| 摘要 |
<p>The free ends of the webs have teeth pointing alternately in opposite directions. The teeth of some or all of the webs take a bar or concrete ring. The rings are fixed in the factory to the sections, and are welded to the teeth. The rings, crenelated, are fixed to the sections by pinching the teeth. The sections are designed in folds to take sheets or blocks of foam between the folds. The sections are joined along overlaps.</p> |
