RU2477773C1 - Method to manufacture guncrete elements of steel double-branch pillar - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: double-branch pillar comprises branches connected with a grid. Each guncrete element of a pillar is made of an oval profile, into which expanding concrete is injected along a concrete line. The profile being a shell rotates around the longitudinal axis, and concrete is thrown by centrifugal forces to shell walls. Centrifugal forces compact concrete, and excessive moisture is squeezed out from it. Steam is sent to the central channel, concrete is steamed from inside, and rotation is stopped. The produced finished branches are connected with a grid from elements of box-shaped section. The base of branches is equipped with anchor beams, which connect branches, and branch heads - with flanges. A cross beam is attached to flanges with bolts, and the upper guncrete part of the pillar is fixed to the cross beam. The inner channels are used to let cooling water through in order to increase fire resistance of the structure.

EFFECT: increased durability and bearing capacity, simplified technological process and reduced labour intensiveness of frame erection.

11 dwg

Description

The invention relates to the construction of reinforced concrete frames of industrial and civil buildings from concrete elements.

Reinforced concrete structures are subject to corrosion of concrete and reinforcement [1, p.255], [2]. Corrosion of the reinforcement inside the section of the column or beam is especially dangerous. Corrosion products have a volume of almost two (1.91) times greater than the initial volume of steel. Therefore, internal pressure is created inside the reinforced concrete section, easily cracking concrete. This leads to peeling and collapse of the protective layer. So at the CHPP-1 in Penza, built in 1943, having reinforced concrete columns with a cross section of 1400 × 700 mm with a protective layer of 75 mm, a sharp decrease in the bearing capacity was observed when the protective layer of concrete collapsed on the columns. The initial cross-sectional area of the column is A * = 140 · 70 = 9800 cm ² (100%).

After the collapse of the protective layer at the zero mark, a decrease in the dimensions of the cross section 140-2 · 7.5 = 125 cm and 75-2 · 7.5 = 60 cm. The cross-sectional area also decreased A = 125 · 60 = 7500 cm ² (76.5 %). The reduction in cross-sectional area was 24.5%. The decrease in the bearing capacity of the entire column is much larger, since as a result of corrosion the area of reinforcement flow also decreased by 20 ... 25%. The decrease in the bearing capacity of the columns is significant. In addition, ulcerative corrosion of the reinforcement is observed, which is especially dangerous.

During the examination it was found that the more stressed reinforced concrete consoles of the columns of the frame of the CHPP-1 are more affected by corrosion than other less stressed zones of the frame of the structure [3].

Thus, the durability of reinforced concrete frames of buildings, as a result of corrosion of concrete and reinforcement, decreases and becomes insufficient. The relevance of developing designs that are more resistant to external aggressive influences is growing!

For the prototype we take a method of reinforcing reinforced concrete columns, proposed by K. K. Nezhdanov and developed with graduate students [4, RU No. 2274719].

In the prototype, a method of reinforcing a reinforced concrete column that has lost its bearing capacity as a result of corrosion of concrete and reinforcement is as follows.

The surface of a reinforced concrete column that has lost its bearing capacity is treated by notching and moistening it. The holder is made of a steel pipe, oval in cross section with a ratio of a larger to a smaller size equal to three. The pipe is cut lengthwise, the damaged column is enclosed inside a steel cage, orienting its large axis of the section in the plane of the eccentricity of the application of longitudinal compressive force, and reduce the eccentricity.

Hermetically connect the two halves of the oval section into a single unit and fill the cavity between the steel holder and the damaged column with expanding fine-grained concrete, pumping it through the nozzles in the cavity in a "bottom up" manner.

Concrete is compacted by vibrating with deep vibrators and when setting it, the section is preliminarily strained, squeezing it on all sides with a steel cage, transforming the column into pipe concrete and thereby reinforcing the entire structure.

It is also known that after deformation of a cylindrical pipe section from the sides and giving it an elliptical cross-section, a significant increase in the moment of resistance W _X relative to the main horizontal axis X of the oval section occurs [5, No. 2191154], [6, patent No. 2192381], [7, patent No. 2304479]. Therefore, it is advantageous to use a clip from a steel oval pipe.

Known frame structures with oval cross-section of the concrete columns [8, patent No. 2319811], [9, patent No. 2319817]. Also known is a method of eliminating the possibility of collapse of metal structures of the frame from fire [10, patent No. 2411330].

