CN113502921B - Construction method of concrete filled steel tube arch rib - Google Patents

Abstract

When the arch rib is erected, a gap is reserved between arch rib sections on two sides at the arch crown position, and the two sides are rigidly connected through steel members. The end of each rib segment is provided with a pressure applying part. The pressure applying part includes a diaphragm, a cylinder and a piston. After concrete is injected into the arch rib sections on the two sides in a pressure mode, jacks are installed in the gaps, pressure is applied to the piston bodies on the two sides, the concrete pressure in the arch rib sections is increased, and the steel pipe is pulled in the annular direction. After the concrete is finally set, connecting the arch rib sections at the two sides by using the steel pipe sheet at the gap, removing the connecting member, and pressing and injecting the concrete into the gap to complete the forming construction of the arch rib. The method can avoid the void and debonding between the concrete in the arch rib and the steel tube wall, and the added material and cost are low.

Description

A construction method of steel tube concrete arch rib

technical field

The invention relates to the technical field of building construction, in particular to a construction method of a steel pipe concrete arch rib.

Background technique

In recent years, CFST has been widely used in super high-rise buildings and long-span bridges, and its cross-section is mainly circular. Steel pipes and concrete complement each other. On the one hand, the steel pipes are similar to stirrups, which make the concrete three-dimensionally compressed and the compressive capacity is enhanced. On the other hand, the inner filling of concrete solves the potential instability of the steel pipes.

With the increase in the application of concrete filled steel pipes in actual engineering, it is found that there are gaps in many internal concrete and the inner wall of steel pipes. The gaps with large thickness are called voids, and those with small gap thicknesses are generally called debonding. The arch ribs of concrete-filled steel tube arch bridges are exposed in the field, and are poured with pumped concrete. It is generally believed that the interior of the concrete can be compacted if the construction is carried out in accordance with relevant process standards. However, for the concrete-filled steel tube arch bridge constructed by conventional methods, the space between the concrete and the steel tube is unavoidable. The main reason for voiding is the shrinkage of concrete during the process of forming strength, the radial shrinkage of concrete under the action of temperature during use, or the separation of the two caused by the radial expansion of steel pipes. In building structures, it is mainly this interfacial detachment that causes radial debonding. For CFST arch bridges, voiding and debonding mainly occur in the vault section, because the vault section is relatively flat and is the highest part of the entire arch rib. The void directly affects the interaction between the steel pipe and the concrete, and most design codes have not yet considered the effect of the void.

How to avoid voiding of CFST members has attracted attention. The current method mainly uses micro-expansion concrete, slow-expansion concrete, and welding anti-debonding connectors on the inner wall of the steel pipe. Because more anti-debonding connectors will increase the resistance of concrete pumping, it cannot be set too much. At present, the expansion of concrete is mainly used to enhance the tightness of the steel pipe to the concrete, so as to prevent debonding. However, the volume expansion of concrete is limited, and the high temperature makes the expansion of the steel pipe greater. Therefore, the debonding of the concrete and the steel pipe is inevitable.

Contents of the invention

The object of the present invention is to propose a construction method of a steel tube concrete arch rib in order to solve the shortcomings in the prior art.

The technical solution adopted by the invention: make the concrete in the arch rib finally set under the state of external pressure to avoid debonding in the subsequent use process. The specific construction method includes the following steps:

S1: Manufacture of steel pipe sections. Each steel pipe section is manufactured; a diaphragm is welded at the end of the steel pipe section at the top of the arch rib, and the middle part of the diaphragm is connected to a cylindrical cylinder. The outer end of the cylinder is temporarily fixed with a piston body. The loading side faces outward;

S2: Install steel pipe sections to hoist each steel pipe section of the arch rib, leave a gap on the vault, the two sides of the gap are the top steel pipe sections made in the previous step, and the diaphragm is close to the gap; adjust the elevation of each steel pipe section to meet the design requirements , to weld the adjacent steel pipe sections; the top steel pipe sections on both sides of the vault gap are welded to connect the steel members;

