Calculation method of vertical jack loading control value for steel fiber reinforced pipe segment bending

Abstract

The invention relates to the technical field of tunnel engineering, and in particular to a method for calculating a vertical jack loading control value for compression bending of a reinforced steel fiber prefabricated pipe segment. A standard pipe segment is selected and its geometric parameters are determined, and a two-dimensional load structure model is constructed according to the geometric parameters. It is assumed that the vertical displacement generated at the mid-span of the pipe segment under the action of the load is zero, and a simplified vertical jack loading control value is obtained through a vertical jack loading value calculation formula. The simplified vertical jack loading control value is adjusted through the two-dimensional load structure model to obtain an accurate vertical jack loading control value, which can avoid tedious calculations and ensure that the test truly reflects the bearing mode of the pipe segment under construction conditions.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel engineering, and in particular to a method for calculating a loading control value of a vertical jack for bending a reinforced steel fiber prefabricated pipe segment. Background Art

[0002] The shield construction method is an advanced technology widely used in tunnel construction. The tunnel boring machine simultaneously constructs and lays the tunnel lining, i.e. the "shield" or supporting segments, during the tunneling process. This method not only improves the construction efficiency, but also ensures the stability and safety of the tunnel. In the bearing capacity test of reinforced steel fiber concrete segments, correctly determining the loading control value of the vertical jack is one of the key steps. The precise control of the vertical jack loading value is also related to the safety and reliability of the actual project. Therefore, finding an efficient and accurate calculation method is of great significance to improving the test efficiency and ensuring the quality of the project.

[0003] At present, the determination method of the vertical jack loading control value of reinforced steel fiber prefabricated pipe segments in my country is mainly based on Appendix C of the Technical Specification for Reinforced Steel Fiber Concrete Pipe Segments (T / CECS 1374-2023) of the China Association for Engineering Construction Standardization. The specification calculates the loading control values ​​of horizontal and vertical jacks based on the axial force design value and bending moment design value of the basic combination. In these calculations, the determination of the loading value of the vertical jack is affected by the uncertainty of the vertical displacement. This uncertainty makes the calculation of the loading control value of the vertical jack complicated. In order to avoid tedious calculations and ensure that the test truly reflects the bearing mode of the pipe segment under construction conditions, it is urgent to propose a calculation method for the vertical jack loading control value of reinforced steel fiber prefabricated pipe segments, and to improve the operating efficiency of engineers by simplifying the calculation process. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a calculation method for the vertical jack loading control value of the compression bending of reinforced steel fiber prefabricated pipe segments. Based on relevant specifications, the calculation process is simplified, while ensuring that the test truly reflects the bearing mode of the pipe segment under construction conditions and improves the operating efficiency of engineers.

[0005] The present invention provides a method for calculating a vertical jack loading control value for bending a reinforced steel fiber prefabricated pipe segment, comprising the following steps:

[0006] S1. Select a standard segment and determine its geometric parameters, and construct a two-dimensional load structure model based on the geometric parameters;

[0007] S2. Assuming that the vertical displacement of the mid-span of the segment under load is zero, the simplified vertical jack loading control value is obtained through the vertical jack loading value calculation formula;

[0008] S3. Through the two-dimensional load structure model, the simplified vertical jack loading control value is adjusted to obtain the accurate vertical jack loading control value.

[0009] Furthermore, the geometric parameters in S1 specifically include:

[0010] The distance from the center of the horizontal support to the centroid of the cross section at the center of the segment, the span of the segment, and the deadweight of the segment.

[0011] Furthermore, the S2 specifically includes:

[0012] S21. Simulate the working condition of the whole ring segment through the two-dimensional load structure model, and obtain the bending moment value and axial force according to the simulation results, and obtain the eccentricity according to the bending moment value and axial force;

[0013] S22. Combine the eccentricity and bending moment values ​​and use the internal force balance formula to calculate the loading control value of the horizontal jack;

[0014] S23. Assume that the vertical displacement generated at the mid-span of the segment under the action of load is zero, and substitute it, the geometric parameters, the eccentricity, and the loading control value of the horizontal jack into the vertical jack loading value calculation formula to obtain a simplified vertical jack loading control value.

