CN113502921A

CN113502921A - Construction method of concrete filled steel tube arch rib

Info

Publication number: CN113502921A
Application number: CN202110813735.6A
Authority: CN
Inventors: 崔镇江; 魏建东; 王俊林
Original assignee: Zhengzhou University
Current assignee: Zhengzhou University
Priority date: 2021-07-19
Filing date: 2021-07-19
Publication date: 2021-10-15
Anticipated expiration: 2041-07-19
Also published as: CN113502921B

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, a jack is installed in the gap, pressure is applied to the piston bodies on the two sides, concrete pressure in the arch rib sections is increased, and the steel pipe is pulled in the annular direction. And after the concrete is finally set, connecting the arch rib sections at the two sides by using a steel pipe sheet at the gap, removing the connecting member, and injecting the concrete into the gap to finish 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

Construction method of concrete filled steel tube arch rib

Technical Field

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

Background

In recent years, the steel tube concrete is widely applied to super high-rise buildings and large-span bridges, and the section of the steel tube concrete is mainly circular. The steel pipe and the concrete supplement each other, on one hand, the steel pipe is similar to a stirrup, so that the concrete is compressed in three directions, and the pressure resistance is enhanced, and on the other hand, the concrete is filled in the steel pipe to solve the potential instability problem of the steel pipe.

With the increase of concrete filled steel tube application in practical engineering, a plurality of internal concrete and steel tube inner walls have gaps, the gap with large thickness is called void, and the gap with small thickness is generally called debonding. The arch rib of the concrete-filled steel tube arch bridge is exposed in the field, and is poured by pumping concrete, and generally, the concrete can be compacted in the interior when the construction is carried out according to relevant process standards. However, the steel pipe concrete arch bridge constructed by the conventional method cannot avoid the gap between the concrete and the steel pipe. The main reasons for the void are the dry shrinkage of the concrete in the process of forming the strength, the radial shrinkage of the concrete under the action of temperature in the using process, or the separation of the concrete and the steel pipe caused by the radial expansion of the steel pipe and the like. In building structures, it is primarily this interfacial debonding that results in radial debonding. In concrete filled steel tube arch bridges, the de-voiding and de-bonding occurs primarily in the crown section, because the crown section is relatively flat and is the highest point of the overall rib. The void directly affects the combined action of the steel pipe and the concrete, and the influence of the void is not considered in most design specifications at present.

Attention has been paid to avoiding the void of concrete filled steel tube members. The existing method mainly adopts micro-expansion concrete, slow expansion concrete, a connecting piece which is welded on the inner wall of the steel pipe and is prevented from being debonded, and the like. Because of more anti-drop adhesion connectors, the resistance of concrete pumping can be increased, and the arrangement cannot be excessive. At present, the hoop force of the steel pipe to the concrete is enhanced mainly by the expansion of the concrete, so that the debonding is prevented. However, the volume expansion of concrete is limited, and the expansion of steel pipes is increased by high temperature, so that the debonding of concrete and steel pipes is inevitable.

Disclosure of Invention

The invention aims to solve the defects in the prior art and provides a construction method of a concrete filled steel tube arch rib.

The technical scheme adopted by the invention is as follows: the concrete in the arch rib is finally set and formed under the condition of external pressure, so that the concrete is prevented from being debonded in the subsequent use process, and the concrete construction method comprises the following steps:

s1: manufacturing steel pipe sections and manufacturing each steel pipe section; welding a diaphragm plate at the end part of a steel pipe section at the top of the arch rib, connecting the middle part of the diaphragm plate with a cylindrical cylinder body, temporarily fixing a piston body at the outer end of the cylinder body, and enabling the loading surface of the piston body to face outwards;

s2: installing steel pipe sections of the steel pipe section hoisting arch rib, reserving a gap at the arch crown, wherein the top steel pipe section manufactured in the previous step is arranged at two sides of the gap, and the diaphragm plate is close to the gap; adjusting the elevation of each steel pipe section, and welding adjacent steel pipe sections after the design requirements are met; the top steel pipe sections on two sides of the vault gap are welded with steel members;

s3: the pressure injection concrete is pressure-injected into the arch rib sections at two sides of the arch crown, so that the pressure injection is full, and no air is retained between the upper surface of the concrete and the steel pipe;

s4: applying pressure to hoist and mount a force application device in the gap, removing the temporary fixing measure between the cylinder body and the piston body, and applying jacking force to the piston bodies at two ends by the force application device; the outer surface of the steel pipe close to the vault is provided with a strain gauge, the hoop stress of the steel pipe is monitored, and the pushing is controlled according to a set hoop stress limit value; before the concrete reaches the set strength, the jacking force is maintained;

s5: the concrete pouring removal stressing equipment for completing the gap section is characterized in that steel pipe pieces are used for connecting the arch rib sections on two sides of the gap, and the steel pipe pieces are connected together to form the gap steel pipe section for connecting the arch rib sections on two sides; pressing and injecting concrete into the gap steel pipe section; and after the newly-injected concrete is finally set and reaches the set strength, removing the original connecting steel member spanning the gap.

