Research Of Cad System For Metal Roof Truss Structure

Metal roof truss which is usually made of thin-wall steel, is widely used due to its unique features such as flexible arrangements, diverse modelings, good mechanical properties and technological properties. With the development of society, the design demand for metal roof truss structure is increasingly high. General design and analysis software lacks good support for modelling, analysis and optimization, post-processing and so on. Aiming at the characterics of metal roof truss structure, the CAD requirments of metal roof truss constructure are summarized. Based on the study on the architecuture and core technologies of computer-aid design system for metal roof truss construe, a corresponding CAD system is developed.First, according to the characteristics of metal roof truss structure and its needs of computer-aided design, based on the analysis of similar CAD/CAE software available for structure analysis home and abroad, with AutoCAD as the graphics-processing platform, a 4-layer architecture general scheme for CAD system for metal roof truss structure is proposed, which includes user interface layer, graphics and data processing layer, access layer and data layer.Second, the core technologies for developing the CAD system for metal roof truss structure are studied. It is difficult to extract the parametric modelling method at overall structure level because metal roof truss structure has diverse types and complex strutcures. In order to quicken modelling for metal roof truss structure, a parametric modelling method based on the local features of metal roof truss structure is presented. By dividing the overall structures into several structure modules and applying parametric modelling method to each structure module, the goal is achieved. The rods of metal roof truss structure are connected by welding the gusset plates. On the basis of summarizing the fundamental requirements of gusset plate constructure and the design parameter of welding, a design method for gusset plate is introduced. According to this method, welded seam is designed by force and attribute information of rods, overall outline of gusset plate is determined by welded seam parameter, gusset plate meeting structure demands is generated by optimizing overall outline by using location and parameter information of rods. As engineering design documents is a vital reference for the engineering examination and verification of metal roof truss structure, an automatic generation method for design documents based on the reusable text configuration templates is presented. Knowledge modules involved in design documents are stored in text configuration templates, and then, design documents is generated automatically by configuring the templates.At last, based on above studies, the CAD system for metal roof truss structure is developed, which is validated to meet the design requirements of metal roof truss structure by an application example.