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CONTENTS
Volume 52, Number 3, November10 2014
 

Abstract
In this paper a new particle swarm ray optimization algorithm is proposed for truss shape and size optimization with natural frequency constraints. These problems are believed to represent nonlinear and non-convex search spaces with several local optima and therefore are suitable for examining the capabilities of new algorithms. The proposed algorithm can be viewed as a hybridization of Particle Swarm Optimization (PSO) and the recently proposed Ray Optimization (RO) algorithms. In fact the exploration capabilities of the PSO are tried to be promoted using some concepts of the RO. Five numerical examples are examined in order to inspect the viability of the proposed algorithm. The results are compared with those of the PSO and some other existing algorithms. It is shown that the proposed algorithm obtains lighter structures in comparison to other methods most of the time. As will be discussed, the algorithm\'s performance can be attributed to its appropriate exploration/exploitation balance.

Key Words
optimal design of truss structures; ray optimization; particle swarm optimization; PSRO; frequency constraints

Address
A. Kaveh and A. Zolghadr: Centre of Excellence for Fundamental Studies in Structural Engineering, School of Civil Engineering, Iran University of Science and Technology, Narmak, Tehran-16, Iran

Abstract
In an indentation approach, the smooth rigid spherical ball penetrated into a deformable flat is considered for the study based on contact mechanics approach. The elastic-plastic frictionless spherical indentation analysis has been under taken in the finite element analysis using „ABAQUS‟ and experimental study. The spherical indentation has been studied for the materials like steel, aluminium, copper and brass with an identical spherical indenter for diverse indentation depths. The springback analysis is executed for studying the actual indentation depth after the indenter is unloaded. In the springback simulation, the material recovers its elastic deformation after the indenter is unloaded. The residual diameter and depth of an indentation for various materials are measured and compared with simulation results. It shows a good agreement between the simulation and an experimental studies.

Key Words
indentation; elastic-plastic; depth of indentation; springback analysis; indentation diameter; contact mechanics

Address
V. C. Sathish Gandhi: Department of Mechanical Engineering, University College of Engineering Ariyalur, (A constituent College of Anna University, Chennai), Ariyalur - 621 704, Tamilnadu, India
R. Kumaravelan: Department of Mechanical Engineering, Velalar College of Engineering and Technology, Erode - 638 012, Tamilnadu, India
S. Ramesh: Department of Mechanical Engineering, Vel Tech High Tech Dr. Rangarajan Dr. Sakunthala Engineering College, Chennai - 600 062, Tamilnadu, India

Abstract
This study aimed to develop an approach to accurately predict the wind models and wind effects of large wind turbines. The wind-induced vibration characteristics of a 5 MW tower-blade coupled wind turbine system have been investigated in this paper. First, the blade-tower integration model was established, which included blades, nacelle, tower and the base of the wind turbine system. The harmonic superposition method and modified blade element momentum theory were then applied to simulate the fluctuating wind field for the rotor blades and tower. Finally, wind-induced responses and equivalent static wind loads (ESWL) of the system were studied based on the modified consistent coupling method, which took into account coupling effects of resonant modes, cross terms of resonant and background responses. Furthermore, useful suggestions were proposed to instruct the wind resistance design of large wind turbines. Based on obtained results, it is shown from the obtained results that wind-induced responses and ESWL were characterized with complicated modal responses, multi-mode coupling effects, and multiple equivalent objectives. Compared with the background component, the resonant component made more contribution to wind-induced responses and equivalent static wind loads at the middle-upper part of the tower and blades, and cross terms between background and resonant components affected the total fluctuation responses, while the background responses were similar with the resonant responses at the bottom of tower.

