动荷载、动应力是指荷载随________不断地变化,或构件在荷载作用下随________不断运动。但只要应力不超过材料的比例极限,________定律仍适用于动应力、动应变的计算
A campus emergency ______ occur at any time of the day or night, weekend, or holiday, with little or no warning.
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