Truss is a plane structure composed of straight bars and generally has triangular elements, as shown in Fig. 11,2. Truss members mainly bear axial tension or pressure3,4, so as to make full use of the strength of materials to give full play to the role of materials, save materials and reduce the weight of the structure5,6.
Truss structure originated in ancient Rome, after continuous development, it has been widely used in various fields of life, such as large space roof, Industrial workshop, bridge, aircraft, crane, and so on7. Therefore, the research of single truss has been very thorough and it has been widely used, but for truss system, there are still many areas to be researched and developed8.
After further research on the mechanical characteristics of truss, a mechanical phenomenon is found: When the two trusses are overlapped and loaded respectively, the lower chord of the upper truss generates tension and the upper chord of the lower truss generates pressure. If the upper and lower trusses are connected as a whole at the overlap, the "internal force" hedging effect will occur, so as to reduce the internal force of the structure; If the upper and lower trusses are only overlapped and do not form a whole, there is no such effect. This phenomenon is verified by experiments.