[0015] Furthermore, the loading control value of the horizontal jack and the simplified vertical jack loading control value are input into the two-dimensional load structure model to obtain the maximum bending moment internal force value of the segment.

[0016] Further, the step S3, adjusting the simplified vertical jack loading control value to obtain the accurate vertical jack loading control value, specifically includes:

[0017] S31, inputting the loading control value of the horizontal jack and the simplified vertical jack into the two-dimensional load structure model, and calculating the maximum bending moment internal force value of the segment;

[0018] S32, adjusting the simplified vertical jack loading control value, and recalculating the maximum bending moment internal force value of the segment, and determining whether the difference between the maximum bending moment internal force value of the segment and the bending moment value is less than a preset threshold;

[0019] S33. If the difference between the maximum bending moment internal force value of the segment and the bending moment value is less than a preset threshold, confirm that the current vertical jack loading control value is an accurate vertical jack loading control value; otherwise, return to S32 to repeat the calculation and judgment process.

[0020] Furthermore, the vertical jack loading value calculation formula is:

[0021] ;

[0022] Among them, F represents the vertical jack loading value; P represents the horizontal jack loading value; H represents the distance from the center of the horizontal support to the centroid of the cross section at the center of the segment; e represents the eccentricity; l represents the span of the segment; G1 represents the deadweight of the segment; Represents the vertical displacement of the mid-span of the segment under load.

[0023] Furthermore, the internal force balance formula is:

[0024] P = M / e;

[0025] P represents the loading control value of the horizontal jack; e represents the eccentricity; M represents the bending moment value.

[0026] The embodiments of the present invention have the following technical effects:

[0027] 1. By assuming that the vertical displacement generated in the mid-span of the segment under the action of load is zero, the simplified vertical jack loading control value is obtained through the vertical jack loading value calculation formula, and the simplified vertical jack loading control value is adjusted to obtain the precise vertical jack loading control value instead of the vertical displacement integral calculation, which can avoid a large number of integral calculations and ensure that the test truly reflects the bearing mode of the segment under construction conditions.

[0028] 2. By combining the simplified vertical jack loading control value with the actual working condition model, a more accurate vertical jack loading value can be obtained to ensure the safety and stability of the segment structure in actual application.

[0029] 3. Using a two-dimensional load structure model to adjust the simplified loading control value helps to optimize the design, reduce errors, and make the calculation results closer to the actual situation.

[0030] 4. This method is applicable to different types of reinforced steel fiber segments and various working conditions, which helps to be effectively applied in different engineering environments and increases the adaptability and flexibility of engineering design. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 It is a flow chart of a method for determining a vertical jack loading control value for bending a reinforced steel fiber prefabricated pipe segment provided by an embodiment of the present invention;

[0033] Figure 2This is a cross-sectional dimension diagram of a standard steel fiber tunnel segment in a certain subway section provided by an embodiment of the present invention;

[0034] Figure 3 It is a schematic diagram of a two-dimensional load structure model of a standard block segment of a reinforced steel fiber tunnel in a certain subway section provided by an embodiment of the present invention;

[0035] Figure 4 It is a diagram of segment bending moment internal force values ​​when a simplified vertical jack loading control value is input, provided in an embodiment of the present invention;

[0036] Figure 5 It is a diagram of the internal force values ​​of the bending moment of the pipe segment when the adjusted vertical jack loading control value is inputted, as provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0038] Figure 1 The flowchart of the method for determining the vertical jack loading control value of the steel fiber prefabricated pipe segment bending provided by the embodiment of the present invention. Figure 1 , including:

[0039] S1. Select a standard segment and determine its geometric parameters, and construct a two-dimensional load structure model based on the geometric parameters;

[0040] Furthermore, the geometric parameters in S1 specifically include:

[0041] The distance from the center of the horizontal support to the centroid of the cross section at the center of the segment, the span of the segment, and the deadweight of the segment.

