| 摘要 |
A prop made from an elongate timber element. The cross-sectional area of the element is reduced in at least one region e.g. by tapering the element, forming circumferential grooves in it, or boring holes axially or transversely into or through the element. The region of reduced cross-section is reinforced by means of bands or a sleeve which extends circumferentially around at least part of the region. The reduced cross-sectional area promotes deformation of the prop and the reinforcement controls the rate of deformation.
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