Construction method based on pushing support

Abstract

The invention relates to the technical field of construction based on a pushing support, in particular to a construction method based on a pushing support, which comprises the following steps: designing a pushing support structure, and installing a slideway at the top end of the pushing support after welding is completed; reinforcing steel bar machining and binding are conducted on the formwork according to the drawing, and concrete is poured into the formwork through a layered pouring method after binding; the horizontal jack is started, the prefabricated sections are pushed forwards step by step, and the steps are repeated till all the prefabricated sections are pushed to the designed positions; beam falling preparation work is carried out, the jack is started to slowly fall the bridge, and the bridge is gradually transferred to the designed support from the pushing support; the pushing support adopts a segmented prefabrication and continuous pushing mode, the construction period is greatly shortened, the construction efficiency is improved, meanwhile, through continuous pushing, the overall performance of a bridge is improved, the construction risk is reduced, the pouring complexity is reduced through the prefabricated pedestal and the formwork, the construction safety is improved, and environment protection is facilitated.

Description

Technical Field

[0001] The invention relates to the technical field of construction based on a jacking support, and in particular to a construction method based on a jacking support. Background Art

[0002] In recent years, with the development of transportation, high-grade roads and super-large bridges have flourished in China. In order to ensure the stable support during bridge construction, jacking supports are needed to support them, so as to ensure the stability of the structure during construction, thereby improving its construction safety. At the same time, it ensures the smooth movement of bridge segments during the jacking process to avoid safety accidents such as tilting or collapse, and improves construction efficiency, further speeds up the use progress, and ensures the quality and construction period of the bridge.

[0003] Most of the existing jacking supports have complicated structures and cannot be used and installed according to different terrains or bridges. The scope of application is relatively limited, and the construction period is long, which reduces the construction efficiency and the overall performance of the bridge. In addition, most concrete is poured directly into the steel formwork. During the pouring process, voids and bubbles are easily generated inside the concrete, which reduces the density of the concrete and makes the concrete prone to cracks due to temperature changes or shrinkage. At the same time, it causes uneven force, resulting in stress concentration inside the concrete, making it difficult for the jacking support to work, resulting in a relatively unstable jacking process and reducing the jacking efficiency.

[0004] Therefore, in order to address the above-mentioned problems of long construction period, reduced construction efficiency and reduced overall performance of the bridge, a construction method based on jacking support can be designed. Summary of the invention

[0005] In order to overcome the problem of long construction period, reduced construction efficiency and reduced overall performance of the bridge.

[0006] The technical solution of the present invention is: a construction method based on a jacking support, comprising the following steps:

[0007] S1: Design the jacking support structure according to the structural form of the bridge and the jacking span parameters. After the support structure is determined, weld the steel structures together. After welding, install the slideway on the top of the jacking support.

[0008] S2: A prefabricated pedestal is set up at the prefabrication site. A template is made on the prefabricated pedestal according to the design size of the bridge segment. Rebars are processed and tied on the template according to the drawings. After tying, concrete is poured into the template by layered pouring;

[0009] S3: Install the horizontal jack behind the jacking support, adjust the position and angle of the jacking device, move the prefabricated bridge segment to the starting position of the jacking support through the beam moving device, make the front end of the segment fit tightly with the rear end of the previous segment, and then install the temporary connection device to connect the adjacent segments into a whole;

[0010] S4: Start the horizontal jack and gradually push the precast segment forward. When it reaches the designed position, stop pushing and adjust the thrust of the horizontal jack. Repeat the above steps until all precast segments are pushed to the designed position.

[0011] S5: Carry out preparation work for beam dropping, remove the slideway and temporary support pads on the jacking support, clear the debris and obstacles on the support and bridge surface, set up jacks under the bridge, start the jacks to slowly lower the bridge, and gradually transfer it from the jacking support to the designed support.

[0012] Preferably, the slide is made of stainless steel or polytetrafluoroethylene, the height difference between adjacent slides does not exceed 2 mm, and the deviation between the center line of the slide and the design axis of the bridge does not exceed 5 mm.

[0013] Preferably, the template installation axis deviation does not exceed 5mm, the elevation deviation does not exceed 10mm, and the error of adjacent template joints does not exceed 2mm.

