The CAD/CAM Technologic Research On Spatial Truss

Recently, tubular truss structures are used extensively in the large-span space structures. These modern structures are found in hall lobbies, airports, gymnasiums, meeting centers and other sites with their structural efficiency, fluency, and aesthetic appeal. In these structures, the hollow section members are joined together by welding the profile ends of secondary members, the braces, onto the circumference of the main member, the chord. These structures spurn conventional spherical joints, simplify joint-configuration and make the whole structures concise. In the paper, the aim is to fabricate tubular truss structures, and basic research about intersection curve of pipe-cutting is carried on. Based on this research, software on the fabrication of tubular joints is developed to adapt to various joints of truss structures.In the field of basic theory on pipe-cutting of intersection curve, firstly, different kinds of tubular truss structures are analyzed, basic types of truss structures and joint configuration on connections are grasped, which intersection curve calculation is divided into two groups: the linear chord and the arc chord. In the process of calculation, numerical calculation and geometric graph is combined, which avoids solving simultaneous equations and makes calculation simplified. Especially in the multi-pipe intersection, appropriate coordinate systems is set up which simplifies coordinate transformation, and a new algorithm of cut-pipe generatrix comparison is adopted which overcomes some complicate calculations such as solving the simultaneous equations.At the same time, a lot of technological questions in the fabrication process are considered. Judgment on overlap joints is suggested to solve the verdict for connection types in the intersection-curve calculation. During computer-aided lofting, considering the effect on the thickness of pipes, amended formulas are given. In addition, to accomplish grooving at the same time of pipe cutting, formulas of groove angle are deduced in detail.