Unstiffened tubular joints have now generally become a common type of structural joint. However, at supports of long lattice girders where low bending moments and high shear forces occur, internal ring-stiffeners can be very useful. So far, ring-stiffened joints have been used in offshore structures in many instances. The theoretical results of the research for this paper show that internal ring-stiffeners (flat sections) are also useful for small chord diameters. By FE modelling of ring stiffened T joints it is found that the connection capacity for a compression loaded brace can increase significantly. The results of the computer analyses indicate that by including ring-stiffeners into the design, a joint efficiency of close to 100 % can be obtained. Within the scope of this parameter study the diameter and thickness of the brace as well as the ring-stiffener dimensions are varied. The chord diameter is kept constant, while the wall thickness is maintained equal to the brace wall thickness.
Tubular sections are used in lattice girders, masts and offshore platforms. T joints are a major component in such structures. At supports, problems can arise due to high shear forces in the chord while the moment loading (resulting in axial forces in the chord) is comparably low. In tubular sections, ring-stiffeners (flat plates) are a possible simple solution for such cases, particularly for smaller sections. Ring-stiffeners have found their main application in offshore structures. While the existing literature (Smedley and Fisher 1991. Sawada ct al. 1979. Brandi 1981) concentrates on this field, most of the important work has been on fatigue (SCF related) problems. Also. they have all dealt with large chord diameters, where T stiffeners have to be used.