Experimental study of hot spot stress for three-planar tubular Y-joint: I. Basic loads

Abstract

Various tubular joints of offshore wind turbines (OWTs) have seen rapid development in the past decades. However, experimental studies on multiplanar tubular joints have mainly been underexplored. This study designed and constructed a multiplanar loading experimental system for multiplanar tubular joints. A model test was performed using this system to investigate the hot spot stress (HSS) of a three-planar tubular Y-joint, which is critical for the fatigue design of a tripod substructure. The HSS distribution along the weld seams under the 12 basic load cases was obtained from the test analysis. The geometric stresses at the key positions of the chord and brace sides were obtained and analysed. The peak values of stress concentration factor (SCF) were obtained and compared with those calculated using the method recommended by the codes. An indirect method that explicitly considers the interaction between multiple braces was proposed and verified to calculate the SCF distribution of multiplanar tubular joints.