Showing papers by "Qiusheng Li published in 2012"

Wind characteristics of a strong typhoon in marine surfaceboundary layer

Abstract: High-resolution wind data were acquired from a 100-m high offshore tower during the passage of Typhoon Hagupit in September, 2008. The meteorological tower was equipped with an ultrasonic anemometer and a number of cup anemometers at heights between 10 and 100 m. Wind characteristics of the strong typhoon, such as mean wind speed and wind direction, turbulence intensity, turbulence integral length scale, gust factor and power spectra of wind velocity, vertical profiles of mean wind speed were investigated in detail based on the wind data recorded during the strong typhoon. The measured results revealed that the wind characteristics in different stages during the typhoon varied remarkably. Through comparison with non-typhoon wind measurements, the phenomena of enhanced levels of turbulence intensity, gust factors, turbulence integral length scale and spectral magnitudes in typhoon boundary layer were observed. The monitored data and analysis results are expected to be useful for the wind-resistant design of offshore structures and buildings on seashores in typhoon-prone regions.

The jump phenomenon effect on the sound absorption of a nonlinear panel absorber and sound transmission loss of a nonlinear panel backed by a cavity

Abstract: Theoretical analysis of the nonlinear vibration effects on the sound absorption of a panel absorber and sound transmission loss of a panel backed by a rectangular cavity is herein presented. The harmonic balance method is employed to derive a structural acoustic formulation from two-coupled partial differential equations representing the nonlinear structural forced vibration and induced acoustic pressure; one is the well-known von Karman’s plate equation and the other is the homogeneous wave equation. This method has been used in a previous study of nonlinear structural vibration, in which its results agreed well with the elliptic solution. To date, very few classical solutions for this nonlinear structural-acoustic problem have been developed, although there are many for nonlinear plate or linear structural-acoustic problems. Thus, for verification purposes, an approach based on the numerical integration method is also developed to solve the nonlinear structural-acoustic problem. The solutions obtained with the two methods agree well with each other. In the parametric study, the panel displacement amplitude converges with increases in the number of harmonic terms and acoustic and structural modes. The effects of excitation level, cavity depth, boundary condition, and damping factor are also examined. The main findings include the following: (1) the well-known “jump phenomenon” in nonlinear vibration is seen in the sound absorption and transmission loss curves; (2) the absorption peak and transmission loss dip due to the nonlinear resonance are significantly wider than those in the linear case because of the wider resonant bandwidth; and (3) nonlinear vibration has the positive effect of widening the absorption bandwidth, but it also degrades the transmission loss at the resonant frequency.

Large Eddy Simulations of Wind-Driven Rain on Tall Building Facades

Abstract: Wind-driven rain (WDR) on building facades may lead to water penetration, cladding damage, structural cracking, etc., which affect the durability of the claddings. This study aims to develop a numerical approach to the evaluation of WDR on tall building envelopes based on large eddy simulations (LESs) and a Eulerian multiphase model. The present method utilizes the concept of the multiphase model to deal with rain and wind, and both wind and rain motions as well as their interactions are treated under the Euler frame, which can significantly reduce the complexity in evaluations of WDR and simplify boundary condition treatments. Besides these advantages, unsteady-state WDR information such as the transient catch ratio of WDR, the spatial and temporal distributions of rain intensity, etc., can be predicted by the LES. A validation study shows that the simulation results agree well with the available experimental data, verifying the accuracy of the simulation approach based on the Eulerian multiphase...

Artificial neural network-based response surface methods for reliability analysis of pre-stressed concrete bridges

Abstract: Two artificial neural network (ANN)-based response surface methods for reliability analysis of pre-stressed concrete bridges are presented. The first method is the traditional ANN-based response surface method, originally introduced by Papadrakakis et al. in 1996 (Papadrakakis, M., Papadopoulos, V. and Lagaro, N., 1996. Structural reliability analysis of elastic-plastic structures using neural network and Monte carlo simulation. Computer Methods in Applied Mechanics and Engineering, 136, 145–163), which is applied here to the reliability analysis of pre-stressed concrete bridges. The second method is an improved ANN-based response surface method developed recently by the authors for the reliability analysis of truss structures, in which the key idea is that the uniform design method (UDM) is adopted to select training data for establishing an ANN model, thereby greatly improving the quality of training datasets for establishing an ANN model and dramatically reducing the required number of training dataset...

Characteristics of Wind Loads on Long-Span Roof

Abstract: In recent years, many large span roofs of airport waiting room and garage were destructed in the tropic storm, which have the characteristics of light mass, high flexibility, slight damping and low natural frequency. Wind loads general control the design of such structures. Thus, the tests of wind pressure with the rigid scale model in boundary layer wind tunnel were conducted in the structural design stage. This paper presents the results of characteristics of wind loads on large-span roof structure of the Guangzhou International Convention & Exhibition Center (GICEC) in frequency domain. The power spectrum densities, correlation coefficients, coherence functions and probability density function (PDF) were analyzed in detail. The results can be summarized as follows: (1)The power spectrum densities of fluctuating wind loads have the characteristics of vortex shedding and the Strouhal number is about 0.295; (2)The coherence coefficients decrease with the frequency and the spatial distance increase at both the along-wind and across-wind direction; (3)There are clearly negative skewed distributions for some pressure taps at the windward leading roof edge and much longer negative tails are observed, which follow Non-Gaussian distributions. The results presented in this paper are expected to be of considerable interest and of use to researchers and professionals involved in designing complex long-span roof structures.

Wind noise simulation and evaluation of a super high-rise building with wind turbine generators

Abstract: Pearl River Tower a sustainable building with wind turbine generators produces bigger environmental noise when wind blows through the tunnels of the building and due to exsitence of wind turbine generators.In order to prevent the effect of noise on the nearby office staff and residents and to avoid affecting the reputation and the performance of Pearl River Tower,it was necessary to predict and evaluate the noise level and distribution around Pearl River Tower.A broadband noise source model based on SST turbulence model was used to numerically simulate the noise level and distribution of the tunnels of Pearl River Tower and its wind turbine generators,then the influence of wind turbine generators on noise was analyzed.The numerical simulation results showed that with one year return period or the maximum monthly mean wind speed,the maximum noise of Pearl River Tower doesn't exceed the limits specified by the "Law of the People's Republic of China on Prevention and Control of Pollution From Environmental Noise".