Study On The Whole Process Of Loading Experiment Of Prefabricated Prestressed Concrete Box Girder With Damage

With the rapid development of bridge construction in our country,the bridge structure style is becoming more and more abundant.Because of the characteristic of the large torsional rigidity and flexural rigidity,the low cost and the fast construction speed and so on,the assembled prestressed concrete box girder has been developed rapidly and widely used at home and abroad.Although the box girder has very good structural performance,there will be many diseases,such as concrete cracking,stiffness degradation,stress variation of prestressed reinforcement and so on in the process of operation.These diseases will directly or indirectly affect the usability,safety and durability of the bridge.Based on the shanxi project about communication science and technology entitled “reach on the working performance of prefabricated prestressed concrete box girder bridge with cracking damage”,and relying on the demolition and reconstruction project of Taihang bridge on the Li Cheng period of chang-han high-speed,this paper carries out the ultimate bearing capacity experiment for the 30-meter prestressed concrete box girder with cracking damage.Based on the data of the deflection,stress,crack development and load.etc of the box girder during the whole process of loading,the paper analyses generally the whole process,failure mechanism and failure characteristics of the damaged prestressed concrete box girder.By considering the material nonlinearity and geometric nonlinearity,the finite element model is established by ansys to get the theoretical value of deflection,strain and stress of the prestressed reinforcement.According to the measured crack information,the nominal tensile strain state of the concrete under the box girder can be obtained,and the stiffness reduction factor,the strain value,the stress of the prestressed reinforcement,the deflection value and so on are calculated by the method of section analysis and damage stiffness calculation.By comparing the analysis and evaluation,the feasibility of the method of damage stiffness calculation is verified.The results show that,coMPared with the experimental value,the results of the finite element calculation results and the damage stiffness calculation have the common development rule on the deflection,strain and stress of the prestressed reinforcement.The results of coMParative analysis of box girder with different damage degree also shows that,due to the different degree of initial crack damage of box girder,the crack of the box girder is earlier and the stiffness decreases rapidly under the experiment load,which causes the finite element results are less than the experimental values.CoMPared with the results of finite element analysis,the values of deflection,strain and stress of the prestressed reinforcement.which are calculated by the damage stiffness theory are closer to the experimental value.The results show that,the method of section analysis based on the damage stiffness calculation can reflect accurately the characteristics of the existing prestressed concrete beam with damage,which can be used to the analysis of the whole process of this kind of structure.