Pre-tilt installation construction method for cantilever steel formwork platform

Abstract

The invention discloses a pre-tilt mounting construction method for a cantilever steel formwork platform, which aims at solving the problem that a cantilever steel formwork is easy to generate lateral deformation and uneven interface stress in a concrete pouring process in ship lock side wall construction, and provides a pre-tilt mounting construction method for the cantilever steel formwork platform through theoretical lateral pressure analysis and formwork stress calculation. The maximum lateral deformation of the formwork under the construction working condition is solved, the installation pre-inclination angle of the formwork is determined according to the maximum lateral deformation, and cooperative control of first compensation, second deformation and final in-place in the construction period is achieved; in the construction process, a formwork platform is installed according to a pre-inclination angle, and fine adjustment and locking are conducted through an inclined support, a sliding rail adjusting mechanism and other adjustable connecting pieces, so that it is guaranteed that a formwork reaches a designed line shape under the effect of concrete side pressure; according to the method, lateral deformation of the formwork structure in the construction period can be reduced, the side wall forming precision is improved, and the construction quality and safety of the ship lock structure are improved.

Description

Technical Field

[0001] This invention relates to the field of cantilever formwork construction technology, and more specifically, to a method for pre-tilting installation of a cantilever steel formwork platform. Background Technology

[0002] The lock sidewall is a typical large-scale, tall concrete structure. During its construction, cantilever steel formwork platforms are commonly used for segmented casting. During concrete pouring and vibration, the formwork system is subjected to significant lateral pressure and dynamic additional forces. Due to the characteristics of its stress boundary, the cantilever steel formwork usually exhibits significant lateral deformation in the vertical direction and at the cantilever ends. If reasonable stress analysis and deformation control methods are lacking, the actual working line of the formwork can easily deviate from the design state, thereby affecting the forming quality of the lock sidewall.

[0003] Currently, engineering projects mainly rely on increasing the stiffness of the formwork, strengthening the support system, or using empirical corrections to control deformation. However, on the one hand, increasing the stiffness will significantly increase construction costs and it is difficult to completely eliminate the deformation effects caused by the cantilever stress characteristics. On the other hand, empirical control methods lack clear theoretical basis and are difficult to achieve predictable and verifiable linear control effects. Summary of the Invention

[0004] The purpose of this invention is to provide a pre-tilted installation construction method for a cantilever steel formwork platform to solve the above-mentioned problems existing in the prior art.

[0005] The application is as follows: A method for pre-tilting installation of a cantilever steel formwork platform includes the following steps: S1 determines the design value of concrete lateral pressure based on construction parameters: Based on the density of concrete γ c The pouring speed v, initial setting time t0, total height h from the calculated location of the concrete lateral pressure to the top surface of the freshly poured concrete, influence coefficient β1 of admixtures, and influence coefficient β2 of slump are respectively calculated according to...

[0006] and

[0007] Two lateral pressure values ​​were calculated, and the smaller value was taken as the basic value of the lateral pressure of the newly poured concrete. At the same time, the additional horizontal load of the poured concrete was superimposed and the loads were combined to obtain the design value p of the formwork lateral pressure. d ; S2 performs stress analysis on the template structure based on the lateral pressure design value: The design value of the side pressure p dFor cantilever steel formwork structures, the lateral deformation curves of the formwork are obtained through structural mechanics calculations or finite element analysis, and the maximum lateral displacement δ of the formwork under construction conditions is determined. max ; S3 determines the pre-tilt angle for template installation based on the maximum deformation: Using the effective pressure height H of the template as the geometric reference, the maximum lateral displacement δ max Converted to template installation pre-tilt angle θ pre And satisfy:

[0008] S4 Install the template according to the pre-tilted angle: During the installation of cantilever steel formwork, the formwork is installed with a slight inward tilt along the water-facing side, and the angle is locked by adjustable screw rods, diagonal supports and connecting tie rods. This allows the formwork to deform and return to its upright position under the lateral pressure of the concrete, ultimately achieving the designed vertical forming effect.

[0009] Furthermore, the theoretical lateral displacement is calculated as follows: Based on the target lateral pressure distribution formed by the combined effects of temperature shrinkage of the sidewall concrete and external constraints, a spatial combined stress analysis model is established with the cantilever steel formwork platform as the main stress-bearing unit. The target lateral pressure distribution is converted into equivalent lateral loads and equivalent bending moments acting on the formwork structure system. Through structural mechanics analysis, the lateral stress and deformation of the cantilever formwork platform under construction conditions are solved, and its maximum lateral displacement δ is obtained. max And the lateral deformation curve along the height of the wall.

