Damping Characteristics Of Architectural Coated Fabric And Its Influence On The Vibration Response Of Membrane Surface

As the core component of membrane structure,membrane material plays an important role in the performance of the structure.The membrane material is a typical viscoelastic material with the characteristics of ideal viscous liquid and elastic solid at the same time.In engineering construction and application,the mechanical characteristics of membrane materials are complex,and they will inevitably be subjected to dynamic loads such as external hail loads,wind loads and their attached impact objects.And then it causes the vibration of membrane surface in the structure.The membrane surface is deformed or even damaged,which affects the safety and normal use of membrane structure.In the current design,the linear elasticity hypothesis is mostly used to describe the constitutive behavior of coated fabric membrane under static load.It rarely considers the dynamic viscoelasticity of the coated fabric membrane material,so it cannot truly reflect the actual behavior characteristics of the membrane surface.On the other hand,it increases the deviation of membrane structure design.In order to ensure the safety and reliability of membrane structure in service period,it is necessary to deeply grasp the dynamic mechanical properties and damping energy dissipation mechanism of membrane materials in different environments.Furthermore,the influence on the membrane vibration response is discussed.Therefore,this paper uses a combination of material testing,structural test,theoretical analysis and numerical simulation to study the viscoelastic properties of coated fabric membranes and their influence on the vibration response of the membrane.The specific research contents and conclusions are as follows:(1)Dynamic mechanical properties of coated fabric.The dynamic viscoelasticity of coated fabric in different environments was analyzed by dynamic thermomechanical analyzer(DMA).The effects of constant temperature,dynamic temperature,and external load frequency were discussed,and the anisotropy of the membrane material in the warp and weft was considered.The results show that the storage modulus,loss modulus and loss factor increase with the increase of external excitation frequency.The loss factor is more sensitive to temperature at the same excitation frequency.Dynamic temperature and constant temperature have a great influence on the damping parameters of the membrane material.In general,the result of constant temperature measurement will float around the result of dynamic temperature measurement.(2)Dynamic viscoelastic constitutive model of coated fabric.Based on the damping constitutive relation theory of viscoelastic materials,the dynamic viscoelastic behavior of coated fabric is analyzed by using Maxwell model,Kelvin model and their respective extension models.Furthermore,the applicability of the fractional derivative model to describe the damping performance of membrane materials is discussed.The results show that the generalized Maxwell viscoelastic model and fractional derivative Kelvin model can be applied in low temperature and frequency domain,and it is feasible to describe the viscoelastic constitutive relationship of membrane materials.(3)Excitation vibration test of plane tensioned membrane structure.The design carried out the free fall excitation vibration test of the planar tensioned membrane structure,mainly considering the influence of the excitation amplitude,initial prestress,excitation point and other factors.The vibration response and energy dissipation mechanism of the planar tensioned membrane structure under different working conditions are discussed.The results show that under the external load,the membrane surface diffuses around the excitation point,and then causes the structural vibration.This is accompanied by energy consumption.When the initial prestress is low and the excitation energy is high,the vibration response of the structure is significant.The period of membrane vibration depends on the initial prestress,and it is not affected by the excitation load.(4)Verification of the viscoelastic model of the membrane material and its application in the open saddle membrane structure.With the help of finite element method,the viscoelastic constitutive model of coated fabric is implanted.The rationality and applicability of viscoelastic constitutive model of membrane under dynamic impact load are verified.The open saddle membrane structure model was established by form-finding analysis by programming method.Then,the modal analysis of the structure and the discussion of the vibration response under dynamic wind load are carried out.The results show that the modal frequency of the structure is lower due to the viscoelasticity of the membrane material.Under the action of dynamic wind load,the viscoelastic model produces more energy consumption than the elastic model.The membrane surface vibration has a large attenuation.The amplitude reduction factor under full load is 0.791.However,the reduction factor for uniformly distributed alternating load on the 1/4 membrane surface is 0.519.In addition,it is easy to produce stress concentration at each support of membrane structure,which needs to be strengthened in structural design.There are 74 pictures,9 tables and 154 references in this paper.