Fatigue Performance Analysis Of Modulus Expansion Joints Based On Nominal Stress Method

In recent years,with the increase in infrastructure investment,the road traffic field has developed by leaps and bounds.The bridge telescopic device is located at the end of the bridge and so on.It is directly subjected to repeated impacts of vehicle loads throughout the year and is prone to fatigue damage.Replacing the telescopic device will not only lead to an increase in the maintenance cost of the bridge,but also block traffic and affect the normal operation of the bridge.In addition,the damage of the telescopic device will also affect the beam and deck pavement,reduce the service life of the bridge structure,and increase the maintenance cost of the bridge.In this paper,the fatigue performance of the bridge modular expansion joint specimen is studied.The static load and fatigue test of the expansion joint specimen are carried out.The two-dimensional finite element analysis model of the expansion joint is established by ANSYS.The bridge is realized based on the nominal legislation.Evaluation of fatigue life of expansion joints.The main work of this paper is as follows:(1)The static load and fatigue tests were carried out on the three sets of expansion joint specimens,and a set of expansion joint specimen loading device conforming to the domestic laboratory conditions was designed.The inclined angle of the device was 11.3°,and the expansion joint specimens were able to be tested.Apply horizontal and vertical loads simultaneously,horizontal load:vertical load is 5:1.Observe the type of fatigue crack that occurred during the fatigue test,the location where the crack occurred,and the number of cycles when the fatigue was broken.In the process of fatigue test of expansion joint specimens,the 3D digital image processing technology was used to investigate the displacement field and strain field of the welded joints of the beam and beam in the expansion joint specimen(2)A two-dimensional finite element calculation model for expansion joints was established.Based on the finite element software ANSYS,the middle beam and the beam of the expansion joint specimen are created by the beam unit Beam 188.The welding between the middle beam and the beam is approximated by the rigid connection and connected by a coupling command.The deflection and strain of the expansion joints under different loads measured by the test were compared with the finite element calculation results.The error was within the allowable range and complied with the NCHRP-402 report.The applicability of the analysis model was verified.(3)The fatigue life prediction model of bridge modular expansion joint based on nominal stress method is developed.Combined with the established finite element analysis model,the finite element model is solved to obtain the nominal stress of the welded part.The Miner linear damage accumulation criterion is used to predict the fatigue life of the expansion joint.By comparing the theoretical calculation results with the life curve in the American AASHTO specification,the expansion joint fatigue detail level conforms to the C and C' type fatigue details.