The technical task of the invention is to increase the durability and bearing capacity of the reinforced concrete frame of the building by applying external surface reinforcement of expandable steel oval to a cross-section with a ferrule that compresses the concrete core, which also performs the function of protecting concrete from corrosion, as well as simplifying the process of erecting a building frame and reducing the complexity of its construction .

The technical task of increasing the bearing capacity and durability of the reinforced concrete frame of the building is implemented as follows.

The column is performed with a ledge to support the crane beams. The column contains the lower two-branch part below the ledge and the upper part above the ledge. The parts are connected in a single unit by a traverse.

Each pipe-concrete element of the column is made of an oval profile with a ratio of a larger to a smaller dimension equal to three. The expanding concrete is pumped through the concrete pipeline and the oval profile, which is fastened around the longitudinal axis, is a cage, centrifugal forces discarding (centrifuging) plastic expanding concrete at the periphery to the walls of the cage, compacting and squeezing excess moisture out of it, which improves the water-cement ratio. Then steam is fed into the central channel and, without stopping rotation, the concrete is steamed from the inside. When set, the concrete expands, comprehensively bursting the outer cage from the inside, and the cage prevents expansion, comprehensively compresses the concrete from the outside and increases its strength. After setting concrete, ready-made pipe-concrete elements of a two-branch column are obtained.

The larger sectional dimension of each of the branches of the lower part of the column is oriented from the plane of the frame, and the upper part in the plane of the frame (in the eccentricity plane). The branches are connected by a lattice of box-shaped elements. The base of the branches of the column is equipped with anchor beams connecting the branches. The heads of the branches are provided with flanges. Traverse attached to the flanges with high-life bolts. The traverse can be performed, for example, from an oval profile with a ratio of a larger to a smaller dimension equal to three.

To support the crane beam on an oval beam, a saddle-shaped support is mounted. The saddle-shaped support consists of a T-member located along the yoke and welded to it along the edges of the longitudinal ribs. Oval holes are made in the tee's shelf, aligned with the counter holes in the lower belts of adjacent crane beams, for connecting the crane beam with anchor bolts to the saddle-shaped support, with the possibility of transverse straightening. The oval beam has stiffeners.

The upper pipe-concrete part of the column is attached to the traverse and a single structure is obtained - a two-branch pipe-concrete column.

Inside each pipe-concrete element there is a channel used to increase the fire resistance of the structure. When a fire occurs and the temperature rises, the sensor gives an alarm and the chilled water supply automatically switches on, heating the two-branch pipe-concrete column to within acceptable limits.

An anchor beam joins the foundation with an anchor bolt equipped with a straightening nut.

Crane beams are uncorrectedly mounted above the center of gravity of the lower part of the column and are pivotally attached to the traverse with anchor bolts, with the possibility of transverse straightening of the crane beams to restore their design position.

At the same time, the upper part of the column is installed in relation to the lower part of the column with eccentricity e to the outside of the building, with a minimum clearance Δ _min between the inner face of the upper part of the column and the side crane projecting outward.

The outer belt of the brake beam is bolted to a table welded to the top of the column, also with the possibility of transverse straightening it.

Figure 1 shows the junction of the oval pipe-concrete branches of the column with an oval cross-section of the hollow beam, the junction of the beam with a saddle-shaped support and the upper oval pipe-concrete part of the column;

figure 2 shows a cross-section of a two-branch pipe-concrete columns;

figure 3 is a side view of figure 1;

figure 4 - node pairing branches of the column with the elements of the lattice;

figure 5 is a section of an oval pipe-concrete upper part of the column;

figure 6 - node pairing branches of the column with anchor beams;

Fig.7 is a top view of Fig.6;

in Fig.8 is a top view in Fig.1;

figure 9 is a diagram of the determination of forces in the outer branches of the column;

figure 10 is a diagram of the determination of forces in the inner branches of the column;

figure 11 is a design diagram of the lattice of the column.

The column is carried out with a step to support the crane beams. The column contains a lower two-branch part below the ledge (inner branch - 1; external branch - 2) and the upper part 3 above the ledge. The parts are connected in a single whole traverse 4.

Each pipe-concrete element of the column is made of an oval profile with a ratio of a larger to a smaller dimension equal to three. The expanding concrete is pumped through the concrete pipeline and the oval profile, which is fastened around the longitudinal axis, is a cage, centrifugal forces discarding (centrifuging) plastic expanding concrete at the periphery to the walls of the cage, compacting and squeezing excess moisture out of it, which improves the water-cement ratio. Then steam is fed into the central channel and, without stopping rotation, the concrete is steamed from the inside. When set, the concrete expands, comprehensively bursting the outer cage from the inside, and the cage prevents expansion, comprehensively compresses the concrete from the outside and increases its strength. After setting concrete, ready-made pipe-concrete elements of a two-branch column are obtained.

