Research On Deflection Characteristics Of Long-span PC Girder Bridge On Vehicle Or Temperature Load

Long span prestressed concrete girder bridges have boomed in recent years, butthe problem of bridges’ deflection in service has great influenced the comfortablenessof driving and the structural safety. The deflection reflects the bridges’ wholecharacteristics, which is the very important parameter in the health-state of existingbridges. The total deflection sigal can be viewed as the superposition of long-termdeflection, annual temperature difference effect, daily temperature difference effectand traffic loads effect, which is obtained by the real-time running state monitoringsystem. So it can correctly assess the work performance and evaluate the health statusof bridges during its service life by rejecting environmental factors effect only byobtaining the deflection characteristics caused by each individual factor.At present, the each individual factor bridge deflection is usually numericalsimulation,and lack of measured data, which may cause some difficulty to analysisdeflection characteristics and the cause of deflection; In practical engineeringapplications, the operating vehicle load exists variability and randomness，so it isdifficult to accurately calculate the value contribution of individual factor in thebridge deflection. Based on the difference of the frequency characteristic of the typeof deflection component, the field measurements and finite element calculationdeflection signal was analysed by using the vibration signal analysis method.This paper mainly completed the following research work:combined the fieldmeasurement test with the calculation of FEM, the deflection data for the backgroundof bridges under vehicle load and temperature load was respectively obtained, whenthe vehicle load deflection signal was acquired,random vehicle load spectrum can becreated through Matlab program by stochastically imitating the traffic flow, in order toanalyse the deflection schedule of the bridge background.The temperature deflectionmeans through bridge temperature field measurement,the girder vertical temperaturegradient mode can be reached, the deflection effects of contrasted bridges underdifferent temperature gradient role was calculated;Through contrasted the bridge fieldmeasurements and finite element calculation,the bridge deflection data was signalanalysed by using the time domain, frequency domain and wavelet analysismethod;Based on reliability theory and used the bridge deflection sampling frequencyestimation, the reliability of signal acquisition was researched and analysed by takingadvantage of the vehicle load deflection frequency domain characteristics.In this paper, results are as follows:（1）The error between simulation of vehicle load deflection calculated value and the statistics of the measured deflection value is less than2%, the error betweenthe calculation of deflection natural frequencies and the measured deflectionfrequency is within the3%, so it is feasible to adopt the long span PC girder bridgevehicle loads to analyse the structural deflection;（2）The frequency of the structure vibration energy range is obvious,and thepower spectral density curves in multimodal distribution,moreover,the amplitudespectrum is a bimodal distribution, it is mainly focused on the structure of the firstorder vibration frequency and the third order frequenc nearby;（3）The value of the fitting temperature difference distribution modeldeflection between the measured deflection is in good agreement; The bridgetemperature deflection data is a kind of day cycle steady state signal; The bridgemeasured temperature deflection signal vibration energy is mainly concentrated in thelow frequency range of0to the1Hz, and the first frequency is nearby0Hz;（4）The sampling frequency of the bridge dynamic monitoring is determinedby the operating vehicle deflection maximum frequency;The probability integrationmethod can be reasonably estimated the bridge deflection signal sampling frequency;The background bridge deflection sampling frequency from the third frequencies neartwice bridge structure can meet the requirements of practical engineering.