Kenshi Ochi

Local buckling of braces in tubular K-joints

Abstract The local buckling of compression braces is one of the recognized failure modes yet to be studied in three-member truss connections of circular tubular members. A series of tests was performed to examine the brace local buckling behavior. The test results demonstrate that the brace local buckling is influenced not only by the wall thickness of the braces but also by the stiffness of the joints. Simple prediction equations for both the resistance and the deformation capacity of the joints failing in this mode are presented on the basis of these test results. It is shown that joint deformation can have beneficial effects on the overall ductility of trusses, when diameter-to-thickness ratios of braces are limited within the range of this test.

ULTIMATE CAPACITY OF TUBULAR DOUBLE K-JOINTS.

A static test was conducted on circular tubular joints in three-dimensional trusses with a triangular cross section. The behavior of these joints was similar to that of planar K-joints. The ultimate strength of these joints was found to be accurately evaluated from the ultimate strength prediction formula for the K-joint.

AWS vs International Design Rules for circular tubular K-connections

Abstract The American Welding Society (AWS) rules are compared with the International Institute of Welding 〈IIW〉 rules for circular tubular connections because of the differences between the two. Subjects discussed include: accuracy in prediction, effects of size and material properties, premature failures due to local buckling of braces and due to fracture at weld toes, and applications to multiplanar connections, focusing on the ultimate behaviour and design of K-connections under axial brace loading for the sake of conciseness. One important conclusion is that the AWS rules lead to relatively unsafe design for K and KK-connections with stocky chords. Suggestions to enhance the reliability of the AWS rules are made.

Recent research developments in the design of tubular structures

Abstract The statistical evaluation of material properties of cold-rolled tubes reveals that both the yield strength and yield ratio of these sections are expressed in functions of D / t and are unusually high compared with those of hot-rolled steels. Based on statistical data for cold-rolled tubes, the local buckling and column buckling strengths and the rotation capacity of portals are evaluated and compared with existing test results. The statistical parameters of the resistance of tubular K-joints are shown. The resistance equation is applicable to K-joints in various materials and, further, can be used to develop other prediction equations for estimating the brace local buckling strength of K-joints and the ultimate capacity of multi-planar K-joints. In addition, results of a series of tests on complete tubular trusses are summarized, and the hysteretic behavior of trusses that sustain out-of-plane buckling of braces and chords is discussed. After buckling of the members, the joints are subjected to combined loads. The resistance and failure mode of the joints under cyclic loading are described.