Experimental comparison in hot spot stress between CFCHS and CHS K-joints with gap

摘要

For the purpose of fatigue assessment, the hot spot stresses of welded gap K-joints made of concrete-filled circular hollow sections (CFCHS) subjected to axial loads were investigated by means of the comparison with the same type joints made of circular hollow sections (CHS). The experiments on seven welded CHS K-joints with different non-dimensional joint geometric parameters were carried out firstly, and then these joints were filled with concrete in the chord so that they became CFCHS K-joints and were tested again under the same loading condition as the CHS joints. Hot spot stresses along the intersections between chords and braces for both kinds of joints were measured by means of both linear and quadratic extrapolation methods. The effects of non-dimensional geometric parameters on stress concentration factor (SCF) were presented. It was found that both the joints had similar varying configuration in hot spot stress and similar effects of geometric parameters. In general, the maximum hot spot stress was located at the crown toe, whereas the minimum was located at the crown heel. The hot spot stress at compression area was higher than that at tension area. However,both the joints had quite different magnitude of hot spot stress. The hot spot stress at the CFCHS joint signifi-cantly lower than that at the CHS joint. It is a effective method to decrease stress concentration of tubular joints and then improve fatigue behavior by filling a chord with concrete.