Wind tunnel tests and numerical aerodynamic analyses were conducted for an integrated catwalk structure under strong winds. From the wind tunnel tests, it is found that the aerodynamic coefficients were different from those of the typical type. The drag coefficient was larger than typical and was sensitive to number of vertical meshes installed rather than the solidity ratio. Comparing with typical catwalk, the integrated one showed larger deformation under strong wind, and the large torsional deformation are mainly caused by drag force. It did not show aerodynamic divergence even the torsional deformation reaching $20^{\circ}$. The reason could be that the stiffness is smaller and thus the catwalk is able to deform to the shape compactable with higher loading. Considering safety for construction, storm rope system is introduced to the catwalk to reduce the deformation to acceptable level.

Investigations on simulated near-surface atmospheric boundary layer (ABL) in an open-jet facility are carried out by conducting experimental tests on small-scale models of low-rise buildings. The objectives of the current study are: (1) to determine the optimal location of test buildings from the exit of the open-jet facility, and (2) to investigate the scale effect on the aerodynamic pressure characteristics. Based on the results, the newly built open-jet facility is well capable of producing mean wind speed and turbulence profiles representing open-terrain conditions. The results show that the proximity of the test model to the open-jet governs the length of the separation bubble as well as the peak roof pressures. However, test models placed at a horizontal distance of 2.5H (H is height of the wind field) from the exit of the open-jet, with a width that is half the width of the wind field and a length of 1H, have consistent mean and peak pressure coefficients when compared with available results from wind tunnel testing. In addition, testing models with as large as 16% blockage ratio is feasible within the open-jet facility. This reveals the importance of open-jet facilities as a robust tool to alleviate the scale restrictions involved in physical investigations of flow pattern around civil engineering structures. The results and findings of this study are useful for putting forward recommendations and guidelines for testing protocols at open-jet facilities, eventually helping the progress of enhanced standard provisions on the design of low-rise buildings for wind.

The probabilistic information of directional extreme wind speeds is important for precisely estimating the design wind loads on structures. A new joint probability distribution model of directional extreme wind speeds is established based on observed wind-speed data using multivariate extreme value theory with the t-Copula function in the present study. At first, the theoretical deficiencies of the Gaussian-Copula and Gumbel-Copula models proposed by previous researchers for the joint probability distribution of directional extreme wind speeds are analysed. Then, the t-Copula model is adopted to solve this deficiency. Next, these three types of Copula models are discussed and evaluated with Spearman's rho, the parametric bootstrap test and the selection criteria based on the empirical Copula. Finally, the extreme wind speeds for a given return period are predicted by the t-Copula model with observed wind-speed records from several areas and the influence of dependence among directional extreme wind speeds on the predicted results is discussed.

Two types of aerodynamic admittance function (AAF) that have been adopted in bridge aerodynamics are addressed. The first type is based on a group of supposed relations between flutter derivatives and AAFs. In so doing, the aero-elastic properties of a section could be used to determine AAFs. It is found that the supposed relations hold only for cases when the gust frequencies are within a very low range. Predominant frequencies of long-span bridges are, however, far away from this range. In this sense, the AAFs determined this way are of little practical significance. Another type of AAFs is based on the relation between the Theodorsen circulation function and the Sears function, which holds for thin airfoil theories. It is found, however, that an obvious illogicality exists in this methodology either. In this article, a viewpoint is put forward that AAFs of bluff bridge deck sections are inherently dependent on oncoming turbulent properties. This kind of dependence is investigated with a thin plate and a double-girder bluff section via computational fluid dynamics method. Two types of wind fluctuations are used for identification of AAFs. One is turbulent wind flow while the other is harmonic. The numerical results indicate that AAFs of the thin plate agree well with the Sears AAF, and show no obvious dependence on the oncoming wind fields. In contrast, for the case of bluff double-girder section, AAFs identified from the turbulent and harmonic flows of different amplitudes differ among each other, exhibiting obvious dependence on the oncoming wind field properties.

Multivariate fluctuating pressures acting on a 2:1 rectangular section (2-D) with dimensions of 9 cm by 4.5 cm has been studied using wind tunnel experiments under uniform and smooth flow condition for various angles of wind incidence. Based on the variation of mean pressure coefficient distributions along the circumference of the rectangular section with angle of wind incidence, and with the aid of skin friction coefficients, three distinct flow regimes with two transition regimes have been identified. Further, variations of mean drag and lift coefficients, Strouhal number with angles of wind incidence have been studied. The applicability of Universal Strouhal number based on vortex street similarity of wakes in bluff bodies to the 2:1 rectangular section has been studied for different angles of wind incidence. The spatio-temporal correlation features of the measured pressure data have been studied using Proper Orthogonal Decomposition (POD) technique. The contribution of individual POD modes to the aerodynamic force components, viz, drag and lift, have been studied. It has been demonstrated that individual POD modes can be associated to different physical phenomena, which contribute to the overall aerodynamic forces.