Pre-tensioning method pre-stress continuous bending web member truss composite beam

Abstract

The utility model relates to the technical field of composite beams, and particularly discloses a pre-tensioning method pre-stress continuous bending web member truss composite beam, which is characterized in that a web member of the composite beam is formed by continuously bending a steel pipe through a pipe bending machine, and cement slurry is injected into the web member; the lower chord member is composed of two grouting steel pipes with prestressed tendons penetrating through the grouting steel pipes. The upper chord and the reinforced concrete floor form a combined section through the double-limb angle steel. The prestressed bent pipe truss composite beam has the remarkable advantages of being high in bearing capacity and rigidity, simple in manufacturing process and the like, compared with a steel beam with the same bearing capacity and rigidity, the steel consumption is reduced by 40%, good economic benefits and social benefits are achieved, and the prestressed bent pipe truss composite beam is particularly suitable for public buildings and industrial buildings with medium and small spans (8-12 m) under the medium-load working condition.

Description

Technical Field

[0001] This utility model relates to the field of composite beam technology, specifically a prestressed composite beam with continuous bending web members using the pre-tensioning method. Background Technology

[0002] Steel structure systems, due to their core advantages such as light weight, high strength, convenient construction, and high degree of industrialization, have become a widely adopted structural form in modern architecture. While traditional solid-web steel beams (H-beams, I-beams, etc.) have mature manufacturing processes, their section efficiency and material utilization are significantly limited. Furthermore, steel structures generally suffer from poor fire resistance. In recent years, truss beams, steel-concrete composite beams, and the application of prestressing have effectively improved the load-bearing efficiency, economy, and fire resistance of beams. In traditional steel frame structures, limited by design inertia and construction cost considerations, ordinary steel components are still commonly used, leading to redundant steel consumption and high structural weight, making it difficult to meet the industry development trends of green building and low-carbon construction. Specific disadvantages include: 1. Traditional steel beams use a solid-web structure, resulting in heavy weight and high material consumption. 2. Traditional steel beams do not apply prestress, and their load-bearing capacity and stiffness are lower than those of prestressed steel beams. 3. Traditional steel beams fail to fully utilize the combined effect of concrete, resulting in relatively low load-bearing capacity and stability, thus leading to higher steel consumption. Simultaneously, steel components combined with concrete exhibit better fire resistance. 4. The fabrication process for the connection nodes between the web members and chord members of traditional steel pipe truss beams is complex, with low automation. 5. Traditional lower chord prestressed truss beams typically employ post-tensioning, with grouting performed or not after tensioning. During component fabrication, only the lower chord steel pipe bears the prestressing force of the prestressing tendons, failing to fully utilize the combined effect of steel-concrete composite and limiting the amount of prestressing tendons used. 6. The post-tensioning process for the lower chord of traditional prestressed truss beams is costly in on-site tensioning, with efficiency and economy far lower than pre-tensioned long-line platform mass production, and insufficient standardization. Therefore, a pre-tensioned prestressed composite truss beam with connected bending web members is proposed. Utility Model Content

[0003] The purpose of this invention is to address the shortcomings of existing technologies by providing a prestressed composite beam with continuous bending web members using the pre-tensioning method, thereby solving the problems mentioned in the background section.

[0004] To achieve the above objectives, this utility model provides the following technical solution: a prestressed continuous bending web truss composite beam using the prestressed pretensioning method, comprising a composite beam body, wherein the composite beam body includes an upper chord, web members, and a lower chord, and the web members are disposed between the upper chord and the lower chord;

[0005] The web member is made of continuously bent steel pipe and filled with cement grout.

[0006] The upper chord is welded to both sides of the bent web member;

[0007] The lower chord consists of two steel pipes, which are horizontally symmetrical and welded to both sides of a bent web member. Prestressed tendons are installed inside the steel pipes, and cement grout is poured in to form a composite member. A cast-in-place reinforced concrete floor slab is installed at the top of the upper chord, and the composite beam body and the cast-in-place reinforced concrete floor slab form a steel-concrete composite section.

[0008] As a preferred embodiment of this utility model, a grouting pipe and an exhaust pipe are welded onto the lower chord, and both the grouting pipe and the exhaust pipe are connected to the lower chord.

[0009] As a preferred embodiment of this utility model, end plates are installed at both ends of the lower chord, and node plates are welded to the ends of the web members.

