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ABSTRACT

Connecting The Elements Of Reinforced Concrete

Structures Protection Of Reinforced Concrete Coverings

Mirzaakhmedov Abdukhalim Takhirovich

Candidate Of Technical Sciences, Associate Professor, Department Of Construction Of

Buildings And Structures, Fergana Polytechnic Institute, Fergana, Uzbekistan

Mirzaakhmedova Ugiloy Abdukhalimjohnovna

Senior Lecturer, Department Of Construction Of Buildings And Structures, Fergana

 Polytechnic Institute, Fergana, Uzbekistan

Reinforcement, Connection Of Elements.

INTRODUCTION

The joints of reinforced concrete structures must ensure reliable transmission of forces and the joint work of reinforced concrete elements; they should be located in places where the least effort is applied.

MATERIALS, DESIGNS AND PROTOTYPING

At 9 points, it is not allowed to use reinforcing ropes and rod reinforcement with a diameter of more than 28 mm without special anchors (since this is not economically viable due to the long anchoring length).

The angle of fracture of the axes of rod reinforcement of classes A500, A600, B500 and A400 (grade 25G2S) with a diameter of up to 40 mm, made by arc welding, should not exceed 6⁰, and for other types of welding – 3⁰In the meshes, it is allowed not to accidentally weld no more than 2% of the intersections of the rods, and in the frames all intersections must be welded. Cutting the ends of the rods with an electric arc during the assembly of structures or cutting the edges of the rods is not allowed

[1].

It should be noted that the replacement of conventional precast concrete products (most often floor slabs or columns) with prestressed ones has almost no effect on the seismic resistance of the structure and can be justified where there are restrictions on deflections or crack opening (should not be confused with technologies such as preliminary compression of the building as a whole or prefabricated floors of the entire floor with a ring cable).

EXPERIMENTAL RESEARCH TECHNIQUE

In prestressed structures, it is not allowed to use reinforcement for which the relative elongation after rupture is less than 2%. When designing rod structures (beams, columns), according to recent publications, it is recommended to take into account the following features: 

a)      Longitudinal reinforcement must have a cross-sectional area of at least 0.1% of the element's cross-sectional area;

b)      Transverse reinforcement in sections of the element with a length of 2h (where h is the height of the element section) adjacent to the rigid corners of the frames must meet the following requirements (where d is the diameter of the longitudinal reinforcement): - the step of the clamps should be no more than: - at 7 points - 1 / 2h, 15d, 150mm; - at 8 points - 1 / 3h, 12d, 100 mm; - with 9 points - 1 / 4h, 10d, 65 mm; - the diameter of the transverse reinforcement must be at least 8 mm [2,3,4.].

Figure 1. - Construction scrap: longitudinal reinforcement is broken; longitudinal and transverse reinforcement are not interconnected; longitudinal reinforcement has a bending stiffness greater than the concrete cover

c)      Welded and mechanical joints of install additional transverse reinforcement longitudinal reinforcement can be in the joint area; performed in any section, and overlapping e) When connecting with an overlap in the joints should be located outside the zone bypass zone, frequent clamps should be of action of the maximum moments; installed with a pitch of at least h / 4, 8d and

d)      For welded and mechanical joints of 100 mm; longitudinal reinforcement in each section, f) The ends of the knitted transverse no more than every second bar should be reinforcement clamps must be bent connected, while the distance between the around the longitudinal reinforcement bar joints along the length of the element must and inserted into the concrete core for a be at least 100 mm (Figure 2), and if the length of at least 6 dsw; bars are joined with eccentricity, then

Figure 2. – Connection longitudinal reinforcement

g)      The ends are not brought into the concrete core; subsequent seismic failure; correct location of the clamps (Figure 3.)

The ends are not Subsequent seismic Correct arrangement routed inside the destruction of clamps concrete core

Figure 3. - Connection of transverse reinforcement

h)      the length of welded seams and bypass of recommended to be taken 30% more than reinforcement when overlapping is that established by the joint venture

        "Concrete      and      Reinforced       Concrete

Structures" [5,6,8].

When designing planar structures (walls, diaphragms), it is recommended to take into account the following features:

•       Along the edges of load-bearing wall elements, concentrated longitudinal vertical reinforcement with a crosssectional area of at least 0.05% of the crosssectional area of the wall should be provided;

•       Along the field of the wall at both side faces, horizontal reinforcement with a total cross-sectional area of at least 0.1% of the area of the corresponding crosssection of the wall element should be provided;

•       The reinforcement distributed along the lateral sides of the wall must be secured against buckling by means of special transverse rods;

•       At the intersections of walls, in places of sharp changes in wall thickness and at the edges of openings, constructive

reinforcement should be provided;

•       In the butt joints of wall elements, it is necessary to provide for the installation of reinforcing or other steel ties, securely behind the anchor ones in concrete. With a seismicity of 9 points for buildings with a height of 5 floors and higher, the crosssection of steel ties is taken to be at least 1 cm² per 1 running meter. m of the joint, and at 7–8 points - not less than 0.5 cm².

The axial compressive strength class of walls is established taking into account the concrete for external and internal load-bearing strength requirements for the main combination of loads, ensuring operational transportation and installation, but should not properties, conditions for stripping, be less than the values specified in Table 1.

Table 1 - Minimum classes of concrete for load-bearing walls of earthquake-resistant buildings

structural solutions for floors made of precast outlets or embedded parts on the ends (Figure concrete slabs with a corrugated or keyed 6).

Figure 6. - Types of precast concrete slabs.

CONCLUSION 

Type 1. Seams between slabs are filled with cement or polymer-cement mortar, or finegrained concrete of class B 7.5 or higher. The slabs are anchored into anti-seismic belts, reinforced concrete straps or girders.

At the level of supporting the hollow-core panels, reinforced concrete straps are arranged on the crossbars of rectangular crosssection, reinforced along the intermediate frames with flat frames, and along the extreme end rows - with spatial frames.

When supporting hollow-core panels on the top of the crossbars, they must be provided with connections in the form of vertical outlets of reinforcement with a diameter of at least 16 mm with a step of 300-400 mm.

Type 2. Anchoring of slabs is provided in the same way as for type I. Floor slabs are laid with a distance of at least 120 mm.

Between the slabs, a reinforcement cage is installed with four longitudinal reinforcement rods with a diameter of 8 mm, which are anchored into antiseismic belts 35 or reinforced concrete straps. Monolithic concrete, fine-grained class B 15.

Type 3. Structural solutions for anchoring and embedding slabs are the same as for type 2, but, in addition, a 50 mm layer of fine-grained concrete of class B 15 or higher, reinforced with a mesh of reinforcement with a diameter of 4 mm with a cell of 500, is provided on the top of the floor. mm [7].

The support of floor slabs, depending on the type of supporting structures, should be taken at least: - on brick and stone walls - 120 mm; - on walls made of vibrated brick blocks - 90 mm; - for precast reinforced concrete girders - 80 mm; - on the walls of large-panel buildings: - when supported along the contour or on three sides - 60 mm; - when supported on two opposite sides - 90 mm; - on walls (diaphragms) made of monolithic reinforced concrete - 90 mm.

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