A new method for dynamic parameters identification of a model-balance system in high-frequency force-balance wind tunnel tests

The high-frequency force-balance (HFFB) technique is one of the most popular methods for assessment of the wind-induced response of tall buildings. Before the measured data being processed, an additional treatment should be made to modify the amplification caused by the model-balance system. This procedure requires determining the dynamic parameter of the model-balance system first. The knocking test method is usually adopted to identify the natural frequency and damping ratio of the model-balance system. However, there are some shortcomings of this approach. First, it requires an additional knocking test, and second, the identified damping ratio by adopting the knocking method is only the structural damping of the model-balance system and the aerodynamic damping of the model is neglected. In this study, a new approach is proposed to identify the natural frequency and damping ratio of the model-balance system based on the measured data in wind tunnel tests. The knocking test is no longer necessary and the identified damping ratio is the entire damping ratio of the model-balance system, that is, the structural damping and the aerodynamic damping are both included. Three illustrative examples, including a hypothetical building, the Commonwealth Advisory Aeronautical Research Council (CAARC) tall building, and two actual buildings with rectangular and nonrectangular cross-sections, are considered to examine the validation of the proposed method. It is shown that the damping ratio of the model-balance system is different under different wind directions, and the actual power spectral density (PSD) of the overturning moments at the base of the model can be calculated accurately by adopting these identification results

Wind effects on a long span steel roof structure: numerical simulation and equivalent static wind loads

A wind tunnel test is conducted in this study on the scaled model of the Guangzhou International Sports Arena (GISA). Simultaneous pressure measurements are conducted in a simulated suburban boundary layer flow field. A numerical simulation approach using Fuzzy Neural Networks (FNNs) is developed for the predictions of wind-induced pressure time series at roof locations which are not covered in the wind tunnel measurements. On the other hand, the wind-induced response of the roof are presented and discussed, which are directly calculated by the Complete Quadratic Combination (CQC) approach. Furthermore, the correlations between the background and resonant response components are discussed in detail, and the results show that neglecting the correlations between the two components would result in considerable error in the response estimation. Finally, the Equivalent Static Wind Load (ESWL) approach is used to estimate the wind-induced responses of the roof, which are compared with those obtained from the CQC approach to examine the effectiveness of the proposed ESWL approach in the design and analysis of large-span roof structures. It is shown through the example that the FNN and ESWL approaches can successfully predict the wind-induced pressures and responses respectively

Walks on weighted networks

We investigate the dynamics of random walks on weighted networks. Assuming that the edge's weight and the node's strength are used as local information by a random walker, we study two kinds of walks, weight-dependent walk and strength-dependent walk. Exact expressions for stationary distribution and average return time are derived and confirmed by computer simulations. We calculate the distribution of average return time and the mean-square displacement for two walks on the BBV networks, and find that a weight-dependent walker can arrive at a new territory more easily than a strength-dependent one.Comment: 4 pages, 5 figures. minor modifications. Comments and suggestions are favored by the author