Design method for elevation of bottom die of movable die frame

Abstract

The invention relates to the technical field of bridge construction, in particular to a movable formwork bottom formwork elevation design method, which comprises the following steps of: performing a pre-pressing test on an initial movable formwork manufactured on the basis of a designed beam bottom elevation to obtain a main beam deflection value and an inelastic deformation amount of the initial movable formwork; the concrete box girder anti-arch value of the initial movable formwork is determined; the bottom formwork construction pre-camber of the movable formwork is obtained based on the main beam deflection value, the main beam non-elastic deformation amount and the concrete box beam anti-camber value; and the bottom formwork elevation of the movable formwork is calculated based on the bottom formwork construction pre-camber and the designed beam bottom elevation. The method comprises the following steps: performing simulated load pressurization on the movable formwork through a pre-pressing test, analyzing and verifying elastic deformation and non-elastic deformation of a main beam frame of the movable formwork and an accessory structure thereof by simulating a loading process of the movable formwork, and guiding a pre-camber value of a formwork and a concrete layered pouring sequence in the construction of the movable formwork based on a deformation rule of the main beam frame and the accessory structure of the movable formwork. A safe movable formwork bottom formwork elevation is designed, and the safety of later construction of the movable formwork is ensured.

Description

Technical Field

[0001] This invention relates to the field of bridge construction technology, and in particular to a method for designing the elevation of the bottom formwork of a movable formwork. Background Technology

[0002] The mobile formwork method is a modern bridge construction approach characterized by high flexibility and adaptability. It involves pouring concrete beams segment by segment between bridge piers using a movable formwork system, ultimately forming the complete bridge structure. Due to its speed, efficiency, energy saving, and environmental friendliness, the mobile formwork method significantly shortens the construction cycle, reduces project costs, and minimizes the impact on the surrounding environment. It has been widely adopted in the construction of continuous beams for highway and railway bridges and is considered a relatively advanced construction method.

[0003] Elastic and inelastic deformations occur during the assembly of mobile formwork, resulting in uncertainties in the strength, stiffness, and stress stability of the structure, which affects construction safety. Therefore, when using the mobile formwork method, it is necessary to clarify the strength, stiffness, and stress stability of each part of the structure, determine whether the formwork's load-bearing capacity can meet the design requirements, and ensure construction safety. Summary of the Invention

[0004] This invention provides a method for designing the bottom formwork elevation of a mobile formwork, which addresses the shortcomings of existing technologies where elastic and inelastic deformations during the assembly of mobile formwork affect construction safety. The method eliminates the inelastic deformation during the assembly of mobile formwork, calculates the actual value of the elastic deformation of the formwork under construction load, and uses this as the basis for setting the pre-camber of the construction template, thereby designing a safe bottom formwork elevation for the mobile formwork.

[0005] This invention provides a method for designing the bottom formwork elevation of a movable formwork, comprising: determining the design beam bottom elevation of the movable formwork; fabricating an initial movable formwork based on the design beam bottom elevation; conducting a pre-stressing test on the initial movable formwork to obtain the main beam deflection value and the inelastic deformation amount of the main beam; determining the concrete box girder camber value of the initial movable formwork according to the alignment control regulations; obtaining the bottom formwork construction pre-camber of the movable formwork based on the main beam deflection value, the main beam inelastic deformation amount, and the concrete box girder camber value; and calculating the bottom formwork elevation of the movable formwork based on the bottom formwork construction pre-camber and the design beam bottom elevation.

[0006] According to a method for designing the elevation of the bottom formwork of a movable formwork provided by the present invention, the method for conducting a pre-loading test on the initial movable formwork to obtain the deflection value and inelastic deformation of the main beam of the initial movable formwork includes: conducting a no-load test on the initial movable formwork, setting multiple observation points on the initial movable formwork to simulate the accurate position of the actual empty formwork bed, and recording the elevation values ​​of the multiple observation points as the pre-loading elevation; conducting a simulated surcharge test on the initial movable formwork, sequentially using precast concrete blocks to perform a pre-loading and pre-loading unloading process on the initial movable formwork, and recording the elevation values ​​of the multiple observation points as the post-loading elevation and the post-unloading elevation, respectively; calculating the elastic deformation of the initial movable formwork based on the post-loading elevation and the post-unloading elevation to obtain the deflection value of the main beam of the initial movable formwork; and calculating the inelastic deformation of the main beam of the initial movable formwork based on the pre-loading elevation and the post-unloading elevation.

