Fatigue Performance Study Of Prefabricated Prestressed Concrete Box Girder Bridge Under Overloading

Prefabricated prestressed concrete box girder bridge is one of the main bridges of medium span beam bridge on the highway in our country. Along with the rapid development of modern transportation and regional economy, the characteristic of overload transportation is more and more significant. And part of the highway actual operation vehicle load has exceeded the design load value. So the fatigue damage of prefabricated prestressed concrete box girder bridges has become a problem can not be ignored. Based on the original data of the weigh-in-motion (WIM) system and structural health monitoring (SHM) system, fatigue performance of prefabricated prestressed concrete box girder bridge under overloading is studied It has important theoretical significance and engineering practical value. The main work is as follows:(1) Based on a total of 23.24 million vehicles raw data of Xinyihe bridge WIM system from May 2012 to December 2015, fatigue load spectrum and standard fatigue car of all vehicles and overloading vehicles (greater than 55 tons vehicles) were studied.(2) Based on the raw data of Xinyihe bridge SHM system from October 2014 to April 2016, the fatigue life of steel plate at the bottom of box girder of Xinyihe bridge middle span was evaluated.(3) Based on the vehicle original data of WIM system and the ANSYS model of Xinyihe bridge, the fatigue life of the left picture, right picture before and after reinforcement of Xinyihe bridge was evaluated.(4) Based on the fatigue cumulative damage model and Monte Carlo fatigue analysis method, the fatigue life of the left picture, right picture before and after reinforcement of Xinyihe bridge was evaluated.The main conclusions are as follows:(1) Based on all vehicle data of WIM and 4.36 million overloading vehicles (greater than 55 tons vehicles) data, probability distribution model of vehicle weight, gap and headway of the actual vehicle is established.(2) Based on WIM monitoring information, three types of fatigue load spectrums of Xinyihe bridge are established, which are fatigue load spectrum of nine models, five models and standard fatigue car.(3) Based on the monitoring data of SHM system, the fatigue life of steel plate at the bottom of box girder of Xinyihe bridge middle span is 140 years.(4) Based on the vehicle raw data of WIM system, the fatigue life of prestressed steel of the left picture is 79 years. The fatigue life of prestressed steel of the right picture before reinforcement is 10 years. The fatigue life of steel plate of the right picture after reinforcement is 146 years. The fatigue life of cable of the right picture after reinforcement is 104 years. And the fatigue life of prestressed steel of the right picture after reinforcement is 58 years. The damage caused by overloaded vehicles accounts for more than 88% of the total damage.(5) Based on the reliability theory, the fatigue life of the left picture, the right picture before and after reinforcement of Xinyihe bridge are 82 years,9 years and 55 years respectively. And it is consistent with the fatigue life which are 79 years,10 years and 58 years obtained from WIM. Three methods of fatigue life evaluation can confirm each other.