Variable-curvature vertical curve pushing fulcrum elevation adjustment optimization method

Abstract

The invention relates to a variable-curvature vertical curve pushing fulcrum elevation adjustment optimization method, which comprises the following steps of: taking a bridge midline design datum line as an x axis, and taking a pushing advancing direction as an x-axis positive direction; the vertical direction is used as the z axis, the vertical upward direction is used as the z axis positive direction, the x coordinate represents the longitudinal position of the pushing beam, and the z coordinate represents the distance of the pushing beam deviating from the design datum line; the optimization method comprises the following steps: S1, smooth incremental analysis calculation; s2, fulcrum elevation adjustment; and S3, fulcrum elevation adjustment and integration. According to the method, optimization analysis can be quickly carried out according to existing incremental launching beam body parameters, so that the calculation cost is remarkably reduced, the calculated fulcrum elevation adjustment amount is smaller, and the economic benefit and the construction efficiency are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of bridge construction, and in particular relates to an optimization method for adjusting the elevation of a jacking support point on a variable curvature vertical curve. Background Art

[0002] The walking jacking method is a commonly used construction method for erecting main beams in bridge construction. It has the advantages of high mechanization and short construction period. It is more widely used when there are many restrictions on the temporary pier spacing, such as when there are navigation requirements and when crossing existing lines. In order to meet the requirements that the bridge line shape is a vertical curve with constant curvature or the beam body has a variable height, the line shape of the bottom surface of the beam body has been mostly a vertical curve with variable curvature in recent years.

[0003] During the jacking construction process, when the vertical curve of the main beam is a straight line, the elevation of the top surface of the support is consistent with the corresponding elevation of the stress-free line of the bottom surface of the beam, and the force form is continuous beam force; while in the process of jacking the vertical curve beam with variable curvature using the walking jacking method, there will be a deviation between the elevation of the top surface of the support and the corresponding elevation of the stress-free line of the bottom surface of the beam. If the elevation of the support is not adjusted, the reaction force of the temporary pier support will be too large.

[0004] Therefore, in order to ensure the force safety during the jacking process, the fulcrum elevation adjustment must be carried out during the jacking process of the variable curvature vertical curved beam. At present, the methods for determining the fulcrum elevation adjustment plan are: exhaustive method, trial method, and single-step modulus search synthesis method. Among them, the exhaustive method forms a fulcrum elevation adjustment plan matrix according to the excess of the support reaction force, and adjusts the fulcrum elevation, but the calculation amount increases by orders of magnitude, the obtained fulcrum elevation adjustment amount is large, and the economic benefit is not significant; the trial method requires engineers to have rich experience and structural mechanics knowledge; the single-step modulus search synthesis method proposes the concept of elevation modulus, and adopts the idea of ​​first single modulus search and then maximum merging to obtain the fulcrum elevation adjustment plan. Although the calculation amount is reduced compared with the exhaustive method, the obtained fulcrum elevation adjustment amount is still large.

[0005] Therefore, it is necessary to propose an optimization method for adjusting the elevation of the jacking support point of a variable curvature vertical curve, so as to quickly obtain the most cost-effective adjustment plan for the elevation of the support point. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for optimizing the elevation adjustment of the jacking support point of a variable curvature vertical curve, which can quickly perform optimization analysis based on the existing jacking beam parameters, significantly reduce the calculation cost, and make the calculated fulcrum elevation adjustment amount smaller, thereby improving economic benefits and construction efficiency.

[0007] The present invention solves the technical problem by the following technical solutions:

[0008] A method for optimizing the elevation adjustment of the jacking support point of a variable curvature vertical curve, characterized in that: the method takes the bridge centerline design reference line as the x-axis, and the jacking forward direction as the positive direction of the x-axis; takes the vertical direction as the z-axis, and the vertical upward direction as the positive direction of the z-axis, the x-coordinate represents the longitudinal position of the jacking beam, and the z-coordinate represents the distance from the design reference line; the steps of the optimization method are:

[0009] S1. Smooth jacking analysis and calculation: Starting from the longitudinal position corresponding to the first jacking condition, the finite element software is used to establish a bridge jacking construction model, and the programming software is used to call the finite element software for rapid analysis, and the support reaction force value, stress value and support point elevation value of the current calculation condition gk jacking parameter are calculated. If the constraint conditions are met, the next jacking condition gk+1 calculation is performed until all jacking conditions are calculated; if the constraint conditions are not met, jump to the next step;