[0007] According to the present invention, a method for designing the bottom formwork elevation of a movable formwork is provided, wherein the deflection value of the main beam of the initial movable formwork is calculated by the following formula: The inelastic deformation of the main beam of the initial moving formwork is calculated using the following formula: In the formula, This represents the initial deflection value of the main beam of the moving formwork. This represents the inelastic deformation of the main beam of the initial moving formwork. This indicates the pre-loading elevation of the observation point on the main beam; This indicates the post-loading elevation of the observation point on the main beam; This indicates the elevation of the observation point on the main beam after unloading.

[0008] According to the present invention, a method for designing the elevation of the bottom formwork of a movable formwork includes multiple observation points symmetrically arranged on the left and right main beams of the initial movable formwork, multiple observation points symmetrically arranged on the left and right cantilever beams of the initial movable formwork, multiple observation points symmetrically arranged on the bottom formwork of the initial movable formwork, and multiple observation points symmetrically arranged on the wing formwork of the initial movable formwork.

[0009] According to the present invention, a method for designing the elevation of the bottom formwork of a movable formwork is provided. The preloading process includes a three-stage loading process, wherein the loading loads are 0-60%, 60%-100%, and 100%-110% of the maximum construction load of the movable formwork in sequence, and the holding times of the three-stage loading should be no less than 2 hours, 2 hours, and 8 hours in sequence. The pre-loading unloading process includes a three-stage unloading process, with the unloading loads being 110%~100%, 100%~60%, and 60%~0% of the maximum construction load of the movable formwork, respectively. The holding times for the three stages of unloading should be no less than 8 hours, 4 hours, and 4 hours, respectively.

[0010] According to the present invention, a method for designing the bottom formwork elevation of a movable formwork is provided, wherein during the pre-loading process, loading is performed symmetrically in layers along the longitudinal and transverse directions of the initial movable formwork, and during the pre-loading unloading process, unloading is performed symmetrically in layers along the longitudinal and transverse directions of the initial movable formwork.

[0011] According to the present invention, a method for designing the elevation of the bottom formwork of a movable formwork is provided, wherein the pre-camber of the bottom formwork is calculated by the following formula: In the formula, This indicates the pre-camber during bottom formwork construction, with upward camber being positive. This represents the initial deflection value of the main beam of the moving formwork, with downward deflection being positive. This represents the inelastic deformation of the main beam of the initial moving formwork, with downward deformation being positive. This indicates the camber value of the concrete box girder, with the downward camber direction being positive.

[0012] According to the present invention, the elevation design method of the bottom formwork of a movable formwork is provided, wherein the camber value of the concrete box girder is distributed in the form of a quadratic parabola along the longitudinal direction, the control points at both ends of the parabola are located at the longitudinal support positions of the concrete box girder, and the control points in the middle of the parabola are located at the positions of the corresponding bottom formwork struts.

[0013] According to the present invention, a method for designing the bottom formwork elevation of a movable formwork is provided, wherein the camber value of the concrete box girder conforms to the following formula: In the formula, Indicates the total length of the concrete box girder; This represents the maximum camber value of the concrete box girder, which is the maximum inelastic deformation of the concrete box girder during the pre-stressing test. This indicates the distance between the control point and the longitudinal support at one end of the concrete box girder; Indicates the distance of the concrete box girder. The anti-arch value at the location.

[0014] According to the present invention, a method for designing the bottom mold elevation of a movable mold frame is provided, wherein the bottom mold elevation of the movable mold frame is calculated by the following formula: In the formula, Indicates the elevation of the bottom formwork of the movable formwork frame; Indicates the design beam bottom elevation of the movable formwork; This indicates the pre-camber during bottom formwork construction.

[0015] The present invention provides a method for designing the bottom formwork elevation of a movable formwork. Through a pre-compression test, the movable formwork is subjected to simulated load in advance. By simulating the loading process of the movable formwork during box girder construction, the elastic and inelastic deformations of the main beam frame and its auxiliary structures of the movable formwork are analyzed and verified. Based on the deformation law, the pre-camber value of the formwork and the sequence of concrete layer pouring during the construction of the movable formwork are guided, and a safe bottom formwork elevation of the movable formwork is designed to ensure the safety of the later construction of the movable formwork. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 This is a flowchart illustrating the method for designing the elevation of the bottom mold of a movable mold frame provided by the present invention.

