Stress concentration factors of circular chord and square braces K-joints under axial loading

A series of tests were carried out by using the verified finite element model to measure the SCF of circular chord and square braces K-joints with a reasonable range of three important parameters, i.e. β(ratio of brace side length to chord diameter), 2γ(ratio of chord diameter to chord thickness), τ(ratio of brace thickness to chord thickness). Maximum stress concentration factors of circular chord and square braces K-joints under axial loading usually occurred at the heel point on brace and chord sides. Stress concentration factor of toe point in five specimens was all less than 0.4. Maximum stress concentration factors on chord and braces increased as 2γ increased. Maximum stress concentration factors on chord and braces decreased as τ increased. Effect of β on maximum stress concentration factors was very complicated. Compared with 2γ and τ, the influence of β on maximum stress concentration factors was much smaller than that of 2γ and τ. The design rules for the SCFs specified in the CIDECT Design Guide are generally quite conservative for circular chord and square braces K-joints. Finally SCF formula were proposed for circular chord and square braces K-joints under balanced axial loading. It is shown that the SCFs calculated from the proposed unified design equation are generally in agreement with the values calculated from finite element analysis.