S3: Injection of concrete: Inject concrete into the arch ribs on both sides of the vault to ensure that the injection is full and there is no trapped air between the upper surface of the concrete and the steel pipe;

S4: Apply pressure to hang in the gap and install the booster device, remove the temporary fixing measures between the cylinder body and the piston body, and the booster device applies thrust to the piston body at both ends; strain gauges are installed on the outer surface of the steel pipe near the vault , monitor the hoop stress of the steel pipe, and control the jacking force with the set hoop stress limit; maintain the jacking force before the concrete reaches the set strength;

S5: Complete the concrete pouring of the gap section and remove the booster equipment, connect the arch rib sections on both sides of the gap with steel pipe pieces, and connect the steel pipe pieces together to form the gap steel pipe section connecting the arch rib sections on both sides; Concrete injection: After the newly injected concrete has finally set and reached the set strength, the connecting steel members that originally spanned the gap are removed.

Preferably, the concrete is micro-expansion self-compacting concrete with a strength grade of at least C60.

Preferably, the composition of the piston body includes an end plate, a side plate, and a stiffened rectangular plate of the end plate; the side plate is cylindrical and has a smooth outer surface.

Preferably, the cylinder body is cylindrical with a smooth inner surface.

Preferably, at the end of the side plate of the piston body away from the end plate, there is a sealing groove along the circumference on the outer surface, and a sealing ring is placed in the sealing groove.

Preferably, the width of the gap and the distance between the end plates of the two temporarily fixed piston bodies are both greater than the initial length of the force-applying device.

Preferably, the force adding device is a hydraulic jack.

Preferably, there is a sealed diaphragm in the middle of the arch rib section, which divides the arch rib section into a plurality of injection chambers; in step S3, the corresponding injection chambers on both sides are injected sequentially from low to high;

Preferably, when the injection chamber is close to the bridge deck, the injection port is set at the upper end of the injection chamber, and the concrete enters the injection chamber from the high end of the injection chamber.

Preferably, the transverse middle part of the steel pipe sheet is close to the connecting steel member, so as to prevent the connecting steel member from affecting the welding operation of adjacent steel pipe sheets.

The beneficial effects of the present invention are: by applying external pressure to the concrete that has just been poured in the steel pipe, the concrete is made denser; both the external pressure and the micro-expansion of the concrete cause the diameter of the steel pipe to expand, and after the final setting of the concrete, the steel pipe tightly The hoop is on the inner concrete column, which enhances the bonding force between the two and can avoid debonding; the external force in this invention is applied at the position of the vault, considering that the newly poured concrete is different from the conventional ones such as water and hydraulic oil. The transmission of pressure is affected by factors such as the viscous resistance between the concrete and the steel pipe wall, and the effect of the pressure gradually decreases toward the bottom of the arch rib, and the effective range is mainly at the top of the arch, which is where voiding and debonding are prone to occur. Therefore, in the present invention, the boosting device is arranged on the top, and the method is efficient; the material adopted in this scheme is section steel, and the equipment adopted are all commonly used equipment on the construction site, and the increased operations are only the operation of welding and hydraulic jacks. Therefore, less material is used, the operation is simple, and only a small increase in cost is required.

Description of drawings

Fig. 1 is the arch rib longitudinal sectional schematic view during the arch rib concrete is applied to the arch rib concrete in embodiment 1;

The sectional schematic diagram of A-A in Fig. 2 Fig. 1;

Figure 3 is a schematic side view of the arch rib before connection;

Fig. 4 Fig. 3 crosses the schematic sectional view of B-B;

Figure 5 is a schematic diagram of an axial cross-section of a defect body being produced;

Figure 6 is a schematic side view of the connecting steel beams between the arch rib sections;

Fig. 7 is a schematic diagram of longitudinal section of arch rib after connection;

Figure 8 is a schematic diagram of the longitudinal section of the two arch ribs after injection of concrete;

Figure 9 is a schematic diagram of the initial connection between the cylinder body and the piston body;

Fig. 10 is a schematic diagram of the longitudinal section after the steel pipe section is welded between the two arch rib sections;

Figure 11 is a schematic diagram of the longitudinal section after the arch rib is formed;

Fig. 12 Schematic diagram of assembling the steel sheets of the gap steel pipe section.