Key Words
large wind turbine system; fluctuating wind field; modified blade element momentum theory; wind-induced response; equivalent static wind load

Address
S.T. Ke, T.G. Wang: Jiangsu Key Laboratory of Hi-Tech Research for Wind Turbine Design, Nanjing University of Aeronautics and Astronautics, 29 Yudao Road, Nanjing 210016, China
Y.J. Ge: State Key Laboratory for Disaster Reduction in Civil Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China
Y. Tamura: Center of Wind Engineering Research, Tokyo Polytechnic University, 1583 Iiyama, Atsugi, Kanagawa 243-0297, Japan

Abstract
Shell foundations have been employed as an alternative for the conventional flat shallow foundations and have proven to provide economical advantage. They have shown considerably improved performance in terms of ultimate capacity and settlement characteristics. However, despite conical shell foundations are frequently used in industry, the theoretical solutions for bearing capacity of these footings are available for only triangular shell strip foundations. The benefits in design aspects can be achieved through theoretical solutions considering shell geometry. The engineering behavior of a conical shell foundation on mixed soils was investigated experimentally and theoretically in this study. The failure mechanism was obtained by conducting laboratory model tests. Based on that, the theoretical solution of bearing capacity was developed and validated with experimental results, in terms of the internal angle of the cone. In comparison to the circular flat foundation, the results show 15% increase of ultimate load and 51% decrease of settlement at an angle of intersection of 120

Key Words
shell foundation; ultimate bearing capacity; theoretical solution

Address
J.E. Colmenares: Department of Civil and Agricultural Engineering, Universidad Nacional de Colombia, Bogota, Colombia
So-Ra Kang: Development & Planning Department, Midas IT, Kyoungki-do, Korea
Young-Jin Shin: DTS T-01 Project, Samsung Construction and Trading Corporation, Abu Dhabi, UAE
Jong-Ho Shin: Department of Civil Engineering, Konkuk University, Seoul, Korea

Abstract
The Lyapunov exponent and moment Lyapunov exponents of Hill\' s equation with frequency and damping coefficient fluctuated by correlated wideband random processes are studied in this paper. The method of stochastic averaging, both the first-order and the second-order, is applied. The averaged Itô differential equation governing the pth norm is established and the pth moment Lyapunov exponents and Lyapunov exponent are then obtained. This method is applied to the study of the almost-sure and the moment stability of the stationary solution of the thin simply supported beam subjected to time-varying axial compressions and damping which are small intensity correlated stochastic excitations. The validity of the approximate results is checked by the numerical Monte Carlo simulation method for this stochastic system.

Key Words
elastic beam; eigenvalues; stochastic averaging; stochastic stability; Monte Carlo method

Address
Goran Janevski, Predrag Kozic and Ivan Pavlovic: Department of Mechanical Engineering, University of Nis, A. Medvedeva 14, 18000 Nis, Serbia

Abstract
A 1/4-scale two-bay eight-storey reinforced concrete frame was tested on shaking table. Initial shaking table tests were carried out through a set of real seismic excitations to investigate the seismic behavior of the RC frame. Subsequently, the damaged frame was repaired using epoxy injection technique, and then subjected to the tests with the same records. The purpose of this study was to investigate experimentally the dynamic characteristics, cracking pattern and lateral inter-story stiffness of RC frames using epoxy injection technique. The test results indicate that epoxy-injection technique appears to be a satisfactory method for repairing earthquake-damaged structure.

Key Words
reinforced concrete frame; shaking table test; epoxy injection technique; dynamic characteristic; wedge splitting test

Address
Jiangtao Yu, Yuanmiao Zhang and Zhoudao Lu: Research Institute of Structural Engineering and Disaster Reduction, Tongji University, Shanghai, China

Abstract
This paper presents the results of an experimental investigation on the flexural behavior of doubly reinforced lightweight concrete (R.L.C.) beams tested under cyclic loading. A total of 20 beam specimens were tested. Test results are presented in terms of ductility index, the degradation of strength and stiffness, and energy dissipation. The flexural properties of R.L.C. beam were compared to those of normal concrete (R.C.) beams. Test results show that R.L.C. beam with low and medium concrete strength (20, 40MPa) performed displacement ductility similar to the R.C. beam. The ductility can be improved by enhancing the concrete strength or decreasing the tension reinforcement ratio. Using lightweight aggregate in concrete is advantageous to the dynamic stiffness of R.L.C. beam. Enhancement of concrete strength and increase of reinforcement ratio will lead to increase of the stiffness degradation of beam. The energy dissipation of R.L.C beam, similar to R.C. beam, increase with the increase of tension reinforcement ratio. The energy dissipation of unit load cycle for smaller tension reinforcement ratio is relatively less than that of beam with higher reinforcement ratio.

