Construction method of complex curved surface super-long span ultra-high performance concrete roof truss

Abstract

The application provides a construction method of a complex curved surface super-long span ultra-high performance concrete roof truss, comprising the following steps: providing a curved surface supporting formwork to reduce the contact area of a bottom formwork and a side formwork; before pouring, the roof truss is segmented along the axial direction, the length of each segment is controlled to be 3-5 m, and a temporary baffle is arranged at the segmented position; UHPC is used to pour each pre-segmented segment area; the interval time for pouring adjacent two segments is controlled to be within 20 min, the temporary baffle is removed after the pouring of the adjacent two segments is completed, and the UHPC overlapping position of the two segments is sprayed and humidified, and the UHPC of the adjacent two segments is fully mixed into an integral whole through steel bar insertion and tamping; when the UHPC reaches initial setting, the UHPC is sprayed and humidified and secondarily troweled, and after the UHPC reaches final setting, the UHPC is maintained by water storage under a film; after the pouring is completed, the curved surface supporting formwork is removed, a steam curing shed is covered, and steam curing is performed to obtain a complex curved surface super-long span UHPC roof truss. The construction method provided by the application can prevent the generation of shrinkage cracks and cold joints, the difficulty of form removal is reduced by optimizing the structure of the supporting formwork, and the construction efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of concrete roof truss fabrication technology, specifically to a construction method for a complex curved surface ultra-long span ultra-high performance concrete roof truss. Background Technology

[0002] The span of reinforced concrete roof trusses is generally 15–24m, while that of prestressed concrete roof trusses is generally 18–36m. When the span exceeds 36m, the cross-sectional dimensions of the prestressed concrete roof truss increase, as does its self-weight, which greatly complicates the hoisting and installation process. To facilitate production, the cross-section of the roof truss is generally rectangular, and its shape is relatively simple.

[0003] Ultra-high performance concrete (UHPC), with its extremely high strength and excellent flowability, makes it possible to construct roof trusses with ultra-long spans and complex curved shapes. The cementitious material content of UHPC typically exceeds 1000 kg / m². 3 UHPC exhibits intense hydration reactions, resulting in significantly greater plastic and chemical shrinkage than conventional concrete. This makes it highly susceptible to shrinkage cracks when casting long, slender components. When casting ultra-long UHPC components, the UHPC material must possess self-compacting properties. UHPC readily flows to distant locations, and the thin layers that have flowed there have a very short initial setting time, making them prone to cold joints. Furthermore, when casting roof trusses with complex curved surfaces, a large portion of the side formwork extends beneath the concrete (e.g., ...). Figure 1 As shown in the figure, the contact area between the side formwork and the bottom formwork is increased. Under the gravity of the concrete poured above, the friction between the side formwork and the bottom formwork increases significantly during demolding, making formwork removal difficult. When using tools such as hammers and crowbars to remove the formwork forcefully, the formwork is easily damaged or deformed, which greatly increases the cost of the formwork, brings difficulties to the pouring production, and reduces production efficiency.

[0004] Therefore, the purpose of this invention is to provide a casting process for a complex curved surface ultra-long span UHPC roof truss. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a construction method for ultra-long span ultra-high performance concrete roof trusses with complex curved surfaces, which can prevent the generation of shrinkage cracks and cold joints. By optimizing the structure of the support formwork, the difficulty of demolding is reduced and the construction efficiency is improved.

[0006] The technical solution of the present invention is as follows:

[0007] A construction method for a complex curved surface ultra-long span ultra-high performance concrete roof truss includes the following steps:

[0008] Step S1: Provide and install the curved support template; the curved support template includes a bottom mold, a first side mold and a second side mold supported on the bottom mold and with an arc-shaped inner surface. The bottom mold includes a first bottom mold, a second bottom mold and a third bottom mold arranged in segments at intervals. The first side mold is suspended above the first bottom mold and the second bottom mold, and the second side mold is suspended above the second bottom mold and the third bottom mold. The contact widths of the first side mold with the first bottom mold and the second bottom mold in the radial direction of the roof truss are respectively 'a', and the contact widths of the second side mold with the second bottom mold and the third bottom mold in the radial direction of the roof truss are respectively 'b'. a and b satisfy the following conditions:

[0009] a=2.5~20%*L, b=2.5~20%*L;

[0010] Where L represents the theoretical contact width between the bottom mold and the side mold;

[0011] Step S2: Before pouring, the roof truss is divided into sections along the axial direction, with each section being 3-5m in length, and temporary baffles are set at the section divisions.