[0010] As a preferred technical solution of this utility model, the web member is made of welded steel pipe or seamless steel pipe with a nominal diameter of DN30 to DN80, and the material is Q235 or Q355.

[0011] As a preferred technical solution of this utility model, the lower chord is made of welded steel pipe or seamless steel pipe with a nominal diameter of DN40 to DN80, and the material is Q235 or Q355.

[0012] As a preferred technical solution of this utility model, the prestressing tendon includes steel strand, steel wire rope or precision rolled threaded steel; the gap between the prestressing tendon and the steel pipe is filled with micro-expansion cement grout, and the compressive strength of the cement grout is 30MPa to 50MPa.

[0013] As a preferred technical solution of this utility model, the prestressed tendons are tensioned on a long-line pedestal; no anchorage is provided at the end of the lower chord, and the tensioning can only be carried out after the injected cement grout reaches 80% of the design strength.

[0014] As a preferred technical solution of this utility model, the upper chord is made of double-limb equilateral angle steel or unequal angle steel with specifications of L40 to L125 and material of Q235 or Q355; a sealing plate is welded to the bottom of the double-limb angle steel or channel steel of the upper chord to seal the bottom. After the floor slab concrete is poured, the gap at the bottom of the upper chord is filled with concrete, realizing full contact between concrete and steel structure to form steel-concrete composite section.

[0015] Compared with the prior art, the beneficial effects of this utility model are:

[0016] 1. By applying prestressing technology to the lower chord, the bending load capacity and stiffness of the composite truss beam are significantly improved, while saving steel consumption.

[0017] 2. The use of a steel-concrete composite section for the upper chord significantly improves the compressive bearing capacity of the upper chord of the truss beam. Due to the contribution of the concrete floor slab, the shear bearing capacity and overall stability of the truss beam are also significantly improved.

[0018] 3. The truss structure is used instead of the traditional solid web structure. The shear force of the web of the solid web steel beam is manifested as the axial force of the diagonal web members in the truss structure, which reduces the beam's shear bearing capacity requirements and saves steel.

[0019] 4. The web members are continuously bent using a pipe bending machine and then filled with cement grout. This simplifies and automates the production process and results in better structural and fire-resistant performance of the composite components. This technology effectively avoids the complex manufacturing process of connecting web members and chord members in traditional steel pipe trusses, improving production efficiency and enhancing the quality assurance level of the components.

[0020] 5. By injecting cement grout into the lower chord, the lower chord steel pipe and the prestressing tendon form bonded prestress, which enables the truss beam to be produced on a long-line pedestal using the pre-tensioning process. Compared with the traditional prestressed steel pipe truss manufacturing process, this significantly improves production efficiency and standardization, while also significantly reducing costs. Attached Figure Description

[0021] Figure 1 This is an elevation view of the prestressed composite beam with continuous bending web members using the pre-tensioning method of this utility model.

[0022] Figure 2 This is a cross-sectional view of the prestressed continuous bending web truss composite beam of the present invention.

[0023] Figure 3 This is a plan view of the prestressed continuous bending web truss composite beam of the present invention.

[0024] In the figure: 100, composite beam body; 1, top chord; 2, web member; 3, bottom chord; 4, prestressed tendon; 5, end plate; 6, node plate; 7, grouting pipe; 8, vent pipe; 9, end plate; 10, cast-in-place reinforced concrete floor slab. Detailed Implementation

[0025] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more definite definition of the scope of protection of the present invention.

[0026] Example: Please refer to Figure 1-3 This utility model provides a technical solution: a prestressed continuous bending web truss composite beam, including a composite beam body 100, the composite beam body 100 including an upper chord 1, web members 2, and a lower chord 3, with the web members 2 disposed between the upper chord 1 and the lower chord 3;

[0027] The web member 2 is made of continuously bent steel pipe and filled with cement grout.

[0028] The upper chord 1 is welded to both sides of the bent web member 2;

[0029] The lower chord 3 is composed of two steel pipes, which are horizontally symmetrical and welded to both sides of the bent web member 2. Prestressed tendons 4 are installed inside the steel pipes, and cement grout is poured in to form a composite member. The top of the upper chord 1 is provided with a cast-in-place reinforced concrete floor slab 10, and the composite beam body 100 and the cast-in-place reinforced concrete floor slab 10 form a steel-concrete composite section. Compared with ordinary trusses, the truss beam formed by this structure has a simpler and more reliable node structure, a wider upper and lower chord, and greater out-of-plane stiffness, which is conducive to ensuring out-of-plane stability during construction and installation. The full combination of steel, cement grout, and concrete not only improves the structural efficiency but also improves the fire resistance of the components.

