Dynamic Response Of Bridges Based On Blast Vibration Signals And Health Condition Assessment

With the continuous development of urbanization in China,the density of urban buildings is getting bigger and bigger,and some new construction projects often have to be close to existing buildings or intersect with existing buildings.In engineering construction,blasting operation as a common construction method has greatly improved the construction efficiency,while on the other hand,the vibration wave generated by blasting will affect the surrounding rock and buildings,and the safety hazards caused cannot be ignored.In this paper,the response law of a continuous box girder bridge under blasting load and the health state of the bridge are discussed and studied by combining theories of structural dynamics and numerical simulation with each other through finite element model and field experimental data in the context of actual engineering,and the main research contents are:(1)the blast vibration signal is analyzed by obtaining the measured data through field monitoring:firstly,the measured peak blast vibration velocity is analyzed by non-linear regression using MATLAB software to establish a prediction model of blast vibration velocity based on empirical data;then by performing Fourier transform on the vibration signal,it is studied that under the condition that the maximum singlesegment charge is determined,with the gradual increase of the blast center distance,the Fourier main frequency gradually decreases;Finally,wavelet analysis techniques are used to analyze the measured blast vibration data,the original signal of blast vibration is decomposed into eight different frequency intervals to explore the energy distribution of the blast vibration signal in each frequency interval.(2)In this paper,a continuous box girder bridge is used as the research background,and the finite element software Midas Civil is used to establish the bridge structure model and conduct numerical simulation.The coupling effect of blast vibration waves in three directions is the most unfavorable to the bridge structure.(3)Based on the fiber unit theory,the elastic-plastic dynamic analysis model of the bridge pier was established,and the axial force changes of the bridge pier under different amplitudes of blast vibration waves were studied.(4)To establish a bridge blasting seismic safety evaluation method based on the capacity demand ratio method(CDR method),the above-mentioned finite element simulation of the continuous box girder bridge under the actual blasting vibration waves,and calculate the capacity demand ratio of each part of the bridge pier,when the ratio is greater than 1,the bridge is in a safe state of blasting load strength;when the ratio is less than 1,the bridge is in a safe state of blasting load strength,this evaluation method can This assessment method can provide some reference for bridge health status assessment.