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CONTENTS
Volume 73, Number 6, March25 2020
 

Abstract
The research study is focuses on a form of all-bolted joint with the external ring stiffening plate in the prefabricated steel structure. The components are bolted at site after being fabricated in the factory. Six specimens were tested under cyclic loading, and the effects of column axial compression ratio, concrete-filled column, beam flange sub plate, beam web angle cleats, and spliced column on the failure mode, hysteretic behavior and ductility of the joints were analyzed. The results shown that the proposed all-bolted joint with external ring stiffening plate performed high bearing capability, stable inflexibility degradation, high ductility and plump hysteretic curve. The primary failure modes were bucking at beam end, cracking at the variable section of the external ring stiffening plate, and finally welds fracturing between external ring stiffening plate and column wall. The bearing capability of the joints reduced with the axial compression ratio increased. The use of concrete-filled steel tube column can increase the bearing capability of joints. The existence of the beam flange sub plate, and beam web angle cleat improves the energy dissipation, ductility, bearing capacity and original rigidity of the joint, but also increase the stress concentration at the variable section of the external reinforcing ring plate. The proposed joints with spliced column also performed desirable integrity, large bearing capacity, initial stiffness and energy dissipation capacity for engineering application by reasonable design.

Key Words
modularized prefabricated steel structure; all-bolted joint; external ring stiffening plate; quasi-static test; failure model

Address
Zhanjing Wu, Zhong Tao, Bei Liu and Heng Zuo: School of Architecture Engineering, Kunming University of Science and Technology, Kunming 650500, China
Zhanjing Wu: Post-doctoral Research Station of Mechanics, Kunming University of Science and Technology, Kunming 650500, China

Abstract
The present paper aims to study the influence of the magnetic field and initial stress on the 2-D problem of generalized thermo-viscoelastic material with voids subject to thermal loading by a laser pulse in the context of the Lord-Shulman and the classical dynamical coupled theories. The analytical expressions for the physical quantities are obtained in the physical domain by using the normal mode analysis. These expressions are calculated numerically for a specific material and explained graphically. Comparisons are made with the results predicted by the Lord-Shulman and the coupled theories in the presence and absence of the initial stress and the magnetic field.

Key Words
Lord-Shulman; thermo-viscoelasticity; initial stress; magnetic field; laser pulse; voids

Address
Mohamed I. A. Othman: Department of Mathematics, Faculty of Science, Zagazig University, P.O. Box 44519, Zagazig, Egypt
Montaser Fekry: Department of Mathematics, Faculty of Science, South Valley University, P.O. Box 83523, Qena, Egypt
Marin Marin: Department of Mathematics and Computer Science , Transilvania University of Brasov, Romania

Abstract
Using backup plate is one of the most commonly used methods to decrease drilling-induced delamination of composite laminates. It has been shown that, the size of the delamination zone is related to the vertical element of cutting force named as thrust force. Also, direct control of thrust force is not a routine task, because, it depends on both drilling parameters and mechanical properties of the composite laminate. In this research, critical feed rate and thrust force are predicted analytically for delamination initiation in drilling of composite laminates with backup plate. Three common theories, linear elastic fracture mechanics, classical laminated plate and mechanics of oblique cutting, are used to model the problem. Based on the proposed analytical model, the effect of drill radius, chisel edge size, and backup plate size on the critical thrust force and feed rate are investigated. Experimental tests were carried out to prove analytical model.

Key Words
composite laminates; backup plate; analytical modelling; delamination; drilling

Address
Hossein Heidary: Department of Mechanical Engineering, Tafresh University, First of Tehran road, Tafresh 3951879611, Iran
Mohammad A. Mehrpouya: Department of Mathematics, Tafresh University, First of Tehran road, Tafresh 3951879611, Iran
Hossein Heidary, Hamed SaghafiNew Technologies Research Center (NTRC), Amirkabir University of Technology, Tehran, 1591633311, Iran
Giangiacomo Minak: Department of Industrial Engineering (DIN), Alma Mater Studiorum, Università di Bologna, 24 Via Terracini, Bologna 40136, Italy

Abstract
The determination of midtower longitudinal stiffness has become an essential component in the preliminary design of multi-tower suspension bridges. For a specific multi-tower suspension bridge, the midtower longitudinal stiffness must be controlled within a certain range to meet the requirements of sliding resistance coefficient and deflection-to-span ratio. This study presents a numerical method to divide different types of midtower and determine rational range of longitudinal stiffness for rigid midtower. In this method, influence curves of midtower longitudinal stiffness on sliding resistance coefficient and maximum vertical deflection-to-span ratio are first obtained from the finite element analysis. Then, different types of midtower are divided based on the regression analysis of influence curves. Finally, rational range for longitudinal stiffness of rigid midtower is derived. The Oujiang River North Estuary Bridge which is a three-tower four-span suspension bridge with two main spans of 800m under construction in China is selected as the subject of this study. This will be the first three-tower four-span suspension bridge with steel truss girders and concrete midtower in the world. The proposed method provides an effective and feasible tool for engineers to design midtower of multi-tower suspension bridges.