[0030] The lower chord 3 is welded with a grouting pipe 7 and an exhaust pipe 8 for grouting and venting. Both the grouting pipe 7 and the exhaust pipe 8 are connected to the lower chord 3. Both ends of the lower chord 3 are equipped with end plates 9, and the ends of the web members 2 are welded with node plates 6.

[0031] The web members 2 are made of welded or seamless steel pipes with a nominal diameter of DN30 to DN80, and the material is Q235 or Q355; after the truss is welded, the web members are filled with cement grout.

[0032] The lower chord 3 is made of welded or seamless steel pipe with a nominal diameter of DN40 to DN80, and the material is Q235 or Q355. The two lower chords are arranged horizontally and symmetrically, and are welded to the two sides of the already bent web members.

[0033] Prestressing tendons include steel strands, steel wire ropes, or precision-rolled threaded steel bars; micro-expansion cement grout is injected into the gap between the prestressing tendons and the steel pipe, and the compressive strength of the cement grout is 30MPa to 50MPa; the prestressing tendons are tensioned on a long-line pedestal, which can achieve mass production; no anchorage is provided at the end of the lower chord 3, and the tension can be released only after the injected cement grout reaches 80% of the design strength. The cement grout is constrained by the steel pipe, which greatly improves its splitting strength and realizes the self-anchoring of the prestressing tendons.

[0034] The top chord 1 is made of double-leg equal or unequal angle steel with specifications from L40 to L125 and material Q235 or Q355. A sealing plate 5 is welded to the bottom of the double-leg angle steel or channel steel of the top chord 1 to seal the bottom. After the floor slab concrete is poured, the gap at the bottom of the top chord is filled with concrete to achieve full contact between the concrete and the steel structure and form a steel-concrete composite section.

[0035] Working principle: The web member 2 is made of continuously bent steel pipes and filled with cement grout; the lower chord member 3 is connected to the two sides of the bent web member by welding two horizontally symmetrical steel pipes, with prestressed tendons inside the steel pipes, and cement grout is poured in to form a composite member; the upper chord member 1 is made of steel sections and welded to the two sides of the bent web member 2, forming a steel-concrete composite section with the cast-in-place reinforced concrete floor slab. Compared with ordinary trusses, the truss beam formed by this structure has a simpler and more reliable node structure, a wider upper and lower chord, and greater out-of-plane stiffness, which is beneficial to ensuring out-of-plane stability during construction and installation; the full combination of steel, cement grout, and concrete not only improves structural efficiency but also enhances the fire resistance of the components.

[0036] Specifically:

[0037] 1. The web members of the truss beam are manufactured by continuously bending steel pipes using a pipe bending machine. This method effectively avoids the complex manufacturing process of connecting web members and chords in traditional steel trusses. Its structural form improves the out-of-plane stiffness of the truss, making it less prone to out-of-plane instability. The manufacturing method of the web members increases production efficiency and also enhances the quality assurance level of the components. The internal filling of the web member steel pipes with cement grout improves their compressive bearing capacity, while also increasing the stiffness and stability of the components. The presence of cement grout also improves the fire resistance of the members.

[0038] 2. By applying prestress and injecting cement grout into the lower chord, the cement grout inside the lower chord steel pipe is subjected to greater compressive stress after the prestress is released, preventing it from cracking during normal use and allowing it to participate in the structural stress. Therefore, it significantly contributes to the tensile stiffness of the lower chord, thereby improving the overall stiffness of the truss beam. As a result, compared with ordinary truss beams, its bending load-bearing capacity and stiffness are significantly improved. Compared with steel beams of the same load-bearing capacity and stiffness, it saves about 40% of steel consumption. Based on the pre-tensioning production process using a long-line platform, it avoids on-site tensioning operations, resulting in significant economic benefits.

[0039] 3. By injecting cement grout into the lower chord, bonded prestressing between the lower chord steel pipe and the prestressing tendons is achieved. The truss beam described in this invention patent can be mass-produced on a pre-tensioned long-line pedestal. Compared with the traditional post-tensioned prestressed steel pipe truss manufacturing process, the components do not require working anchors, and the production efficiency, material utilization rate and standardization are significantly improved.

