Techno Press
Tp_Editing System.E (TES.E)
Login Search


sem
 
CONTENTS
Volume 75, Number 1, July10 2020
 

Abstract
Present research is aimed to investigate the free vibration behavior of functionally graded (FG) nanocomposite conical panel reinforced by graphene platelets (GPLs) on the elastic foundation. Winkler-Pasternak elastic foundation surrounds the mentioned shell. For each ply, graphaene platelets are randomly oriented and uniformly dispersed in an isotropic matrix. It is assumed that the Volume fraction of GPLs reainforcement could be different from layer to layer according to a functionally graded pattern. The effective elastic modulus of the conical panel is estimated according to the modified Halpin-Tsai rule in this manuscript. Cone is modeled based on the first order shear deformation theory (FSDT). Hamilton’s principle and generalized differential quadrature (GDQ) approach are also used to derive and discrete the equations of motion. Some evaluations are provided to compare the natural frequencies between current study and some experimental and theoretical investigations. After validation of the accuracy of the present formulation and method, natural frequencies and the corresponding mode shapes of FG-GPLRC conical panel are developed for different parameters such as boundary conditions, GPLs volume fraction, types of functionally graded and elastic foundation coefficients.

Key Words
conical panel; graphene platelets; GDQM; nanocomposite; elastic foundation

Address
Arameh Eyvazian, Farayi Musharavati, Faris Tarlochan: Mechanical and Industrial Engineering Department, Qatar University, Doha, Qatar
Abdolreza Pasharavesh: Mechanical Engineering Department, Sharif University of Technology, Tehran, Iran
Dipen Kumar Rajak: Department of Mechanical Engineering, Sandip Institute of Technology and Research Center, Nashik, India
Mohammed Bakr Husain : Department of Biological and Environmental Sciences, Qatar University, Doha, Qatar
Tron Nhan Tran: Division of Computational Mechatronic, Institute for Computational Science, Ton Duc Thang University, Ho Chi Minh City, Vietnam / Faculty of Electrical & Electronics Engineering, Ton Duc Thang University, Ho Chi Minh City, Vietnam

Abstract
Due to repetitive traffic loadings and environmental attacks, reinforced concrete (RC) bridge deck slabs are suffering from severe degradation, which makes structural repairing an urgency. In this study, the fatigue performance of an RC bridge deck repairing technique using ultra-high performance fiber reinforcement concrete (UHPFRC) overlay is assessed experimentally with a wheel-type loading set-up as well as analytically based on finite element method (FEM) using a crack bridging degradation concept. In both approaches, an original RC slab is firstly preloaded to achieve a partly damaged RC slab which is then repaired with UHPFRC overlay and reloaded. The results indicate that the developed analytical method can predict the experimental fatigue behaviors including displacement evolutions and crack patterns reasonably well. In addition, as the shear stress in the concrete/UHPFRC interface stays relatively low over the calculations, this interface can be simply simulated as perfect. Moreover, superior to the experiments, the numerical method provides fatigue behaviors of not only the repaired but also the unrepaired RC slabs. Due to the high strengths and cracking resistance of UHPFRC, the repaired slab exhibited a decelerated deterioration rate and an extended fatigue life compared with the unrepaired slab. Therefore, the proposed repairing scheme can afford significant strengthen effects and act as a reference for future practices and engineering applications.

Key Words
UHPFRC; RC slab; bridging stress degradation concept; fatigue; moving wheel

Address
Pengru Deng and Takashi Matsumoto: Faculty of Engineering, Hokkaido University, Sapporo, 060-8628, Japan
Ko Kakuma: Civil Engineering Research Institute for Cold Region, Sapporo, 062-8602, Japan
Hiroshi Mitamura: The Calamity Science Institute, Sunbridge Co. Ltd, Sapporo, 007-0870, Japan

Abstract
In this paper the dynamic behavior of an isolated building subjected to idealized near-fault pulses is investigated. The building is represented with a simple 2-DOF model. Both linear and non-linear behavior of the isolation system is considered. Using dimensional analysis, in conjunction with closed form mathematical idealized pulses, appropriate dimensionless parameters are defined and self-similar curves are plotted on dimensionless graphs, based on which various conclusions are reached. In the linear case, the role of viscous damping is examined in detail and the existence of an optimum value of damping along with its significant variation with the number of half-cycles is shown. In the nonlinear case, where the behavior of the building depends on the amplitude of the excitation, the benefits of dimensional analysis are evident since the influence of the dimensionless Π-terms is easily examined. Special consideration is given to the normalized strength of the non-linear isolation system that appears to play a complex role which greatly affects the response of the 2-DOF. In the last part of the paper, a comparison of the responses to idealized pulses between a linear fixed-base SDOF and the respective isolated 2-DOF with both linear and non-linear damping is conducted and it is shown that, under certain values of the superstructure and isolation system characteristics, the use of an isolation system can amplify both the normalized acceleration and displacement of the superstructure.