Key Words
three-tower suspension bridges; midtower; longitudinal stiffness; sliding resistance; deflection-to-span ratio

Address
Jin Cheng: State Key Laboratory for Disaster Reduction in Civil Engineering, Tongji University, Shanghai, China
Jin Cheng, Hang Xu and Mingsai Xu: Department of Bridge Engineering, Tongji University, Shanghai, China

Abstract
In this study, the spatial variation mechanisms of large far-field earthquakes at engineering scales are first investigated with data from the 2008 Ms 8.0 Wenchuan earthquake. And a novel ‘coherency cut-off frequency’ is proposed to distinguish the spatial variations in ground motions in the low-frequency and high-frequency ranges. Then, a practical piecewise coherency model is developed to estimate and characterize the spatial variation in earthquake ground motions, including the effects of source-to-site distances, site conditions and neighboring topography on these variations. Four particular earthquake records from dense seismograph arrays are used to investigate values of the coherency cut-off frequency for different source-to-site distances. On the basis of this analysis, the model is established to simulate the spatial variations, whose parameters are suitable for both near- and far-field earthquake conditions. Simulations are conducted to validate the proposed model and method. The results show that compared to the existing models, the proposed model provides an effective method for simulating the spatial correlations of ground motions at local sites with known source-to-site distances.

Key Words
spatial variation; coherency function; dense seismograph array; UPSAR; Wenchuan earthquake; Parkfield earthquake; San Simon earthquake

Address
Rui-Fang Yu and Yan-Xiang Yu: Institute of Geophysics, China Earthquake Administration, Beijing, China
Abduwahit Abduwaris: Earthquake Administration of Xinjiang Uyghur Autonomous Region, Wulumuqi, China

Abstract
In this article, the static responses of layered magneto-electro-thermo-elastic (METE) plates in thermal environment have been investigated through FE methods. By using Reddy&rsquos third order shear deformation theory (TSDT) in association with the Hamilton&rsquos principle, the direct and derived quantities of the coupled system have been obtained. The coupled governing equations of METE plates have been derived through condensation technique. Three layered METE plates composed of piezoelectric and piezomagnetic phases are considered for evaluation. For investigating the correctness and accuracy, the results in this article are validated with previous researches. In addition, a special attention has been paid to evaluate the influence of different electro-magnetic boundary conditions and pyrocoupling on the coupled response of METE plates. Finally, the influence of stacking sequences, magnitude of temperature load and aspect ratio on the coupled static response of METE plates are investigated in detail.

Key Words
Reddy’s third order shear deformation theory; magneto-electro-elastic; temperature loading; pyrocoupling; open and closed circuit; static quantities

Address
M. Vinyas, D. Harursampath: Non-linear Multifunctional Composites Analysis and Design (NMCAD) Lab, Department of Aerospace Engineering,
Indian Institute of Science, Bangalore, 560012, India
S.C. Kattimani: Department of Mechanical Engineering, National Institute of Technology Karnataka, Surathkal, 575025, India

Abstract
The dynamic stability of a functionally graded polymer microbeam reinforced by graphene oxides subjected to a periodic axial force is investigated. The microbeam is assumed to rest on an elastic substrate and is subjected to various immovable boundary restraints. The weight fraction of graphene oxides nanofillers is graded across the beam thickness. The effective Young’s modulus of the functionally graded graphene oxides reinforced composite (FG-GORC) was determined using modified Halpin–Tsai model, with the mixture rule used to evaluate the effective Poisson\'s ratio and the mass density. An improved third order shear deformation theory (TSDT) is used in conjunction with the Chebyshev polynomial-based Ritz method to derive the Mathieu-Hill equations for dynamic stability of the FG-GORC microbeam, in which the scale effect is taken into account based on modified couple stress theory. Then, the Mathieu-Hill equation was solved using Bolotin’s method to predict the principle unstable regions of the FG-GORC microbeams. The numerical results show the effects of the small scale, the graphene oxides nanofillers as well as the elastic substrate on the dynamic stability behaviors of the FG-GORC microbeams.

