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CONTENTS
Volume 34, Number 4, April 2022
 


Abstract
Irregularity in plan shape is very common for any type of building as it enhances better air ventilation for the inhabitants. Systematic opening at the middle of the facades makes the appearance of the building plan as a butterfly one. The primary focus of this study is to forecast the force, moment and torsional coefficient of a butterfly plan shaped tall building. Initially, Computational Fluid Dynamics (CFD) study is done on the building model based on Reynolds averaged Navier Stokes (RANS) k-epsilon turbulence model. Fifty random cases of irregularity and angle of attack (AOA) are selected, and the results from these cases are utilised for developing the surrogate models. Parametric equations are predicted for all these aerodynamic coefficients, and the training of these outcomes are also done for developing Artificial Neural Networks (ANN). After achieving the target acceptance criteria, the observed results are compared with the primary CFD data. Both parametric equations and ANN matched very well with the obtained data. The results are further utilised for discussing the effects of irregularity on the most critical wind condition.

Key Words
artificial neural networks; force and moment coefficients; irregular building; rational parametric equations; windinduced torques

Address
Prasenjit Sanyal:1)Department of Civil Engineering, Meghnad Saha Institute of Technology, Kolkata, India 2)Department of Civil Engineering, IIEST, Shibpur, Howrah, India

Sayantan Banerjee:1)Department of Civil Engineering, Meghnad Saha Institute of Technology, Kolkata, India 2)Department of Civil Engineering, IIEST, Shibpur, Howrah, India

Sujit Kumar Dalui:Department of Civil Engineering, IIEST, Shibpur, Howrah, India

Abstract
The current work numerically investigates the transient force and dynamic response of an overhead transmission tower–line structure caused by the passage of a high-speed train (HST). Taking the CRH2C HST and an overhead transmission tower–line structure as the research objects, both an HST–transmission line fluid numerical model and a transmission tower–line structure finite element model are established and validated through comparison with experimental and theoretical data. The transient force and typical dynamic response of the overhead transmission tower–line structure due to HST-induced wind are analyzed. The results show that when the train passes through the overhead transmission tower–line structure, the extreme force on the transmission line is related to the train speed with a significant quadratic function relationship. Once the relative distance from the track is more than 15 m, the train-induced force is small enough to be ignored. The extreme value of the mid-span dynamic response of the transmission line is related to the train speed and span length with a significant linear functional relationship.

Key Words
dynamic response; High-speed train (HST); numerical simulation; overhead transmission tower–line structure; train-induced wind force

Address
Meng Zhang:School of Civil Engineering, Zhengzhou University, Zhengzhou 450001, China

Ying Liu:School of Civil Engineering, Zhengzhou University, Zhengzhou 450001, China

Hao Liu:1)School of Civil Engineering, Zhengzhou University, Zhengzhou 450001, China
2)China Tower Co., Ltd. Luohe Branch, Luohe, 462000, China

Guifeng Zhao:School of Civil Engineering, Zhengzhou University, Zhengzhou 450001, China

Abstract
Section model test, as the most commonly used method to evaluate the aerostatic and aeroelastic performances of long-span bridges, may be carried out under different conditions of incoming wind speed, geometric scale and wind tunnel facilities, which may lead to potential Reynolds number (Re) effect, model scaling effect and wind tunnel scale effect, respectively. The Re effect and scale effect on aerostatic force coefficients and aeroelastic characteristics of streamlined bridge decks were investigated via 1:100 and 1:60 scale section model tests. The influence of auxiliary facilities was further investigated by comparative tests between a bare deck section and the deck section with auxiliary facilities. The force measurement results over a Re region from about 1x105 to 4x105 indicate that the drag coefficients of both deck sections show obvious Re effect, while the pitching moment coefficients have weak Re dependence. The lift coefficients of the smaller scale models have more significant Re effect. Comparative tests of different scale models under the same Re number indicate that the static force coefficients have obvious scale effect, which is even more prominent than the Re effect. Additionally, the scale effect induced by lower model length to wind tunnel height ratio may produce static force coefficients with smaller absolute values, which may be less conservative for structural design. The results with respect to flutter stability indicate that the aerodynamic-dampingrelated flutter derivatives A2* and A*1H*3 have opposite scale effect, which makes the overall scale effect on critical flutter wind speed greatly weakened. The most significant scale effect on critical flutter wind speed occurs at +3° wind angle of attack, which makes the smallscale section models give conservative predictions.

Key Words
auxiliary facilities; bridge; flutter; Reynolds number effect; scale effect; static force coefficients; wind-tunnel test

Address
Tingting Ma and Chaotian Feng: College of Ocean Science and Engineering, Shanghai Maritime University, Shanghai 201306, China

Abstract
Buildings with mono-sloped roofs are used for different purposes like at railway platforms, restaurants, industrial buildings, etc. Between two types of mono-slope roofs, clad and unclad, unclad canopy types are more vulnerable to wind load as wind produces pressure on both upper and lower surfaces of the roof, resulting in uplifting of the roof surface. This paper discusses the provisions of wind loads in different codes and standards for Low-rise buildings. Further, the pressure coefficients on mono-slope canopy roof available in wind code and standards are compared. Previous experimental studies for mono-slope canopy roof along with the recent wind tunnel testing carried out at Indian Institute of Technology, Roorkee is briefly discussed and compared with the available wind codes. From the study it can further be asserted that the information available related to staging or blocking under the mono-slope canopy roofs is limited. This paper is an attempt to put together the available information in different wind codes/standards and the research works carried out by different researchers, along with shedding some light on the future scopes of research on mono-slope canopy roofs.

Key Words
low-rise building; mono-slope canopy; pressure coefficient; suction; wind code; wind load

Address
Ajay Pratap:Dr. B R Ambedkar National Institute of Technology, Jalandhar, India

Neelam Rani:1)Dr. B R Ambedkar National Institute of Technology, Jalandhar, India
2)Faculty of Engineering (Civil), Dr. B R Ambedkar National Institute of Technology, Jalandhar, India

Abstract
Global Warming has been driven majorly by the consumption of fossil fuels. Harnessing energy from wind is viable solution towards reducing carbon footprint created due to burning such fuels, However, wind turbines have their problems of flow separation and aerodynamic stall to tackle with. In an attempt to delay the stall angle and improve the aerodynamic characteristics of the NACA 0015 symmetrical aerofoil, lateral cylindrical ridges were attached to its suction surface, at chord positions ranging from 0.1c to 0.5c. The characteristics of the original and ridged aerofoils were obtained using simultaneous pressure readings taken in a wind tunnel, at a free stream Reynolds number of Re= 2.81 x 105 for a wide range of free stream angles of attack ranging from -45° to 45° . Depending on the ridge size, a delay in stall angle varying from 5° to 20∘ was achieved together with the maximum increase in lift in the post-stall phases. Additionally, efforts were made to identify the optimum position for each ridge.

Key Words
cylindrical/circular ridges; flow separation; separation bubble

Address
V.S. Raatan, S. Ramaswami, S. Mano and S. Nadaraja Pillai: Turbulence and Flow Control Laboratory, School of Mechanical Engineering, SASTRA Deemed University, Thanjavur 613401, India


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