Prefabricated method for overturning of assembled guardrails

Abstract

The present application relates to guardrail preparation technical field, disclose a kind of assembled guardrail overturn prefabrication method, comprising the following steps: construction preparation, template polishing cleaning and inverting, reinforcement cage into mould, template fixing and concrete pouring, template overturn self-demoulding and guardrail's removal and transport, storage and maintenance.The present application utilizes the structural features of assembled guardrail, the bottom wide face is used as concrete pouring opening, which greatly reduces the difficulty of concrete feeding and vibrating, effectively reduces common defects of concrete quality such as air bubbles, voids, improves the structural strength and appearance quality of guardrail component, the surface of the component after pouring is smooth and straight, with high dimensional accuracy.

Description

Technical Field

[0001] This invention relates to the field of guardrail manufacturing technology, specifically to a prefabricated method for rotating assembled guardrails. Background Technology

[0002] Bridge railings are important protective facilities for ensuring road traffic safety, and their construction quality and efficiency directly affect the overall progress and safety performance of bridge projects.

[0003] Traditional bridge railings mostly employ cast-in-place construction, which suffers from problems such as cumbersome formwork erection and dismantling, difficulty in controlling the alignment, unstable appearance quality, and long construction periods. Similarly, conventional formwork casting methods for prefabricated railings also have many drawbacks: low construction efficiency, numerous common concrete quality defects, inconvenient formwork reuse, and potential damage to the edges and surfaces of railing components during demolding, increasing later repair costs. Furthermore, the casting method often uses the narrow top face of the railing as the pouring port, making concrete feeding and vibration difficult, easily leading to quality problems such as air bubbles, voids, and insufficient compaction, affecting the structural strength and service life of the railing. Therefore, we propose a prefabricated flip-over method for prefabricated railings. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned shortcomings and provide a prefabricated method for rotating assembled guardrails.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a prefabricated method for rotating and flipping prefabrication of assembled guardrails, comprising the following steps: S1. Construction preparation: Plan and harden the prefabrication site, re-inspect the incoming materials and determine the concrete mix ratio that meets the requirements of inverted pouring, customize the flipping template with semi-circular arc flipping track and complete the acceptance, inspect the construction equipment and provide special technical briefing and safety training to the workers. S2. Grinding, cleaning and inverting the template: Remove welding slag, rust, oil and concrete residue from the inner surface of the template, grind the contact surface smooth, apply release agent evenly and let it dry, embed grout-stop strips at the template joints and control their compression to 20%-30%, and check the overall dimensions of the template after assembly. S3. Rebar cage placement: Process the rebar cage according to the drawings and set up protective layer pads. Fix the embedded parts with the positioning jig, invert the rebar cage and hoist it into the inner cavity of the formwork and fix it with a pressure bar to prevent it from floating. Precisely install the core mold and seal the grouting holes. S4. Formwork fixing and concrete pouring: Use supports to firmly lock the formwork to the ground. Use the bottom wide side of the guardrail as the pouring port. Pour concrete in layers with each layer being ≤30cm thick. Use a Φ50 high-frequency immersion vibrator to vibrate. When pouring the last layer, accurately control the top surface of the concrete to be 5±2mm lower than the upper edge of the formwork. S5. Self-demolding by template flipping: Remove the core mold 6 hours after the concrete pouring is completed. When the strength of the test specimens cured under the same conditions is ≥20MPa, clean the flipping area and lay square timber and waste tires to form a buffer zone. After the template support is removed, the template is flipped 180° at a uniform speed through the lifting points of the semi-circular flipping track. The guardrail components automatically detach from the template by their own weight. If there is local adhesion, use a wooden mallet or rubber mallet to tap the side wall of the template to assist in demolding. It is forbidden to knock on the components or forcibly pry them. S6. Moving, storing and maintaining: Use gantry cranes or forklifts to move the guardrail components smoothly. Set the lifting points or support points at the ends of the guardrail components. When storing the components, use long rectangular wooden supports. When stacking, align the support points of the upper and lower layers. After demolding, immediately cover with a water-retaining film and continue to keep moist for no less than 7 days. Take corresponding temperature and humidity control measures in winter and summer.

[0006] Furthermore, the prefabrication site must be firm, flat, and well-drained, with a load-bearing capacity sufficient to support the rotation of large formwork and the operation of gantry cranes.

[0007] Furthermore, the slump of the concrete pouring is controlled at 160±20mm. During vibration, the vibrator is inserted quickly and withdrawn slowly, vertically inserted into the lower layer of concrete for 5-10cm, with a vibration point spacing of ≤30cm. The vibration time at each point is 20-30 seconds until the concrete surface is covered with slurry and no significant air bubbles escape.

[0008] Furthermore, the space of the flipping area is not less than 3.5 times the height of the component, and the operator must remain in the safe area throughout the process and is prohibited from standing in the template flipping path.

[0009] Furthermore, the components are not in direct contact with the ground when stored, and ventilation gaps of not less than 10cm are left between the components. The maintenance adopts a fully automatic spray system for continuous moisturization.

[0010] Furthermore, this method is applicable to the construction of low guardrails on bridges that are narrow at the top and wide at the bottom, with straight lines and no protruding structures in the middle.

[0011] Furthermore, the protective layer pads are high-strength mortar pads or special plastic retaining rings, arranged in a quincunx pattern with a spacing of no more than 50cm.

[0012] Furthermore, the acceptance of the flipping template includes checking the structural strength and rigidity, the accuracy of the semi-circular flipping track, dimensional accuracy, joint sealing, and compatibility of the release agent.

[0013] Furthermore, the semi-circular arc flipping track must meet the requirements of accurate radius of curvature, smooth and wear-resistant surface, firm connection with the template body, and flipping shafts or lifting points at both ends of the track.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention utilizes the structural characteristics of prefabricated guardrails, which are narrow at the top and wide at the bottom, and uses the wide bottom surface as the concrete pouring port. This significantly reduces the difficulty of concrete feeding and vibration, effectively reduces common concrete quality defects such as air bubbles and voids, and improves the structural strength and appearance quality of guardrail components. The poured components have smooth and straight surfaces and high dimensional accuracy.

[0015] 2. This invention achieves automatic demolding of guardrail components by customizing a special template with a semi-circular rotating track and precisely controlling the concrete top surface to be 5±2mm lower than the upper edge of the template. This eliminates the need for manual prying or strong pulling by large equipment, avoiding damage to the edges and surfaces of the components during demolding and achieving non-destructive demolding. At the same time, it greatly simplifies the demolding process and significantly improves the demolding speed.

[0016] 3. The construction method of the present invention does not require frequent disassembly and assembly of formwork, which reduces the frequency of use of large equipment such as gantry cranes and effectively saves prefabrication site, labor and machinery costs. Attached Figure Description

[0017] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a flowchart of a prefabricated method for rotating prefabricated guardrails. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Reference Figure 1 A prefabricated method for rotating prefabricated guardrails includes the following steps: S1. Construction preparation: Plan and harden the prefabrication site, re-inspect the incoming materials and determine the concrete mix ratio that meets the requirements of inverted pouring, customize the flipping template with semi-circular arc flipping track and complete the acceptance, inspect the construction equipment and provide special technical briefing and safety training to the workers. S2. Grinding, cleaning and inverting the template: Remove welding slag, rust, oil and concrete residue from the inner surface of the template. Grind the contact surface smooth (Ra≤6.3μm). Apply release agent evenly and let it dry. The release agent is emulsified oil and polymer. Embed grout-stopping strips such as closed-cell foam rubber strips or EPDM rubber strips at the template joints. Control the compression of the grout-stopping strips to 20%-30%. Check the overall dimensions of the template after assembly. S3. Rebar cage placement: Process the rebar cage according to the drawings and set up protective layer pads. Fix the embedded parts with the positioning jig, invert the rebar cage and hoist it into the inner cavity of the formwork and fix it with a pressure bar to prevent it from floating. Precisely install the core mold and seal the grouting holes. S4. Formwork fixing and concrete pouring: Use supports to firmly lock the formwork to the ground. Use the bottom wide side of the guardrail as the pouring port. Pour concrete in layers with each layer being ≤30cm thick. Use a Φ50 high-frequency immersion vibrator to vibrate. When pouring the last layer, accurately control the top surface of the concrete to be 5±2mm lower than the upper edge of the formwork. S5. Self-demolding by template flipping: Remove the core mold 6 hours after the concrete pouring is completed. When the strength of the test specimens cured under the same conditions is ≥20MPa, clean the flipping area and lay square timber and waste tires to form a buffer zone. After the template support is removed, the template is flipped 180° at a uniform speed through the lifting points of the semi-circular flipping track. The guardrail components automatically detach from the template by their own weight. If there is local adhesion, use a wooden mallet or rubber mallet to tap the side wall of the template to assist in demolding. It is forbidden to knock on the components or forcibly pry them. S6. Moving, storing and maintaining: Use a gantry crane or forklift to move the guardrail components smoothly. Set the lifting points or supports at the ends of the guardrail components, with the lifting points located 1 / 4 to 1 / 5 of the way from the end of the guardrail. Use special lifting tools or nylon slings to keep the components level and stable. When storing the components, use long rectangular wooden supports. When stacking, align the support points of the upper and lower layers. After demolding, immediately cover with a water-retaining film and continue to keep moist for no less than 7 days. Take corresponding temperature and humidity control measures in winter and summer.

