| The skybridge is a new type of structure that has been developed in the past twenty years.More and more designers become enthusiastic about this suspended structure on account of its unique appearance and diverse functions.This paper takes the construction of multi-storey concrete skybridges of Zhihui Building in Yangzhou as the research background.Based on comparing and analyzing several formwork methods,spatial steel truss structure is adopted as the formwork platform for constructing the skybridges of Zhihui Building,combining the specific characteristics of this project.Then,following aspects are studied as well.(1) Design selection of steel platform and steel corbel.Through comparative analysis of two spatial steel truss plans,namely deck type and diagonal bracing type,deck spatial steel truss structure is defined as the structure type of the steel formwork platform,and its self-vibration characteristics are also calculated.Considering the reaction force is awfully large during use of steel platform,so select double-webbed box corbel as the support corbel because of its strong shear capacity.In addition,the effects on exsiting main structure caused by using steel platform are also studied,and some strengthening measures are taken in the concentrated area of large tension stress.(2) Design loads and removal period of the steel formwork platform.According to a certain analysis idea,arrangements of steel tube scaffolds are designed to get the basic loads when the 1 st skybridge works alone,then use ANS YS to analyze the behavior of integral steel tube scaffolds with semi-rigid connection under different load cases.By importing reaction forces of scaffolds into the overall model composed of 1st skybridge and main structure,the mechanical properties of 1st skybrige under 10 days are checked when it works alone.The results show that,because of secondary beam,1st skybridge is unable to bear the construction of 2nd skybridge without steel platform.In theory,steel platform can be removed after completing 1st skybridge,but considering the deformation of secondary beam is large when 1st skybridge works alone, in actual operation, to ensure engineering quality and safety,remove steel platform after completing 2nd skybridge.(3) Installation of the steel formwork platform.The steel platform in this project is a large spatial steel truss structure,and there are various common installation schemes.According to the situations of construction site,two schemes are primarily selected.Through multi-index comprehensive comparison, the most dominant integral lifting method is finally determined to install and remove the steel formwork platform.Besides.this paper has also analyzed and solved some technical problems during the lifting process,meanwhile specific ideas are given for this method.(4) Control of steel formwork platform in construction process.Firstly,based on assessments of calculation results, the most reasonable 8 lifting points scheme is determined among all the 3 schemes.As the position and number of lifting points are known,the author has studied the limit of lifting displacement difference under two cases,after comparison,it sets the limit of lifting displcement difference to± 30mm.Then,use ANSYS to analyze the stability of steel platform during lifting process,the results show that the out-of-plane instability will not happen while steel platform is actually lifted.During actual construction,steel platform will be removed after completing 2nd skybridge.So in order to study the mechanical property of steel platform when constructing 2nd skybridge,birth and death element method is adopted.And it comes to the conclusion that, it is feasible to design the steel platform for bearing construction of 1st skybridge and it is also feasible to remove the steel platform after completing 2nd skybridge.Finally,this paper has also discussed measures of control and monitoring in the process of integrally lifting steel platform.The study of this paper is in the hope of providing references for constructing similiar multi-storey concrete skybridges. |
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