由于形势发展的需要,不少建筑物底部设有人防,当采用装配式结构时,履带起重机需在人防顶板上行走和吊装,如采用跨外吊装,起重机吨级需增大很多,在经济上不合算,为此需了解和掌握履带对人防的荷载,以利事先采取必要措施确保安全。如路基箱与人防顶板接触要平正,不平时必须铺以黄砂或采用较宽的路基箱,就可避免不必要的经济损失(如盲目增加受弯钢筋,人防顶板下面加支撑等)。现分别介绍几种计算方法: Due to the development of the situation, many buildings are equipped with air defenses at the bottom of the building. When an assembled structure is used, the crawler cranes must be walked and hoisted on the air defense roof. If the cranes are used for cross-lifting, the tonnage of the cranes needs to be increased greatly, and economically. It is not cost-effective to understand and grasp the load on the civil air defenses in order to facilitate the necessary advance measures to ensure safety. For example, the contact between the road base box and the air-defense roof should be level, if it is not smooth, it must be covered with yellow sand or a wider roadbed to avoid unnecessary economic losses (such as increasing the steel bar blindly, adding support under the air-defense roof, etc.). Several calculation methods are introduced separately: