Research On Finite Element Modal Updating Damage Identification Method Of Simply Supported Concrete Beam Under The Influence Of Temperature

With the rapid development of national economy in our country,there's been a dramatic improvement in bridge engineering.Bridges play an important role in the transportation system,ensure the safety of bridge structure which is used for the development of national economy and people's life and property security of great significance.Bridges are in the process of operation,however,inevitably affected by long-term load and environmental factors,leading to structure damage and even they collapse.A large number of research results show that the environmental factors,especially the temperature will cause a significant change in bridge structure dynamic characteristics,which may hide the influence of the structure damage on the dynamic characteristics,therefore,studying the effect of temperature on modal parameters of bridges,and under the influence of temperature and putting forward effective damage identification method has an important practical significance.Long-term monitoring of a reinforced concrete beam was presented in this paper.Based on the distribution of temperature field in concrete beam characteristic,the mechanism of the influence of temperature on modal parameters is analysed in theory.Through finite element method to build the benchmark model,it realized damage identification based on the finite element model updating under the ambient temperature influence.This paper's main research contents are as follows:1?Through the long-term monitoring of simply-supported concrete temperature field outside,it revealed the rule and influence mechanism of environment temperature on the modal parameters change of simply supported concrete beam.Through the analysis of the measured temperature data,it clarified the negative correlation between modal frequency variation and ambient temperature field distribution of simply supported beam,indicating the temperature mainly by changing elastic modulus of concrete which result in the change of modal frequency.2?Simply supported beam model was established using the finite element analysis software ANSYS to simulate actual temperature field,theoretically studying the influence of uneven temperature distribution on the modal frequency,and reference model was constructed under the temperature field which was known.Then,modal frequency calculation method was analyzed under the condition of known ambient temperature field.3?Flexibility matrix which is extremely sensitive to the damage was used.Flexibility residual concept was put forward and it was regarded as objective function,using the measured modal data and finite element model to calculate the modal information to calculate flexibility residual,model updating method based on combining sensitivity and Tikhonov regularization method was used.Modify the elastic modulus value of concrete making the flexibility residual values of each node close to zero,thus making the finite element model consistent with the actual structure.4?Finally,flexibility difference curvature was used to identify damage location and quantification,finite element model of simply-supported concrete was used for simulating different damage locations and degrees of damage.Through numerical simulation,the results showed that this method can effectively identify structural damage location and realize damage location.