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CONTENTS
Volume 68, Number 4, November25 2018
 

Abstract
In the present paper, we offer a new flat shell finite element. It is the result of the combination of a membrane element and a bending element, both based on the strain-based formulation. It is known that Co plane membrane elements provide poor deflection and stress for problems where bending is dominant. In addition, they encounter continuity and compliance problems when they connect to C1 class plate elements. The reach of the present work is to surmount these problems when a membrane element is coupled with a thin plate element in order to construct a shell element. The membrane element used is a triangular element with four nodes, three nodes at the vertices of the triangle and the fourth one at its barycenter. Each node has three degrees of freedom, two translations and one rotation around the normal. The coefficients related to the degrees of freedom at the internal node are subsequently removed from the element stiffness matrix by using the static condensation technique. The interpolation functions of strain, displacements and stresses fields are developed from equilibrium conditions. The plate element used for the construction of the present shell element is a triangular four-node thin plate element based on Kirchhoff plate theory, the strain approach, the four fictitious node, the static condensation and the analytic integration. The shell element result of this combination is robust, competitive and efficient.

Key Words
finite element method; membrane; plate; shell; condensation; deformation approach; drilling rotation

Address
Hamza Guenfoud, Mohamed Himeur and Mohamed Guenfoud: LGCH Laboratory, 8 Mai 1945 University of Guelma, Algeria
Hassina Ziou: Mohamed Khider University, Biskra, Algeria

Abstract
Cable supported structures have been widely used in civil engineering. Cable tension estimation has great importance in cable supported structures\' analysis, ranging from design to construction and from inspection to maintenance. Even though the Bernoulli-Euler beam element is commonly used in the traditional finite element method for calculation of frequency and cable tension estimation, many elements must be meshed to achieve accurate results, leading to expensive computation. To improve the accuracy and efficiency, a dynamic finite element method for estimation of cable tension is proposed. In this method, following the dynamic stiffness matrix method, frequency-dependent shape functions are adopted to derive the stiffness and mass matrices of an exact beam element that can be used for natural frequency calculation and cable tension estimation. An iterative algorithm is used for the exact beam element to determine both the exact natural frequencies and the cable tension. Illustrative examples show that, compared with the cable tension estimation method using the conventional beam element, the proposed method has a distinct advantage regarding the accuracy and the computational time.

Key Words
dynamic finite element; frequency-dependent shape function; frequency calculation; cable tension estimation

Address
Yonghui Huang: Guangzhou University-Tamkang University Joint Research Center for Engineering Structure Disaster Prevention and Control, Guangzhou University, Guangzhou 510006, China
Quan Gan: Network & Educational Technology Center, Jinan University, Guangzhou 510632, China
Shiping Huang and Ronghui Wang: School of Civil Engineering and Transportation, South China University of Technology, Guangzhou 510640, China

Abstract
In the present paper, functionally graded (FG) materials are presented to investigate the bending analysis of simply supported plates. It is assumed that the material properties of the plate vary through their length according to the power-law form. The displacement field of the present model is selected based on quasi-3D hyperbolic shear deformation theory. By splitting the deflection into bending, shear and stretching parts, the number of unknowns and equations of motion of the present formulation is reduced and hence makes them simple to use. Governing equations are derived from the principle of virtual displacements. Numerical results for deflections and stresses of powerly graded plates under simply supported boundary conditions are presented. The accuracy of the present formulation is demonstrated by comparing the computed results with those available in the literature. As conclusion, this theory is as accurate as other shear deformation theories and so it becomes more attractive due to smaller number of unknowns. Some numerical results are provided to examine the effects of the material gradation, shear deformation on the static behavior of FG plates with variation of material stiffness through their length.

Key Words
FGM; bending; thick plate

Address
Ali Mazari: Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department, University of Sidi Bel Abbes, Algeria
Amina Attia:
1) Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department, University of Sidi Bel Abbes, Algeria
2) Departement de Genie Civil, Institut des Sciences et de la Technologie, Centre Universitaire d\'Ain Temouchent, Algerie
Mohamed Sekkal:
1) Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department, University of Sidi Bel Abbes, Algeria
2) Laboratoire de Modelisation et Simulation Multi-echelle, Departement de Physique, Faculte des Sciences Exactes, Departement de Physique, Universite de Sidi Bel Abbes, Algeria
Abdelhakim Kaci:
1) Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department, University of Sidi Bel Abbes, Algeria
2) Universite Dr Tahar Moulay, Faculte de Technologie, Departement de Genie Civil et Hydraulique, BP 138 Cite En-Nasr 20000 Saida, Algerie
Abdelouahed Tounsi:
1) Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department, University of Sidi Bel Abbes, Algeria
2) Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia
Abdelmoumen Anis Bousahla:
1) Laboratoire de Modelisation et Simulation Multi-echelle, Departement de Physique, Faculte des Sciences Exactes, Departement de Physique, Universite de Sidi Bel Abbes, Algeria
2) Centre Universitaire Ahmed Zabana de Relizane, Algeria
S.R. Mahmoud:
Department of Mathematics, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia

