Assembled round steel core mold

Abstract

The present application relates to the field of engineering, disclose a kind of assembled round steel core mould, including at least one straight section formwork unit and / or at least one curved section formwork unit, the straight section formwork unit is enclosed by multiple straight section formwork pieces along the wedge-shaped arc surface into cylindrical, the curved section formwork unit is enclosed by multiple curved section formwork pieces into arc pipe, adjacent formwork piece and adjacent formwork unit are detachably connected by detachable connecting piece.The beneficial effects of the present application are that under the premise of guaranteeing structural strength and anti-floating safety, the steel mould is quickly disassembled and efficiently circulates in narrow space.

Description

Technical Field

[0001] This invention relates to the technical field of engineering, and specifically to an assembled circular steel core mold. Background Technology

[0002] Nuclear power plants contain numerous pipe racks, trenches, and Balance of Plant (BOP) sub-items, among which circular cross-section concrete structures are a common form. These structures are typically constructed using cast-in-place concrete, and the choice of formwork system directly impacts construction efficiency and project quality. Currently, traditional construction methods often use bent wooden formwork as circular inner molds, which offers advantages such as readily available materials and flexible on-site processing. In recent years, some projects have experimented with using steel inner molds to improve formwork rigidity and reuse rates. However, due to the unique structural form of circular inner molds, the installation and dismantling of steel molds often requires considerable operating space, while the internal spaces of nuclear power plant pipe racks and trenches are typically quite narrow, posing a challenge to the application of steel molds.

[0003] In existing technologies, the bending of wooden formwork suffers from problems such as complex reinforcement methods, difficult dismantling, and low turnover rate of curved formwork, often resulting in it being scrapped after a single use, leading to high construction costs and significant resource waste. While traditional steel inner formwork offers advantages such as good rigidity and high turnover rate, it is mostly an integral or simply segmented structure, making installation and dismantling extremely inconvenient in confined spaces. It typically requires ample operating space or reliance on large machinery, and its heavy design to meet strength requirements further exacerbates the difficulty of installation and dismantling. Therefore, how to achieve rapid installation, dismantling, and efficient turnover of steel core formwork in confined spaces while ensuring sufficient structural strength to resist concrete lateral pressure and meeting anti-buoyancy safety requirements has become a pressing technical problem to be solved in this field. Summary of the Invention

[0004] To address the aforementioned technical issues, the aim is to provide a modular circular steel core mold that, while ensuring structural strength and anti-buoyancy safety, enables rapid disassembly and efficient turnover of the steel mold within a confined space.

[0005] This invention is achieved through the following technical solution:

[0006] An assembled circular steel core mold includes at least one straight section template unit and / or at least one curved section template unit. The straight section template unit is formed into a cylindrical shape by multiple straight section template pieces with wedge-shaped arc surfaces along the axial direction. The curved section template unit is formed into an arc-shaped tube by multiple curved section template pieces. Adjacent template pieces and adjacent template units are detachably connected by detachable connectors.

[0007] The beneficial effects of this invention are that, due to the segmented structure that divides the steel core mold into straight section template units and curved section template units, and the fact that the straight section template unit is composed of multiple straight section template pieces with wedge-shaped arc surfaces along the axial direction to form a cylindrical shape, and the curved section template unit is composed of multiple curved section template pieces to form an arc-shaped tube, the entire steel core mold can be transported into narrow pipe racks or trenches as smaller sheet components for on-site assembly. This overcomes the problem that traditional integral or simple segmented steel molds cannot be installed and disassembled in confined spaces due to the excessive size of the components. Simultaneously, by using adjacent template pieces… The formwork is detachably connected to each other and to adjacent formwork units, allowing each formwork component to be removed sequentially in reverse order after pouring. This avoids the low turnover rate caused by the destructive removal of wooden formwork and enables the rapid disassembly and efficient turnover of steel formwork in narrow spaces. Furthermore, after each formwork component is connected to form an integral cylindrical structure, the rigidity of the cylinder itself can effectively resist the lateral pressure of the concrete. Thus, while ensuring structural strength and anti-buoyancy safety, it solves the technical contradiction that the heavy design of traditional steel formwork further exacerbates the difficulty of installation and disassembly.

