Showing papers by "Qiusheng Li published in 2016"

Monitoring Wind Characteristics and Structural Performance of a Supertall Building during a Landfall Typhoon

Abstract: Wind characteristics in the atmospheric boundary layer (ABL) and structural performance under extreme wind conditions are of major concern in the design of tall buildings in tropical cyclone-prone regions. On August 22, 2008, Typhoon Nuri (0812) made landfall over Hong Kong and then passed over its city center. This paper presents the analyzed results of the observations collected at two offshore meteorological stations and by a structural health monitoring system installed in a 420-m-high supertall building in downtown Hong Kong during the entire passage of Typhoon Nuri. The wind characteristics over open (sea) and urban (city) terrains at different stages of the typhoon are presented and discussed. Moreover, the wind-induced responses of the supertall building during the typhoon are investigated. The structural dynamics properties and serviceability of the supertall building during a landfall typhoon are evaluated. This study aims to investigate the wind characteristics in the ABL during a landf...

Identification of Wind Loads and Estimation of Structural Responses of Super-Tall Buildings by an Inverse Method

Abstract: This article presents a Kalman-filter-based estimation algorithm for identification of wind loads on a super-tall building using limited structural responses. In practice, acceleration responses are most convenient to be measured among wind-induced dynamic responses of structures. The proposed inverse method allows estimating the unknown wind loads and structural responses of a super-tall building using limited acceleration measurements. Taipei 101 Tower is a super-tall building with 101 stories and a height of 508 m. Field measurements and numerical simulations of the wind effects on Taipei 101 Tower are conducted. The wind loads acting on the super-tall building are estimated based on the wind-induced responses determined from the numerical simulations and the refined finite-element model of the structure, which are in good agreement with the exact results. The stability performance of the proposed algorithm is evaluated. The influence of noise levels in the measurements and covariance matrix of noise on the identification accuracy are investigated and discussed based on the L-curve method. Finally, the wind loads and structural responses are reconstructed based on the field-measured accelerations during Typhoon Matsa. The accuracy of the identified results is verified by comparing the reconstructed acceleration responses with the field measurements. The results of this study show that the proposed inverse approach can provide accurate predictions of the wind loads and wind-induced responses of super-tall buildings based on limited measured responses.

Monitoring of dynamic behaviour of super-tall buildings during typhoons

Abstract: This paper presents the field measurement results of the wind effects on two super-tall buildings (having height over 400 m) in Hong Kong during the passage of Typhoon Nesat in 2011. The field data such as wind speed, wind direction, structural acceleration and displacement responses were simultaneously recorded during the typhoon. Detailed analysis of the field data was conducted to investigate the wind field over an urban area, structural dynamic properties and wind-induced responses of the super-tall buildings. The typhoon-generated wind characteristics including turbulence intensity, gust factor and power spectral density of fluctuating wind speed were presented and discussed. The acceleration responses were analysed by Fourier transform to represent an averaged perspective over the records. Then, the wavelet transform was used to present time-frequency energy distributions of the structural vibrations. Instantaneous spectra were also presented for further discussions of the non-stationary signals. A ...

Large-eddy simulation of wind effects on a super-tall building in urban environment conditions

Abstract: A combined study of large-eddy simulation (LES), wind tunnel testing and full-scale measurement is conducted for the evaluation of wind effects on a super-tall building in a complex urban area. To validate the numerical simulations, the wind tunnel experiments including synchronous multi-pressure and high-frequency force balance model tests are conducted in a boundary layer wind tunnel laboratory. The numerical predictions are then compared with the experimental results, demonstrating that the LES can provide comparable predictions of the wind effects on the super-tall building. Furthermore, the cross-validation of the predicted displacement responses by the LES against the wind tunnel and full-scale measurements are presented and the agreement among them is reasonably good. The main objective of this study is to explore an effective numerical approach for the accurate estimation of wind effects on tall buildings in urban environment conditions and promote the practical use of the LES in the wind-resistan...

Across-wind dynamic loads on L-shaped tall buildings

Abstract: The across-wind dynamic loads on L-shaped tall buildings with various geometric dimensions were investigated through a series of wind tunnel testing. The lift coefficients, power spectral densities and vertical correlation coefficients of the across-wind loads were analyzed and discussed in details. Taking the side ratio and terrain category as key variables, empirical formulas for estimating the across-wind dynamic loads on L-shaped tall buildings were proposed on the basis of the wind tunnel testing results. Comparisons between the predictions by the empirical formulas and the wind tunnel test results were made to verify the accuracy and applicability of the proposed formulas. Moreover, a simplified procedure to evaluate the across-wind dynamic loads on L-shaped tall buildings was derived from the proposed formulas. This study aims to provide a simple and reliable way for the estimation of across-wind dynamic loads on L-shaped tall buildings.