[0018] Figure 2 This is a schematic diagram of the process for obtaining the deflection value and inelastic deformation amount of the main beam of the initial moving formwork provided by the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0020] In the description of the embodiments of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "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 the embodiments of the present 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 limitations on the embodiments of the present invention.

[0021] In embodiments of the present invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0022] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0023] The following is combined Figure 1 and Figure 2 The present invention describes the method for designing the elevation of the bottom mold of the movable mold frame.

[0024] One embodiment of the present invention provides a method for designing the elevation of the bottom mold of a movable mold frame, see [link to relevant documentation]. Figure 1 As shown, the process of designing the elevation of the bottom mold of the movable mold frame includes the following steps S1 to S5.

[0025] S1. Determine the design beam bottom elevation of the movable formwork. This step is mainly to clarify the target height of the movable formwork during construction, i.e., the design beam bottom elevation. This elevation value is determined based on the bridge design requirements and the specific conditions of the construction site.

[0026] S2. Based on the design beam bottom elevation, fabricate an initial moving formwork, conduct a pre-compression test on the initial moving formwork, and obtain the main beam deflection value and the inelastic deformation amount of the main beam.

[0027] Based on the design beam bottom elevation determined in S1, a preliminary movable formwork is constructed. Multiple observation points are set on the initial movable formwork, and the initial elevations of these points (elevations before preloading) are recorded. Precast concrete blocks are used to load and unload the movable formwork, and the elevation values ​​of each observation point at different stages (elevations after loading and after unloading) are recorded. By analyzing the elevation data after loading and unloading, the deflection value (elastic deformation) and inelastic deformation of the main beam are calculated.

[0028] S3. Determine the camber value of the concrete box girder for the initial moving formwork according to the alignment control regulations. This step involves determining the camber value of the concrete box girder based on specific alignment control standards. The camber value is an adjustment value pre-set to compensate for possible settlement or deformation during construction, and it is usually distributed in the form of a quadratic parabola.

[0029] S4. Based on the main beam deflection value, the inelastic deformation of the main beam, and the camber value of the concrete box girder, obtain the pre-camber of the bottom formwork of the movable formwork. Combining the data obtained in the previous steps (main beam deflection value, inelastic deformation value, and camber value of the concrete box girder), calculate the required pre-camber of the bottom formwork of the movable formwork. The pre-camber is the upward bending degree set in advance to ensure that the final structure reaches the design elevation.

[0030] S5. Calculate the bottom formwork elevation of the movable formwork based on the pre-camber of the bottom formwork construction and the design beam bottom elevation. Combine the pre-camber of the bottom formwork construction obtained in S4 with the initially determined design beam bottom elevation to calculate the final bottom formwork elevation of the movable formwork. This elevation value will be used to guide the formwork setting in actual construction to ensure the safety and accuracy of the bridge structure.

[0031] It is understood that the method for designing the bottom formwork elevation of the mobile formwork in this embodiment involves pre-loading the mobile formwork under simulated load through a pre-compression test. By simulating the loading process of the mobile formwork during box girder construction, the elastic and inelastic deformations of the main beam frame and its auxiliary structures of the mobile formwork are analyzed and verified. Based on the deformation law, the pre-camber value of the formwork and the sequence of concrete layer pouring during the construction of the mobile formwork are guided, and a safe bottom formwork elevation of the mobile formwork is designed to ensure the safety of the mobile formwork in the later stages of construction.

[0032] In some embodiments of the mobile formwork bottom formwork elevation design method of the present invention, see Figure 2 As shown, the process of conducting a pre-stressing test on the initial moving formwork and obtaining the deflection value and inelastic deformation of the main beam of the initial moving formwork in step S2 includes the following steps S21~S23.

[0033] S21. Conduct a no-load test on the initial moving mold frame. Set up multiple observation points on the initial moving mold frame to simulate the accurate position of the actual empty mold bed. Record the elevation values ​​of the multiple observation points as the pre-loading elevation.

