RU2469948C2 - Method for complete unloading of reinforced concrete cantilever of column against action of crane beams - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: for full unloading of a reinforced concrete cantilever of a column against actions of adjacent crane beams that lost its bearing capacity as a result of concrete and reinforcement corrosion, a protective layer of concrete above the column ledge and in the gap between adjacent crane beams and the upper part of the column is removed. A central support beam is installed onto a centraliser, and the beam protrudes with its cantilevers beyond the side faces of the column at one and other sides of the column. An anchor beam is installed at the rear side of the column, central and anchor beams are joined with each other by means of horizontal traction rods with nuts and washers. Side cheeks are installed, and a shell is closed. Short arms of levers are brought under adjacent crane beams, and these arms are joined with crane beams by jack bolts operating for compression, and long arms are brought under anchor beams of the shell, and also joined with jack bolts. At the ends control levers are connected to each other and form a closed control frame. The control frame is installed onto the design elevation. Then jack bolts are adjusted in a mechanised manner.

EFFECT: complete unloading of column cantilevers and provision of crane beams flattening.

2 dwg

Description

The present invention relates to a technological method for restoring the performance of reinforced concrete frame structures of industrial and civil buildings with minimal interference to the main production process.

Analysis of known technical solutions revealed the following. A device for clips and build-up of the cross section and the installation of additional fittings [1, p.255]. There is also a technical solution for strengthening collapsing consoles of reinforced concrete columns, including the installation of a rod system and a steel shoe welded from sheets [2, p. 55, Fig. 25A]. The surface is moistened and covered with shotcrete by concrete. In this case, during the work, the dismantling of the crane beams is necessary. We take well-known devices for analogues. However, most often the reinforced concrete console of the columns, which are affected by the supporting reactions of the crane beams, lose their bearing capacity due to corrosion processes occurring directly in the area under the supports of the crane beams.

The disadvantage of analogues is the need to unload the collapsing consoles of the columns during the work on strengthening and, as a result, stop the turbine workshop for the duration of the repair. No methods were found for the work on strengthening and unloading the consoles of columns without dismantling the beams. Known reinforcement methods require stopping cranes and dismantling adjacent beams before reinforcing work, and it takes two three weeks to set up new reinforced concrete with the required strength.

A known reinforcement method proposed by K. K. Nezhdanov and developed with graduate students [3, patent No. 2346878], allowing quickly and with a sufficient guarantee of strength to ensure complete unloading of collapsing reinforced concrete consoles of columns of industrial buildings. This method is the closest prototype.

The technical task of the invention is the complete unloading of the consoles of columns that have lost their efficiency as a result of corrosion of concrete and reinforcement, without stopping the production process and ensuring the straightening of crane beams.

The technical task of implementing the method of complete unloading, reinforced concrete cantilever columns from the effects of adjacent crane beams, which lost its bearing capacity as a result of corrosion of concrete and reinforcement, was achieved as follows.

The protective layer of concrete above the ledge of the column and in the interval between adjacent crane beams and the upper part of the column is removed, and the surface is washed with water.

In the gap, a centralizer is installed (a support ring from a steel pipe) and filled with fine-grained expanding concrete. The central support beam is mounted on the centralizer, which protrudes with its consoles beyond the side faces of the column on one and the other side of the column, at 1/3 ... 1/2 of its height of its section. The central support beam is mounted square in cross section. Mount the support washers on the central beam and hang from the ends of the central beam of the thrust. Holes are formed in the lower chords of the crane girders at design points for new anchor bolts.

The difference is that the anchor beam is installed on the back of the column, the central and anchor beams are connected to each other by horizontal rods with washers and nuts. Set the side cheeks and close the cage around the upper part of the column, the method of "bottom up" is pumping fine-grained expanding concrete into a circular gap between the cage and the column [4]. At the beginning of concrete setting, tighten the nuts on horizontal rods, additionally compact the concrete in the cage by pressing.

After a set of concrete strengths are suspended on rods to the protruding ends of the central support beam unequal control levers on one and the other side of the column.

Bring the short shoulders of the levers under adjacent crane beams and connect these shoulders to the crane beams with compression bolts, and the long shoulders lead under the anchor beams of the cage and also connect them with jack bolts.

