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CONTENTS
Volume 48, Number 2, July 25 2023
 

Abstract
The present manuscript aims to investigate the deviation between the middle surface (MS) and neutral surface (NS) formulations on the static response of bi-directionally functionally graded (BDFG) porous plate. The higher order shear deformation plate theory with a four variable is exploited to define the displacement field of BDFG plate. The displacement field variables based on both NS and on MS are presented in detail. These relations tend to get and derive a new set of boundary conditions (BCs). The porosity distribution is portrayed by cosine function including three different configurations, center, bottom, and top distributions. The elastic foundation including shear and normal stiffnesses by Winkler–Pasternak model is included. The equilibrium equations based on MS and NS are derived by using Hamilton's principles and expressed by variable coefficient partial differential equations. The numerical differential quadrature method (DQM) is adopted to solve the derived partial differential equations with variable coefficient. Rigidities coefficients and stress resultants for both MS and NS formulations are derived. The mathematical formulation is proved with previous published work. Additional numerical and parametric results are developed to present the influences of modified boundary conditions, NS and MS formulations, gradation parameters, elastic foundations coefficients, porosity type and porosity coefficient on the static response of BDFG porous plate. The following model can be used in design and analysis of BDFG structure used in aerospace, vehicle, dental, bio-structure, civil and nuclear structures.

Key Words
BDFG porous plates; differential quadrature method; middle and Neutral surfaces formulations; modified boundary conditions; static analysis

Address
Amr E. Assie:1)Mechanical Engineering Department, Faculty of Engineering, Jazan University, P. O. Box 45142, Jazan, Kingdom of Saudi Arabia 2)Department of Mechanical Design and Production, Faculty of Engineering, Zagazig University, P.O. Box 44519, Zagazig, Egypt

Salwa A. Mohamed:Department of Engineering Mathematics, Faculty of Engineering, Zagazig University, P.O. Box 44519, Zagazig, Egypt

Alaa A. Abdelrahman:Department of Mechanical Design and Production, Faculty of Engineering, Zagazig University, P.O. Box 44519, Zagazig, Egypt

Mohamed A. Eltaher:Mechanical Engineering Department, Faculty of Engineering, King Abdulaziz University, P.O. Box 80204, Jeddah, Saudi Arabia
4Department of Mechanical Design and Production, Faculty of Engineering, Zagazig University, P.O. Box 44519, Zagazig, Egypt

Abstract
The CFRP bar was used to achieve more ductile and durable headed-stud shear connectors in composite components. Three series of push-out tests were firstly conducted, including specimens reinforced with pure steel fibers, steel and CFRP bars. The distributed stress was measured by the commercial PPP-BOTDA (Pre-Pump-Pulse Brillouin optical time domain analysis) optical fiber sensor with high spatial resolution. A series of numerical analyses using non-linear FE models were also made to study the shear force transfer mechanism and crack response based on the test results. Test results show that the CFRP bar increases the shear strength and stiffness of the large diameter headed-stud shear connection, and it has equivalent reinforcing effects on the stud shear capacity as the commonly used steel bar. The embedded CFRP bar can also largely improve the shear force transfer mechanism and decrease the tensile stress in the transverse direction. The parametric study shows that low content steel fibers could delay the crack initiation of slab around the large diameter stud, and the CFRP bar with normal elastic modulus and the standard reinforcement ratio has good resistance to splitting crack growth in headed stud shear connectors.

Key Words
CFRP bar; headed stud shear connector; PPP-BOTDA; push-out test; SFRC

Address
Huawen Ye, Wenchao Wang, Ao Huang and Zhengyuan Wang:School of Civil Engineering, Southwest Jiaotong University, Chengdu 610031, China

Abstract
This study investigates the influences of porosity on the stability of the orthotropic laminated plates under uniaxial and biaxial loadings based on the hyperbolic shear deformation theory. Three different porosity distribution are considered with three specific functions through the plate thickness. The stability equations of porous orthotropic laminated plates are derived by the virtual work principle. Applying the Galerkin method to partial differential equations, the critical buckling load relation of porous orthotropic laminated plates is obtained. After validating the accuracy of the proposed formulation in accordance with the available literature, a parametric analysis is performed to observe the sensitivity of the critical buckling load to shear deformation, porosity, orthotropy, loading factor, and different geometric properties.