[0012] Step S3: Use UHPC to pour each pre-divided segment area in sections. After each segment is poured, spray the surface immediately and cover it with a curing film. The interval between pouring two adjacent segments should be controlled within 20 minutes. After pouring two adjacent segments, remove the temporary baffle and spray moisture at the overlap of the UHPC of the two segments. Use steel bars to tamp the mixture to ensure that the UHPC of the two adjacent segments are fully mixed into a whole.

[0013] Step S4: When the UHPC reaches initial setting, remove the curing membrane, spray humidification and smear and press a second time. After smearing and pressing, cover the curing membrane in time, and carry out water storage curing under the membrane after the UHPC reaches final setting.

[0014] Step S5: 12 hours after the pouring is completed, remove the curved support template, cover the steam curing shed, and carry out steam curing. The temperature is raised to 90±5℃ at a rate not exceeding 12℃ / h and kept constant for 48 hours. Then, the temperature is lowered to the ambient temperature at a rate not exceeding 15℃ / h to obtain a complex curved ultra-long span UHPC roof truss.

[0015] Furthermore, a = 5~10%*L, b = 5~10%*L.

[0016] Furthermore, the curved support template also includes a first diagonal brace that is connected to the first bottom mold and the first side mold at both ends, and a second diagonal brace that is connected to the third bottom mold and the second side mold at both ends.

[0017] Furthermore, the inclination angles of the first and second diagonal braces are 45-60°.

[0018] Furthermore, in step S3, when pouring each pre-divided segment area in sections, the outer area is poured first, followed by the inner area.

[0019] Furthermore, the span of the complex curved ultra-long span UHPC roof truss is greater than 36m.

[0020] Compared with existing technologies, the construction method for complex curved surface ultra-long span ultra-high performance concrete roof trusses provided by this invention has the following advantages:

[0021] The construction method for complex curved ultra-long span ultra-high performance concrete roof trusses provided by this invention optimizes the structure of the curved support formwork, allowing the side formwork to be erected in mid-air. Simultaneously, it employs a segmented continuous pouring process, combined with secondary troweling, under-membrane water curing, and timely steam curing, solving problems such as shrinkage cracks and cold joints that are common in the pouring technology of complex curved ultra-long span UHPC roof trusses. Furthermore, the new curved support formwork structure also solves problems such as difficult demolding and easy damage or deformation of the formwork, reducing formwork costs and improving construction efficiency. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram illustrating the use of conventional templates in existing technologies;

[0024] Figure 2 This is a schematic diagram of the curved surface support template of the present invention in use. Detailed Implementation

[0025] To enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention, and to make the above-mentioned objectives, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be further described below.

[0026] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0027] This invention first provides a roof support template for fabricating complex curved roof trusses; please refer to [link / reference]. Figure 2 This is a schematic diagram of the curved support template of the present invention in use. The curved support template includes a bottom mold 1 and a side mold 2 supported on the bottom mold 1. The inner sidewall of the side mold 2 is arc-shaped. UHPC is poured in the area enclosed by the bottom mold and the side mold to form a curved roof truss.

[0028] In the existing curved support formwork, the bottom surface of the side formwork is in complete contact with the bottom formwork during installation. Since the inner wall of the side formwork is arc-shaped, that is, part of the bottom of the side formwork is located below the UHPC, the friction between the side formwork and the bottom formwork is increased under the gravity of the UHPC, making demolding difficult and potentially damaging the roof truss structure during demolding.

[0029] To address the shortcomings of existing curved support formwork, this invention optimizes the structure of the bottom formwork and the installation methods of the bottom and side forms, reducing the contact area between the side and bottom forms, thereby reducing the friction between them. This not only facilitates demolding but also improves production efficiency and reduces damage to the formwork and the UHPC roof truss structure.

