Trusses and space frames

Trusses and space frames are assemblies of linear members that act primarily in axial tension or compression as ties or struts. The term truss denotes an assembly in one plane, and the term space frame describes a three-dimensional assembly in which the interconnections are such that a load at any point is distributed in all directions through the assembly. The joints need not be rigid and, ideally, should allow free relative rotations of the members. But they must be capable of transmitting tension as well as compression. The usual role in a building is of carrying a roof— in place of the arch, dome, vault, beam, or slab. In the early 19^th century, the true timber truss, necessarily somewhat elaborated and with the bottom tie made from shorter lengths of timber with lapped joints, was stretched to span about 150 ft. (45m); but the first wide-span iron roofs (of basically arched form) had then been built, and future development was in iron and steel. With the introduction of wrought iron for the ties, there was a clearer differentiation between these and the struts that was carried over into steel construction. Because there was no risk of the ties buckling, they were made appreciably more slender.

The most important space frames are lighter framed equivalents of domes and vaults, or of slabs spanning in two or more directions simultaneously. The framed dome is a very early form, particularly if we include primitive dome-shaped huts. But even in fully developed timber-framing systems, the ribs were invariably aligned radially and circumferentially, and the system was then braced by additional diagonals or by the outer covering. Early iron-framed domes merely reproduced this timber form, and it was only in the second half of the 19^th century that an inherently stiff, triangulated pattern of framing was substituted. This might be regarded as the first true space frame.

Further development of the framed dome or vault has taken place almost entirely in the 20^th century and has lagged somewhat behind parallel developments in airframe structures, where there was a greater incentive to seek the most efficient use of material to save weight.

Vocabulary

truss — ферма, связь, стропильная ферма

assembly — монтаж, сборка

strut — стойка, подкос, распорка

plane — плоскость

joint — узел (фермы)

to lap — перекрывать в напуск, соединять внахлестку

buckle — изгиб, прогиб (вертикальный)

simultaneously — одновременно

to align — выстраивать в линию, ставить в ряд, выравнивать

to lag (behind) — запаздывать, отставать

incentive — стимул

to seek — искать

/. Choose the right modal verb.

1. The joints... not be rigid.

a) must b) can c) need

Translate this text.

11.THE ARCHITECTURE OF THE 80^th CENTURY

Warming up

1. Why is this style called Constructivism?

2. What are its main features?

3. What famous Constructivists do you know?

Text 1. Read the text and tell about the most famous works of this style.