[0008] In some embodiments, the straight section formwork unit is formed by four straight section formwork pieces, each of which includes a steel plate and a back rib steel plate fixed to the outer surface of the steel plate. By employing a structure in which the straight section formwork unit is formed by four equal straight section formwork pieces, and each straight section formwork piece includes a steel plate and a back rib steel plate fixed to the outer surface of the steel plate, the straight section formwork unit achieves four-part modularization while significantly enhancing the bending stiffness of each formwork piece through the back rib steel plate. This effectively reduces the size and weight of a single formwork piece while ensuring the overall structural strength is sufficient to resist the lateral pressure of concrete. This facilitates manual handling and assembly in narrow pipe gallery spaces, solving the problem of traditional steel formwork being difficult to install and dismantle due to excessively large components.

[0009] In some embodiments, sealing gaskets are provided at the joints between adjacent straight template sections and at the joints between adjacent template units. Because of this structure, sealing gaskets are used at the joints between adjacent straight template sections and at the joints between adjacent template units, each joint is effectively sealed after template assembly, preventing grout leakage from the joints during concrete pouring. This ensures the quality of concrete forming and the flatness of the template's inner wall. Simultaneously, the elastic cushioning effect of the sealing gaskets facilitates the smooth separation of template sections during subsequent dismantling, indirectly improving installation and dismantling efficiency and the number of times the template can be reused.

[0010] In some embodiments, the sealing gasket includes a straight strip rubber gasket disposed at the joint between the straight template sections and a circular rubber gasket disposed at the joint between each template unit. Because the sealing gasket comprises a straight strip rubber gasket disposed at the joint between the straight template sections and a circular rubber gasket disposed at the joint between each template unit, rubber gaskets of appropriate shapes are used for different joint types (linear joints between sections and annular joints between units), achieving a more precise and reliable sealing effect. This prevents grout leakage from causing adhesion during template disassembly and compensates for assembly errors through the elastic deformation of the rubber material, further ensuring that the template maintains good sealing and smooth disassembly / reassembly even after multiple reuses.

[0011] In some embodiments, the straight and / or curved template sections are provided with back rib steel plates, the detachable connectors are bolts, and corresponding connection holes for the bolts to pass through are provided on the back rib steel plates. By using back rib steel plates on the straight and / or curved template sections, and setting bolts as the detachable connectors with connection holes on the back rib steel plates for the bolts to pass through, the bolt connection force acts directly on the high-rigidity back rib steel plates rather than the thin-walled steel plates themselves. This avoids local deformation of the thin-walled steel plates at the connection points and enables rapid fastening and disassembly between template sections and template units. Therefore, while ensuring connection reliability, it significantly shortens the installation and disassembly time, meeting the construction needs for efficient turnover in confined spaces.

[0012] In some embodiments, the bend template unit includes two interlocking bend steel core mold pieces, A and B, which are joined together along the web-back direction of the bend. Because the bend template unit comprises two interlocking bend steel core mold pieces, A and B, with A and B joined along the web-back direction of the bend, the bend template unit is structurally divided into two large sections. This preserves the integrity of the overall arc of the bend while achieving segmentation of the bend template, thus solving the problem that traditional bend steel molds, being integrally formed, cannot be removed from narrow spaces. This provides a structural basis for the rapid installation and dismantling of bend templates at the bends of pipe racks.

[0013] In some embodiments, the back and front dividing seams of the curved section template unit extend axially, while the waistline dividing seam is inclined relative to the axial direction, with one end of the waistline dividing seam biased towards the abdomen and the other end biased towards the back. Because of this structure, the demolding path of the curved section template is optimized into a guiding oblique separation method, avoiding the jamming phenomenon caused by the self-locking effect of the curved surface during traditional axial straight seam division. This achieves smooth removal of the curved steel core mold after casting, significantly reducing the difficulty and time required for demolding the curved section.

[0014] In some embodiments, one end of the waistline dividing joint is offset 10mm towards the abdomen and the other end is offset 10mm towards the back. Because of this precise offset of 10mm towards the abdomen and 10mm towards the back, the oblique dividing joint of the curved formwork has defined geometric parameters. Finite element analysis and practical verification have shown that this 10mm offset is sufficient to eliminate the self-locking effect of the curved surface, while preventing excessive offset from causing misalignment and deformation of the formwork under the lateral pressure of concrete. This achieves optimal design while ensuring a balance between smooth demolding and forming accuracy.

