Researches On Erection Simulation Optimization And Thermal Effect Of Large-span Double-helix Single-layer Latticed Shell Structure

With the development of economy,the engineering construction tend to be more large and complex.A batch large scale and complex project have been established.The geometry,material property and boundary conditions will endure significantly change during erection process.The internal force of member and structural deformation is generated through accumulation of each constructional step.So the internal force and deformation of the whole structure are closely related to constructional process.At the same time,erection phase is the most dangerous period of the life cycle of the whole structure.It has been pointed out that more than two thirds of the structural collapse accidents happened during erection phase according to statistical results.The reason is that the complexity of construction was ignored.The theory about construction mechanics is not mature in many aspects due to its wide range.Such as the numerical simulation method,ultimate load computing theory of scaffold system,optimum of construction process,influence of welding residual stress on mechanical behavior,theory of wind-induced vibration analysis,etc..In addition,influence of nonuniform temperature field caused by solar radiation on mechanical behavior of structures in construction and service phase is also an emergent key problem to solve.Birth and death method is the most commonly adopted method for construction simulation.The mechanical principal is multiply the stiffness matrix of uninstalled component with a factor which is small enough so that the influence of uninstalled components can be neglected.But the dead element are not eliminated from the whole structure.These element will deform according to the nodal displacement between dead element and live element,i.e.‘floating'.In this paper,secondary development of general finite element software was conducted based on step by step technology and the numerical construction simulation method which can avoid floating was proposed.At the same time,the numerical simulation of the whole construction process was conducted based on the YUJIAPU railway station building,a conch-shaped latticed shell structure.The changing history of stress during integral lifting process was systematically studied and the field monitor was also conducted.Based on the work mentioned above,ultimate loading capacity of door-type scaffold system was investigated.The mechanical behavior of connection joint of door-type scaffold system is complex.The connection joint between different modules present semi-rigid characteristic.An efficient numerical method for considering semi-rigid joints was put forward in this paper.At the same time,the initial member bend imperfection was considered.In addition,ultimate loading capacity of door type scaffold system was also investigated.Dozens of supporting jigs are needed for construction of large scale and complex project.The selection of supporting points for spatial structures which have complex shape is very difficult for the engineers,such as the YUJIAPU railway station building.It is a big problem to select the optimum combination of supporting points.In addition,unloading sequence of the supporting points is closely related to the constructional safety.So investigations about the series problems mentioned above were conducted based on the real coded genetic algorithm method.In addition,a binary coded genetic algorithm was adopted for optimization of support stiffness.There are always a lot of welding work in construction site.The YUJIAPU railway station building was constructed by fully welding the member together.Influence of welding residual stress on mechanical behavior of thick steel plate,box member and box member-cross plate welding joints was systematically investigated.An efficient computational method was proposed by embedding the wielding residual stress in the overall structure.The amazing computational time was avoided and this method make it possible to consider the influence of welding residual stress in the overall structure.In addition,the method to consider the influence of welding residual stress by change the material property was also proposed.It was adopted for investigations of an actual project.The proper orthogonal decomposition method and pseudo excitation method were combined to put forward the POD-pseudo excitation method.It was suitable for wind induced vibration analysis of spatial structures and the computational cost was reduced significantly.This method was adopted to conduct wind induced vibration analysis for structure under lifting state.Results have shown that this method was efficient and accurate for the structures with low natural frequency.The construction period of large-span spatial structures is usually very long.Therefore the structure under construction state will suffer not only the daily temperature variation but also the seasonal temperature difference.So the temperature field and stress field were monitored on to investigate influence of temperature on the large-span double-helix structure;the monitoring work was continued for one year to investigate the influence of membrane structure.The results monitored before and after installation of membrane structure was compared to investigate the influence of membrane on structure under solar radiation.