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


was
 
CONTENTS
Volume 29, Number 5, November 2019
 

Abstract
Due to the rugged terrain, metro lines in mountain city across numerous wide rivers and deep valleys, resulting in instability of high-pier bridge and insecurity of metro train under crosswind. Compared with the conditions of no-wind, crosswind triggers severer vibration of the dynamic system; compared with the short-pier viaduct, the high-pier viaduct has worse stability under crosswind. For these reasons, the running safety of the metro vehicle traveling on a high-pier viaduct under crosswind is analyzed to ensure the safe operation in metro lines in mountain cities. In this paper, a dynamic model of the metro vehicle-track-bridge system under crosswind is established, in which crosswind loads model considering the condition of wind zone are built. After that, the evaluation indices and the calculation parameters have been selected, moreover, the basic characteristics of the dynamic system with high-pier under crosswind are analyzed. On this basis, the response varies with vehicle speed and wind speed are calculated, then the corresponding safety zone is determined. The results indicate that, crosswind triggers drastic vibration to the metro vehicle and high-pier viaduct, which in turn causes running instability of the vehicle. The corresponding safety zone for metro vehicle traveling on the high-pier is proposed, and the metro traffic on the high-pier bridge under crosswind should not exceed the corresponding limited vehicle speed to ensure the running safety.

Key Words
running safety; crosswind; high-pier viaduct; metro vehicle-track-bridge interaction; mountain city

Address
Yunfei Zhang: School of Mechatronics and Vehicle Engineering, Chongqing Jiaotong University, Chongqing 400074, China
Jun Li, Zhaowei Chen and Xiangyang Xu: School of Mechatronics and Vehicle Engineering, Chongqing Jiaotong University, Chongqing 400074, China;
Chongqing Key Laboratory of Integration and Control for Urban Rail Transit Vehicle System, Chongqing 400074, China


Abstract
The wind blowing at high velocity in an open storage yard leads to wind erosion and loss of material. Fence structures can be constructed around the periphery of the storage yard to reduce the erosion. The fence will cause turbulence and recirculation behind it which can be utilized to reduce the wind erosion and loss of material. A properly designed fence system will produce lesser turbulence and longer shelter effect. This paper aims to show the applicability of Support Vector Machine (SVM) to predict the recirculation length. A SVM model was built, trained and tested using the experimental data gathered from the literature. The newly developed model is compared with numerical turbulence model, in particular, modified k-e model along with the experimental results. From the results, it was observed that the SVM model has a better capability in predicting the recirculation length. The SVM model was able to predict the recirculation length at a lesser time as compared to modified k-e model. All the results are analyzed in terms of statistical measures, such as root mean square error, correlation coefficient, and scatter index. These examinations demonstrate that SVM has a strong potential as a feasible tool for predicting recirculation length.

Key Words
fence; recirculation length; support vector machine; modified k-

Address
Prashanth Janardhan: Department of Civil Engineering, National Institute of Technology Silchar, Assam, India
Harish Narayana: Department of Civil Engineering, M S Ramaiah Institute of Technology, Bengaluru, Karnataka, India

Abstract
Wind tunnel testing technique has been established as a powerful experimental method for predicting wind-induced loads on high-rise buildings. Accurate assessment of the design wind load combinations for tall buildings on the basis of wind tunnel tests is an extremely important and complicated issue. The traditional design practice for determining wind load combinations relies partly on subjective judgments and lacks a systematic and reliable method of evaluating critical load cases. This paper presents a novel optimization-based framework for determining wind tunnel derived load cases for the structural design of wind sensitive tall buildings. The peak factor is used to predict the expected maximum resultant responses from the correlated three-dimensional wind loads measured at each wind angle. An optimized convex hull is further developed to serve as the design envelope in which the peak values of the resultant responses at any azimuth angle are enclosed to represent the critical wind load cases. Furthermore, the appropriate number of load cases used for design purposes can be predicted based on a set of Pareto solutions. One 30-story building example is used to illustrate the effectiveness and practical application of the proposed optimization-based technique for the evaluation of peak resultant wind-induced load cases.

