Study On Fatigue Behavior Of Prefabricated Steel Truss Concrete Composite Beams Based On PCSS Shear Connection

Supported by the Ministry of transport construction technology projects(2013 319 814 040)"the basic theory research of constructing the extra-large-span steel trussconcrete composite continuous rigid frame bridge" leaded by the tutor.For the full fabricated truss-concrete composite continuous rigid frame bridge was first used on qingqichong super long span bridge of guangfuzhao highway,mechanical behavior experimental study of the composite beam at negative moment section of the qingqichong bridge had been conducted under fatigue loads.Main study works are as follows:(1)Based on the Qingyingyong Bridge,the steel truss-concrete composite model test beam was designed according to the 4:1 scale of the negative moment zone.The fatigue load lower limit and load amplitude were determined according to the dead load of the real bridge and the vehicle load.Accumulative 3.4 million times of fatigue load test on the test beam.(2)The test beam was subjected to 2 million fatigue loadings,and it was verified that the composite beam did not undergo fatigue damage under normal use cyclic load.Then,the load amplitude is continuously increased to simulate the overload effect of the composite beam at different degrees.After a certain number of loadings,the loaddeflection curve is measured by static loading test.The stiffness degradation law of the composite beam is observed,and the interface strain distribution and stud slip change law are combined.And bridge deck crack analysis combined beam stiffness degradation causes.(3)Aiming at the discontinuous distribution of steel-concrete interface shear force in the fully-disassembled steel truss-concrete composite beam,the discontinuous distribution of steel-concrete interface shear force is studied.The discontinuous force transmission model of steel truss-concrete composite beam is explored,and the connection is calculated according to this model.The stress of the joint welded joint between the deck and the steel sill under fatigue load,and the method of mitigating the fatigue stress according to the force characteristics.(4)The fatigue performance of the shear-welded joints of the Qingliangyong Bridge combined beam under actual vehicle load is studied.The local solid-shell element model is established by the ABAQUS software,and the sub-model technology is used to refine the weld near the weld.The grid,introducing the hot spot stress method,and considering the weld defects,calculated the hot spot stress amplitude of the weld under the fatigue model III load specified in JTG D64-2015.(5)The parameters of the shear joint weld details of Qingyingyong Bridge are analyzed.The influence of weld seam on the hot spot stress amplitude of welds under different penetration depths,different fillet weld sizes and different gusset shapes and sizes is discussed.