Study On Dynamic Response Of Saddle Membrane Structure Under Hail Impact

As a new type of spatial structure,membrane structures have been widely used in large span space structures,such as stadium,exhibition field and railway(bus)station,because of its excellent architectural characteristics,excellent structural characteristics and suitable economy.Due to the characteristics of light-weight and long-span,the membrane structures are sensitive to external loads,resulting to larger vibration deformation which should be avoided in the use of membrane structures.However,at present,the theory of membrane structures design is still at the stage of gradual accumulation and perfection.This paper mainly studies the dynamic response of the saddle membrane structure under the impact of hail,which can provide a theoretical basis for the rational consideration of the adverse impact of the hail impact load in the theory of membrane structure design.In addition,the general rule of dynamic response of membrane structure is applied to guide the construction and maintenance of membrane structure.It also has great practical significance in guaranteeing the normal use of membrane structure,prolonging its service life,and preventing or reducing the occurrence of engineering accidents.In this paper,the dynamic response of typical four-point saddle membrane structures under hail impact is numerically simulated and experimentally studied.Firstly,the form-finding analysis for four-point saddle membrane structures are done by using the finite element analysis software ANSYS to obtain the initial shape of the saddle surface.Then,by using LS-DYNA explicit dynamic analysis program,transient dynamic analysis is carried out on the complex mechanical process of hail impact on the membrane surface.In addition,the experimental study of hail impact saddle membrane structures is designed and implemented to verify the reliability of numerical simulation.The main contributions of this dissertation are as follows:(1)The plane projection geometry model of the saddle membrane structure is created by the finite element analysis software ANSYS.The initial pretension is applied to the surface of the saddle membrane structure by falling temperature method.And,the side cable tension is applied in the form of the initial strain.The form-finding analysis is made by the complex utilization of self-equilibrium iterative method for small elastic modulus surface and support displacement lifting method.Based on the above operations,the initial shape of saddle membrane structure can be obtained.(2)The implicit explicit sequential solution function of the LS-DYNA explicit dynamic analysis program is used.In numerical simulation,hail is regarded as a rigid body with initial velocity,moreover,the contact between the hail and the membrane surface is automatic contact on the surface.Then,the dynamic impact process of hail impacting the membrane surface is solved.Afterwards,the dynamic responses of the membrane surface are obtained by post-processing of the LS-PROPOST program.(3)Based on the designed saddle membrane structural tensioning device,an experiment on the impact of hail on the saddle shaped membrane is carried out.During the experiment,a non-contact laser displacement sensor was used to record the dynamic response of the characteristic points on the membrane surface.Then,the obtained experimental results are compared with the numerical simulation results to verify the accuracy and reliability of the numerical simulation.