Research On Damage Identification Of Bridge Structure Based On Measured Displacement Influence Line

The unit concentrated load moves along the structure,indicate a pattern of the change of quantitative value called the influence line of the quantity.Establish an observation point on the bridge,when the concentrated load moves on the bridge,the displacement observation value of the observation point is measured,the displacement variation is called the displacement influence line of bridge.The displacement influence line can reflect the global information,and can solve the problem of incomplete information in bridge damage identification.Most of the existing research on the damage identification by using the displacement influence line after the fitting,the damage index is established by using the influence line data before and after structural damage.Most of the existing research on the structure detection of the bridge by the inclination angle is based on the function relationship between inclination angle and deflection,through the calculation of the deflection data of the structure to achieve the purpose of structural detection.Few the direct use of the structure of the tilt angle to achieve the bridge damage identification detection research.In recent years,with the continuous development of the inclinometer and the continuous improvement of measurement accuracy,it is possible to identify the damage of the bridge directly by using the real value of structural dip.According to the displacement influence line theory,a bridge damage identification method based on the difference curvature of the multiple measuring points displacement influence line is proposed,to realize the damage identification of the bridge structure under the condition of unknown initial data;presents a method of damage identification based on the angular influence line,and the structural model is established by numerical simulation and finite element method,carry out the damage identification analysis of the structure,and verify the validity of the damage identification index.According to the characteristics of the displacement influence line,the measured displacement influence line measured by the sensor is analyzed,and the damage identification method based on the measured displacement influence line data is established.Through the core operation,the damage point is output finally,to complete the damage identification of bridge structure.The main work is as follows:First,this paper deduces the formula of the difference curvature of the multiple measuring points displacement influence line of simply supported beam bridge,in addition,the damage identification of the simply supported beam bridge with different measuring points,different degrees of damage,different damage location and Multiple damage is analyzed.It is concluded that the difference curvature of the influence line of multiple measurement points in damage section is only related to the damage degree and the damage location,which can be used for the damage identification of simply supported beam bridge.Second,in order to verify the applicability of the damage identification index,a numerical analysis model is established to study the damage identification of a fixed end beam and three span continuous box girder bridge.Selecting the appropriate position of the measuring points,the difference curvature index of the multiple measuring points displacement influence line can be used to identify the damage of the continuous beam bridge structure,can clearly identify the damage location.Third,The definition of the concept of the angular influence line of simply supported beam bridge,the formula of the angular influence line of the simply supported beam bridge is deduced,put forward the damage identification index based on the difference and difference curvature of angular influence line before and after the damage of simply supported beam bridge and the formula is derived.The finite element model of simply supported beam bridge structure is established and analyzed.The damage identification of simply supported beam bridge can be realized by using the difference of the angular influence line before and after the damage.The peak value of the difference curve in the damage area and have good damage identification effect.The value of difference curvature of angular influence line before and after the damage of simply supported beam bridge is 0 and in the damage area was not 0,in view of the above to identificate the damage of simply supported beam bridge structure has high accuracy,damage identification can be performed for single and multiple damage.Fourth,The theoretical analysis of the angular influence line of the non-idealsupport beam structure is carried out,the theoretical formula of the angular influence line of beam structure with rotating elastic support is derived,this paper establishes the foundation for the application of the angular influence line in bridge damage identification.Fifth,a new method for damage identification of bridge structures based on the measured displacement data is proposed by combining the displacement influence line damage identification method with artificial neural network.A simple supported beam bridge is taken as an example to analyze the damage identification,and for distinguish the damage location and damage degree have small error by using this method.It lays the foundation for the intelligent development of the theory.