At the ends, the control levers are connected to each other and form a closed control frame. Set the control frame to the project mark. Then the jack bolts are mechanically adjusted, on the short shoulders of the control levers, coordinating the adjustment of the levers with the design value Δ by jacking up the adjacent crane beams.

Unscrew the fixing anchor bolts by this value Δ, and then mechanically adjust the jack bolts on the long shoulders of the control levers. The control levers jack the adjacent crane beams by Δ with jack bolts, abutting them against the anchor beam. The crane beams are returned to their original design position, all the nuts are checked and the modernized crane structures are operated.

The control frame can be assembled around the column at the zero mark, and then lifted by winches to the design mark and suspended on rods to the central beam.

Figure 1 shows the complete discharge of collapsing reinforced concrete consoles;

The bearing capacity of the collapsing reinforced concrete consoles 1 is lost and it must be fully restored! Steel adjacent crane beams 2 are based on the console 1, which collapses from corrosion of concrete and reinforcement.

The supporting reactions of adjacent beams 2, which are subcrane, affect the reinforced concrete console 1 eccentrically.

The method of complete unloading consists in the fact that the protective layer of concrete above the ledge of the column and in the interval between adjacent crane beams 2 and the upper part 3 of the column is removed, and the surface is washed with water.

In the plan, in the interval between adjacent crane beams 2 and the upper part of the column 3, a centralizer 4 (a support ring of a steel pipe) is laid and filled with fine-grained expanding concrete.

Install on the centralizer 4 a central 5 support beam, which protrudes with its consoles beyond the side faces of the column on one and the other side of the column, to 1/3 ... 1/2 of its width. The central 5 support beam is mounted tubular in cross section. Mount the washers on several bolts on the central beam and hang them from the ends of the central beam beam 6 with nuts 7. Form 2 holes in the lower belts of the crane beams at the design points for jack bolts.

Lay on the centralizer 4 a low-modular lining, then on top of it mount the central 5 support beam, protruding beyond the side faces of the column at 1/3 ... 1/2 of its height.

The central 5 support beam is supported through a low-modulus lining, for example, from sheet rubber or oak onto a centralizer 4 near the center of gravity of the column 3.

The central 5 support beam can be made, for example, from an oval profile with a ratio of a larger cross-sectional dimension to a smaller dimension equal to three [5], [6]. Between the central 5 supporting beam and the upper part of the column there is a gap of 80 ... 100 mm along the contour, taking into account the removed protective layer.

An anchor 8 beam, box-shaped in cross section, is installed on the back of the column. Connect the central 5 and anchor 8 beams to each other with horizontal rods 9 with washers and nuts. Install the side cheeks 10 and close the clip around the top of the column. There is a gap of 80 ... 100 mm all over the circuit, taking into account the removed protective layer of concrete.

The method of "bottom to top" is injected with fine-grained expanding concrete into a circular gap between the cage and the column [4]. Initially, the setting of concrete tighten the nuts on the horizontal rods 10, additionally compact the concrete in the cage by pressing.

After a set of concrete strengths are suspended on rods 6 to the protruding ends of the central 5 of the support beam unequal control levers 11 on one or the other side of the column.

Summarize the short 12 shoulders of the levers under adjacent crane beams and connect these shoulders to the crane beams with 13 compression bolts, and the long arms 14 lead under the anchor 8 of the cage beam, and also connect them with 15 jack bolts with washers and nuts.

At the ends, the control levers are connected to each other by rods 16 and form a closed control frame. The control frame is set to the design mark by turning the nuts on the rods 6 with a wrench 6. Then the jack 13 bolts on the short 12 shoulders of the control levers 11 are mechanically adjusted and the lever adjustment is coordinated with the design jacking Δ of adjacent crane beams.

Unscrew the fixing anchor bolts 17 by this value Δ, and then mechanically adjust the jack bolts 15 on the long shoulders of the control levers 11. The levers 11 jack the adjacent crane 2 beams with jack bolts 15 by Δ, abutting with jack bolts in the anchor 8 beam, the crane 2 beams are returned to their original design position. They check all the nuts and operate the modernized crane structures.

