A construction method for a prefabricated prestressed material yard elevated platform

Abstract

This invention discloses a construction method for a prefabricated prestressed material yard elevated platform. The method involves prefabricating cantilevered variable cross-section T-shaped cap beams, composite beams, and composite slabs in a processing plant. After the cast-in-place columns are completed, a specialized hoisting and positioning auxiliary device is used to hoist the prefabricated cap beams to the top of the columns and fine-tune their positioning. The cap beams are then connected to the column reinforcement via double-threaded steel bar joints. Subsequently, micro-expansion concrete is used to pour the connection nodes between the cap beams and columns and steam curing is performed. Next, the composite beams and composite slabs are installed sequentially. The pre-reserved reinforcement at both ends of the composite beams is designed with one end longer than the other, so that the connection position of the lower row of reinforcement in the main beam is moved out of the cap beam area. Beam section holes are pre-reserved at the junction of the cap beam and the main beam, and beam supports are prefabricated at the lower part of the beam ends for temporary support during the hoisting of the composite beams. Finally, the integral nodes and the cast-in-place layer of the composite slab surface are poured. This invention can reduce the amount of full-span scaffolding and temporary supports, improve the reliability and installation accuracy of node connections, and shorten the construction cycle.

Description

Technical Field

[0001] This invention relates to the field of metallurgical construction engineering technology, and more specifically, to a construction method for a prefabricated prestressed material yard elevated platform. Background Technology

[0002] With the development of the steel industry, the demand for large-scale enclosed material yards is increasing. Type C enclosed material yards, with their advantages of good environmental performance and high space utilization, have become an important type of material yard in the construction of raw material yards for steel enterprises. The structure of a Type C material yard mainly consists of a raft foundation, intermediate retaining walls, and an elevated platform. The elevated platform is a cantilevered platform supported by independent columns at both ends, typically with a length exceeding 500m, a width of approximately 11m, and a height between 16m and 23.5m.

[0003] Traditionally, elevated platforms in material yards are constructed using full-span scaffolding. This method requires erecting a full-span scaffolding system under the entire elevated platform as a support system before formwork erection, rebar tying, and concrete pouring. This method suffers from several drawbacks, including massive scaffolding usage, high construction costs, scaffolding occupying the entire construction space, hindering the simultaneous execution of other work processes, long scaffolding erection and dismantling cycles, a large amount of work at height, and high safety risks.

[0004] Another existing construction method is the steel support frame plus cantilevered scaffolding construction method. This method uses a steel support frame as the main support system, combined with cantilevered scaffolding for construction operations. Compared with full-span scaffolding, this method reduces the amount of scaffolding used, but it still has problems such as higher costs for steel support frame fabrication and installation, the steel support frame layout still affecting the space below, greater safety risks associated with cantilevered scaffolding, and limited improvement in overall construction efficiency.

[0005] In recent years, prefabricated building technology has been applied in fields such as bridges and housing construction. Existing technologies include composite prefabricated elevated platforms and their assembly methods for C-shaped material yards, as well as rapid prefabricated elevated platforms for C-shaped material yards, providing a foundation for prefabricated construction of elevated platforms in material yards.

[0006] However, existing prefabricated technologies still have the following shortcomings in the application of elevated platforms in material yards: First, they are not adaptable enough to specific working conditions such as long distances, large cantileverages, and narrow construction spaces in elevated platforms; Second, the prefabrication technology for large cantilevered variable cross-section T-shaped components is immature, and existing prefabrication molds and processes are difficult to meet the requirements of large-scale, high-precision prefabrication, easily leading to quality defects such as holes and insufficient compaction; Third, the reliability of node connection technology needs to be improved, and existing grouting sleeve connection technology has problems such as high construction difficulty and difficulty in ensuring quality in scenarios involving large-diameter, high-density steel reinforcement connections; Fourth, the natural curing of node concrete requires a long time to reach the design strength, affecting the turnover and use of the support system; Fifth, the hoisting and positioning of large-tonnage prefabricated cap beams lacks dedicated auxiliary devices, making manual adjustment difficult, inefficient, and posing high safety risks.

