某承受轴心拉力的钢板用摩擦型高强度螺栓连接,接触面摩擦系数是0.5,栓杆中的预拉力为155KN,栓杆的受剪面是一个,钢板上作用的外拉力为180KN,该连接所需螺栓个数为()
A campus emergency ______ occur at any time of the day or night, weekend, or holiday, with little or no warning.
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