[0015] In some embodiments, the outer surfaces of the straight and / or curved template sections are uniformly provided with circumferential and axial stiffening ribs. The spacing between the circumferential stiffening ribs is 300mm, and the axial stiffening ribs include four first stiffening ribs with a thickness of 6mm and four second stiffening ribs with a thickness of 12mm. By employing a structure in which circumferential and axial stiffening ribs are uniformly distributed on the outer surfaces of the straight and / or curved template sections, the spacing between the circumferential stiffening ribs is 300mm, and the axial stiffening ribs include four first stiffening ribs with a thickness of 6mm and four second stiffening ribs with a thickness of 12mm, the stiffening rib system optimized through finite element calculation achieves precise material allocation while ensuring the overall stiffness of the template meets the requirements of concrete lateral pressure. 12mm stiffening ribs are used in areas with higher stress, and 6mm stiffening ribs are used in areas with lower stress. This reduces the self-weight of the template while avoiding material redundancy caused by uniformly sized stiffening ribs in traditional steel molds, further improving the ease of handling and dismantling the template in confined spaces.

[0016] In some embodiments, the straight section formwork unit and / or curved section formwork unit are provided with an anti-buoyancy anchoring structure. The anti-buoyancy anchoring structure includes arc-shaped rings spaced apart along the axial direction of the formwork unit. The arc-shaped rings are welded to pre-embedded inverted U-shaped anchor bars, and each arc-shaped ring is provided with two anchor cables. By using an anti-buoyancy anchoring structure on the straight section formwork unit and / or curved section formwork unit, which includes arc-shaped rings spaced apart along the axial direction of the formwork unit, arc-shaped rings welded to pre-embedded inverted U-shaped anchor bars, and two anchor cables provided for each arc-shaped ring, the enormous buoyancy generated by the steel core mold during concrete pouring is effectively transferred to the concrete foundation through the welded connection between the arc-shaped rings and the pre-embedded anchor bars. This achieves built-in anti-buoyancy, eliminating the need for complex external counterweights or support systems on the formwork. Thus, while ensuring anti-buoyancy safety, it maintains the cleanliness of the external space of the formwork and the convenience of installation and dismantling operations, resolving the contradiction between traditional anti-buoyancy measures and construction in confined spaces.

[0017] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0018] 1. The straight section formwork unit is composed of four equal straight section formwork pieces, and each straight section formwork piece includes a steel plate and a back rib steel plate fixed to the outer surface of the steel plate. This allows the straight section formwork unit to achieve four-piece modularization, while the back rib steel plate significantly enhances the bending stiffness of each formwork piece. Thus, while ensuring that the overall structural strength is sufficient to resist the lateral pressure of concrete, the size and weight of a single formwork piece are effectively reduced, making it easier to manually handle and assemble in narrow pipe gallery spaces. This solves the problem of traditional steel formwork being difficult to install and dismantle due to the excessive size of the components.

[0019] 2. Due to the precise offset of 10mm towards the abdomen and 10mm towards the back at one end of the waistline dividing joint, the oblique dividing joint of the curved section formwork has definite geometric parameters. Finite element analysis and actual verification show that this 10mm offset is sufficient to eliminate the self-locking effect of the curved surface, while preventing the formwork from deforming under the lateral pressure of concrete due to excessive offset. Thus, the optimal design is achieved while ensuring the balance between smooth demolding and forming accuracy.

[0020] 3. Due to the adoption of a structure in which circumferential and axial stiffening ribs are evenly distributed on the outer surface of straight and / or curved template sections, with a spacing of 300mm between circumferential stiffening ribs and four 6mm thick first stiffening ribs and four 12mm thick second stiffening ribs in the axial stiffening ribs, the stiffening rib system optimized by finite element calculation achieves precise material distribution while ensuring that the overall stiffness of the template meets the requirements of concrete lateral pressure. 12mm stiffening ribs are used in areas with higher stress and 6mm stiffening ribs are used in areas with lower stress. This reduces the self-weight of the template and avoids the material redundancy caused by uniform stiffening ribs in traditional steel templates, further improving the convenience of handling and dismantling the template in narrow spaces. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0022] Figure 1 This is a schematic diagram of the elevation of a single section of the straight-cut steel core mold in this invention;

[0023] Figure 2 This is a schematic diagram of the elevation of the rubber gasket in this invention;

[0024] Figure 3 This is a schematic diagram of the unfolding of a single straight section in this invention;

[0025] Figure 4 This is a schematic diagram of the unfolded single-section straight segment combination in this invention;

[0026] Figure 5 This is a planar schematic diagram of the 90° (5 sections) bend in this invention;

[0027] Figure 6 This is a planar schematic diagram of the 54° (3 sections) bend in this invention;

[0028] Figure 7 For the present invention Figure 5 and Figure 6 Schematic diagram of the elevation of sections A and B at section 1-1;

[0029] Figure 8 For the present invention Figure 5 and Figure 6 Schematic diagram of a single section at section 1-1;

[0030] Figure 9 For the present invention Figure 5 and Figure 6 Schematic diagram of the elevation of sections A and B in section 2-2;

[0031] Figure 10 For the present invention Figure 5 and Figure 6 Schematic diagram of a single section at section 2-2;

[0032] Figure 11 This is a schematic diagram of the unfolded section B in this invention;

[0033] Figure 12 This is a schematic diagram of the unfolded curved section A in this invention;

[0034] Figure 13 This is a schematic diagram of the unfolded single section of the curved segment in this invention.