The control frame can be assembled around the column at the zero mark, and then completely raised by winches to the design mark and suspended on rods 6 to the central 5 beam.

Loose contact of the mounted cage to the upper part of the column is sealed, for example, by external shotcrete, and this eliminates the leakage of fine-grained expanding concrete when it is pumped into the cage by a concrete pump.

Thus, the modernized console columns are completely unloaded from the supporting reactions of adjacent crane beams. Support reactions are passed around the damaged reinforced concrete console, through the control levers 11 and traction 6 to the central 5 support beam of the cage with minimal eccentricity. Tighten and counter nuts on all rods and operate the modernized crane structures.

The technological sequence of the complete unloading of the console:

- All steel reinforcement elements are pre-mechanized at the steelworks and perform test welding.

- Remove the protective layer of concrete in the area of the cage and wash the surface with water.

- Mount the centralizer.

- Mount the central support and anchor beams and connect them to each other with rods.

- The central and anchor beams are connected to each other by side cheeks of sheets with flanged edges. The flanged edges are bolted on both sides of the column and close the clip.

- Control the design position of the clip. Loose contact of the mounted closed cage to the upper part of the column is sealed, for example, by external shotcrete and this eliminates the leakage of fine-grained expanding concrete through the cracks.

- Mount the concrete pump and control panel, attach the ferrules to the concrete pipes.

- The concrete pump is controlled from the control panel, fine-grained expanding concrete is pumped into the cage by the bottom-up method.

When set, the concrete expands, strains the clip from the inside, compresses the reinforced column from all sides and combines the clip and column into a single whole.

- Next, a steel closed control frame is assembled on bolts at the floor mark, consisting of a pair of unequal control levers 11 oriented perpendicular to the crane beams 2 and having holes for jack bolts 13 and 15. The control frame covers the column from four sides.

- Winches pull up the control frame to the design level, sliding up the column shaft.

- Suspend unequal control levers 11 on the rods 6 to the central beam 5. To facilitate installation, the rods 6 extend outside the section of the control levers 11, and the upper and lower washers for the four bolts are common and cover the cross section of each control lever above and below.

- Combine the holes in the shelves of the crane 2 beams and unequal control levers 11 and attach the unequal control levers with jack bolts 13 and 15 to adjacent crane 2 beams and the anchor beam 8.

- Taking into account the precipitation of the column by Δ, unscrew the nuts on the anchor bolts by Δ.

- Taking into account the precipitation of the column by the value of Δ and subsequent jacking, adjust the jack bolts on the short shoulders 12 of the control levers 11.

- Lastly, the jack bolts on the long shoulders 14 of the control levers 11 are adjusted, jacking the adjacent crane 2 beams by the draft Δ, resting the jack bolts 15 against the anchor beam 8, and restore their original design mark. Anchor beam 8 is an emphasis for jack bolts 15.

- It should be noted that the jack bolts on the long shoulders 14 of the control levers 11 are loaded 2 ... 3 times less, in proportion to the ratio of the short and long shoulders of each of the control levers 11, which facilitates straightening.

- Mechanized by a wrench, guaranteed to tighten the locknuts on rods 6 and jack bolts 13 and 15 and fix the design position of the crane 2 beams.

- Operate the modernized console columns and straightened crane structures.

The support reaction D _max from two adjacent cranes was transmitted to the collapsing console 1 with an eccentricity e and caused a bending moment: M = D _max e.

After the console is completely unloaded, the support reaction D _max is transmitted to the short shoulders 12 of the pair of control levers 11, and then through the link 6 to the central 5 support beam of the cage. The central 5 beam transfers D _max further to centralizer 4 with minimal eccentricity for column 3.

The long shoulders 14 of the pair of control levers 11 are proportional to the ratio of the shoulders of the pair of levers 2 ... 3 times less force trying to lift through the jack bolts 15 jack 8 beam rails, monolithically connected with the body of the column 3 and which is the focus.

Thus, the damaged console 1 is completely unloaded.

The method of complete unloading of reinforced concrete consoles of columns that have lost the bearing capacity has been developed for implementation at TPP-1 in Penza.