[0014] Preferably, during the steel bar binding process, protective layer pads are set. The pads are made of plastic material, with a spacing of no more than 1m and a plum blossom arrangement. After the concrete is poured, a water spray curing method is used for curing, and the curing time is 7 to 14 days.

[0015] Preferably, the pushing speed is 5 to 10 cm / min, and the beam dropping speed is 3 to 5 mm / min.

[0016] Preferably, the concrete strength is not less than C20 and the pouring thickness is 15 to 30 cm.

[0017] Preferably, a total station is used to monitor the bridge in all directions to measure the plane position and elevation changes of the beam.

[0018] Preferably, during the jacking process, the pressure is applied in three stages, and the displacement value of each stage of pressure is observed by using a micrometer to accurately measure the total displacement value.

[0019] Preferably, during the jacking process, the displacement, stress and strain of the segment are monitored in real time by means of displacement sensors and stress-strain monitoring instruments on the bridge segment. When the beam falls to the designed position, movable supports are installed and the upper and lower parts of the movable supports are welded to the beam and the pier top respectively.

[0020] Preferably, after the beam is dropped, the height difference of the beam body at adjacent supports is 1 to 5 mm, and the deviation between the support center line and the beam body support center line is 1 to 10 mm.

[0021] The beneficial effects of the present invention are as follows: the jacking bracket adopts the method of segmented prefabrication and continuous jacking, which greatly shortens the construction period and ensures that the bridge is smoothly and safely moved to the final position in a short time, thereby improving the construction efficiency. At the same time, segmented prefabrication and continuous jacking reduce the use of high-altitude operations and large lifting equipment, thereby reducing the safety risks in the construction process. Through continuous jacking, the overall performance of the bridge is improved and the construction risk is reduced. The prefabricated pedestal and template reduce the casting complexity and improve the construction safety. At the same time, the noise and vibration of the construction are reduced, which is beneficial to the protection of the environment. In addition, the jacking bracket can be applied to different terrain conditions and bridge structures, thereby increasing its adaptability. Moreover, through the layered pouring of concrete, the thickness of each layer of concrete is moderate, which is convenient for the vibrator to fully vibrate, ensures that there are no gaps and bubbles inside the concrete, and improves the density of the concrete. At the same time, each layer of concrete can be tightly combined with the lower layer of concrete before initial setting, thereby avoiding the problem of cracks caused by temperature changes or concrete shrinkage. The layered poured concrete is subjected to more uniform force during the jacking process, thereby avoiding the difficulty or damage of jacking caused by the internal stress concentration of the concrete, thereby making the jacking process smoother and improving the jacking efficiency. DETAILED DESCRIPTION

[0022] The present invention will be further described below in conjunction with the embodiments.

[0023] The present invention provides an embodiment:

[0024] Example 1

[0025] According to the structural form of the bridge and the parameters of the jacking span, the vertical load borne by the jacking support is calculated. The specific calculation formula is as follows:

[0026] Normal stress of the support structure under load

[0027] σ=F / A

[0028] Where F is the axial force and A is the cross-sectional area;

[0029] Shear stress of the support structure under load

[0030] τ=Fv / IvFv is the shear force, Iv is the polar moment of inertia of the section;

[0031] The critical load is calculated to determine whether the stability requirements are met. The specific calculation formula is as follows:

[0032] Pcr=π2

[0033] P is the critical pressure of the support, and k is the end coefficient of the support. After the support structure is determined, the steel structures are welded together, and after welding, the slideway is installed on the top of the push support. A prefabricated pedestal is set up at the prefabrication site, and a template is made on the prefabricated pedestal according to the design size of the bridge segment. The number of required steel bars is calculated according to the drawings. The specific calculation formula is as follows:

[0034]

[0035] S g is the area of ​​the steel bar layout, a is the steel bar spacing; and then calculate the total weight of the steel bars. The specific calculation formula is as follows:

[0036] G g =ρ g nL g

[0037] ρ g is the density of the steel bars; after the calculation is completed, the steel bars are accurately cut, bent, welded and other processing operations are carried out on the template to ensure that the size, shape and mechanical properties of the steel bars meet the requirements of the specifications; the processed steel bars are transported to the template on the prefabricated pedestal for binding. The steel bars are arranged in a plum blossom shape, and plastic protective layer pads are set. The spacing and position of the pads are strictly controlled to ensure that the thickness of the protective layer of the steel bars in the concrete is uniform and consistent. After bundling, the concrete is poured into the template in layers with a pouring thickness of 15cm. During the pouring process, the concrete is fully vibrated by combining an inserted vibrator and an attached vibrator to ensure the uniformity and density of the concrete, especially in the densely reinforced areas and corners of the template. Vibration is strengthened to prevent quality defects such as honeycombs and hemp surfaces; 12 hours after the concrete pouring is completed, the water spray curing method is used for curing, and the curing time is 14 days. During the curing period, the concrete surface is kept moist at all times, according to the environment According to the changes in ambient temperature and humidity, the frequency and amount of water spraying should be reasonably adjusted. At the same time, moisturizing measures such as covering with plastic film or geotextile should be taken to prevent the water on the concrete surface from evaporating too quickly, ensure that the concrete obtains sufficient water during the hydration process, improve the strength and durability of the concrete, and reduce shrinkage cracks on the concrete surface; install the horizontal jack behind the jacking bracket, adjust the position and angle of the jacking device, ensure that the axis of the jack is consistent with the jacking direction of the beam body, and move the prefabricated bridge segment to the starting position of the jacking bracket through the beam moving equipment. During the movement, strictly control the speed and direction of the beam body to avoid collision with the bracket or other obstacles, so that the front end of the segment is tightly fitted with the rear end of the previous segment, ensure that the width of the joints between adjacent segments is uniform, and then use high-strength bolt connection or welding connection to connect the adjacent segments into a whole; start the horizontal jack, and gradually push the prefabricated segment forward at a speed of 5cm / min. According to the jacking speed, The jacking time of a single bridge section length is calculated, and the single jacking time is added up to the total jacking time; after the jacking time is fixed, when the jacking reaches the designed position, the jacking is stopped and the thrust of the horizontal jack is adjusted, and the above steps are repeated until all prefabricated segments are pushed to the designed position; during the jacking process, the displacement of the stage is monitored in real time through the displacement sensor and stress strain monitoring instrument on the bridge stage, and the actual displacement x is compared with the designed x 设计 The displacement allowable deviation Δx of the jacking trajectory determines whether the jacking is normal. The specific comparison formula is as follows:

[0038] |xx 设计 |≤Δx

[0039] The stress and strain are calculated according to Hooke's law. The specific calculation formula is as follows:

[0040] σ=∑ε

[0041] E is the elastic modulus of the beam material. Compare the actual force σ with the allowable stress [σ] of the material to ensure that σ≤[σ], thereby ensuring that the stress is within the specification range.

[0042] Example 2

[0043] After all prefabricated segments are pushed to the designed position, the preparation for beam dropping is carried out. The slideway and temporary support pads on the pushing bracket are removed. During the removal process, care should be taken to protect the bracket structure and the beam body from damage, and the removed parts should be properly cleaned and stored. At the same time, the debris and obstacles on the bracket and the bridge surface should be completely cleaned to provide a safe and clean working environment for the beam dropping operation. Jacks are set under the bridge. The layout of the jacks is reasonably arranged according to the weight distribution of the beam body and the position of the support to ensure that the beam body can fall smoothly and evenly during the beam dropping process. At the same time, the lifting force of the jack is calculated according to the weight of the beam body. The specific calculation formula is as follows:

[0044]

[0045] G is the weight of the beam, n is the number of jacks, and the safety factor is k=1.2~1.5. The jacks are started to slowly lower the bridge. The beam lowering speed is 3mm / min. The slow speed ensures that the beam is accurately positioned during the lowering process to avoid collision between the beam and the support or uneven settlement of the beam due to excessive speed. During the beam lowering process, high-precision leveling instruments, total stations and other measuring instruments are used to monitor the elevation and plane position of the beam in real time to ensure that the height difference of the beam at adjacent supports is 3mm after the beam is lowered, and the deviation between the support centerline and the beam support centerline is 5mm. When the beam falls to the designed position, the movable support is installed, and the upper and lower parts of the movable support are welded to the beam and the pier top respectively. The welding process is strictly carried out in accordance with the welding process requirements to ensure reliable weld quality, so that the beam is gradually transferred from the jacking support to the designed support to complete the bridge beam lowering operation.

