Study On The Vibration Reduction Model Of Urban Greening Trees Based On Periodic Theory

Urban trees are often planted in a periodic arrangement in space.This paper takes urban trees as large-scale natural phononic crystals.Based on the phononic crystal theory,a three-dimensional unit cell is used to rqpresent the entire forest and finite element analysis via COMSOL5.3a software is implemented to identify dispersion relationships.The surface-wave band gaps of urban forests are identified using the sound cone method and strain energy method.The influences of soil elastic modulus,tree spacing,trunk radius,and tree height on band gaps are discussed.Finally,a three-dimensional simulation model experiment test are applied to verify the effect of urban trees on vibration reduction.The results show that numerical frequency-reduction zones are consistent with theoretical surface-wave band gaps.An increasing soil modulus results in a wider and higher-frequency band gap.Urban forests with larger trunk diameters and smaller tree distance can generate lower-frequency and wider band gaps.It is beneficial to obtain low-frequency band gaps with increasing tree height.A manmade engineered array of trees can be designed with Rayleigh wave band gaps at a low frequency of ?80 Hz.This study provides a new concept for the quantitative design of urban forests to reduce ground vibration in specific frequency ranges.The main innovation:From the perspective of periodic structure(phononic crystal),a three-dimensional dynamic model of urban trees is established,based on the phononic crystal band gap calculation method in the microscopic field of material science and physics,a set of calculation and analysis methods suitable for calculating the vibration attenuation zone of large-scale periodic forest are proposed Through numerical simulation and outdoor experiment the calculation methods are verified,which provide the theoretical basis for quantitative design of urban forest.Through the study of the full text,the reasonably designed urban forest can be used as a vibration isolation barrier to effectively reduce traffic vibration,and enhance the ecological service function of urban forest.The research results of this paper can be directly applied to the improvement of urban ecosystem function in Beijing,and also have extremely important application potential in the urban ecological construction of Xiongan New District.