The larger sectional dimension of each of the branches of the lower part of the column is oriented from the plane of the frame, and the upper part in the plane of the frame (in the eccentricity plane). The branches are connected by a lattice of box-shaped profile elements 5. The base of the branches of the column 6 is equipped with anchor beams 7 connecting the branches. The heads of the branches are provided with flanges 8. The beam is connected to the flanges with high-life bolts 9. The beam can be made, for example, from an oval profile with a ratio of a larger to a smaller size equal to three.

To support the crane beam, an saddle-shaped support 10 is mounted on the oval cross-beam 10. The saddle-shaped support consists of a T-element 11 located along the cross-beam and welded to it along the edges of the longitudinal ribs 12. Oval holes (⌀60 and 33 mm) coaxial with the counter holes are made in the flange of the T-section. in the lower belts of adjacent crane beams, for connecting the crane beam with anchor bolts to the saddle-shaped support, with the possibility of transverse straightening. The oval beam has stiffeners 13.

The upper pipe-concrete part 3 of the column is connected to the traverse and a single structure is obtained - a two-branch pipe-concrete column.

There is a ⌀50 mm channel inside each pipe-concrete element, which is used to increase the fire resistance of the structure. When a fire occurs and the temperature rises, the sensor gives an alarm and the chilled water supply automatically switches on, heating the two-branch pipe-concrete column to within acceptable limits.

In the base of the column 6 there is an opening for the flow of water 14. Anchor beam 7 is attached to the foundation 15 with anchor bolts (axis of anchor bolts 16) equipped with straightening nuts.

Crane beams are uncorrectedly mounted above the center of gravity of the lower part of the column and are pivotally attached to the traverse with anchor bolts, with the possibility of transverse straightening of the crane beams to restore their design position.

At the same time, the upper part of the column is installed in relation to the lower part of the column with eccentricity e to the outside of the building, with a minimum clearance Δ _min between the inner face of the upper part of the column and the side crane projecting outward.

The outer belt of the brake beam is bolted to a table welded to the top of the column, also with the possibility of transverse straightening it.

The difference is that both branches of the column and the upper part of the column are made of prefabricated concrete elements made by centrifugation. This method allows you to compact the concrete mixture and squeeze out excess moisture from it, which improves the water-cement ratio, increases the strength of concrete. An increase in the strength of concrete occurs also due to the compression of it with a steel cage.

The economic effect was achieved by reducing the complexity of manufacturing, reducing material consumption and increasing the bearing capacity of the structure. The use of surface reinforcement increases the durability of the structure, protects concrete from corrosion, increases the manufacturability of the building frame.

Concrete implementation example

It is necessary to compare the new solution for the design of the two-branch column with the already known technical solutions. Let us compare a two-branch column with branches with a cross section of an I-beam with a column whose branches have an oval pipe-concrete section.

Calculation of the bottom of the column

Stresses are given in MPa (megapascals), so for convenience we will measure the acting forces in gN (hectonewtons).

Then 1 MPa = 10 ⁶ N / m ² = 1 N / mm ² = 100 N / cm ² = 1 gN / cm ² .

The material of the steel beam is С255 GOST 27772-88 (V St3 sp5) with design resistance: with bending R _y = 230 MPa, with a shear R _cf = 0.58 · R _y = 133.4 MPa.

We determine the longitudinal force in the outer branch of the column (the force determination circuit is shown in Fig. 9):

M _max = 74529 gN · m

N _respectively = 33401 gN

∑М _о = 0

-N _{lower in} 150 + M + N _respectively 75 = 0

Having received the required area A _tr , according to assortment we select a column of I-beam profile 155B2 with the following characteristics:

A _f = 124.75 cm ² ;

i _x = 22.43 cm;

i _y = 4.7 cm

and oval section from a pipe трубы530 mm with the following characteristics:

And _f = 115 cm ² ;

i _x = 24.0 cm;

i _y = 7.2 cm

We determine the longitudinal force in the inner branch (the force determination circuit is shown in Fig. 10):

M _min = 43837 gNm

N _respectively = 27434 gN

∑М _о = 0

-MN _resp . 75 + N _int . 150 = 0

Having received the required area A _tr , according to the assortment we select a column of I-beam profile I55B2 with the following characteristics:

And _f = 124.75 cm ² ;

i _x = 22.43 cm;

i _y = 4.7 cm

and oval section from a pipe ⌀530 mm with the following characteristics

And _f = 115 cm ² ;

i _x = 24.0 cm;

i _y = 7.2 cm

Stability check from the plane: l _x1 = 14.2 m

1. A column with I-beam branches

λ _x <λ _y

σ = 137.85 MPa≤146.28 MPa

Sustainability is provided.

