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CONTENTS
Volume 25, Number 6, June 2020
 

Abstract
This paper, presents the dynamic and stability analysis of the simply supported single walled Carbon Nanotubes (SWCNT) reinforced concrete beam on elastic-foundation using an integral first-order shear deformation beam theory. The condition of the zero shear-stress on the free surfaces of the beam is ensured by the introduction of the shear correction factors. The SWCNT reinforcement is considered to be uniform and variable according to the X, O and V forms through the thickness of the concrete beam. The effective properties of the reinforced concrete beam are calculated by employing the rule of mixture. The analytical solutions of the buckling and free vibrational behaviors are derived via Hamilton\'s principle and Navier method. The analytical results of the critical buckling loads and frequency parameters of the SWCNT-RC beam are presented in the form of explicit tables and graphs. Also the diverse parameters influencing the dynamic and stability behaviors of the reinforced concrete beam are discussed in detail.

Key Words
dynamic; stability analysis; SWCNT concrete beam; Hamilton\'s principle; Navier solution; rule of mixture

Address
Fouad Bourada: Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department, University of Sidi Bel Abbes, Algeria; Departement des Sciences et de la Technologie, Centre Universitaire de Tissemsilt, BP 38004, Ben Hamouda, Algerie; Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals,
31261 Dhahran, Eastern Province, Saudi Arabia
Abdelmoumen Anis Bousahla: Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia; Laboratoire de Modelisation et Simulation Multi-echelle, Universite de Sidi Bel Abbes, Algeria
Abdeldjebbar Tounsi: Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department, University of Sidi Bel Abbes, Algeria; Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia
E.A. Adda Bedia: Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia
S.R. Mahmoud: GRC Department, Jeddah Community College, King Abdulaziz University, Jeddah, Saudi Arabia
Kouider Halim Benrahou: Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department, University of Sidi Bel Abbes, Algeria; Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia
Abdelouahed Tounsi: Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department, University of Sidi Bel Abbes, Algeria; Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia

Abstract
This paper presents a numerical method for evaluating fire performance of prestressed concrete (PC) T shaped bridge girders under combined effect of structural loading and hydrocarbon fire exposure conditions. A numerical model, developed using the computer program ANSYS, is employed to investigate fire response of PC T shaped bridge girders by taking into consideration structural inherent parameters, namely; arrangement of prestressing strands with in the girder section, thickness of concrete cover over prestressing strands, effective degree of prestress and content of prestressing strands. Then, a sequential thermo-mechanical analysis is performed to predict cross sectional temperature followed by mechanical response of T shaped bridge girders. The validity of the numerical model is established by comparing temperatures, deflections and failure time generated from fire tests. Through numerical studies, it is shown that thickness of concrete cover and arrangement of prestressing strands in girder section have significant influence on the fire resistance of PC T shaped bridge girders. Increase in effective degree of prestress in strands with triangular shaped layout and content in prestressing strands can slow down the progression of deflections in PC T shaped bridge girder towards the final stages of fire exposure, to thereby preventing sudden collapse of the girder. Rate of deflection based failure criterion governs failure in PC T shaped bridge girders under most hydrocarbon fire exposure conditions. Structural inherent parameters incorporated into sectional configuration can significantly enhance fire resistance of PC bridge girders; thus mitigating fire induced collapse of these bridge girders.

Key Words
bridge fires; fire resistance; hydrocarbon fire; prestressed concrete bridge girder; numerical modeling

Address
Gang Zhang, Chaojie Song, Wei Hou and Shuanhai He: School of Highway, Chang\'an University, Xi\'an, Shaanxi 710064, China
Venkatesh Kodur: Department of Civil and Environmental Engineering, Michigan State University, East Lansing, MI 48864, USA

Abstract
Adding fibers improves concrete performance in respect of strength and plasticity. There are numerous fibers for use in concrete that have different mechanical properties, and their combination in concrete changes its behavior. So, to investigate the behavior of the fiber reinforced concrete, an in vitro study was conducted on concrete with different fiber compositions including different ratios of steel, polypropylene and glass fibers with the volume of 1%. Two forms of fibers including singlestranded and aggregated fibers have been used for testing, and the specimens were tested for compressive strength and dividable tensile strength (splitting tensile) to determine the optimal ratio of the composition of fibers in the concrete reinforced by hybrid fibers. The results show that the concrete with a composition of steel fibers has a better performance than other compounds. In addition, by adding glass and propylene fibers to the composition of steel fibers, the strength of the samples is reduced. Also, if using the combination of fibers is required, the use of a combination of glass fibers with steel fibers will provide a better compressive strength and tensile strength than the combination of steel fibers with propylene.

