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CONTENTS
Volume 31, Number 1, July 2020
 

Abstract
This paper presents a method of estimation of fatigue demands on connection bolts of tubular steel wind turbine towers. The presented method relies on numerical simulation of aerodynamic loads and structural behavior of bolted connections modeled using finite element method. Variability of wind parameters is represented by a set of values derived from their probability densities, which are adjusted based on field measurements. Numerically generated stress time-series show agreement with the measurements from strain gauges inside bolts, in terms of power spectra and the resulting damage. Position of each bolt has a determining effect on its fatigue damage. The proposed framework for fatigue life estimation represents the complexities in loading and local behavior of the structure. On the other hand, the developed procedure is computationally efficient since it requires a limited number of simulations for statistically representing the wind variations.

Key Words
wind turbine; tower; fatigue; finite element; aero-dynamic; bolted connection

Address
Behrouz Badrkhani Ajaei and Serdar Soyoz:Department of Civil Engineering, Bogazici University, Istanbul, Turkey

Abstract
The aircraft industry supports aviation by building aircraft and manufacturing aircraft parts for their maintenance. Fuel economization is one of the biggest concerns in the aircraft industry. The reduction in specific fuel consumption of aircraft can be achieved by a variety of means, simplest and more effective is the one to impose minor modifications in the aircraft main wing or the parts which are exposed to the air flow. This method can lead to a reduction in aerodynamic resistance offered by the air and have a smoother flight. The main objective of this study is to propose geometric design modifications on an existing aircraft wing which acts as a vortex generator and it can reduce the drag and increase lift to drag ratio, leading to lower fuel consumption. The NACA 2412 aircraft wing is modified and designed. Rigorous flow analysis is carried out using computational fluid dynamics based software Ansys Fluent. Results show that saw tooth modification to the main wing shows the best aerodynamic efficiency as compared to other modifications.

Key Words
aircraft industry; NACA; fuel economization; aerodynamic efficiency; ANSYS fluent

Address
Shiva Kumar M.R, Srinath R, Vigneshwar K and Ravi Kumar B:School of Mechanical Engineering, SASTRA Deemed University, Thanjavur, Tamilnadu, India

Abstract
The wind field measurement of severe winds such as hurricanes (or typhoons), thunderstorm downbursts and other gales is important issue in wind engineering community, both for the construction and health monitoring of the wind-sensitive structures. Although several wireless data transmission systems have been available for the wind field measurement, most of them are not specially designed for the wind data measurement in structural wind engineering. Therefore, the field collection is still dominant in the field of structural wind engineering at present, especially for the measurement of the long-term and high-frequency wind speed data. In this study, for remote wind field measurement, a novel wireless long-term and high-frequency wind data acquisition system with the functions such as remote control and data compression is developed. The system structure and the collector are firstly presented. Subsequently, main functions of the collector are introduced. Also novel functions of the system and the comparison with existing systems are presented. Furthermore, the performance of this system is evaluated. In addition to as the wireless transmission for wind data and hardware integration for the collector, the developed system possesses a few novel features, such as the modification of wind data collection parameters by the remote control, the remarkable data compression before the data wireless transmission and monitoring the data collection by the cell phone application. It can be expected that this system would have wide applications in wind, meteorological and other communities.

Key Words
wind field measurement; remote control; data compression; wireless data transmission; cell phone application; integration

Address
Ning Zhao:School of Civil Engineering, Sichuan Agricultural University, Chengdu 611830, China
Guoqing Huang:School of Civil Engineering, Chongqing University, Chongqing 400044, China/ School of Civil Engineering, Southwest Jiaotong University, Chengdu 610031, China
Ruili Liu :School of Civil Engineering, Chongqing University, Chongqing 400044, China
Liuliu Peng:School of Civil Engineering, Chongqing University, Chongqing 400044, China



Abstract
Aiming at the wind-resistant design of a sea-crossing arch bridge, the static aerodynamic coefficients of its girder (composed of stretches of

Key Words
static aerodynamic force coefficients; numerical simulation; girder; wind tunnel test; arch bridge

Address
Institute of Bridge Engineering, Zhejiang University of Technology,288 Liuhe Road Hangzhou 310023, China

Abstract
A new type of bridge deck section consisting of four-box decks, two side decks for vehicular traffic lanes and two middle decks for railway traffic, has been experimentally investigated for determining its aerodynamic properties. The eight flutter derivatives were determined by the Iterative Least Squares (ILS) method for this new type of four-box deck model, with two windshields of 30 mm and 50 mm height respectively. Wind tunnel experiments were performed for angles of attack α=±6° ±4° ±2° and 0° and Re numbers of 4.85 x105 to 6.06x105 and it was found that the four-box deck with the 50 mm windshields had a better aerodynamic performance. Also, the results showed that the installation of the windshields reduced the values of the lift coefficient CL for the negative angles attack in the range of -6° to 0° but the drag coefficient CD increased in the positive angle of attack range. However, galloping instability was not encountered for the tested reduced wind speeds, of up to 9.8. The aerodynamic force coefficients and the flutter derivatives for the four-box deck model were consistent with the results reported for the Messina triple-box bridge deck, but were different from those reported for the twin-box bridge decks.