2. A column with oval branches with a ratio of dimensions equal to three

λ _x > λ _y

γ = 0.9

σ = 149.5 MPa≤168.912 MPa

Stability is provided with a margin of 13%.

Specification of a double-branch double-tee column

Section Length mm amount Weight Note units Total Dvutarv 55B2 14200 2 1390.18 2780.36

Oval cross-section two-column specification

Section Length mm amount Weight Note units Total Oval h = 530 mm 14200 2 1282.26 2564.52

Grid calculation

The design grid of the representation of FIG. 11.

l is the length of the brace of the lattice; N _Rask - longitudinal force in the brace.

We select the elements of the lattice of the box section γ = 0.9

For A _Tr = 10.88 cm ^{2 we} take a section □ 10 × 10 × 0.3 cm

And _f = 11.64 cm ² ;

i _x = 3.96 cm

γ = 0.9

σ = 154.786 MPa≤174.294 MPa

Stability secured with margin

Transformation of column branches into pipe-concrete elements

We will increase the stability of the branches of the column by turning them into concrete pipes.

The value of the coefficient of increase in the strength of concrete in the pipe [Belene, p.191]

Table 1 Concrete grade 250 300 350 400 450 500 550 k _bya 1.92 1.83 1.73 1.66 1,59 1.55 1,50 R _PR MPa 10.79 13.24 15,2 17.17 19.13 21.09 R _PR kgf / cm ² 110 135 155 175 195 215

The bearing capacity of pipe-concrete column N≤ (A R _{os os os} + A k _Tr R _y) φ

where A _b and A _Tr - the area of the concrete core and steel pipe;

k _ba - coefficient of increase of concrete strength in the pipe;

R _ba = R _CR and R _y - the design resistance of concrete and steel;

φ is the coefficient of stability of the rod of the concrete column.

Reduced flexibility

;

; ℓ_ef - расчетная длина колонны;Where

;

; ℓ _ef is the estimated column length;

- радиус бетонного ядра.

- radius of the concrete core.

table 2 Stability coefficient φ of the rod of the concrete pipe Reduced flexibility λ _Pr 10 twenty thirty 40 fifty 60 Concrete grade 250 0.988 0.963 0.931 0.888 0.850 0.791 Concrete grade 500 0.988 0.974 0.950 0.922 0.893 0.852 Reduced flexibility λ _Pr 70 80 90 one hundred 110 120 Concrete grade 250 0.728 0.654 0.591 0.527 0.461 0.400 Concrete grade 500 0.80 0.731 0.663 0.588 0.518 0.450

Assign the branches of the column from the oval section of the pipe. The oval rod was obtained from a pipe ⌀ 530 · 7 mm, A = 115 cm ² , i _x = 24.0 cm, i _y = 7.2 cm, m = 90.3 kg.

The vertical and horizontal dimensions of the oval profile (along the axis passing through the middle of the wall thickness)

2b=26,16 см.

2b = 26.16 cm.

Vertical and horizontal profile oval dimensions

2 a + t ₀ = 78.48 + 0.7 = 79.18; 2b + t ₀ = 2 · 13.08 + 0.7 = 26.86 cm.

Moments of inertia

Moments of resistance

Section core radii

radii of inertia

The geometric and calculated length of the column from the plane is ℓ = 1420; ℓ _ef = μ · ℓ = 1420 cm.

The geometric and calculated length of the column in the plane is µ = 1, ℓ = 300; ℓ _ef = μ · ℓ = 300 cm.

Maximum flexibility λ _x = 59.17

We fill the oval profile with fine-grained expanding concrete and turn the core into a concrete pipe.

The external dimensions of the concrete cross section of the core are the largest and smallest 2 a -t ₀ = 78.48-0.7 = 77.78; 2b-t ₀ = 2 · 13.08-0.7 = 25.46 cm.

The cross-sectional area of the concrete core

The moment of inertia of the concrete core

Radius of inertia of concrete core

Reduced flexibility

The bearing capacity of the branch of the concrete pipe

The bearing capacity of the branch of the pipe-concrete column increased in comparison with the steel branch of the column of the I-section in 25596.4 / 18248.43 = 1.4 times.

