Construction fittings – yesterday and today

Recommendation points

• Characteristics and classification of construction fittings
• Basic requirements for building fittings:
• Construction fittings are divided into:
• Scope of construction fittings

The first to use metal beams to strengthen the structure of the building were the Greeks, who used reinforcement more than two thousand years ago – in 470 BC. on about. Sicily. However, the use of reinforcement in brickwork did not give the desired results – the metal reacted with moisture penetrating through the seams in the masonry, the resulting corrosion violated the strength of the wall.

Therefore, the use of reinforcement in construction is inextricably linked with the invention of cement – this is how reinforced concrete appeared, combining two properties: concrete compression and reinforcement elongation. Reinforcement in the composition of reinforced concrete is practically not subject to corrosion.

Construction reinforcement is made from hot-rolled steel, produced in two types – in the form of a smooth round metal rod and a round metal rod with surface protrusions.

Characteristics and classification of construction fittings

By definition, fittings are devices and parts that are not included in the main composition of parts of any structures and structures, but ensure their efficient operation..

The main construction fittings are manufactured in accordance with GOST 5781-82. It differs in profile types, purpose, production technology. The reinforcement of the periodic profile has corrugation applied to the rods – uniform and at a certain angle to the longitudinal axis. Round reinforcement – a rounded bar, along the length of which two longitudinal ribs and transverse protrusions are applied, running along a helical line in three passes. Smooth reinforcement does not have any corrugations on the rods.

There are several classes of construction reinforcement, depending on the physical and mechanical strength properties: from A-I to A-VI, each of the classes is made of steel of certain grades. Reinforcing steel grade (for example A500) may have an addition in the form of letters, behind which are the following qualities: “t” – heat-hardened (example – A500t), “c” – reinforcement for welding, “k” – high resistance to corrosion, ” c “- the reinforcement is strengthened by a hood.

Basic requirements for building fittings:

• high indicators of strength and ductility;
• rigid and durable adhesion to concrete;
• minimum spacing in concrete products;
• efficient welding;
• resistance to corrosion and metal fatigue.

Construction fittings are divided into:

• by the main material: steel and non-metal;
• by the production method: wire, rope and rod;
• along the profile: round, smooth and with a periodic profile;
• according to the functions performed: for tensioned and non-stressed;
• by purpose: for assembly, distribution and work;
• by mounting method: knitted (frame, mesh) and welded.

The main GOST, according to which the production of fittings is currently underway, is GOST 1088-94 and the conditions of STO ASChM 7-93. The periodic profile of such building reinforcement has a crescent corrugation, where the transverse ribs do not intersect with the longitudinal ones, in contrast to the annular profile (GOST 5781-82). The crescent corrugated profile is widely used in European countries and has its own European standard – EN-10080-1 (1998). It should be noted that both the annular and crescent-shaped reinforcing profiles have their own disadvantages: the annular connection of the ribs reduces the strength of the bar, concentrating the stress at the junction; the properties of the crescent profile in terms of stiffness and adhesion to concrete are lower than those of the ring profile. Rolled metal manufacturers are currently researching new types of reinforcing profiles to improve their performance..

Reinforcing steels in accordance with GOST 5781 have mechanical properties associated with the chemical composition of the steel. For the manufacture of reinforcing profiles, carbon steels (3-5sp), alloyed with silicon and manganese (25G2S, 35GS) are used. Extra strong steels are alloyed with titanium and chromium (23Kh2G2Ts, 23Kh2G2T). The standard length of hot rolled rebar is 6.8-11.2m, in rare cases up to 25m.

Scope of construction fittings

Over the past decades, the technique of monolithic concreting has been widely used in the construction of buildings and structures. The object, rebuilt using this technology, acquires high strength qualities, not to mention the aesthetic appeal of such buildings. Construction reinforcement in the composition of concrete serves as a connecting frame, a kind of skeleton, reliably anchored in concrete, thanks to its corrugated surface.

All large structures in recent decades have been built using the technique of monolithic concreting. Dams and hydroelectric power plants, dams and bridges, public and civil buildings – all were built using concrete reinforced with structural reinforcement of certain grades.

The most common use of reinforcement is as one of the main components of reinforced concrete products, from floor slabs to statues and pedestals..

Construction reinforcement is used in the most critical building structures, therefore, its characteristics must be invariably high.