SU1368403A1 - Ferroconcrete girder - Google Patents

Abstract

The invention relates to the construction, in particular to reinforced concrete structures of buildings and structures. The purpose of the invention is to increase the carrying capacity and reliability. Reinforced concrete beam is composed of blocks 1, mated with ends at joints 2, Beam is equipped with working longitudinal tensioned reinforcement 3, placed freely in the span without adhesion to concrete, and anchored at beam ends by means of anchors 4. Along the perimeter of each block 1 in the plane of bend of the beam reinforcement 6 is placed, forming a closed loop. The cross-sectional area of the vertical branch of the contour reinforcement 6 located in the block along the drain is determined by the formula (hx) b / R h, where R. is the calculated tensile strength of concrete; h is the full height of the beam cross section; x is the height of the compressed zone of the beam, determined from the equilibrium condition; b is the width of the wall in the middle of the height of the beam section; R is the design resistance to stretching the loop reinforcement. 3 cl. with with affiSESS FZEEE ;;

Description

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The invention relates to the construction, in particular to reinforced concrete structures of buildings and structures.

The purpose of the invention is to increase the carrying capacity and reliability.

Figure 1 shows the beam, a general view; figure 2 - section aa in figure 1 figure 3 - section bb in fig 1.

Reinforced concrete beam includes a beam composed of blocks 1, mated with ends along joints 2, working longitudinal tension reinforcement 3, placed freely in the span without adhesion to concrete and anchored by means of anchors 4 along the ends of the beam. The tension fittings 3 can be located either openly or in channels filled with charging in blocks 1. In any case, fittings 3 are coated with a lubricant made of viscous polymer and placed in a tubular elastic sheath (not shown), Blocks 1 contain spatially reinforcing cage 5, which is insignificant in terms of metal consumption, in order to prevent their damage during transportation, pre-assembly and installation of the beam. Armature j forming a closed loop is placed along the perimeter of each block 1 in the plane of the bend of the beam. At joints 2, indirect fittings 7 are placed at the ends of block I in each joint 2 on part of the faces of block 1, intended for 35 loop fittings 6, is located during operation to receive a hedgehog in block 1 along joint 2, to determine for enlarging, it is collected according to the formula

ke applied a layer of glue (not shown),

It provides solidity compressed f

zones and joint operation in the extended zone 40

 (h-x) 4

Rjh

as an artificial crack, the position of which is known in advance.

The beam under load works as follows

Under the action of transverse load

In the stretched zone of the beam, after opening the reduction, the opening occurs

only joints 2 between blocks 1 With this, depending on the number of in-line reinforcement 3, the size of block 1, the number of joints 2 in the span and the magnitude of the lateral load at the operation stage, it can be controlled

The figure reveals no joints, since there are no other cracks in the beam due to the contour reinforcement 6. Since the working reinforcement 3 does not have adhesion to concrete, it is also inclined

cracks in the wall of the beam under the action of shear forces are not formed.

With an increase in the external load up to the destruction of the beam, only the opening of the joint, which is an artificial transverse crack, occurs. At the same time, unlike analogs to

There are no horizontal cracks between the compressed zone and the body of the beam before the destruction stage over the top of the open joint. Used famous beams with

a work armature without adhesion to concrete, immediately after the formation of transverse cracks in the wall, vertical tensile stresses y occur, In the proposed beam

thanks to the placement along the joints

2 at the ends of 1 vertical branches-contour reinforcement 6, anchored in the compressed and extended zones of the beam by horizontal sections of the closed contour 6, these transverse vertical tensile stresses h are perceived by the vertical reinforcement 6 and thereby prevents the transfer of stretching on concrete and the formation of longitudinal cracks separating the compressed zone from the body of the beam. In order to completely exclude the probability of the formation of these longitudinal cracks, the cross-sectional area of the vertical wind R i (h-x) 4

Rjh

the cross-sectional area of the contour reinforcement located in the beam along one joint;

design tensile strength of concrete; the full height of the cross-section of the beam; the height of the compressed zone of the beam, which is determined by their equilibrium conditions, for T-shaped and I-beam sections, x is taken equal to the average thickness of the compressed flange; wall width in the middle of the beam section height; design tensile strength of the reinforcement of the loop.

