Research On The Essential Safety Of The Attached Tower Crane Based On Time-varing Theory

With the development of our country's urbanization process,the construction industry in all parts of the country is in full swing.The attached tower crane is heavy hoisting equipment,which is palying a great important role in construction.On the one hand,the attached tower crane have many advantages that large lifting weight,big turning radius,wide operating area,plays an important role in improving construction efficiency and reducing labor intensity and construction cost and the realization of the mechanization of engineering construction.The attached tower crane is becoming more and more indispensable in the process of high-rise building construction of large transport equipment.On the other hand,the service time of the attached tower crane is long,the whole service cycle includes: assembly stage,jacking stage,use stage and disassembly stage.What's more,it's dismantling process is complex,and need to cooperate with different type of workers,operators personnel quality is uneven,high level requirements operation,vulnerable to environmental influences.Because of the above reasons,attached tower crane accidents may occur all over the whole service stage.The traditional concept of safety is passive acceptance of accidents,while the concept of essential safety is active prevention.This paper studies the nature of tower crane safety which based on basic structure in different stages of the tower crane,find out the key link in different stages of the tower crane safety,which allow us to take corresponding measures to control the safe state,so as to achieve the aim of preventing the hidden trouble.The attached tower crane is a typical time-varying structure,need to change frequently in the service cycle.Therefore,the mechanical characteristic model of each stage of the attached tower crane was established,which is based on the viewpoint of time-varying theory,and combines SAP2000 finite element analysis software.Through the model analysis,the key stress joint which affect the overall safety of the attached tower crane were found out,and the key stress joint were analyzed in a more deeper and more reasonable way by using the mechanical method,and the internal force variation law of the components under the influence of multiple factors was studied.This study concluded that the installation disassembly stage resistive overturning stability calculation model,jack-up job stage jack-up beam trunnion internal force calculation model and jack-up operation phase equilibrium model,the tower crane pin-ear plate connecting nodes of internal force calculation model.The above model can effectively serve the design of attached tower crane and its overall safety risk monitoring.Besides,in this study,relevant experiments were carried out on the relatively important parts of the actual attached tower crane,and the experimental data were analyzed and compared with the theoretical model.The data verified the validity of the finite element analysis model that established by the institute,it can also effectively serve the overall safety assessment of the attached tower crane.