Hybrid beam cable-stayed bridge concrete side span and cast-in-place support interactive design method

Abstract

The invention relates to the technical field of bridges, and provides a hybrid beam cable-stayed bridge concrete side span and cast-in-place support interactive design method, through interactive design of a concrete side span and a cast-in-place support, unification of structural safety, structural economy and support cost saving is achieved, and the cost of the whole construction process is saved; according to the method, in the interactive design process, the three-level adjustment priority of a support batch dismantling scheme, prestressing tendon arrangement and the geometric size of a main beam is established, and the influence of concrete side span parameter adjustment on a middle span steel beam is reduced to the minimum; according to the method, for the structure meeting the stress requirement and the support meeting the flood crossing requirement, the structure newly-added cost and the support amortization cost are comprehensively considered, the most economical combination scheme is selected, the project life cycle cost is minimized on the premise that safety is guaranteed, and on the premise that the structure stress safety is guaranteed, the project life cycle cost is reduced. Risks of water blocking and damming of a large number of supports in the flood period are thoroughly avoided, and smooth flood discharge and safety of the support structure are ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bridges, and particularly relates to a mixed girder cable-stayed bridge concrete side span and cast-in-place support interactive design method. BACKGROUND

[0002] Mixed girder cable-stayed bridges have been widely used due to their strong crossing capacity and large rigidity. The side span of a mixed girder cable-stayed bridge is usually a concrete structure with large self-weight and rigidity, and the side span concrete plays the role of anchoring and weighting for the mid-span.

[0003] Due to the large difference in self-weight between the side span and the mid-span, the side span cannot be constructed by the conventional symmetrical cantilever method. In the prior art, the concrete side span is usually constructed by pouring and pre-stressing tendon tensioning on the support; as the main span girder segments are sequentially installed, the side span and the mid-span cable are also symmetrically tensioned accordingly; after the main span closure and the completion of the tensioning of the full-bridge cable, the side span cast-in-place support is removed at one time.

[0004] However, the water blocking rate of the side span support of a large-span mixed girder cable-stayed bridge is large, and the construction period is long, so the main girder construction and support removal cannot be completed in one dry period, and the conventional construction procedure has the following problems and deficiencies: (1) According to the water conservancy technical regulations for river-crossing bridges in different places, the allowable water blocking area of a river-crossing bridge is generally 3.5% to 7%. A large number of cast-in-place supports will greatly exceed the allowable water blocking rate, seriously hinder the normal flood discharge during the flood period, and cause waterlogging, which may cause serious danger to the structures on both banks of the river.

[0005] (2) The sudden flood period is usually accompanied by a large amount of floating objects, and the dense temporary support greatly increases the water blocking effect; in severe cases, the temporary support may be washed away by the flood, further causing damage to the completed bridge structure. The prior art lacks a precise simulation means for the stress state of the structure during the support removal process, and relevant personnel cannot predict whether the main girder will crack and the remaining support will be unstable during the batch removal of the support, so the one-time removal strategy must be adopted.

[0006] (3) The strength of the natural foundation is greatly affected by the flood, and for the cast-in-place support that needs to pass through the flood period, bored piles or driven steel pipe piles are usually used, the support pile foundation construction period is long, the driven steel pipe pile cannot be effectively recycled, and the support foundation cost is high.

[0007] In view of this, it is necessary to propose a mixed girder cable-stayed bridge concrete side span and cast-in-place support interactive design method to solve or at least alleviate the above-mentioned defects. SUMMARY

[0008] The main purpose of the present application is to provide a mixed beam cable-stayed bridge concrete side span and cast-in-place support interactive design method to solve the technical problems of rigid removal timing of the cast-in-place support of the concrete side span of the mixed beam cable-stayed bridge (must be removed once after the whole bridge closure, cannot dynamically adapt to flood warning), and the main beam structure is designed according to the bridge completion state, and the stress requirements of the support batch removal in the construction process are not considered.

[0009] To achieve the above-mentioned purpose, the present application provides a mixed beam cable-stayed bridge concrete side span and cast-in-place support interactive design method, comprising the following steps: S1, obtaining the initial structural parameters of the concrete side span main beam, the maximum allowable water blocking area of the conventional support, and the actual water blocking area of the conventional support; S2, if the actual water blocking area is greater than the maximum allowable water blocking area, a plurality of support batch removal schemes are drafted; S3, establishing a whole bridge structure analysis model, dividing the construction stages according to the actual construction sequence, inputting the initial structural parameters and a plurality of support batch removal schemes, and calculating the stress state of the concrete side span main beam and the stress state of the support under each construction stage; S4, judging whether the stress state of the concrete side span main beam and the stress state of the support under each construction stage meet the preset safety standard; if yes, marking the current support batch removal scheme as a feasible scheme, entering step S7, otherwise entering step S5; S5, keeping the main beam size unchanged, adjusting the arrangement parameters of the prestressed beam, generating a plurality of prestressed adjustment sub-schemes, and returning to step S3 for recalculation; if there is a prestressed adjustment sub-scheme that makes all construction stages meet the safety standard, the combination of the current support batch removal scheme and the prestressed adjustment sub-scheme is marked as a feasible scheme, and step S7 is entered, otherwise step S6 is entered; S6, adjusting the geometric size of the concrete side span main beam according to the preset priority, returning to step S5 for prestressed optimization and calculation after each adjustment, until the combination of the geometric size and the prestressed parameters that meet the safety standard is found, which is marked as a feasible scheme and enters step S7; S7, summarizing all feasible schemes, calculating the comprehensive cost of each feasible scheme, and selecting the feasible scheme with the minimum comprehensive cost as the optimal construction scheme output.

[0010] Preferably, the step S1 of obtaining the initial structural parameters of the concrete side span main beam comprises the following steps: A whole bridge finite element model is established according to the material properties and geometric properties of the bridge structure, and the preliminary structural size and preliminary arrangement of the prestressed beam of the concrete side span main beam are obtained by calculation according to the minimum bending energy principle and the one-time bridge construction method; The construction stage is divided according to the conventional construction procedure, the full-support of the concrete side span is simulated in the full-bridge finite element model, the full-support is set as a compression spring unit only; and according to the support removal step in the conventional construction procedure, the spring units are passivated in sequence at the removal time, and the node force with the same node position at the previous passivation time is applied, which is equal in size and opposite in direction to the spring support reaction force; The full-bridge finite element model is run to perform the whole-process construction simulation calculation, the stress state of the structure in each construction stage is accumulated, and the stress distribution of the concrete side span main beam in the whole-process construction is obtained; The stress distribution is compared with the preset stress safety standard, the preliminary structure size and the preliminary prestressed beam arrangement are optimized and adjusted according to the stress distribution for the part that does not meet the stress safety standard, and the initial structure parameters of the optimized concrete side span main beam are output; wherein the initial structure parameters include beam height, web thickness, top plate thickness, bottom plate thickness and prestressed beam arrangement parameters.

[0011] Preferably, the step S1 of obtaining the maximum allowable water-blocking area of the conventional support includes the following steps: The allowable value of the flood control water-blocking rate at the bridge site, the water-blocking area of the permanent pier and the river cross-section area corresponding to the design flood level at the bridge site are obtained; The maximum allowable total water-blocking area is calculated according to the allowable value of the flood control water-blocking rate and the river cross-section area; The difference between the maximum allowable total water-blocking area and the water-blocking area of the permanent pier is calculated to obtain the maximum allowable water-blocking area of the conventional support.

[0012] Preferably, the step S2 includes the following steps: S21, if the actual water-blocking area is greater than the maximum allowable water-blocking area, a plurality of support batch removal schemes are prepared; wherein each support batch removal scheme is generated according to the following principles: at least two steel pipe columns form a support group, which is the smallest unit for support removal; each support group is symmetrically arranged from the side span midspan to the direction of the two piers; the spatial position coordinates of each support group and the removal time sequence of each support group are determined; S22, for each support batch removal scheme, the maximum instantaneous water-blocking area in each removal stage is calculated, and it is verified whether the maximum instantaneous water-blocking area is less than or equal to the maximum allowable water-blocking area; S23, all support batch removal schemes that meet the maximum instantaneous water-blocking area less than or equal to the maximum allowable water-blocking area are screened out to obtain a plurality of support batch removal schemes.

[0013] Preferably, the step S3 includes the following steps: S31, a full-bridge structure analysis model is established, construction stages are divided according to actual construction sequence, and the initial structure parameters and multiple support removal schemes are input into the full-bridge structure analysis model; S32, in each construction stage, the cast-in-place support is simulated as a compression spring unit, and according to the removal time in each support removal scheme, the spring unit at the corresponding position is passivated in sequence in the corresponding removal stage, and at the same time, a node force equal in size and opposite in direction to the support reaction force of the spring unit is applied to the same node position at the passivation time, to simulate the load transfer in the support removal process; S33, the full-bridge structure analysis model is run, and the concrete sectional edge normal compressive stress and the concrete sectional edge normal tensile stress of the concrete side span main beam and the axial force value and the bending moment value of each steel pipe column in each construction stage are calculated and output as the stress state of the concrete side span main beam and the stress state of the support.

[0014] Preferably, the step S4 of judging whether the stress state of the concrete side span main beam and the stress state of the support in each construction stage meet the preset safety standard comprises the following steps: judging whether the following conditions are met in each construction stage: Condition one: the concrete side span main beam meets: ; and meets: ; wherein is the concrete sectional edge normal compressive stress of the concrete side span main beam in the construction stage, is the concrete sectional edge normal tensile stress of the concrete side span main beam in the construction stage, is the design value of the concrete axial compressive strength, is the design value of the concrete axial tensile strength; Condition two: the steel pipe support strength meets: ; wherein is the steel pipe support structure importance coefficient, is the axial force value of the steel pipe support under the action of the load, is the effective sectional area of the steel pipe support considering the influence of local stability, is the design allowable strength of the steel material specified in the specification; Condition three: the steel pipe support stability meets: ; wherein is the bending moment of the steel pipe support around the y-axis under the action of the load, is the bending moment of the steel pipe support around the z-axis under the action of the load is the overall stability reduction coefficient of the axial compression member , are the sectional moduli of the effective section relative to the y-axis and the z-axis, respectively, considering the influence of local stability; If all the construction stages satisfy the condition one, the condition two and the condition three at the same time, it is determined that the current support batch removal scheme satisfies the preset safety standard; otherwise, it is determined that the preset safety standard is not satisfied.

[0015] Preferably, the step S5 keeps the girder size unchanged, adjusts the arrangement parameters of the prestressed beam, and generates a plurality of prestress adjustment sub-schemes, including the following steps: S51, obtaining the girder geometric size corresponding to the current support batch removal scheme determined as not satisfying the preset safety standard in step S4; wherein the girder geometric size includes the girder height, the web thickness, the top plate thickness and the bottom plate thickness; S52, keeping the girder geometric size unchanged, and adjusting the arrangement parameters of the prestressed beam in the following priority order: first adjusting the tensioning sequence of the prestress; second adjusting the linear shape of the prestressed beam; and finally adjusting the steel beam model of the prestressed beam; S53, generating a prestress adjustment sub-scheme each time the arrangement parameters are adjusted; wherein the prestress adjustment sub-scheme includes the adjusted tensioning sequence, linear shape and steel beam model; S54, combining the generated plurality of prestress adjustment sub-schemes with the current support batch removal scheme respectively as the plurality of prestress adjustment sub-schemes.

[0016] Preferably, the step S6 includes the following steps: S61, obtaining the girder geometric size corresponding to the current support batch removal scheme still not satisfying the preset safety standard after adjusting the prestressed beam in step S5; S62, gradually adjusting the girder geometric size in the following priority order: first adjusting the web thickness with an adjustment interval of 5cm~10cm; second adjusting the top plate thickness or the bottom plate thickness with an adjustment interval of 5cm~10cm; and finally adjusting the girder height with an adjustment interval of 5cm~10cm; S63, generating a new girder structure scheme each time the size adjustment is completed, and returning to step S5 to re-optimize the prestressed beam parameters and check; S64, repeating steps S62 to S63 until a combination of geometric size and prestressed beam parameters satisfying the safety standard is found, marking the combination as a feasible scheme and entering step S7.

[0017] Preferably, the step S7 includes the following steps: S71, summarizing all feasible schemes; wherein each feasible scheme includes the final geometric size of the concrete side span girder, the final arrangement parameters of the prestressed beam and the final batch removal scheme of the cast-in-place support; S72, obtaining the reference girder material cost and the reference support service period corresponding to the conventional construction scheme; S73, for each feasible solution, calculate the increase of the main beam material cost relative to the benchmark main beam material cost; S74, for each feasible solution, calculate the actual service period of each support group according to the demolition timing in the final batch demolition scheme, and calculate the amortization cost of support materials; S75, for each feasible solution, calculate the comprehensive cost according to the increase and the amortization cost of support materials; S76, compare the comprehensive costs of all feasible solutions, and select the feasible solution with the minimum comprehensive cost as the optimal construction scheme output.

