門(men)式(shi)起(qi)(qi)(qi)重(zhong)(zhong)機(ji)(ji)(ji)(又稱(cheng)龍(long)門(men)起(qi)(qi)(qi)重(zhong)(zhong)機(ji)(ji)(ji))是橋(qiao)(qiao)(qiao)架通過兩側(ce)支(zhi)(zhi)腿(tui)支(zhi)(zhi)撐在地面(mian)軌道上的橋(qiao)(qiao)(qiao)架型起(qi)(qi)(qi)重(zhong)(zhong)機(ji)(ji)(ji)。在結構上由門(men)架、大車運行機(ji)(ji)(ji)構、起(qi)(qi)(qi)重(zhong)(zhong)小(xiao)車和電氣部分(fen)等(deng)組(zu)成。有的門(men)式(shi)起(qi)(qi)(qi)重(zhong)(zhong)機(ji)(ji)(ji)只(zhi)在一(yi)側(ce)有支(zhi)(zhi)腿(tui)，另一(yi)側(ce)支(zhi)(zhi)撐在廠房或棧橋(qiao)(qiao)(qiao)上運行，稱(cheng)作(zuo)半門(men)式(shi)起(qi)(qi)(qi)重(zhong)(zhong)機(ji)(ji)(ji)。門(men)式(shi)起(qi)(qi)(qi)重(zhong)(zhong)機(ji)(ji)(ji)的門(men)架上部橋(qiao)(qiao)(qiao)架(含主梁(liang)和端(duan)梁(liang))、支(zhi)(zhi)腿(tui)、下橫梁(liang)等(deng)部分(fen)構成。為了擴大起(qi)(qi)(qi)重(zhong)(zhong)機(ji)(ji)(ji)作(zuo)業(ye)范圍，主梁(liang)可(ke)以向(xiang)一(yi)側(ce)或兩側(ce)伸出支(zhi)(zhi)腿(tui)以外(wai)，形成懸臂(bei)。也可(ke)采用帶(dai)臂(bei)架的起(qi)(qi)(qi)重(zhong)(zhong)小(xiao)車，通過臂(bei)架的俯仰(yang)和旋轉擴大起(qi)(qi)(qi)重(zhong)(zhong)機(ji)(ji)(ji)作(zuo)業(ye)范圍。