Key Words
critical buckling load; laminated plate; orthotropy; porosity; porous plate; shear deformation theory; stability

Address
Ferruh Turan:Department of Civil Engineering of Engineering Faculty, Ondokuz Mayis University, 55139, Samsun, Turkey

Abstract
Complex and intricate preparation techniques, the imperative for utmost precision and sensitivity in instrumentation, premature sample failure, and fragile specimens collectively contribute to the arduous task of measuring the fracture toughness of concrete in the laboratory. The objective of this research is to introduce and refine an equation based on the gene expression programming (GEP) method to calculate the fracture toughness of reinforced concrete, thereby minimizing the need for costly and time-consuming laboratory experiments. To accomplish this, various types of reinforced concrete, each incorporating distinct ratios of fibers and additives, were subjected to diverse loading angles relative to the initial crack (α)in order to ascertain the effective fracture toughness (Keff) of 660 samples utilizing the central straight notched Brazilian disc (CSNBD) test. Within the datasets, six pivotal input factors influencing the Keff of concrete, namely sample type (ST), diameter (D), thickness (t), length (L), force (F), and α, were taken into account. The ST and a parameters represent crucial inputs in the model presented in this study, marking the first instance that their influence has been examined via the CSNBD test. Of the 660 datasets, 460 were utilized for training purposes, while 100 each were allotted for testing and validation of the model. The GEP model was finetuned based on the training datasets, and its efficacy was evaluated using the separate test and validation datasets. In subsequent stages, the GEP model was optimized, yielding the most robust models. Ultimately, an equation was derived by averaging the most exemplary models, providing a means to predict the Keff parameter. This averaged equation exhibited exceptional proficiency in predicting the Keff of concrete. The significance of this work lies in the possibility of obtaining the Keff parameter without investing copious amounts of time and resources into the CSNBD test, simply by inputting the relevant parameters into the equation derived for diverse samples of reinforced concrete subject to varied loading angles.

Key Words
central straight notched Brazilian disc; concrete fracture toughness; effective fracture toughness; gene expression programming

Address
Ahmadreza Khodayari: School of Civil, Environment and Mining Engineering, University of Adelaide, Adelaide,5005, Australia

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

Adil Hussein Mohammed: Department of Communication and Computer Engineering, Faculty of Engineering, Cihan University-Erbil, Kurdistan Region, Iraq

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

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

Hawkar Hashim Ibrahim: Department of Civil Engineering, College of Engineering, Salahaddin University-Erbil, 44002 Erbil, Kurdistan Region, Iraq

Ahmed Babeker Elhag: Department of Civil Engineering, College of Engineering, King Khalid University, Abha 61413, Saudi Arabia

Shima Rashidi: Department of Computer Science, College of Science and Technology, University of Human Development, Sulaymaniyah, Kurdistan Region, Iraq


Abstract
Many recent attempts have sought accurate prediction of pile pullout resistance (Pul) using classical machine learning models. This study offers an improved methodology for this objective. Adaptive neuro-fuzzy inference system (ANFIS), as a popular predictor, is trained by a capable metaheuristic strategy, namely equilibrium optimizer (EO) to predict the Pul. The used data is collected from laboratory investigations in previous literature. First, two optimal configurations of EO-ANFIS are selected after sensitivity analysis. They are next evaluated and compared with classical ANFIS and two neural-based models using well-accepted accuracy indicators. The results of all five models were in good agreement with laboratory Puls (all correlations 〉 0.99). However, it was shown that both EO-ANFISs not only outperform neural benchmarks but also enjoy a higher accuracy compared to the classical version. Therefore, utilizing the EO is recommended for optimizing this predictive tool. Furthermore, a comparison between the selected EO-ANFISs, where one employs a larger population, revealed that the model with the population size of 75 is more efficient than 300. In this relation, root mean square error and the optimization time for the EO-ANFIS (75) were 19.6272 and 1715.8 seconds, respectively, while these values were 23.4038 and 9298.7 seconds for EO-ANFIS (300).

Key Words
equilibrium optimizer; fuzzy logic; geotechnical simulation; pile foundation; pullout resistance

Address
Yuwei Zhao: 1)College of Civil Engineering, Xuzhou University of Technology, Xuzhou 221018, Jiangsu, China 2)Laboratory of Environmental Impact and Structural Safety in Civil Engineering, China University of Mining and Technology, Xuzhou, 221116, Jiangsu, China

Mesut Gor: Firat University, Engineering Faculty, Civil Engineering Department, Division of Geotechnical Engineering, 23119, Elazig, Turkey

Daria K. Voronkova: 1)Department of Mathematics and Natural Sciences, Gulf University for Science and Technology, Mishref Campus, Kuwait 2)Bauman Moscow State Technical University Moscow, Russia

Hamed Gholizadeh Touchaei: Department of Civil Engineering, Southern Illinois University Edwardsville, Edwardsville, IL 62026, USA

Hossein Moayedi and Binh Nguyen Le:1)Institute of Research and Development, Duy Tan University, Da Nang 550000, Vietnam 2)School of Engineering & Technology, Duy Tan University, Da Nang, Vietnam