[0030] Specifically, the bottom formwork 1 includes a first bottom formwork 11, a second bottom formwork 12, and a third bottom formwork 13, which are arranged in segments at intervals. That is, the bottom formwork 1 is divided into three segments in the radial direction of the roof truss, and the three segments are discontinuous.

[0031] The side formwork 2 includes a first side formwork 21 and a second side formwork 22 arranged at relative intervals. The inner surfaces of the first side formwork 21 and the second side formwork 22 are arc-shaped. During installation, the first side formwork 21 is suspended above the first bottom formwork 11 and the second bottom formwork 12, and the second side formwork 22 is suspended above the second bottom formwork 12 and the third bottom formwork 13. That is, the left and right ends of the first side formwork 21 overlap with the first bottom formwork 11 and the second bottom formwork 12, respectively, and the left and right ends of the second side formwork 22 overlap with the second bottom formwork 12 and the third bottom formwork 13, respectively. Furthermore, the contact widths of the first side formwork 21 with the first bottom formwork 11 and the second bottom formwork 12 in the radial direction of the roof truss are 'a' and 'b', respectively. a and b satisfy the following conditions:

[0032] a=2.5~20%*L, b=2.5~20%*L;

[0033] Where L represents the theoretical contact width between the bottom mold and the side mold.

[0034] Experiments revealed that when a < 2.5% * L or b < 2.5% * L, instability is easily caused due to the small contact area between the side mold and the bottom mold; when a > 10% * L or b > 10% * L, demolding becomes difficult due to the excessively large contact area between the side mold and the bottom mold. Therefore, preferably, a = 5 ~ 10% * L and b = 5 ~ 10% * L.

[0035] In practical applications, to maintain the stability of the bottom mold and side molds, it is preferable to stabilize the structure by setting diagonal braces 3. Specifically, the curved support formwork 100 also includes a first diagonal brace 31 connected at both ends to the first bottom mold 11 and the first side mold 21 respectively, and a second diagonal brace 32 connected at both ends to the third bottom mold 13 and the second side mold 22 respectively. The inclination angle of the first diagonal brace 31 and the second diagonal brace 32 is 45-60°, making the structure more stable.

[0036] The construction method of the complex curved surface ultra-long span ultra-high performance concrete roof truss of the present invention, using the aforementioned curved surface support template, includes the following steps:

[0037] Step S1: Install curved surface support template;

[0038] Step S2: Before pouring, the roof truss is divided into sections along the axial direction, with each section being 3-5m long. Temporary baffles are set at the section divisions to ensure that the poured UHPC does not flow far away and to prevent cold joints from appearing.

[0039] Step S3: Use UHPC to pour each pre-divided segment area in sections, that is, pour the outer area first, then pour the inner area. After each segment is poured, spray the surface immediately and cover it with a curing film. The interval between pouring two adjacent segments is controlled within 20 minutes. After the two adjacent segments are poured, remove the temporary baffle and spray the overlap of the UHPC of the two segments to increase humidity. Use steel bars to tamp the mixture to ensure that the UHPC of the two adjacent segments are fully mixed into a whole, so as to achieve the purpose of continuous pouring.

[0040] Step S4: When the UHPC reaches initial setting, remove the curing membrane, spray humidification and smear and press a second time. After smearing and pressing, cover the curing membrane in time, and carry out water storage curing under the membrane after the UHPC reaches final setting.

[0041] During this process, a second troweling is performed during initial setting to eliminate the plastic shrinkage generated by the early hydration reaction of UHPC, reducing the risk of cracking; after final setting, water storage and curing under the membrane are carried out to ensure that UHPC retains water and reduces the risk of shrinkage cracking.

[0042] Step S5: 12 hours after the pouring is completed, remove the curved support template, cover the steam curing shed, and carry out steam curing. The temperature is raised to 90±5℃ at a rate not exceeding 12℃ / h and kept constant for 48 hours. Then, the temperature is lowered to the ambient temperature at a rate not exceeding 15℃ / h to obtain a complex curved ultra-long span UHPC roof truss.