[0018] Compared with the prior art, the present application has the following beneficial effects: The present application realizes the unity of structural safety, structural economy and support cost saving through the interactive design of concrete side span and cast-in-place support, saves the construction process cost; In the interactive design process, the present application establishes a three-level adjustment priority of support batch demolition scheme, prestressed beam arrangement and main beam geometric size, reduces the influence of concrete side span parameter adjustment on the mid-span steel beam to the minimum, breaks the rigid constraint of one-time demolition, and realizes the dynamic and batch early demolition of support before the flood period; The present application selects the most economical combination scheme by comprehensively considering the structural additional cost and support amortization cost of the support meeting the stress requirement and flood passing demand, realizes the minimization of the whole life cycle cost of the project under the premise of safety; The construction method of the present application for early demolition of part of the support is determined through interactive design, which realizes the early demolition of part of the support before the flood period under the premise of ensuring the safety of the structure, thereby completely avoiding the risk of water blocking and waterlogging of a large number of supports during the flood period, ensuring smooth flood discharge and support structure safety. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor based on the drawings shown.

[0020] Figure 1 The flowchart in an embodiment of the present application; Figure 2 The structure schematic diagram after the erection of the side span cast-in-place support, pouring of the concrete side span main beam on the support, and tensioning of the prestressed steel beam in an embodiment of the present application; Figure 3 The structure schematic diagram after the early demolition of part of the side span cast-in-place support in an embodiment of the present application; Figure 4 This is a schematic diagram of the structure after the simultaneous installation and tensioning of the stay cables in the side span and the middle span, according to one embodiment of the present invention; Figure 5 This is a schematic diagram of the main span structure after closure in one embodiment of the present invention; Figure 6 This is a schematic diagram of the structure after removing the remaining side span cast-in-place support in one embodiment of the present invention; Figure 7 This is a schematic diagram of a side span support system in the prior art; Figure 8 This is a schematic diagram of the support structure that was removed in advance. Figure 9 A schematic diagram of the brackets that were later removed; Figure 10 This is a schematic diagram of the Bailey beam before its separation and dismantling in one embodiment of the present invention; Figure 11 This is a schematic diagram of the structure after the Bailey beam is separated and dismantled in one embodiment of the present invention; Figure 12 This is a schematic diagram of the structure of the bracket graded unloading block assembly in one embodiment of the present invention; Figure 13 for Figure 12 A view along the AA direction; Figure 14 for Figure 13 A view along the BB direction; Figure 15 for Figure 12 A view along the CC direction.

[0021] The objectives, features, and advantages of this invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings.

[0022] Explanation of icon numbers: 10. First support unit; 110. First I-beam; 120. Second I-beam; 130. First detachable connector; 20. Second support unit; 210. Third I-beam; 220. Fourth I-beam; 230. Second detachable connector; 30. Third connector; 310. Rectangular slot; 320. Nut; 40. Filling layer; 50. Base connecting plate; 610. First batch of cutting seams; 620. Second batch of cutting seams; 710. Bailey beam lower chord; 720. Connecting pin; 81. Foundation; 82. Steel pipe column; 83. Horizontal bracing; 84. Diagonal brace; 85. Pier top steel plate; 86. Bailey beam; 87. Lower crossbeam; 91. Pre-removed support; 92. Post-removed support; 93. Concrete side span main beam; 94. Stay cable. Detailed Implementation

[0023] It is to be understood that the specific embodiments described herein are merely illustrative of the present application and do not limit the scope of the application.

[0024] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present application.

[0025] The descriptions of “first”, “second”, etc. in the present application are only for descriptive purposes, and cannot be understood as indicating or implying the relative importance of the technical features indicated, or implicitly indicating the number of the technical features indicated. Therefore, the features defined as “first”, “second” can explicitly or implicitly include at least one of the features. In addition, the technical solutions of various embodiments can be combined with each other, but it must be based on the fact that the technical solutions can be realized by those of ordinary skill in the art. When the combination of technical solutions contradicts each other or cannot be realized, it should be considered that the combination of technical solutions does not exist, and is not within the protection scope of the present application.

[0026] Please refer to Figures 1 to 15 The application provides a mixed beam cable-stayed bridge concrete side span and cast-in-place support interactive design method, which comprises the following steps: S1, obtaining initial structure parameters of a concrete side span main beam 93, a maximum allowed water blocking area of a conventional support, and an actual water blocking area of the conventional support; S2, if the actual water blocking area is greater than the maximum allowed water blocking area, a plurality of support batch removal schemes are drafted; S3, establishing a full-bridge structure analysis model, dividing construction stages according to the actual construction sequence, inputting the initial structure parameters and the plurality of support batch removal schemes, and calculating the stress state of the concrete side span main beam 93 and the stress state of the support under each construction stage; S4, judging whether the stress state of the concrete side span main beam 93 and the stress state of the support under each construction stage meet the preset safety standard; if yes, marking the current support batch removal scheme as a feasible scheme, and entering step S7; otherwise, entering step S5; S5, keeping the size of the main beam unchanged, adjusting the arrangement parameters of the prestressed beam, generating a plurality of prestressed adjustment sub-schemes, and returning to step S3 for recalculation; if there is a prestressed adjustment sub-scheme that makes all the construction stages meet the safety standard, marking the combination of the current support batch removal scheme and the prestressed adjustment sub-scheme as a feasible scheme, and entering step S7; otherwise, entering step S6; S6, gradually adjust the geometric size of the concrete side span main beam 93 according to the preset priority, return to step S5 to perform prestress optimization and checking after each adjustment, until a combination of geometric size and prestress parameters meeting the safety standards is found, marked as a feasible scheme and entering step S7; S7, aggregate all feasible schemes, calculate the comprehensive cost of each feasible scheme, and select the feasible scheme with the minimum comprehensive cost as the optimal construction scheme output.

[0027] As a preferred embodiment, the initial structural parameters of the concrete side span main beam 93 obtained in step S1 include the following steps: According to the material properties and geometric properties of the bridge structure, a full-bridge finite element model is established, and the preliminary structural size and preliminary prestress bundle arrangement of the concrete side span main beam 93 are calculated according to the minimum bending energy principle according to the one-time bridge construction method; First, according to the material properties (such as the elastic modulus of concrete, the standard value of compressive strength, the yield strength of steel, etc.) and geometric properties (such as the main span span, the side span span, the tower height, the cable plane arrangement, etc.) of the bridge structure, a full-bridge finite element model is established. In the full-bridge finite element model, the minimum bending energy method known in the art is used to determine the reasonable bridge completion state of the hybrid girder cable-stayed bridge. The principle of this method is: taking the cable force distribution, the main girder bending moment, the main tower bending moment and the side pier reaction force as the control target, the initial tension of the stay cable 94 is optimized to minimize the bending strain energy of the main girder under the action of dead load, so as to obtain a balanced force and smooth linear bridge completion state. Through this calculation, the preliminary structural size (including beam height, web thickness, top plate thickness, bottom plate thickness) of the concrete side span main beam 93 and the preliminary arrangement (including steel bundle type, line shape and tensioning sequence) of the prestress bundle can be obtained.

