| 摘要 |
The beam is made by bending the metal sheet to give it dovetail-section ribs along its centre and edges, the centre rib facing in the opposite direction to the edge ribs. The sheet can also be given a V-shaped cross-section, with the flat portions between its centre and edge ribs sloping upwards. The ribs are formed so that their dimensions are smaller than their final shape, allowing them to be fitted together under tension by opening and releasing them, applying an effort to the flat portions.
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