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CONTENTS
Volume 51, Number 5, September10 2014
 

Abstract
In order to improve the crane-hook\'s performance and service life, we formulate a multi-criteria shape design problem considering practical conditions. The structural weight, the displacement at specified points and the induced matrix norm of stiffness matrix are adopted as the evaluation items to be minimized. The heights and widths of cross-section are chosen as the design variables. The design variables are expressed in terms of shape functions based on the Gaussian function. For this multi-objective optimization problem with three items, we utilize a multi-objective evolutionary algorithm, that is, the multi-objective Particle Swarm Optimization (MOPSO). As a common feature of obtained solutions, the side views are tapered shapes similar to those of actual crane-hook designs. The evaluation item values of the obtained designs demonstrate importance of the present optimization as well as the feasibility of the proposed optimal design approach.

Key Words
optimal design; crane-hook; finite element method; Gaussian; MOPSO

Address
Takao Muromaki : Mechanical Engineering, Maizuru National College of Technology, 234 Siroya, Maizuru, Kyoto, 625-8511, Japan
Kazuyuki Hanahara and Yukio Tada : Graduate School of System Informatics, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501, Japan

Abstract
The functionally graded beam (FGB) is investigated in this study on both dynamic and static loading in case of resting on a soil medium rather than on the usual Winkler-Pasternak elastic foundation. The powerful ABAQUS software was used to model the problem applying finite element method. In the present study, two different soil models are taken into account. In the first model, the soil is assumed to be an elastic plane stress medium. In the second soil model, the Drucker-Prager yield criterion, which is one of the most well-known elastic-perfectly plastic constitutive models, is used for modelling the soil medium. The results are shown to evaluate the effects of the different soil models, stiffness values of the elastic soil medium on the normal and shear stress and free vibration properties. A comparison was made to those from the existing literature. Numerical results show that considering real soil as a continuum space affects the results of the bending and the modal properties significantly.

Key Words
functionally graded materials; beams; ABAQUS; Winkler-Pasternak; foundation; FEM; composite

Address
Amin Chegenizadeh, Behzad Ghadimi, Hamid Nikraz : Department of Civil Engineering, Curtin University, Perth, Australia
Mesut Simsek : Department of Civil Engineering, Yildiz Technical University, Turkey

Abstract
Investigations of regular and chaotic vibrations of the autoparametric pendulum absorber suspended on a nonlinear coil spring and a magnetorheological damper are presented in the paper. Application of a semi-active damper allows controlling the dangerous motion without stooping of system and additionally gives new possibilities for designers. The investigations are curried out close to the main parametric resonance. Obtained numerical and experimental results show that the semi-active suspension may reduce dangerous motion and it also allows to maintain the pendulum at a given attractor or to jump to another one. Moreover, the results show that, for some parameters, MR damping may transit to chaotic motions.

Key Words
chaos; bifurcation; MR damping; control; attractor

Address
Krzysztof Kecik : Department of Applied Mechanics, Lublin University of Technology, Nadbystrzycka 36 St., Lublin 20-618, Poland

Abstract
Environmental changes, especially global climate change, are creating new challenges to the development of the Arctic regions, which have substantial energy resources. And attention to offshore structures has increased with oil and gas development. The structural impact response of an explosion-resistant profiled blast walls normally changes when it operates in low temperatures. The main objectives of this study are to investigate the structural response of blast walls in low temperature and suggest useful guidelines for understanding the characteristics of the structural impact response of blast walls subjected to hydrocarbon explosions in Arctic conditions. The target temperatures were based on the average summer temperature (−20\'C), the average winter temperature (−40\'C) and the coldest temperature recorded (approximately −68\'C) in the Arctic. The nonlinear finite element analysis was performed to design an explosion-resistant profiled blast wall for use in Arctic conditions based on the behaviour of material properties at low temperatures established by performing a tensile test. The conclusions and implications of the findings are discussed.

