A prefabricated prestressed concrete hollow beam

Abstract

A prefabricated prestressed concrete hollow beam relates to the field of building structure engineering, including a hollow beam body, a cover plate and a steel skeleton arranged in the hollow beam body, the cross section of the hollow beam body is U-shaped, the cover plate is arranged at the inner edge of the upper opening of the hollow beam body, the cover plate and the hollow beam body cooperate with each other to form a cavity, the steel skeleton includes bottom bars, upper prestressed bars and U-shaped stirrups, a plurality of bottom prestressed bars are arranged between the left and right bottom bars, and the bottom prestressed bars and the bottom bars are arranged in parallel; the prestressed bars are tensioned by the pre-tensioning method, the concrete is poured to a certain height, the inner template is placed and fixed, the gap between the inner template and the outer template is poured with concrete, the excess prestressed bars are released and sheared after the concrete is formed, the template is removed and the cover plate is bonded to the groove by mortar to form a closed cavity. The invention reduces the dead weight of the structure, reduces the amount of steel bars and concrete, and greatly improves the anti-cracking and anti-deformation capabilities of the component.

Description

Technical Field

[0001] The invention relates to the field of building structure engineering, in particular to a prefabricated prestressed concrete hollow beam. Background Art

[0002] In recent years, in order to promote the industrialization of construction, promote prefabricated buildings, and speed up the production of prefabricated components, the country has issued a series of relevant policies. Since 2015, my country has successively issued specifications for prefabricated buildings. The "Industrialized Building Evaluation Specifications" proposed to build prefabricated buildings on a large scale across the country starting from 2016. Prefabricated buildings have the advantages of short construction period, good quality, environmental protection and energy saving, and saving manpower and material resources. Beams are commonly used load-bearing components in building structures. At this stage, my country's composite beam components are mainly reinforced concrete composite beam components, which are heavy, prone to cracks, and have low crack resistance. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a prefabricated prestressed concrete hollow beam with low deadweight and crack resistance in view of the deficiencies in the prior art.

[0004] The technical problem to be solved by the present invention is achieved through the following technical solution. The present invention is a prefabricated prestressed concrete hollow beam:

[0005] 1. It includes a hollow beam body, a cover plate and a steel bar skeleton arranged in the hollow beam body, the cross section of the hollow beam body is U-shaped, the cover plate is arranged at the inner edge of the upper opening of the hollow beam body, the cover plate and the hollow beam body cooperate with each other to form a closed cavity structure, the steel bar skeleton includes bottom bars, upper prestressed bars and U-shaped stirrups, a plurality of U-shaped stirrups are placed in parallel along the length direction of the hollow beam body, the left and right bottom bars and the U-shaped stirrups are arranged vertically, the two upper prestressed bars and the bottom bars are arranged in parallel, a plurality of bottom prestressed bars are arranged between the left and right bottom bars, and the bottom prestressed bars and the bottom bars are arranged in parallel,

[0006] 2. Production process steps

[0007] It includes a long-line pedestal, an outer formwork and an inner formwork, wherein the outer formwork includes a side formwork and an end formwork, and the end formwork is provided with a hole for the prestressed tendons to pass through, wherein the prestressed tendons include a bottom prestressed tendon and an upper prestressed tendon.

[0008] Step 1: Install the outer formwork on the long-line pedestal, pass the prestressed tendons through the preset holes on the end formwork and fix one end of the prestressed tendons on the long-line pedestal, tie the steel bar skeleton inside the outer formwork, tension the prestressed tendons and fix the other end of the prestressed tendons on the long-line pedestal after tensioning is completed;

[0009] Step 2: After pouring concrete to a height of 10-30mm above the bottom prestressed reinforcement and bottom reinforcement, compact the concrete using the inner formwork and fix the inner formwork, then pour concrete into the gap between the inner formwork and the outer formwork. After pouring, wait for the concrete to form. When the concrete compressive strength reaches 70%-80% of the design strength, release the prestressed reinforcement and cut off the excess prestressed reinforcement.

[0010] Step 3: Remove the outer formwork and the inner formwork, and bond the cover plate to the inner edge of the upper opening of the hollow beam body with mortar to form a closed cavity inside the hollow beam body, thus completing the production of the prefabricated prestressed concrete hollow beam.

[0011] The technical problem to be solved by the present invention can be further achieved by the following technical solution: in the above-mentioned prefabricated prestressed concrete hollow beam, the thickness of the cover plate is 10-15 mm.

[0012] The technical problem to be solved by the present invention can be further achieved by the following technical solution: in the above-mentioned prefabricated prestressed concrete hollow beam, the internal angle of the hollow beam body is a chamfer.

[0013] The technical problem to be solved by the present invention can be further achieved by the following technical solution: in the above-mentioned prefabricated prestressed concrete hollow beam, a groove for engaging a cover plate is provided at the top of the hollow beam body.

