The Fast Test Method Of The Small Span Bridges Based On Statistical Moment

Nowadays,China is a country of bridge power,but most of the bridge being used in our country have injured and damaged more or less,and whose bearing capacity has a certain reduction,which is difficult to meet the current serious traffic situation.it will cost quite a lot to demolish and reconstruct all these diseases bridge,that is the reason why old bridge reinforcement is mainly used,and the bridge inspection for old bridge reinforcement and maintenance scheme and appropriate method is also the point.Therefore,there is great significance to study the application of bridge detection technology.However,the load test method is usually used in the bridge detection at present,which is carried out under the premise of the interruption of traffic,and it will result in a certain amount of traffic congestion caused by the interruption of traffic.Therefore,how to conduct the method of bridge detection under the premise of uninterrupted traffic will have the great significance.Therefore,this paper use the method of statistics.Firstly,we can get the model of vehicle load on the bridge structure by statistical analysis.And then,deducing the sum of each piece of beam deflection of the bridge is a fixed value under vehicle load.Next we establish the damage and undamage the Midas model,analyzing the sum of deflection of the bridge under the vehicle load in the Midas model.Finally,we will do field experiment.The main contents of this paper are as follows:(1)According to the deflection formula f ×P.k,it is found that the deflection of the bridge is related to the stiffness coefficient of the bridge under traffic load.In fact,the daily vehicle load will meet a certain probability distribution,under this kind of distribution of the traffic load,the deflection also belong to a certain distribution result.If the distribution of vehicle load is the same in a period of time,and the results of deflection obtained by this time also belong to the same distribution,it is considered that the stiffness of the bridge does not change,that is to say the bridge structure has no damage;on the contrary,if the deflection does not belong to the same distribution,that is the stiffness of bridge changed,and the bridge structure have some damage.Verifying whether the distribution is same or not can be achieved by K-S test.(2)Choosing the G6 Beijing-Tibet expressway,through using the statistical method to analysis the vehicle load which is located in Gansu Province in January 2015,the daily distribution function can be obtained,that is mainly composed of small vehicles,medium and large vehicles,it presents three peak distribution.We use a extreme value type I and two normal distribution the weighted sum to fit the probability model of the distribution of three peaks.Then we do K-S test for the fitting results and actual results,between the fitting result,the inspection results show that the fitting of the results can represent the actual distribution of three peaks,at the same time every day belong to the same vehicle load distribution.This eliminates effects because of the different vehicle load distribution in working days,weekends and national statutory holidays.(3)Because of the multiple beam box girder structure usually used in the expressway bridge,which will get the corresponding deflection on each beam under the vehicle load,This paper use the rigid beam method and hinged plate method to derive the sum of the deflection under different conditions which the bridge structure whether damage or not.The results show that no matter what kind of situation,the sum of the deflection is a fixed value,namely the sum of every piece of beam deflection is not changed when the vehicle load has changed in the bridge transverse position.(4)The vehicle load of the G6 Beijing-Tibet expressway in January 2015 act on the intact Midas bridge model,the 10% damage model and the 20% damage model,after statistics the sum of deflection at 0.01 mm to K-S testing,it can be seen that the inspection result is not through the inspection standards,shows that the sum of the deflection does not belong to the same distribution,namely has a certain bridge structure damage,verifying the method(1)is feasibility.(5)According to Laohutaizi l# bridge and Laohutaizi 2# bridge of G6 Beijing Tibet expressway,Using photoelectric measuring instrument to measure the total deflection under actual vehicle load within one week in February and march.Through the K-S testing,the results through the inspection standards,this shows that the bridge damage did not occur within a month.