Wind Effects And Dynamic Characteristics Of Long-span Round Bamboo Arch Structure

The large-span round bamboo arch structure has the characteristics of large-span,light weight and low damping,so it is sensitive to wind loads.Due to the limit knowledge of the wind effects and structural dynamic characteristics of the large-span round bamboo arch structure by now,it is inconvenient to design the round bamboo structure,not to mention the deficiency of necessary measured data.In response to these practical problems,this paper studies wind field and structural dynamic characteristics of a certain type of large-span round bamboo arch,aiming to provide a reference for the design of similar round bamboo structures.This paper takes the large-span Bamboo Arch Pavilion(Expo 2019,Beijing)with round bamboo materials as the research object.Wind speed and acceleration response data were obtained through on-site monitoring,after which we carried out relevant research basis of monitoring data.The research content is as follows :(1)Developed a wind field monitoring test plan;(2)The average wind characteristics,fluctuating wind characteristics,self-similarity and long-range correlation of wind speed during the monitoring period were solved by processing and analyzing the wind speed data obtained from monitoring;(3)By processing and analyzing the vibration data obtained by monitoring,the vibration characteristics of this type of structure are studied;(4)The Peak Picking method(PP)and Stochastic Subspace Identification based on covariance(SSI-COV)are used to study the dynamic characteristics of Bamboo Arch Pavilion;(5)Based on the measured modal parameters,parameter-type correction method based on sensitivity was adopted to modify the initial finite element model.The results of the study are as follows.(1)During the period of monitoring,the dominant wind direction of the wind field was northwest,and the wind angle of attack was small.There is a certain difference between the measured power spectrum and the Von Karman specification spectrum,so the power spectrum given in the specification cannot be directly used to describe the actual wind field characteristics around the large-span round bamboo arch structure.Parameter fitting is performed on the measured spectrum,and the accurate value of each parameter is obtained,which provides the basis for the reconstruction of the wind field around this type of structure;(2)Through hurst index calculation of wind speed data,it is found that the wind speed obtained during the monitoring period has long range positive correlation and self-similarity,and belongs to “1/f fluctuation”;(3)The response extremum of the structure during the monitoring period is analyzed and the relationship between the mean wind speed and the root mean square of acceleration response is fitted.It is found that the relationship between the two parameters are linear;(4)The Z-direction and X-direction fourth-order and Y-direction first-order modes of Bamboo Arch Pavilion are identified.The analysis frequency found that the out-of-plane stiffness of the round bamboo arch structure was greater than the in-plane stiffness,and it was more likely to cause in-plane vibration under the action of dynamic loads;the analysis of the damping ratio found that the damping ratio had a larger dispersion,distributed between 0.5% and 4.5%,belongs to the small damping,the energy consumption capacity of the structure is weak;(5)The modified finite element model is obtained,which can be used as a platform to detect the damage of round bamboo structure and analyze the damage degree of structural components and joints of round bamboo.The wind effect and dynamic characteristics of a large-span bamboo arch structure is studied for the first time in the thesis.The wind effect,vibration characteristics,modal parameters and model corrections obtained in this research can be useful for the design、construction and health monitoring of the large-span bamboo arch structure.