[0010] S2. Adjustment of temporary pier support elevation: if the current calculation condition does not meet the constraint conditions, enter the support elevation adjustment module, start adjusting the support elevation of the previous calculation condition gk-1 of the calculation condition, and record the calculation condition D(i)=gk and the adjustment condition number A(i)=gk-1 of the top-pushing beam body that does not meet the constraint conditions, and correct the existing support elevation according to the support elevation adjustment plan. In addition to meeting the structural force safety requirements of the adjustment condition and the condition immediately following it, the support elevation adjustment plan should also ensure that the support elevation is minimized. After the support elevation is adjusted once, if the two conditions do not meet the constraint conditions, the next support elevation adjustment is performed; if the constraint conditions are met, the next top-pushing condition gk+1 calculation is performed;

[0011] S3. Integration of temporary pier support elevation adjustment: After all the jacking conditions are calculated, the support elevation adjustment plan is integrated. The integrated support elevation adjustment aims to minimize the number of adjustments under the premise of the total adjustment amount. The j-th longitudinal position support elevation adjustment plan and the j+1-th support elevation adjustment plan are merged in sequence. The elevation is corrected according to the merged support elevation adjustment vector, and the support elevation adjustment gk is calculated. H (j) Structural force analysis: if the constraint conditions are not met, the next fulcrum elevation adjustment plan is integrated; if the constraint conditions are met, the fulcrum elevation adjustment plan is integrated once and forms the final fulcrum elevation adjustment. At this time, the total fulcrum elevation adjustment amount m is the smallest and the number of adjustments k is the least.

[0012]

[0013] Where: E represents the elevation of the jacking support point under each jacking calculation condition during the whole jacking process; R i Represents the reaction force of fulcrum i#; [R i ] represents the allowable support reaction force of the fulcrum i#; σ G represents the maximum stress of each section of the beam; [σG ] represents the allowable stress of the beam; σ D represents the maximum stress of each cross section of the guide beam; [σ D ] represents the allowable stress of the guide beam; Indicates the lowest elevation of each support point, h i Indicates the top elevation of each support point. Indicates the highest elevation of each support point.

[0014] Moreover, the elevation adjustment principle of the temporary pier support point of S2 is controlled by the support point reaction force limit. The support point position is adjusted vertically downward to reduce the reaction force borne by the pier; the support point position near the pier is adjusted upward to share the excess support point force, and then the support point elevation is adjusted to make the structure force safe and reasonable.

[0015] Moreover, the support elevation adjustment module of S2 uses the main program to call the finite element model of the pushing process for calculation based on the main beam pushing parameters. When the structural force safety does not meet the requirements at a certain pushing stage, the temporary pier support elevation is adjusted and optimized, and the support elevation optimization results are stored.

[0016] The advantages and beneficial effects of the present invention are:

[0017] 1. Compared with the exhaustive method for determining the elevation adjustment scheme of the fulcrum of the vertical curved beam with variable curvature for jacking, the present invention significantly reduces the required basic data and calculation time, and the obtained fulcrum elevation adjustment method has good economic benefits; compared with the trial calculation method for determining the elevation adjustment scheme of the fulcrum of the vertical curved beam with variable curvature for jacking, it is not necessary for engineering personnel to have a comprehensive understanding and rich experience in the mechanical properties of the main beam jacking process.

[0018] 2. The fulcrum elevation adjustment optimization method of the present invention is based on "first accurately optimizing the fulcrum elevation adjustment for the over-limit pier, and then integrating the fulcrum elevation adjustment plan". The concept is clear, the process is feasible, and it is easy to implement through programming, and the fulcrum elevation adjustment plan of the jacking beam can be quickly obtained.

[0019] 3. The present invention combines MATLAB and ANSYS to optimize the fulcrum elevation of the variable curvature vertical curve steel box girder. The MATLAB data processing function and the convenience of ANSYS parametric modeling can be used to analyze the steel box girder jacking process and the fulcrum elevation adjustment optimization analysis, which greatly improves the intelligent calculation. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a flow chart of the present invention;

[0021] Figure 2 This is a schematic diagram of the structure of the fulcrum elevation adjustment program module of the present invention;

[0022] Figure 3 A schematic diagram of a pre-camber curve of a steel box girder according to an embodiment of the present invention;

[0023] Figure 4 It is a schematic diagram of the top pushing construction arrangement of an embodiment of the present invention;

[0024] Figure 5 A finite element model of a steel box girder according to an embodiment of the present invention;

[0025] Figure 6 It is a temporary pier support reaction diagram after the support point elevation is optimized in an embodiment of the present invention. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below through specific examples. The following examples are only illustrative and not restrictive, and the protection scope of the present invention cannot be limited thereto.