Key Words
steel fibers; propylene fibers; glass fiber; compressive strength; dividable tensile strength

Address
Ali Ghamari: Department of Civil Engineering, Darreh Shahr Branch, Islamic Azad University, Darreh Shahr, Iran
Javad Kurdi: Department of Structural Engineering, Vali-e-Asr University Of Rafsanjan, Rafsanjan, Iran
Alireza Bagher Shemirani: Faculty of Civil, Water and Environmental Engineering, Shahid Beheshti University, Tehran, Iran
Hadi Haeri: State Key Laboratory for Deep GeoMechanics and Underground Engineering, Beijing, 100083, China

Abstract
An experimental system on three point bending notched beams was established to study the fracture process of concrete. In this system, the acoustic emission (AE) was used to build the cumulative generation order (AGO) and dynamically track the process of microcrack evolution in concrete. A grey-cusp catastrophe model was built based on AE parameters. The results show that the concrete beams have significant catastrophe characteristic. The developed grey-cusp catastrophe model, based on AGO, can well describe the catastrophe characteristic of concrete fracture process. This study also provides a theoretical and technical support for the application of AE in concrete fracture prediction.

Key Words
concrete; damage; catastrophe model; grey-cusp theory; acoustic emission

Address
Zhonggou Chen: School of Landscape Architecture, Zhejiang Agriculture and Forestry University, Hangzhou 311300, China
Chuanqing Fu: College of Civil Engineering and Architecture, Zhejiang University of Technology, Hangzhou 310034, China
Yifeng Ling: National Concrete Pavement Technology Center, Institute for Transportation, IA 50014, USA
Xianyu Jin: College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058, China

Abstract
The use of pile foundations has become more popular in recent years, as the combined action of the pile cap and the piles can increase the bearing capacity, reduce settlement, and the piles can be arranged so as to reduce differential deflection in the pile cap. Piles are relatively long, slender members that transmit foundation loads through soil strata of low bearing capacity to deeper soil or rock strata having a high bearing capacity. In this study analysis of pile cap with considering different parameters like depth of the pile cap, width and breadth of the pile cap, type of piles and different types of soil which affect the behaviour of pile cap foundation is carried out by using Finite Element Software ANSYS. For understanding the settlement behaviour of pile cap foundation, parametric studies have been carried out in four types of clay by varying pile cap dimensions with two types of piles namely normal and under-reamed piles for different group of piles. Furthermore, the analysis results of settlement and stress values for the pile cap with normal and under-reamed piles are compared. From the study it can be concluded that settlement values of pile cap with under-reamed pile are less than the settlements of pile cap with normal pile. It means that the ultimate load bearing capacity of pile cap with under-reamed piles are greater than the pile cap with normal piles.

Key Words
pile foundation; under-reamed pile; settlement analysis; finite element method; clay soils; bearing capacity

Address
Madisetti Pavan Kumar: Civil Engineering, SVP Engineering College, Visakhapatnam, Andhra Pradesh, 530041, India
P. Markandeya Raju: Civil Engineering, MVGR College of Engineering (A), Vizianagaram, Andhra Pradesh, 535005, India
G. Vincent Jasmine: Civil Engineering, Raghu Engineering College (A), Visakhapatnam, Andhra Pradesh, 531162, India
Mantini Aditya: Structural Engineering, SVP Engineering College, Visakhapatnam, Andhra Pradesh, 530041, India

Abstract
Geometrically nonlinear axisymmetric bending analysis of shear deformable circular plates on a nonlinear threeparameter elastic foundation was made. Plates ranging from \"thin\" to \"moderately thick\" were investigated for three types of material: isotropic, transversely isotropic, and orthotropic. The differential equations were discretized by means of the finite difference method (FDM) and the differential quadrature method (DQM). The Newton-Raphson method was applied to find the solution. A parametric investigation using seven unknowns per node was presented. The novelty of the paper is that detailed numerical simulations were made to highlight the combined effects of the material properties and the boundary conditions on (i) the deflection, (ii) the stress resultants, and (iii) the external load. The formulation was verified through comparison studies. It was observed that the results are highly influenced from the boundary conditions, and from the material properties.