[0034] The purpose of the no-load test is to determine the precise position and state of the initial moving formwork under no-load conditions. Multiple observation points are set on the initial moving formwork. These observation points should simulate the accurate position of the formwork in actual construction. The elevation values ​​of these observation points are recorded as the "pre-stressing elevation", which is an important benchmark data for subsequent deformation calculations.

[0035] S22. Conduct a simulated load test on the initial moving formwork. Use precast concrete blocks to perform preloading and unloading processes on the initial moving formwork in sequence, and record the elevation values ​​of multiple observation points, which are recorded as the elevation after loading and the elevation after unloading, respectively.

[0036] The purpose of the simulated load test is to simulate the load conditions in actual construction through loading and unloading processes to evaluate the deformation characteristics of the movable formwork. During the loading process, precast concrete blocks are used to load the initial movable formwork in stages. After each stage, the elevation values ​​of each observation point are recorded, referred to as the "post-loading elevation." Similarly, the unloading process is carried out in stages, and the elevation values ​​of each observation point are recorded, referred to as the "post-unloading elevation."

[0037] S23. Calculate the elastic deformation of the initial moving formwork based on the elevation after loading and unloading, and obtain the deflection value of the main beam of the initial moving formwork; calculate the inelastic deformation of the main beam of the initial moving formwork based on the elevation before preloading and the elevation after unloading.

[0038] It is understandable that by performing the above steps S21 to S23, the elastic and inelastic deformation of the initial moving formwork can be effectively obtained. This is crucial for ensuring construction safety and accuracy. These data will be used in subsequent steps, such as calculating the camber value of the concrete box girder and the pre-camber of the bottom formwork, thereby providing a scientific basis for the design of the moving formwork. This systematic pre-stressing test method can improve construction quality and reduce potential safety risks.

[0039] Specifically, the deflection value of the main beam of the initial moving formwork is calculated using the following formula: The inelastic deformation of the main beam of the initial moving formwork is calculated using the following formula: In the formula, This represents the initial deflection value of the main beam of the moving formwork. This represents the inelastic deformation of the main beam of the initial moving formwork. This indicates the pre-loading elevation of the observation point on the main beam; This indicates the post-loading elevation of the observation point on the main beam; This indicates the elevation of the observation point on the main beam after unloading.

[0040] It is understandable that the initial moving formwork's main beam deflection value (elastic deformation) is obtained through the formula... The calculation shows that this formula measures the difference in elevation between the loaded and unloaded states, reflecting the elastic deformation of the structure under load. This deformation is recoverable and can return to its initial state after unloading. The inelastic deformation of the main beam of the initial moving formwork is calculated using the formula... The calculation shows that this formula measures the difference between the elevation before preloading and after unloading, reflecting the irreversible deformation that occurs in the structure under load. This deformation is permanent and cannot be restored to its initial state even after unloading. Assuming the elevation before preloading is 10m, the elevation after loading is 9.95m, and the elevation after unloading is 9.97m, then the deflection value of the main beam... This indicates that the main beam bent downwards during loading (a negative value indicates a drop), and recovered some height after unloading. (Main beam inelastic deformation) This indicates that the main beam underwent some permanent deformation during loading and unloading, meaning it remained 0.03 meters lower than its initial position after unloading. The above calculations allow for an accurate assessment of the elastic and inelastic deformation of the moving formwork, providing reliable data support for subsequent pre-camber design.

[0041] In some embodiments of the mobile formwork bottom formwork elevation design method of the present invention, the multiple observation points include multiple observation points symmetrically arranged on the left and right main beams of the initial mobile formwork, multiple observation points symmetrically arranged on the left and right cantilever beams of the initial mobile formwork, multiple observation points symmetrically arranged on the bottom formwork of the initial mobile formwork, and multiple observation points symmetrically arranged on the wing formwork of the initial mobile formwork.