[0014] The technical problem to be solved by the present invention can be further achieved by the following technical scheme: in the prefabricated prestressed concrete hollow beam described above, the top end of the U-shaped stirrup is higher than the hollow beam body, and the ends of the U-shaped stirrup are provided with hook-shaped steel bars for lifting facing each other.

[0015] Compared with the prior art, the beneficial effects of the present invention are that the cross-section of the hollow beam body is U-shaped, the cover plate is bonded to the inner edge of the upper opening of the hollow beam body to form a closed cavity structure, and bottom prestressed tendons and upper prestressed tendons are arranged in the hollow beam body, which reduces the dead weight of the structure, reduces the amount of steel bars and concrete, and greatly improves the component's resistance to cracking and deformation. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A cross-sectional schematic diagram of the present invention;

[0017] Figure 2 It is a schematic diagram of placing an inner template of the present invention;

[0018] Figure 3 A schematic diagram of pouring completion of the present invention;

[0019] In the figure: 11. Hollow beam body, 12. Steel bar skeleton, 121. U-shaped stirrups, 122. Bottom reinforcement, 123. Upper prestressed reinforcement, 124. Bottom prestressed reinforcement, 125. Sealing stirrups, 13. Cover plate. DETAILED DESCRIPTION

[0020] The specific technical solutions of the present invention are further described below to help those skilled in the art further understand the present invention without limiting the rights thereof.

[0021] Reference Figures 1 to 3 In order to distinguish the prestressed tendons from other non-prestressed tendons, the non-prestressed tendons in the figure are bolded. A prefabricated prestressed concrete hollow beam:

[0022] 1. It comprises a hollow beam body 11, a cover plate 13 and a steel bar skeleton 12 arranged in the hollow beam body, wherein the cross section of the hollow beam body is U-shaped, the cover plate is arranged at the inner edge of the upper opening of the hollow beam body, the cover plate and the hollow beam body cooperate with each other to form a closed cavity structure, the steel bar skeleton comprises a bottom rib 122, an upper prestressed rib 123 and a U-shaped stirrup 121, a plurality of U-shaped stirrups are placed in parallel along the length direction of the hollow beam body, the left and right bottom ribs and the U-shaped stirrups are arranged vertically, the two upper prestressed ribs and the bottom ribs are arranged in parallel, a plurality of bottom prestressed ribs 124 are arranged between the left and right bottom ribs, and the bottom prestressed ribs and the bottom ribs are arranged in parallel;

[0023] 2. Production process steps

[0024] It includes a long-line pedestal, an outer formwork and an inner formwork, wherein the outer formwork includes a side formwork and an end formwork, and the end formwork is provided with a hole for the prestressed tendons to pass through, wherein the prestressed tendons include a bottom prestressed tendon and an upper prestressed tendon.

[0025] Step 1: Install the outer formwork on the long-line pedestal, pass the prestressed tendons through the preset holes on the end formwork and fix one end of the prestressed tendons on the long-line pedestal, tie the steel bar skeleton inside the outer formwork, tension the prestressed tendons and fix the other end of the prestressed tendons on the long-line pedestal after tensioning is completed;

[0026] Step 2: After pouring concrete to a height of 10-30mm above the bottom prestressed reinforcement and bottom reinforcement, compact the concrete using the inner formwork and fix the inner formwork, then pour concrete into the gap between the inner formwork and the outer formwork. After pouring, wait for the concrete to form. When the concrete compressive strength reaches 70%-80% of the design strength, release the prestressed reinforcement and cut off the excess prestressed reinforcement.

[0027] Step 3: Remove the outer formwork and the inner formwork, and bond the cover plate to the inner edge of the upper opening of the hollow beam body with mortar to form a closed cavity inside the hollow beam body, thus completing the production of the prefabricated prestressed concrete hollow beam.

[0028] FRP material can be selected as prestressed tendons. FRP material has high tensile strength, light weight and corrosion resistance. The elastic modulus of FRP tendons is low. Combining it with prestressed technology can give full play to its performance. Compared with traditional steel bar materials, components using FRP tendons as prestressed tendons are environmentally friendly and more corrosion-resistant. They also reduce the self-weight of the structure and reduce the use of steel.

[0029] The upper prestressed tendons balance the prestress of the bottom prestressed tendons to a certain extent. The arrangement of the prestressed tendons at the same time can avoid the excessive prestress at the bottom of the prefabricated prestressed concrete hollow beam, resulting in reverse arching and cracking.

[0030] The bottom end of the inner formwork is provided with a chamfer of 15-25 mm, and the top end of the inner formwork is provided with a top plate for forming a groove. During the pouring process, the bottom corner inside the hollow beam body is chamfered, and the top end of the hollow beam body forms a groove for fitting the cover plate. By chamfering the internal corners of the beam, the stress concentration effect is reduced and concrete cracking is effectively prevented; after removing the outer formwork and the inner formwork, a cover plate with a thickness of 10-15 mm is inserted into the groove at the upper end of the hollow beam body, and the cover plate is bonded with mortar, so that a closed cavity is formed inside the prefabricated prestressed concrete hollow beam, preventing cast-in-place concrete from entering the cavity, reducing the deadweight of the structure, and reducing the amount of concrete used.

