Investigation of hot spot stress for welded tubular K-joints with stiffeners

Abstract

Steel stiffeners can be utilized to reinforce the welded hollow section K-joints, possibly bringing about a different magnitude and distribution of hot spot stress from the traditional joints without stiffeners. There is a lack of knowledge on the hot spot stress and its calculation method for the welded tubular K-joints with stiffeners, especially under complex load cases, which has hindered the fatigue design. With regard to an engineering practice of a bridge under construction, this paper investigates the distribution and magnitude of hot spot stress and its calculation method. Experimental tests including two load cases are conducted to provide a benchmark for the finite element (FE) modelling. FE analysis is carried out to investigate the influence of stiffeners on the hot spot stress ranges at several critical locations, covering the parameters including number, thickness and position of internal ring stiffeners. The hot spot stress calculation method is then developed based on the superposition concept. It is found that the hot spot stress ranges near the stiffeners are relatively large, in addition to those at crowns and saddles. The locations of interest include not only crowns and saddles but also the locations at the intersection of stiffener contours and intersection lines. The maximum hot spot stress ranges can be reduced by 55.7% in chords and 37.4% in braces by setting stiffeners. The developed hot spot stress calculation method is verified for the welded tubular K-joints with stiffeners. In addition, a fatigue test on the welded tubular K-joints with stiffeners is performed. • Investigate the hot spot stress distribution and magnitude of the welded tubular K-joints with stiffeners. • Conduct experimental tests of the specimens in two combined load cases. • Analyze the effects of steel stiffeners on the hot spot stress ranges of welded tubular K-joints using FE modelling method. • Extend the hot spot stress calculation method for the welded tubular K-joints with stiffeners. • Perform a fatigue test on the welded tubular K-joints with stiffeners.