ZHelezobetonnyie skeletons of new type with a tension of armature in the course of installation

Frame ferro-concrete designs with an armature tension in postroechnyih conditions — a perspective direction of building of inhabited and public buildings. Unlike known frame designs in the given system there are no crossbars, it consists only of two elements — columns and plates, therefore is called bezrigelnoy as frame system. Modular elements in the given design unite among themselves in the course of erection without mortgage elements and svarochnyih works, but only at the expense of prepressure of high-strength armature ‐ in two mutually perpendicular directions (fig. 1).

The given system has also other advantages in comparison with known constructive systems which are widely used in building practice (large-panel, frame without prepressure, etc.): in it there are no acting consoles on columns, armaturnyie issues, the quantity of standard sizes is lowered (in the absence of mortgage elements), decisions are possible diverse architecturally-planirovochnye. As a result on 1 m І it is used less than a steel and concrete (because of the best work of concrete owing to compression in two is mutual-perpendicular directions and applications of high-strength preintense armature (K-7, A-U… A-up). Therefore steel overhead charge is lowered to 10-40 %, concrete and labour input — to 20 % and a total cost to — 25 %.

In Russia and republics CIS since 80th years on present time on such technology it has been erected more than hundred 16-storeyed apartment houses and public buildings.

From the beginning of 1984 of State Unitary Enterprise NIIZHB has conducted great volume of settlement-theoretical and developmental works on working out of new technical decisions of the given frame systems for many-storeyed and maloetazhnyih at home with the different sizes of cells to 7,2 m and for various loads to 800-1200 kg/m І (fig. 2). Thus in these workings out, except overlappings, covers, balconies, (loggias) and onboard elements, preintense were as well base (fig. 3) and stropilnyie elements for a roof. These designs can be also national teams from melkoshtuchnyih elements or monolithic in which association and obzhatie also is made by means of preintense armature in postroechnyih conditions. These buildings passed experimental check on krupnorazmernyih fragments and in the course of erection.

Tests of four cells in the size 7,2h6 m of block sections of a skeleton of overlapping (by a brick and blocks) in the course of erection of a many-storeyed apartment house in Moscow are conducted. Measurements of deflections of various plots of overlapping and onboard elements, pressure in contact seams between columns and end faces, torsion of beams in a zone of an arrangement of lifts and a staircase have been conducted. Also defined prepressure in rope armature K-7 in diameter of 15 mm before and after a delay in two points between columns, deformations of the top plots of three-storyed columns at a tension of armature and zagruzhenii vertical loading. At the maximum load (1,2 settlement) it is noted destructions in skeleton elements. At standard load after 15 hours of endurance the greatest deflection has made 6,5 mm (1/900 flights), and at settlement load — 8,8 mm. At the maximum load the deflection reached about 12 mm (1/500 flights). At overlapping unloading the residual deflection has made 2 mm.

Deflections of onboard elements flight of 6-7,2 m at settlement linear load have made 2-3 mm which after complete unloading have decreased to zero.

Movings of the top plots of extreme columns did not exceed 9 mm that it is recommended to consider at skeleton installation.

State Unitary Enterprise NIIZHB suggests to expand a scope of the given frame system: for maloetazhnogo buildings, for reconstruction of buildings of old building (5-storeyed buildings, at change of old overlappings).

The author accumulates experience of use of frame system in maloetazhnom building, the new technology which has allowed to reduce considerably the cost price of 1 m І such housing accommodation is developed. The design of such house consists from malozaglublennyih modular or monolithic ferro-concrete elements with apertures in mutually perpendicular directions established in places of crossing of walls, and between them beams and the preintense armature which anchor after a tension are fixed on the indicated angular elements place raspornyie.

With a thickness considerably smaller, than multihollow floorings, it is offered to produce overlappings between columns and to lift on design level by means of four hydrojacks which are applied to an armature tension. Lifting of overlappings without the crane reduces building cost. Thus building of such house is conducted in two stages: at first only a skeleton (the bases, columns, overlapping and a roof), and then — walls, windows, doors and the equipment for a waterpipe, water drains and electricians (fig. 4). Walls from melkoshtuchnyih elements (blocks, a heater, etc.), and as bearing elements of a roof — prestrained stropilnyie the designs made of easy ferro-concrete parts, buildings united at-sight by means of preintense armature.

Counts of the cost price of such two-storeyed house with a total area about 140 m І with a cellar have shown, that at the first stage of 1 m І costs 35 u.e/m І, and on the second — 120 u.e./m І (in market prices of the end of 2001).

We develop technical decisions of reconstruction of 5-storeyed buildings with three longitudinal bearing walls in which it is possible to use modular elements of factory manufacturing. Such buildings make a significant part of an available housing of many cities of Russia (only in Moscow about 4-5 million in m І), and experts do not recommend them to take down.

In this case it is offered to establish along an old building columns which adjoin one end of a plate of overlapping, and other end they adjoin ferro-concrete elements (the same section, as a column) with the apertures, leaning in deepenings in old walls (brick, block) a facade. Further all system of elements is pressed out in two orthogonal directions by preintense armature.

Offered constructive systems for reconstruction do not require labour-consuming works on warming of old facades which in this case become internal walls. The new effective method in case of need strengthenings of the old bases which does not require great volume of excavations is thus applied, and use of new bearing elements of a roof gives the chance to erect a mansard floor.

— hydrojacks new home equipment is developed for a tension and an anchor for fastening of rope or rod armature, and also equipment for skeleton installation.

Employees NIIZHBa can render the scientific and technical and advisory help, conduct technical support of building objects and participate in designing, in works on a tension, quality assurance, to execute tests of a building, its elements and knots.
N.A. MARKAROV, the doctor tehn. Sciences, the professor, NIIZHB Source: «the Building expert» #19

It is introduced: on January, 24th, 2003

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