Thus, the placement along the reinforcement contour 6, the amount of which along the joint 2 is determined by the above dependence, ensures reliable anchoring of the vertical reinforcement branches 6 and full inclusion in the work for the perception of transverse stretching. Moreover, the amount of stretched reinforcement of circuit 6, parallel to the stretched edge of block 1, determines yuf of the condition for providing the required crack resistance of block 1, and the number of compressed reinforcement 6 should be sufficient to anchor this reinforcement located along the junction 2 in the compressed zone. The presence of reinforcement 6 prevents the formation of longitudinal cracks separating the compressed zone. The proposed beam makes it possible to increase reliability, since the probability of brittle failure of the beam under load is completely eliminated. Its bearing capacity also increases, since it is possible to more fully utilize the durable properties of compressed concrete and working reinforcement 3. In addition, the contour reinforcement 6 is installed with the required protective layer and therefore, for a short opening of the joints 2, this reinforcement does not require additional corrosion protection. The beam is distinguished by high durability, since not only reinforcement 5-7 of block 1, but also working reinforcement 3 is protected against corrosion.

To ensure the tightness of the joint 2 and reduce the magnitude of local (contact) stresses in concrete, a layer of glue based on epoxy resins is placed along the entire height of the compressed zone at the joint 2. To prevent the destruction of concrete in the joint 2 from local compressive stresses in the compressed zone, indirect fittings are placed at the ends of block 1, for example, in the form of welded meshes 7. These signs will increase the load bearing capacity of the beam and eliminate the likelihood of premature failure of the beam ty of concrete in joints 2 beams. In the stretched zone, the junction 2 can either be made dry without filling, or the contact surfaces of the blocks 1 can be coated with a viscous polymer, ensuring the tightness of the joint 2 with a small opening. Placing joints 2 in certain places along the span

allows you to control the width of the openings of the joints and the total displacement of the beam under operating loads. This increases the operational reliability of the beam. In addition, the proposed beam has an increased resistance to the action of transverse forces, characteristic of beams with reinforcement that does not adhere to concrete. This makes it possible to significantly reduce the number of transverse reinforcement, eliminate the injection of channels and reduce the number of longitudinal tension of the reinforcement 3.

The use of the proposed beam, for example, in bridge construction or in long-span coatings of buildings and structures, allows for screening up to 40% of the amount of reinforcement in the wall, by 14% the consumption of high-strength tensile reinforcement, by 10–15% reduction in labor costs For the enlarging assembly, simplify the section shape of the beam , to expand the scope of the construction season, carried out assembly work at low and negative temperatures without additional energy consumption.

Formula of invention

Reinforced concrete beam, including a composite length of reinforced blocks, combined on the ends of transverse joints, and longitudinal tension reinforcement anchored at the ends of the beam and located in the span freely without adhesion to concrete, characterized in that, in order to increase the bearing capacity and reliability, the blocks along the contour in the plane of the bend of the beam are provided with a closed contour reinforcement, and the cross-sectional area of the contour reinforcement in each block along the transverse joints is determined by the formula

Rtt (h-x) - b

0

Where

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i

BUT,

"T h

Rjh is the cross-sectional area of the contour reinforcement located in the block along one single joint; design tensile strength of concrete; the full height of the cross-section of the beam; the height of the compressed zone of the beam, determined from the equilibrium condition, for T-shaped

and I-sections x are taken equal to the average thickness of the compressed shelf;

- wall width in the middle of the beam section height;

- the calculated tensile strength of the reinforcement is consrig .2

at the same time, the transverse joint between the blocks in the compressed zone is made on glue, and indirect fittings are placed at the ends of the joined blocks in this zone.

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Claims (1)

Claim Reinforced concrete beam, including a composite beam along the length of reinforced blocks joined at the ends by transverse joints, and longitudinal tensile reinforcement, anchored at the ends of the beam and located in the span freely without adhesion to concrete, characterized in that, in order to increase the bearing capacity and reliability, blocks along the contour in the plane of bending of the beam are equipped with closed contour reinforcement, and the cross-sectional area of the contour reinforcement in each block along the transverse joint is determined by the formula. ___ i. R _s h ~ ~ 'where A _s is the cross-sectional area of the contour reinforcement located in the block along “one joint; - calculated concrete tensile strength; h is the total height of the cross section of the beam; x - the height of the compressed beam zone, determined from the equilibrium conditions for tee · ^s and I-sections 1368403 x are equal to the average thickness of the compression flange; ' b is the width of the wall in the middle of the height of the beam section; R _g is the calculated tensile strength of the contour reinforcement, while the transverse joint between the blocks in the compressed zone is glued, and indirect reinforcement is placed at the ends of the joined blocks in this zone. in