[0027] Figure 1 The present invention is a flow chart of the method for optimizing the fulcrum elevation adjustment during the entire jacking process. Figure 2 This is the module structure of the fulcrum elevation adjustment program described in the present invention.

[0028] A method for optimizing the elevation adjustment of the jacking support point of a variable curvature vertical curve is innovative in that: the method takes the bridge centerline design reference line as the x-axis, and the jacking forward direction as the positive direction of the x-axis; takes the vertical direction as the z-axis, and the vertical upward direction as the positive direction of the z-axis, the x-coordinate represents the longitudinal position of the jacking beam, and the z-coordinate represents the distance from the design reference line; the steps of the optimization method are:

[0029] S1. Smooth jacking analysis and calculation: Starting from the longitudinal position corresponding to the first jacking condition, the finite element software is used to establish a bridge jacking construction model, and the programming software is used to call the finite element software for rapid analysis, and the support reaction force value, stress value and support point elevation value of the current calculation condition gk jacking parameter are calculated. If the constraint conditions are met, the next jacking condition gk+1 calculation is performed until all jacking conditions are calculated; if the constraint conditions are not met, jump to the next step;

[0030] S2. Adjustment of temporary pier support elevation: if the current calculation condition does not meet the constraint conditions, enter the support elevation adjustment module, start adjusting the support elevation of the previous calculation condition gk-1 of the calculation condition, and record the calculation condition D(i)=gk and the adjustment condition number A(i)=gk-1 of the top-pushing beam body that does not meet the constraint conditions, and correct the existing support elevation according to the support elevation adjustment plan. In addition to meeting the structural force safety requirements of the adjustment condition and the condition immediately following it, the support elevation adjustment plan should also ensure that the support elevation is minimized. After the support elevation is adjusted once, if the two conditions do not meet the constraint conditions, the next support elevation adjustment is performed; if the constraint conditions are met, the next top-pushing condition gk+1 calculation is performed;

[0031] S3. Integration of temporary pier support elevation adjustment: After all the jacking conditions are calculated, the support elevation adjustment plan is integrated. The integrated support elevation adjustment aims to minimize the number of adjustments under the premise of the total adjustment amount. The j-th longitudinal position support elevation adjustment plan and the j+1-th support elevation adjustment plan are merged in sequence. The elevation is corrected according to the merged support elevation adjustment vector, and the support elevation adjustment gk is calculated. H (j) Structural force analysis: if the constraint conditions are not met, the next fulcrum elevation adjustment plan is integrated; if the constraint conditions are met, the fulcrum elevation adjustment plan is integrated once and forms the final fulcrum elevation adjustment. At this time, the total fulcrum elevation adjustment amount m is the smallest and the number of adjustments k is the least.

[0032]

[0033] Where: E represents the elevation of the jacking support point under each jacking calculation condition during the whole jacking process; R i Represents the reaction force of fulcrum i#; [R i ] represents the allowable support reaction force of the fulcrum i#; σ G represents the maximum stress of each section of the beam; [σ G ] represents the allowable stress of the beam; σ D represents the maximum stress of each cross section of the guide beam; [σ D ] represents the allowable stress of the guide beam; Indicates the lowest elevation of each support point, h i Indicates the top elevation of each support point. Indicates the highest elevation of each support point.

[0034] The elevation adjustment principle of the temporary pier support point of S2 is controlled by the support point reaction limit. The support point position is adjusted vertically downward to reduce the reaction force borne by the pier; the support point position near the pier is adjusted upward to share the excess support point bearing force, and then the support point elevation is adjusted to make the structure force safe and reasonable.

[0035] The support elevation adjustment module of S2 uses the main program to call the finite element model of the pushing process for calculation based on the main beam pushing parameters. When the structural force safety does not meet the requirements at a certain pushing stage, the temporary pier support elevation is adjusted and optimized, and the support elevation optimization results are stored.

[0036] The embodiment of the present invention is based on a bridge in Tianjin, which is a bottom-supported simply supported steel box tied arch bridge with a single span of 410m. The main beam is a steel box beam. There are 45 standard segments of the main beam, and the standard segment length is 9m. The designed bridge line shape of the steel box beam is a two-way slope with a slope of 3.5%, and the designed stress-free line shape is a variable curvature vertical curve, in which the maximum pre-camber is 26.0cm, such as Figure 3 shown.