[0042] In some embodiments, constructing a two-dimensional load structure model includes: establishing a model framework, defining the boundary conditions of the model according to the span of the segment, setting the support points and loading points of the segment; setting the load,

[0043] The deadweight of the segment is applied to the model, usually as a uniformly distributed load acting on the length of the segment. According to the position of the horizontal support, the corresponding support conditions are set to simulate the actual support state. The geometric parameters are input, and the distance from the center of the horizontal support to the centroid of the cross section at the center of the segment is used to determine the load application position and force distribution. The actual geometric dimensions of the segment are input into the model to ensure that the model can accurately simulate the actual shape and size of the segment.

[0044] S2. Assuming that the vertical displacement of the mid-span of the segment under load is zero, the simplified vertical jack loading control value is obtained through the vertical jack loading value calculation formula;

[0045] Further, it specifically includes:

[0046] S21. Simulate the working condition of the whole ring segment through the two-dimensional load structure model, and obtain the bending moment value and axial force according to the simulation results, and obtain the eccentricity according to the bending moment value and axial force;

[0047] S22. Combine the eccentricity and bending moment values ​​and use the internal force balance formula to calculate the loading control value of the horizontal jack;

[0048] Furthermore, the internal force balance formula is:

[0049] P = M / e;

[0050] P represents the loading control value of the horizontal jack; e represents the eccentricity; M represents the bending moment value.

[0051] S23. Assume that the vertical displacement generated at the mid-span of the segment under the action of load is zero, and substitute it, the geometric parameters, the eccentricity, and the loading control value of the horizontal jack into the vertical jack loading value calculation formula to obtain a simplified vertical jack loading control value.

[0052] Furthermore, the vertical jack loading value calculation formula is:

[0053] ;

[0054] Among them, F represents the vertical jack loading value; P represents the horizontal jack loading value; H represents the distance from the center of the horizontal support to the centroid of the cross section at the center of the segment; e represents the center distance; l represents the span of the segment; G1 represents the deadweight of the segment; Represents the vertical displacement of the mid-span of the segment under load.

[0055] It is worth explaining that due to the uncertainty of ΔV in the above calculation formula of vertical jack loading value, it is not easy to determine the vertical jack loading control value F. In view of this, three solutions are proposed:

[0056] 1. Apply the virtual force principle to derive ΔV. The general formula is: ; However, the amount of integral calculation is huge and often takes a lot of time to derive, so it is not suitable for use.

[0057] 2. Assuming ΔV is zero, use the formula to calculate the vertical jack loading value, establish a two-dimensional load model, and adjust the vertical jack loading value several times to make the maximum bending moment internal force value of the segment consistent with the bearing bending moment design value. The vertical loading value used at this time is the precise control value of the vertical jack loading. This method can be easily mastered by engineers with the help of computer-assisted calculations.

[0058] 3. Assuming ΔV is zero, the simplified control value of the vertical jack loading is calculated directly using the formula. This method is simple and can be used to roughly estimate the control value of the vertical jack loading of the segment, but it is also safer and more conservative.

[0059] Therefore, ideas 2 and 3 are adopted to determine the vertical jack loading control value.

[0060] S3. Through the two-dimensional load structure model, the simplified vertical jack loading control value is adjusted to obtain the accurate vertical jack loading control value.

[0061] Furthermore, the loading control value of the horizontal jack and the simplified vertical jack loading control value are input into the two-dimensional load structure model to obtain the maximum bending moment internal force value of the segment.

[0062] Further, in S3, the simplified vertical jack loading control value is adjusted to obtain the accurate vertical jack loading control value, which specifically includes:

[0063] S31, inputting the loading control value of the horizontal jack and the simplified vertical jack into the two-dimensional load structure model, and calculating the maximum bending moment internal force value of the segment;

[0064] Specifically, inputting the known horizontal jack loading control value and the simplified vertical jack loading control value into the two-dimensional load structure model will generate a maximum bending moment internal force value of the segment, which reflects the stress state of the segment under a given load.

