A Study On The Construction Of Large Span Moving Support System In Strong Wind Areas

The moving support system is a construction equipment which uses bearing steel girders and piers.This system supports formwork,beam weight and various loads for the bridge construction through hole by hole pouring.Among the existing projects,most of the bridges employ the moving support system have relatively good weather conditions,and there is no monsoon with high frequency,high intensity and long duration.At the same time,there is a lack of design and construction experience of the moving support system in strong wind areas.In view of the application status and facing problems of the moving support system,this thesis takes the Songxia Super-Large Bridge of Fuzhou Changle to Pingtan Expressway as an example to investigate the performance of the moving support system in strong wind areas.It is noted that the Pingtan Strait,which is one of the three major wind outlets in the world.This project site experiences strong winds of 6 grade and above exceeding 300 days per year.Meanwhile,for this project the average pier height of Songxia Super-Large Bridge is over 38 m,the span of the upper cast-in-place box girder is 58 m,the span of the largest cast-in-place box girder is 68 m,and the maximum pulling volume of the single-hole box girder is close to 1000m3.The construction technology of the moving support system under such complex conditions is systematically studied in this thesis.For the strong wind conditions in the sea area of the Songxia Super-Large Bridge site,a design method for the downward moving support system with large-span is proposed,and the main technical parameters are given to meet the construction requirements of the long-span moving support system.At the same time,the wind-resistant balanced beam is used to improve the stability of crossing holes in strong wind areas.Aiming at the assembly of the long-span moving support system at the cliff,temporary bracket erection and combined lifting and pushing construction techniques are presented to resolve the assembly problem of the moving support system.Aiming at the construction efficiency in strong wind areas,the movable gantry crane is used,which can improve the construction efficiency,shorten the construction period and cut down construction cost.Subsequently,the unfavorable working conditions such as pulling and passing holes of the moving support system in strong wind areas are further studied by finite element modeling.The results show that the strength,stiffness and stability of the moving support system meet all code requirements for the working conditions.At the same time,the pre-arch values are set by comparing the experimental pre-compression values and the finite element results.The overall stability and safety of the moving support system are proved.Finally,by a preliminary examination of the construction benefit between the steel pipe support and the moving support systems,the advantages of the moving support system for super-large bridges are summarized.