Displacement Monitoring For Super Tall Building With Setbacks At Construction Stage

With the rapid development of China's economy and society,the construction of super high-rise buildings in China is increasing rapidly in recent years.The structural system of such tall buildings is becoming more and more complex.The common characteristic of such super-tall buildings includes long period in construction and complicated construction technology.Those factors,which include the complex loading,different construction nethods and contruction sequences,have great influence on the structural deformation for super tall buildings during the construction period.Therefore,it is very important to conduct the structural health and displacement monitoring of such super tall buildings.Such research studies could provide the guideline for the construction process and assure the safety of super tall building during the construction period.Various types of displacement monitoring method were adopted in this dissertation to investigate the Eastern Building of Huarun Center in Nanning City at its construction satge,and the measured data are compared with the numerical simulation results on structural performance of this super tall building with setbacks by stage construction analysis method.The main contents of this dissertation are as follows:(1)Several commonly used methods for displacement monitoring on super high rise buildings was briefly described.The minotoring instruments include GPS,total station,leveling,and tiltmeter.The basic principles,their characteristics and shortcomings for each displacement monitoring method by different instruments are analyzed.(2)The implementation scheme and key technical requirements of displacement monitoring on this tall building at construction stage are analyzed in detail.It mainly includes the transmission of control network,establishment of the planar control network at all different levels,dynamic survey and monitoring of the tall building at construction satge.Based on the differences in the height of the constructed tall buiding and the surroundingenvironment,the flexible external control method is adopted to combine with the internal control method,furthermore the dynamic deformation monitoring method by the combined use of "GNSS+Total station+Tiltmeter" is also used to demonstrate the principle and relevant procedures of displacment monitoring on this tall building.(3)The monitoring of horizontal and vertical displacement monitoring of the super tall building at 19 M,31M stories was first conducted by total station system.The monitoring points are located at both incore wall and outer steel columns.The changing trend of the horizontal displacement of the building at these two levels was evaluated.At the same time,the total station instrument is also utilized to conduct the dynamic monitoring and measurement on horizontal displacements at 31 M level.The combined Empirical Mode Decomposition(EMD)and Power Spectral Density analysis method was ultilized to analysis the measured dynamic displacement and obtain the first order natural frequency in the two main-axis direction of the super tall building.In addition,the long-term displacement monitoring was also conducted by the Global Positiong System(GPS)testing system atop of the building during construction.Meanwhile the combined EMD and PSD analysis on the GPS measured total dispalcemnt was also performed to evaluate the dynamic characteristics of the super tall building during construction.By comparing the displacement monitoring data from two different displacement measuring systems by total station and GPS,the effectivess of displacement monitoring methods from two types of measuring instruments could be verified.(4)Finally the horizontal dispalcemnt monitoring data for 19 M and 31 M stories from the total station was further compared with those corresponding numerical simulation results on structural performance of this super tall building with setbacks by stage construction analysis method.The comparing results show that the monitoring data are generally consistent with the numerical simulation results by the finite element analysis method.In addition,the trend of variation in the dispalcelments at the monitoring points at 19 M,31M floor levels also agreement with the change trend of those numerical analyzed displacement by the finite element simulation method.Comparing results of the natural frequency estimated from two different displacement testing methods(Total station and GPS)with those obtained from the numerical analysis method by FEM was finally conducted.The difference between them is within 10%.This proved the effectiveness of both GPS and total station methods in the continuous monitoring of dynamic deformation,and also reflected the reliability and correctness of the numerical analyzed results by stage construction analysis method.