Research On Static Behaviour Of Unstiffened Overlapped Circular Hollow Section K-Joints

Steel tubes have been widely used in large span truss structures because of excellent properties. As organic component of whole structure, design of tube-to-tube connections is a important aspect. Connections between hollow section members are usually configured by welding one member directly to the surface of the other, where possible, without any stiffening or reinforcing element. Overlapped Circular-Hollow-Section(CHS) K-joints are widely used in actual projects. It is necessary to investigate static behaviour of Circular-Hollow-Section K-joints in all aspects.On the basis of overlapped CHS K-joints mode tests, nonlinear FE analysis on joint specimens are made. The disseration disscuss behaviour, failure mechanism and ultimate capacity of overlapped CHS K-joints. The effect of overlapped ratio, hidden seam welded or not, loading hierarchy reversal, throat thickness of fillet welds, the unbalanced loading at the joint as well as the joint geometry on joint behaviour is discussed. Parametric formulae for predicting ultimate capacity and seam length are given.Firstly, experimental research on static behaviour of overlapped CHS K-joints are conducted. Seven specimens with the hidden seam unwelded and three specimens with the hidden seam welded were tested under monotonic loading. The test procedure and joint failure mechanism are presented. The effects of the joint geometry, the throat thickness of fillet welds, hidden seam welded or not, unbalanced loading at the joint as well as the loading hierarchy reversal on the joint behaviour were studied. Results of these tests show that the welding situation of the hidden seam has some effect on the stress distribution and failure mechanism, but the static ultimate capacity of the overlapped CHS K-joints is not affected significantly given that through brace is under compression. When the brace-to-chord thickness ratio is smaller, the local failure is the main failure mechanism observed. This failure mechanism and the consequent reduction of the ultimate capacity have not been considered by the current codes. This chapter lays an experimental foundation for the...