In the figure: 1-steel pipe, 2-concrete, 3-first-stage exhaust pipe, 4-T-shaped steel beam, 5-jack, 6-stiffened triangular plate, 7-diaphragm, 8-cylinder, 9-piston body, 10-notch, 11-column, 12-beam, 13-stiffened rectangular plate, 14-end plate, 15-side plate, 16-screw, 17-sealing ring, 18-second stage exhaust pipe, 19- The second stage feed pipe, 20-upper steel pipe piece, 21-lower steel pipe piece, 22-replenishing grout hole.

Detailed ways

Example 1

This embodiment takes the forming of an arch rib in a concrete-filled steel tube arch bridge as an example. The outer diameter of the steel pipe of the arch rib is 1200mm, and the wall thickness is 20mm. In order to improve the anti-bonding ability between the formed steel pipe and the internal concrete, the construction scheme in the present invention is adopted. The construction method of the steel pipe concrete arch rib comprises the following steps:

S1: Manufacture of steel pipe section With the vault as the boundary, there is an arch rib section on both sides, and the two arch rib sections are symmetrical relative to the mid-span position. Each arch rib segment is composed of several steel pipe segments. Make each steel pipe segment. The diaphragm 7 is welded at the end of the steel pipe section at the top of the arch rib, and the middle part of the diaphragm 7 is connected to a cylindrical cylinder 8, and the outer end of the cylinder 8 is temporarily fixed with a piston body 9, see Fig. 1, Fig. 5 and Fig. 9. A stiffening triangular plate 6 is added to the connection between the diaphragm 7 and the steel pipe 1, as shown in FIG. 4 . The temporary fixation measures include 16 screw rods 16 with a diameter of 20mm evenly distributed along the circumference, and the screw rods 16 enter the non-through screw holes on the side plate 15 after passing through the through holes on the cylinder body 8 . The composition of the piston body 9 includes an end plate 14, a side plate 15, and a stiffened rectangular plate 13; the side plate 15 is cylindrical and has a smooth outer surface. The cylinder block 8 is cylindrical, with an inner diameter of 600 mm and a smooth inner surface. The end of the side plate 15 of the piston body 9 away from the end plate 14 has a sealing groove along the circumference on the outer surface, and a sealing ring 17 is placed in the sealing groove. The grout filling hole 22 is arranged on the diaphragm 7, and a one-way valve is installed inside, which can only flow in and not flow out.

S2: Install steel pipe sections Lift and install the steel pipe sections of the arch rib, see Figure 3. Leave a gap in the vault, the top steel pipe sections made in the previous step are on both sides of the gap, and the diaphragm 7 is close to the gap; the width of the gap is 800mm, and the outer surface of the end plate 14 is 100mm from the gap. Adjust the elevation of each steel pipe section to meet the design requirements, weld adjacent steel pipe sections; weld T-shaped steel beams 4 as connecting steel members for the top steel pipe sections on both sides of the vault gap. Five T-shaped steel beams 4 are evenly arranged along the circumference of the gap, as shown in FIG. 2 . T-shaped steel girder 4 adopts conventional T-shaped steel, T-shaped steel height 294mm wide 300mm web thickness 12mm, wing plate thickness 20mm; Add welding one and the same width of flange on the T-shaped steel flange, the steel plate that thickness is 18mm ensures that all The sum of the cross-sectional areas of the T-shaped steel beams 4 is greater than the cross-sectional area of the steel pipes 1 . The schematic side view of the T-shaped steel beam 4 between the arch ribs is shown in Figure 6. In order to facilitate subsequent construction, there is a gap 10 with a length of 1000mm in the middle of the T-shaped steel beam 4, and the depth of the gap 10 is 40mm. At this stage, a hanger consisting of uprights 11 and beams 12 is installed, see FIG. 7 .

