Thin walled structure is widely used in designing light weight vehicle. For automotive industry, weight is an important characteristic to increase performance of a vehicle. Vehicle structures are built from thin walled beams by joining them using various joining methods and techniques. For a structure, its stiffness greatly depends on joint stiffness. However, stiffness of thin walled beam is difficult to predict accurately due to buckling effect. Once the beams are joined to form a structure, it will expose to joint flexibility effect. A lot of researches had been done to predict the behaviors of thin walled joint analytically and numerically. However, these methods failed to come out with satisfactory result. In this research work, finite element model for 3D space frame thin walled structural joint is developed using circular beam element by validating with experimental result. Another finite element model using rigid element is used to represent 3D space frame behavior without joint effect. The difference between these 2 models is due to joint effect. By using same modelling technique, joint stiffness for different sizes can be established. Then, the relation between joint stiffness for 3D space frame and size of beam can be obtained.