[0007] Therefore, there is a need to provide a prefabricated prestressed material yard elevated platform construction method that is efficient, reliable, safe, and economical, specifically designed for the working conditions of the material yard elevated platform. Summary of the Invention

[0008] The purpose of this invention is to address the problems mentioned in the background section by providing a construction method for a prefabricated prestressed material yard elevated platform, which reduces the amount of full-span scaffolding and temporary supports, improves the reliability of node connections and installation accuracy, and shortens the construction cycle.

[0009] The present invention adopts the following technical solution:

[0010] A construction method for a prefabricated prestressed material yard elevated platform includes the following steps:

[0011] S1, Structural Decomposition Design: In accordance with the principle of equivalent cast-in-place construction, the fully cast-in-place T-shaped elevated platform structure is decomposed into cantilevered variable cross-section T-shaped cap beams, main beams connecting the cap beams, and composite slabs. After stress analysis of each precast component, the structural dimensions and reinforcement are adjusted, and the lifting points and connection points are analyzed.

[0012] S2, Precast component factory production: The cantilevered variable cross-section T-shaped cap beam, composite beam and composite slab are precast centrally in the processing plant using special steel molds;

[0013] S3, Cast-in-place column construction: Cast-in-place column part of the intermediate retaining wall of the material yard, and position control of the exposed steel bars at the top of the cast-in-place column;

[0014] S4, Precast Cap Beam Lifting and Positioning: A special lifting and positioning auxiliary device is used to lift the precast cantilevered variable cross-section T-shaped cap beam to the top of the cast-in-place column. The special lifting and positioning auxiliary device includes two support components and a support platform. The two support components can slide and adjust on the support platform to achieve fine-tuning of the position of the cantilevered variable cross-section T-shaped cap beam and the cast-in-place column. The connection between the cantilevered variable cross-section T-shaped cap beam and the cast-in-place column reinforcement is achieved through double threaded steel bar joints.

[0015] S5, Node Concrete Pouring: Micro-expansion concrete is used to pour the connection node between the cantilevered variable cross-section T-shaped cap beam and the cast-in-place column. After pouring, steam curing process is used to accelerate the concrete strength growth.

[0016] S6, Installation of composite beams and slabs: The composite beams and slabs are hoisted sequentially. Reinforcing bars are pre-installed at both ends of the composite beams, with one end longer than the other. The connection point of the lower row of reinforcing bars in the main beam is moved out of the cap beam area. A beam section opening is pre-installed at the connection point between the cap beam and the main beam, and a beam support is pre-fabricated at the lower end of the beam for temporary support during the hoisting of the precast beam. Reinforcing bar connections between components are achieved through double-threaded steel bar joints, and finally, the overall joint is cast in place.

[0017] S7, Slab Concrete Construction: Pour the cast-in-place layer on the surface of the composite slab to complete the construction of the entire elevated platform structure.

[0018] Furthermore, in step S1, the cantilevered variable cross-section T-shaped cap beam is designed to have a length of 11m, a height of 1.2m, and a cantilever length of 2.2m at each end. Reinforcing bars are provided at the connection between the cap beam and the column, and the bottom reinforcing bars of the beam are connected through.

[0019] Furthermore, in step S1, considering that excessive stress at the bottom of the beam during hoisting may cause cracks, the location of the hoisting points is redesigned, and hoisting points are erected in the middle of the beam.

[0020] Furthermore, in step S2, the special steel mold adopts an adjustable design. The mold is precisely processed with reference to the component dimensions of the cap beam design to ensure that the geometric dimension error of each component is controlled within ±5mm.

[0021] Furthermore, in step S3, the concrete pouring height of the cast-in-place column is 16m to 20.9m. A uniform steel plate is used to fix the reinforcement for positioning, ensuring that the cumulative error of the two directional lines of the cast-in-place column, the spacing between columns, the thickness of the protective layer of the top reinforcement of the column, the length of the exposed reinforcement, and the verticality is within 15mm.

[0022] Furthermore, in step S4, the double-threaded steel bar joint adopts the Class I joint standard, the main reinforcement bars connecting the cap beam and the column are staggered within a range of 35d, and the percentage of joints is 50%, where d is the diameter of the connected steel bars.