Key Words
wind tunnel test; load combinations; optimization-based framework; design envelope; tall buildings

Address
C.M. Chan, F. Ding and K.T. Tse: Department of Civil and Environmental Engineering, The Hong Kong Univ. of Science and Technology, Hong Kong
M.F. Huang: Institute of Structural Engineering, Zhejiang University, Hangzhou, P. R. China
K.M. Shum : CLP Power Wind/Wave Tunnel Facility, The Hong Kong University of Science and Technology, Hong Kong
K.C.S. Kwok: School of Civil Engineering, The University of Sydney, NSW 2006, Australia


Abstract
Pre-stressed concrete poles are among the supporting systems used to support transmission lines. It is essential to protect transmission line systems from harsh environmental attacks such as downburst wind events. Typically, these poles are designed to resist synoptic wind loading as current codes do not address high wind events in the form of downbursts. In the current study, the behavior of guyed pre-stressed concrete Transmission lines is studied under downburst loads. To the best of the authors\' knowledge, this study is the first investigation to assess the behaviour of guyed pre-stressed concrete poles under downburst events. Due to the localized nature of those events, identifying the critical locations and parameters leading to peak forces on the poles is a challenging task. To overcome this challenge, an in-house built numerical model is developed incorporating the following: (1) a three-dimensional downburst wind field previously developed and validated using computational fluid dynamics simulations; (2) a computationally efficient analytical technique previously developed and validated to predict the non-linear behaviour of the conductors including the effects of the pretension force, sagging, insulator\'s s stiffness and the non-uniform distribution of wind loads, and (3) a non-linear finite element model utilized to simulate the structural behaviour of the guyed pre-stressed concrete pole considering material nonlinearity. A parametric study is conducted by varying the downbursts locations relative to the guyed pole while considering three different span values. The results of this parametric study are utilized to identify critical downburst configurations leading to peak straining actions on the pole and the guys. This is followed by comparing the obtained critical load cases to new load cases proposed to ASCE-74 loading committee. A non-linear failure analysis is then conducted for the three considered guyed pre-stressed concrete transmission line systems to determine the downburst jet velocity at which the pole systems fail.

Key Words
guyed poles; transmission line structures; pre-stressed concrete poles; HIW-downbursts; finite element modelling

Address
Ahmed M. Ibrahim and Ashraf A. El Damatty: Department of Civil and Environmental Engineering. Western University, London, ON, Canada;
Structural Engineering Department. Faculty of Engineering, Cairo University, Giza, Egypt


Abstract
The modal frequency responses of adhesive bonded T-joint structure have been analyzed numerically and verified with own experimental data. For this purpose, the damped free frequencies of the bonded joint have been computed using a three-dimensional finite element model via ANSYS parametric design language (APDL) code. The practical relevance of the joint structure analysis has been established by comparing the simulation data with the in-house experimental values. Additionally, the influences of various geometrical and material parameters on the damped free frequency responses of the joint structure have been investigated and final inferences discussed in details. It is observed that the natural frequency values increase for the higher aspect ratios of the joint structure. Also, the joint made up of Glass fiber/epoxy with quasi-isotropic fiber orientation indicates more resistance towards free vibration.

Key Words
ANSYS APDL; fiber orientation; free vibration; glass/epoxy composite; T-joint, FEM

Address
Mani Chandra Kunche, Hari Babu Nallala, Pankaj V. Katariya and Subrata K. Panda: Department of Mechanical Engineering ,NIT Rourkela,769008, Odisha, India
Pradeep K. Mishra and Subhransu Panda: Department of Mechanical Engineering, BPUT, Rourkela, Odisha, India
Chetan K. Hirwani: Department of Mechanical Engineering, Aditya Engineering College, Surampalem-533437, Andhra Pradesh, India


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