Key Words
reinforced concrete; lightweight aggregate; cyclic loading; ductility; stiffness; energy dissipation

Address
Li-Kai Chien: Department of Earth Sciences and Institute of Geophysics, National Central University, Taiwan
Yi-Hao Kuo: Department of Civil Engineering, National Chung-Hsing University, Taiwan
Chung-Ho Huang: Department of Civil Engineering, National Taipei University of Technology, Taiwan
How-Ji Chen: Department of Civil Engineering, National Chung-Hsing University, Taiwan
Ping-Hu Cheng: Department of Earth Sciences and Institute of Geophysics, National Central University, Taiwan

Abstract
Pounding between adjacent buildings is a significant challenge in metropolitan areas because buildings of different heights collide during earthquake excitations due to varying dynamic properties and narrow separation gaps. The seismic responses of adjacent buildings of varying height, coupled through soil subjected to earthquake-induced pounding, are evaluated in this paper. The lumped mass model is used to simulate the buildings and soil, while the linear visco-elastic contact force model is used to simulate pounding forces. The results indicate while the taller building is almost unaffected when the shorter building is very short, it suffers more from pounding with increasing height of the shorter building. The shorter building suffers more from the pounding with decreasing height and when its height differs substantially from that of the taller building. The minimum required separation gap to prevent pounding is increased with increasing height of the shorter building until the buildings become almost in-phase. Considering the soil effect; pounding forces are reduced, displacements and story shears are increased after pounding, and also, minimum separation gap required to prevent pounding is increased.

Key Words
pounding; adjacent buildings; tall building; short building; separation gap; seismic response; Fixed-Based (FB); Structure-Soil-Structure Interaction (SSSI)

Address
Sadegh Naserkhaki: Department of Civil and Environmental Engineering, Faculty of Engineering, University of Alberta, Edmonton, Canada; Department of Civil Engineering, Faculty of Engineering, Universiti Putra Malaysia, Serdang, Malaysia
Marwan El-Rich: Department of Civil and Environmental Engineering, Faculty of Engineering, University of Alberta, Edmonton, Canada
Farah N.A. Abdul Aziz: Department of Civil Engineering, Faculty of Engineering, Universiti Putra Malaysia, Serdang, Malaysia
Hassan Pourmohammad: Department of Civil Engineering, Faculty of Engineering, Islamic Azad University, Karaj Branch, Karaj, Iran

Abstract
For analysis of the plates and membranes by numerical or analytical methods, the question of choice of the system of functions satisfying the different boundary conditions remains a major challenge to address. It is to this issue that is dedicated this work based on an approach of choice of combinations of trigonometric functions, which are shape functions of a bended beam with the boundary conditions corresponding to the plate support mode. To do this, the shape functions of beam vibrations for strength analysis of the rectangular plates by Kantorovich-Vlasov\'s method is considered.Using the properties of quasi-orthogonality of those functions allowed assessing to differential equation for every member of the series. Therefore it\'s proposed some new forms of integration of the beam functions, in order to simplify the problem.

