4. Are the statements true or false?

a . Carbon and low-alloying steel are mainly used in metallic structures.

b. ST-3 steel is traditionally applied in construction.

c. Trusses are less economical than beams.

d. Depending on the load and functional purpose all columns can be triangle, brace-shaped, cross-shaped, diamond-shaped and others.

e. To transmit the horizontal loads acting on a building stand structures are used.

f. Steel trusses are used for hangars and garages.

g. Frame systems are less expensive than beam structures.

h. Arch coverings are often used in civil buildings and trusses with parallel chords are basically used for industrial buildings.

i. Metallic structures are widely used in industrial and civil construction.

j. Trusses can be of two types.

4. Insert the scheme of different types of metallic constructions. Then use it as a plan to retell the text.

Metallic structures

Beams

Trusses

Steel columns

triangle

Frames

Arches

5 . The role game. Imagine that you are an architect; you have won the tender for the school construction design. Discuss with your colleagues the types of metallic constructions to be used for:

• ceilings

• foundation

• floors

• walls

• roof

TEXT II. APPLICATION OF METALLIC SYSTEMS

Metallic systems in service can be seen in the constructions of bridges, skyscrapers, metallic membranes and other systems. The construction of different types bridges involves metallic systems.

T he metallic constructions of arch type bridges are arches and semi-arches where the road bed is mounted both over the arch or under it. Suspension bridges contain metallic pillars as supporting constructions. They are embedded into the banks of the river, channel. Cables are strained through the pillars and the road bed is fixed on them.

A Shrouds bridge is the sort of a suspension bridge but it has extra-supporting in its central part. A beam bridge has trusses and beams in its base from which the metallic constructions are formed, the spans of the bridge. Pontoon bridges are seasonal or temporary crossings. The main part of a pontoon bridge is a metallic hollow cylinder welded on the edges. Pontoons have so high carrying capacity that they can carry bridges, transport, piers. Extra metallic constructions such as rails, stairs, railings are necessary not only for bridges but for buildings and other objects.

The construction of skyscrapers is impossible without metallic constructions. They are the framework of any skyscraper. Reinforced concrete is only suitable for the buildings under 15 storeys. Metallic systems are the key element of a 100-storey skyscraper framework.

T he recent years saw the wide use of metallic membranes. They are thin-shelled suspending systems subjected to bending stress in the least degree. The major advantages of such systems are the combination of load-bearing and enclosing functions and fabrication. Fabricated in advance metallic sheets are delivered to the site where the whole membrane is constructed without scaffold. The Olympic stadiums in Moscow and in Sochi can serve the examples of such metallic coverings. The cycle track covering in Moscow was made with the help of two metallic membranes of Gausse curve. These membranes can resist to vertical and horizontal loads.

O ne of the greatest examples of metallic constructions is the Eiffel Tower, the symbol of Paris. It is the whole metallic installation. Its initial function was the entrance gates to Paris. It was planned as a temporary construction. The radio antennae on its top saved it from the disassembly. It was designed in the shape of a pyramid to resist wind loads. Modern architects say the metal of the Eiffel Tower will be enough for three towers, the constructive material was overused. The tower has a concrete foundation. Most TV towers are metallic constructions with triangle frameworks of trusses (usually). They are hard, easy-assembled and disassembled.

TASKS