S3: injection concrete The concrete 2 is micro-expansion self-compacting concrete with a strength grade of C60. The arch rib section on each side is a pressure injection chamber, and there are multiple first-stage exhaust pipes 3 . There are multiple feed ports, the lowest feed port being located at the middle of the rib height. Simultaneously press-inject concrete 2 into the two arch rib sections from low to high on both sides; when injecting at the lowest feed port, at the beginning stage, concrete 2 flows from the high end to the low end relying on its own gravity; during subsequent injection, Less pressure is required than direct injection from the deck end. During the pressure injection process, from low to high, timely close the first-stage exhaust pipe of the slurry outlet 3. Complete the pumping construction of the concrete 2 of the two arch rib sections. The longitudinal section diagram of the two arch rib sections after injection of concrete is shown in Figure 8. The interior of the arch rib section has been fully injected, and there is no trapped air between the upper surface of the concrete 2 and the steel pipe 1.

S4: Apply pressure After the pumping construction of concrete 2 is completed, immediately hang and install the jack 5 in the gap of the vault, and adjust the position of the jack 5 with a manual hoist. After the top extension rod is fully retracted, the initial length of the jack 5 is 700mm, the outer diameter is 600mm, and the inner diameter is 400mm. Remove the screw rod 16 between the temporarily fixed cylinder body 8 and the piston body 9. The jack 5 exerts push force on the piston body 9 at both ends; a strain gauge is installed on the outer surface of the steel pipe 1 at the top of the arch rib section to monitor the hoop stress of the steel pipe 1 . The set hoop stress limit is 150MPa to control the jacking; before the concrete 2 reaches 80% of the design strength, the jacking force is maintained.

For the concrete 2 near the vault, the transmission of pressure can be analyzed approximately according to the method in conventional liquids, so as to estimate the required jacking force. According to the size of the inner diameter of the cylinder body 8 and the inner diameter of the jack 5, a pressure increase of 1 MPa is generated in the concrete 2, at least corresponding to an oil pressure increase of 2.25 MPa in the oil pressure of the jack 5; The pressure increment corresponds to the stress increment of 29MPa in the steel pipe 1 hoop direction. Therefore, if it is set to cause a stress increment of 150MPa in the steel pipe 1 at the top of the arch rib section, the corresponding pressure increment in the concrete is greater than 5MPa, and the oil pressure increment in the jack 5 is about 11.3MPa, corresponding to the top of the jack 5. The thrust is 165tonf. Therefore, when selecting the jack 5, you can choose the one with a rated jacking force of 250 tonf or 300 tonf. During the application of force, the strain gauge on the steel pipe 1 is observed to monitor the hoop stress of the steel pipe 1 near the vault. If before the hoop stress reaches the limit value, the stroke of the jack 5 will reach the maximum value, the grout of the concrete 2 without coarse aggregate can be injected into the arch rib section through the grouting hole 22, and at the same time, the jack 5 returns; 5. After the return stroke finishes, stop the pressure injection by grouting hole 22, continue to start operating jack 5, make it elongate. This cycle continues until the hoop stress reaches the limit.

S5: Complete the concrete pouring of the gap section and remove the jack 5, use the upper steel pipe piece 20 and the lower steel pipe piece 21 to connect the arch rib sections on both sides of the gap, and weld the two steel pipe pieces to form a gap steel pipe connecting the arch rib sections on both sides section, see Figure 10 and Figure 12; the bottom and top of the gap steel pipe section are respectively provided with a second-stage feed pipe 19 and a second-stage exhaust pipe 18. An electric blanket is wrapped on the gap steel pipe section to heat the steel pipe section to promote the expansion of the steel pipe. Press-inject concrete 2 into the steel pipe section in the gap; after the newly injected concrete 2 finally sets and reaches the set strength, remove the electric blanket; remove the T-shaped steel beam 4 that spans the gap, and the hanger, etc., and correct the surface of the arch rib , the schematic diagram of the longitudinal section after the arch rib is formed is shown in Figure 11.

So far, according to the solution of the present invention, the molding construction of the arch rib has been completed.