Abstract
In this paper, masonry infilled reinforced concrete (RC) frames are analyzed through a probabilistic approach. A macro-modeling technique, based on an equivalent diagonal pin-jointed strut, has been resorted to for modelling the stiffening contribution of the masonry panels. Since it is quite difficult to decide which mechanical characteristics to assume for the diagonal struts in such simplified model, the strut width is here considered as a random variable, whose stochastic characterization stems from a wide set of empirical expressions proposed in the literature. The stochastic analysis of the masonry infilled RC frame is conducted via the Probabilistic Transformation Method by employing a set of space transformation laws of random vectors to determine the probability density function (PDF) of the system response in a direct manner. The knowledge of the PDF of a set of response indicators, including displacements, bending moments, shear forces, interstory drifts, opens an interesting discussion about the influence of the uncertainty of the masonry infills and the resulting implications in a design process.

Key Words
RC frames; masonry infills; macro-modeling approaches; probability transformation method; probability density function; probability-based design

Address
Dario De Domenico, Giovanni Falsone and Rossella Laudani: Department of Engineering, University of Messina, Contrada Di Dio, 98166 Sant\'Agata, Messina, Italy

Abstract
In this article, a comparative study has been made to investigate the scattering behaviour of three layered structure model on torsional surface wave. For such model intermediate layer is taken as fiber reinforced composite, resting over a dry sandy Gibson substratum and underlying by different anelastic media. We consider two distinct mediums for topmost layer. In the first case, topmost layer has been taken as fluid saturated homogeneous porous layer, while in the second case the fluid saturated porous layer has been replaced by a transversely isotropic layer. Simple form expression for the secular equation of torsional surface wave has been worked out in both the cases by executing specific boundary conditions, which comprises Whittaker\'s function and its derivative, for imminent result that have been elaborated asymptotically. Some special cases have been constituted which are in excellent compliance with recorded literatures. For the sake of comparative study, numerical estimation and graphical illustration have been accomplished to identify the effects of the width ratio of the layers, Biot\'s gravity parameter, sandy parameter, porosity parameter and other heterogeneity parameters corresponding to the layers and half spaces, horizontal compressive and tensile initial stress on the phase velocity of torsional surface wave.

Key Words
torsional surface wave; transversely isotropy; porosity; fiber reinforcement; dry-sandy; secular equation

Address
Shishir Gupta, Prasenjit Pati, Anand Mandi and Santimoy Kundu: Department of Applied Mathematics, Indian Institute of Technology (Indian School of Mines), Dhanbad, India

Abstract
Temperature fields and temperature deformations induced by time-varying solar radiation, shadow, and heat exchange are of great importance for the ride safety and quality of the maglev system. Accurate evaluations of their effects on the dynamic performances are necessary to avoid unexpected loss of service performance. This paper presents a numerical approach to determine temperature effects on the maglev train/guideway interaction system. Heat flux density and heat transfer coefficient of different components of a 25 m simply supported concrete guideway on Shanghai High-speed Maglev Commercial Operation Line is calculated, and an appropriate section mesh is used to consider the time-varying shadow on guideway surfaces. Based on the heat-stress coupled technology, temperature distributions and deformation fields of the guideway are then computed via Finite Element method. Combining guideway irregularities and thermal deformations as the external excitations, a numerical maglev train/guideway interaction model is proposed to analyze the temperature effect. The responses comparison including and excluding temperature effect indicates that the temperature deformation plays an important role in amplifying the response of a running maglev, and the parameter analysis results suggest that climatic and environmental factors significantly affect the temperature effects on the coupled maglev system.

Key Words
high-speed maglev transport; maglev train/guideway interaction system; thermal analysis; temperature effect; dynamic performance

Address
Long Zhang: College of Civil Engineering, Tongji University, Shanghai 200092, China
JingYu Huang:
1) College of Civil Engineering, Tongji University, Shanghai 200092, China
2) National Maglev Transportation Engineering R&D Center, Tongji University, Shanghai 201804, China

Abstract
Square tubular columns are commonly used in moment resisting frames, while through-diaphragm connection is the most typical configuration detail to connect the H-shaped beam to the column. However, brittle fracture normally occurs at the complete joint penetration weld between the beam flange and the through-diaphragm due to the stress concentration caused by the geometrical discontinuity. Accordingly, three improved types of through-diaphragm are presented in this paper to provide smooth force flow path comparing to that of conventional connections. Tensile tests were conducted on four specimens and the results were analyzed in terms of failure modes, load-displacement response, yield and ultimate capacity, and initial stiffness. Furthermore, strain distributions on the through-diaphragm, the beam flange plate, and the column face were comprehensively evaluated and discussed. It was found that all the proposed three types of improved through-diaphragm connections were able to reduce the stress concentration in the welds between the beam flange and the through-diaphragm. Furthermore, the stress distribution in connection with longer tapered through-diaphragm was more uniform.

