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

Abstract

The invention 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] The present invention relates to the technical field of composite beams, and specifically to a pre-tensioned prestressed continuous curved web truss composite beam. Background Art

[0002] Due to its core advantages such as light self-weight, high strength, convenient construction, and high industrialization level, the steel structure system has become a widely adopted structural form in modern architecture. Although traditional solid web steel beams (such as H-beams and I-beams) have mature manufacturing processes, there are significant limitations in their section efficiency and material utilization rate. At the same time, steel structures generally have poor fire resistance. In recent years, the gradually developed truss beams, steel-concrete composite beams, and the application of prestress have effectively improved the bearing efficiency, economy, and fire resistance of beams. In traditional steel frame structures, due to design inertia and construction cost considerations, ordinary steel sections are still commonly used, resulting in redundant steel consumption and high structural self-weight, making it difficult to meet the industry development trends of green buildings and low-carbon construction. The specific disadvantages are as follows: 1. Traditional steel beams adopt solid web structures, resulting in large self-weight and high material consumption. 2. Traditional steel beams are not prestressed, and their 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 bearing capacity and stability, thus leading to a relatively high steel consumption; at the same time, the steel components combined with concrete have better fire resistance. 4. The manufacturing process of the connection nodes between the web members and chord members of traditional steel pipe truss beams is complex, and the degree of production automation is low. 5. In traditional post-tensioned prestressed truss beams, the post-tensioning construction process is usually adopted in the lower chord rods. After tensioning, grouting is carried out or not. During the component manufacturing stage, only the lower chord steel pipes are used to bear the pre-pressure of the prestressing tendons, and the combined effect of steel pipe concrete is not fully utilized, restricting the amount of prestressing tendons. 6. The lower chord of traditional prestressed truss beams mostly adopts the post-tensioning process, with high on-site tensioning costs, far lower efficiency and economy than batch production using the pre-tensioning long-line bench method, and insufficient standardization. Therefore, a pre-tensioned prestressed continuous curved web truss composite beam is provided. Summary of the Invention

[0003] The purpose of the present invention is to address the deficiencies of the prior art and provide a pre-tensioned prestressed continuous curved web truss composite beam to solve the problems raised in the above background art.

[0004] To achieve the above purpose, the present invention provides the following technical solution: A pre-tensioned prestressed continuous curved web truss composite beam, including a composite beam body, the composite beam body includes an upper chord rod, web members, and a lower chord rod, and the web members are arranged between the upper chord rod and the lower chord rod;

[0005] The web members are made of continuously bent steel pipes and filled with cement slurry inside;

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

[0007] The lower chord is composed of two steel pipes. The two horizontally symmetric steel pipes are welded to both sides of the bent web member. Prestressing tendons are arranged inside the steel pipes, and cement slurry is poured to form a composite member; a cast-in-place reinforced concrete floor slab is arranged on 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 technical solution of the present invention, a grouting pipe and an exhaust pipe are welded on the lower chord, and both the grouting pipe and the exhaust pipe are communicated with the lower chord.

[0009] As a preferred technical solution of the present invention, end plates are installed at both ends of the lower chord, and gusset plates are welded at the ends of the web members.

[0010] As a preferred technical solution of the present invention, the web members are made of welded steel pipes or seamless steel pipes with a nominal diameter of DN30 - DN80, and the material is Q235 or Q355.

[0011] As a preferred technical solution of the present invention, the lower chord is made of welded steel pipes or seamless steel pipes with a nominal diameter of DN40 - DN80, and the material is Q235 or Q355.

[0012] As a preferred technical solution of the present invention, the prestressing tendons include steel strands, steel wire ropes or high-strength deformed steel bars; the void between the prestressing tendons and the steel pipes is grouted with slightly expanding cement slurry, and the compressive strength of the cement slurry is 30MPa - 50MPa.

[0013] As a preferred technical solution of the present invention, the prestressing tendons are tensioned on a long-line bench; no anchor is provided at the end of the lower chord, and the tensioning can be carried out after the poured cement slurry reaches 80% of the designed strength.

[0014] As a preferred technical solution of the present invention, the upper chord is made of double-angle equal-leg steel or unequal-leg steel with a specification of L40 to L125, and the material is Q235 or Q355; a sealing plate is welded at the bottom of the double-angle steel or channel steel of the upper chord for bottom sealing. After the floor slab concrete is poured, the void at the bottom of the upper chord is filled with concrete, realizing full contact between the concrete and the steel structure and forming a steel-concrete composite section.

[0015] Compared with the prior art, the beneficial effects of the present invention are:

[0016] 1. By applying prestress technology and applying prestress to the lower chord, the flexural bearing capacity and stiffness of the composite truss beam are significantly improved, and the steel consumption is saved.

[0017] 2. The upper chord adopts a steel-concrete composite section, which 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 adopted to replace the traditional solid web structure. The shear force of the web of the solid web steel beam is reflected as the axial force of the diagonal web members in the truss structure, reducing the requirement of the beam for shear bearing capacity and saving steel consumption.