[0023] Furthermore, in step S5, the micro-expansion concrete is C45 non-shrink fine aggregate concrete, which is one grade higher than the concrete strength grade of the component. The steam curing temperature is controlled at 60℃~80℃, and the curing time is not less than 24 hours.

[0024] Furthermore, in step S6, the threaded joints of the main beam reinforcement are matched with double threaded sleeves.

[0025] Furthermore, in step S1, PKPM and Lizheng Toolbox are used for structural calculations, REVIT is used for 3D modeling to detect rebar collisions, and Fuzor is used to create construction animations.

[0026] Furthermore, the elevated platform has a length of 480m to 620m, a width of 11m to 12m, and a height of 16m to 24.5m.

[0027] Beneficial effects

[0028] Construction efficiency is significantly improved. This invention adopts a construction mode that combines factory prefabrication with on-site assembly, enabling parallel operations. Compared with traditional full-span scaffolding construction methods, the overall construction efficiency is increased by more than 40%. The joints utilize steam curing technology, which increases the concrete strength gain rate by 2 to 3 times, and greatly improves the turnover efficiency of the support system.

[0029] Construction costs are significantly reduced. This invention eliminates the need for a full-scale scaffolding system, reducing construction costs by over 35%. Factory prefabrication improves material utilization and reduces on-site waste. The support system is recyclable, further reducing construction costs.

[0030] Construction space is significantly freed up. This invention adopts prefabricated construction, with on-site operations mainly involving hoisting and node pouring. This frees up construction space below, creating conditions for other processes to be carried out simultaneously, enabling multiple processes to be carried out in parallel and shortening the overall project duration.

[0031] The structure boasts reliable quality. This invention employs double-threaded steel bar joint technology, achieving connection quality up to Class I joint standards, realizing performance equivalent to cast-in-place connections. Factory prefabrication ensures stable component quality, avoiding fluctuations in on-site construction quality. Micro-expansion concrete is used at joints, effectively reducing the risk of shrinkage cracks.

[0032] Safety risks are significantly reduced. This invention drastically reduces the amount of work at height, decreasing scaffolding usage by over 90%, with workers primarily operating on the ground and protected platforms. A specialized hoisting positioning auxiliary device improves the safety and accuracy of hoisting operations.

[0033] The environmental benefits are significant. This invention reduces on-site wet work, lowering dust and noise pollution. The formwork and support system are reusable, reducing construction waste and aligning with the development trends of green construction and building industrialization.

[0034] Highly adaptable. This invention is optimized for the specific working conditions of elevated platforms in material yards, and can adapt to the construction of elevated platforms of different lengths, heights, and cantilever dimensions, thus having broad application prospects. Attached Figure Description

[0035] Figure 1 This is a flowchart of the construction process of the present invention.

[0036] Figure 2 This is a design drawing for the connection between the precast cap beam and the cast-in-place section.

[0037] Figure 3 A schematic diagram of the prefabricated component of the retaining wall for the T-shaped elevated platform – the cap beam.

[0038] Figure 4 A schematic diagram of the prefabricated component of the retaining wall for the T-shaped elevated platform – the composite beam.

[0039] Figure 5 A schematic diagram of prefabricated composite slabs for the retaining wall of a T-shaped elevated platform.

[0040] Figure 6 This is a diagram showing the location of the lifting points for the cap beam.

[0041] Figure 7 This is a schematic diagram of the reinforcement at the bottom of the cap beam.

[0042] Figure 8 This is a design drawing for the connection point between the cap beam and the cast-in-place section.

[0043] Figure 9 This is a design drawing for the connection between the cap beam and the main beam.

[0044] Figure 10 This is a rendering of the cast-in-place column construction. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0046] Example 1

[0047] This example project is a comprehensive material yard project under the capacity replacement and upgrading renovation project of a steel group company in Yunnan Province. The C-shaped material silo elevated platform is 510m long and 11m wide, with a platform height ranging from 16m to 23.5m. The seismic fortification intensity is 8 degrees, the basic design seismic acceleration is 0.2g, and the seismic resistance level is level three. Except for the columns, the upper part of the retaining wall, at an elevation of 16.0m to 23.5m, adopts a prefabricated design scheme.