[0010] Furthermore, the pre-tilt angle θ pre The determination process includes: Based on the structural stiffness, projected height, lateral pressure distribution of concrete, and pouring rate parameters of the cantilever steel formwork, an elastic deformation analysis model for the formwork structure is established. By solving the theoretical lateral deformation curve of the formwork under the design limit construction condition, the pre-tilt angle θ corresponding to the maximum deformation is obtained. pre This causes the formwork to tend to be vertical after being subjected to the lateral pressure of the concrete.

[0011] Furthermore, the pre-tilt angle θ pre A uniform overall angle setting or different pre-tilt amounts can be set in segments along the height direction of the template to match the actual distribution of concrete lateral pressure.

[0012] Furthermore, the pre-tilt angle is achieved through the lead screws at both ends of the inclined support, the vertical truss, and the slide rail adjustment mechanism, and is locked with bolts to form a stable installation state.

[0013] Furthermore, after the template is installed, the initial tilt state of the template is detected and verified by using a laser verticality meter, total station, or monitoring target array to ensure that the pre-tilt amount meets the design target.

[0014] Furthermore, the method is used for the construction of integral lifting cantilever formwork for the tall concrete structures of the lock head, lock chamber, and navigation wall of a ship lock.

[0015] Compared with the prior art, the embodiments of the present invention achieve the following beneficial effects: This invention establishes a spatial stress model of a cantilever steel formwork platform, transforming the lateral pressure of concrete during the pouring stage into equivalent bending moments and lateral deformations. Based on this, it calculates the theoretical maximum lateral displacement of the formwork structure under construction conditions, thereby determining a reasonable pre-tilt angle. This allows the formwork to approach the design target posture after actual stress and deformation, achieving coordinated control of the formwork posture during construction: "compensation first, deformation later, and final positioning." Through the calculation and implementation of the pre-tilt angle, the formwork achieves a shape close to the design after lateral pressure, effectively offsetting the elastic deformation caused by lateral pressure. This avoids the cost and weight problems caused by excessive thickness due to insufficient formwork stiffness, and improves the verticality of the facade and the accuracy of the structural alignment after concrete molding. Attached Figure Description

[0016] Figure 1 This is a structural schematic diagram of the cantilever steel formwork provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of the cantilever steel formwork panel provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the bottom platform of the cantilever steel formwork provided in an embodiment of the present invention; Figure 4 This is a structural schematic diagram of the cantilever steel formwork support system provided in an embodiment of the present invention.

[0017] Among them: 1-panel, 11-steel plate, 12-back vertical rib, 13-back horizontal rib, 2-top platform, 21-top platform support frame, 22-platform railing, 3-bottom platform, 31-top horizontal beam, 32-vertical beam, 33-diagonal bar, 34-horizontal bar, 4-support system, 41-vertical truss, 42-diagonal support, 43-slide rail adjustment mechanism. Detailed Implementation

[0018] The present invention will now be described in detail with reference to the accompanying drawings.

[0019] Example 1

[0020] This invention provides a pre-tilted installation method for a cantilever steel formwork platform. Before the formwork is subjected to the lateral pressure of concrete, the cantilever steel formwork platform is pre-tilted slightly inward to the inside of the structure, so that the formwork forms a stable initial inward tilted state. Under the lateral pressure of newly poured concrete and construction live load, the formwork gradually rebounds from the tilted state to approach the designed vertical position, thereby offsetting the elastic deformation of the formwork caused by the lateral pressure of concrete and ensuring the linear accuracy and verticality of the structure after it is formed.

[0021] During the implementation process, the template is first positioned in plane according to the axis of the construction site; then the load-bearing system, such as the vertical truss 41, the sliding rail adjustment mechanism 43, and the diagonal support 42, is installed; then the template is slightly tilted inward by adjusting the screw rod of the diagonal support 42; the tilt angle is confirmed and locked by precision measuring equipment; finally, concrete is poured in the template locked state.

[0022] Please refer to Figure 1-4 Taking the concrete construction of the side wall of a lock chamber as an example, the wall height is about 3.1m. A cantilever steel formwork system is used for layered pouring construction. The cantilever steel formwork consists of panel 1, top platform 2, bottom platform 3 and support system 4.

