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CONTENTS
Volume 48, Number 4, November25 2013
 

Abstract
A new computational approach for the rain load on the transmission tower is presented to obtain the responses of system subjected to the wind and rain combined excitations. First of all, according to the similarity theory, the aeroelastic modeling of high-voltage transmission tower is introduced and two kinds of typical aeroelastic models of transmission towers are manufactured for the wind tunnel tests, which are the antelope horn tower and pole tower. And then, a formula for the pressure time history of rain loads on the tower structure is put forward. The dynamic response analyses and experiments for the two kinds of models are carried out under the wind-induced and wind-rain-induced actions with the uniform and turbulent flow. It has been shown that the results of wind-rain-induced responses are bigger than those of only wind-induced responses and the rain load influence on the transmission tower can‟t be neglected during the strong rainstorm. The results calculated by the proposed method have a good agreement with those by the wind tunnel test. In addition, the wind-rain-induced responses along and across the wind direction are in the same order of response magnitude of towers.

Key Words
high-voltage transmission tower; rain load; aeroelastic model; wind-rain excitation; wind tunnel test

Address
Hong-Nan Li, Shun-Yong Tang and Ting-Hua Yi : Faculty of Infrastructure Engineering, Dalian University of Technology, Dalian 116023, P.R. China
Shun-Yong Tang : China United Engineering Corporation, Hangzhou 310022, P.R. China

Abstract
In recent years, many countries have added railway noise to the issues covered by noise regulations. It is known that the rail is the dominant source of rolling noise at frequency range of 500Hz - 2000Hz for the conventional speeds (<160km/h). One of the effective ways to reduce noise from railway track is using a rail vibration absorber. To study the acoustic performance of rail absorber, the decay rates of vibration have long been used by researcher. In this paper, A FE model of a periodic supported rail with infinite element in ABAQUS is developed to study the acoustic performance of the rail absorber. To compute the decay rates, acceleration responses along the rail transferred to MATLAB to obtain response levels in frequency domain and then by processing the response levels, the decay rates obtained for each1/3octav band. Continous rail absorber is represented by a steel layer and an elastomer layer. The decay rates for conventional rail and rail with one-side absorber and also, the rail with two side absorber are obtained and compared. Then, to improve the system of rail absorber, a steel plate with elastomer layer is added to bottom of the rail foot. The vertical decay rate results show that the decay rate of rail vibration along the track is significantly increased around the tuned frequency of the absorber and thus the rail vibration energy is substantially reduced in the corresponding frequency region and also effective in rail noise reduction.

Key Words
continous rail absorber; decay rate; FEM;ABAQUS; noise; UIC60

Address
Habibollah Molatefi and Soroush Izadbakhsh : Railway Engineering School, Iran University of Science and Technology, Tehran, Iran

Abstract
Municipalities in the United Arab Emirates approve reinforced concrete design of building structures to follow either the ACI 318 or the BS 8110 code. Since the requirements of these codes are different from each, there is a need to compare the structural demand in the two codes. The main objective of this study is to compare the design requirements of the ACI 318 code with the BS 8110 code for the flexural, shear and axial compression limit states. The load factors and load combinations in the two codes are also compared. To do so, a large number of cross-sections with different geometries, material properties, and reinforcement ratios are analyzed following the procedures in the two codes. The relevant factored load combinations in the two codes are also investigated for a wide range of live-to-dead load ratios and for various wind-to-dead load ratios. The study showed that the differences between the design capacities in the ACI 318 and BS 8110 codes are minor for flexure, moderate for axial compression, and major for shear. Furthermore, the factored load combinations for dead load, live load and wind in the two codes yield minorto- moderate differences, depending on the live-to-dead load ratio and intensity of wind.

Key Words
axial compression; code; concrete; flexure; reinforced concrete; shear; specification; standard; structural design

Address
Sami W. Tabsh : Department of Civil Engineering, American University of Sharjah, P.O. Box 26666, Sharjah, UAE

Abstract
This paper presents the experimental as well as analytical study conducted on layer-bonded scrap tire rubber pad (STRP) isolators to develop low-cost seismic isolators applicable to structures in developing countries. The STRP specimen samples were produced by stacking the STRP layers one on top of another with the application of adhesive. In unbonded application, the STRP bearings were placed between the substructure and superstructure without fastening between the contact surfaces which allows roll-off of the contact supports. The vertical compression and horizontal shear tests were conducted with varying axial loads. These results were used to compute the different mechanical properties of the STRP isolators including vertical stiffness, horizontal effective stiffness, average horizontal stiffness and effective damping ratios. The load-displacement relationships of STRP isolators obtained by experimental and finite element analysis results were found to be in close agreement. The tested STRP samples show energy dissipation capacity considerably greater than the natural rubber bearings. The layer-bonded STRP isolators serve positive incremental force resisting capacity up to the shear strain level of 150%.