Abstract
The present research investigates how micromechanical models affect the behavior of Functionally Graded (FG) plates under different boundary conditions. The study employs diverse micromechanical models to assess the effective material properties of a two-phase particle composite featuring a volume fraction of particles that continuously varies throughout the thickness of the plate. Specifically, the research examines the vibrational response of the plate on a Winkler-Pasternak elastic foundation, considering different boundary conditions. To achieve this, the governing differential equations and boundary conditions are derived using Hamilton's principle, which is based on a four-variable shear deformation refined plate theory. Additionally, the Galerkin method is utilized to compute the plate's natural frequencies. The study explores how the plate's natural frequencies are influenced by various micromechanical models, such as Voigt, Reuss, Hashin-Shtrikman bounds, and Tamura, as well as factors such as boundary conditions, elastic foundation parameters, length-to-thickness ratio, and aspect ratio. The research results can provide valuable insights for future analyses of FG plates with different boundaries, utilizing different micromechanical models.

Key Words
boundary conditions; functionally graded plates; micromechanical modeling; natural frequency; WinklerPasternak foundation

Address
Tao Hai: 1)School of Computer and Information, Qiannan Normal University for Nationalities, Duyun, Guizhou, 558000, China 2)State Key Laboratory of Public Big Data, Guizhou University, Guizhou Guiyang, 550025, China 3)Faculty of Computing, Universiti Teknologi Malaysia (UTM), UTM Skudai, Johor Bahru 81310, Johor, Malaysia

A. Yvaz: World-class research center

Abstract
Steel-concrete composite box girder bridges are widely used in the construction of highway and railway bridges both domestically and abroad due to their advantages of being light weight and having a large spanning ability and very large torsional rigidity. Composite box girder bridges exhibit the effects of shear lag, restrained torsion, distortion and interface bidirectional slip under various loads during operation. As one of the most commonly used calculation tools in bridge engineering analysis, one-dimensional models offer the advantages of high calculation efficiency and strong stability. Currently, research on the one-dimensional model of composite beams mainly focuses on simulating interface longitudinal slip and the shear lag effect. There are relatively few studies on the one-dimensional model which can consider the effects of restrained torsion, distortion and interface transverse slip. Additionally, there are few studies on vehicle-bridge integrated systems where a one-dimensional model is used as a tool that only considers the calculations of natural frequency, mode and moving load conditions to study the dynamic response of composite beams. Some scholars have established a dynamic analysis model of a coupled composite beam bridge-train system, but where the composite beam is only simulated using a Euler beam or Timoshenko beam. As a result, it is impossible to comprehensively consider multiple complex force effects, such as shear lag, restrained torsion, distortion and interface bidirectional slip of composite beams. In this paper, a 27 DOF vehicle rigid body model is used to simulate train operation. A two-node 26 DOF finite beam element with composed box beams considering the effects of shear lag, restrained torsion, distortion and interface bidirectional slip is proposed. The dynamic analysis model of the coupled composite box girder bridge-train system is constructed based on the wheel-rail contact relationship of vertical closefitting and lateral linear creeping slip. Furthermore, the accuracy of the dynamic analysis model is verified via the measured dynamic response data of a practical composite box girder bridge. Finally, the dynamic analysis model is applied in order to study the influence of various mechanical effects on the dynamic performance of the vehicle-bridge system.

Key Words
biaxial slip; constrained torsion; coupled steel-concrete composite bridge-train system; distortion; dynamic analysis; shear lag

Address
Li Zhu,Wei Liu, Tian-Nan Han and Chao Chen:School of Civil Engineering, Beijing Jiaotong University, Beijing, China

Ray Kai-Leung Su:Department of Civil Engineering, The University of Hong Kong, Hong Kong, China


Abstract
The present paper examines the stability analysis of the buckling differentiae of the small-scale, non-uniform porosity-dependent functionally graded (PD-FG) tube. The high-order beam theory and nonlocal strain gradient theory are operated for the mathematical modeling of nanotubes based on the Hamilton principle. In this paper, the external radius function is non-uniform. In contrast, the internal radius is uniform, and the cross-section changes along the tube length due to these radius functions based on the four types of useful mathematical functions. The PD-FG material distributions are varied in the radial direction and made with ceramics and metals. The governing partial differential equations (PDEs) and associated boundary conditions are solved via a numerical method for different boundary conditions. The received outcomes concerning different presented parameters are valuable to the design and production of small-scale devices and intelligent structures.

Key Words
buckling analysis; FGM; high-order theory; nonuniform structures; numerical solution, porosity

Address
Peng Zhang:Faculty of Architecture and Civil Engineering, Huaiyin Institute of Technology, Huaian, Jiangsu 223001, China

Jun Song:2)School of Civil Engineering, Shandong Jiaotong University, Jinan 250357, Shandong, China
3)China Communications Second Highway Survey, Design and Research Institute Co., Ltd, Wuhan 430050, Hubei, China
4)School of Civil and Hydraulic Engineering, Huazhong University of Science and Technology, Wuhan 430074, Hubei, China

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

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