Research On Ultimate Bearing Capacity Of Prestressed The Small Box Girder By Experiment

In recent years,the structure of prestressed small box Girder Bridge has been developed rapidly because of its low construction height,large torsional rigidity,convenient prefabricated erection and material saving,and has become an important part of small and medium span bridges in China.With the rapid development of China’s economic construction,The phenomenon of overloading and overloading is increasing and the traffic pressure is increasing.prestressed girder bridge disease has been exposed in the actual operation process,so the measurement and evaluation to this kind of bridge has become particularly important.Further study of the stress of the bridge performance,damage condition,ultimate bearing capacity and safety stock has practical significance and important theory basis to later stage of operations and the safety of the bridge detection evaluation.In this paper,through study of the ultimate bearing capacity test of prestressed small box girder as the background,it is describes the whole failure process to get the each stage of loading test phenomena,response of structure,analysis of the stress mechanism and failure characteristics and relevant test parameters of each stage.Firstly,this paper introduces the characteristics and research status of prestressed box girder structure,and summarized the ultimate bearing capacity of the theoretical analysis and experimental research methods.Secondly,on the basis of the definition of pre stress,proposed the method of obtaining the true pre stress of the structure is obtained by testing the cracking moment,analyzed the theoretical calculation method of the cracking moment.For the constitutive relation,failure mechanism and typical failure mode of concrete structure are briefly summarized.The calculation of bearing capacity,crack mechanism and crack width calculation are discussed.Finally,combined with the engineering practice,analyzed the design of the load test,the cracking load test,the re-fissure load test,the failure load test to obtain stress strain relationship,the changes of the mid-span deflection,the phenomenon of cracking.To obtain pressure dissipation structure bending,cracking moment,restressing degree,parameters such as ultimate bearing capacity and safety reserves.