[0035] The attached diagram shows the markings and corresponding component names:

[0036] 1. Straight rubber gasket; 2. Steel plate; 3. Bolt; 4. Back rib steel plate; 5. Circular rubber gasket; 6. Bent section steel core mold A piece; 7. Bent section steel core mold B piece. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0038] Throughout this specification, references to "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in connection with that embodiment or example is included in at least one embodiment of the invention. Therefore, the phrases "an embodiment," "an example," "an example," or "an example" appearing in various places throughout the specification do not necessarily refer to the same embodiment or example. Furthermore, specific features, structures, or characteristics can be combined in one or more embodiments or examples in any suitable combination and / or sub-combination. Moreover, those skilled in the art will understand that the illustrations provided herein are for illustrative purposes and are not necessarily drawn to scale. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0039] In the description of this invention, the terms "front", "rear", "left", "right", "up", "down", "vertical", "horizontal", "high", "low", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of this invention.

[0040] The terms "first," "second," etc., used in this invention are merely for clarity of description and are not intended to limit any order or emphasize importance. Furthermore, the term "connection" as used herein, unless otherwise specified, can refer to a direct connection or an indirect connection via other components.

[0041] Example

[0042] like Figures 1-13 As shown, this embodiment provides an assembled circular steel core mold, including at least one straight section template unit and / or at least one curved section template unit. The straight section template unit is formed into a cylindrical shape by multiple straight section template pieces with wedge-shaped arc surfaces along the axial direction. The curved section template unit is formed into an arc-shaped tube by multiple curved section template pieces. Adjacent template pieces and adjacent template units are detachably connected by detachable connectors.

[0043] See Figures 1-5The straight section template unit is composed of four straight section template pieces. Each straight section template piece includes a steel plate 2 and a back rib steel plate 4 fixed to the outer surface of the steel plate 2. The wedge-shaped arc surface of the straight section template piece has a draft angle of 1:100 to 1:50 along the axial direction. By adopting a structure in which the straight section template unit is composed of four equal straight section template pieces, and each straight section template piece includes a steel plate 2 and a back rib steel plate 4 fixed to the outer surface of the steel plate 2, the straight section template unit achieves four-piece modularization while significantly enhancing the bending stiffness of each template piece through the back rib steel plate 4. This effectively reduces the size and weight of a single template piece while ensuring the overall structural strength is sufficient to resist the lateral pressure of concrete. This facilitates manual handling and assembly in narrow pipe gallery spaces, solving the problem of traditional steel formwork being difficult to install and dismantle due to excessively large components.

[0044] See Figures 1-5 Sealing gaskets are installed at the joints between adjacent straight template sections and at the joints between adjacent template units. This structure effectively seals all joints after template assembly, preventing grout leakage during concrete pouring and ensuring the quality of concrete forming and the flatness of the template's inner wall. The elastic cushioning effect of the sealing gaskets also facilitates the smooth separation of template sections during subsequent dismantling, indirectly improving installation and dismantling efficiency and the number of reuses.

[0045] Specifically, both the straight rubber gasket 1 and the circular rubber gasket 5 are made of ethylene propylene diene monomer (EPDM) or chloroprene rubber (CR), which have corrosion resistance and aging resistance properties and are suitable for nuclear power plant pipe gallery environments.

[0046] See Figures 1-5 The sealing gaskets include straight rubber gaskets 1 disposed at the joints between the straight template sections and circular rubber gaskets 5 disposed at the joints between each template unit. Because the sealing gaskets consist of straight rubber gaskets 1 disposed at the joints between the straight template sections and circular rubber gaskets 5 disposed at the joints between each template unit, rubber gaskets of appropriate shapes are used for different joint types (linear joints between sections and annular joints between units), achieving a more precise and reliable sealing effect. This prevents grout leakage from causing adhesion during template disassembly and compensates for assembly errors through the elastic deformation of the rubber material, further ensuring that the template maintains good sealing and smooth disassembly even after multiple reuses.