[0019] 4. The web members are continuously bent by a pipe bender and then filled with cement slurry. On the one hand, the production process is simplified and automated; on the other hand, the structural performance and fire resistance of the composite members are better. This technology effectively avoids the complex manufacturing process of the connection nodes between the traditional steel pipe truss web members and chord members, improves production efficiency and at the same time enhances the quality assurance level of the members.

[0020] 5. By injecting cement slurry into the lower chord, the lower chord steel pipe and the prestressed tendons form bonded prestress, enabling the truss beam to be produced on a long-line bench using the pre-tensioning method. Compared with the traditional manufacturing process of prestressed steel pipe trusses, the production efficiency and standardization degree are significantly improved, and the cost is significantly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is the elevation view of the pre-tensioning prestressed continuously bent web member truss composite beam of the present invention;

[0022] Figure 2 is the cross-sectional view of the pre-tensioning prestressed continuously bent web member truss composite beam of the present invention;

[0023] Figure 3 is the plan layout view of the pre-tensioning prestressed continuously bent web member truss composite beam of the present invention.

[0024] In the figure: 100, composite beam body; 1, upper chord; 2, web member; 3, lower chord; 4, prestressed tendon; 5, sealing plate; 6, gusset plate; 7, grouting pipe; 8, exhaust pipe; 9, end plate; 10, cast-in-place reinforced concrete floor slab. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] The following elaborates on the preferred embodiments of the present invention in conjunction with 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 making a clearer and more definite definition of the protection scope of the present invention.

[0026] Embodiment: Please refer to Figures 1-3 , the present invention provides a technical solution: a pre-tensioning prestressed continuously bent web member truss composite beam, including a composite beam body 100. The composite beam body 100 includes an upper chord 1, web members 2, and a lower chord 3. The web members 2 are arranged 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 slurry inside.

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

[0029] The lower chord 3 consists of two steel pipes. Two horizontally symmetric steel pipes are welded to both sides of the bent web member 2. Prestressing tendons 4 are arranged inside the steel pipes, and cement slurry is poured to form a composite member. A cast-in-place reinforced concrete floor slab 10 is arranged at the top of the upper chord 1, 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 joint structure, a larger width of the upper and lower chords, 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 slurry and concrete not only improves the structural efficiency, but also improves the fire resistance of the components.

[0030] A grouting pipe 7 and an exhaust pipe 8 are welded to the lower chord 3 for grouting and exhausting. Both the grouting pipe 7 and the exhaust pipe 8 are communicated with the lower chord 3. End plates 9 are installed at both ends of the lower chord 3, and a gusset plate 6 is welded to the end of the web member 2.

[0031] The web member 2 is made of welded steel pipe or seamless steel pipe with a nominal diameter of DN30 - DN80, and the material is Q235 or Q355. After the truss is welded, the web member is filled with cement slurry.

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

[0033] The prestressing tendons include steel strands, steel wire ropes or high-strength deformed steel bars. The gap between the prestressing tendons and the steel pipes is grouted with slightly expanding cement slurry, and the compressive strength of the cement slurry is 30MPa - 50MPa. The prestressing tendons are tensioned on a long-line bench, enabling batch production. No anchor is set at the end of the lower chord 3, and the tensioning can be carried out after the poured cement slurry reaches 80% of the design strength. By forming constraints on the cement slurry through the steel pipes, the splitting strength is greatly improved, realizing the bonded self-anchoring of the prestressing tendons.

[0034] The upper chord 1 is made of double-angle equal-leg or unequal-leg angles with a specification of L40 to L125, and the material is Q235 or Q355. A sealing plate 5 is welded to the bottom of the double-angle angles or channels of the upper chord 1 for bottom sealing. After the floor slab concrete is poured, the gap at the bottom of the upper chord is filled with concrete, realizing full contact between the concrete and the steel structure and forming a steel-concrete composite section.

[0035] Working principle: The web member 2 is made by continuously bending a steel pipe and filled with cement slurry inside; the lower chord 3 is welded and connected on both sides of the bent web member by two horizontally symmetric steel pipes, prestressing tendons are arranged inside the steel pipes, and cement slurry is filled to form a composite member; the upper chord 1 is welded and connected on both sides of the bent web member 2 by using section steel, and forms a steel-concrete composite section with the cast-in-place reinforced concrete floor slab. Compared with ordinary trusses, the joint structure of the truss beam formed by this structure is simpler and more reliable, the widths of the upper and lower chords are increased, and the out-of-plane stiffness is greater, which is beneficial to ensuring the out-of-plane stability during the construction and installation stages; the full combination of steel, cement slurry and concrete not only improves the structural efficiency, but also improves the fire resistance of the members.