Key Words
layer bonded STRP; compression test; cyclic shear test; FE analysis, low-cost base isolation

Address
Huma Kanta Mishra : Department of Urban Management, Kyoto University, Japan
Akira Igarashi : Department of Civil and Earth Resources Engineering, Kyoto University, Japan

Abstract
Apart from thinning of cortical layers, the local bone curvature, varying along bone periphery, modulates ultrasound waves as well, which is however often underestimated or overlooked in clinical quantitative ultrasound (QUS). A dedicated three-dimensional finite element modelling technique for cortical bones was established, for quantitatively exploring and calibrating the effect of local curvature of cortical bone on ultrasound. Using a correlation-based mode extraction technique, high-velocity group (HVG) and low-velocity group (LVG) wave modes in a human radius were examined. Experimental verification using acrylic cylinders and in vitro testing using a porcine femur were accomplished. Results coherently unravelled the cortical curvature exerts evident influence on bone-guided ultrasound when RoC/n<1 for HVG mode and RoC/n<2 for LVG mode (RoC/n: the ratio of local bone curvature radius to wavelength); the sensitivity of LVG mode to bone curvature is higher than HVG mode. It has also been demonstrated the local group velocity of an HVG or LVG mode at a particular skeletal site is equivalent to the velocity when propagating in a uniform cylinder having an outer radius identical to the radius of curvature at that site. This study provides a rule of thumb to compensate for the effect of bone curvature in QUS.

Key Words
local bone curvature; cortical bone; bone modelling; quantitative ultrasound (QUS); highvelocity group wave; low-velocity group wave; in vitro testing

Address
Jiangang Chen, Zhongqing Su, Li Cheng : The Department of Mechanical Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong
Jiangang Chen : The Ultrasound and Elasticity Imaging Laboratory, Department of Biomedical Engineering,
Columbia University, New York, NY, USA
De-an Ta : The Department of Electronic Engineering, Fudan University, Shanghai, P.R. China

Abstract
An outline of the Timoshenko beam theory is presented. Two differential equations of motion in terms of deflection and rotation are comprised into single equation with deflection and analytical solutions of natural vibrations for different boundary conditions are given. Double frequency phenomenon for simply supported beam is investigated. The Timoshenko beam theory is modified by decomposition of total deflection into pure bending deflection and shear deflection, and total rotation into bending rotation and axial shear angle. The governing equations are condensed into two independent equations of motion, one for flexural and another for axial shear vibrations. Flexural vibrations of a simply supported, clamped and free beam are analysed by both theories and the same natural frequencies are obtained. That fact is proved in an analytical way. Axial shear vibrations are analogous to stretching vibrations on an axial elastic support, resulting in an additional response spectrum, as a novelty. Relationship between parameters in beam response functions of all type of vibrations is analysed.

Key Words
Timoshenko beam theory; flexural vibration; axial shear vibration; vibration parameter; analytical solution; double frequency phenomenon

Address
Ivo Senjanović and Nikola Vladimir : Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb, Ivana Lučića 5, 10000 Zagreb, Croatia

Abstract
Nonlinear behavior of functionally graded material (FGM) plates under thermal loads is investigated here using an efficient sinusoidal shear deformation theory. The displacement field is chosen based on assumptions that the in-plane and transverse displacements consist of bending and shear components, and the shear components of in-plane displacements give rise to the sinusoidal distribution of transverse shear stress through the thickness in such a way that shear stresses vanish on the plate surfaces. Therefore, there is no need to use shear correction factor. Unlike the conventional sinusoidal shear deformation theory, the proposed efficient sinusoidal shear deformation theory contains only four unknowns. The material is graded in the thickness direction and a simple power law based on the rule of mixture is used to estimate the effective material properties. The neutral surface position for such FGM plates is determined and the sinusoidal shear deformation theory based on exact neutral surface position is employed here. There is no stretching–bending coupling effect in the neutral surface-based formulation, and consequently, the governing equations and boundary conditions of functionally graded plates based on neutral surface have the simple forms as those of isotropic plates. The non-linear strain–displacement relations are also taken into consideration. The thermal loads are assumed as uniform, linear and non-linear temperature rises across the thickness direction. Closed-form solutions are presented to calculate the critical buckling temperature, which are useful for engineers in design. Numerical results are presented for the present efficient sinusoidal shear deformation theory, demonstrating its importance and accuracy in comparison to other theories.

Key Words
functional composites; thermal properties; buckling; plate theory; neutral surface position

Address
Rabbab Bachir Bouiadjra : Faculte d\'Architecture & de Genie Civil, Departement de Genie Civil, Universite Sciences et de la Technologie d\'Oran, Algeria; Laboratoire des Materiaux et Hydrologie, Faculte de Technologie, Universite de Sidi Bel Abbes, Algeria
E.A. Adda Bedia: Laboratoire des Materiaux et Hydrologie, Faculte de Technologie, Universite de Sidi Bel Abbes, Algeria
Abdelouahed Tounsi: Laboratoire des Materiaux et Hydrologie, Faculte de Technologie, Universite de Sidi Bel Abbes, Algeria; Laboratoire des Structures et Materiaux Avances dans le Genie Civil et Travaux Publics, Universite de Sidi Bel Abbes, Faculté de Technologie, Departement de Génie Civil, Algeria

Abstract
The use of the rigid polyurethane foam (RPF) to strengthen sandwich structures against blast terror has great interests from engineering experts in structural retrofitting. The aim of this study is to use the RPF to strengthen sandwich steel structure under blast load. The sandwich steel structure is assembled to study the RPF as structural retrofitting. The filed blast test is conducted. The finite element analysis (FEA) is also used to model the sandwich steel structure under shock wave. The sandwich steel structure performance is studied based on detonating different TNT explosive charges. There is a good agreement between the results obtained by both the field blast test and the numerical model. The RPF improves the sandwich steel structure performance under the blast wave propagation.

Key Words
displacements; field blast test; finite element analysis; blast wave; sandwich steel structure; TNT explosive charge

Address
Sherif A. Mazek : Civil Engineering Department, Military Technical College, Kobbry El-Kobba, Khlifa El-Maamoon, Cairo, Egypt
Ashraf A. Mostafa : Egyptian Engineering Department, Cairo, Egypt


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