[0048] The construction steps are as follows:

[0049] 1. Structural decomposition design.

[0050] The fully cast-in-place T-shaped elevated platform structure is divided into three main precast components: cantilevered variable cross-section T-shaped cap beams, main beams 2 connecting the cap beams 3, and composite slabs 1. The cap beams are designed to be 11m long and 1.2m high, with cantilever lengths of 2.2m at each end. Double-threaded steel bar joints are used for node connections; the joints are Class I joints. PKPM is used for structural calculations, Revit is used for 3D modeling and rebar collision detection, and Fuzor is used to create construction animations.

[0051] 2. Prefabricated components are manufactured in factories.

[0052] A dedicated steel mold production line is set up in the precast component plant to mass-produce cantilevered variable cross-section T-shaped cap beams, composite beams, and composite slabs. The cap beam molds are adjustable steel molds, each of which can be reused more than 50 times. The concrete mix ratio is strictly controlled during the precasting process, and steam curing is used to ensure the strength of the components.

[0053] 3. Construction of cast-in-place columns.

[0054] Four cast-in-place columns were poured for the intermediate retaining wall, with a total height of 20.9m. Custom-made steel plate molds were used to fix the position of the top reinforcing bars, ensuring that the positional deviation of the reinforcing bars was controlled within ±10mm. The column concrete was C40, and it was naturally cured after pouring.

[0055] 4. Hoisting and positioning of precast cap beams.

[0056] A 130-ton truck crane was used for hoisting the cap beams, with each cap beam weighing approximately 45 tons. A specialized hoisting and positioning auxiliary device was used; first, two support components were placed on top of the columns, and then the cap beam was hoisted into position. Precise positioning was achieved through the sliding adjustment of the support components. Double-threaded steel bar joints were used to connect the cap beams and column reinforcement, with a joint rate of 50%.

[0057] 5. Node concrete pouring and curing.

[0058] The joints were constructed using C45 non-shrink fine-aggregate micro-expansion concrete. Immediately after pouring, a steam curing hood was installed for steam curing at a temperature controlled at 70℃±5℃ for 24 hours. After curing, the concrete strength reached more than 85% of the design strength, and the supporting frame could be removed for reuse.

[0059] 6. Installation of composite beams and composite slabs.

[0060] The composite beams and composite slabs were hoisted sequentially. The composite beams featured unequal-length reinforcing bars at both ends, with the lower row of reinforcing bar connection nodes moved out of the cap beam area for easier operation. Pre-installed beam supports on the cap beam served as temporary supports during the hoisting of the composite beams. Double-threaded steel bar joints were used to connect the reinforcing bars of each component, and finally, the joint concrete was poured.

[0061] 7. Construction of slab concrete.

[0062] The slab reinforcement was tied, and a C35 concrete cast-in-place layer was poured. Mechanical vibration was used for compaction, and the slab was then covered with a membrane for curing.

[0063] After adopting the technology of this invention, the construction period of the elevated platform was shortened from the planned 120 days to 72 days, and the construction efficiency was increased by 40%. The cost of the measures was reduced by 3.2 million yuan, a decrease of 38%. No safety accidents occurred during the construction period, and the project quality passed the acceptance inspection on the first attempt.

[0064] Example 2

[0065] This example project is the second phase of the green and intelligent transformation project for the raw material yard of a steel company. The C-shaped silo elevated platform is 480m long, 11m wide, and 17.5m to 22.8m high. The construction site for this project is small, with many existing production facilities nearby, and has high requirements for construction safety and environmental protection.

[0066] The construction steps are as follows:

[0067] 1. Structural decomposition design.

[0068] Given the limited site conditions of this project, the component disassembly scheme was optimized, dividing the cap beam into standard sections and adjustment sections. The standard sections are uniformly 11m in length to facilitate factory production, while the adjustment sections are customized according to the actual dimensions on site. Double-threaded steel bar joints are used for node connections.

[0069] 2. Prefabricated components are manufactured in factories.