Three-dimensional ambient noise tomography across the Taiwan Strait: The structure of a magma-poor rifted margin

Abstract: H.K-C. is supported by Ministry of Science and Technology (grant MOST104-2628-M-008-005-MY3). D. Brown acknowledges funding by MINECO grant-GL2013-43877-P. Q. Li and Z. Ye acknowledge funding by Sinoprobe-02-03. S wave tomography model presented in all figures can be obtained from the lead author (Hao Kuo-Chen, kuochen@ncu.edu.tw).

Analysis of Flutter and Nonlinear Dynamics of a Composite Laminated Plate

Abstract: This paper presents the analysis of flutter and nonlinear dynamics of an orthotropic composite laminated rectangular plate subjected to aerodynamic pressures and transverse excitation. The first-order linear piston theory is employed to model the air pressures. Based on Reddy's third-order shear deformation plate theory and von Karman-type equation for the geometric nonlinearity, the nonlinear governing equations of motion are derived for the composite laminated rectangular plate by applying the Hamilton's principle. The Galerkin method is utilized to discretize the partial differential governing equations to a set of nonlinear ordinary differential equations. The critical Mach number for occurrence of the flutter of the composite laminated plate is investigated by solving the eigenvalues problem. The relationship between the limit cycle oscillation and the critical Mach number is analyzed based on the nonlinear equations. The numerical simulation is conducted to study the influences of the transverse excitation on the nonlinear dynamics of the composited laminated plate. The numerical results, which include bifurcation diagram, phase plots and waveforms, demonstrate that there exist the bifurcation and chaotic motions of the composited laminated plate subjected to the aerodynamic pressures and the transverse excitation.

Identification of Wind Loads on Supertall Buildings Using Kalman Filtering–Based Inverse Method

Abstract: A Kalman filtering–based inverse method for identification of wind forces on supertall buildings is proposed. The new approach allows simultaneously estimating the wind loads and entire wind-induced responses of a supertall building using only a limited set of measurements. The effectiveness and good accuracy of the proposed algorithm are validated with experimental results. The wind loads acting on a supertall building are estimated based on the wind-induced responses determined from wind-tunnel testing. The stability of the proposed algorithm is evaluated. The effects of several key factors such as measurement noise, errors of structural modal parameters, and covariance matrix of noise on the identification accuracy are examined and discussed using the L-curve method. Finally, the identified wind loads on the supertall building based on field-measured displacements were compared with the wind-tunnel testing results to further verify the effectiveness of the inverse technique.

3D ambient noise tomography across the Taiwan Strait: the structure of a magma-poor rifted margin

Abstract: Rifting along southeastern Eurasia in the Late Cenozoic led to the formation of a magma-poor rifted margin facing the South China Sea to the southeast and the Philippine Sea to the east. Further rifting along the outer part of the margin during the Middle to Late Miocene was accompanied by an extensive episode of intraplate flood volcanism that formed the Penghu Archipelago. Previous geophysical studies in the area of the Strait have focused primarily on the shallow structures of the rift basins and the depth to the Moho. In this study we present the regional-scale 3D S-wave structure of the Taiwan Strait that is derived from a joint Chinese and Taiwanese 3D ambient noise tomography study. The S-wave model shows a thinning of the crust beneath the rift basins where, locally, thin high-velocity layers suggest the presence of intrusive bodies. The rift basin and the foreland basin along the west coast of Taiwan are imaged as low velocity zones with thicknesses between 5 and 10 km, and extending eastward beneath the Taiwan mountain belt. In the upper 10 km of the crust, the basaltic rocks of the Penghu Archipelago are imaged as a high velocity zone that, with depth, becomes a relatively low velocity zone. We interpret this low velocity zone in the lower crust and upper mantle beneath the Penghu Archipelago to image a thermal anomaly related to the still cooling magma feeding system and the melt reservoir area that fed the flood basalts at the surface.

Evaluation of wind loads and wind induced responses of a super-tall building by large eddy simulation

Abstract: Taipei 101 Tower, which has 101 stories with height of 508 m, is located in Taipei where typhoons and earthquakes commonly occur. It is currently the second tallest building in the world. Therefore, the dynamic performance of the super-tall building under strong wind actions requires particular attentions. In this study, Large Eddy Simulation (LES) integrated with a new inflow turbulence generator and a new sub-grid scale (SGS) model was conducted to simulate the wind loads on the super-tall building. Three-dimensional finite element model of Taipei 101 Tower was established and used to evaluate the wind-induced responses of the high-rise structure based on the simulated wind forces. The numerical results were found to be consistent with those measured from a vibration monitoring system installed in the building. Furthermore, the equivalent static wind loads on the building, which were computed by the time-domain and frequency-domain analysis, respectively, were in satisfactory agreement with available wind tunnel testing results. It has been demonstrated through the validation studies that the numerical framework presented in this paper, including the recommended SGS model, the inflow turbulence generation technique and associated numerical treatments, is a useful tool for evaluation of the wind loads and wind-induced responses of tall buildings.