Wind-induced Coupled Vibration Analysis Of Large Tree-Frame Structures

With the acceleration of urbanization and the gradual improvement of people's demand for green ecological environment,although many large-scale trees have been planted at home and abroad,and good environmental and social benefits have been obtained,there is no coupled vibration mechanism of tree-structure system.The influence of large-scale trees on structural vibration under wind load(especially under strong wind)is rarely involved.Therefore,in combination with the large-scale tree-structure coupling wind-induced vibration problem in the large-scale tree greening project of the transportation hub of Guangzhou Baiyun International Airport Expansion Project,the coupled vibration mechanism of large-scale tree-structure system is adopted.The load transfer mode of large-scale trees and structures under windinduced vibration holds that the soil is equivalent to the horizontal and rotating spring damping unit.The simplified calculation model of the large tree-structure is proposed,and two examples are used to calculate the ground motion response analysis considering the SSI effect by MATLAB to verify the accuracy of equivalent spring damping unit of the soil.Based on the equivalent method of soil and software ABAQUS,a three-dimensional solid finite element model of large-scale tree-arbor pool structure was established to analyze the deformation of large trees,the response of spring damping unit and the internal force of arbor pool structure;from the single tree-arbor pool structure model to the overall frame structure model of 16 large tree clusters,five models are established for the overall frame structure of 16 tree clusters for modal and response contrast analysis,and the wind-induced coupled vibration mechanics response analysis of large tree-frame structures is further carried out.The results of this study can provide a reasonable and simplified design for large-scale tree-frame structure wind-induced coupling analysis as a reference and technical support.The work carried out in this paper and the conclusions reached are as follows:1.The soil equivalent horizontal and rotating spring damping system,considering the SSI effect equivalent single degree of freedom method to solve the interaction between soil and structure,combined with the proven method and applied to the SSI ground motion response analysis.The basic frequency of the SSI system is reduced,and the basic period of vibration is prolonged.The response of the parameter SSI system increases first and then decreases with the increase of the weight ratio of the upper structure,and decreases with the increase of the shear wave velocity of the soil.In the large-scale tree-soil-structure system,the soil can be simplified as a spring damping system to reflect the load transfer of trees and structures under wind load2.Based on the verified tree trunk model,a large tree-arbor pool structure model was established based on ABAQUS,and wind-induced response analysis was carried out for largescale tree-arbor pool structure under wind load design.The wind-induced vibration response of the arbor pool under different parameters,such as soil type,canopy form,trunk height,different wind speed and elastic modulus ratio of the tree material,is discussed.It shows that the soil type is from I to IV,and the dynamic response of the arbor pool structure is increased.The dynamic response of the tree to the arbor pool structure in the shape of the cylindrical canopy is greater than the truncated cone and then greater than the conical crown;the height of the tree trunk,the ratio of the elastic constant of the tree material and the increase of the wind speed increase the response to the arbor pool structure.3.From the vibration response analysis of single tree-arbor pool structure under wind load,the vibration response of 16 tree clusters-frame structures under wind load is further analyzed.ABAQUS model of solid element large-scale tree-beam shell element frame structure(model 1);ABAQUS model of beam shell element large-scale tree-frame structure(model 2);SAP2000 model of space bar member element large-scale tree-frame structure(model 3);a simplified model for extracting the base shear and bending moment from the frame structure of the third layer after receiving the wind load on the tree(model 4);the large-scale tree is equivalent to SDOF,and add SDOF to each tree pool of framework model on the third floor(model 5).Comparison of modal and response analysis of five large tree-frame structural models shows that the result error of simplifying trunk into load form is about 10%,and the model 4 is the most reasonable.4.According to the comparison of three large tree-frame structure models response,taking model 1 and modal 4 as analysis objects,the model 1 is taken as the analysis object,and the five parameters of soil type,tree crown form,tree trunk diameter,tree elastic constant ratio and tree damping ratio are discussed.It shows that the soil type is from I to IV,and the dynamic response of the overall frame structure increases;the dynamic response of the tree to the overall frame structure in the cylindrical canopy form is greater than that of the truncated cone,and then greater than the conical crown form;with the increase of the tree's own damping ratio to the overall frame,the response of the structure is reduced;the ratio of the diameter of the tree trunk to the elastic constant of the material increases,and the response to the overall frame structure also increases.