Ming Gu

Summary: When a large super high‐rise building taller than the surrounding tall buildings is built in a dense urban area, the aerodynamic interference effects of the surrounding buildings on the proposed building attract much attention, while the interference effects of the taller high‐rise building on the nearby existing buildings are often ignored. Based on a series of wind tunnel tests, the interference effects of a proposed taller high‐rise building, an adjacent equal‐height partner building, and relatively short background buildings on the target building's local wind pressures are analysed in this paper. Two‐dimensional numerical simulation are carried out to further understand the interference mechanism in some cases. The test results show that the influence of a nearby proposed taller high‐rise building may lead to wind‐induced damage on the interfered shorter buildings' envelopes. The envelope structures of other surrounding buildings facing the side of the proposed building need to be given more attention.

Summary: Lattice towers are among the most vulnerable structures during typhoons. In this study, the wind engineering research field base near Shanghai Pudong International Airport was used to measure the mean wind speeds and directions at a height of 10 m, as well as the accelerations atop a 40‐m high lattice tower during Typhoons Neoguri and Nakri to investigate the characteristics of the near‐ground wind and the responses of the lattice tower. Moreover, an aeroelastic model of the lattice tower was generated by the discrete stiffness method. Using the wind tunnel test of the aeroelastic model, the root mean square accelerations of the tower were studied with different wind speeds and directions. The responses of the tower in the across‐wind direction were found always higher than those in the along‐wind direction, which meant the vortex shedding of each single cylinder had an impact on the responses of the tower in the across‐wind direction. The test results were compared with those of field measurements to evaluate the accuracy of the aeroelastic model, and the two were generally in a good agreement. Thus, the aeroelastic model could precisely simulate the dynamic characteristics of a prototypical lattice tower using the discrete stiffness method.

This paper aims to accurately calculate the time-varying standard deviation of nonstationary wind speed by modeling wind speed as a time-varying mean wind speed plus a uniformly modulated nonstationary process and applying the autoregressive moving average–generalized autoregressive conditional heteroscedasticity (ARMA-GARCH) model to analyze the time-varying standard deviation of the wind speed. This paper also proposes a convenient and practical first-order difference GARCH method for calculating the time-varying standard deviation of uniformly modulated nonstationary processes that can decrease the computation time. The applicability of the ARMA–GARCH model, first-order difference GARCH method, and existing common methods for calculating the time-varying standard deviation of nonstationary wind speed are verified and analyzed using numerical simulations. The results show that the ARMA-GARCH model and first-order difference GARCH method are superior to the existing common methods. Finally, with the combination of the ARMA-GARCH model and first-order difference GARCH method, the nonstationary wind characteristics (considering the nonstationarities of mean wind speed and standard deviation) of Typhoon Chan-hom are investigated and compared with the results only taking into account time-varying mean wind speed.

A series of wind tunnel tests were conducted to investigate the effects of parapets of different configurations and various heights on the wind loading of a flat-roofed low-rise building. Local wind pressures, area-averaged peak pressures, and overall roof uplift force on the roof were determined. Spectral analysis was also performed to better understand the mechanism of how the presence of parapets affects the wind effects on the building. Additional attention was given to the power spectral density and non-Gaussian features of the area-averaged wind pressures. The results show that low parapets (h/H no more than 0.1) often increase suctions in the roof corner region. The presence of high parapets results in a decrease in the wind effects over the roof corners; however, it also leads to a growth of the uplift force over the entire roof. Comparisons among many different parapet configurations show that the ones with the raised and bottom-slotted corners help to efficiently alleviate the worst suction on flat roofs. In addition, the high parapet acts as a low-pass filter, filters out parts of the high-frequency energy in the approach flow, and stabilizes the wind pressure distribution on roof.

To accurately identify the nonlinear damping ratio of tall buildings, the authors propose an envelope random decrement technique (RDT). To verify the accuracy of the envelope RDT for the evaluation of amplitude-dependent nonlinear damping ratio, an iterative computing method, which can accurately work out the response of structures whose parameters depend on the response amplitude in any form, is also proposed. Then, using three different damping models in the numerical simulations, of which the response is calculated by the proposed iterative computing method, the applicabilities of traditional RDT, RDT ranked by peak amplitude, and the envelope RDT presented in this paper for the evaluation of amplitude-dependent nonlinear damping ratio are analyzed and compared. Results indicate that envelope RDT is better than the other two methods for the evaluation of amplitude-dependent nonlinear damping ratio. Finally, the envelope RDT is applied to identify the damping ratios of the Shanghai World Financi...