Prestress design and geometric correction method of cable-truss structures based on equivalent equilibrium force model

Cable-truss structure is a typical form of cable-strut tensile structures, which consists of upper cable system, lower cable system and several vertical struts. As with the general cable-strut tensile structure, only when the reasonable geometric shape matches the feasible prestress distribution can the cable-truss structure obtain structural stiffness and bear the external load. Once the geometric shape is unreasonable, the cable-truss structure is just a mechanism without bearing capacity and cannot be stiffened by introducing prestress. Consequently, a reasonable geometry is the premise for cable-truss structure to become an effective load bearing system. In this paper, an equivalent equilibrium force model, called EEFM, is proposed according to the geometric-mechanical characteristics of cable-truss structures. A cable-truss structure in this model is split into upper and lower cable systems with equivalent nodal forces. The geometric rationality can be easily evaluated from the equivalent nodal force relationship. According to the geometric topology and equilibrium equation of two cable systems, the self-stress mode of the structure with reasonable geometry can be directly obtained. For structures with unreasonable geometry, the node coordinates of one cable system are corrected based on the other cable system. Several cases are presented to verify the accuracy and validity of the proposed method. This method can be used for shape design, geometric correction and force finding, and has greater advantages for cable-truss structures with asymmetric or complex space configuration.