[0047] See Figures 1-13The straight and / or curved template sections are provided with back rib steel plates 4, and the detachable connectors are bolts 3. Corresponding connecting holes are provided on the back rib steel plates 4 for the bolts 3 to pass through. By using back rib steel plates 4 on the straight and / or curved template sections, and setting bolts 3 as the detachable connectors with connecting holes on the back rib steel plates 4 for the bolts 3 to pass through, the connecting force of the bolts 3 acts directly on the high-rigidity back rib steel plates 4 rather than the thin-walled steel plates 2 themselves. This avoids local deformation of the thin-walled steel plates 2 at the connection points and enables rapid fastening and disassembly between template sections and template units. Therefore, while ensuring connection reliability, it significantly shortens the installation and disassembly time, meeting the construction needs for efficient turnover in narrow spaces.

[0048] Specifically, the back rib steel plate 4, the circumferential stiffening rib, and the axial stiffening rib are all welded to the steel plate 2 using double-sided fillet welds. The weld height is not less than 0.7 times the thickness of the stiffening rib, and after welding, the surface is ground to form a smooth transition. The bolts 3 are equipped with spring washers or lock nuts, and the connecting holes on the back rib steel plate 4 are oblong holes, allowing for fine adjustments between the template pieces during assembly.

[0049] See Figures 6-8 The bending section template unit includes two interconnected bending section steel core mold pieces, A and B, which are joined together along the web-like direction of the bending section. Because the bending section template unit comprises these interconnected bending section steel core mold pieces A and B, with them joined along the web-like direction of the bending section, the bending section template unit is structurally divided into two large sections. This preserves the integrity of the overall arc shape of the bending section while achieving segmentation of the bending section template. This solves the problem of traditional bending section steel molds being unable to be removed from narrow spaces due to their integral molding, providing a structural basis for the rapid installation and dismantling of bending section templates at the bends of pipe racks.

[0050] See Figures 6-13 The back and front dividing seams of the curved section template unit extend axially, while the waistline dividing seams are inclined relative to the axial direction, with one end of the waistline dividing seam biased towards the abdomen and the other end biased towards the back. Due to this structure, the demolding path of the curved section template is optimized into a guiding oblique separation method, avoiding the jamming phenomenon caused by the self-locking effect of the curved surface during traditional axial straight seam division. This achieves smooth removal of the curved steel core mold after casting, significantly reducing the difficulty and time required for demolding the curved section.

[0051] Specifically, after optimization through finite element analysis, the waistline dividing seam adopts an oblique division with one end biased towards the abdomen by 10mm and the other end biased towards the back by 10mm. The stiffening rib system adopts a differentiated arrangement with a circumferential spacing of 300mm and four axial ribs of 6mm and four ribs of 12mm.

[0052] The finite element optimization process for the offset of the waistline dividing seam is as follows:

[0053] The difficulty in dismantling curved formwork stems primarily from the fact that, with traditional axial straight-joint segmentation, the curved formwork is difficult to separate after concrete pouring due to the shrinkage force of the concrete and the self-locking effect of the curved surface itself. To address this issue, this embodiment proposes setting the waistline segmentation as an oblique segmentation and determining the optimal offset through finite element analysis. This embodiment uses general-purpose finite element analysis software to establish a three-dimensional solid model of the steel core mold. The formwork and stiffening ribs are simulated using shell elements. The lateral pressure of the concrete is applied to the inner wall of the formwork as a surface load. The boundary conditions are set so that the contact relationship between adjacent formwork panels is frictional contact. The demolding process is simulated by gradually releasing the contact constraints.

[0054] A three-dimensional finite element model of the curved formwork was established. The web and back dividing joints were set to extend axially, and the waistline dividing joints were set to have five working conditions with offsets of 0mm (i.e., axial straight joint), 5mm, 10mm, 15mm, and 20mm. A concrete lateral pressure of 19kPa (calculated according to GB50666-2011) was applied to the model, and the displacement process of the formwork panels separating during demolding was simulated. The peak tensile force required for the separation of the formwork panels and the maximum equivalent stress of the formwork panels under each working condition were extracted.

[0055] The calculation results show that:

[0056] When the offset is 0mm (axial straight seam), the peak tensile force of the template sheet separation is 12.6kN, and there is obvious jamming during the demolding process, requiring repeated tapping to separate it;

[0057] When the offset is 5mm, the peak tensile force drops to 8.3kN, and the jamming phenomenon is significantly reduced;

[0058] When the offset is 10mm, the peak tensile force is further reduced to 4.1kN, the demolding process is smooth and without jamming, and the maximum equivalent stress of the template sheet is 32.5MPa, which is far below the material yield strength.

