Vocabulary

rough — грубый

somewhat — отчасти, до некоторой степени

gap — промежуток

to wedge — закреплять клином

inclined — наклонный

inverted — перевернутый

span — расстояние (между опорами арки свода)

to exceed — превышать

voussoir — клинчатый камень

to depart — отступать

inconsistency — несовместимость, несообразность

merit — достоинство

braced — укрепленный

stiffness — жесткость

tubular — трубчатый

The millenium dome

Since the Greenwich meridian and thus the world time finds its origin in Greenwich, in Britain the idea has been conceived that it should be the place where the world should celebrate its step into the new millenium.

The centre of the Millenium celebrations is the Millenium Dome, the largest single public assembly building in the world. The architect of the Dome, Richard Rogers, is famous for such works as the Pompidou Centre, opened in 1977, and the Lloyd's of London building.

The Dome is an exceptional example of building engineering. The Dome itself provides an enclosure for the exhibition to protect the exhi­bits and the visitors from the weather.

The concept of the Dome's roof is apparently very simple. Tensioned steel cables are arranged radially on the surface of the dome and held in space by hangar and tie down cables at 25m intervals. The surface is defined as a spherical cap.

Between the cables, tensioned coated fabric is used as cladding. Both the tensioned cables and cladding carry the loads by deflection accompanied by increase in tension.

The forces in the cables, 40 tonnes in each radial line have to be resisted at the centre where they come together and at the boundary where they are anchored. In the centre of the roof there is a 30m diameter tension ring consisting of 12 — 48mm diameter cables which carry a total of 700 tonnes. At the edge the forces are resisted by vertical ground anchors going 12m down into the gravel layers and horizontally by a concrete ring beam 1000m in circumference which carries the loads in compression.

Vocabulary

to conceive — задумывать, представлять millenium — тысячелетие

cable — кабель, канат, трос

fabric — ткань, материя

cladding — покрытие

deflection — прогиб, провес

to resist — противостоять; выдерживать

to anchor — скреплять, закреплять

layer — слой

circumference — окружность

Floor systems

The continuous slab constitutes a self-contained floor system, though it may be desirable for non-structural reasons to add a separate top surface and a separate ceiling below. Before the development of the reinforced-concrete slab, the nearest equivalents were the floor composed of beams of timber or stone set immediately alongside one another, and the floor provided by a more or less solid fill above a brick or concrete vault. The first of these involved a very extravagant use of material and hence expenditure of effort, so it usually gave way to a more differentiated form with increasing skill in construction. The second was more efficient, inherently strong, and fireproof, and continued to be used for these reasons until supplanted by the reinforced-concrete slab. But it had the drawbacks of greater overall depth than alternative forms, and of greater weight plus the generation of outward thrusts, so that stronger walls were called for.

The alternative to these forms was always some composite system, with beams as the principal spanning and load-bearing elements. In the commonest of these systems, still widely used, light timber beams span at short intervals between opposite walls and are covered by boards or twigs and rammed earth.

Today the usual floor system, apart from intermediate floors within single dwellings, is the reinforced-concrete slab with or without projecting beams. For very heavy loadings and wide spans, a grid of beams within a bay may be used to stiffen and strengthen the slab without requiring it to be of great thickness throughout. In all cases, the slab has a great advantage over the earlier systems because it is a good horizontal diaphragm, binding the walls or columns together and distributing any side loads between them.