Mechanical Behavior Analysis Of Continuous Rigid Frame-Flexible Arch Bridge After Damage

In recent decades,China has begun the large-scale construction of continuous rigid frame arch bridges.This structure combines the advantages of concrete-filled steel tube arch bridges and continuous rigid frame bridges.It has the advantages of large overall rigidity,large spanning capacity,and convenient construction.It can better meet the traffic requirements of high-speed railways.However,under normal use conditions,with the extension of service time,due to environmental influences,degradation of material properties and other reasons,the critical components of continuous rigid-frame arch bridges may be damaged,and the safety performance of bridge structures may be affected in severe cases.This paper intends to analyze the possible damage of the suspender and the damage of pier-girder-arch connections of the continuous rigid frame arch bridge,and to study the changes of the cable force and the deflection of the main beam of the continuous rigid frame arch bridge after the damage of key components.In this paper,the Huaihe Extra Large Bridge(continuous rigid frame-flexible arch bridge)is taken as the research object,and the finite element analysis software MIDAS/Civil is used to establish the spatial finite element model of the bridge.Firstly,the change law of the cable force and the deflection of the main beam(anchor point of the main beam under the suspender and the quarter-point of the side span)of the bridge was studied when the constant load,temperature load and train load are applied separately.Then,under the constant load,a single cable damage of 5%,10%,15%,20%,25%,30%,and 50% occurred on the left half-span suspender on the downside,and under the train load 30% damage occurred with different suspender,The change law of the cable force of each cable and the deflection of each point of the main beam(anchor point of the main beam under the suspender and the quarter point of the side span)was studied.Finally,the Change law of cable force and the deflection of each point of the main beam(anchor point of the main beam under the suspender and the quarter point of the side span)under different loads and(including different damage levels and different damage lengths)of the pier-girder-arch connections were studied.The results show that the distribution of cable force of the suspender under constant load is relatively uniform,and the mid-span and both side spans of the main beam have a certain upwarp.The cable force of the suspender and the deflection at each point of the main beam(anchor point of the main beam under the suspender and the quarter point of the side span)linearly change with the increase and decrease of the overall temperature.The damage of the suspender will obviously reduce the cable force value on the damaged suspender.The cable force values of the four suspenders on the two sides closer to the damaged suspender will increase to a certain extent,and the remaining suspender cable force will not change significantly.The damage will cause the mid-span of the main beam to downwarp and the the side span to upwarp.With the increase of the degree of damage of the boom,the degree of reduction of the cable force of the boom increases,and the degree of downwarping of the mid-span main beam and t side-span main beam increases.The damage of the pier-girder-arch connections causes the main beam to show deflection in the vicinity of the damage location.The deflection value and the absolute value of the change in suspender cable force increase with the increase of the damage length and the degree of damage,but this cable force change and the deflection change is not obvious and the magnitude is small.Suspender damage can be judged by the change of cable force,it is difficult to judge the damage of the suspender by the change of deflection,and it is difficult to judge the damage of the pier-girder-arch connections by the change of cable force and deflection.