Research On Rapid Geometry Modeling Of 3D Solid Power Transmission Tower

Usually, for each new designed transmission tower, an expensive full scale test must be carried out to validate its safety. A more economical alternative is to do a computer simulation by using finite element method (FEM). At present, engineers mostly use a simplified tower model to do the finite element analysis, in which they use two-force bar or beam elements to discretize the beam components, and use hinged or rigid joints to model the nodes. Apparently, this simplified model is far from accurate to represent the tower's mechanical behavior. Though a solid element model or a hybrid beam element and solid element model would be much better, it is real hard to be built in existing FEM preprocess software on account of the non-trivial complexity of solid tower.In order to build the solid tower model more easily and quickly, this paper proposed a drawing based approach, which proceeded from the wireframe model and design drawings, then passed through three stages in turn, i.e. drawing recognition, structure matching, and solid modeling. After that, a solid tower model is built eventually.The drawing recognition stage is to recognize the angle beam components, screws, and connecting plate from the design drawings. According to the representation of these components on drawings, this paper introduced corresponding recognition algorithms for each kind of components respectively. For the recognition of angle beams, a relativity constrained iterative search algorithm is proposed, associated with a composite data structure named Angle Tree to make it run faster. For the recognition of screws, a simple position and radius based judging method is adopted. For the recognition of connection plates, a heuristic algorithm is proposed, in which the screws that might be on the same plate are merged into groups firstly, and then the connection plates are searched within the neighborhood of these screw groups.The structure matching stage is to build a mapping relationship between the 2D drawing structure and a substructure of 3D wireframe model. This paper proposed an approximate edit distanced based error-tolerant structure matching algorithm to do that, in which a matching seed and a projection base plane is selected by user, then a breadth first search (BFS) is launched to spread the matched pairs to whole structure.The solid modeling stage is to model solid angle beam components and connection plates. This paper discussed in detail how to determinate the size and position of each component. In the assembly process, a BFS based algorithm is adopted to offset the components automatically to avoid collision and penetration.Be aware of above methods, this paper built a complete solid modeling system prototype. It is verified by application examples that this system can be used to generate a local solid model of transmission tower quickly. This paper's research can provide a foundation for further study on full scale test simulation platform.