[0046] A construction method based on a jacking support according to the above-mentioned embodiment can significantly shorten the construction period and ensure that the bridge is moved to the final position smoothly and safely in a short time, thereby improving construction efficiency. At the same time, segmented prefabrication and continuous jacking reduce the use of high-altitude operations and large lifting equipment, thereby reducing safety risks in the construction process. Through continuous jacking, the overall performance of the bridge is improved and the construction risk is reduced. The prefabricated pedestal and formwork reduce the complexity of casting and improve construction safety.

[0047] The embodiments of the present invention are described in detail above, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge scope of those skilled in the art without departing from the purpose of the present invention.

Claims

1. A construction method based on a jacking support, comprising the following steps: S1: Design the jacking support structure according to the structural form of the bridge and the jacking span parameters. After the support structure is determined, weld the steel structures together. After welding, install the slideway on the top of the jacking support. S2: A prefabricated pedestal is set up at the prefabrication site. A template is made on the prefabricated pedestal according to the design size of the bridge segment. Rebars are processed and tied on the template according to the drawings. After tying, concrete is poured into the template by layered pouring; S3: Install the horizontal jack behind the jacking support, adjust the position and angle of the jacking device, move the prefabricated bridge segment to the starting position of the jacking support through the beam moving device, make the front end of the segment fit tightly with the rear end of the previous segment, and then install the temporary connection device to connect the adjacent segments into a whole; S4: Start the horizontal jack and gradually push the precast segment forward. When it reaches the designed position, stop pushing and adjust the thrust of the horizontal jack. Repeat the above steps until all precast segments are pushed to the designed position. S5: Carry out preparation work for beam dropping, remove the slideway and temporary support pads on the jacking support, clear the debris and obstacles on the support and bridge surface, set up jacks under the bridge, start the jacks to slowly lower the bridge, and gradually transfer it from the jacking support to the designed support.

2. The construction method based on the jacking support according to claim 1 is characterized in that: The slide is made of stainless steel or polytetrafluoroethylene. The height difference between adjacent slides does not exceed 2mm, and the deviation between the center line of the slide and the design axis of the bridge does not exceed 5mm.

3. The construction method based on the jacking support according to claim 1 is characterized in that: The template installation axis deviation shall not exceed 5mm, the elevation deviation shall not exceed 10mm, and the error of adjacent template joints shall not exceed 2mm.

4. The construction method based on the jacking support according to claim 1 is characterized in that: During the steel bar binding process, protective layer pads are set up. The pads are made of plastic material, with a spacing of no more than 1m and a plum blossom arrangement. After the concrete is poured, water spray curing method is used for curing, and the curing time is 7 to 14 days.

5. The construction method based on the jacking support according to claim 1 is characterized in that: The pushing speed is 5-10cm / min, and the beam dropping speed is 3-5mm / min.

6. The construction method based on the jacking support according to claim 1 is characterized in that: The concrete strength shall not be lower than C20, and the pouring thickness shall be 15 to 30 cm.

7. The construction method based on the jacking support according to claim 1 is characterized in that: A total station is used to monitor the bridge in all directions and measure the plane position and elevation changes of the beam.

8. The construction method based on the jacking support according to claim 1 is characterized in that: During the jacking process, the pressure is applied in three stages and the displacement value of each stage of pressure is observed by using a micrometer to accurately measure the total displacement value.

9. The construction method based on the jacking support according to claim 1 is characterized in that: During the jacking process, the displacement sensors and stress-strain monitoring instruments on the bridge segments are used to monitor the displacement, stress and strain of the segments in real time. When the beam falls to the designed position, the movable bearings are installed and the upper and lower parts of the movable bearings are welded to the beam and the pier top respectively.

10. The construction method based on the jacking support according to claim 1 is characterized in that: After the beam is dropped, the height difference of the beam at adjacent supports is 1 to 5 mm, and the deviation between the support center line and the beam support center line is 1 to 10 mm.

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