[0042] Understandably, in some specific examples, before the simulated load test begins, after the initial moving formwork is in place, observation points are arranged at the main beams, bottom formwork, and side formwork of the initial moving formwork. Five measuring points are set on each of the left and right main beams, for a total of 10 measuring points; five measuring points are set on each of the left and right cantilever beams, for a total of 10 measuring points; five measuring points are set on each of the left and right sides of the bottom formwork, for a total of 10 measuring points; and five measuring points are set on each of the left and right sides of the wing formwork, for a total of 10 measuring points, to observe their changes. A total of 40 measuring points are set. All observation points should be arranged as symmetrically as possible to more accurately reflect the overall deformation of the formwork and avoid data deviations caused by uneven stress on one side. The observation points should cover the main stress-bearing parts and key nodes of the formwork to ensure comprehensive acquisition of deformation information of the formwork under different working conditions. The location of the observation points should facilitate the installation and reading of measuring equipment (such as levels, total stations, etc.) to improve work efficiency and data accuracy. The same instrument and the same person shall take the readings during the observation. The elevation measured above shall be recorded for each observation, and the original data shall be kept for review. The measurement accuracy and reading error shall be ±1 mm.

[0043] The main beam is the primary component supporting the entire formwork structure. By symmetrically setting multiple observation points on the left and right main beams of the initial moving formwork to monitor the deformation of the main beams, the stress state and deformation characteristics of the entire formwork can be understood. The cantilever beam is usually used to support the formwork system and bear part of the construction load. By symmetrically setting multiple observation points on the left and right cantilever beams of the initial moving formwork, monitoring the deformation of the cantilever beam helps to assess its load-bearing capacity and stability. The bottom formwork is in direct contact with the concrete pouring surface, and its deformation directly affects the quality of the final bridge structure. By symmetrically setting multiple observation points on the wing formwork of the initial moving formwork to monitor the deformation of the bottom formwork, the pre-camber can be adjusted to ensure that the poured structure meets the design requirements. The wing formwork is mainly used for lateral support and shaping. By symmetrically setting multiple observation points on the wing formwork of the initial moving formwork to monitor its deformation, it helps to ensure the stability and accuracy of the lateral structure.

[0044] In some embodiments of the mobile formwork bottom formwork elevation design method of the present invention, the preloading process includes a three-stage loading process, with the loading loads being 0-60%, 60%-100%, and 100%-110% of the maximum construction load of the mobile formwork in sequence, and the holding time of the three-stage loading should be no less than 2h, 2h, and 8h in sequence.

[0045] Taking a 32m span for the first span as an example, preloading of the 32m span is required. The preloading of the moving formwork utilizes precast concrete blocks (1.0m × 1.2m × 0.9mm, 2.5t per block) as the preloading load. The design load is: 316.1m of design concrete for a 32m simply supported box girder. 3 The steel reinforcement consists of 57.819 tons, steel strands of 10.656 tons, and the design bulk density of C50 reinforced concrete is 2.6 t / m³. 3 The inner mold weighs 36 t, and the total weight that the movable mold frame can bear is: G 总 =G 砼 +G 钢筋 +G 钢绞线 +G 内模 +Additional weight = 316.1m 3 ×2.6t / m 3 +57.819t + 10.656t + 36t + 5t ≈ 931t. The determined preload coefficient is 110%, and its reference load is 1024 tons. The weight distribution of the concrete box girder is simulated by precast concrete blocks. The formwork is subjected to three levels of loading tests at 558.6 tons (60%), 931 tons (100%), and 1024 tons (110%), and the elevation values ​​of each measuring point are measured.

[0046] First-stage loading 0-60%: The first-stage loading is 60%. Starting from both ends of the beam, precast concrete blocks are evenly placed on the bottom formwork according to the load distribution, with the two web sides heightened, totaling 558.6 tons (224 blocks). At this point, the load is 60% of the box girder construction load state. Measurements are taken and recorded, and the stress on the moving formwork is observed. Observations are taken once every 1 hour, for a total of 2 hours. Only then can the second-stage loading be carried out.

[0047] Second-stage loading 60-100%: The second-stage loading is 100%, that is, loading precast concrete blocks (931t-558.6t=372.4t) (149 blocks), with a total weight of 931t. At this time, the loading reaches 100% of the box girder construction load state. Measurements are taken and records are recorded to observe the stress on the moving formwork. Observations are made once every 1 hour for a total of 2 hours. Only then can loading begin.

[0048] The third level of loading is 100-110%: The third level of loading is 110%. 93t (38 pieces) of precast concrete blocks are stacked in the load distribution area at both ends of the beam, with a total weight of 1024t. At this time, the loading is 110% of the box girder construction load state. Observation is carried out once every 1 hour, for a total of 8 hours. Unloading is allowed only if the deformation difference between the last two observations is less than 2mm.

