Abstract: The main force of tubular L-joints is bending moment. It is different from connections of common tubular truss. A simplified theoretical method is adopted to analyze the strength and stiffness of tubular L-joints. It reveals that the normal stresses in transverse direction of steel tube pinch the tubular wall at connection zone. As a result, the stiffness and the bearing capacity of joints are reduced. L-joints without rib stiffener are semi-rigid connections. The main factors influencing transverse normal stresses are the angle between two tubes, connection type and construction details. The design formulae and construction details are suggested based on the theoretical results and engineering practice, which are validated by finite element analysis.