[0065] S32, adjusting the simplified vertical jack loading control value, and recalculating the maximum bending moment internal force value of the segment, and determining whether the difference between the maximum bending moment internal force value of the segment and the bending moment value is less than a preset threshold;

[0066] S33. If the difference between the maximum bending moment internal force value of the segment and the bending moment value is less than a preset threshold, confirm that the current vertical jack loading control value is an accurate vertical jack loading control value; otherwise, return to S32 to repeat the calculation and judgment process.

[0067] It is worth noting that according to the calculation results of the maximum bending moment internal force value of the segment, the loading control value of the vertical jack needs to be adjusted to make the calculated internal force value closer to the target value (i.e. the required bending moment value). The adjustment process will continue until the difference between the calculated bending moment value and the target bending moment value is less than a preset threshold. If the final calculation result meets the set accuracy requirements (i.e. the difference is less than the preset threshold), the current vertical jack loading control value is confirmed to be an accurate value. If the accuracy requirements are not met, it is necessary to return to the adjustment step, readjust the loading control value of the vertical jack, and repeat the calculation and judgment process until the accuracy requirements are met.

[0068] This method can accurately determine the loading control value of the vertical jack, thereby improving the accuracy of the structural model calculation; it can better adapt to the actual load conditions, optimize the structural design, and avoid engineering problems caused by inaccurate load calculation; this method allows dynamic adjustment of the loading control value of the vertical jack to achieve precise load conditions, enhancing the adaptability and accuracy of the model.

[0069] For example, taking a standard steel fiber tunnel segment of a subway section as an example, the segment section dimensions are as follows: Figure 2 As shown, l =3250cm, the outer ring radius is: 3100cm, the inner ring radius is: 2750cm, the curvature of the segment is 67.5°, the distance from the center of the horizontal support to the centroid of the cross section at the center of the segment is H=493cm, and the ring width is 1.2m.

[0070] Calculate the self-weight of the segment G1 = 3.14 × (3.1 2 -2.75 2 )×67.5 / 360×1.2×25=36.16KN

[0071] Establish a two-dimensional load structure model, such as Figure 3 shown.

[0072] Calculated bending moment value M=216.91KN•m, axial force N=1109.28KN, eccentricity e=M / N=216.91 / 1109.28=0.196m;

[0073] Use the internal force balance formula to calculate the loading control value of the horizontal jack: P=N=1109.28KN;

[0074] Assuming that the vertical displacement Δv generated at the mid-span of the segment under load is 0, the simplified vertical jack loading control value F0 is obtained through the vertical jack loading value calculation formula;

[0075] ;

[0076] Input P=1109.28KN, F0=691.94KN into the two-dimensional load structure model to obtain the segment bending moment internal force value diagram, as shown in Figure 4 As shown, at this time, the maximum bending moment internal force value M 0max =257.67KN•m>M=216.91KN•m, set the preset threshold to 0.5KN•m.

[0077] Considering keeping the P value unchanged and appropriately reducing the F value, after several trial calculations, F1=653KN is taken. At this time, the segment bending moment internal force value diagram is as follows: Figure 5 As shown, the maximum bending moment internal force value M in the segment 1max =216.62 KN•m, |M 1max -M|=|216.62-216.91|KN•m=0.29KN•m<0.5KN•m, so at this time the vertical jack loading control value of the segment F1=653KN is the precise control value of the vertical jack loading of the segment.

[0078] If you want to roughly estimate the vertical jack loading control value of the segment, and be safer and more conservative, you can assume that the vertical displacement Δv=0 generated at the mid-span of the segment under the action of load. Through the vertical jack loading value calculation formula, you can get the simplified vertical jack loading control value F0. Generally, the maximum bending moment internal force value obtained in the segment at this time is 15% to 20% larger than the segment bearing bending moment value.

