The space frame structure must be a geometrically invariant system under the action of external force. However, there are still many forms of space frames that are structurally geometrically variable in terms of their structure. Only after adding appropriate support constraints can it become a geometrically invariant system.
The triangle is geometrically invariant, so the space frame unit formed by connecting a new node with three non-coplanar members is also a geometrically invariant system. When the shape composed of the space frame rod system is a polyhedron composed of triangular interfaces, it is also geometrically invariant. Therefore, the analysis of the geometric invariant problem of the space frame structure can be turned into a plane problem.
The geometrically variable unit of the space frame can be a geometrically invariant system by adding rods or appropriately adding supporting chain rods.
When calculating with the program, if there is an unreasonable situation such as a particularly large deflection, the space frame structure may be geometrically variable.
The above analysis of the geometric invariant system of the space frame structure is carried out. If you are still confused, you can leave a message for consultation, and SAFS steel structure engineering will have professionals to answer you.