A PRELIMINARY ANALYSIS ON STABILITY OF THE TRAPEZOIDAL WOOD RACK OF THE YONGLE BIG BELL
永乐大钟梯形木架稳定性初探

The YONGLE big bell and the wood-rack for suspending the big bell are valuable antique relics. Their safety and reliability have attracted much attention of scientists and engineers.In the present paper a preliminary study on stability of the trapezoidal wood-rack is carried out.Based on a simplified bending constitutive model of the mortise and tenon joint(in Chinese it is called"MAO-SUN")between beams and pillars of the rack,the influence of the side-angle of the pillars on the stability of the rack is analyzed.The energy method of stability theory of elastic structures and the comparison method are used.The formulas for the critical load are derived for the reduced two dimensional trapezoidal rack structures.The critical loads are computed for the wood-rack with different side-angles,as well as for that without side-angle.The results are compared with each other for different racks with different side-angles.It is concluded that the wood-rack with side-angle has better stability as compared to that without side-angle.The wood rack design with inclined pillars is a typical design of wooden architectures in ancient China and shows the wisdom of designers and craftsmen.