Study On Dynamic Response Of Orthotropic Saddle Membrane Structure Excited By Hailstone And Rainfall Loads

With the rapid development of Engineering Materials Science and modern architectural structure technology,membrane structure architecture is more and more favored by architects.Although membrane structure has many advantages,it has light weight and small rigidity,so it is very sensitive to the impact load(such as wind,rainstorm,hail,wind debris,etc.).Under the action of load,it is easy to produce large vibration deformation,resulting in relaxation,fold and damage of membrane structure,even leading to engineering accidents.At present,the dynamic response of membrane structures is mainly concerned with the wind-induced dynamic response and the impact of mask structure.The research on the impact load of space membrane structure by theoretical analysis has not been reported.In this paper,the orthotropic saddle membrane structure,which is widely used in engineering,is taken as the research object.Through theoretical analysis,numerical simulation and experimental research methods,the dynamic response of the structure under hail and rainstorm loads is analyzed.The laws are summarized to reveal the disaster causing mechanism of the membrane structure and provide theoretical basis for the design analysis and construction of the membrane structure,so as to achieve the purpose of disaster prevention and mitigation.In the analytical theory,the orthotropic and large deflection of membrane materials are considered.The governing equations of the forced vibration of orthotropic saddle membrane structure under hail impact load and rainstorm load are established by using von Karman’s large deflection theory and darlambert’s principle.Through the simplification of Galerkin method,KBM perturbation method and free parameter perturbation method are used for approximate solution.In the case study,the dynamic response results of hail and rainstorm are analyzed in detail with the load,rise span ratio of membrane surface and pretension level as the variable parameters.ANSYS / LS-DYNA finite element analysis software is used to simulate the dynamic response of saddle membrane structure under the impact of hail,and the numerical simulation results of the dynamic response of membrane surface are obtained.The dynamic response data of the saddle membrane structure under the rainstorm load are obtained by the rainstorm impact test.The results of analytical theory,numerical simulation and experimental research are compared and analyzed.The main conclusions are as follows:1.Although hail and rainstorm load will not directly lead to material damage and structural instability of membrane structure,it will lead to large deflection displacement and strong nonlinear vibration of membrane structure.With the increase of load,the amplitude of membrane surface increases significantly,but the increase of load has little effect on the frequency and period of vibration.Through the analysis,it is found that the lower vibration frequency is harmful to the stability of membrane structure,so the low frequency vibration should be considered in the calculation of membrane structure.2.Compared with the increase of membrane pretension,the decrease of membrane rise span ratio has more significant effect on membrane amplitude and period.Therefore,in the preliminary design stage of membrane structure,we should try to use a large ratio of membrane to plane rise to span,so that it has a strong resistance to load and vibration.When the rise span ratio of membrane structure is determined,increasing the pretension level is helpful to resist the external load and suppress the vibration.3.The membrane structure should maintain a high and stable tension during operation and maintenance to reduce stress relaxation and plastic deformation of membrane surface.Under the action of load,the relaxation of membrane surface will reduce the critical wind speed of membrane structure,so after bearing the external load,the pretension level of membrane structure needs to be tested and re tensioned.