[0028] According to the conventional construction procedure, the construction stages are divided, the full-support of the side span concrete is simulated in the full-bridge finite element model, the full-support is set to be only a compression spring unit; and according to the support removal step in the conventional construction procedure, the spring unit is passivated in sequence at the removal time, and a node force equal in size and opposite in direction to the spring support reaction force is applied at the same node position at the previous passivation time; The preliminary structural size and preliminary prestress bundle arrangement are input, and in the full-bridge finite element model, the detailed construction stages are divided according to the conventional construction procedure. For example, Figures 2 to 6 , a typical construction stage is divided into: Stage (1): erecting the side span cast-in-place support, pouring the concrete side span main beam 93 on the support, and tensioning the prestressed steel bundle after the concrete strength reaches the design requirement; stage (2): removing the cast-in-place support of the side span in advance; stage (3): simultaneously installing and tensioning the stay cables 94 of the side span and the midspan; stage (4): main span structure closure; stage (5): removing the remaining cast-in-place support of the side span.

[0029] In this embodiment, the simulation of the cast-in-place support uses only pressure spring units. The specific operation is as follows: a spring unit is arranged below each node of the concrete side span main beam 93, which only works when subjected to pressure (i.e. simulates the support of the support to the beam body), and automatically exits when the beam body is separated from the support. In the support removal, the spring units are passivated in sequence according to the removal steps, and at the same node position at the moment before passivation, a node force equal in size and opposite in direction to the support reaction force of the spring unit is applied, so as to simulate the smooth transfer of load from the support to the main beam and the cable-stayed cable 94 system during the support removal process, and solve the technical problem that the stress mutation at the moment of support removal cannot be accurately simulated in the traditional finite element analysis.

[0030] The full-bridge finite element model is run to perform full-process construction simulation calculation, and the stress state of the structure at each construction stage is accumulated to obtain the stress distribution of the concrete side span main beam 93 in the full-process construction; The full-bridge finite element model is run to perform full-process construction simulation calculation according to the construction stages. During the calculation process, the finite element program automatically accumulates the stress state of the structure at each construction stage, considers the time-dependent effects such as geometric nonlinearity, concrete shrinkage and creep, and finally outputs the stress distribution of the concrete side span main beam 93 at each construction stage.

[0031] The stress distribution is compared with the preset stress safety standard (preferably the safety standard required by the current domestic specification), the preliminary structure size and the preliminary arrangement of the prestressed beam are optimized and adjusted according to the stress distribution for the part that does not meet the stress safety standard, and the initial structure parameters of the optimized concrete side span main beam 93 are output; wherein the initial structure parameters include beam height, web thickness, top plate thickness, bottom plate thickness and prestressed beam arrangement parameters. The full-process stress distribution is compared with the preset stress safety standard stage by stage and part by part. For the part that does not meet the stress safety standard, the preliminary structure size and the preliminary arrangement of the prestressed beam are optimized and adjusted according to the degree and position of stress overrun. The principle of adjustment is: preferentially adjusting the prestress (such as adjusting the tensioning sequence, line shape and steel beam type), and adjusting the geometric size (according to the priority of web, top and bottom plate, and beam height) if it still does not meet the requirement. After optimization and adjustment, return to step S3 for full-process simulation until all construction stages and all parts meet the stress safety standard, at which time the size parameters and the beam arrangement parameters obtained after iteration convergence are taken as the initial structure parameters of the optimized concrete side span main beam 93.

[0032] As a preferred embodiment, the step S1 of obtaining the maximum allowable water-blocking area of the conventional support includes the following steps: Obtaining the allowable flood resistance rate of the bridge site, the water resistance area of the permanent pier, and the river cross-section area corresponding to the design flood level at the bridge site; The allowable flood resistance rate is a control index determined according to the river grade, the flood control plan and the relevant specifications. The water resistance area of the permanent pier can be calculated according to the size, number and arrangement of the permanent pier in the preliminary design scheme of the bridge. The sum of the projection areas of all the permanent piers in the water flow direction under the design flood level is calculated. The river cross-section area corresponding to the design flood level at the bridge site can be determined according to the hydrological analysis report of the bridge site section and the river terrain measurement data. The total area of the river cross-section corresponding to a certain return period (such as 100 years) design flood level corresponding to the bridge flood control standard is determined.

[0033] According to the allowable flood resistance rate and the river cross-section area, the maximum allowable total water resistance area is calculated. The total cross-section area of the river at the bridge site under the design flood level is the total channel for flood resistance. The allowable flood resistance rate determines the maximum proportion of the total water resistance area that can be occupied by the permanent pier and the temporary support. Therefore, the maximum allowable total water resistance area is the product of the allowable flood resistance rate and the river cross-section area.

[0034] The difference between the maximum allowable total water resistance area and the water resistance area of the permanent pier is calculated to obtain the maximum allowable water resistance area of the conventional support. After obtaining the maximum allowable total water resistance area, the water resistance area of the permanent pier occupied by the permanent pier is deducted from the maximum allowable total water resistance area. The remaining space that can be occupied by the temporary support is the constraint for subsequent preparation of the support batch removal scheme. The maximum instantaneous water resistance area of the support batch removal scheme at any removal stage should not exceed this value.

[0035] As a preferred embodiment, the step S2 comprises the following steps: S21, if the actual water resistance area is greater than the maximum allowable water resistance area, a plurality of support batch removal schemes are prepared. Each support batch removal scheme is generated according to the following principles: at least two steel pipe columns form a support group, which is the smallest unit for support removal; each support group is symmetrically arranged from the midspan of the side span to the direction of the pier; the spatial position coordinates of each support group and the removal time sequence of each support group are determined; If the actual water resistance area is greater than the maximum allowable water resistance area, it is determined that the flood resistance is limited, and the design process of the support batch removal scheme needs to be started. When preparing the scheme, a plurality of support batch removal schemes are generated according to the following principles: (1) Support group principle: at least two steel pipe columns form a support group, which is the smallest unit for support removal. The purpose of setting up a group instead of removing a single column is that the lateral stability of a single steel pipe column is poor and prone to overturning during removal; two or more steel pipe columns form a group, which can form a stable spatial force system to ensure the overall stability of the remaining support during removal.

