橋式起重機主梁為什麼要保持一定的上拱度形狀

    橋qiao式shi起qi重zhong機ji的de兩liang個ge主zhu梁liang都dou製zhi成cheng均jun勻yun向xiang上shang拱gong起qi的de形xing狀zhuang，稱cheng上shang拱gong度du。橋qiao式shi起qi重zhong機ji製zhi成cheng一yi定ding上shang拱gong度du的de形xing狀zhuang
，是shi防fang止zhi起qi重zhong機ji在zai吊diao物wu時shi，主zhu梁liang產chan生sheng下xia撓nao
；jinliangjianshaoxiaochezaidiaowuyunxingzhongchanshengdefujiazulihuozixinghuadong。ciwai
，juyouyidingdeshanggongdu，dangqizhongjidiaoqifuheshi，nengshidacheyunxingjigouchuyujiaoyoulidegongzuozhuangtai。

    上拱度的拱值規定為跨度的1／1000。