Key Words
offshore structures; arctic conditions; structural impact response characteristics; blast walls; nonlinear finite element analysis

Address
Jung Min Sohn, Sang Jin Kim, Dong Jin Seong, Bong Ju Kim,Yeon Chul Ha, Jung Kwan Seo and Jeom Kee Paik : The Korea Ship and Offshore Research Institute (The Lloyd\'s Register Foundation Research Centre of Excellence), Pusan National University, Busan, Korea

Abstract
In this paper, we study the inverse mode shape problem for an Euler-Bernoulli beam, using an analytical approach. The mass and stiffness variations are determined for a beam, having various boundary conditions, which has a prescribed polynomial second mode shape with an internal node. It is found that physically feasible rectangular cross-section beams which satisfy the inverse problem exist for a variety of boundary conditions. The effect of the location of the internal node on the mass and stiffness variations and on the deflection of the beam is studied. The derived functions are used to verify the p-version finite element code, for the cantilever boundary condition. The paper also presents the bounds on the location of the internal node, for a valid mass and stiffness variation, for any given boundary condition. The derived property variations, corresponding to a given mode shape and boundary condition, also provides a simple closed-form solution for a class of non-uniform Euler-Bernoulli beams. These closed-form solutions can also be used to check optimization algorithms proposed for modal tailoring.

Key Words
Euler-Bernoulli beam; free vibration; modal tailoring; inverse problem; closed-form solution

Address
Korak Sarkar and Ranjan Ganguli : Department of Aerospace Engineering, Indian Institute of Science, Bangalore-560012, India

Abstract
The goal of this study is to evaluate and design steel plates with optimal material distributions achieved through a specific material topology optimization by using a CCARAT (Computer Aided Research Analysis Tool) as an optimizer, topologically optimally updating node densities as design variables. In typical material topology optimization, optimal topology and layouts are described by distributing element densities (from almost 0 to 1), which are arithmetic means of node densities. The average element densities are employed as material properties of each element in finite element analysis. CCARAT may deal with material topology optimization to address the mean compliance problem of structural mechanical problems. This consists of three computational steps: finite element analysis, sensitivity analysis, and optimality criteria optimizer updating node densities. The present node density based design via CCARAT using node densities as design variables removes jagged optimal layouts and checkerboard patterns, which are disadvantages of classical material topology optimization using element densities as design variables. Numerical applications that topologically optimize reinforcement material distribution of steel plates of a cantilever type are studied to verify the numerical superiority of the present node density based design via CCARAT.

Key Words
node density based design; material topology optimization; CCARAT; node densities; steel plate; reinforcement

Address
Dongkyu Lee : Department of Architectural Engineering, Sejong University, Seoul, 143-747, Korea
Soomi Shin : Research Institute of Industrial Technology, Pusan National University, Busan, 609-735, Korea
Hyunjung Park : Division of Architecture, Silla University, Busan, 617-736, Korea
Sungsoo Park : Department of Architectural Engineering, Pusan National University, Busan, 609-735, Korea

Abstract
The truss based steel bridge structures usually consists of gusset plates which lose their load carrying capacity and rigidity under the effect of repeated and dynamics loads. This paper is focused on modeling the nonlinear material behavior of the gusset plates of the Truss Based Bridges subjected to dynamics loads. The nonlinear behavior of material is characterized by a damage coupled elsto-plastic material models. A truss bridge finite element model is established in Abaqus with the details of the gusset plates and their connections. The nonlinear finite element analyses are performed to calculate stress and strain states in the gusset plates under different loading conditions. The study indicates that damage initiation occurred in the plastic deformation localized region of the gusset plates where all, diagonal, horizontal and vertical, truss member met and are critical for shear type of failure due tension and compression interaction. These findings are agreed with the analytical and experimental results obtained for the stress distribution of this kind gusset plate.

Key Words
truss based steel bridges; gusset plate; dynamic analysis of bridges; nonlinear modeling

Address
Babur Deliktas and Akhaan Mizamkhan : Department of Civil Engineering, Uludag University, Gorukle, BURSA, 16069, Turkey

Abstract
Success in the excavation of foundations is commonly known as being very important in asserting stability. Furthermore, when the subjected formation is rocky and the use of explores is required, the demands of successful blasting are multiplied. The quick and correct estimation of xcavation\'s characteristics may help the design of building structures, increasing their safety. The present paper proposes a new classification system which connects blastability and rock mass quality. This new system primarily concerns poor and friable rock mass, heavily broken with mixture of angular and rounded rock pieces. However, it should concern medium and good quality rock mass. The Blastability Quality System (BQS) can be an easy and widely - used tool as it is a quick calculator for blastability index (BI) and rock mass quality. Taking into account the research calculations and the parameters of BQS, what has been at question in this paper is the effect of BI magnitude on a geological structure.

Key Words
excavation; blast ability; rock mass; quality; classification; explosion; methodology

Address
B. Christaras and M. Chatziangelou : Department of Geology, Aristotle University of Thessaloniki, 546 31, Greece

Abstract
This paper describes a formulation to predict optimum post-tensioning forces and cable dimensioning for self-anchored cable-stayed suspension bridges. The analysis is developed with respect to both dead and live load configurations, taking into account design constrains concerning serviceability and ultimate limit states. In particular, under dead loads, the analysis is developed with the purpose to calculate the post-tensioning cable forces to achieve minimum deflections for both girder and pylons. Moreover, under live loads, for each cable elements, the lowest required cross-section area is determined, which verifies prescriptions, under ultimate or serviceability limit states, on maximum allowable stresses and bridge deflections. The final configuration is obtained by means of an iterative procedure, which leads to a progressive definition of the stay, hanger and main cable characteristics, concerning both post-tensioning cable stresses and cross-sections. The design procedure is developed in the framework of a FE modeling, by using a refined formulation of the bridge components, taking into account of geometric nonlinearities involved in the bridge components. The results demonstrate that the proposed method can be easily utilized to predict the cable dimensioning also in the framework of long span bridge structures, in which typically more complexities are expected in view of the large number of variables involved in the design analysis.

Key Words
long span bridges/structures; numerical methods; structural design; finite element method (FEM); post-tension

Address
Paolo Lonetti and Arturo Pascuzzo : Department of Civil Engineering, University of Calabria, Via P. Bucci, 87030, Rende, Cosenza, Italy

Abstract
An equivalent single layer trigonometric shear deformation theory taking into account transverse shear deformation effect as well as transverse normal strain effect is presented for static flexure of cross-ply laminated composite and sandwich plates. The inplane displacement field uses sinusoidal function in terms of thickness coordinate to include the transverse shear deformation effect. The cosine function in thickness coordinate is used in transverse displacement to include the effect of transverse normal strain. The kinematics of the present theory is much richer than those of the other higher order shear deformation theories, because if the trigonometric term (involving thickness coordinate z) is expanded in power series, the kinematics of higher order theories (which are usually obtained by power series in thickness coordinate z) are implicitly taken into account to good deal of extent. Governing equations and boundary conditions of the theory are obtained using the principle of virtual work. The closed-form solutions of simply supported cross-ply laminated composite and sandwich plates have been obtained. The results of present theory are compared with those of the classical plate theory (CPT), first order shear deformation theory (FSDT), higher order shear deformation theory (HSDT) of Reddy and exact three dimensional elasticity theory wherever applicable. The results predicted by present theory are in good agreement with those of higher order shear deformation theory and the elasticity theory.

Key Words
shear deformation; transverse normal strain; static flexure; cross-ply laminated plate; sandwich plate; transverse shear stress

Address
Atteshamuddin S. Sayyad : Department of Civil Engineering, SRES\'s College of Engineering, University of Pune, Kopargaon-423601, (Maharashtra State), India
Yuwaraj M. Ghugal : Department of Applied Mechanics, Government Engineering College, Karad-415124, Maharashtra State, India


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