[0036] (2) Symmetrical arrangement principle: each support group is symmetrically arranged from the midspan of the side span to the direction of the pier. The purpose of symmetrical removal is to balance the stress of the main beam during support unloading, and to avoid excessive additional torsional moment or lateral deformation of the main beam caused by unilateral unloading.

[0037] (3) Parameter determination: determine the spatial position coordinates of each support group and the removal sequence of each support group to form a preliminary support batch removal scheme.

[0038] S22, for each support batch removal scheme, calculate the maximum instantaneous water blocking area in each removal stage, and verify whether the maximum instantaneous water blocking area is less than or equal to the maximum allowable water blocking area; For each support batch removal scheme, according to its removal sequence, the entire construction process is divided into several removal stages. In each removal stage, the number of steel pipe columns still in service in that stage is counted, and the maximum instantaneous water blocking area in that stage is calculated to verify whether the maximum instantaneous water blocking area is less than or equal to the maximum allowable water blocking area. This step ensures that the water blocking area at each moment does not exceed the maximum allowable water blocking area through stage-by-stage calculation. If the calculated value of a scheme in a certain stage exceeds the maximum allowable water blocking area, it is determined that the scheme does not meet the flood discharge requirements and is rejected.

[0039] S23, screen all support batch removal schemes that meet the maximum instantaneous water blocking area less than or equal to the maximum allowable water blocking area to obtain multiple support batch removal schemes.

[0040] After all the proposed support batch removal schemes are calculated stage by stage, all support batch removal schemes that meet the maximum instantaneous water blocking area less than or equal to the maximum allowable water blocking area are screened to obtain multiple support batch removal schemes.

[0041] As a preferred embodiment, the step S3 comprises the following steps: S31, establish a full-bridge structure analysis model, divide the construction stages according to the actual construction sequence, and input the initial structure parameters and multiple support batch removal schemes into the full-bridge structure analysis model; A full-bridge structure analysis model (e.g., using a common commercial finite element software) is established, construction stages are divided according to the actual construction sequence, and the initial structure parameters and various support removal schemes are input into the full-bridge structure analysis model as the basis for subsequent simulation calculations.

[0042] In each construction stage, the cast-in-place support is simulated as a compression-only spring element, and according to the removal timing in each support removal scheme, the spring element at the corresponding position is passivated in sequence in the corresponding removal stage, and at the same time, a node force equal in size and opposite in direction to the support reaction force of the spring element is applied to the same node position at the previous passivation time to simulate the load transfer during support removal. In each construction stage, the cast-in-place support is simulated as a compression-only spring element, and according to the removal timing in each support removal scheme, the spring element at the corresponding position is passivated in sequence in the corresponding removal stage, and at the same time, a node force equal in size and opposite in direction to the support reaction force of the spring element is applied to the same node position at the previous passivation time to simulate the load transfer during support removal.

[0043] S33, the full-bridge structure analysis model is run, and the concrete sectional normal stress and the concrete structure long-term condition bearing capacity of the concrete side span main beam 93 in each construction stage are calculated and output, as well as the steel pipe support strength and the steel pipe support stability of each steel pipe column, as the stress state of the concrete side span main beam 93 and the stress state of the support.

[0044] The full-bridge structure analysis model is run, and the full-process construction simulation calculation is performed, the structure stress state of each construction stage is automatically accumulated during the calculation process, and the geometric nonlinearity, concrete shrinkage and creep, and other time-dependent effects are considered, and the concrete sectional normal stress and the concrete structure long-term condition bearing capacity of the concrete side span main beam 93 in each construction stage are calculated and output, as well as the steel pipe support strength and the steel pipe support stability of each steel pipe column.

[0045] As a preferred embodiment, the step S4 of judging whether the stress state of the concrete side span main beam 93 and the stress state of the support in each construction stage meet the preset safety standard includes the following steps: whether the following conditions are met in each construction stage: Condition one: the concrete side span main beam 93 meets: , and meets: ; wherein is the concrete sectional edge normal compressive stress (MPa) of the concrete side span main beam 93 in the construction stage, the normal tensile stress (MPa) of the concrete section edge of the concrete section of the concrete side span main girder 93 in the construction stage, the design value of the axial compressive strength of the concrete (MPa), the design value of the axial tensile strength of the concrete (MPa); Condition two: the strength of the steel pipe support satisfies: ; wherein, is the importance coefficient of the steel pipe support structure, is the axial force value (MN) of the steel pipe support under the action of the load, is the effective sectional area (m 2 ) of the steel pipe support considering the influence of local stability, is the design allowable strength of the steel material specified in the specification (MPa); Condition three: the stability of the steel pipe support satisfies: ; wherein is the bending moment (MN·m) of the steel pipe support around the y-axis under the action of the load, is the bending moment (MN·m) of the steel pipe support around the z-axis under the action of the load, is the overall stability reduction coefficient of the axial compression member , are the sectional moduli (m 3 ) of the effective section relative to the y-axis and the z-axis considering the influence of local stability; if all the construction stages simultaneously satisfy the condition one, the condition two, and the condition three, it is determined that the current support batch removal scheme satisfies the preset safety standard; otherwise, it is determined that the preset safety standard is not satisfied.

[0046] Preferably, the overall stability reduction coefficient of the axial compression member is calculated according to the following formula: ; wherein, , ; wherein, is the axial compression slenderness ratio, which can be directly selected according to the specification; is the yield strength of the steel material; E is the elastic modulus of the steel material; is the calculation parameter of the overall stability reduction coefficient of the axial compression member, which can be directly taken from the specification. is the relative slenderness ratio, is an intermediate parameter for reduction coefficient calculation (no definite definition).

[0047] As a preferred embodiment, the step S5 keeps the main girder size unchanged and adjusts the arrangement parameters of the prestressed beam to generate multiple prestressed adjustment sub-schemes, including the following steps: S51, obtaining the girder geometry corresponding to the current support batch removal scheme determined as not satisfying the preset safety standard in step S4; wherein the girder geometry includes the beam height, the web thickness, the top plate thickness and the bottom plate thickness; S52, keeping the girder geometry unchanged, adjusting the arrangement parameters of the prestressed beam in the following priority order: first adjusting the tensioning sequence of the prestress; second adjusting the linear of the prestressed beam; and finally adjusting the steel beam model of the prestressed beam; adjusting the tensioning sequence does not increase the material cost, only changes the construction timing, has the most direct effect on the structure stress and the most optimal economy; adjusting the linear involves pipeline arrangement, the cost is moderate; adjusting the steel beam model involves changing the material specification, the cost is the highest, and it is the last means.