[0079] The present invention assumes that the vertical displacement of the mid-span of the segment under load is zero, uses a formula to calculate the simplified vertical jack loading control value, establishes a two-dimensional load model, and adjusts the vertical jack loading value several times to make the maximum bending moment internal force value of the segment consistent with the bearing bending moment design value. The vertical loading value used at this time is the vertical jack loading precise control value. The method for determining the vertical jack loading control value for the bending of the reinforced steel fiber prefabricated segment proposed in the present invention can roughly estimate the vertical jack loading control value and obtain the vertical jack loading precise control value. By cleverly utilizing and deferring the provisions of relevant specifications, the complex mid-span deflection integral calculation is effectively avoided, and the calculation efficiency is significantly improved. At the same time, it ensures that the test design can truly simulate the segment force mode under the construction and use conditions, providing a more practical evaluation method for engineering practice. Moreover, the determination method is not only simple to operate and easy for engineers to master and apply, but also greatly saves time costs, providing strong support for the quality control and safety assessment of prefabricated segments.

[0080] It should be noted that the terms used in the present invention are only for describing specific embodiments, rather than limiting the scope of the present application. As shown in the present specification, unless the context clearly indicates an exception, the words "one", "a", "a kind of" and / or "the" do not specifically refer to the singular, but may also include the plural. The terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method or device. In the absence of more restrictions, the elements defined by the sentence "include one..." do not exclude the presence of other identical elements in the process, method or device including the elements.

[0081] It should also be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. Unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", etc. should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention.

Claims

1. A method for calculating the control value of the vertical jack loading for bending of reinforced steel fiber prefabricated segments, characterized in that: The steps include: S1. Select a standard segment and determine its geometric parameters, and construct a two-dimensional load structure model based on the geometric parameters; S2. Assuming that the vertical displacement of the mid-span of the segment under load is zero, the simplified vertical jack loading control value is obtained through the vertical jack loading value calculation formula; S21. Simulate the working condition of the whole ring segment through the two-dimensional load structure model, and obtain the bending moment value and axial force according to the simulation results, and obtain the eccentricity according to the bending moment value and axial force; S22. Combine the eccentricity and bending moment values ​​and use the internal force balance formula to calculate the loading control value of the horizontal jack; S23, assuming that the vertical displacement of the mid-span of the segment under the action of the load is zero, and bringing it, the geometric parameter, the eccentricity, and the loading control value of the horizontal jack into the vertical jack loading value calculation formula to obtain a simplified vertical jack loading control value; The vertical jack loading value calculation formula is: ； Among them, F represents the vertical jack loading value; P represents the horizontal jack loading value; H represents the distance from the center of the horizontal support to the centroid of the cross section at the center of the segment; e represents the eccentricity; l represents the span of the segment; G1 represents the deadweight of the segment; Represents the vertical displacement of the mid-span of the segment under load; S3. By using the two-dimensional load structure model, the simplified vertical jack loading control value is adjusted to obtain the accurate vertical jack loading control value; S31, inputting the loading control value of the horizontal jack and the simplified vertical jack into the two-dimensional load structure model, and calculating the maximum bending moment internal force value of the segment; S32, adjusting the simplified vertical jack loading control value, and recalculating the maximum bending moment internal force value of the segment, and determining whether the difference between the maximum bending moment internal force value of the segment and the bending moment value is less than a preset threshold; S33. If the difference between the maximum bending moment internal force value of the segment and the bending moment value is less than a preset threshold, confirm that the current vertical jack loading control value is an accurate vertical jack loading control value; otherwise, return to S32 to repeat the calculation and judgment process.

2. The method for calculating the control value of the vertical jack loading for bending of reinforced steel fiber prefabricated segments according to claim 1 is characterized in that: The geometric parameters in S1 specifically include: The distance from the center of the horizontal support to the centroid of the cross section at the center of the segment, the span of the segment, and the deadweight of the segment.

3. The method for calculating the vertical jack loading control value for bending of reinforced steel fiber prefabricated segments according to claim 1 is characterized in that: The internal force balance formula is: P = M / e; P represents the loading control value of the horizontal jack; e represents the eccentricity; M represents the bending moment value.

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