Stress Analysis And Fatigue Characteristics Of Cable Tower Anchorage Zone Of Double-layer Four-track Railway Cable-stayed Bridge

With the rapid development of China’s railways,my country’s railway traffic has increased significantly,and cable-stayed bridges,as an important part of railway lines,are facing great challenges.The anchorage area of the cable-tower is the key part of transmitting the load.Due to the influence of the concentrated force of the stay cable,the anchoring force of the prestressed tendon and the weakening of the cable hole,the stress state of the structure is very complicated.Under the action of the heavy axle fatigue train,repeated alternating stress will appear in the anchorage area of the cable-tower,and the accumulated fatigue damage may lead to fatigue damage,which is more sensitive in multi-line railway cable-stayed bridges.It is very necessary to analyze the force of its structure by means of numerical simulation,to understand the force characteristics and fatigue characteristics of the structure,and to ensure the safety of the actual working state.This thesis takes a double-deck four-track railway cable-stayed bridge as the research background,and uses the numerical simulation method to analyze the spatial force and fatigue characteristics of the anchorage area of the cable-tower.The main research contents and conclusions of this thesis are as follows:(1)The whole bridge model is established with the help of MIDAS/Civil finite element software,and the segments of the cable-tower anchoring area are selected based on the calculation results of the whole bridge model.The ANSYS finite element software is used to establish the solid model of the anchorage area of the cable-tower for space force analysis.The results show that the compressive stress reserve of the tower wall in the anchorage area of the cable-tower can basically balance the horizontal force transmitted by the stay cable during operation,and the inner side of the tower wall will generate tensile stress that does not exceed the limit value.There is a local stress concentration phenomenon at the concrete cable hole and the anchor plate cable hole,where the concrete compressive stress is in a state of high stress for a long time.(2)Determine the type and frequency of fatigue trains by consulting the research literature,relying on the train line conditions of the actual project,and obtain the cable force time history diagram of different fatigue trains in the way of loading influence lines,and realize it with the help of MATLAB programming.After obtaining the cable force time history diagram,it is analyzed and processed by the rainflow counting method to determine the fatigue load spectrum.(3)The fatigue load spectrum is imported into the ANSYS model to obtain the stress spectrum of the fatigue details.Based on the evaluation method of the S-N curve of materials,the fatigue details of the anchorage zone of the cable tower are analyzed.The results show that under the most unfavorable working conditions of ZS17 and BS17,the annual average fatigue cumulative damage difference of the two fatigue details is small,and the minimum fatigue life meets the service life requirements of railway bridges.Fatigue damage of cable-tower anchorage zone during operation is not considered as a design control factor.According to the composition of annual fatigue cumulative damage,it can also be concluded that in the fatigue design of cable-tower anchorage zone,the role of single track and double track trains is mainly considered.