The bearing capacity of the branch of the pipe-concrete column increased compared to the steel branch of the column oval in section in

25596.4 / 19424.88 = 1.3 times.

The effect is high.

Information sources

1. Reinforced concrete and stone structures: Textbook for construction specialties of universities / V.M. Bondarenko, V. G. Nazarenko, V. I. Rimshin; edited by V.M. Bondarenko - M., Higher. school, 2007, 887 p .; silt.

2. A.P. Kudzis. Reinforced concrete and stone structures: A textbook for construction specialties. - M., Higher. school., 1989 - 264 p.

3. Nezhdanov K.K., Nezhdanov A.K., Borozdin A.Yu. The method of unloading collapsing reinforced concrete consoles. B66C 7/00, E04G 23/02. Application 2006 112731/11, 04.17.2006. Russian patent No. 2346878. Posted 02/20/2009. Bull. No. 5.

4. Nezhdanov K.K., Tumanov V.A., Nezhdanov A.K. A method of reinforcing a reinforced concrete column that has lost its bearing capacity. Russian Patent No. 2274719. M., Cl. E04G 23/02. Application No. 2004116028 dated 2004.02.19. Bull. No. 11. Published on April 20, 2006. Concrete. Prototype.

5. Nezhdanov K.K., Tumanov V.A., Nezhdanov A.K., Karev M.A. Rail and beam construction. Russian Patent No. 2191154. M., Cl. B66C 6/00, 7/08. Bull No. 24. Zareg. 10/20/2002.

6. Nezhdanov K.K., Nezhdanov A.K., Tumanov V.A., Karev M.A. Rail and beam construction. Patent of Russia No. 2192381. M., Cl. B66C 6/00, 7/08. Bull No. 31. Zareg. 11/10/2002. Oval.

7. Nezhdanov K.K., Tumanov V.A., Publishing S.G., Nezhdanov A.K. A method of increasing the bending capacity of a cylindrical pipe. Patent of Russia No. 2304479. Bull. Number 23. Published on August 20, 2007. Oval.

8. Nezhdanov K.K., Nezhdanov A.K., Libarov A.V. "A way to control the stress state of a two-span building frame with foundations with jet engines." Patent of Russia No. 2319811. E02D 35/00 (2006.01). Application for invention No. 2005 116385/03 (018711). Bull. No. 8. Published on March 20, 2008.

9. Nezhdanov K.K., Karev M.A., Nezhdanov A.K., Schipalkin A.A. "The frame of a two-span building." Patent of Russia No. 2 319817. Е04С 3/38 (2006.01). Application for invention No. 2005 116385/03 (018711). Bull. No. 8. Published on March 20, 2008. Concrete.

10. Nezhdanov K.K., Nezhdanov A.K., Kunichkin P.V. A way to eliminate the possibility of collapse of the metal frame structures from fire. Russian patent RU No. 2411330. C1. Application No. 2009117090/03. 05/04/2009. IPC Е04В 1/94 (2006.01). Published 02/10/2011.

Claims (1)

A method of manufacturing pipe-concrete elements of a two-branch steel column containing branches connected by a grating, characterized in that each pipe-concrete element of the column is made of an oval profile with a larger to smaller ratio of three, the expanding concrete is pumped through the concrete pipe and oval rapidly rotating around the longitudinal axis the profile, which is a cage, by centrifugal forces discards (centrifuges) plastic expanding concrete on the periphery to the walls of the cage, by centrifugal forces up they fill and squeeze excess moisture out of it, improve the water-cement ratio, supply steam to the central channel and, without stopping rotation, concrete is steamed from the inside, and when set, the concrete expands, comprehensively bursts the outer cage from the inside, and the cage prevents expansion, comprehensively compresses the concrete from the outside and increases its strength, they complete the rotation, they receive finished pipe-concrete branches, they orient the large dimensions of the ovals perpendicular to the plane of the column, connect the branches with a lattice of box-shaped elements in the section, I equip t the base of the branches with anchor beams connecting the branches, and the ends of the branches with flanges, high-life bolts are connected to the traverse flanges, for example, from an oval profile with a ratio of a larger dimension to a smaller dimension of three, the upper pipe-concrete part of the column is attached to the traverse and get a single structure - a two-branch a pipe-concrete column, and the internal channels are used to increase the fire resistance of the structure, automatically letting cooling water through an alarm signal, limiting the heating of two branches howl pipe-concrete column within tolerable limits.

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