Cranked Beam 意思係呢條 beam 由 support 至 support 唔係同一水平. 呢條Beam 嘅 elevation 起碼有兩個或以上.
當計 headroom 嘅時候都係由 bottom of beam 度至 top of slab. 小心計算時留意 slab 有cranked, 因為除咗 beam 之外 slab 都有可能會 cranked 造成落底一級嘅效果, 但無論如何 headroom = Elev of bottom of beam - Elev of top of slab.