Study On Monitoring Technology For Rotational Construction Of The Cable-stayed Bridge Over Railway Lines

Cable-stayed bridges have the advantages of large span capacity and beautiful bridge type.With the wide application of cable-stayed bridges,the situation of intersection of lines in construction of cable-stayed bridges is gradually increasing.The use of cable-stayed bridge rotation construction technology can reduce the impact on railway operation and ensure the safety of existing railway lines.In the process of cable-stayed bridge swing construction,in addition to balanced stress factors,it is also affected by many environmental factors.Especially after removing the bracing support of cable-stayed bridges,the vibration induced by train operation and gale weather will affect the overall stability of cable-stayed bridges,which may lead to deviation or even overturning.Therefore,the research on monitoring technology of cable-stayed bridge swing construction has practical application value in engineering.In this paper,the construction monitoring technology of a cable-stayed bridge with swivel structure is studied based on an example of a railway-crossing swivel cablestayed bridge project.The main research results are as follows:(1)By studying the construction process of cable-stayed bridge rotation,the influence of train-induced vibration and wind load environmental factors is analyzed.It is pointed out that the cable-stayed bridge is in the state of no auxiliary support at this time because of the uninterrupted train operation in the trial-turning stage,which is the most critical construction stage in the turning construction process.(2)According to the engineering example,the structure of asymmetric cable-stayed bridge is studied,and the weight and counterweight of asymmetric cable-stayed bridge are realized according to the principle of unbalanced moment.The monitoring data of the rotation of cable-stayed bridges are compared with the theoretical values.There is no contact between the supporting foot and the slideway from beginning to end.The vertical amplitude,lateral acceleration and vertical acceleration of the beam end are within the control range.The conclusion is drawn that the rotation process is smooth and there is no large jitter.(3)In this paper,the stability of cable-stayed bridges without auxiliary support is studied based on train-induced vibration.The data acquisition and time history analysis method are combined to calculate and analyze the stability of cable-stayed bridges.The results show that the rotational moment under vibration is less than the friction moment,so the train operation will not cause the cable-stayed bridge instability.If the rotating moment is greater than the friction moment,the supporting foot should be fixed to prevent the overturning of the cable-stayed bridge.(4)Based on the analysis of the stability of cable-stayed bridges under different static wind loads,the critical wind speed of static wind is obtained.Comparing the calculated flutter critical wind speed with the static critical wind speed,the smaller one is the critical wind speed of 12.6 m/s for cable-stayed bridge rotation construction.It was observed that the wind speed was 7.6 m/s less than the critical wind speed on the turning construction day,and the turning process was safe and stable.