| Umbrella-shaped tensile structure,as a kind of cable structure,has a wide application prospect in small and medium span because of its clear force transmission path and light weight.The construction of umbrella-shaped tensile structure has a few mechanical problems.In China,the construction of cable structures adopts the way of manual operation of high-pressure oil pump to control jack at present.Through the automatic construction technology,the labor cost can be reduced and the construction efficiency can be improved.Taking the roof of Nanchang citizen center as the background project,the purpose of this thesis is to study the mechanical characteristics,construction technology and error control standard of umbrella-shaped tensile structure.At the same time,according to the construction requirements of the background project and considering the generality of the system,this thesis aims to develop a set of hydraulic control system,which can meet the demand of the construction of cable structures.First,the overall design of the cable structure roof of Nanchang citizen center is introduced,and ANSYS is used to build the finite element model.The iterative method is used for the forcefinding of the model.After verifying the correctness of the model,the static analysis is carried out to investigate the force and displacement of the structure under typical load.Meanwhile,the structural analysis under different load combinations is carried out to ensure the safety of the structure.Then,according to the structural characteristics and the layout condition of the site,the construction scheme of the project is designed: 5 bearing cables are used as lifting cables,and3 valley cables are used as stable cables during the lifting process.To obtain necessary parameters for the operation of the system,several key construction conditions are determined.The nonlinear dynamic finite element method(NDFEM)is used to analyze the construction process of the structure in order to explore the change trend of the cable force during the construction.The traction length of the tooling cables under different working conditions and the corresponding structural response are also determined.The construction error sensitivity of umbrella-shaped tensile structure is studied.The independent error analysis and coupling error analysis are carried out for force-control tension scheme and cable-length-control tension scheme respectively.The error control standards of different tension schemes are determined and the comparison of the two schemes is carried out.This thesis introduces the causes of accumulated travel error during the construction.The influence of accumulated travel error of uniform distribution and normal distribution on the structure during the tension process is studied to provide the basis for the monitoring value of the cable force during the tension process.To satisfy the demands of the background project and ensure the generality of the system,the overall scheme of the hydraulic control system is determined,and modular pump stations are the core.The key components in the pump station are selected,including PLC,hydraulic pump,jack,pressure sensor and displacement sensor.The design of common traction tools is introduced and the suitable jacks for the background project are selected.The basic functions necessary for the automatic construction of cable net are decomposed,and the I/O points of the equipment are allocated.Based on the flexibility of cable structures,the control method of the travel displacement and the speed of the cylinder extension of the jacks are put forward.The software of the lower computer of the pump station PLC and the main PLC are programmed respectively.According to the requirements of the construction of cable structures,three construction conditions are established including traction-length-control condition,traction-lengthcorrection condition and force-control condition.The corresponding control algorithms are designed respectively.The factors that affect the response of the structure after tension are studied,and the feasibility and shortcomings of the current algorithms are clarified.At the same time,in order to realize the generality of the system,the data input mode of the upper computer is proposed,and the upper computer software is programmed according to the requirements of the working-conditions-control,monitoring and data recording.The operation interface of the system is designed and the corresponding operation method is introduced.Finally,the work of this thesis is summarized,and the areas that can be improved are also pointed out. |
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