Based On Strain Mode Bridge Damage Study

Nowadays,China's bridges and viaducts have begun to carry out largescale construction.Bridge is an indispensable part of the traffic engineering,its healthy development can speed up the economic development of our country and promote the livelihood of the people.Strain modal is a key parameter for bridge structural health monitoring,which is important not only the variation of the stress and strain of bridge structure,but also in the process of bridge damage identification.Strain modal is sensitive to the local characteristic response of structure,once damage is appeared in bridge,the stiffness in the damage location will decline,leading to a reduced stiffness on the strain modal curve.Therefore,it is necessary and feasible to conduct strain modal analysis to discover the bridge damage.The thesis is carried out mainly from the following aspects:1.The problems of the operation of existing bridges are analyzed through on-site exploration and theoretical analysis.2.The strain modal solution method is deduced based on the relationship between displacement modal and strain modal.Besides,the orthogonality has been validated.The relationship between strain modal and displacement modal strain is derived by modal analysis of existing error process.3.Based on finite element software,a simple continuous beam model is established,by reducing the stiffness of different units to simulate the bridge damage and analyze the natural frequency changes.Using the continuous beam model,the strain mode can not only recognize the single position damage,but also can effectively identify the damage of multiple positions.4.Some corresponding sensors have been installed on bridges to measure the bridge dynamic strain and acceleration which can used to solve the bridge strain modal.In addition,compared with the finite element simulation under the bridge intact state the damage situation of bridge is determined.