Study Of Pre-processing And Post-processing Of Computer-Aided Design System On The Space Grid Structure

During the last two or three decades, the space grid structure was becoming a very popular structure type. Now, the span of this kind of structure is becoming larger and the form is becoming more complicated increasingly. It is very difficult to design the structure by the traditional means. Hence, it is very important to work out the CAD software that is used to design the space grid structure.On the basis of summarizing the similar software's strongpoint and shortcoming, the key techniques used to develop the computer-aided design system are studied especially in this thesis. For the first time, ActiveX Automation, a technique to develop secondly AutoCAD, is applied to the large structure CAD system in China. The system's pre-processing and post-processing modules are accomplished with this technique. In this thesis, several aspects as follows are studied:(1) Making use of ActiveX Automation, the intercommunicating connection between the application and AutoCAD is established. Then, it is applied to the large structure CAD system.(2) A new input way of structure sketch was gained in this thesis. Utilizing ActiveX Automation, the system can manage AutoCAD to directly create some entities such as lines and spheres that are used to figure the bars and nodes. At the same time, the information of bars and nodes can be generated automatically through analyzing these entities' correlative data. While the application is running, the user can intercommunicate with the system and achieve the information of loads and boundary restraint. By this means, the applicable range of the pre-processing is extended.(3) The post-processing module of the system can automatically generate the construction drawing of plan, installation internal force and material tables. And the structure's three-dimension model also can be come into being automatically.(4) By integrating the pre-processing and post-processing modules with the calculating module, an integral computer-aided system on the space grid structure -SGSCAD is achieved. Finally, SGSCAD is proved to be feasible by analyzing several practical engineering examples.