An examination of the turbine workshop of the CHPP-1 in Penza revealed dangerous corrosion damage to the reinforced concrete consoles of the columns, on which the split crane beams rest.

An old turbine weighing 100 tons must be dismantled when lifting it with a hitch from two bridge cranes with a lifting capacity of 50 tons and moved to the end of the workshop, and a new turbine weighing 100 tons should be moved to the installation site.

The reinforced concrete consoles of columns damaged by corrosion do not provide sufficient strength. Reinforced concrete consoles could collapse under the influence of supporting reactions of beams and required immediate reinforcement. It is impossible to stop the turbine workshop during the repair. Therefore, a method has been developed for the complete unloading of consoles without stopping the turbine workshop.

We will calculate the designs of the unit for supporting the crane beams using the forces arising in it during the simultaneous operation of two close-coupled cranes operating in the coupling and transporting a turbine weighing 100 tons on one cross beam.

Two adjacent cranes with a lifting capacity of 50 tons are placed unfavorably on adjacent beams. The calculated impact of each wheel is P = 2674.1 gN.

The maximum support reaction D _{max is} determined by the line of influence: D _max = ∑Р _i y _i ; D _max = 3 · 2674.1 (2.18 + 4) / 6 = 8263 gN.

We take the ratio of the shoulders of the control levers is approximately 3/1, that is, the long arm exceeds the short one by three times, then the force transmitted from the bottom to the top is transmitted to the anchor beam, F _Sub. = 8263/3 = 2754.3 gN.

The total force in eight rods 6 will be equal to

∑F = D _max + F _Bcsp. = 8263 + 2754.3 = 11017.3 gN.

The emergency state of the console is eliminated by completely unloading the collapsing console.

A pair of control levers on eight rods of high-strength alloy steel (GOST 4543-71 *) are suspended from the main support beam of the holder of the upper part of the column. Rods, steel 40KhZMF "Select" [7, p. 72, table 61 *] with the least temporary resistance R _bun = 1350 MPa. The calculated resistance after heat treatment [7, p.6] R _bh = 0.7R _bun = 945 MPa.

Eight rods 6 transmit the total force near the center of gravity of the cross section of the column with minimal eccentricity (see figure 2).

∑F = D _max + F _Bc = 8263 + 2754.3 = 11017.3 gN.

The required cross-sectional area of eight rods 6 (alloy steel 40X "Select")

We take eight rods M20 [7, p. 72, tab. 62 *] with a total net cross-sectional area of 2.45 · 8 = 19.6> 14.6 cm ² cut. That is, four rods for the suspension of each control lever. Testing the strength of eight rods 6 tensile

The strength of the eight rods 6 tensile provided with a margin.

Calculation of the central support beam for bending

We take a section of the central support beam box-shaped.

The load per unit of its length

Then the bending moment

The required moment of resistance of the Central support beam

The cross-section of the central support beam is a rectangular pipe of two unequal angles [8, p. 50] 2 G 200 · 125 · 14 mm, A = 2 · 37.9 = 78.8 cm ² , W _x = 422 cm ³ , m = 34.4.2 = 68.8 kg / m. Steel C275 VST3ps6-2, TU 14-1-3023-80, R _y = 260 MPa.

Strength check of the central support beam

The strength of the central support beam of the cage is provided.

The central support beam can be made I-beam in the section of I 300 · 135 mm, A = 46.5 cm ² , W _x = 472 cm ³ [8, p. 52]

Lever Calculation

Short lever arm - 30 cm

Long shoulder of the control lever - 100 cm

Bending moment M = 5000 · 30 = 150,000 gN / cm

The required moment of resistance of the control lever

The cross section of the control lever is a rectangular pipe from two unequal angles [8, p. 50] 2 G 250 · 160 · 16 mm, A = 2 · 63.6 = 127.2 cm ² , W _x = 782.6 cm ³ , m = 49.9.2 = 99.8 kg / m. Steel C255 VST3sp5, GOST 27772-88, R _y = 230 MPa.

Checking the strength of the control lever

A comparison of the developed method with the prototype shows the following significant differences, namely:

1. The reinforced concrete console of the column, which has lost its bearing capacity, is completely unloaded from the supporting reactions of the crane beams and bending moment.