[0023] Please refer to Figure 2 The panel 1 is composed of a steel plate 11, a back vertical rib 12, and a back horizontal rib 13. The steel plate 11 is 3m×3.1m in size and 6mm thick, and is made of Q235 material; the back vertical rib 12 consists of 8 No. 8 channel steels arranged at a spacing of 35cm; the back horizontal rib 13 consists of 3 double No. 14 channel steels arranged at a spacing of 136cm.

[0024] Please refer to Figure 1 The top platform support frame 21 is formed by connecting and combining horizontally and diagonally arranged equilateral angle steels with vertically arranged equilateral angle steels. The outer end is provided with a welded steel pipe with a square cross section as a railing post insertion hole. The top platform 2 is provided with a platform railing 22 with a height of 1.2m.

[0025] Please refer to Figure 3 The bottom platform 3 is composed of a top crossbeam 31 of double-section No. 14 channel steel, a vertical beam 32 of double-section No. 12 channel steel, and a diagonal brace 33 of double-section No. 12 channel steel. Two No. 10 channel steels are added in the middle as crossbars 34 for reinforcement.

[0026] Please refer to Figure 4The support system 4 consists of a vertical truss 41, diagonal supports 42, and a slide rail adjustment mechanism 43. The vertical truss 41 is made of double-layered No. 18 channel steel, with No. 10 channel steel used for connecting rods between the trusses, spaced 1m apart. The vertical truss 41 is connected to the panel 1 via 20mm diameter precision-rolled threaded steel as connecting rods. The slide rail adjustment mechanism 43 is placed on the bottom platform 3. The diagonal supports 42 are circular steel pipes with an outer diameter of 76mm and a wall thickness of 6mm, connecting the vertical truss 41 to the slide rail adjustment mechanism 43, and adjusting the forward and backward movement of the formwork via screws at both ends.

[0027] To achieve the scientific determination of the pre-tilt angle, this invention simplifies the cantilever steel formwork into a stress-bearing body that is elastically compressed and bent along the height direction, based on the construction design conditions and formwork structural parameters, and establishes a structural stress analysis model for it before the cantilever steel formwork is installed.

[0028] The maximum lateral pressure exerted on the formwork by freshly poured concrete is calculated using the following formula:

[0029] and

[0030] The smaller value is taken as the standard value of the control lateral pressure, and combined with the construction live load to form the design lateral pressure P. d .

[0031] The lateral pressure is applied as a distributed load along the height of the formwork to the formwork stress model. The equivalent bending moment distribution and lateral deformation curve of the formwork under this load condition are calculated, and the maximum lateral displacement δ is obtained. max And the deformation pattern along the height direction. The deformation results of this theory serve as the basis for pre-tilt compensation.

[0032] Based on the project construction parameters: Concrete density γ c =25kN / m³; Pouring speed ν = 0.5 m / h; The initial setting time of the concrete is t0 = 8 h; The correction factor for the effect of admixtures is β1 = 1.2; The correction factor for the effect of concrete slump is β2 = 1.0; Pouring height H≈3.0m Calculated based on standard side pressure:

[0033]

[0034] Take the smaller value: p =41.2 kPa Considering load combinations (including construction live loads): p d =1.2×41.2+1.4×2=52.3 kPa This embodiment uses: p d =52.3 kPa The design of the lateral pressure is used for template stress analysis.

[0035] Based on the template structure system, the template is simplified into an approximate cantilever bending structure system with continuous support. The equivalent lateral pressure is applied along the height of the template, and the maximum lateral displacement δ of the template is obtained through structural mechanics calculations or finite element analysis. max .

[0036] The pre-tilt angle for template installation can be determined according to the basic principle of pre-tilt compensation based on the present invention:

[0037] Where: H is the effective stress-bearing height of the template; θ pre This refers to the inward pre-tilt angle during template installation.

[0038] During the pre-tilt installation process, the pre-tilt angle θ pre A uniform overall angle setting or different pre-tilt amounts can be set in segments along the height direction of the template to match the actual distribution of concrete lateral pressure.

[0039] Furthermore, the pre-tilt angle is achieved through the lead screws at both ends of the inclined support 42, the vertical truss 41, and the slide rail adjustment mechanism 43, and is locked with bolts to form a stable installation state.