[0020] The prefabrication site must be firm, flat, and well-drained, and its load-bearing capacity must be able to support the flipping of large formwork and the operation of gantry cranes.

[0021] The slump of the concrete pouring should be controlled at 160±20mm. When vibrating, the vibrator should be inserted quickly and withdrawn slowly, vertically inserted into the lower layer of concrete for 5-10cm. The spacing between vibration points should be ≤30cm, and the vibration time for each point should be 20-30 seconds until the concrete surface is covered with slurry and no significant air bubbles escape.

[0022] The space in the flipping area should be no less than 3.5 times the height of the component. Operators must remain in the safe area throughout the process and are prohibited from standing in the formwork flipping path.

[0023] The components are stored without direct contact with the ground, and ventilation gaps of no less than 10cm are left between the components. A fully automatic spray system is used for continuous moisturizing during maintenance.

[0024] This method is suitable for the construction of low guardrails on bridges that are narrow at the top and wide at the bottom, with straight lines and no protruding structures in the middle.

[0025] The protective layer pads are high-strength mortar pads or special plastic clips, arranged in a quincunx pattern with a spacing of no more than 50cm.

[0026] Acceptance of the flip-up template includes checking the structural strength and rigidity, the accuracy of the semi-circular flip-up track, dimensional accuracy, joint sealing, and compatibility of the release agent.

[0027] The semi-circular arc flipping track must meet the requirements of accurate radius of curvature, smooth and wear-resistant surface, firm connection with the template body, and flipping shafts or lifting points at both ends of the track.

[0028] Working principle: The prefabrication site is planned and hardened; incoming materials are re-inspected and the concrete mix ratio that meets the requirements for inverted casting is determined; a custom-made inverted formwork with a semi-circular inverted track is completed and accepted; construction equipment is inspected and workers are given specialized technical briefings and safety training; then, welding slag, rust, oil stains, and concrete residue are removed from the inner surface of the formwork; the contact surfaces are polished smooth (Ra≤6.3μm); a release agent is evenly applied and dried; the release agent is an emulsified oil and a high-molecular polymer, etc.; grout-stopping strips, such as closed-cell foam rubber strips or EPDM rubber strips, are embedded at the joints of the formwork, and the compression of the grout-stopping strips is controlled to be 20%— 30% of the work was completed. After assembly, the overall dimensions of the formwork were checked. The reinforcing cage was fabricated according to the drawings, and protective layer pads were installed. The embedded parts were fixed using a positioning jig. The reinforcing cage was inverted and hoisted into the formwork cavity, and a pressure bar was used to fix it to prevent it from floating. The core mold was precisely installed and the grouting holes were sealed. The formwork was firmly locked to the ground using supports. The bottom wide side of the guardrail was used as the pouring port. Concrete was poured in layers, with each layer ≤30cm thick. A Φ50 high-frequency immersion vibrator was used for vibration. When pouring the last layer, the top surface of the concrete was precisely controlled to be 5±2mm lower than the upper edge of the formwork. The core mold was removed 6 hours after the concrete was poured. The specimen strength was ≥20MPa after curing under the same conditions. During the process, the overturning area is cleaned and square timber and waste tires are laid to form a buffer zone. After the formwork support is removed, the entire formwork is rotated 180° at a uniform speed through the lifting points of the semi-circular overturning track. The guardrail components automatically detach from the formwork by their own weight. If there is local adhesion, use a wooden mallet or rubber mallet to tap the side wall of the formwork to assist in demolding. It is forbidden to knock on the components or forcibly pry them. Use a gantry crane or forklift to move the guardrail components smoothly. Set the lifting points or support points at the ends of the guardrail components. The lifting point position is close to 1 / 4 to 1 / 5 of the end of the guardrail. Use special lifting tools or nylon slings to keep the components horizontal and stable. When storing the components, use long square timber for support. When stacking, align the support points of the upper and lower layers. After demolding, immediately cover with a water-retaining film and continue to keep moist for no less than 7 days. Take corresponding temperature and humidity control measures in winter and summer.