2. The box-shaped cross-section of the central beam of the holder dampens the dynamics of the effects of the wheels of the cranes, which increases the endurance of the attachment point and crane beams.

3. The spatial position of the crane beams is controlled and their design position is restored during operation.

4. The manufacture of structures is simplified.

5. The central beam is clearly fixed on the centralizer installed between adjacent crane beams and the upper part of the column.

6. Support reactions from adjacent crane beams are transmitted through the central beam, supported through a centralizer with minimal eccentricity near the center of gravity of the section of the lower part of the column.

7. The straightening of the crane tracks is mechanized by tightening the nuts on the rods with a wrench.

8. Tightening the nuts with a wrench ensures accurate alignment of elevations of adjacent crane beams with coaxially mounted rails.

9. Jacking the crane beams is easy to re-do. The economic effect was achieved due to the following:

- Increasing the reliability of the nodes supporting the crane beams on the columns.

- An exception to the possibility of collapse of the reinforced concrete consoles of columns that have lost the bearing capacity.

- Ensured restoration of the design position of the crane beams and mechanized straightening of rail tracks during operation.

The method was developed for CHPP-1 in Penza. In this way, the console of the turbine compartment that has lost the bearing capacity in 2011 will be completely unloaded.

Bibliography

1. Kudzis A.P. Reinforced concrete and stone structures. In 2 parts. Part 2. Designs of industrial and civil buildings and structures. - M.: Higher School, 1989, 264 p.

2. Recommendations for assessing the state and strengthening of building structures of industrial buildings and structures. - M .: Stroyizdat, 1989.

3. Nezhdanov K.K., Nezhdanov A.K., Borozdin A.Yu. Russian patent No. 2346878. Posted 02/20/2009. Bull. No. 5. Prototype.

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.

5. 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.

6. Nezhdanov K.K., Tumanov V.A., Publishers 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.

7. SNiP II - 23 - 81 *. Steel structures. - M.: TsITP Gosstroy of the USSR, 1990 - 96 p.

8. Sakhnovsky M.M. Handbook of constructor of welded structures. - Dnepropetrovsk: Promin, 1975.273 s.

Item Numbers

1. reinforced concrete consoles that have lost their bearing capacity

2. adjacent crane beams

3. top of the column

4. centralizer

5. the central beam of the cage

6. traction suspension

7. nuts

8. Anchor beam

9. horizontal traction clips

10. cheeks of a steel holder

11. unequal control levers

12. short lever arm

13. jacking bolts

14. long lever arm

15. jacking bolts

16. traction control levers

Claims (1)

The method of complete unloading of the reinforced concrete cantilever of the column from the effects of crane beams, which lost its bearing capacity as a result of corrosion of concrete and reinforcement, namely, that the protective layer of concrete is removed above the ledge of the column and in the gap between adjacent crane beams and the upper part of the column, and the surface is washed with water, in the interval, establish a support ring (centralizer) from a steel pipe and fill it with fine-grained expanding concrete, install a central support beam on the centralizer, which protrudes they are consoles on one and the other side of the column, characterized in that they install an anchor beam on the back of the column, connect these beams to each other by horizontal rods with washers and nuts, install side cheeks and close the clip around the top of the column, from the bottom up fine-grained expanding concrete is pumped into a circular gap between the holder and the column; at the beginning of concrete setting, tighten the nuts on horizontal rods, additionally compact the concrete by pressing, and then harden the concrete after hardening on the rods to the protruding ends of the central beam, unequal control levers, on both sides of the column, orienting the short shoulders under adjacent crane beams, without tightening, connect these shoulders to the crane beams with jacking bolts working in compression, and their long shoulders are brought under the anchor beam of the cage and they are also connected with jack bolts, the ends of the levers are connected to each other and form a closed control frame, set it to the design position, and then mechanically adjust the jack bolts of short the shoulders of the control levers, coordinating the adjustment with the project jacking by the value Δ of adjacent crane beams, unscrew the mounting anchor bolts by the value Δ, and then mechanically adjust the jack bolts on the long shoulders of the control levers, jack the adjacent crane beams by the value Δ, return them to their original design position , check all the nuts and operate the modernized crane structures.

Images