Key Words
shape functions ; beam vibrations ; beam functions ; Kantorovich-Vlasov\'s method

Address
Emmanuel E.T. Olodo and Gerard Degan: Laboratory of Applied Mechanics and Energetic (LEMA), University of Abomey-Calavi, Benin

Abstract
A series of experimental work is carried out with the aim to understand the flexural performance of laminated glass (LG) beams using polyvinyl butyral (PVB) and Ionoplast interlayers subjected to short term duration loads in the circumstance of elevated temperature. The study is based on a total of 42 laboratory tests conducted in ambient temperature ranging from 25oC to 80oC. The load duration is kept within 20 seconds. Through the tests, load-stress and load-deflection curves of the LG are established; appropriate analytical models for the LG are indentified; the effective thicknesses as well as the shear transfer coefficients of the LG are semi-empirically determined. The test results show that within the studied temperature range the bending stresses and deflections at mid-span of the LG develop linearly with respect to the applied loads. From 25oC to 80oC the flexural behavior of the PVB LG is found constantly between that of monolithic glass and layered glass having the same nominal thickness; the flexural behavior of the Ionoplast LG is equivalent to monolithic glass of the same nominal thickness until the temperature elevates up to 50oC. The test results reveal that in calculating the effective thicknesses of the PVB and Ionoplast LG, neglecting the shear capacities of the interlayers is uneconomic even when the ambient temperature is as high as 80oC. In the particular case of this study, the shear transfer coefficient of the PVB interlayer is found in a range from 0.62 to 0.14 while that of the Ionoplast interlayer is found in a range from 1.00 to 0.56 when the ambient temperature varies from 25oC to 80oC.

Key Words
polyvinyl butyral laminated glass; Ionoplast laminated glass; temperature; flexural performance; short duration load

Address
Xiaokun Huang, Gang Liu, Qiang Liu: China Academy of Building Research, Beijing, China
Stephen J. Bennison: E.I. DuPont de Nemours & Co. Inc., USA

Abstract
In the early design stage of ships, the two most important structural analyses are performed to identify the structural capacity and safety. The first step is called global strength analysis (longitudinal strength analysis or hull girder strength analysis) and the second step is local buckling analysis (stiffened panel strength analysis). This paper deals with the ultimate strength performance of Arctic sea route-going commercial ships considering the effect of low temperature. In this study, two types of structural analyses are performed in Arctic sea conditions. Three types of ship namely oil tanker, bulk carrier and container ship with four different sizes (in total 12 vessels) are tested in four low temperatures (−20, −40, −60 and −80oC), which are based on the Arctic environment and room temperature (20oC). The ultimate strength performance is analysed with ALPS/HULL progressive hull collapse analysis code for ship hulls, then ALPS/ULSAP supersize finite element method for stiffened panels. The obtained results are summarised in terms of temperature, vessel type, vessel size, loading type and other effects. The important insights and outcomes are documented.

Key Words
ultimate strength performance; Arctic; northern sea routes; oil tankers; bulk carriers; container ships

Address
Dae Kyeom Park, Jeom Kee Paik, Bong Ju Kim, Jung Kwan Seo,
Chen Guang Li: Korea ship and Offshore Research Institute (The Lloyd

Abstract
A semi-analytical numerical approach for the effective structural dynamic response analysis of spar floating substructure for offshore wind turbine subject to wave-induced excitation is introduced in this paper. The wave-induced rigid body motions at the center of mass are analytically solved using the dynamic equations of rigid ship motion. After that, the flexible structural dynamic responses of spar floating substructure for offshore wind turbine are numerically analyzed by letting the analytically derived rigid body motions be the external dynamic loading. Restricted to one-dimensional sinusoidal wave excitation at sea state 3, pitch and heave motions are considered. Through the numerical experiments, the time responses of heave and pitch motions are solved and the wave-induced dynamic displacement and effective stress of flexible floating substructure are investigated. The hydrodynamic interaction between wave and structure is modeled by means of added mass and wave damping, and its modeling accuracy is verified from the comparison of natural frequencies obtained by experiment with a 1/100 scale model.

Key Words
spar floating substructure; wave-induced excitation; pitch and heave motions; flexible structural dynamic responses; semi-analytical numerical approach

Address
Jin-Rae Cho, Bo-Sung Kim, Eun-Ho Choi, Shi-Bok Lee and O-Kaung Lim: School of Mechanical Engineering, Pusan National University, Busan 609-735, Korea


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