Study Of Typhoon-induced Dynamic Responses Of A Super Tall Building Based On Structural Health Monitoring System

Numerous skyscrapers have been built in the past decades as a consequence of fast economic and social developments.Particularly,the new generation of skyscrapers is generally designed to be flexible and slender,which poses new challenges for their serviceability performance and safety under ambient excitations and extreme events.All these challenges further motivate the need to better understand the structural behaviors of those high-rise buildings through full-scale monitoring.In the context of such motivations,Ping-An Finance Center(PAFC)in Shenzhen,with a total height of 600 m,is considered as a desirable full-scale test benchmark platform for the assessment of structural performance of skyscrapers.An integrated structural health monitoring(SHM)system with total number of 553 sensors,which was designed based on the modular design methodology,is being installed in PAFC to monitor its structural performance and external excitations during both construction and service stages.Consequently,structural wind-induced dynamic responses obtained during the passage of strong typhoons,which are vital issues and widespread concerns about structural performances in the life cycle of super high-rise buildings from the beginning of construction to the whole service stage,are mainly presented and discussed in this dissertation:(1)The SHM system equipped in PAFC is of substantial practical significance for the application and promotion of SHM technologies in super-tall buildings.The integrated monitoring system for both in-construction and in-service monitoring allows the life-cycle observation of the structural states,from the beginning of construction to the whole service stage.The modular design of the SHM system ensures highly effective independence of each sub-system.The effectiveness and necessity of the design strategy,elevation reservation,was verified through the field measurements of the vertical deformations during the construction process.The shrinkage and creep of concrete and construction sequence have significant effects on the vertical deformations of PAFC(40%?50%),and the time-dependent effects should be taken into account in the numerical analysis of the vertical deformations of super-tall buildings.The elastic deformation played a dominated role at the construction stage.However,at the service stage,the shrinkage and creep-induced deformation will keep increasing moderately over a long period and eventually exceed the elastic deformation.Until the fifth service year,the vertical deformation will be mostly completed.(2)Based on the analysis results of field measurement from the Shenzhen Meteorological Tower,the averaged 10-min fluctuating winds match quite well with the standardized normal distribution(?N(0,1)).Spectral analysis results demonstrate the accuracy and reliability of the spectral estimation method for determining the turbulence integral length scale of winds based on the von Karman spectral model.In addition,Empirical formulas for gust factor with respect to different wind gust durations were validated and the relationship between gust factor(GF)and turbulence intensity(I)for the three components of fluctuating wind velocity can be depicted by linear models.The vertical wind profiles tended to exhibit some“kinks”for the cases of hilly terrain in the upwind direction or lower wind speeds,which may be attributed to the effects of thermally nonstationary conditions.In general,the empirical models can provide reasonable predictions for the measured wind speed profiles.The wind structure throughout the entire TBL of typhoon was explored.The measurements and subsequent analysis results showed that the vertical profiles of horizontal mean wind speed in the eyewall regions of Typhoon Nida were characterized by a LLJ which is absent in classical wind profile models of the ABL.The TBL depth increased radially outward and then remained almost constant.Effects of topography and terrain on the typhoon wind structure were evident.The measurements with upstream mountainous exposures were featured with an increased height of LLJ and intensified wind shears beneath,compared to those with comparatively upstream open exposures.(3)The observations of wind-induced pressures on the external surfaces of PAFC revealed that vortex shedding alternately occurred from its two sides.The Strouhal number was found about 0.12 which was consistent with those obtained from a scaled model of PAFC via wind tunnel tests and also with the St of a square prism.Probability distributions of negative pressures illustrated distinct non-Gaussian characteristics which became more evident with the increase of pressure amplitude.Moreover,the mean pressure coefficients obtained from the field measurements were in good agreement with those stipulated in the load code of China(GB50009-2012).The strain responses in PAFC were influenced by both wind strength and ambient temperature,while the 1^st swaying mode dominated the dynamic strain component.It is speculated from the strain measurements that when the gradient speed exceeds certain value range(81 m/s during Typhoon Nida),the skyscraper may experience vortex-induced resonance.(4)The spectral analysis results of the measured structural dynamic responses illustrated that the 1^st swaying modal component dominated the acceleration responses of PAFC and the 1^st torsional responses were generally one order smaller than those of the 1^stswaying mode.The identified natural frequencies decreased with the increase of the response amplitude while the damping ratios showed a fluctuation with the response amplitude.It is suggested that damping ratios of the fundamental swaying and torsional modes of 0.5%-1.2%appeared reasonable for the wind-resistant design of super-tall buildings similar to PAFC.The acceleration responses of PAFC during the typhoon were well confined within the upper limits stipulated in ISO-1984,indicating that the serviceability performance of the skyscraper during a moderate typhoon satisfactorily met the requirement of the international standard.The vibration control performance of damper system is compared and analyzed based on the theoretical analytical model and field measurement results.The theoretical results show that the damper system has a good control and attenuation effect on the first-order bending vibration of the structure,and the damping effect is 10%?40%under the influence of typhoon with return period of 1 year and 10 years.The measured results under strong typhoon show that the TMD system can suppress the wind-induced vibration of super high-rise buildings timely and effectively when the structural response exceeds the trigger level.The damping effect of the damper system is close to 50%during Typhoon Mangkhut.