[0059] When the offset is 15mm, the peak tensile force drops to 3.2kN, but the template sheet has a misalignment of 0.3mm under the action of concrete lateral pressure, which may affect the flatness of the concrete molding.

[0060] When the offset is 20mm, the misalignment increases to 0.8mm, and stress concentration occurs at the root of the template sheet, with the maximum equivalent stress reaching 68MPa.

[0061] Taking into account both the smoothness of demolding and the accuracy of molding, the optimal offset for the waistline dividing joint was determined to be 10mm, that is, 10mm offset towards the abdomen on one end and 10mm offset towards the back on the other end. This offset can effectively eliminate the self-locking effect of the curved surface, achieve smooth demolding, and ensure that the formwork does not experience significant misalignment under the lateral pressure of the concrete, thus ensuring the quality of concrete molding.

[0062] The finite element optimization process of the stiffening rib system is as follows:

[0063] To achieve lightweight design while ensuring the overall stiffness of the formwork, this embodiment optimizes the stiffening rib system. The circumferential stiffening rib spacing, the number and thickness of axial stiffening ribs are used as design variables. The objective function is to minimize the total weight of the formwork, with constraints that the maximum equivalent stress of the formwork does not exceed the material's yield strength and the maximum deformation does not exceed 1 / 400 of the formwork span. Multi-parameter finite element optimization analysis is performed. The finite element optimization of the stiffening rib system adopts the same modeling method as the aforementioned waistline segmentation joint optimization: a three-dimensional solid model of the steel core mold is established using general-purpose finite element analysis software. The formwork and stiffening ribs are simulated using shell elements. The concrete lateral pressure is applied to the inner wall of the formwork as a surface load, and the boundary conditions are set to allow frictional contact between adjacent formwork panels.

[0064] The optimization employed a parametric scanning method, with design variables including: circumferential stiffener spacing (range 200mm-500mm, step size 50mm), number of axial stiffeners (4, 6, 8, 10), and axial stiffener thickness (4mm, 6mm, 8mm, 10mm, 12mm). The objective function was to minimize the total weight of the formwork, with constraints of maximum equivalent stress ≤235MPa and maximum deformation ≤L / 400 (L being the formwork span). A total of 120 working conditions were calculated, and the optimal solution that satisfied the constraints and minimized the weight was selected.

[0065] The initial design adopted axial stiffening ribs with a circumferential stiffening rib spacing of 400mm and eight axial stiffening ribs with a thickness of 6mm. The calculated maximum equivalent stress of the template was 187MPa and the maximum deformation was 2.4mm. Although the strength requirements were met, the total weight of the template was 286kg. The single template section (0.6m in length) was relatively heavy, which was not conducive to manual handling and installation / disassembly.

[0066] Sensitivity analysis revealed that reducing the spacing of the circumferential stiffeners from 400mm to 300mm reduced the maximum equivalent stress of the formwork from 187MPa to 126MPa, the maximum deformation from 2.4mm to 1.6mm, and the formwork weight increased by only 8kg. The axial stiffeners were arranged with differentiated thicknesses, that is, the thickness of the stiffeners was increased at the locations with higher stress (near the intersection with the circumferential stiffeners), which could effectively improve the local stiffness without significantly increasing the weight.

[0067] Based on the above analysis, the optimization scheme is determined as follows: the spacing between circumferential stiffeners is 300mm; a total of eight axial stiffeners are set, of which four stiffeners with a thickness of 6mm and a height of 60mm are arranged in the middle area between adjacent circumferential stiffeners, and the other four stiffeners with a thickness of 12mm and a height of 60mm are arranged directly below the circumferential stiffeners to form a differentiated arrangement.

[0068] Finite element analysis revealed that the optimized template exhibits a maximum equivalent stress of 94 MPa, a maximum deformation of 1.2 mm, and a total weight of 224 kg, representing a 21.7% reduction compared to the initial design. Furthermore, the differentiated stiffening rib arrangement enhances the rigidity of the template at critical stress points while significantly reducing overall weight. This allows a single section of the template to be handled manually by two workers without the need for heavy machinery, achieving the design goal of rapid installation and dismantling in confined spaces.