Key Words
seismic response; near-fault pulses; base-isolation; dimensional analysis; non-linear analysis; earthquake engineering

Address
Denis Istrati: Department of Civil Engineering, University of Nevada-Reno, NV 89577, USA
Constantine C. Spyrakos and Eleni Panou-Papatheodorou: Laboratory of Materials Science and Engineering, School of Chemical Engineering, National Technical University of Athens,
Zografou Campus, 9 Iroon Polytechniou str, 15780, Athens, Greece
Panagiotis G. Asteris: Computational Mechanics Laboratory, School of Pedagogical and Technological Education, Heraklion, GR 14121, Athens, Greece

Abstract
This paper presents a full-scale experimental test to investigate the flexural behavior of an innovative dovetail ultra-high performance concrete (UHPC) joint designed for the 5th Nanjing Yangtze River Bridge. The test specimen had a dimension of 3600 × 1600 × 170 mm, in accordance with the real bridge. The failure mode, crack pattern and structural response were presented. The ductility and stiffness degradation of the tested specimens were explicitly discussed. Test results indicated that different from conventional reinforced concrete slabs, well-distributed cracks with small spacing were observed for UHPC joint slabs at failure. The average nominal flexural cracking strength of the test specimens was 7.7 MPa, signifying good crack resistance of the proposed dovetail UHPC joint. It is recommended that high grade reinforcement be cooperatively used to take full advantage of the superior mechanical property of UHPC. A new ductility index, expressed by dividing the ultimate deflection by flexural cracking deflection, was introduced to evaluate the post-cracking ductility capacity. Finally, a strut-and-tie (STM) model was developed to predict the ultimate strength of the proposed UHPC joint.

Key Words
composite bridge; ultra-high performance concrete (UHPC); joint; flexural behavior; STM model

Address
Key Laboratory of Concrete and Prestressed Concrete Structures of the Ministry of Education, School of Civil Engineering, Southeast University, Nanjing, China

Abstract
The purpose of this study is to develop practical tools for the mechanical design of cylindrical porous media subjected to a broad gap in a hygrothermal environment. The planar axisymmetrical and transient hygrothermoelastic field in a porous hollow cylinder that is exposed to a broad gap of temperature and dissolved moisture content and is free from mechanical constraint on all surfaces is investigated considering the nonlinear coupling between heat and binary moisture and the diffusive properties of both phases of moisture. The system of hygrothermal governing equations is derived for the cylindrical case and solved to illustrate the distributions of hygrothermal-field quantities and the effect of diffusive properties on the distributions. The distribution of the resulting stress is theoretically analyzed based on the fundamental equations for hygrothermoelasticity. The safety hazard because of the analysis disregarding the nonlinear coupling underestimating the stress is illustrated. By comparing the cylinder with an infinitesimal curvature with the straight strip, the significance to consider the existence of curvature, even if it is infinitesimally small, is demonstrated qualitatively and quantitatively. Moreover, by investigating the bending moment, the necessities to consider an actual finite curvature and to perform the transient analysis are illustrated.

Key Words
diffusion; porous medium; binary moisture; nonlinear coupling; hygrothermal stress; cylinder

Address
Masayuki Ishihara, Taku Yoshida, Yoshihiro Ootao: Graduate School of Engineering, Osaka Prefecture University,
1-1 Gakuen-cho, Naka-ku, Sakai-shi, Osaka 599-8531, Japan
Yoshitaka Kameo: nstitute for Frontier Life and Medical Sciences, Kyoto University,
53 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan

Abstract
This paper presents a study on the mechanical behavior of buried pipelines crossing faults using experimental and numerical methods. A self-made soil-box was used to simulate normal fault, strike-slip fault and oblique slip fault. The effects of some important parameters, including the displacement and type of fault, the buried depth and the diameter of pipe, on the deformation modes and axial strain distribution of the buried pipelines crossing faults was studied in the experiment. Furthermore, a finite element analysis (FEA) model of spring boundary was developed to investigate the performance of the buried pipelines crossing faults, and FEA results were compared with experimental results. It is found that the axial strain distribution of those buried pipelines crossing the normal fault and the oblique fault is asymmetrical along the fault plane and that of buried pipelines crossing the strike-slip fault is approximately symmetrical. Additionally, the axial peak strain appears near both sides of the fault and increases with increasing fault displacement. Moreover, the axial strain of the pipeline decreases with decreasing buried depth or increasing ratios of pipe diameter to pipe wall thickness. Compared with the normal fault and the strike-slip fault, the oblique fault is the most harmful to pipelines. Based on the accuracy of the model, the regression equations of the axial distance from the peak axial strain position of the pipeline to the fault under the effects of buried depth, pipe diameter, wall thickness and fault displacement were given.