[0036] Specifically:

[0037] 1. The web members of the truss beam are made by continuously bending the steel pipe with a pipe bender. This method effectively avoids the complex manufacturing process of the connection nodes between the web members and chords of traditional steel trusses. Its structural form improves the out-of-plane stiffness of the truss, making it less likely to experience out-of-plane instability; the manufacturing method of the web members improves the production efficiency and also enhances the quality assurance level of the members. The inside of the web member steel pipe is filled with cement slurry, which can improve its compressive bearing capacity, and at the same time improve the stiffness and stability of the member; the presence of the cement slurry also improves the fire resistance of the member.

[0038] 2. By applying prestress and injecting cement slurry into the lower chord, after the prestress is released, the cement slurry in the lower chord steel pipe is under large compressive stress, which can prevent it from cracking during the normal use stage and participate in the structural force. Therefore, it makes a significant contribution to the tensile stiffness of the lower chord, thereby improving the overall stiffness of the truss beam; therefore, compared with ordinary truss beams, its flexural bearing capacity and stiffness are both significantly improved; compared with steel beams with the same bearing capacity and stiffness, the steel consumption is saved by about 40%; based on the pre-tensioning process on a long-line bench, the on-site tensioning operation is avoided, which has significant economic benefits.

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

[0040] 4. Force-bearing of the composite section: The upper chord and the cast-in-place reinforced concrete floor slab form a composite section, which improves the flexural and shear bearing capacities of the beam and significantly reduces the steel consumption of the upper chord; the web member and the cement slurry form a composite member, which can reduce the steel consumption; the lower chord and the cement slurry and prestressing tendons form a composite member, and the steel consumption of the lower chord is significantly reduced.

[0041] The specific manufacturing steps are as follows:

[0042] 1. According to the total length of the designed web member 2, multiple round steel pipes are welded into a whole pipe, and a continuously bent web member 2 is made by bending with a pipe bender.

[0043] 2. The lower chord member 3 is welded and connected to the side surface of the bent web member 2; a grouting pipe 7 and an exhaust pipe 8 are installed on the lower chord member 3.

[0044] 3. The double-angle steel upper chord member 1 is welded and connected to the side surface of the bent web member 2, and the bottom is sealed by spot welding thin iron sheets.

[0045] 4. The prefabricated gusset plate 6 is welded to the end of the web member 2.

[0046] 5. After the first four steps are completed, the fabricated pipe truss beam is placed on the long-line bench, prestressed steel strands are inserted into the steel pipe of the lower chord member 3, and the end plate 9 is installed.

[0047] 6. The prestressed tendon 4 is tensioned, and slightly expanded cement slurry is injected into the web member 2 and the lower chord member 3 for curing.

[0048] 7. After the cement slurry in the pipes of the web member 2 and the lower chord member 3 reaches 80% of the designed strength, relaxation is carried out, and anti-corrosion and fire protection treatments are carried out on the fabricated prestressed steel pipe truss.

[0049] 8. Hoisting and installation are carried out, and after the construction conditions of the concrete floor slab are met, the floor slab concrete is poured.

[0050] The above embodiments only express the implementation manners of the present invention, and the description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

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

2. The pretensioned prestressed continuous bent web member truss composite beam according to claim 1, wherein: A grouting pipe (7) and an exhaust pipe (8) are welded to the lower chord (3), and both the grouting pipe (7) and the exhaust pipe (8) are communicated with the lower chord (3).

3. The pretensioned prestressed continuous bent web member truss composite beam according to claim 2, wherein: End plates (9) are installed at both ends of the lower chord (3), and gusset plates (6) are welded to the ends of the web members (2).

4. The pretensioned prestressed continuous bent web member truss composite beam according to claim 1, characterized in that: The web members (2) are made of welded steel pipes or seamless steel pipes with a nominal diameter of DN30 to DN80, and the material is Q235 or Q355.

5. The pretensioned prestressed continuous bent web member truss composite beam according to claim 1, wherein: The lower chord (3) is made of welded steel pipes or seamless steel pipes with a nominal diameter of DN40 to DN80, and the material is Q235 or Q355.

6. The pretensioned prestressed continuous bent web member truss composite beam according to claim 1, characterized in that: The prestressing tendons include steel strands, steel wire ropes or high-strength deformed steel bars; The gap between the prestressing tendons and the steel pipes is grouted with slightly expanding cement slurry, and the compressive strength of the cement slurry is 30MPa to 50MPa.

7. The pretensioned prestressed continuous bent web member truss composite beam according to claim 6, wherein: The prestressing tendons are tensioned on a long-line bench; No anchor is provided at the end of the lower chord (3), and the tensioning can be carried out after the poured cement slurry reaches 80% of the design strength.

8. The pretensioned prestressed continuous bent web member truss composite beam according to claim 1, wherein: The upper chord (1) uses double-angle equal-leg or unequal-leg angles, with a specification of L40 to L125, and the material is Q235 or Q355; A sealing plate (5) is welded to the bottom of the double-angle steel or channel steel of the upper chord (1) for bottom sealing. After the floor slab concrete is poured, the gap at the bottom of the upper chord is filled with concrete, realizing full contact between the concrete and the steel structure, and forming a steel-concrete composite section.

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