Bridge Damage Identification Based On The Difference And Curvature Of Influence Lines Of Symmetrical Measuring Points

As an important part of the road traffic system,the safe service of bridges is very important.As the traffic load continues to increase,most bridges have experienced varying degrees of damage and deterioration,and some damages directly affect operational safety.In recent years,bridge safety accidents have occurred frequently,which not only caused a lot of loss of life and property,but also caused social panic.Therefore,it is extremely important to carry out research on bridge health monitoring and damage identification.Based on the current research status of bridge damage identification,and on the basis of previous studies,this paper uses the influence line as the starting point,and proposes to use the displacement and corner influence line difference and the difference curvature of the symmetrical measuring point as the damage identification index.The main research contents are as follows:(1)In the elastic range,according to the principle of virtual work,derive the difference expression of the displacement influence line of the symmetric measuring point of the simply supported beam under the moving load,and then find the curvature of the difference,according to the displacement influence line difference of the symmetric measuring point Locate the damage location and locate the damage interval based on the difference curvature.Numerical simulation was carried out by using a simply supported beam to simulate various damage conditions located in different areas of the measuring point.(2)Establish a three-span continuous beam,study the damage identification of continuous beam bridges based on the difference of the displacement influence line of the symmetrical measuring points and the curvature of the difference,and arrange two sets of symmetrical measuring points located in different areas of the continuous beam to identify different areas of the continuous beam For different working conditions such as single damage and multiple damages,the feasibility and applicability of indicators in continuous beam damage identification are studied.The results show that the symmetrical measuring points located in the side span area of the continuous beam are more sensitive than the symmetrical measuring points in the middle span area.(3)In the range of elasticity,based on the principle of virtual work,derive the difference expression of the influence line of the symmetrical measuring point of the simply supported beam under the moving load,and use a simply supported beam to carry out the numerical simulation and simulate the different measuring points.Multiple damage conditions in the area.(4)Taking the single box girder of the small box girder as the background,the proposed method is used to verify the damage identification.Simulating multiple damage conditions,the damage location of various damage conditions of small box girder can be accurately identified.Then the damage degree is inverted.As the damage degree continues to increase,the accuracy of identifying damage continues to increase.The accuracy of damage identification is also closely related to the location of the measuring point.Symmetrical measuring points can be arranged reasonably according to the actual damage of the bridge.If conditions permit,multiple groups of symmetrical measuring points can be arranged for damage identification.(5)The method proposed in this paper is verified by the indoor simply supported beam damage diagnosis test,and the moving load loading and the quasi-static loading are carried out respectively.Moving load is used to identify the dynamic influence line of any measuring point of the bridge,and the quasi-static load is used to obtain the quasi-static influence line of the symmetric measuring point.Then,the damage is located based on the difference of the quasi-static displacement influence line of the symmetrical measuring point,and the damage interval is identified by the difference curvature value.