Constant Amplitude Fatigue Calculative Method of Welded Hollow Spherical Joint with Cross-Board in Steel Plate-Type Grid Structure

The fatigue of grid structures with welded hollow spherical joint under suspending cranes is an issue in both academic and engineering fields at home and abroad. The structural fatigue is mainly caused by the fatigue failure of welded hollow spherical joint with cross-board. In this paper, 16 specimens categorized in KQ-4、KQ-5 and KQ-7were tested stably and efficiently under constant amplitude stress by use of self-designed loading equipment. The testing results show that the form and mechanism of fatigue failure were clarified elementarily. A fatigue curve of welded hollow spherical joint with cross-board, S-N curve, was suggested in this paper based on the statistic regression analysis of the 16 testing results. The constant amplitude fatigue calculation method was established for welded hollow spherical joint with cross-board in grid structure with welded hollow spherical joint by use of allowable stress amplitude method.