[0069] Optimization results show that, under the premise of meeting strength and stiffness constraints, a circumferential stiffener spacing of 300mm is the optimal balance point. Although further reducing the spacing can reduce stress, the weight increases significantly, which does not meet the lightweighting target. When the number of axial stiffeners is eight, the stress distribution is the most uniform. Among the eight axial stiffeners, the differentiated arrangement of four 6mm thick and four 12mm thick stiffeners reduces the weight by 21.7% compared to using all 12mm thick stiffeners, and the maximum equivalent stress is reduced from 187MPa to 94MPa, achieving the optimal balance between lightweighting and structural strength.

[0070] Through the aforementioned finite element optimization analysis, this embodiment determined the 10mm offset of the waistline dividing joint and the optimized arrangement of the stiffening rib system. Actual construction verification showed that the prefabricated circular steel core mold using this optimized scheme exhibited a 67% reduction in peak tensile force during demolding compared to the traditional axial straight joint structure, and a 21.7% reduction in the total weight of the formwork compared to the initial design. A single section of the formwork could be manually handled and dismantled by two workers. While ensuring structural strength and anti-buoyancy safety, it achieved rapid dismantling and efficient turnover in confined spaces, effectively solving the technical problems existing in the prior art.

[0071] To meet anti-buoyancy safety requirements, the straight and / or curved template units are equipped with anti-buoyancy anchoring structures. These anchoring structures include arc-shaped rings spaced at intervals along the axial direction of the template unit. These arc-shaped rings are welded to pre-embedded inverted U-shaped anchor bars, with two anchor cables corresponding to each arc-shaped ring. The arc-shaped rings and inverted U-shaped anchor bars are welded together, with the welding points positioned for easy cutting, allowing for separation by cutting the weld points during template removal and enabling the anchor bars to be reused. In other embodiments, the arc-shaped rings and inverted U-shaped anchor bars can also be connected using detachable connectors such as bolts or clips. Based on buoyancy calculations during concrete pouring, the buoyancy force on a single template section (0.6m in length) is:

[0072] ;

[0073] HRB400 grade III steel bars with a diameter of 16mm were used to construct the arc rings, with one set every 0.6m along the axial direction of the formwork unit. Each arc ring was welded to two pre-embedded inverted U-shaped anchor bars, and the anchor bar was embedded in the concrete for 300mm. Based on the bond strength of C30 concrete, the pull-out force of a single anchor bar was calculated as follows:

[0074] ;

[0075] Each arc-shaped ring corresponds to two anchor bars, with a total pull-out resistance of 24.2kN, far exceeding the buoyancy force of 11.1kN, and a safety factor of 2.18, meeting the anti-buoyancy requirements. This anti-buoyancy anchoring structure adopts an internal design, eliminating the need for additional counterweights or support systems outside the formwork, ensuring the cleanliness of the external space of the formwork and facilitating installation and dismantling operations.

[0076] The specific construction process includes the following steps:

[0077] Step 1: Assemble into single sections in the background.

[0078] Four equal straight template pieces are connected by bolts 3 through the connecting holes on the back rib steel plate 4, forming a cylindrical shape to create a single straight section. Straight rubber gaskets 1 are inserted at the joints between adjacent straight template pieces. The curved section steel core mold A piece 6 and curved section steel core mold B piece 7 are butt-jointed along the web direction of the curved section and connected by bolts 3, forming an arc-shaped tube to create a single curved section. Straight rubber gaskets 1 are inserted at the butt joint.

[0079] Step 2: Hoist the equipment to the construction site.

[0080] The assembled straight and curved sections are categorized, packaged, and transported to the construction site by vehicles. A truck crane or manual labor with simple lifting equipment is used to hoist the individual formwork units to the construction location in the pipe gallery or trench. Since each individual formwork section (0.6m in length) weighs only 224kg, it can be carried by hand by two workers without relying on heavy machinery, making it particularly suitable for formwork placement in confined spaces.

[0081] Step 3: Intersegmental connection

[0082] Circular rubber gaskets 5 are added between adjacent sections, and bolts 3 are used to connect them through the connecting holes on the back rib steel plate 4. For straight sections, they are connected sequentially from one end to the other to form a straight section template; for curved sections, they are connected sequentially according to the designed curvature (e.g., 5 sections for 90°, 3 sections for 54°) to form a complete curved section template. When connecting, ensure that the waistline dividing joints of adjacent sections are aligned to form a continuous oblique demolding path. An arc ring is set every 0.6m along the axial direction of the template unit. The arc ring is made of HRB400 grade III steel bars with a diameter of 16mm. The arc ring is welded to the pre-embedded inverted U-shaped anchor bars. Each arc ring corresponds to two anchor cables, and the anchor cable length is 300mm. According to calculations, the buoyancy force on a single section template (length 0.6m) is 11.1kN, the total pull-out force of the two anchor bars of each arc ring is 24.2kN, and the safety factor is 2.18, which meets the anti-buoyancy requirements. Using the elongated holes on the back rib steel plate 4, fine-tune the relative positions between adjacent sections to ensure that the template axis, elevation, and curvature meet the design requirements. Check the tightness of all bolts 3 to ensure that the connection between sections is firm and that the sealing gaskets are properly compacted.

