Modal Parameters Identification Of Super High-rise Buildings Based On Bayesian Framework And Statistical Characteristics Analysis Of Modal Parameters

With the development of construction technology,a large number of high-rise /super high-rise buildings with novel structural system have been built in the southeast coast of China.Modal parameters provide important reference information for the analysis of vibration characteristics,structural health monitoring,structural damage identification,finite element model modification and wind resistance design of high-rise/super high-rise buildings.Therefore,it is necessary to evaluate the modal parameters of building structures reasonably.Because there are often uncertainties when analyzing the dynamic characteristics of structures,this paper mainly analyzes and evaluates these uncertainties from a statistical perspective.Firstly,Bayesian Spectral Density Approach(BSDA)are exploited to experimentally identify the dynamic characteristics of a single super high-rise building under the excitation of strong typhoon,and the uncertainty of the modal parameters is analyzed to demonstrate the effectiveness and superiority of this method.The BSDA method is then used to identify the modal parameters of the structural responses of several super high-rise buildings that were subjected to the typhoons,and the modal identification results are compared with those obtained via several existing statistical models.Finally,a database of the dynamic properties of high-rise buildings is established through a wide collection of related information from public sources,which is used to updated the existing statistical models of buildings’ modal parameters which tend to lose efficiency for super-tall buildings since very limited information on buildings with a height exceeding 200 m has been incorporated in associated database.BSDA belongs to frequency-domain identification method of modal parameter identification technology under Bayesian framework.It considers that the power spectral density(PSD)of the structural response would approximately follow the Chi-square probability distribution.Using the statistical characteristics of PSD,the posterior probability density function with modal parameters is constructed by BSDA to determine the optimal value of the modal parameters.Compared with the deterministic method,BSDA method has obvious advantages of providing quantitative analysis information for the uncertainty of modal parameter.Therefore,it has been widely used in the analysis of dynamic characteristics of super high-rise buildings.In addition,the BSDA can not only identify the natural frequency and damping ratio,but also provide the results of the PSD of modal excitation.In this thesis,the modal parameters of the 300 m high Leatop Plaza in Guangzhou subjected to Typhoon Mangkhut is identified via the BSDA method.Results reveal that the PSD of modal excitation was positively related to wind speed and structural response,but the identified natural frequencies and damping ratios are scattered more severely.Quantitative analysis of the uncertainty of each parameter shows that the uncertainty of the damping ratio and PSD of modal excitation are much higher than that of natural frequency,illustrating that the BSDA method is able to provide more accurate identification of natural frequency.The BSDA method is then utilized to identify the modal parameters of multiple super high-rise buildings subjected to typhoons.The results suggest that the vibration amplitude of the buildings and the length of structural response signals have great influence on the identification results of damping ratio.It is also noticed that the identification results of natural frequency and damping ratio deviate from several existing statistical models of buildings’ modal parameters.Most of the existing statistical models are obtained on the basis of field measurements for buildings whose structure heights do not exceed 200 meters.Consequently,they can hardly be used to predict the dynamic properties of super high-rise buildings with ever increasing heights.Through wide collection from public journal sources,a field database for the modal parameters of super high-rise buildings is established in this thesis,which totally covers 293 buildings with varied structural systems,and 119 super high-rise buildings whose heights exceed 200 meters.Based on the database,the modal parameters of high-rise buildings are systematically analyzed,and a statistical prediction model is established which becomes more suitable for super high-rise buildings.The dynamic properties information of buildings above and below 200 meters are classified to analysis,and a new prediction model is proposed for the relationship between 1st swaying mode and 1st torsional mode with respect to the structural height and the number of floors.In addition,the relationship among the damping ratio of torsional modal and torsional modal,natural frequency,structural height,average height between floors,amplitude,etc.is analyzed and demonstrated.Results from this part provide useful information for predicting the dynamic properties of super-tall buildings reasonably.The results from this thesis provide useful reference for better understanding the typhoon-effects on super-tall buildings and for accurately predicting the dynamic properties of high-rise buildings.Related outcomes are of practical importance to facilitate the wind resistant design of super high-rise buildings and other wind-sensitive structures.