[0049] All counterweights should be prepared in advance and placed in a location convenient for lifting and transportation. During loading, the loading time, tonnage, and location must be recorded in detail. The measurement team must be notified promptly for on-site monitoring. The next level of load cannot be applied without monitoring. Monitoring should be conducted, and the moving formwork should be inspected. If any abnormalities are found, loading should be stopped immediately, analyzed, and appropriate measures taken. If the measured values ​​differ significantly from the theoretical values, the cause should be analyzed before determining the next step. Throughout the loading process, unified organization and command are required. Professional technicians and responsible persons should be present on-site to coordinate. Data from all marked points must be tested after each loading level. If excessive local deformation is found, loading should be stopped, and the system should be reinforced before continuing. Loading should be carried out symmetrically in layers along both the longitudinal and transverse directions. Concentrated loading in one place is prohibited, and the loading weight error should not exceed 3%.

[0050] The pre-stressing unloading process includes a three-stage unloading process. The unloading loads are 110%~100%, 100%~60%, and 60%~0% of the maximum construction load of the moving formwork, respectively. The holding time for the three stages of unloading should be no less than 8 hours, 4 hours, and 4 hours, respectively.

[0051] After the main beam of the formwork has stabilized due to deformation, and the difference in deformation between the last two observations is less than 2mm, the preload can be removed. The unloading process is the reverse of the loading process. The unloading process should be carried out symmetrically in layers both longitudinally and laterally, and concentrated unloading at one point is prohibited. The unloading weight error should not exceed 3%. The unloading process can be carried out symmetrically from left to right, or symmetrically hoisted from left to right. The unloading of precast concrete blocks should proceed from one end to the other in layers. In short, unloading should be carried out evenly and sequentially to prevent the impact of sudden load release, and heavy objects should be properly placed to avoid affecting normal construction. The unloading process is also divided into three stages: The first stage involves unloading at a rate of 1024 to 931 tons (110% to 100%): 93 tons need to be unloaded. At this point, the unloading reaches 100% of the box girder construction load. Measurements are then taken and the stress on the moving formwork is observed. Observations are made every 2 hours, for a total of 8 hours.

[0052] The second stage of unloading is carried out at a rate of 931 to 558.6 tons (100% to 60%): 372.4 tons are unloaded. At this point, the unloading reaches 60% of the construction load of the box girder. Measurements are taken and the stress on the moving formwork is observed. Observations are taken every 2 hours, for a total of 4 hours.

[0053] The third stage of unloading is based on a load range of 435 to 0 tons (60% to 00%): 558.6 tons are unloaded. At this point, the unloading reaches 0% of the construction load of the box girder. Measurements are taken and recorded to observe the stress on the moving formwork. Observations are made every 2 hours, for a total of 4 hours.

[0054] During the unloading process, each stage of unloading must be observed and recorded before moving to the next level of load. The elastic recovery of the moving formwork must be measured and recorded. All measurement records must be submitted to the test guidance team on the same day. Any abnormalities found on site must be reported promptly.

[0055] In some embodiments of the mobile formwork bottom formwork elevation design method of the present invention, the pre-camber of the bottom formwork construction is calculated by the following formula: In the formula, This indicates the pre-camber during bottom formwork construction, with upward camber being positive. This represents the initial deflection value of the main beam of the moving formwork, with downward deflection being positive. This represents the inelastic deformation of the main beam of the initial moving formwork, with downward deformation being positive. This indicates the camber value of the concrete box girder, with the downward camber direction being positive.

[0056] Understandably, the pre-camber setting during bottom formwork construction is intended to counteract structural deformation caused by the self-weight and other loads after concrete pouring, ensuring that the final structure meets the design elevation and alignment requirements. Determining the pre-camber value is a complex process involving the comprehensive consideration of multiple factors. In this embodiment, the pre-camber during bottom formwork construction involves the main beam deflection value, the main beam inelastic deformation, and the concrete box girder camber value. The main beam deflection is the deformation caused by various loads (such as the main frame, hanging ribs, outer formwork, reinforcement, concrete, and inner formwork loads) acting on the main beam. Calculations must consider all possible loads and analyze them based on the material's elastic modulus and section properties. The inelastic deformation of the main beam is due to the inelastic properties of the material itself; irreversible deformation may occur during loading. Pre-loading tests can identify and quantify this deformation in advance, thus incorporating it into the pre-camber calculation. The camber value of the concrete box girder is the camber set according to design requirements or alignment control standards, used to compensate for settlement after concrete pouring. It is typically distributed in a parabolic or other suitable curve form to ensure the overall aesthetic appearance and functional requirements of the structure.

