Abstract
High-sided road vehicles are susceptible to a sharp-edged crosswind gust, which may cause vehicle accidents such as overturning, excessive sideslip, or exaggerated rotation. This paper thus investigates the dynamic behaviour and possible accidents of high-sided road vehicles entering a sharp-edged crosswindrngust with road surface roughness and vehicle suspension included. The high-sided road vehicle is modelled as a combination of several rigid bodies connected by a series of springs and dampers in both vertical and lateral directions. The random roughness of road surface is generated from power spectral density functions for various road conditions. The empirical formulae derived from wind tunnel test results are employed to determine aerodynamic forces and moments acting on the vehicle. After the governing equations of motion are established, an extensive computation work is performed to examinernthe effects of road surface roughness and vehicle suspension on the dynamic behaviour and vehicle accidents. It is demonstrated that for the high-sided road vehicle and wind forces specified in the computation, the accident vehicle speed of the road vehicle running on the road of average condition is relatively smaller than that running on the road of very good condition for a given crosswind gust. The vehicle suspension system should be taken into consideration, and the accident vehicle speed becomes smaller if the vehicle suspension system has softer springs and lighter dampers.
Address
Y.L. XurnDepartment of Civil and Structural Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong KongrnW.H. GuornSchool of Civil Engineering and Architecture, Central South University, Changsha, China
Abstract
Experimental studies on drag reduction of a circular cylinder of diameter D were conducted in the subcritical flow regime at Reynolds numbers in the range 4
Key Words
drag reduction; circular cylinder; shield plates; base cavity; separation; wake.
Address
Department of Civil Engineering, University of Jordan, Amman, Jordan
Abstract
A number of methods based on various ideas have been proposed for simulating the non-Gaussian stationary process. However, these methods have some limitations. This paper reviewed several simulation methods based on the translation method using logarithmic and polynomial functions, which have emerged in the history of statistics and in the field of civil engineering. The applicability of each method is discussed from the viewpoint of the reproducibility of higher order statistics of the object function in the simulated sample functions, and examined using pressure signals measured from wind tunnel experiments for various shapes of buildings. The parameter estimation methods, i.e. the method of moments and quantile plot, are also reviewed, and the useful aspects of each method are discussed. Additionally, a simple worksheet for parameter estimation is derived based on the method of moment for practical application, and the accuracy is discussed comparing with a set of previously proposed formulae.
Address
Institute of Environmental Studies, Graduate School of Frontier Sciences,rnThe University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
Abstract
In the past decades, much effort has been made towards the study of single-mode-based vibration controls with dynamic energy absorbers such as single or multiple Tuned Mass Dampers(TMDs). With the increase of bridge span length and the tendency of the bridge cross-section being more slender and streamlined, multi-mode coupled vibrations as well as their controls have become very important for large bridges susceptible to strong winds. As a simple but effective device, the TMD system especially the semi-active one has become a promising option for such coupled vibration controls. However, despite various studies of optimal controls of single-mode-based vibrations with TMDs, researchrnon the corresponding controls of the multi-mode coupled vibrations is very rare so far. For the development of a semi-active control strategy to suppress the multi-mode coupled vibrations, a comprehensive parametric analysis on the optimal variables of this control is substantial. In the present study, a multi-mode controlrnstrategy named
Key Words
buffeting; tuned mass damper; mode coupling; long-span bridge; control.
Address
S.R. Chen and C.S. CairnDepartment of Civil and Environmental Engineering, Louisiana State University, Baton Rouge, LA 70803, USArnM. GurnDepartment of Bridge Engineering, Tongji University, Shanghai 200092, ChinarnC.C. ChangrnDepartment of Civil Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
Abstract
This paper presents an extensive analysis of the short term, unsteady wind loading on a lowrise building. The building is located in a rural environment and only the specific situation of wind flow orthogonal to the long face of the structure is considered. The data is analysed using conventional analysis and less traditional methods such as conditional sampling and wavelet analysis. The nature of the flow field over the building is found to be highly unsteady and complex. Fluctuating pressures on the windward wall are shown to a large extent to be caused by the fluctuations in the upstream flow, whereas extreme pressures on the roof are as a result of high intensity small scale flow structures. On the roof of the building a significant amount of energy is shown to exist at frequencies above 1 Hz.
Key Words
unsteady loading; conditional sampling; wavlet analysis; low-rise building.
Address
M. Sterling and C.J. BakerrnSchool of Engineering, The University of Birmingham, Edgbaston, Birmingham, B15 2TT, UKrnR.P. HoxeyrnSilsoe Research Institute, Wrest Park, Silsoe, Bedford, MK45 4HS, UK