Key Words
flutter derivatives; four-box bridge deck; aerodynamic coefficients; wind tunnel tests

Address
Xi Chen :Power Construction Corporation of China, Chengdu, Republic of China
Elena Dragomirescu: Department of Civil Engineering, University of Ottawa, 161 Louis Pasteur, Ottawa, K1N 6N5, ON, Canada

Abstract
Considering the wind barriers induced aerodynamic characteristic variations of both bridge deck and trains, this paper studies the effects of wind barriers on the safety and stability of trains as they run through an urban rail transit cable-stayed bridge which tends to be more vulnerable to wind due to its relatively low stiffness and lightweight. For the bridge equipped with wind barriers of different characteristics, the aerodynamic coefficients of trains and bridge decks are obtained from wind tunnel test firstly. And then, the space vibration equations of the wind-train-bridge system are established using the experimentally obtained aerodynamic coefficients. Through solving the dynamic equations, one can calculate the dynamic responses both the trains and bridge. The results indicate that setting wind barriers can effectively reduce the dynamic responses of both the trains and bridge, even though more wind forces acting on the bridge are caused by wind barriers. In addition, for urban rail transit cable-stayed bridges located in strong wind environment, the wind barriers are recommended to be set with 20% porosity and 2.5 m height according to the calculation results of cases with wind barriers porosity and height varying in two wide ranges, i.e., 10% - 40% and 2.0 m to 4.0 m, respectively.

Key Words
wind barrier; train; cable-stayed bridge; wind tunnel test; coupled vibration

Address
Wei He:School of Civil Engineering, Anhui Jianzhu University, Hefei, 230601, China
Xiang-Rong Guo:School of Civil Engineering, Central South University, Changsha, 410075, China
Zhi-hui Zhu:School of Civil Engineering, Central South University, Changsha, 410075, China
Pengru Deng :Faculty of Engineering, Hokkaido University, Sapporo, 0608628, Japan
Xu-hui He:School of Civil Engineering, Central South University, Changsha, 410075, China


Abstract
Wind fragility analysis (WFA) of concrete chimney is often executed disregarding temperature effects. But combined wind and temperature effect is the most critical limit state to define the safety of a chimney. Hence, in this study, WFA of a 70 m tall RC chimney for combined wind and temperature effects is explored. The wind force time-history is generated by spectral representation method. The safety of chimney is assessed considering limit states of stress failure in concrete and steel. A moving-least-squares method based dual response surface method (DRSM) procedure is proposed in WFA to alleviate huge computational time requirement by the conventional direct Monte Carlo simulation (MCS) approach. The DRSM captures the record-to-record variation of wind force time-histories and uncertainty in system parameters. The proposed DRSM approach yields fragility curves which are in close conformity with the most accurate direct MCS approach within substantially less computational time. In this regard, the error by the single-level RSM and least-squares method based DRSM can be easily noted. The WFA results indicate that over temperature difference of 150°C, the temperature stress is so pronounced that the probability of failure is very high even at 30 m/s wind speed. However, below 100°C, wind governs the design

Key Words
fragility; wind force; temperature; RC chimney; Monte Carlo simulation; dual response surface method

Address
Gaurav Datta, Avinandan Sahoo and Soumya Bhattacharjya:Department of Civil Engineering, Indian Institute of Engineering Science and Technology (IIEST),
Shibpur, Howrah.-711103. West Bengal, India

Abstract
The aerostatic stability analysis of a long-span suspension bridge by the Element-free Galerkin (EFG) method is presented in this paper. Nonlinear effects due to wind structure interactions should be taken into account in determining the aerostatic behavior of long-span suspension bridges. The EFG method is applied to investigate torsional divergence of suspension bridges, based on both the three components of wind loads and nonlinearities of structural geometric. Since EFG methods, which are based on moving least-square (MLS) interpolation, require only nodal data, the description of the geometry of bridge structure and boundaries consist of defining a set of nodes. A numerical example involving the three-dimensional EFG model of a suspension bridge with a span length of 888m is presented to illustrate the performance and potential of this method. The results indicate that presented method can effectively be applied for modeling suspension bridge structure and the computed results obtained using present modeling strategy for nonlinear suspension bridge structure under wind flow are encouragingly acceptable.

Key Words
suspension bridge; Element-free Galerkin methods; aerostatic stability; wind loads; wind structure interaction

Address
Golriz Zamiria and Saeid R. Sabbagh-Yazdi:Department of Civil Engineering, KNToosi University of Technology, 1346, Valiasr St. (Mirdamad Cross), Tehran, Iran


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