[0031] The top of the U-shaped stirrup is higher than the hollow beam body, and the ends of the U-shaped stirrup are bent to form opposite hook-shaped steel bars, which are convenient for lifting during the later construction process; a sealing stirrup 125 that matches the hook-shaped steel bars is arranged between the opposite hook-shaped steel bars on the U-shaped stirrup, and the sealing stirrups can be fixedly connected by steel bars, thereby improving the stability of the steel skeleton structure. When the upper part of the prefabricated prestressed concrete hollow beam is cast in the later stage, the connection between the prefabricated prestressed concrete hollow beam and the upper cast-in-place concrete is strengthened.

[0032] When pouring concrete, use the same batch of concrete to make several test blocks, and cure them under the same conditions as the hollow beam body. Use a machine to press the test block at regular intervals to measure the strength of the test block. When the test block reaches 70%~80% of the design strength, it is considered that the hollow beam body has also reached the design strength of 70%~80%. Release the prestressed tendons, choose a cutting method that causes less disturbance to the hollow beam body, cut off the excess prestressed tendons and place the hollow beam body in the factory for curing, completing the production of prefabricated prestressed concrete hollow beams.

[0033] The production and maintenance of the prefabricated prestressed concrete hollow beams are completed in the factory. Prestressed tendons that meet the engineering requirements are selected. The length of the prestressed tendons can be flexibly adjusted according to actual needs. The prefabricated prestressed concrete hollow beams are produced on a long-line pedestal. The prestressed tendons are tensioned on the long-line pedestal using the pre-tensioning method. Then, the external formwork is installed on the long-line pedestal and concrete is poured. This avoids the complex process of on-site tensioning of prestressed components, effectively shortens the construction period, and reduces the environmental problems caused by manual work. The hollow design and prestressed technology are effectively combined to reduce the dead weight of the structure, reduce the amount of steel bars and concrete used, effectively avoid premature cracks in the concrete structure, and reduce production costs and construction costs.

[0034] Obviously, the described embodiments are only some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Claims

1. A prefabricated prestressed concrete hollow beam, characterized in that: It comprises a hollow beam body, a cover plate and a steel bar skeleton arranged in the hollow beam body, wherein the cross section of the hollow beam body is U-shaped, the cover plate is arranged at the inner edge of the upper opening of the hollow beam body, the cover plate and the hollow beam body cooperate with each other to form a closed cavity structure, the steel bar skeleton comprises bottom bars, upper prestressed bars and U-shaped stirrups, a plurality of U-shaped stirrups are arranged in parallel along the length direction of the hollow beam body, two left and right bottom bars and the U-shaped stirrups are arranged vertically, two upper prestressed bars and the bottom bars are arranged in parallel, a plurality of bottom prestressed bars are arranged between the left and right bottom bars, and the bottom prestressed bars and the bottom bars are arranged in parallel; 2. Production process steps It includes a long-line pedestal, an outer formwork and an inner formwork, wherein the outer formwork includes a side formwork and an end formwork, and the end formwork is provided with a hole for the prestressed tendons to pass through, wherein the prestressed tendons include a bottom prestressed tendon and an upper prestressed tendon. Step 1: Install the outer formwork on the long-line pedestal, pass the prestressed tendons through the preset holes on the end formwork and fix one end of the prestressed tendons on the long-line pedestal, tie the steel bar skeleton inside the outer formwork, tension the prestressed tendons and fix the other end of the prestressed tendons on the long-line pedestal after tensioning is completed; Step 2: After pouring concrete to a height of 10-30mm above the bottom prestressed reinforcement and bottom reinforcement, compact the concrete using the inner formwork and fix the inner formwork, then pour concrete into the gap between the inner formwork and the outer formwork. After pouring, wait for the concrete to form. When the concrete compressive strength reaches 70%-80% of the design strength, release the prestressed reinforcement and cut off the excess prestressed reinforcement. Step 3: Remove the outer formwork and the inner formwork, and bond the cover plate to the inner edge of the upper opening of the hollow beam body with mortar to form a closed cavity inside the hollow beam body, thus completing the production of the prefabricated prestressed concrete hollow beam.

2. The prefabricated prestressed concrete hollow beam according to claim 1, characterized in that: The cover plate has a thickness of 10-15 mm.

3. The prefabricated prestressed concrete hollow beam according to claim 1, characterized in that: The inner corners of the hollow beam body are chamfered.

4. The prefabricated prestressed concrete hollow beam according to claim 1, characterized in that: The top end of the hollow beam body is provided with a groove for engaging the cover plate.

5. The prefabricated prestressed concrete hollow beam according to claim 1, characterized in that: The top end of the U-shaped stirrup is higher than the hollow beam body, and the ends of the U-shaped stirrup are provided with hook-shaped steel bars for hoisting facing each other.

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