[0070] Production is carried out at nearby prefabrication plants to reduce transportation distances. Improved adjustable steel molds are used for the cap beams to enhance mold versatility. Automated vibration equipment is used during prefabrication to ensure concrete compaction.

[0071] 3. Construction of cast-in-place columns.

[0072] The cast-in-place columns were constructed using a skip-pour method to minimize disruption to surrounding production. High-precision measurement technology was employed to control the column position and verticality, and the top reinforcing bars were fixed using positioning frames to ensure positional accuracy.

[0073] 4. Hoisting and positioning of precast cap beams.

[0074] A 100-ton crawler crane was used for lifting, which is suitable for working conditions with limited space. An improved lifting and positioning auxiliary device was used to improve positioning efficiency, reducing the average positioning time for each cap beam from 40 minutes to 25 minutes.

[0075] 5. Node concrete pouring and curing.

[0076] C45 micro-expansion concrete was used, with steam curing at 65℃ for 24 hours. The supports were removed immediately after curing, and the structure was moved to the next construction section.

[0077] 6. Installation of composite beams and composite slabs.

[0078] The assembly line operation method is adopted, and the installation of the composite beam begins after every 3 cap beams are completed, realizing parallel operation of multiple processes.

[0079] 7. Construction of slab concrete.

[0080] The segmented casting method is adopted to improve the efficiency of slab construction.

[0081] By employing this invention, the elevated platform construction was successfully completed in a confined space, minimizing the impact on surrounding production facilities. The construction period was 68 days, 42 days shorter than traditional methods. Zero accidents were reported, and environmental standards were met.

[0082] Example 3: Expansion Project of Integrated Material Yard of a Large Steel Enterprise

[0083] This example project is the expansion of a comprehensive material yard for a large steel enterprise. The C-type material silo elevated platform is 620m long, 12m wide, and 18m-24.5m high. The project has a tight schedule, requiring the elevated platform construction to be completed within 80 days.

[0084] The construction steps are as follows:

[0085] 1. Structural decomposition design.

[0086] Standardized design is adopted, with all cap beams, composite beams, and composite slabs using uniform dimensions to maximize factory production. Optimized node design further improves assembly efficiency.

[0087] 2. Prefabricated components are manufactured in factories.

[0088] Two prefabrication production lines were set up and two shifts were implemented to ensure that the supply speed of components could meet the on-site hoisting requirements.

[0089] 3. Construction of cast-in-place columns.

[0090] Multiple work surfaces were constructed simultaneously, and all cast-in-place columns were completed within 40 days.

[0091] 4. Hoisting and positioning of precast cap beams.

[0092] With two large cranes operating simultaneously, eight cap beams can be hoisted and positioned each day.

[0093] 5. Node concrete pouring and curing.

[0094] The efficient steam curing process allows the mold to be removed in just 18 hours, further improving the turnover efficiency of the support system.

[0095] 6. Installation of composite beams and composite slabs.

[0096] A prefabricated construction platform is used to improve installation efficiency and safety.

[0097] 7. Construction of slab concrete.

[0098] Ultra-early strength concrete is used to shorten the curing time.

[0099] The entire elevated platform construction was completed in just 76 days, four days ahead of schedule as required by the client. The project quality was excellent, and costs were kept within budget.

[0100] The above description is merely a preferred embodiment of the present invention; however, the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and its improved concepts, should be covered within the scope of protection of the present invention.

