Research On The Prestress Friction Loss Of Long Curved Beam And Tensioning Method Of Long-span PC Continuous Rigid Frame Bridges

Long-span PC continuous rigid frame bridges have been widely used in recent years,but a number of them appear cracks in different degrees after they are put into use,due to many factors of design,construction,construction control and operation etc.Through many experts and scholars' research results,insufficient reserve of effective prestress is an important cause of diseases such as midspan deflection and girder cracks.For long-span PC continuous rigid frame bridges,due to the loss of prestress,the actual stress in the structure is difficult to agree with the stress at the beginning of the design.That is to say,calculation of stress can not reflect the actual stress state of the structure and it left a security hazard at the beginning.The prestressing loss of long beam increases continuously with the increase of beam length compared with the short beam.At the same time,the reserve of effective prestress is directly related to the loss of prestress and the prestress loss will affect the crack resistance and deflection of the structure.This paper takes the Hanjiang super large bridge as the support project and the prestressing loss of long curved beam is studied by friction test on the whole bridge by means of integral beam + single tension around the prestressing loss and tension mode of long-span PC continuous rigid frame bridges.Therefore,in order to correctly analyze the prestressing loss of long curved beam,the following research is carried out in this paper:(1)The principle of prestress loss of Long-span PC continuous rigid frame bridges has been theoretically analyzed.Based on the research of Long-span PC continuous rigid frame bridges by scholars at home and abroad,the main diseases existing in continuous rigid frame bridges are expounded,and the prestress losses caused by the deflection of long curved channels and the deviation of ducts are discussed theoretically.(2)Based on the friction resistance test of large span continuous rigid frame bridge,the long bend beam mu value and kappa value are measured,and the prestress friction loss is compared with the standard value.In the actual engineering friction test as the starting point,the effective prestress reserve of long curved beam,using the least square analysis method,sensitivity and combination of tension and friction test site strain and elongation data,measured value and kappa value,and a reference to similar bridge test results of test data and many experts and scholars due to insufficiency of effective prestress for long curved beam friction loss are analyzed.(3)Based on the results of finite element analysis and field friction test of long-span PC continuous rigid frame bridges,the loss of effective prestress caused by friction loss of long curved beam was analyzed.This paper takes the Hanjiang super large bridge as the support project and the prestressing loss of long curved beam is studied by friction test on the whole bridge by means of integral beam + single tension around the prestressing loss and tension mode of long-span PC continuous rigid frame bridges.Combined with the results of Midas finite element analysis,the phenomenon of effective prestress shortage caused by friction loss of long curved beam is analyzed.