Research On Damage Identification Method Of Suspension Bridge Based On Dynamic Characteristic

The ground anchored suspension bridge is always being the preferred type when building a large span bridge which spans more than 1 km.It plays an important role of facilitating the social traffic,somtime even related to the national and social stability.Morever,the construction technology of the large span suspension bridge is complexed so thar the cost is high.Due to the flexible,dynamic responseis more significant to the whole structure than the static response.Therefor,using the dynamic characteristic parameter toidentify the structural damage is of great theoretical significance and a wide range of practical valueThe paper firstly elaborates the modal analysis method which is commonly used to structural dynamic analysis,including the modal analysis theory,the construction of the damage identification indices and the damage detection principle of the wavelet analysis.The paper based on a project named Qingcaobei bridge which main spanis 788 m is an anchored suspension bridge.Taking into account the anchored suspension bridge stiffened stiffning beam is usually lower than the stiffness of cable and pylon,the study focused on the stiffening beam damage identification.First of all,using the bridge design software Midas Civil to build the finite element analysis simulation model of the relying bridge and conducting the dynamic characteristics analysis.Then extracted the top 10 modal frequencies.Meanwhile,using the MATLAB to conducting spectrum analysis of the 1 hour continuous monitoring data.Comparing the results of FFT and finite element calculation shows the operation of bridge is in good condition,there is no obvious damage.Then,used Midas Civil to builde finite element model which the stiffening beam with simulating damage to conduct dynamic characteristic analysis.Extracted beam top 10 modal frequencies and modal shape,using central difference formula for approximate calculation of curvature to structue modal frequency difference,vibration mode difference,modal curvature differencefor damage identification.Resesearched on the damage identification sensitivity level of each index,the damage location accuracy and the relationship with damage degree.Results show that,the three damage indicators can identify damage and are correlated positively with damage degree.Modal frequency difference index is unable to locate damage,mode shape differential index has the possiblity of positioning error,modal curvature difference index can accurately positione injury.Finally,usingthe Guass2 wavelet basis function to processthe finite element damage vibrationdate andcurvature datadirectly,thus realizesthe damage identification and location work in the absence of original no injury data.