Research On Integral Equation Method For Moving Load Identification Based On Virtual Work Principle

Due to environmental erosion,material resistance attenuation,natural or manmade disasters and other factors,the risk of building structures facing safety problems increases significantly with the increase of the service life of the structure.Accurately obtaining the external load of the structure,long-term stress state assessment and health monitoring of the structure are effective means to ensure the safe service of the structure.The direct measurement of loads has great limitations due to factors such as the structure being in working state and the unreachable load measuring points.Therefore,load identification is the key research content of structural health monitoring.Based on the differential equation of structural motion,the stability of load identification and the robustness to noise need to be further improved by using differential time-domain algorithm or frequency-domain deconvolution algorithm.In this paper,by introducing virtual functions,the integral equation of structural motion is established based on the principle of virtual work,the integral equation is used to reduce the structural response types of integral equations,the load identification problem is transformed into an algebraic equation solution by the integral equation,and the displacement response or acceleration response is collected to identify the structural moving load..The influence of parameters such as modal truncation number,sampling frequency,integration interval,and virtual function type on the identification effect of moving loads is analyzed.The algorithm proposed in this paper is used to identify the axle contact force and the elevator guide rail-guide shoe contact force.Research indicates:(1)The integral equation method for moving load identification based on displacement response has a good identification effect on the simply supported beam model under noise conditions such as constant load,harmonic load,and triangular wave load when the signal-to-noise ratio is 20.The load identification effect under low speed conditions is better than that under high vehicle speed conditions.There are optimal sampling frequency and modal truncation number in the identification process,and the optimal modal truncation number can be selected according to the energy norm.There is still a good recognition effect on continuous beams,and the load recognition accuracy on simply supported beams is better than that on continuous beams.(2)The integral equation method for moving load identification based on acceleration response has a good identification of constant load,harmonic load and triangular wave load on multi-degree-of-freedom systems,simply supported beams and continuous beams when the signal-to-noise ratio is 20,etc.Effect.In a multidegree-of-freedom system,the accumulated error caused by noise can be eliminated by a high-pass filter.In the numerical simulation of simply supported beams and continuous beams,the recognition speed based on acceleration response is faster than that based on displacement response,the recognition curve is smoother,and the robustness to noise is better.(3)The two moving load identification integral equation methods can effectively identify the axle contact force and the guide rail-guide shoe contact force in the axle coupling system and the elevator car system.The two methods in the vehicle-axle coupling system have better contact force identification results in the uniaxial springmass system,and the smaller the road surface roughness,the better the identification effect.In the identification of elevator guide rail-guide shoe contact force,the identification speed based on acceleration response is faster than that based on displacement response.Through the simplification of the calculation model,the contact force and roughness function of the guideway-guide shoe under different noise conditions are well identified by using the acceleration response of the partial degrees of freedom in the car.