[0083] Step 4: Concrete pouring

[0084] After passing the acceptance inspection, concrete pouring will proceed.

[0085] Step 5: Template Removal

[0086] After the concrete reaches the design strength, the formwork is removed. The removal sequence is the reverse of the assembly sequence: First, loosen the bolts 3 between sections to disconnect the connections between individual sections. Then, loosen the bolts between panels to disconnect the connections between the individual formwork panels. For straight sections, remove the top formwork panel first, then remove the side formwork panels in sequence, and finally remove the bottom formwork panel. For curved sections, utilize the oblique guiding effect of the waistline dividing joint to first separate the curved section steel core mold A panel 6 and the curved section steel core mold B panel 7, and then remove them one by one. Because the waistline dividing joint adopts an oblique dividing design with one end biased towards the abdomen and the other end biased towards the back 10mm, the formwork panels automatically detach from the concrete surface when separated obliquely, effectively avoiding the self-locking effect of the curved surface. Finite element analysis verified that the peak tensile force during demolding is 4.1kN, which is 67% lower than that of the traditional axial straight joint structure (12.6kN). The demolding process is smooth and does not require hammering or the use of pry bars.

[0087] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A modular circular steel core mold, characterized in that, It includes at least one straight section template unit and / or at least one curved section template unit. The straight section template unit is formed into a cylindrical shape by multiple straight section template pieces with wedge-shaped arc surfaces along the axial direction. The curved section template unit is formed into an arc-shaped tube by multiple curved section template pieces. Adjacent template pieces and adjacent template units are detachably connected by detachable connectors.

2. The assembled circular steel core mold according to claim 1, characterized in that, The straight section template unit is formed by four straight section template pieces, each of which includes a steel plate (2) and a back rib steel plate (4) fixed to the outer surface of the steel plate (2).

3. The assembled circular steel core mold according to claim 2, characterized in that, Sealing gaskets are installed at the joints between adjacent straight template sections and at the joints between adjacent template units.

4. The assembled circular steel core mold according to claim 3, characterized in that, The sealing gaskets include straight strip rubber gaskets (1) disposed at the joints between the straight section template pieces, and circular rubber gaskets (5) disposed at the joints between each template unit.

5. The assembled circular steel core mold according to claim 1, characterized in that, The straight section template and / or the curved section template are provided with a back rib steel plate (4), the detachable connector is a bolt (3), and the back rib steel plate (4) is provided with a corresponding connecting hole for the bolt (3) to pass through.

6. The assembled circular steel core mold according to claim 1, characterized in that, The bending section template unit includes a bending section steel core mold A piece (6) and a bending section steel core mold B piece (7) that are spliced ​​together. The bending section steel core mold A piece (6) and the bending section steel core mold B piece (7) are connected along the back and front directions of the bending section.

7. The assembled circular steel core mold according to claim 6, characterized in that, The abdominal and back dividing seams of the curved template unit extend axially, and the waistline dividing seams are inclined relative to the axial direction, with one end of the waistline dividing seam biased towards the abdomen and the other end biased towards the back.

8. The assembled circular steel core mold according to claim 7, characterized in that, One end of the waistline dividing seam is offset 10mm towards the abdomen, and the other end is offset 10mm towards the back.

9. The assembled circular steel core mold according to claim 1, characterized in that, The outer surface of the straight section template piece and / or the curved section template piece is evenly provided with circumferential stiffening ribs and axial stiffening ribs. The spacing of the circumferential stiffening ribs is 300mm. The axial stiffening ribs include four first stiffening ribs with a thickness of 6mm and four second stiffening ribs with a thickness of 12mm.

10. The assembled circular steel core mold according to claim 1, characterized in that, The straight section template unit and / or curved section template unit are provided with an anti-buoyancy anchoring structure. The anti-buoyancy anchoring structure includes arc-shaped rings arranged at intervals along the axial direction of the template unit. The arc-shaped rings are welded to the pre-embedded inverted U-shaped anchor bars, and each arc-shaped ring is provided with two anchor cables.

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