Abstract
The grid structure with welded hollow spherical joints (WHSJs) is widely used in industrial buildings with suspended cranes. Cyclic loadings generated by the suspended cranes could result in the fatigue failure of WHSJs. However, a corresponding fatigue design method has not been established. This paper presents an experimental study on the fatigue performance of the weld toe in the steel tube of WHSJs under axial force. Stress distribution on the joint’s surface was obtained by the static load test. By using the MTS fatigue testing machine, a constant-amplitude fatigue test was performed on the full-scale joint specimens. Twenty effective test data were obtained and fitted to a fatigue S-N curve by the least squares method. The corresponding fatigue design method for allowable stress amplitude was established. The mechanism of fatigue failure at the joint was investigated through microscopic analysis using scanning electron microscopy. The results of this paper can be potentially used as a basis for revising specifications and to promote the practical application of grid structures with WHSJs.
Highlights
Welded hollow spherical joints (WHSJs) are widely used in the grid structures of industrial buildings, aircraft maintenance facilities, and public buildings
For Specimen 1, the perpendicular stresses at the middle of the pipe were 44.08 MPa and 42.64 MPa, which were close to the nominal axial normal stress of 40.87 MPa; for Specimen 2, the perpendicular stresses at the middle of the pipe were 50.06 MPa and 48.41 MPa, which were close to the nominal axial normal of 48.29 MPa. ese indicated that the stress state in the middle of the steel tube was almost the uniaxial stress state
Yan [19] reported that allowable stress amplitude [Δσ]2×106 is 22 MPa at the weld toe in the hollow sphere of WHSJs under axial force. is value is smaller than 66.36 MPa, which is the allowable stress amplitude of the fatigue failure at the weld toe in the steel tube found in this study. erefore, the allowable stress amplitudes of two fatigue failure modes of WHSJs should be categorized into two classes
Summary
Welded hollow spherical joints (WHSJs) are widely used in the grid structures of industrial buildings, aircraft maintenance facilities, and public buildings. Numerical methods were used by Zhao et al [9] to study the effects of corrosion on the flexural stiffness and bending capacity of joints at different locations of WHSJs. there is limited research on the fatigue performance of WHSJs. In industrial buildings, the suspended cranes are often installed on the grid structure to meet the requirements of production. According to the recorded data, lifting the crane once can produce several loading-unloading cycles Based on this, they recommended that fatigue calculations should be carried out on the joints and their connected members which the suspended cranes directly acted on. Yan [19] carried out fatigue tests of 29 full-scale WHSJs, obtained the fatigue S-N curves of weld toe in the hollow sphere, and established a practical fatigue design formula based on the nominal stress amplitude and hot-spot stress amplitude at the spherical surface of the joints
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