Study On Nonlinear Vibration And Probabilistic Evaluation Method For Wind Resistant Performance Of Flat Membrane Roofs

Membrane structures usually produces large deformation and vibration under wind load for its light and flexible,This large deformation and vibration will in turn affect the air flow field around the structure,thus forming the Air-structure coupling effect,which will lead to the change of membrane vibration characteristics,and even lead to aeroelastic instability in the initial design defects of the membrane structure.Aeroelastic instability is a serious threat to wind-resistant safety of membrane structures,so the study of aeroelastic instability is always one of the hot topics in wind-resistant design of membrane structures.Because of the complexity of mechanical properties of membrane structures,especially the obvious geometric nonlinearity of membrane vibration,the theoretical work in this field was mostly based on the hypothesis of small deformation in the past.In addition,the destruction of membrane structures under strong wind occurs frequently in recent years,indicating that there are some deficiencies in the theory of wind-resistant design of membrane structures at this stage.Therefore,engineers need a simple and applicable evaluation method to evaluate the wind resistance of membrane structures.Therefore,This paper is devoted to studying the nonlinear vibration characteristics of flat membrane roofs,searching for theoretical methods suitable for solving the nonlinear vibration,and applying them to the windresistant design of membrane roofs to obtain the transcendental probability of different wind-resistant performance levels under a given field,so as to evaluate their windresistant capacity.This article has carried on the related research from the following five aspects,the main contents are as follows:(1)Analytical method for nonlinear vibration of membrane roofs: In view of the limitation of traditional perturbation method which only aims at solving small parameter vibration equations,this paper improves the multi-scale method,introduces transformation parameters,and solves the membrane nonlinear vibration equations with large parameters analytically.The orthogonality of membrane materials and the orthogonality of membrane materials are considered in the study.Damping coefficient.By comparing with the traditional perturbation solution and numerical solution,the accuracy and applicability of the solution method are determined.(2)Suggestions for the maximum initial stress of roof membrane tension: The greater the pre-tension,the greater the stiffness of roof membrane surface,but it is accompanied by the increase of construction cost and stress relaxation during normal use.Therefore,through the impact test of flat rectangular tensioned membrane,the deformation attenuation rate of impact displacement of membrane under various tensions is studied,and the maximum initial stress of tensioned membrane is suggested.At the same time,the influence of orthotropy on the vibration amplitude of membrane material is analyzed by collecting vibration data from different measuring points.(3)Aerodynamic effects on membrane nonlinear vibration: membrane vibration in the air will drive the surrounding air movement,the air flow field after the movement will react on the membrane,changing its vibration characteristics.Based on the principle of energy conservation and aeroelasticity,the additional aerodynamic force of membrane roof vibration in air field is solved analytically in this paper.On this basis,the influence of additional aerodynamic force on the vibration frequency and amplitude of membrane material and the effect of wind speed and initial Pre-tension on the additional aerodynamic force of membrane roof are discussed.Ringing.(4)Design parameters of membrane roof to prevent aeroelastic instability: The main reason of aeroelastic instability is the insufficiency of pre-tension and the unreasonable span of membrane element.The critical wind speed of aeroelastic instability is solved by the improved multi-scale method,and the relationship between the critical wind speed and membrane pre-tension and span ratio is obtained,so as to obtain an underground instability.Minimum pre-tension,span ratio requirements corresponding to design wind speed in the same recurrence period and other layout principles to prevent aeroelastic instability.(5)Probabilistic evaluation method for wind resistance of membrane roofs considering aerodynamic stability: Wind resistance of membrane roofs in a given field is evaluated from the perspective of probability.Based on the concept of performancebased structural design,a performance-based probability evaluation framework for flat membrane roofs is established by simplifying the mathematical model of wind field.The annual average transcendental probability is used to quantitatively evaluate the wind resistance of the structures.In the evaluation process,considering the effect of additional air quality on the wind-induced vibration of roof,the wind-resistant capacity of roof under different performance levels can be obtained accurately and quickly.