Key Words
functionally graded microbeam; graphene oxide reinforced composites; dynamic stabilities; third order shear deformation theory; Chebyshev-Ritz method

Address
Yuewu Wang, Tairan Fu: Key Laboratory for Thermal Science and Power Engineering of Ministry of Education,
Beijing Key Laboratory of CO2 Utilization and Reduction Technology, Department of Energy and Power Engineering,
Tsinghua University, Beijing, China, 100084
Ke Xie: Institute of Systems Engineering, China Academy of Engineering Physics, Mianyang, Sichuan, China, 621900

Abstract
Force based design (FBD) approach is prevalent in most of the national seismic design codes world over. Direct displacement based design (DDBD) and energy based design (EBD) approaches are relatively new methods of seismic design which claims to be more rational and predictive than the FBD. These three design approaches are conceptually distinct and imparts different strength, stiffness and ductility property to structural members for same plan configuration. In present study behavioural assessment of frame of six storey RC building designed using FBD, DDBD and EBD approaches has been performed. Lateral storey forces distribution, reinforcement design and results of nonlinear performance using static and dynamic methods have been compared. For the three approaches, considerable difference in lateral storey forces distribution and reinforcement design has been observed. Nonlinear pushover analysis and time history analysis results show that in FBD frame plastic deformation is concentrated in the lower storey, in EBD frame large plastic deformation is concentrated in the middle storeys though the inelastic hinges are well distributed over the height and, in DDBD frame plastic deformation is approximately uniform over the height. Overall the six storey frame designed using DDBD approach seems to be more rational than the other two methods.

Key Words
force based design; direct displacement based design; energy based design; target drift; seismic behavior; nonlinear analysis

Address
Department of Applied Mechanics, Visvesvaraya National Institute of Technology,Nagpur 440010, Maharashtra, India

Abstract
The influence on flexural strength of Glass/Epoxy laminated composite curved panels of different geometries (cylindrical, spherical, elliptical, hyperboloid and flat) due to inclusion of nano cenosphere filler examined in this research article. The deflection responses of the hybrid structure are evaluated numerically using the isoparametric finite element technique and modelled mathematically via higher-order displacement structural kinematics. To predict the deflection values, a customised in-house computer code in MATLAB environment is prepared using the higher-order isoparametric formulation. Subsequently, the numerical model validity has been established by comparing with those of available benchmark solution including the convergence characteristics of the finite element solution. Further, a few cenosphere filled hybrid composite are prepared for different volume fractions for the experimental purpose, to review the propose model accuracy. The experimental deflection values are compared with the finite element solutions, where the experimental elastic properties are adopted for the computation. Finally, the effect of different variable design dependent parameter and the percentages of nano cenosphere including the geometrical shapes obtained via a set of numerical experimentation.

Key Words
experimental bending; hybrid composite; glass cenosphere; FEM, HSDT

Address
Harsh Kumar Pandey, Himanshu Agrawal, Subrata Kumar Panda,
Chetan Kumar Hirwani, Pankaj V. Katariya and Hukum Chand Dewangan
Harsh Kumar Pandey: Department of Mechanical Engineering, Dr. C.V. Raman Institute of Science & Technology, Bilaspur (C.G.), India
Himanshu Agrawal: Department of Mechanical Engineering, Government Engineering College, Jagdalpur, Chhattisgarh, India 494001
Subrata Kumar Panda, Hukum Chand Dewangan: Department of Mechanical Engineering, NIT Rourkela, Rourkela, Odisha, Sundergarh, India 769008
Chetan Kumar Hirwani: Department Mechanical Engineering, National Institute of Technology Patna, Bihar, India, 800005

Abstract
The present investigation deals with the thermomechanical interactions in an orthotropic thermoelastic homogeneous body in the context of fractional order theory of thermoelasticity due to time harmonic sources. The application of a time harmonic concentrated and distributed sources has been considered to show the utility of the solution obtained. Assuming the disturbances to be harmonically time dependent, the expressions for displacement components, stress components and temperature change are derived in frequency domain. Numerical inversion technique has been used to determine the results in physical domain. The effect of frequency on various components has been depicted through graphs.

Key Words
orthotropic medium; fractional calculus; frequency domain; fourier transform; concentrated and uniformly distributed loads

Address
Department of Basic and Applied Sciences, Punjabi University Patiala, Punjab, India


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