝑅𝐹𝑅 respect to 𝐴𝑅𝐹𝑅.

Key Words
compressive strength; geopolymer concrete; natural zeolite; random forests regression; silica fume

Ying Bi:School of Civil Engineering and Architecture, Zhengzhou Shengda University of Economics,
Business & Management; Henan Zhengzhou, 451191, China

Yeng Yi:Department of Civil Engineering, Huazhong University, Wuhan, Hubei, China

Classical and first-order nonlocal beam theory are employed in this study to assess the thermal buckling performance of a small-scale conical, cylindrical beam. The beam is constructed from functionally graded (FG) porositydependent material and operates under the thermal conditions of the environment. Imperfections within the non-uniform beam vary along both the radius and length direction, with continuous changes in thickness throughout its length. The resulting structure is functionally graded in both radial and axial directions, forming a bi-directional configuration. Utilizing the energy method, governing equations are derived to analyze the thermal stability and buckling characteristics of a nanobeam across different beam theories. Subsequently, the extracted partial differential equations (PDE) are numerically solved using the generalized differential quadratic method (GDQM), providing a comprehensive exploration of the thermal behavior of the system. The detailed discussion of the produced results is based on various applied effective parameters, with a focus on the potential application of nanotubes in enhancing sports bikes performance.

Key Words
functionally graded structures; nonuniform structures; numerical analysis; sport; thermal buckling; thermal stability

Chaobing Yan:Department of Teacher Education, Lishui University, Lishui 323000, Zhejiang, China

Tong Zhang:Sports department, Zhongnan University of Economics and Law, Wuhan 430073, Hubei, China

Ting Zheng:School of Ecology, Lishui University, Lishui 323000, Zhejiang, China

Tayebeh Mahmoudi:Hoonam Sanat Farnak, Engineering and technology company, Ilam, Iran

The usage of fiber-reinforced polymer materials increases in the construction sector due to their advantages in terms of high mechanical strength, lightness, corrosion resistance, low density and high strength/density ratio, low maintenance and painting needs, and high workability. In this study, it is aimed to improve mechanical properties of GFRP box profiles, produced by pultrusion method, by filling the polymer concrete into them. Within the scope of study, hybrid use of polymer concrete produced with GFRP box profiles was investigated. Hybrid pressure and bending specimens were produced by filling polymer concrete (polyester resin manufactured with natural sand and stone chips) into GFRP box profiles having different cross-sections and dimensions. Behavior of the produced hybrid members was investigated under bending and compression tests. Hollow GFRPₓₓ profiles, polymer-filled hybrid members, and nominative polymeric concrete specimens were tested as well. The behavior of the specimens under pressure and bending tests, and their load bearing capacities, deformations and changes in toughness were observed. According to the test results; It was deduced that hybrid design has many advantages over its component materials as well as superior physical and mechanical properties.

Key Words
bending strength; compressive strength; Glass Fiber Reinforced Plastic (GFRP); hybrid beam; polymer concrete

Ali Saribiyik:Department of Civil Engineering, Sakarya University of Applied Sciences, 54187 Sakarya, Turkiye

Ozlem Ozturk:Department of Civil Engineering, Sakarya University of Applied Sciences, 54187 Sakarya, Turkiye

Ferhat Aydin:Department of Civil Engineering, Sakarya University of Applied Sciences, 54187 Sakarya, Turkiye

Yasin Onuralp Ozkilic:1)Department of Civil Engineering, Necmettin Erbakan University, 42140 Konya, Türkiye
2)Department of Civil Engineering, Lebanese American University, Byblos 1102-2801, Lebanon

Emrah Madenci:Department of Civil Engineering, Necmettin Erbakan University, 42140 Konya, Turkiye

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