| 摘要 |
A fire-retardant roof construction in a building wherein a fire-resistant wall separates a first room from a second room and supports purlins which carry a roof cladding fire-retardant roof construction. A first set of parallel purlins extends over the first room, each having one end pivotally mounted over a horizontal axis parallel to the wall adjacent the top of the wall. A set of upright cleats of sheet metal are secured to the top of the wall, each providing the pivotal mounting for a respective purlin. A second set of parallel purlins extends over the second room, and is mounted on cleats in the manner of the first set. The pivotal mountings are so located that each purlin, if deprived of support elsewhere, can collapse to hang down from its pivot without structural damage to the wall or the respective cleat. A first fireproof curtain seals the walltop space between each adjacent pair of purlins of the first set, and a second fireproof curtain seals the walltop space between each adjacent pair of purlins of the second set. The two curtains define between them a sufficient space so that damage to one curtain from collapsing purlins does not breach the other curtain. A divide in the roof cladding directly over the space provides for controlled separation whereby the cladding can collapse together with its supporting purlins over one room without effect on the purlins, or on the cladding supported by the purlins, of the other room.
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