[0040] Furthermore, after the template is installed, the initial tilt state of the template is detected and verified by using a laser verticality meter, total station, or monitoring target array to ensure that the pre-tilt amount meets the design target.

[0041] Furthermore, the method is used for the construction of integral lifting cantilever formwork for tall concrete structures such as lock heads, lock chambers, and navigation walls.

[0042] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0043] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of the invention and form different embodiments. Any of the claimed embodiments can be used in any combination.

Claims

1. A method for pre-tilting installation of a cantilever steel formwork platform, characterized in that, Includes the following steps: S1 determines the design value of concrete lateral pressure based on construction parameters: Based on the density of concrete γ c The pouring speed v, initial setting time t0, total height h from the calculated location of the concrete lateral pressure to the top surface of the freshly poured concrete, influence coefficient β1 of admixtures, and influence coefficient β2 of slump are respectively calculated according to... and Two lateral pressure values ​​were calculated, and the smaller value was taken as the basic value of the lateral pressure of the newly poured concrete. At the same time, the additional horizontal load of the poured concrete was superimposed and the loads were combined to obtain the design value p of the formwork lateral pressure. d ; S2 performs stress analysis on the template structure based on the lateral pressure design value: The design value of the side pressure p d For cantilever steel formwork structures, the lateral deformation curves of the formwork are obtained through structural mechanics calculations or finite element analysis, and the maximum lateral displacement δ of the formwork under construction conditions is determined. max ; S3 determines the pre-tilt angle for template installation based on the maximum deformation: Using the effective pressure height H of the template as the geometric reference, the maximum lateral displacement δ max Converted to template installation pre-tilt angle θ pre And satisfy: ； S4 Install the template according to the pre-tilted angle: During the installation of cantilever steel formwork, the formwork is installed with a slight inward tilt along the water-facing side, and the angle is locked by adjustable screw rods, diagonal supports and connecting tie rods. This allows the formwork to deform back to its original position under the lateral pressure of the concrete, ultimately achieving the designed vertical forming effect.

2. The pre-tilted installation construction method for a cantilever steel formwork platform according to claim 1, characterized in that, The theoretical lateral displacement is solved as follows: Based on the target lateral pressure distribution formed by the combined effects of temperature shrinkage of the sidewall concrete and external constraints, a spatial combined stress analysis model is established with the cantilever steel formwork platform as the main stress-bearing unit. The target lateral pressure distribution is converted into equivalent lateral loads and equivalent bending moments acting on the formwork structure system. Through structural mechanics analysis, the lateral stress and deformation of the cantilever formwork platform under construction conditions are solved, and its maximum lateral displacement δ is obtained. max And the lateral deformation curve along the height of the wall.

3. The pre-tilted installation construction method for a cantilever steel formwork platform according to claim 1, characterized in that, The pretilt angle θ pre The determination process includes: Based on the structural stiffness, projected height, lateral pressure distribution of concrete, and pouring rate parameters of the cantilever steel formwork, an elastic deformation analysis model for the formwork structure is established. By solving the theoretical lateral deformation curve of the formwork under the design limit construction condition, the pre-tilt angle θ corresponding to the maximum deformation is obtained. pre This causes the formwork to tend to be vertical after being subjected to the lateral pressure of the concrete.

4. The pre-tilted installation construction method for a cantilever steel formwork platform according to claim 1, characterized in that, The pretilt angle θ pre A uniform overall angle setting or different pre-tilt amounts can be set in segments along the height direction of the template to match the actual distribution of concrete lateral pressure.

5. The pre-tilted installation construction method for a cantilever steel formwork platform according to claim 1, characterized in that, The pre-tilt angle is achieved through the screw rods at both ends of the inclined support, the vertical truss, and the slide rail adjustment mechanism, and is locked with bolts to form a stable installation state.

6. The pre-tilted installation construction method for a cantilever steel formwork platform according to claim 1, characterized in that, After the template is installed, the initial tilt state of the template is checked and verified by using a laser verticality meter, total station or monitoring target array to ensure that the pre-tilt amount meets the design target.

7. The pre-tilted installation construction method for a cantilever steel formwork platform according to claim 1, characterized in that, The method is used for the construction of integral lifting cantilever formwork for tall concrete structures such as lock heads, lock chambers, and navigation walls of ship locks.

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