A Treatise On The Principles And Practice Of Dock Engineering

SHED FLOORS. 375 Authorities. Public conveniences, including urinals and w.c., are useful adjuncts. Lighting.—Single storey sheds are best lighted from the roof, either by giass tiles, skylights, or lanterns. Artificial light is also necessary for night time, and during the short days of winter. Gas may be burnt in the form of sunlights, as shown in fig. 372, suspended from the roof by chains, by means of which the frame can be lowered for cleaning purposes. Electricity is a common illuminant, and there are other systems, such as the Kitson light (burning petroleum vapour), the Lucigen light, acetylene, and others, into the relative merits of which it is unnecessary to enter here. The lower fioors of sheds more than one storey in height, will necessarily derive their natural light from the sides, either through windows or glazed panels in the doors. Shed Floors. —The nature of the material employed for the formation of shed floors is of some importance. The area may be paved, flagged, asphalted, tiled, concreted, or timbered, but it must be borne in mind that the dust arising from the wear of a stone surface is exceedingly detrimental to cargoes consisting of cereals. On the other hand, timber platforms are hardly suitable where there is vehicular traffic within the shed, and, from the point of view of fire prevention, their introduction is not to be commended. So-called asphalt floors, consisting of macadam bedded in tar, are flexible, and do not crack or fracture under concentrated moving loads, as sometimes occurs with floors of more rigid materials laid upon a yielding foundation, but their very plasticity is an objectionable feature in warm climates and in situations exposed to the direct heat of the sun’s rays. Natural asphalt forms a smooth, hard, and durable surface. This and a granolithic surface, composed of equal parts of Portland cement and crushed granite, will be found to yield the least amount of dust from attrition. But the former is expensive, and the latter is only adapted to the conditions of ordinary trucking. Where vehicular traffic is heavy, a pavement of granite or whinstone setts, laid in cement on a bed of rock rubble and concrete, will generally be found the most serviceable. Sheds of more than one storey should have upper floors of fireproof, or, at any rate, of fire-resisting material. For this purpose combinations of iron or steel and concrete are generally employed. And as this department of shed construction is of a very important character, some of the more prominent forms will be briefly noticed. The first and earliest type was that formed of a series of iron girders connected by brick arches, the upper surface being levelied with concrete. A later example (fig. 361) is that of a floor, formed by buckled iron plates, rivetted to the upper flanges of plate girders. A concrete covering forms a bed for Staffordshire blue tiles, 1| inches thick. In the instance selected for illustration the iron plates are 52 inches square. A third form of floor, shown in fig. 362, consists of a series of rolled steel joists, 6 by 3 inches, bedded in concrete at a uniform distance apart of