Preferably, the concrete is a micro-expansive, self-compacting concrete having a strength rating of at least C60.

Preferably, the piston body comprises an end plate, a side plate and a stiffening rectangular plate of the end plate; the side plate is cylindrical, and the outer surface of the side plate is smooth and clean.

Preferably, the cylinder is cylindrical and has a smooth inner surface.

Preferably, the end part of the side plate of the piston body, which is far away from the end plate, is provided with a sealing groove along the circumference, and a sealing ring is arranged in the sealing groove.

Preferably, the width of the gap, the distance between the end plates of the two temporarily fixed piston bodies, is greater than the initial length of the force means.

Preferably, the force application device is a hydraulic jack.

Preferably, the middle part of the arch rib section is provided with a sealed diaphragm plate which divides the arch rib section into a plurality of pressure injection bins; in step S3, the injection bins on both sides are sequentially injected from low to high;

preferably, when the pressure injection bin close to the bridge floor is in pressure injection, the pressure injection port is arranged at the upper end of the pressure injection bin, and the concrete enters the pressure injection bin from the high end of the pressure injection bin.

Preferably, the transverse middle part of the steel pipe sheet is close to the connecting steel member, so that the connecting steel member is prevented from influencing the welding operation of the adjacent steel pipe sheet.

The invention has the beneficial effects that: the concrete is more compact by applying external pressure to the concrete just injected into the steel pipe; the diameter of the steel pipe is expanded by external pressure and micro-expansion of the concrete, and after the concrete is finally set, the steel pipe is tightly hooped on the concrete column inside, so that the bonding force between the steel pipe and the concrete column is enhanced, and debonding can be avoided; the external acting force is applied to the arch crown position, considering that newly poured concrete is different from conventional liquids such as water, hydraulic oil and the like, the transmission of the pressure is influenced by factors such as viscous resistance between the concrete and the steel pipe wall, the pressure is gradually reduced towards the bottom of the arch rib, the effective range is mainly in the arch crown section, and the effective range is the position which is easy to be subjected to hollowing and debonding, so that the method has high efficiency by arranging the force applying device at the top; the material that adopts in this scheme is shaped steel, and the equipment of adoption is building site equipment commonly used, and the operation of increase is only welding and hydraulic jack's operation, consequently, uses the material few, easy operation, only increases few cost.

Drawings

FIG. 1 is a schematic longitudinal sectional view of a dome rib during the application of a jacking force to a rib concrete in example 1;

FIG. 2 is a schematic cross-sectional view A-A of FIG. 1;

FIG. 3 is a schematic side view of a rib prior to connection;

FIG. 4 is a schematic cross-sectional view taken through B-B in FIG. 3;

FIG. 5 is an axial cross-sectional view of a defect body under fabrication;

FIG. 6 is a schematic side view of a connecting beam between arch rib segments;

FIG. 7 is a schematic longitudinal cross-sectional view of the joined ribs;

FIG. 8 is a schematic longitudinal cross-sectional view of two rib sections after the concrete is injected;

FIG. 9 is a schematic view of the initial connection between the cylinder and the piston body;

FIG. 10 is a schematic longitudinal cross-sectional view of a section of steel tubing welded between two rib segments;

FIG. 11 is a schematic longitudinal cross-sectional view of the rib after it has been formed;

FIG. 12 is a schematic diagram of assembling steel plates of the gap steel pipe section.

In the figure: the method comprises the following steps of 1-steel pipe, 2-concrete, 3-first-stage exhaust pipe, 4-T-shaped steel beam, 5-jack, 6-stiffening triangular plate, 7-diaphragm plate, 8-cylinder body, 9-piston body, 10-notch, 11-upright post, 12-cross beam, 13-stiffening rectangular plate, 14-end plate, 15-side plate, 16-screw rod, 17-sealing ring, 18-second-stage exhaust pipe, 19-second-stage feed pipe, 20-upper steel pipe piece, 21-lower steel pipe piece and 22-grout filling hole.