[0048] S53, generating a prestressed adjustment sub-scheme each time the arrangement parameter is adjusted; wherein the prestressed adjustment sub-scheme includes the adjusted tensioning sequence, linear and steel beam model; S54, combining the generated multiple prestressed adjustment sub-schemes with the current support batch removal scheme respectively as the multiple prestressed adjustment sub-schemes.

[0049] As a preferred example, the step S6 includes the following steps: S61, obtaining the girder geometry corresponding to the current support batch removal scheme still not satisfying the preset safety standard after adjusting the prestressed beam in step S5; S62, gradually adjusting the girder geometry in the following priority order: first adjusting the web thickness, the adjustment interval is 5cm~10cm; second adjusting the top plate thickness or the bottom plate thickness, the adjustment interval is 5cm~10cm; and finally adjusting the beam height, the adjustment interval is 5cm~10cm; first adjusting the web thickness, the adjustment interval is 5cm~10cm, the web has the largest contribution to the shear and stiffness of the cross section, and the priority adjustment can quickly improve the structure stress and has the least impact on the bridge deck system; second adjusting the top plate thickness or the bottom plate thickness, the adjustment interval is 5cm~10cm, the top plate thickness or the bottom plate thickness adjustment affects the bridge deck elevation or the lower edge line; and finally adjusting the beam height, the adjustment interval is 5cm~10cm, the beam height adjustment has the largest impact on the overall bridge stiffness and may affect the bridge clearance, and it is the last means. The interval of 5~10cm is an engineering experience value determined according to the minimum construction size requirement of the concrete structure and the template modulus, which can ensure the adjustment effect and avoid excessive adjustment.

[0050] S63, generating a new girder structure scheme each time the size adjustment is completed, and returning to step S5 to re-optimize and check the prestressed beam parameters; S64, repeating steps S62 to S63 until a combination of geometry and prestressed beam parameters satisfying the safety standard is found, marking the combination as a feasible scheme and entering step S7.

[0051] As a preferred embodiment, the step S7 comprises the following steps: S71, aggregating all feasible schemes; wherein each feasible scheme comprises final geometric dimensions of the concrete side span main beam 93, final arrangement parameters of the prestressed beam, and final batched removal scheme of the cast-in-place support; S72, obtaining the reference main beam material cost and the reference support service period corresponding to the conventional construction scheme; wherein the reference main beam material cost can be calculated according to the conventional design size and the bundle according to the market material unit price. The reference support service period is the total number of days from the erection to the one-time removal of the support in the conventional scheme.

[0052] S73, for each feasible scheme, calculating the increase amount of the main beam material cost relative to the reference main beam material cost; S74, for each feasible scheme, calculating the actual service period of each support group according to the removal timing in the final batched removal scheme, and calculating the support material amortization cost; S75, for each feasible scheme, calculating the comprehensive cost according to the increase amount and the support material amortization cost; S76, comparing the comprehensive costs of all feasible schemes, and selecting the feasible scheme with the minimum comprehensive cost as the optimal construction scheme output.

[0053] As another preferred embodiment, the present application also provides a side span cast-in-place support design and removal construction scheme. For the design of cast-in-place support, the side span support system of the present application is composed of foundation, steel pipe column, flat link, inclined strut, pier top steel plate, lower cross beam, unloading block, Bailey beam, I-beam, square wood and formwork, etc. According to the proposed support removal scheme, the side span support foundation is divided into two types, the support removed at the later stage adopts the driven steel pipe pile foundation, and the support removed in advance adopts the strip-shaped enlarged foundation.

[0054] The connection between the driven steel pipe pile and the steel pipe column is a prominent stress position, and single-sided bevel welding is used between the two; 4 reinforcing connection plates are uniformly arranged around the connection, and ring fillet welds are used to weld them with the steel pipe pile and the steel pipe column. For the steel pipe column that needs to be connected, the same connection method can be used.

[0055] Please refer to the accompanying Figures 7 to 15 In another embodiment, the present application also provides a support grading unloading block assembly for a hybrid girder cable-stayed bridge, comprising: The first support unit 10 comprises two first I-shaped steel 110 and second I-shaped steel 120 arranged oppositely, the webs of the first I-shaped steel 110 and second I-shaped steel 120 are opposite, and the two are fixedly connected by a first detachable connecting piece 130 to form a first box structure. Further, the first detachable connecting piece 130 and the second detachable connecting piece 230 are first screws, both ends of the first screw are provided with a fastening nut 320. The first screw is arranged in the connecting hole (not marked in the figure) corresponding to the webs of the two I-shaped steels, and the two ends are locked by the fastening nut 320. Through this connection mode, the first I-shaped steel 110 and the second I-shaped steel 120 and the space between them together form a box structure, i.e. the first box structure. The first box structure has a closed cross-sectional form, can effectively bear the vertical load, and has a certain bending stiffness.

[0056] The second support unit 20 comprises two third I-shaped steel 210 and fourth I-shaped steel 220 arranged oppositely, the webs of the third I-shaped steel 210 and fourth I-shaped steel 220 are opposite, and the two are fixedly connected by a second detachable connecting piece 230 to form a second box structure. The third connecting piece 30 penetrates and connects the first support unit 10 and the second support unit 20, detachably connects the first box structure and the second box structure into an integral support structure, and forms a filling cavity between the first support unit 10 and the second support unit 20. Further, the third detachable connecting piece is a second screw, both ends of the second screw are provided with a fastening nut 320, and the length of the second screw is greater than the length of the first screw. The second screw penetrates the webs of the first I-shaped steel 110, the second I-shaped steel 120, the third I-shaped steel 210, and the fourth I-shaped steel 220, and the two ends are locked by the fastening nut 320. Through the connection of the third connecting piece 30, the first box structure and the second box structure are detachably connected into an integral support structure. At this time, a closed cavity, i.e. a filling cavity, is formed between the first support unit 10 and the second support unit 20.

[0057] The filling layer 40 is arranged in the filling cavity. The filling layer 40 transmits pressure in the normal load state, and plays a heat insulation and buffering role in the unloading process.

[0058] Further, the second I-shaped steel 120 and the third I-shaped steel 210 are arranged in close proximity, and the filling cavity is formed between the second I-shaped steel 120 and the third I-shaped steel 210. The upper flange plates and the lower flange plates of the second I-shaped steel 120 and the third I-shaped steel 210 are arranged in close proximity side by side.

[0059] As a preferred embodiment, the upper flange plate of the second I-shaped steel 120 is provided with a first notch (not shown in the figure) communicating with the filling cavity, and the upper flange plate of the third I-shaped steel 210 is provided with a second notch (not shown in the figure) communicating with the filling cavity, and the first notch and the second notch are arranged in correspondence and jointly enclose a rectangular notch 310.