Claims

1. A construction method for a prefabricated prestressed material yard elevated platform, characterized in that, Includes the following steps: S1, Structural Decomposition Design: In accordance with the principle of equivalent cast-in-place construction, the fully cast-in-place T-shaped elevated platform structure is decomposed into cantilevered variable cross-section T-shaped cap beams, main beams connecting the cap beams, and composite slabs. After stress analysis of each precast component, the structural dimensions and reinforcement are adjusted, and the lifting points and connection points are analyzed. S2, Precast component factory production: The cantilevered variable cross-section T-shaped cap beam, composite beam and composite slab are precast centrally in the processing plant using special steel molds; S3, Cast-in-place column construction: Cast-in-place column part of the intermediate retaining wall of the material yard, and position control of the exposed steel bars at the top of the cast-in-place column; S4, Precast Cap Beam Lifting and Positioning: A special lifting and positioning auxiliary device is used to lift the precast cantilevered variable cross-section T-shaped cap beam to the top of the cast-in-place column. The special lifting and positioning auxiliary device includes two support components and a support platform. The two support components can slide and adjust on the support platform to achieve fine-tuning of the position of the cantilevered variable cross-section T-shaped cap beam and the cast-in-place column. The connection between the cantilevered variable cross-section T-shaped cap beam and the cast-in-place column reinforcement is achieved through double threaded steel bar joints. S5, Node Concrete Pouring: Micro-expansion concrete is used to pour the connection node between the cantilevered variable cross-section T-shaped cap beam and the cast-in-place column. After pouring, steam curing process is used to accelerate the concrete strength growth. S6, Installation of composite beams and slabs: The composite beams and slabs are hoisted sequentially. Reinforcing bars are pre-installed at both ends of the composite beams, with one end longer than the other. The connection point of the lower row of reinforcing bars in the main beam is moved out of the cap beam area. A beam section opening is pre-installed at the connection point between the cap beam and the main beam, and a beam support is pre-fabricated at the lower end of the beam for temporary support during the hoisting of the precast beam. Reinforcing bar connections between components are achieved through double-threaded steel bar joints, and finally, the overall joint is cast in place. S7, Slab Concrete Construction: Pour the cast-in-place layer on the surface of the composite slab to complete the construction of the entire elevated platform structure.

2. The construction method for a prefabricated prestressed material yard elevated platform according to claim 1, characterized in that: In step S1, the cantilevered variable cross-section T-shaped cap beam has a design length of 11m, a height of 1.2m, and a cantilever length of 2.2m at each end. Reinforcing bars are provided at the connection between the cap beam and the column, and the bottom reinforcing bars of the beam are connected through.

3. The construction method for a prefabricated prestressed material yard elevated platform according to claim 1, characterized in that: In step S1, considering the possibility of cracks due to excessive stress at the bottom of the beam during hoisting, the location of the hoisting points was redesigned, and hoisting points were erected in the middle of the beam.

4. The construction method for a prefabricated prestressed material yard elevated platform according to claim 1, characterized in that: In step S2, the special steel mold adopts an adjustable design. The mold is precisely processed with reference to the component dimensions of the cap beam design to ensure that the geometric dimension error of each component is controlled within ±5mm.

5. The construction method for a prefabricated prestressed material yard elevated platform according to claim 1, characterized in that: In step S3, the concrete pouring height of the cast-in-place column is 16m to 20.9m. A uniform steel plate is used to fix the reinforcement for positioning, ensuring that the cumulative error of the two directional lines of the cast-in-place column, the spacing between columns, the thickness of the protective layer of the top reinforcement of the column, the length of the exposed reinforcement, and the verticality is within 15mm.

6. The construction method for a prefabricated prestressed material yard elevated platform according to claim 1, characterized in that: In step S4, the double-threaded steel bar joint adopts the Class I joint standard. The main reinforcement bars connecting the cap beam and the column are staggered within a range of 35d. The percentage of joints is 50%, where d is the diameter of the connected steel bars.

7. The construction method for a prefabricated prestressed material yard elevated platform according to claim 1, characterized in that: In step S5, the micro-expansion concrete is C45 non-shrink fine aggregate concrete, which is one grade higher than the concrete strength grade of the component. The steam curing temperature is controlled at 60℃~80℃ and the curing time is not less than 24 hours.

8. The construction method of a prefabricated prestressed material yard elevated platform according to claim 1, characterized in that: In step S6, the main beam reinforcement connection nodes are threaded and fitted with double threaded sleeves.

9. A construction method for a prefabricated prestressed material yard elevated platform according to claim 1, characterized in that: In step S1, PKPM and Lizheng Toolbox are used for structural calculations, REVIT is used for 3D modeling to detect rebar collisions, and Fuzor is used to create construction animations.

10. A construction method for a prefabricated prestressed material yard elevated platform according to claim 1, characterized in that: The elevated platform is 480m to 620m long, 11m to 12m wide, and 16m to 24.5m high.

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