Key Words
crossing fault; buried pipeline; strain distribution; deformation mode; finite element analysis (FEA); position of peak axial strain

Address
School of Urban Construction, Yangtze University, Jingzhou 434000, China
Dan F. Zhang, Xi. Zeng, Zhen. Lei and Guo F. Du: Hubei Provincial Oil and Gas Storage and Transportation Engineering Technology Research Center, Jingzhou 434000, China
Xue M. Bie: State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian 116024, China


Abstract
The present paper investigates the combination resonance behavior of imperfect spiral stiffened functionally graded (SSFG) cylindrical shells with internal and external functionally graded stiffeners under two-term large amplitude excitations. The structure is embedded within a generalized nonlinear viscoelastic foundation, which is composed of a two-parameter Winkler-Pasternak foundation augmented by a Kelvin-Voigt viscoelastic model with a nonlinear cubic stiffness, to account for the vibration hardening/softening phenomena and damping considerations. With regard to classical plate theory of shells, von-Kármán equation and Hook law, the relations of stress-strain are derived for shell and stiffeners. The spiral stiffeners of the cylindrical shell are modeled according to the smeared stiffener technique. According to the Galerkin method, the discretized motion equation is obtained. The combination resonance is obtained by using the multiple scales method. Finally, the influences of the stiffeners angles, foundation type, the nonlinear elastic foundation coefficients, material distribution, and excitation amplitude on the system resonances are investigated comprehensively.

Key Words
nonlinear vibrations; combination resonance behaviors; spiral stiffened FG cylindrical shell; multiple scales method; geometric imperfections; nonlinear viscoelastic foundation; two-term excitation

Address
Faculty of Mechanical and Mechatronics Engineering, Shahrood University of Technology, Shahrood, Iran

Abstract
The present study intends to analyze damage in thin-walled steel cylinders undergoing constant internal pressure and thermal cycles through use of anisotropic continuum damage mechanics (CDM) model coupled with nonlinear kinematic hardening rule of Chaboche. Materials damage in each direction was defined based on plastic strain and its direction. Stress and strain distribution over wall-thickness was described based on the CDM model and the return mapping algorithm was employed based on the consistency condition. Plastic zone expansion across the wall thickness of cylinders was noticeably affected with change in internal pressure and temperature gradients. Expansion of plastic zone over wall-thickness at inner and outer surfaces and their boundaries demarking elastic and plastic regions was attributed to the magnitude of damage induced over thermo-mechanical cycles on the thin-walled samples tested at various pressure stresses.

Key Words
anisotropic Continuum Damage Mechanics (CDM); cyclic loading; nonlinear kinematic hardening; return mapping algorithm; cylindrical pressure vessel

Address
Azam Surmiri, Ali Nayebi: Mechanical Engineering Department, Shiraz University, Shiraz, Iran
Hojjatollah Rokhgireh: Mechanical Engineering Department, University of Larestan, Lar, Iran
Ahmad Varvani-Farahani: Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, Canada

Abstract
An asymptotic local plane strain elasticity theory is reformulated for the static analysis of a simply-supported, multiple graphene sheet system (MGSS) in cylindrical bending and resting on an elastic medium. The dimension of the MGSS in the y direction is considered to be much greater than those in the x and z directions, such that all the field variables are considered to be independent of the y coordinate. Eringen\'s nonlocal constitutive relations are used to account for the small length scale effects in the formulation examining the static behavior of the MGSS. The interaction between the MGSS and its surrounding foundation is modelled as a Winkler foundation with the parameter kw, and the interaction between adjacent graphene sheets (GSs) is considered using another Winkler model with the parameter cw. A parametric study with regard to some effects on the static behavior of the MGSS resting on an elastic medium is undertaken, such as the aspect ratio, the number of the GSs, the stiffness of the medium between the adjacent layers and that of the surrounding medium of the MGSS, and the nonlocal parameter.

Key Words
Eringen's nonlocal elasticity theory; foundation; multiple graphene sheet systems; nonlocal plane strain elasticity theory; static; the perturbation method

Address
Department of Civil Engineering, National Cheng Kung University, Taiwan, Republic of China

Abstract
The bond performance of glass fibre reinforced polymer (GFRP) bars and that of steel bars embedded in Alkali Activated Cement (AAC) concrete are analysed and compared using pull-out specimens. The bond failure modes, the average bond strength and the free end bond stress-slip curves are used for comparison. Tepfer’s concrete ring model is used to further analyse the splitting failure in ribbed steel bar and GFRP bar specimens. The angle the bond forces make with the bar axis was calculated and used for comparing bond behaviour of ribbed steel bar and GFRP bars in AAC concrete. The results showed that bond failure mode plays a significant role in the comparison of the average bond stress of the specimens at failure. In case of pull-out failure mode, specimens with ribbed steel bars showed a higher bond strength while specimens with GFRP bars showed a higher bond stress in case of splitting failure mode. Comparison of the bond stress-slip curves of ribbed steel bars and GFRP bars depicted that the constant bond stress region at the peak is much smaller in case of GFRP bars than ribbed steel bars indicating a basic bond mechanism difference in GFRP and ribbed steel bars.

Key Words
Alkali activated cement (AAC), GFRP bars, bond behaviour, Pull-out failure, Splitting failure, Bond-angle

Address
School of Engineering and Information Technology, UNSW Canberra, Australia


Techno-Press: Publishers of international journals and conference proceedings.       Copyright © 2020 Techno-Press
P.O. Box 33, Yuseong, Daejeon 34186 Korea, Tel: +82-42-828-7996, Fax : +82-2-736-6801, Email: info@techno-press.com