[0037] The steel box girder is constructed by the top-pushing method, and the top-pushing span combination is 58m+65×4m+11m+20m. Figure 4 As shown. The assembly platform is set between Pier 32 and temporary Pier 1#. The assembly platform is 38m long, the steel guide beam is 48m long, and the I-shaped straight web section is adopted. There are 6 fixed fulcrums and 2 fulcrums on the assembly platform. The total length of the jacking is 350m. After each segment is positioned, assembled and welded on the assembly platform according to the stress-free design line, it is pushed forward section by section.

[0038] The steel box girder and guide beam are made of Q355 steel with an allowable stress of 296MPa. The allowable support reaction of the temporary pier is the total weight of the jacking beam divided by the number of fixed supports and multiplied by the coefficient K. The coefficient K is usually 1.2-1.5. In this project, 1.2 is taken to calculate the allowable support reaction of the temporary pier to be 21000kN. The allowable support reaction of the assembly platform support is 20000kN. Considering the structural construction and safety requirements, the threshold value of the support elevation adjustment is 19cm. During the jacking process of the steel box girder, the adjustable temporary pier supports are 1#-6#, and their initial elevation is set to 0.16m. The assembly platform support does not participate in the support elevation adjustment. The assembly platform support elevation is set according to the stress-free linear design value corresponding to the assembled steel box girder assembly segment.

[0039] The secondary development technology of ANSYS based on APDL of the present invention establishes the bar system model of the steel box girder jacking process, and the calculation model is as follows: Figure 5 As shown in the figure, the steel box girder and guide beam are simulated by beam4 unit, and the support is simulated by vertical constraint. The model of each construction stage is established according to the method of "the pier moves but the beam does not move".

[0040] The push beam is 350m long, the guide beam is 48m long, the total push beam length is 398m, the unit length is 1m, the model has a total of 398 units and 399 nodes. The origin of the x-coordinate of the calculation model is set at the fulcrum position behind the assembly platform, and the total push distance is 350m.

[0041] Taking into account the assembly of steel box girders, the maximum cantilever of the guide beam and the upper pier, the standard jacking amount is 1m, and there are 350 longitudinal calculation conditions in the whole process of jacking. The calculation table of longitudinal conditions is shown in Table 1. The calculation of a single jacking construction stage is based on the idea of ​​"one-time drop" and "forced displacement".

[0042] Table 1 Longitudinal working condition calculation table

[0043]

[0044]

[0045] Calculation results of the model of the embodiment of the present invention

[0046] The elevation modulus is set to 10mm. The principle of adjusting the elevation of the temporary pier support is controlled according to the support reaction limit. The overall setting principle of adjusting the support elevation for the temporary pier support reaction exceeding the limit is set according to the idea of ​​"adjusting the pier vertically downward to reduce the force; adjusting the adjacent pier vertically upward to share the force", and then adjusting the support elevation to ensure the safety and rationality of the structural force. The specific adjustment principles are shown in Table 4. The first column in the table indicates the position of the support reaction exceeding the limit, and the situation where the support elevation needs to be adjusted; the second and third columns respectively indicate the support number and the adjustment direction of the support that need to be adjusted.

[0047] According to the fulcrum elevation adjustment principles in Table 2, the fulcrum elevation adjustment plan obtained through fulcrum elevation adjustment optimization and integration is shown in Table 3.

[0048] Table 2 Principles of adjusting the fulcrum elevation

[0049]

[0050]

[0051] Table 3 Optimized adjustment scheme of pivot elevation

[0052]

[0053] According to the above support elevation adjustment scheme, the temporary pier support reaction force diagram under this adjustment scheme is obtained, as shown in Figure 6 As shown. Figure 6 It is known that the reaction force of the temporary pier support after optimization and adjustment meets the control value requirements, and the number of adjustments during the top-pushing construction process is only 11 times, and the sum of the absolute values ​​of all support adjustments is 0.71m, that is, the amount of steel plate required for the adjustment of the support elevation is small, and the economic benefits are significant. The calculation computer CPU uses a 2.50GHz i5 Intel processor. The calculation time of the proposed support elevation optimization method program is less than 0.5h. The basic data required for the calculation is simple, and the support elevation adjustment plan can be quickly calculated based on the top-pushing related parameters. The same computer configuration is used to adjust the support elevation based on the exhaustive method. The final number of adjustments is 9 times, the total amount of support elevation adjustment is 2.26m, and the calculation time is about 13h. Therefore, in the analysis of the whole process of top-pushing, the proposed support elevation optimization method is an efficient method to determine the support elevation adjustment plan for the variable curvature vertical curved beam, and it has great engineering application value.