[0040] 4. Composite section stress: The top chord forms a composite section with the cast-in-place reinforced concrete floor slab, which improves the bending and shear bearing capacity of the beam and significantly reduces the amount of steel used in the top chord; the web members form a composite component with the cement grout, which can reduce the amount of steel used; the bottom chord forms a composite component with the cement grout and prestressing tendons, which significantly reduces the amount of steel used in the bottom chord.

[0041] The specific production steps are as follows:

[0042] 1. According to the designed total length of the web member 2, multiple round steel pipes are welded into a single pipe, and then bent into a continuously curved web member 2 by a pipe bending machine.

[0043] 2. Weld the lower chord 3 to the side of the bent web member 2; install the grouting pipe 7 and the vent pipe 8 on the lower chord 3.

[0044] 3. Weld the upper chord 1 of the double-limb angle steel to the side of the bent web member 2, and spot weld a thin sheet of iron to the bottom for sealing.

[0045] 4. Weld the prefabricated node plate 6 to the end of the web member 2.

[0046] 5. After the first four steps are completed, place the fabricated tubular truss beam on the long-line platform, insert prestressed steel strands into the steel pipe of the lower chord 3, and install the end plate 9.

[0047] 6. Tension the prestressing tendons 4, inject micro-expansion cement grout into the web members 2 and the lower chord members 3, and then cure.

[0048] 7. After the cement grout inside the pipes of web member 2 and lower chord member 3 reaches 80% of the design strength, the tension is released, and the completed prestressed steel pipe truss is treated with anti-corrosion and fireproofing.

[0049] 8. After hoisting and installation to meet the construction conditions for the concrete floor slab, pour the concrete for the floor slab.

[0050] The above embodiments merely illustrate the implementation of this utility model, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the utility model patent. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of this utility model, and these all fall within the protection scope of this utility model.

Claims

1. A pre-tensioned prestressed continuous haunch girder composite beam, comprising a composite beam body (100), characterized in that: The composite beam body (100) includes an upper chord (1), a web member (2), and a lower chord (3), with the web member (2) disposed between the upper chord (1) and the lower chord (3); The web member (2) is made of continuously bent steel pipe and filled with cement grout inside; The upper chord (1) is welded to both sides of the bent web member (2); The lower chord (3) is composed of two steel pipes. The two horizontally symmetrical steel pipes are welded to both sides of the bent web member (2). The steel pipes are provided with prestressed tendons (4) and cement grout is poured to form a composite member. The top of the upper chord (1) is provided with a cast-in-place reinforced concrete floor slab (10). The composite beam body (100) and the cast-in-place reinforced concrete floor slab (10) form a steel-concrete composite section.

2. The precast prestressed hybrid girder according to claim 1, wherein: A grouting pipe (7) and an exhaust pipe (8) are welded onto the lower chord (3), and both the grouting pipe (7) and the exhaust pipe (8) are connected to the lower chord (3).

3. The precast prestressed hybrid girder of claim 2, wherein: Both ends of the lower chord (3) are equipped with end plates (9), and the ends of the web members (2) are welded with node plates (6).

4. The precast prestressed hybrid girder of claim 1, wherein: The web member (2) is made of welded steel pipe or seamless steel pipe with a nominal diameter of DN30 to DN80, and the material is Q235 or Q355.

5. The precast prestressed hybrid girder of claim 1, wherein: The lower chord (3) is made of welded steel pipe or seamless steel pipe with a nominal diameter of DN40 to DN80, and the material is Q235 or Q355.

6. The precast prestressed hybrid girder of claim 1, wherein: The prestressing tendons include steel strands, steel wire ropes, or precision-rolled threaded steel bars; micro-expansion cement grout is injected into the gap between the prestressing tendons and the steel pipe, and the compressive strength of the cement grout is 30MPa to 50MPa.

7. The prestressed composite beam with bent web members according to claim 6, characterized in that: The prestressed tendons are tensioned on a long-line platform; no anchorage is provided at the end of the lower chord (3), and the tensioning can only be carried out after the cement grout reaches 80% of the design strength.

8. The precast prestressed hybrid beam according to claim 1, wherein: The upper chord (1) is made of double-limb equilateral angle steel or unequal-limb angle steel with specifications of L40 to L125 and material of Q235 or Q355. A sealing plate (5) is welded to the bottom of the double-limb angle steel or channel steel of the upper chord (1) to seal the bottom. After the floor slab concrete is poured, the gap at the bottom of the upper chord is filled with concrete to achieve full contact between the concrete and the steel structure and form a steel-concrete composite section.

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