Key Words
strain analysis; tensile performance; through-diaphragm; square tube column; load-displacement curve

Address
Ying Qin:
1) Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, and National Prestress Engineering Research Center, School of Civil Engineering, Southeast University, Nanjing, China
2) State Key Laboratory of Subtropical Building Science, South China University of Technology, Guangzhou, China
Jing-Chen Zhang, Peng Shi, Yi-Fu Chen, Yao-Han Xu and Zuo-Zheng Shi: Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, and National Prestress Engineering Research Center, School of Civil Engineering, Southeast University, Nanjing, China

Abstract
This paper presents the results of an experimental study on the structural performance of an innovative GFRP-concrete composite beam construction, which is reinforced with longitudinal GFRP pultruded box-profile and transverse steel stirrups. GFRP perfobond (PBL) shear connectors are employed to enhance the bonding performance between the GFRP profile and the concrete portion. To investigate the shear and flexural performance of this composite system, eight specimens were designed and tested under three-point and four-point bending. The main variables were the height of the composite beam and the shear span-to-depth ratio. The test results indicated that bonding cracks did not occur at the interface between the GFRP profile and the concrete until the final stage of the test. This shows that the specimens performed well as composite beams during the test and that the GFRP PBL connectors were reliable. Based on the test results, two calculation methods were used to determine the flexural and shear capacity of the composite beams. A comparative study of the test and theoretical results suggests that the proposed methods can reasonably predict both the flexural and shear capacities of the specimens, whereas the provisions of ACI 440 are relatively conservative on both counts.

Key Words
GFRP-concrete composite beam; flexural performance; shear performance; experimental study; static load

Address
Yong Yang, Yicong Xue, Tao Zhang and Jing Tian: School of Civil Engineering, Xi

Abstract
Three points bending flexural test was modeled numerically to study the crack propagation in the pre-cracked beams. The pre-existing edge cracks in the beam models were considered to investigate the crack propagation and coalescence paths within the modeled samples. The effects of particle size on the single edge-notched round bar in bending test were considered too. The results show that Failure pattern is constant by increasing the ball diameter. Tensile cracks are dominant mode of failure. These crack initiates from notch tip, propagate parallel to loading axis and coalescence with upper model boundary. Number of cracks increase by decreasing the ball diameter. Also, tensile fracture toughness was decreased with increasing the particle size. In the present study, the influences of particles sizes on the cracks propagations and coalescences in the brittle materials such as rocks and concretes are numerically analyzed by using a three dimensional particle flow code (PFC3D). These analyses improve the understanding of the stability of rocks and concretes structures such as rock slopes, tunnel constructions and underground openings.

Key Words
SENRBB test; pre-existing edge cracks; PFC3D

Address
Hadi Haeri and Zheming Zhu:MOE Key Laboratory of Deep Underground Science and Engineering, School of Architecture and Environment, Sichuan University, Chengdu 610065, China
Vahab Sarfarazi: Department of Mining Engineering, Hamedan University of Technology, Hamedan, Iran


Abstract
In this research the effect of bedding layer angle and bedding layer thickness on the shear failure mechanism of concrete has been investigated using PFC3D. For this purpose, firstly calibration of PFC3d was performed using Brazilian tensile strength. Secondly punch shear test was performed on the bedding layer. Thickness of layers were 5 mm, 10 mm and 20 mm. in each thickness layer, layer angles changes from 0o to 90o with increment of 25o. Totally 15 model were simulated and tested by loading rate of 0.016 mm/s. The results show that when layer angle is less than 50o, tensile cracks initiates between the layers and propagate till coalesce with model boundary. Its trace is too high. With increasing the layer angle, less layer mobilizes in failure process. Also, the failure trace is very short. It\'s to be note that number of cracks decrease with increasing the layer thickness. The minimum shear punch test strength was occurred when layer angle is more than 50o. The maximum value occurred in 0o. Also, the shear punch test tensile strength was increased by increasing the layer thickness.

Key Words
bedding layer; shear punch test; anisotropy; tensile crack; PFC3D

Address
Hadi Haeri and Zheming Zhu: MOE Key Laboratory of Deep Underground Science and Engineering, School of Architecture and Environment, Sichuan University, Chengdu 610065, China
Vahab Sarfarazi: Department of Mining Engineering, Hamedan University of Technology, Hamedan, Iran


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