Detailed Description

Example 1

This embodiment takes the molding of one 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 20 mm. In order to improve the anti-debonding capacity between the formed steel pipe and the internal concrete, the construction scheme provided by the invention is adopted. The construction method of the concrete-filled steel tube arch rib comprises the following steps:

s1: the steel pipe section is manufactured by taking a vault as a boundary, two sides of the steel pipe section are respectively provided with an arch rib section, and the two arch rib sections are symmetrical relative to a midspan position. Each rib segment is composed of a plurality of steel tube segments. And manufacturing each steel pipe section. A diaphragm 7 is welded at the end part of a steel pipe section at the top of the arch rib, a cylindrical cylinder body 8 is connected to the middle part of the diaphragm 7, and a piston body 9 is temporarily fixed at the outer end of the cylinder body 8, as shown in fig. 1, 5 and 9. A stiffening triangle 6 is added at the joint of the diaphragm 7 and the steel pipe 1, as shown in figure 4. The temporary fixing measures comprise 16 screws 16 with the diameter of 20mm which are uniformly distributed along the circumference, and the screws 16 pass through the through holes on the cylinder body 8 and then enter the non-through screw holes on the side plates 15. The piston body 9 comprises an end plate 14, a side plate 15 and a stiffening rectangular plate 13; the side plate 15 is cylindrical and has a smooth outer surface. The cylinder body 8 is cylindrical, the inner diameter is 600mm, and the inner surface is smooth. The end of the side plate 15 of the piston body 9, which is far away from the end plate 14, is provided with a sealing groove along the circumference, and a sealing ring 17 is arranged in the sealing groove. The diaphragm plate 7 is provided with a grout supplementing hole 22, and a one-way valve is arranged in the diaphragm plate, so that the grout can only flow in but cannot flow out.

S2: the installation of the steel pipe sections hoists the individual steel pipe sections of the arch rib, see fig. 3. A gap is reserved at the vault, the top steel pipe section manufactured in the previous step is arranged at two sides of the gap, and the diaphragm plate 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. Adjusting the elevation of each steel pipe section, and welding adjacent steel pipe sections after the design requirements are met; and (4) welding the T-shaped steel beams 4 as connecting steel members for the top steel pipe sections on two sides of the arch crown gap. 5T-shaped steel beams 4 are uniformly arranged along one circle of the gap, as shown in figure 2. The T-shaped steel beam 4 is made of conventional T-shaped steel, the height of the T-shaped steel is 294mm, the width of the T-shaped steel is 300mm, the web thickness is 12mm, and the wing plate thickness is 20 mm; and a steel plate which has the same width as the flange and has the thickness of 18mm is additionally welded on the flange of the T-shaped steel, so that the sum of the cross-sectional areas of all the T-shaped steel beams 4 is ensured to be larger than the cross-sectional area of the steel pipe 1. A schematic side view of a T-shaped steel beam 4 between arch rib sections is shown in FIG. 6. in order to facilitate subsequent construction, a notch 10 with the length of 1000mm is arranged in the middle of the T-shaped steel beam 4, and the depth of the notch 10 is 40 mm. At this stage, a spreader consisting of uprights 11 and cross-beams 12 is installed, see fig. 7.

S3: and (3) pressure-casting the concrete 2 is micro-expansive self-compacting concrete with the strength grade of C60. The rib section on each side is an injection molding bin which is provided with a plurality of first-stage exhaust pipes 3. There are a plurality of feed inlets, and the feed inlet of lowest department is located the middle part of rib height. The two sides of the arch rib section are synchronously injected with concrete 2 from low to high; when the lowest feed port is injected, the concrete 2 flows into the lower end from the high end by the self gravity at the beginning stage; and during subsequent pressure injection, the pressure is lower than the pressure required by directly injecting from the bridge deck end. And in the process of pressure casting, the exhaust pipe 3 at the first stage of slurry discharge is closed from low to high in time, the pumping construction of the concrete 2 of the two arch rib sections is completed, and the longitudinal section schematic diagram of the two arch rib sections after the concrete is pressure cast is shown in figure 8. The rib sections are fully injected, and no air is retained between the upper surface of the concrete 2 and the steel pipe 1.

S4: after pumping construction of the pressure concrete 2 is completed, a jack 5 is immediately hung and installed in the gap of the vault, and the position of the jack 5 is adjusted by adopting a manual hoist. After the jacking rod is completely retracted, the initial length of the jack 5 is 700mm, the outer diameter is 600mm, and the inner diameter is 400 mm. The screw 16 temporarily fixing the cylinder 8 and the piston body 9 is removed. The jack 5 applies jacking force to the piston bodies 9 at the two ends; and a strain gauge is arranged on the outer surface of the steel pipe 1 at the arch top end of the arch rib section, and the circumferential stress of the steel pipe 1 is monitored. Setting a circumferential stress limit value of 150MPa so as to control pushing; the jacking force is maintained until the concrete 2 reaches the design strength of 80%.

