Model Test Based Vehicle Load And Seed Inversion Method

As transportation business booms over the recent decades,a variety of transporting vehicles have come into being,predominated by the heavy-load vehicles and trailers;meanwhile,there have been a growing number of overloading phenomena going beyond the bearing capacity of bridges,causing which to suffer premature damages or even collapses and severely shortened service lives.Therefore,how to identify the moving loads on bridges has been an important topic,which attaches vital significance to the routine maintenance,health monitoring and assessment of bearing conditions of bridges at the current stage.This paper mainly conducts a moving load identification using a simply supported T-beam organic glass model and the ANSYS software.On the basis of the dynamic strain response of the corresponding section under the bridge across which the vehicle is travelling,the vehicle weight is identified by adopting the maximum strain amplitude method and the area enclosed by the strain influence line.Below are the main contents of research in this paper:1.Select the common 40-meter simple T girder for roads,bridges and culverts in 2009 as the reference object.Dimensions of the section of the prototypical bridge are scaled down by applying the theory of similarity.Organic glass is selected as the test material.A representative section is selected to affix strain foils to.A self-dissembled DFL3251 AXB car of Dongfeng brand is scaled down in terms of sectional dimension and vehicle weight.The speed at which the car travels across the bridge is calibrated.A frequency transformer,engine,roller,pull rope,car,acceleration/deceleration zone and lead rail are adopted to collaboratively complete the car-cross-bridge test.2.The car is used to conduct a static load test to collect the static strains and initial finite element model,compute the static strains to form a contrast,and compute the errors between both.Relevant parameters of the finite elements are corrected,and parameters to be corrected are determined preliminarily.A method of forward and backward differences is employed to determine the sensitivity of the parameters to be corrected.A target function is established for optimization iteration.The numerical values of the parameters to be corrected are determined finally.3.A dynamic load test is conducted on the finite element model which has been corrected,as contrasted to the dynamic load test on the organic glass model.The errors between both are analyzed.The results of computation of both are associated to analyze the relation of influence on the strain time-distance curve at different vehicle weights,speeds and roughness of bridge.4.Inversion is performed on vehicle speed and weight.First,the vehicle speed is inverted by utilizing the rising and falling timespans on the time-distance curve of strain and the time interval between both sections when maximum strain emerges on the one-quarter and three-quarter sections.Next,the strain recognition curve and equation at known vehicle weight are established by the maximum strain amplitude method.Based on the theory of influence line,the area under the time-distance curve of strains is utilized to recognize the vehicle weight and determine the integral coefficient of strains at known vehicle weight and speed.Finally,the established strain recognition curve,equation and integral coefficient of strains are utilized for inversion of unknown vehicle speed and weight.