[0054] In the embodiment of the present invention, combined with the top-pushing construction parameters of a bridge in Tianjin, the support elevation of the variable curvature steel box girder is optimized based on MATLAB and ANSYS. The results show that the calculated support elevation adjustment scheme significantly improves the calculation efficiency and has good economic benefits compared with the exhaustive method, while ensuring the structural force safety during the top-pushing process.

[0055] Although the embodiments and drawings of the present invention are disclosed for illustrative purposes, those skilled in the art will appreciate that various substitutions, changes and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments and drawings.

Claims

1. A method for optimizing the elevation adjustment of the top-pushing support point of a variable curvature vertical curve, characterized in that: The method uses the bridge centerline design reference line as the x-axis, and the jacking forward direction as the positive direction of the x-axis; the vertical direction is the z-axis, and the vertical upward is the positive direction of the z-axis. The x-coordinate represents the longitudinal position of the jacking beam, and the z-coordinate represents the distance from the design reference line. The steps of the optimization method are: S1. Smooth jacking analysis and calculation: Starting from the longitudinal position corresponding to the first jacking condition, the finite element software is used to establish a bridge jacking construction model, and the programming software is used to call the finite element software for rapid analysis, and the support reaction force value, stress value and support point elevation value of the current calculation condition gk jacking parameter are calculated. If the constraint conditions are met, the next jacking condition gk+1 calculation is performed until all jacking conditions are calculated; if the constraint conditions are not met, jump to the next step; S2. Adjustment of temporary pier support elevation: if the current calculation condition does not meet the constraint conditions, enter the support elevation adjustment module, start adjusting the support elevation of the previous calculation condition gk-1 of the calculation condition, and record the calculation condition D(i)=gk and the adjustment condition number A(i)=gk-1 of the top-pushing beam body that does not meet the constraint conditions, and correct the existing support elevation according to the support elevation adjustment plan. In addition to meeting the structural force safety requirements of the adjustment condition and the condition immediately following it, the support elevation adjustment plan should also ensure that the support elevation is minimized. After the support elevation is adjusted once, if the two conditions do not meet the constraint conditions, the next support elevation adjustment is performed; if the constraint conditions are met, the next top-pushing condition gk+1 calculation is performed; S3. Adjustment and integration of temporary pier support elevation; After all the jacking conditions are calculated, the fulcrum elevation adjustment scheme is integrated. The integrated fulcrum elevation adjustment aims to minimize the number of adjustments under the premise of the total amount of adjustment. The j-th longitudinal position fulcrum elevation adjustment scheme and the j+1-th fulcrum elevation adjustment scheme are merged in sequence. The elevation is corrected according to the merged fulcrum elevation adjustment vector, and the fulcrum elevation adjustment gk is calculated. H (j) Structural force analysis: if the constraint conditions are not met, the next fulcrum elevation adjustment plan is integrated; if the constraint conditions are met, the fulcrum elevation adjustment plan is integrated once and forms the final fulcrum elevation adjustment. At this time, the total fulcrum elevation adjustment amount m is the smallest and the number of adjustments k is the least. Where: E represents the elevation of the jacking support point under each jacking calculation condition during the whole jacking process; R i Represents the reaction force of fulcrum i#; [R i ] represents the allowable support reaction force of the fulcrum i#; σ G represents the maximum stress of each section of the beam; [σ G ] represents the allowable stress of the beam; σ D represents the maximum stress of each cross section of the guide beam; [σ D ] represents the allowable stress of the guide beam; Indicates the lowest elevation of each support point, h i Indicates the top elevation of each support point. Indicates the highest elevation of each support point.

2. The optimization method for determining the elevation adjustment scheme of the support point of a vertical curved beam with variable curvature during jacking process according to claim 1 is characterized in that: The elevation adjustment principle of the temporary pier support point of S2 is controlled by the support point reaction force limit value, and the support point position is adjusted vertically downward to reduce the reaction force supported by the pier; The support point position near the pier is adjusted upward to share the over-limit support point load, and then the support point elevation is adjusted to make the structure load safe and reasonable.

3. The optimization method for determining the elevation adjustment scheme of the support point of a vertical curved beam with variable curvature during jacking process according to claim 1 is characterized in that: The support elevation adjustment module of S2 uses the main program to call the finite element model of the pushing process for calculation based on the main beam pushing parameters. When the structural force safety does not meet the requirements at a certain pushing stage, the temporary pier support elevation is adjusted and optimized, and the support elevation optimization results are stored.

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