| In the construction process of super high-rise building,low level jacking formwork platform with few fulcrums(jacking formwork platform for short)is the most widely used formwork system at present.The system has a number of advantages such as good overall closure,high degree of integration and high security,but also improve the construction efficiency and shorten the construction period.However,in long-term use,it is found that the structure will face the influence of man-made damage,environmental corrosion or sudden situation,which may lead to local stress concentration,strength failure and brittle fracture.In order to avoid the corresponding engineering safety accidents or the existence of potential hazards.Therefore,it is necessary to analyze the mechanical performance of the steel platform with jacking formwork,especially the mechanical state of the local components at the fulcrum.It is of great significance to evaluate the bearing capacity and stability of jacking formwork platform scientifically and reasonably.Based on the jacking formwork steel platform used in the construction of a super high-rise project,this paper analyzes the stress forms and characteristics of the structure of the jacking formwork steel platform by theoretical analysis method.The field monitoring method is used to master the actual stress of the structure,and the real-time monitoring of the steel platform structure of the jacking formwork is carried out and the monitoring results are analyzed.Combined with the actual load distribution in the field,the finite element software is used to analyze the steel platform of the jacking formwork frame,and the numerical calculation is carried out under three different working conditions:construction,jacking and self-climbing.The characteristics of steel platform system with low level jacking formwork frame with few fulcrums are analyzed.The structure of jacking support system of steel platform with jacking die frame is improved by adding force fulcrum to reduce stress concentration.Firstly,the general situation of the system of the steel platform with jacking formwork is discussed,and the structural characteristics and working principle of the system are analyzed.At the same time,the force transfer path between each system in the jacking formwork steel platform is expounded,and the force characteristic of the jacking formwork steel platform itself is summarized.According to the results of simulation and analysis of the preliminary design and the characteristics of the structure,a detailed on-site monitoring technical scheme is prepared.According to the site construction conditions,the jacking formwork steel platform structure has been monitored for nearly three months.Combined with the stress state of the structure in the actual use process,the stress variation rule in the monitoring data is obtained,and the measured average value of the stress and the original calculated value are analyzed.In order to further explore the mechanical properties of the steel platform with jacking formwork under actual conditions,a finite element model was established based on the actual load of the steel platform with jacking formwork in engineering applications.Different finite element models were established according to three different working conditions,and the maximum displacement and deformation values and the maximum combined stress values under different working conditions were obtained.The stress concentration with less fulcrum on the steel platform of jacking formwork frame has a negative effect on the components at the joints after comparing several different schemes.A solution of adding a movable mechanical auxiliary column at the original fulcrum is put forward,and the corresponding structural sketch and section characteristics as well as the recommended length range are given.In this paper,the mechanical properties of steel platform with jacking formwork are analyzed.By comparing the analysis results of the finite element model and the monitoring results,it is concluded that the structure is still in a safe state.It is found that the monitoring value of some components is greater than that calculated by the preliminary design simulation analysis,and exceeds about 15%.The main reason is that the load value is not considered enough in the preliminary design process,and the secondary reason is that the construction site has not strictly fulfilled the load stacking requirements.In view of the unfavorable situation of the original structure system with fulcrum,the improved scheme is put forward to effectively reduce the stress concentration at the original fulcrum,improve the stability of the structure,and increase the ability of resisting lateral movement of the structure,and achieve a certain expected effect.The research results can provide reference for the design and construction of similar type of jacking formwork steel platform in the future. |
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