圈上序大峰 Safety of threaded fastener 2009年04月22日新华社 口塔吊断裂事故原 因系该塔吊螺栓 断裂导致 口塔吊第二节斜支撑 处上方连接螺栓断 裂，导致塔吊倾覆 圆上泽夫通大学 Operation of Bolt Clamping load stretches or elongates bolt with tensile force Fi,called bolt preload The clamping force that produces tension in the bolt induces compression in the members The bolt and nut compress members together with preload force Fi,which existed forever 1111  塔吊断裂事故原 因系该塔吊螺栓 断裂导致 2009年04月22日 新华社  塔吊第二节斜支撑 处上方连接螺栓断 裂，导致塔吊倾覆 Safety of threaded fastener Operation of Bolt  Clamping load stretches or elongates bolt with tensile force Fi , called bolt preload  The clamping force that produces tension in the bolt induces compression in the members  The bolt and nut compress members together with preload force Fi , which existed forever