Claims (7)

1. a construction method of concrete-filled steel tube arch rib, is characterized in that: concrete is micro-expansion self-compacting concrete, makes the concrete in the arch rib final set forming under the state of being subjected to external pressure, avoids falling off in subsequent use process Sticky, the specific construction method includes the following steps: S1: Manufacture of steel pipe sections. Each steel pipe section is manufactured; a diaphragm is welded at the end of the steel pipe section at the top of the arch rib, and the middle part of the diaphragm is connected to a cylindrical cylinder. The outer end of the cylinder is temporarily fixed with a piston body. The loading side of the piston body faces outward; the composition of the piston body includes an end plate, a side plate, and a stiffened rectangular plate of the end plate; the side plate is cylindrical, and the outer surface is smooth; the cylinder body is cylindrical, and the inner surface is smooth; The end of the side plate of the piston body away from the end plate has a sealing groove along the circumference on the outer surface, and a sealing ring is placed in the sealing groove; S2: Install steel pipe sections to hoist each steel pipe section of the arch rib, leave a gap on the vault, the two sides of the gap are the top steel pipe sections made in the previous step, and the diaphragm is close to the gap; adjust the elevation of each steel pipe section to meet the design requirements , to weld the adjacent steel pipe sections; the top steel pipe sections on both sides of the vault gap are welded to connect the steel members; S3: Injection of concrete: Inject concrete into the arch rib sections on both sides of the vault, and use multiple first-stage exhaust pipes on the arch rib sections to ensure that the injection is full and there is no trapped air between the upper surface of the concrete and the steel pipe; S4: Apply pressure to hang in the gap and install the booster device, remove the temporary fixing measures between the cylinder body and the piston body, and the booster device applies thrust to the piston body at both ends; strain gauges are installed on the outer surface of the steel pipe near the vault , monitor the hoop stress of the steel pipe, and control the jacking with the set hoop stress limit value; if the jack stroke will reach the maximum value before the hoop stress reaches the limit value, the jack can pass through the grouting hole on the diaphragm Press-inject the concrete slurry without coarse aggregate into the arch rib section, and at the same time, the jack returns; after the jack returns, stop the pressure injection through the grout filling hole, and continue to operate the jack to make it elongate; so cycle until The hoop stress reaches the limit; before the concrete reaches the set strength, maintain this jacking force; S5: Complete the concrete pouring of the gap section and remove the booster equipment, connect the arch rib sections on both sides of the gap with steel pipe pieces, and connect the steel pipe pieces together to form the gap steel pipe section connecting the arch rib sections on both sides; Concrete injection: After the newly injected concrete has finally set and reached the set strength, the connecting steel members that originally spanned the gap are removed. 2. The construction method of a concrete-filled steel tube arch rib according to claim 1, characterized in that: the strength grade of the slightly expanded self-compacting concrete is at least C60. 3. The construction method of a kind of concrete-filled steel tube arch rib according to claim 1, characterized in that: the width of the gap and the distance between the end plates of the two temporarily fixed piston bodies are all greater than the initial length. 4. The construction method of a concrete-filled steel tube arch rib according to claim 1, characterized in that: the adding force device is a hydraulic jack. 5. the construction method of a kind of concrete-filled steel pipe arch rib according to claim 1 is characterized in that: the middle part of described arch rib section has a sealed diaphragm, and arch rib section is divided into a plurality of injection chambers; In step S3, press the injection chambers corresponding to both sides sequentially from low to high; 6. The construction method of a kind of concrete-filled steel tube arch rib according to claim 5, characterized in that: when injecting the injection chamber close to the bridge deck, the injection port is arranged at the upper end of the injection chamber, and the concrete is pressed from the injection chamber. The high end of the betting bin enters the pressure betting bin. 7. The construction method of a concrete-filled steel tube arch rib according to claim 1, wherein the transverse middle part of the steel tube sheet is close to the connecting steel member, thereby preventing the connecting steel member from affecting the welding operation of the adjacent steel pipe sheet.

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