[0029] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A prefabricated method for rotating prefabricated guardrails, characterized in that, Includes the following steps: S1. Construction preparation: Plan and harden the prefabrication site, re-inspect the incoming materials and determine the concrete mix ratio that meets the requirements of inverted pouring, customize the flipping template with semi-circular arc flipping track and complete the acceptance, inspect the construction equipment and provide special technical briefing and safety training to the workers. S2. Grinding, cleaning and inverting the template: Remove welding slag, rust, oil and concrete residue from the inner surface of the template, grind the contact surface smooth, apply release agent evenly and let it dry, embed grout-stop strips at the template joints and control their compression to 20%-30%, and check the overall dimensions of the template after assembly. S3. Rebar cage placement: Process the rebar cage according to the drawings and set up protective layer pads. Fix the embedded parts with the positioning jig, invert the rebar cage and hoist it into the inner cavity of the formwork and fix it with a pressure bar to prevent it from floating. Precisely install the core mold and seal the grouting holes. S4. Formwork fixing and concrete pouring: Use supports to firmly lock the formwork to the ground. Use the bottom wide side of the guardrail as the pouring port. Pour concrete in layers with each layer being ≤30cm thick. Use a Φ50 high-frequency immersion vibrator to vibrate. When pouring the last layer, accurately control the top surface of the concrete to be 5±2mm lower than the upper edge of the formwork. S5. Self-demolding by template flipping: Remove the core mold 6 hours after the concrete pouring is completed. When the strength of the test specimens cured under the same conditions is ≥20MPa, clean the flipping area and lay square timber and waste tires to form a buffer zone. After the template support is removed, the template is flipped 180° at a uniform speed through the lifting points of the semi-circular flipping track. The guardrail components automatically detach from the template by their own weight. If there is local adhesion, use a wooden mallet or rubber mallet to tap the side wall of the template to assist in demolding. It is forbidden to knock on the components or forcibly pry them. S6. Moving, storing and maintaining: Use gantry cranes or forklifts to move the guardrail components smoothly. Set the lifting points or support points at the ends of the guardrail components. When storing the components, use long rectangular wooden supports. When stacking, align the support points of the upper and lower layers. After demolding, immediately cover with a water-retaining film and continue to keep moist for no less than 7 days. Take corresponding temperature and humidity control measures in winter and summer.

2. The prefabrication method for rotating prefabricated guardrails as described in claim 1, characterized in that: The prefabrication site must be firm, flat, and well-drained, with a load-bearing capacity sufficient to support the rotation of large formwork and the operation of gantry cranes.

3. The prefabrication method for rotating prefabricated guardrails as described in claim 1, characterized in that: The slump of the concrete pouring is controlled at 160±20mm. During vibration, the vibrator is inserted quickly and withdrawn slowly, vertically inserted into the lower layer of concrete for 5-10cm, with a vibration point spacing of ≤30cm. The vibration time at each point is 20-30 seconds until the concrete surface is covered with slurry and no significant air bubbles escape.

4. The prefabrication method for rotating prefabricated guardrails as described in claim 1, characterized in that: The space in the flipping area shall be no less than 3.5 times the height of the component. Operators shall remain in the safe area throughout the entire process and shall not stand in the template flipping path.

5. The prefabrication method for rotating prefabricated guardrails as described in claim 1, characterized in that: The components are not in direct contact with the ground when stored, and ventilation gaps of not less than 10cm are left between the components. The maintenance adopts a fully automatic spray system for continuous moisturization.

6. The prefabrication method for rotating prefabricated guardrails as described in claim 1, characterized in that: This method is suitable for the construction of low guardrails on bridges that are narrow at the top and wide at the bottom, with straight lines and no protrusions in the middle.

7. The prefabrication method for rotating prefabricated guardrails as described in claim 1, characterized in that: The protective layer pads are high-strength mortar pads or special plastic clips, arranged in a quincunx pattern with a spacing of no more than 50cm.

8. The prefabrication method for rotating prefabricated guardrails as described in claim 1, characterized in that: The acceptance of the flipping template includes checking the structural strength and rigidity, the accuracy of the semi-circular flipping track, dimensional accuracy, joint sealing, and compatibility of the release agent.

9. A prefabricated method for rotating prefabricated guardrails as described in claim 1, characterized in that: The semi-circular arc flipping track must meet the requirements of accurate radius of curvature, smooth and wear-resistant surface, firm connection with the template body, and flipping shafts or lifting points at both ends of the track.

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