[0060] Specifically, before the bracket staged unloading block assembly is installed, the construction personnel can pour fine sand into the filling cavity through the rectangular notch to ensure that the filling is dense. When cutting the web of the I-shaped steel, the cutting point is in direct contact with the fine sand, and the heat is quickly absorbed and diffused by the fine sand, thereby playing a heat insulation role. At the same time, the existence of the rectangular notch makes the cutting operation can directly observe the flow state of the fine sand, when the cutting of the web causes the fine sand to flow out, the operator can observe the descending condition of the fine sand through the rectangular notch to judge the unloading process. For example, when the first support unit 10 is removed, one side of the filling cavity is open, and the fine sand flows out through the first notch under the action of gravity, which is beneficial to subsequent cutting.

[0061] As another preferred embodiment, the lower end of the first support unit 10 and / or the second support unit 20 is provided with a base connecting plate 50, and the base connecting plate 50 is provided with bolt holes for connecting with the lower steel pipe column 82. The base connecting plate 50 is used to make the bracket staged unloading block assembly and the lower steel pipe column 82 detachably connected.

[0062] As a preferred embodiment, the webs of the first I-shaped steel 110, the second I-shaped steel 120, the third I-shaped steel 210, and the fourth I-shaped steel 220 are provided with cutting guide mark lines (not shown in the figure), and the cutting guide mark lines are located in the middle upper region of the web.

[0063] Specifically, cutting guide marking lines are provided on the webs of the first I-beam 110, the second I-beam 120, the third I-beam 210, and the fourth I-beam 220. These cutting guide marking lines are located in the upper-middle region of the webs, specifically at 2 / 3 to 4 / 5 of the web height, and on both sides of the support center line of the lower chord 710 of the Bailey beam. This position avoids the high-stress area at the bottom of the webs and ensures a smooth change in stress at the support point of the lower chord 710 when cutting the first batch of areas. Furthermore, the cutting guide marking lines are located on both sides of the support center line of the lower chord 710, and the spacing between the two marking lines is preferably equal to twice the width of the lower chord.

[0064] The cutting guide markings are pre-set on the web surface using either stamping or high-temperature resistant coating. When operators are cutting at height, there is no need for temporary measurements or marking; they can directly cut according to the pre-set markings. This avoids cutting position deviations caused by manual measurement errors, ensuring that the first batch of cuts always falls within the predetermined range. Furthermore, it standardizes operations, guaranteeing consistent unloading results even when different work teams are involved.

[0065] Preferably, the first support unit 10 and the second support unit 20 are symmetrically arranged about the central plane of the filled cavity. Under normal load-bearing conditions, the load transmitted from the Bailey beam 86 is evenly distributed to the lower structure through the four I-beams, ensuring uniform stress distribution under normal load-bearing conditions. The symmetrical design allows the first support unit 10 and the second support unit 20 to be used interchangeably without the need to distinguish left from right on site.

[0066] As a preferred example, the filling layer 40 is fine sand with a particle size ranging from 0.15 mm to 2.36 mm. The lower limit of 0.15 mm ensures sufficient voids between particles, maintaining a certain degree of fluidity under pressure. Particles larger than 2.36 mm have better fluidity but a higher void ratio, easily leading to bridging. Therefore, this embodiment uses a particle size range of 0.15 mm to 2.36 mm. Furthermore, during the cutting of the web of the inner I-beam and the descent of the Bailey beam 86, the fine sand acts as a buffer medium, being gradually compacted and providing a cushioning effect.

[0067] Workflow: Before the support structure is removed, the tiered unloading block assembly has been installed between the steel pipe column 82 and the Bailey beam 86 and is under load. At this time, the first support unit 10 and the second support unit 20 are connected as a whole by the third connector 30, and the cavity is filled with fine sand, which is poured in through a rectangular groove.

[0068] When the support is dismantled, the pin shaft 720 of the Bailey beam 86 is first removed, and the dismantled and retained supports are separated and unloaded; after the separation and unloading, the Bailey beam 86 to be dismantled is unloaded, and the retained Bailey beam remains in the original supporting state.

[0069] When the Bailey beam 86 is unloaded, the second screw rod and the nut 320 are first removed, and then one of the first screw rods and the nut 320 of the box-shaped structure is removed. At this time, the mechanical connection between the first support unit 10 and the second support unit 20 is released, but the fine sand in the filled cavity still transmits pressure, and the upper structure remains stable, achieving preliminary unloading.

[0070] According to the construction needs, one side (for example, the first support unit 10) to be dismantled is selected, and the first detachable connecting piece 130 and the second detachable connecting piece 230 (i.e., the first screw rod) and the nut 320 on the first support unit 10 are removed. For the two pieces of I-shaped steel, they are removed by cutting the web. The two pieces of I-shaped steel are cut and removed from the outside to the inside.

[0071] When the web of the I-shaped steel is cut, in order to prevent sudden damage to the I-shaped steel during cutting, the cutting position is located at the upper part of the web, and the horizontal cutting area is divided into two batches, the first batch of cutting area is one width of the lower chord of the Bailey beam 710 on both sides of the support center line; the remaining is the second batch of cutting area. When cutting the outer I-shaped steel, first cut the first batch of area, so that the top plate of the support Bailey beam lower chord 710 has a certain deformation in the local area, achieving initial unloading of the I-shaped steel; then cut the second batch of area, complete the unloading of the I-shaped steel; and remove the unloaded I-shaped steel.

[0072] After the outer I-shaped steel is removed, the Bailey beam lower chord 710 is supported on the inner I-shaped steel. The cutting method of the web of the inner I-shaped steel is the same as that of the outer I-shaped steel. When the web is cut, the top plate of the I-shaped steel is deformed and moved downward as a whole, so that the Bailey beam 86 and the upper formwork system supported on the top plate are synchronously moved downward, and then are separated from the concrete structure, and further the partial support system can be dismantled.

