The Key Technologies Of Computer Aided Design Of Continuous Beam Bridge

Computer Aided Design (CAD) is the main technology in the area of engineering surveying and design. Because of the improvement of computer technologies and of development of application requirements, the previous CAD technology cannot meet the development of the industry application. In modern CAD system, object analysis, data exchanging between different systems, product viewing are supplied as well as graphic plotting. So that currently new CAD technologies and new methods such as Parametric Design, Dynamic Data Exchanging and Engineering Visulization play important roles in the area of engineering surveying and design.In this paper, it begins with the technology of Parametric Design, Dynamic Data Exchanging as the major point. At first, the concepts of Parametric Design and the technology of Dynamic Data Exchanging based on background database is emphased. Parametric Design is the best way to describe the attributes of an object designed, and supplied a way to analyze the attributes at real time. The Dynamic Data Exchanging provide a way to standardize the result of the object analysed, and provide a way to exchange data between different systems.Then, the Continuous Beam Bridge CAD System is taken as a real example, to analyse the system structure including the layout, data requirements, procedure diagram of the sub-systems such as Beam Calculating and Modeling, Construction Simulating, Structure Analysis, Result Output, Pre-stressed Tightwire Layout, General Tightwire Layout, Design Graphic Plotting.Next, the key technologies of the Continuous Beam Bridge CAD System including the definition and usage method of various geometrical/physical models, the definition and procedure of data structure and the optimization of pre-stressed tightwire are described. The methods and examples to describe the utilization of AutoCAD_ADS, ObjectARX, Entity Dictionary and the utilization of Dynamic Data Exchanging is also supplied. The Entity Dictionary and the Extended Entity are the basic definitions of the attributes of a designed object. Through the connection of background database by RDO, we can extend the attributes of object.Finally, some real application samples is given in this paper.