Key Words
plate; nonlinear; Pasternak, Winkler; foundation; deflection

Address
Murat Altekin: Department of Civil Engineering, Yildiz Technical University, 34220 Istanbul, Turkey

Abstract
This paper investigates the artificial neural network (ANN) to predict the dimensionless parameters for the maximum contact pressures and contact areas of a contact problem. Firstly, the problem is formulated and solved theoretically by using Theory of Elasticity and Integral Transform Technique. Secondly, the contact problem has been extended based on the ANN. The multilayer perceptron (MLP) with three-layer was used to calculate the contact distances. External load, distance between the two quarter planes, layer heights and material properties were created by giving examples of different values were used at the training and test stages of ANN. Program code was rewritten in C++. Different types of network structures were used in the training process. The accuracy of the trained neural networks for the case was tested using 173 new data which were generated via theoretical solutions so as to determine the best network model. As a result, minimum deviation value (difference between theoretical and C++ ANN results) of was obtained for the network model. Theoretical results were compared with artificial neural network results and well agreements between them were achieved.

Key Words
contact problem; artificial neural network; quarter plane; multilayer perceptron; theory of elasticity

Address
Ecren Uzun Yaylaci: Department of Fisheries Technology Engineering, Karadeniz Technical University, Trabzon, Turkey
Murat Yaylaci: Department of Civil Engineering, Recep Tayyip Erdogan University, Rize, Turkey
Hasan Ölmez: Department of Marine Engineering Operations, Karadeniz Technical University, Trabzon, Turkey
Ahmet Birinci: Department of Civil Engineering, Karadeniz Technical University, Trabzon, Turkey

Abstract
Over the years, several machine learning approaches have been proposed and utilized to create a prediction model for the high-performance concrete (HPC) slump flow. Despite HPC is a highly complex material, predicting its pattern is a rather ambitious process. Hence, choosing and applying the correct method remain a crucial task. Like some other problems, prediction of HPC slump flow suffers from abnormal attributes which might both have an influence on prediction accuracy and increases variance. In recent years, different studies are proposed to optimize the prediction accuracy for HPC slump flow. However, more state-of-the-art regression algorithms can be implemented to create a better model. This study focuses on several methods with different mathematical backgrounds to get the best possible results. Four well-known algorithms Support Vector Regression, M5P Trees, Random Forest, and MLPReg are implemented with optimum parameters as base learners. Also, redundant features are examined to better understand both how ingredients influence on prediction models and whether possible to achieve acceptable results with a few components. Based on the findings, the MLPReg algorithm with optimum parameters gives better results than others in terms of commonly used statistical error evaluation metrics. Besides, chosen algorithms can give rather accurate results using just a few attributes of a slump flow dataset.

Key Words
multilayer perceptron regression; regression trees; support vector regression; redundant features, M5P trees

Address
Ramazan Unlu: Management and Information Systems, Gumushane University, 29000 Gümüşhane, Turkey

Abstract
Based on a refined shear deformation finite strip, transient vibrations of graphene oxide powder (GOP) reinforced plates due to external pulse loads have been investigated. The plate has uniformly and linearly distributed GOPs inside material structure. Applied pulse loads have been selected as sinusoidal, linear and blast types. Such pulse loads result in transient vibrations of the GOP-reinforced plates which are not explored before. Finite strip method (FSM) has been performed for solving the equations of motion and then inverse Laplace transform technique has been employed to derive transient responses due to pulse loading. It is reported in this study that the transient responses of GOP-reinforced plates are dependent on GOP dispersions, GOP volume fraction, type of pulse loading, loading time and load locations.

Key Words
transient response; vibration; graphene oxide powder; concrete plate; finite strip; pulse load

Address
Seyed Sajad Mirjavadi: Department of Mechanical and Industrial Engineering, Qatar University, P.O. Box 2713, Doha, Qatar
Masoud Forsat: Department of Civil and Architectural Engineering, Qatar University, Doha, Qatar
Mohammad Reza Barati: Fidar Project Qaem Company, Darvazeh Dolat, Tehran, Iran
A.M.S. Hamouda: Department of Mechanical and Industrial Engineering, Qatar University, P.O. Box 2713, Doha, Qatar


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