[0043] Because of the use of the new curved support formwork, which is easy to dismantle, the dismantling time is shortened. Steam curing can be carried out immediately after dismantling, which can quickly improve the strength of UHPC and further reduce the later shrinkage of UHPC, thus reducing the risk of component cracking. In addition, the use of steam curing shortens the curing time and improves construction efficiency.

[0044] In summary, the construction method for complex curved ultra-long span ultra-high performance concrete roof trusses provided by this invention optimizes the structure of the curved support formwork, allowing the side formwork to be erected in mid-air. Simultaneously, it employs a segmented continuous pouring process, combined with secondary troweling, under-membrane water curing, and timely steam curing, solving problems such as shrinkage cracks and cold joints that are common in the pouring technology of complex curved ultra-long span UHPC roof trusses. Furthermore, the new curved support formwork structure also solves problems such as difficult demolding and easy damage or deformation of the formwork, reducing formwork costs and improving construction efficiency.

[0045] The construction method for complex curved high-performance concrete roof trusses provided by this invention can be used for the construction of roof trusses with ultra-long spans, with a span greater than 36m.

[0046] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations made to these embodiments without departing from the principles and spirit of the present invention still fall within the protection scope of the present invention.

Claims

1. A construction method for a complex curved surface ultra-long span ultra-high performance concrete roof truss, characterized in that, Includes the following steps: Step S1: Provide and install the curved support template; the curved support template includes a bottom formwork, a first side formwork and a second side formwork supported on the bottom formwork and having an arc-shaped inner surface. The bottom formwork includes a first bottom formwork, a second bottom formwork, and a third bottom formwork arranged in segments along the radial direction of the roof truss. The first side formwork is suspended above the first and second bottom formworks, and the second side formwork is suspended above the second and third bottom formworks. The contact widths of the first side formwork with the first and second bottom formworks in the radial direction of the roof truss are respectively 'a', and the contact widths of the second side formwork with the second and third bottom formworks in the radial direction of the roof truss are respectively 'b'. a and b satisfy the following conditions: a=(5~10)%*L, b=(5~10)%*L; Where L represents the theoretical contact width between the bottom mold and the side mold; Step S2: Before pouring, the roof truss is divided into sections along the axial direction, with each section being 3-5m in length, and temporary baffles are set at the section divisions. Step S3: Use UHPC to pour each pre-divided segment area in sections. After each segment is poured, spray the surface immediately and cover it with a curing film. The interval between pouring two adjacent segments should be controlled within 20 minutes. After pouring two adjacent segments, remove the temporary baffle and spray moisture at the overlap of the UHPC of the two segments. Use steel bars to tamp the mixture to ensure that the UHPC of the two adjacent segments are fully mixed into a whole. Step S4: When the UHPC reaches initial setting, remove the curing membrane, spray humidification and smear and press a second time. After smearing and pressing, cover the curing membrane in time, and carry out water storage curing under the membrane after the UHPC reaches final setting. Step S5: 12 hours after the pouring is completed, remove the curved support template, cover the steam curing shed, and carry out steam curing. The temperature is raised to 90±5℃ at a rate not exceeding 12℃ / h and kept constant for 48 hours. Then, the temperature is lowered to the ambient temperature at a rate not exceeding 15℃ / h to obtain a complex curved ultra-long span UHPC roof truss.

2. The construction method for complex curved surface ultra-long span ultra-high performance concrete roof trusses according to claim 1, characterized in that, The curved support template also includes a first diagonal brace that is connected to the first bottom mold and the first side mold at both ends, and a second diagonal brace that is connected to the third bottom mold and the second side mold at both ends.

3. The construction method for complex curved surface ultra-long span ultra-high performance concrete roof trusses according to claim 2, characterized in that, The inclination angle of the first and second diagonal braces is 45-60°.

4. The construction method for complex curved surface ultra-long span ultra-high performance concrete roof trusses according to claim 1, characterized in that, In step S3, when pouring each pre-divided segment area in sections, the outer area is poured first, followed by the inner area.

5. The construction method for complex curved surface ultra-long span ultra-high performance concrete roof trusses according to any one of claims 1-4, characterized in that, The span of the complex curved surface ultra-long span UHPC roof truss is greater than 36m.

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