Study On Simulations Of Translational And Torsional Fluctuating Wind-excitation And Extrapolation Reconstruction Of Wind Pressure Fields On The Claddings Of High-rise Buildings

With the development of social economy and technology,high-rise building is become more higher,and more flexible.Wind load is gradually one of important dynamic loads acted on these kinds of slender buildings,and may play a decisive role on the safety of high-rise building claddings and residential comfort.Due to strong wind action,occupants feel uncomfortable because of excessive vibration and property loss caused by damage of building claddings occur frequently.Therefore,the windresistant design of high-rise buildings is not only concerned on the structure safety,but also makes it necessary to study the residential comfort under normal conditions.The dynamic wind load simulation of along-wind,across-wind and torsional vibration analysis of structures bring some new problems,and concerns for structural wind engineering of high-rise buildings with non-linear damper device in time domain.The research results in this paper can be briefly divided into four parts: the simulation of fluctuating excitation of along-wind,across-wind and torsional wind loads on high-rise buildings,and reconstruction of wind pressure field on the surface of high-rise buildings.And the contents are as follows:(1)numerical simulation of fluctuating wind force excitation in the along-wind direction and wind-induced vibration analysis in time domain.Generally,it is reasonable to assume that the wind load data conform to the Gauss distribution for high-rise buildings that meet the proposed steady assumption.Wind speed spectrums proposed by Davenport,Kaimal and von Kármán are adopted respectively with spatial coherence function.The fluctuating wind force time series in the along-wind direction are simulated respectively by weighted amplitude wave superposition method along the height of the building.A wind-induced vibration analysis of typical rectangular high-rise buildings is carried out,and the results are compared with those of UND aerodynamic database,show that the RMS of acceleration calculated by von Kármán spectrum is basically consistent with that by Chinese load code and UND aerodynamic database.Davenport spectrum overestimates acceleration response by 30%~40%,but Kaimal spectrum underestimate the acceleration response by 20%?With the increase of reduced wind speed,RMS of structural acceleration response decreases by 5%~16%,RMS of structural top displacement response decreases by 5%~20%.On this basis,the wind induced vibration responses of the structure,considering the along-wind aerodynamic damping,are further studied.With the increase of reduced wind speed,RMS of structural acceleration response decreases by 5%~16%,and RMS of structural displacement response decreases by 5%~20%.(2)numerical simulation of fluctuating wind force excitation in the across-wind direction and wind-induced response of structure.To study the structural response under the cross-wind fluctuating wind force action,an improved simulation method of across-wind fluctuating excitation had been studied for rectangular high-rise buildings.First,across-wind inertia force had been formulated between the across-wind acceleration and floor mass distributed along structure height based on Newton's second theorem,and the coherence function for across-wind force spectrum was considerably adapted,then the cross spectrum of across-wind force was theoretically deduced and across–wind induced excitations along structure height had been generated by Weighted Amplitude Wave Superposition method.Research results show that the structural dynamic response was related to the natural frequency of the structure.Fora typical case,the mode 1 in across wind direction are dominant,and the second order frequency contributed greatly.Furthermore,vibration control of the case was analyzed when the viscous dampers established in the structure.The peak of frequency power spectrum corresponding to the mode 2 decreased distinctly with viscous dampers device for high-rise buildings.The first 2 modes or high modes must be considered while calculating across-wind acceleration.The findings of current work were of use and interest to researcher and designers involved in the wind-resistant design of high-rise buildings to nonlinear analysis and vibration control.When the reduction wind speed is about 10.02,RMS of the maximum cross-wind displacement peak appears at the top,increases by about 57.2%.Effective measures should be taken to avoid the aerodynamic effects in the wind-resistant design of structures.(3)numerical simulation of fluctuating torsional moment excitation in the torsional direction and wind-induced response of structure.A simulation method of torsional fluctuating excitation had been presented for rectangular high-rise buildings.First,interlayer torque power spectrum had been formulated between the torsional angular acceleration and rotary inertia distributed along structure height based on generalized Newton's second theorem,and the coherence function for torque power spectrum was considerably adapted,then the cross spectrum of torque was theoretically deduced,and torsional excitations along structure height had been generated by Weighted Amplitude Wave Superposition method.Research result shows that the mean RMS of torsional angular acceleration response in time domain is slightly larger than that of UND database,which is consistent in statistical sense.In addition,the torsional acceleration of the structure is mainly due to the contribution of the first torsional mode.(4)Extrapolation reconstruction of fluctuating wind pressure at the building corner region.However,to investigate wind pressure at the edge of the building,the work presented in this paper focuses on the extrapolation reconstruction of wind pressure fields.Here,we propose an improved proper orthogonal decomposition(POD)and Kriging method with a von Kármán correlation function to resolve this issue.The studies show that it works well for not only interpolation reconstruction but also extrapolation reconstruction.The proposed method does require determination of the Hurst exponent and other parameters analysed from the original data.Hence,the fluctuating wind fields have been characterized by the von Kármán correlation function,as an a priori function.The range of [0.75-0.85] for Hurst exponent of the windward side of the building is obtained by the R/S method.It shows that the time series of the data has long-term memory effect and belongs to a self-similar stochastic process.Compared with the cubic spline method and linear variogram of Kriging menthod,preliminary results suggest high efficiency in extrapolation reconstruction,and it is useful for extrapolation and interpolation reconstruction at the edge or corner regions in wind resistance design.