[0057] Suppose that in a bridge project, the deflection of the main beam at a certain observation point of the movable formwork is calculated to be 0.5m (downward) through a preloading test, the inelastic deformation of the main beam is calculated to be 0.2m (downward) through a preloading test, and the camber of the concrete box girder is 0.3m (upward). Then the precamber of the bottom formwork at the observation point can be calculated as follows: This means that when setting the bottom formwork at this observation point, a pre-camber of 0.4m needs to be added to the design beam bottom elevation to ensure that the final structure meets the design requirements. Specifically, the bottom formwork elevation of the movable formwork is calculated using the following formula: In the formula, Indicates the elevation of the bottom formwork of the movable formwork frame; Indicates the design beam bottom elevation of the movable formwork; This indicates the pre-camber of the bottom formwork. Assuming the design beam bottom elevation is +10m above the reference plane, the calculated pre-camber of the bottom formwork is 0.4m. Therefore, the final design elevation of the bottom formwork of the movable formwork needs to be increased by 0.4m based on the design beam bottom elevation of 10m, resulting in a bottom formwork elevation of 10.04m.

[0058] In bridge construction, the camber value is a downward camber pre-set during formwork installation to compensate for permanent deformation (i.e., irreversible deformation) caused by factors such as self-weight, shrinkage, and creep after concrete pouring. In some specific examples, the camber value of the concrete box girder is distributed longitudinally in the form of a quadratic parabola. The control points at both ends of the parabola are located at the longitudinal supports of the concrete box girder, and the control points in the middle of the parabola are located at the corresponding bottom formwork struts. Specifically, the camber value of the concrete box girder conforms to the following formula: In the formula, Indicates the total length of the concrete box girder; This represents the maximum camber value of the concrete box girder, which is the maximum inelastic deformation of the concrete box girder during the pre-stressing test. This indicates the distance between the control point and the longitudinal support at one end of the concrete box girder; Indicates the distance of the concrete box girder. The anti-arch value at the location.

[0059] Assume the total length of a certain concrete box girder It is 50 meters long, with the maximum anti-arch value being [missing information]. For a value of 10 mm, the anti-camber value of several control points in the middle needs to be calculated. Assuming there are three control points in the middle, located at 10 meters, 25 meters, and 40 meters from one end support respectively, then: the first control point ( The anti-camber value of this control point is: The second control point ( The anti-camber value of this control point is: The third control point ( The anti-camber value of this control point is: .

[0060] By setting the camber appropriately and fully considering various influencing factors, construction quality and structural safety can be effectively guaranteed, ensuring that the geometry and alignment of the concrete box girder meet design requirements. Setting the camber using a quadratic parabola is a simple and effective approach that can better meet the needs of actual engineering projects. In the specific implementation process, calculations and adjustments must be made strictly in accordance with design specifications to ensure that the camber value at each control point is accurate.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for designing the elevation of the bottom mold of a movable mold frame, characterized in that, include: Determine the bottom elevation of the design beam of the movable formwork; Based on the designed beam bottom elevation, an initial moving formwork is fabricated, and a pre-compression test is conducted on the initial moving formwork to obtain the main beam deflection value and the inelastic deformation amount of the main beam. The camber value of the concrete box girder of the initial moving formwork is determined according to the linear control regulations; Based on the deflection value of the main beam, the inelastic deformation of the main beam, and the camber value of the concrete box girder, the pre-camber of the bottom formwork of the movable formwork is obtained. The elevation of the bottom formwork of the movable formwork is calculated based on the pre-camber of the bottom formwork construction and the design beam bottom elevation.

