Research And Application On Offline-Assembly Method Of Steel Structure Components

With the development of the construction industry,there are more and more complex steel structure buildings.To ensure the success of the construction,most of the steel structure components need pre-assembly in factories before on-site installation.Due to the large size of steel structure,on-site assembly is faced with great difficulty that requires a lot of manpower,resources and space.On the other hand,the unqualified process of installation can have terrible influence on environment and workers' health.In contrast,the offline-assembly method of steel structure components provides another promising solution that avoids pre-assembly on site and achieves detection program integrating measurement,analysis and assembly.This research adopts different measurement and data processing methods for different components to instruct the construction of the steel structure and improve efficiency of steel structure assembly.Based on HSE(Health Safety Environment)and EBA(Energy Barrier Analysis)theory,the risks of on-site pre-assembly are first assessed to conclude key factors influencing HSE,dominating types of accidents,and ways of energy accumulation and propagation.Then,the risk prevention measures are elaborated to provide the theoretical basis and instructional framework for the proposed offline-assembly method which adopts different measurement and processing methods for small and complex-shaped components,large size and deep-hole components.For the small and complex-shaped components,three-dimensional scanning measurement and point cloud data processing have been used to form point cloud model of components to make comparison with BIM model.For the large size and deep-hole components,the portable light pen is used to measure and compare points on components.The improved TLS iterative algorithm is developed in this study for spatial point fitting to modify the BIM model.After measurement and data processing,assembly results and error reports can be outputted based on the virtual assembly of point cloud model or modified BIM model.For the components satisfying the assembly requirements,the assembly reports with assembly errors is used to guide on-site construction combined with BIM technology.In terms of components that cannot be assembled,components correction can be conducted according to the error reports.Finally,this study verifies this method based on some steel box girder bridge components in Wuhan.The benefits evaluation of offline-assembly method and risks analysis are conducted simultaneously.The results show that the offline-assembly method can greatly improve the efficiency of pre-assembly,the quality of the project and decrease costs of production and management.Comparing with the transitional techniques which is complicated,consuming more time,high cost,difficult to control error,low usage of space and so on,offline-assembly is more healthy,safely and environment friendly.This method reduces risks fundamentally and provides hopeful prospects for the further development of steel structure production industry.