The concrete 2 near the crown can be analyzed for pressure transfer approximately as in conventional liquids to estimate the required jack thrust. According to the size of the inner diameter of the cylinder 8 and the inner diameter of the jack 5, 1MPa of pressure increment is generated in the concrete 2, and the pressure increment at least corresponds to 2.25MPa of oil pressure increment in the jack 5; considering the size of the steel pipe 1, the pressure increment of 1MPa in the concrete corresponds to the stress increment of 29MPa in the circumferential direction of the steel pipe 1. Therefore, if the stress increase of 150MPa is set to be generated in the steel tube 1 at the top end of the arch rib segment, the pressure increase in the concrete is larger than 5MPa, the hydraulic pressure increase in the jack 5 is about 11.3MPa, and the jacking force of the jack 5 is 165 tonf. Thus, when the jack 5 is selected, a rated jacking force of 250tonf or 300tonf can be selected. During the application of force, the strain gauges on the steel pipe 1 are observed to monitor the hoop stress of the steel pipe 1 near the arch crown. If the stroke of the jack 5 reaches the maximum value before the circumferential stress reaches the limit value, grouting the grout of the concrete 2 without coarse aggregate into the arch rib section through the grout supplementing hole 22, and simultaneously returning the jack 5; after the return stroke of the jack 5 is finished, the pressure injection through the grout hole 22 is stopped, and the operation of the jack 5 is continued to extend the jack. And the steps are repeated until the hoop stress reaches a limit value.

S5: completing the concrete pouring and removing jack 5 of the gap section, connecting the arch rib sections at two sides of the gap by using an upper steel pipe sheet 20 and a lower steel pipe sheet 21, and welding the two steel pipe sheets to form the gap steel pipe section for connecting the arch rib sections at two sides, as shown in fig. 10 and 12; the bottom and top of the gap steel pipe section are provided with a second stage feed pipe 19 and a second stage vent pipe 18, respectively. The gap steel pipe section is wrapped with an electric blanket to heat the section of steel pipe and promote the expansion of the steel pipe. Pressing and injecting concrete 2 into the gap steel pipe section; after the newly injected concrete 2 is finally set and reaches the set strength, the electric blanket is removed; the original T-shaped steel beam 4 crossing the gap and the hanger are removed, the surface of the arch rib is corrected, and the longitudinal section schematic diagram after the arch rib is formed is shown in figure 11.

Thus, according to the scheme of the invention, the forming construction of the arch rib is completed.

Claims

1. A construction method of a concrete filled steel tube arch rib is characterized in that: the concrete in the arch rib is finally set and formed under the condition of external pressure, so that the concrete is prevented from being debonded in the subsequent use process, and the concrete construction method comprises the following steps:

2. A method of constructing a concrete filled steel tube arch rib according to claim 1, wherein: the concrete is a micro-expansive self-compacting concrete with a strength rating of at least C60.

3. A method of constructing a concrete filled steel tube arch rib according to claim 1, wherein: the piston body comprises end plates, side plates and stiffening rectangular plates of the end plates; the side plate is cylindrical, and the outer surface of the side plate is smooth and clean.

4. A method of constructing a concrete filled steel tube arch rib according to claim 1, wherein: the cylinder body is cylindrical, and the inner surface is smooth and clean.

5. A construction method of a concrete filled steel tube arch rib according to claim 3 and claim 4, wherein: the end part of the side plate of the piston body, which is far away from the end plate, is provided with a sealing groove along the circumference on the outer side surface, and a sealing ring is arranged in the sealing groove.

6. A method of constructing a concrete filled steel tube arch rib according to claim 1, wherein: 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 application device.

7. A method of constructing a concrete filled steel tube arch rib according to claim 1, wherein: the force application equipment is a hydraulic jack.

8. A method of constructing a concrete filled steel tube arch rib according to claim 1, wherein: the middle part of the arch rib section is provided with a sealed diaphragm plate which divides the arch rib section into a plurality of pressure injection bins; in step S3, the injection bins on both sides are sequentially injected from low to high;

9. a construction method of a steel pipe concrete arch rib according to claim 8, wherein: when the pressure injection bin close to the bridge floor is subjected to pressure injection, the pressure injection port is formed in the upper end of the pressure injection bin, and concrete enters the pressure injection bin from the high end of the pressure injection bin.

10. A method of constructing a concrete filled steel tube arch rib according to claim 1, wherein: the transverse middle part of the steel pipe sheet is close to the connecting steel member, so that the connecting steel member is prevented from influencing the welding operation of the adjacent steel pipe sheet.