2. The method for designing the elevation of the bottom mold of a movable mold frame according to claim 1, characterized in that, A pre-stressing test was conducted on the initial moving formwork to obtain the deflection value and inelastic deformation of the main beam of the initial moving formwork, including: An unloaded test was conducted on the initial moving mold frame. Multiple observation points were set on the initial moving mold frame to simulate the accurate position of the actual empty mold bed. The elevation values ​​of the multiple observation points were recorded as the pre-loading elevation. A simulated surcharge test was conducted on the initial moving formwork. Precast concrete blocks were used to perform a preloading and unloading process on the initial moving formwork in sequence, and the elevation values ​​of multiple observation points were recorded, which were respectively recorded as the elevation after loading and the elevation after unloading. The elastic deformation of the initial moving formwork is calculated based on the post-loading elevation and the post-unloading elevation to obtain the deflection value of the main beam of the initial moving formwork; the inelastic deformation of the main beam of the initial moving formwork is calculated based on the pre-loading elevation and the post-unloading elevation.

3. The method for designing the elevation of the bottom mold of the movable mold frame according to claim 2, characterized in that, The deflection value of the main beam of the initial moving formwork is calculated using the following formula: ; The inelastic deformation of the main beam of the initial moving formwork is calculated using the following formula: ; In the formula, This represents the initial deflection value of the main beam of the moving formwork. This represents the inelastic deformation of the main beam of the initial moving formwork. This indicates the pre-loading elevation of the observation point on the main beam; This indicates the post-loading elevation of the observation point on the main beam; This indicates the elevation of the observation point on the main beam after unloading.

4. The method for designing the elevation of the bottom mold of the movable mold frame according to claim 2, characterized in that, The multiple observation points include multiple observation points symmetrically arranged on the left and right main beams of the initial moving formwork, multiple observation points symmetrically arranged on the left and right cantilever beams of the initial moving formwork, multiple observation points symmetrically arranged on the bottom template of the initial moving formwork, and multiple observation points symmetrically arranged on the wing template of the initial moving formwork.

5. The method for designing the elevation of the bottom mold of a movable mold frame according to claim 2, characterized in that, The preloading process includes a three-stage loading process, with the loading loads being 0-60%, 60%-100%, and 100%-110% of the maximum construction load of the movable formwork, respectively. The holding times for the three stages of loading should be no less than 2 hours, 2 hours, and 8 hours, respectively. The pre-loading unloading process includes a three-stage unloading process, with the unloading loads being 110%~100%, 100%~60%, and 60%~0% of the maximum construction load of the movable formwork, respectively. The holding times for the three stages of unloading should be no less than 8 hours, 4 hours, and 4 hours, respectively.

6. The method for designing the elevation of the bottom mold of a movable mold frame according to claim 5, characterized in that, During the pre-loading process, loading is performed symmetrically in layers along the longitudinal and transverse directions of the initial moving mold frame. During the pre-loading unloading process, unloading is performed symmetrically in layers along the longitudinal and transverse directions of the initial moving mold frame.

7. The method for designing the elevation of the bottom mold of a movable mold frame according to any one of claims 1 to 6, characterized in that, The pre-camber of the bottom formwork construction is calculated using the following formula: In the formula, This indicates the pre-camber during bottom formwork construction, with upward camber being positive. This represents the initial deflection value of the main beam of the moving formwork, with downward deflection being positive. This represents the inelastic deformation of the main beam of the initial moving formwork, with downward deformation being positive. This indicates the camber value of the concrete box girder, with the downward camber direction being positive.

8. The method for designing the elevation of the bottom mold of a movable mold frame according to claim 7, characterized in that, The camber value of the concrete box girder is distributed in the form of a quadratic parabola along the longitudinal direction. The control points at both ends of the parabola are located at the longitudinal support positions of the concrete box girder, and the control points in the middle of the parabola are located at the positions of the corresponding bottom formwork support rods.

9. The method for designing the elevation of the bottom mold of a movable mold frame according to claim 8, characterized in that, The camber value of the concrete box girder conforms to the following formula: In the formula, Indicates the total length of the concrete box girder; This represents the maximum camber value of the concrete box girder, which is the maximum inelastic deformation of the concrete box girder during the pre-stressing test. This indicates the distance between the control point and the longitudinal support at one end of the concrete box girder; Indicates the distance of the concrete box girder. The anti-arch value at the location.

10. The method for designing the elevation of the bottom mold of a movable mold frame according to any one of claims 1 to 6, characterized in that, The elevation of the bottom mold of the movable mold frame is calculated using the following formula: In the formula, Indicates the elevation of the bottom formwork of the movable formwork frame; Indicates the design beam bottom elevation of the movable formwork; This indicates the pre-camber during bottom formwork construction.

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