[0073] The above is only a preferred embodiment of the present application, and does not limit the patent scope of the present application, and any equivalent structure or equivalent process transformation using the content of the specification and drawings, or direct or indirect application in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A mixed girder cable-stayed bridge concrete side span and cast-in-place support interactive design method, characterized in that, The method comprises the following steps: S1, obtaining initial structure parameters of a concrete side span main beam, a maximum allowed water blocking area of a conventional support, and an actual water blocking area of the conventional support; S2, if the actual water blocking area is greater than the maximum allowed water blocking area, multiple support batch removal schemes are drafted; S3, a full-bridge structure analysis model is established, construction stages are divided according to an actual construction sequence, the initial structure parameters and the multiple support batch removal schemes are input, and stress states of the concrete side span main beam and stress states of the support in each construction stage are calculated; S4, it is judged whether the stress states of the concrete side span main beam and the stress states of the support in each construction stage meet preset safety standards; if yes, the current support batch removal scheme is marked as a feasible scheme, and step S7 is entered; otherwise, step S5 is entered; S5, the size of the main beam is kept unchanged, arrangement parameters of prestressed tendons are adjusted, multiple prestressed adjustment sub-schemes are generated, and step S3 is returned to recalculate; if there is a prestressed adjustment sub-scheme that makes all construction stages meet the safety standards, a combination of the current support batch removal scheme and the prestressed adjustment sub-scheme is marked as a feasible scheme, and step S7 is entered; otherwise, step S6 is entered; S6, the geometric size of the concrete side span main beam is adjusted according to a preset priority, and each adjustment returns to step S5 for prestressed optimization and calculation, until a combination of a geometric size and prestressed parameters that meet the safety standards is found, which is marked as a feasible scheme and enters step S7; S7, all feasible schemes are summarized, the comprehensive cost of each feasible scheme is calculated, and the feasible scheme with the minimum comprehensive cost is selected as an optimal construction scheme and output.

2. The method according to claim 1, wherein, The step S1 of obtaining the initial structure parameters of the concrete side span main beam comprises the following steps: A full-bridge finite element model is established according to material properties and geometric properties of the bridge structure, and the preliminary structure size and the preliminary arrangement of prestressed tendons of the concrete side span main beam are obtained by calculation according to the minimum bending energy principle and the one-time bridge construction method; Construction stages are divided according to a conventional construction procedure, full-support of the side span concrete is simulated in the full-bridge finite element model, the full-support is set as a compression spring unit, and at the same node position at a time before the removal, a node force equal in size and opposite in direction to the spring support reaction force is applied; The full-bridge finite element model is run for full-process construction simulation calculation, the structure stress states of each construction stage are accumulated, and the stress distribution of the concrete side span main beam in the full-process construction is obtained; The stress distribution is compared with a preset stress safety standard, for parts that do not meet the stress safety standard, the preliminary structure size and the preliminary arrangement of prestressed tendons are adjusted according to the stress distribution, and the initial structure parameters of the optimized concrete side span main beam are output; wherein the initial structure parameters include beam height, web thickness, top plate thickness, bottom plate thickness, and prestressed tendon arrangement parameters.

3. The method of claim 1, wherein the method is characterized by: The step S1 of obtaining the maximum allowed water blocking area of the conventional support comprises the following steps: Obtaining a specified flood control rate allowable value at a bridge site, a water-blocking area of a permanent pier, and a river cross-section area corresponding to a design flood level at the bridge site; According to the flood control rate allowable value and the river cross-section area, calculating a maximum allowable total water-blocking area; Calculating a difference between the maximum allowable total water-blocking area and the water-blocking area of the permanent pier to obtain a maximum allowable water-blocking area of the conventional support.

4. The method of claim 1, wherein the method is characterized by: The step S2 includes the following steps: S21, if the actual water-blocking area is greater than the maximum allowable water-blocking area, multiple support batch removal schemes are prepared; wherein, each support batch removal scheme is generated according to the following principles: at least two steel pipe columns form a support group, which is the smallest unit of support removal; each support group is symmetrically arranged from the midspan of the side span to the direction of the pier; the spatial position coordinates of each support group and the removal time sequence of each support group are determined; S22, for each support batch removal scheme, the maximum instantaneous water-blocking area in each removal stage is calculated, and it is verified whether the maximum instantaneous water-blocking area is less than or equal to the maximum allowable water-blocking area; S23, all support batch removal schemes that meet the condition that the maximum instantaneous water-blocking area is less than or equal to the maximum allowable water-blocking area are screened out to obtain multiple support batch removal schemes.

5. The method of claim 4, wherein the method is characterized by: The step S3 includes the following steps: S31, a full-bridge structure analysis model is established, the construction stages are divided according to the actual construction sequence, and the initial structure parameters and multiple support batch removal schemes are input into the full-bridge structure analysis model; S32, in each construction stage, the cast-in-place support is simulated as a compression spring unit, and according to the removal time sequence in each support batch removal scheme, the spring units at the corresponding positions are passivated in turn in the corresponding removal stage, and at the same time, a node force equal in size and opposite in direction to the support reaction force of the spring unit is applied to the same node position at the previous passivation time to simulate the load transfer in the support removal process; S33, the full-bridge structure analysis model is run, and the concrete sectional edge normal compressive stress and the concrete sectional edge normal tensile stress of the concrete side span main beam and the axial force value and the bending moment value of each steel pipe column in each construction stage are calculated and output as the stress state of the concrete side span main beam and the stress state of the support.

6. The method of claim 5, wherein the method further comprises: The step S4 includes the following steps: It is judged whether the stress state of the concrete side span main beam and the stress state of the support in each construction stage meet the preset safety standard. Condition one: the concrete edge span main girder satisfies: ; and satisfies: ; wherein, is the concrete sectional edge normal compressive stress of the concrete edge span main girder in the construction stage, is the concrete sectional edge normal tensile stress of the concrete edge span main girder in the construction stage, is the design value of the concrete axial compressive strength, is the design value of the concrete axial tensile strength; Condition two: the strength of steel pipe support meets: ; wherein, is the importance coefficient of steel pipe support structure, is the axial force value of steel pipe support under load, is the effective cross-sectional area of steel pipe support considering the influence of local stability, is the design allowable strength of steel specified in the specification; Condition three: the stability of steel pipe support meets: ; wherein, is the bending moment of the steel pipe support around the y-axis under the action of load, is the bending moment of the steel pipe support around the z-axis under the action of load, is the overall stability reduction coefficient of the axial compression member, , are the sectional moduli of the effective section relative to the y-axis and the z-axis considering the influence of local stability, respectively; If all construction stages meet conditions one, two and three at the same time, it is determined that the current support batch removal scheme meets the preset safety standard; otherwise, it is determined that the preset safety standard is not met.

7. The method of claim 6, wherein the method further comprises: determining the interaction between the concrete side span and the cast-in-place support based on the determined interaction between the concrete side span and the cast-in-place support. In the step S5, the main beam size is kept unchanged, and the arrangement parameters of the prestressed beam are adjusted to generate multiple prestress adjustment sub-schemes, including the following steps: S51, obtaining the main beam geometric size corresponding to the current support batch removal scheme which is determined by the step S4 as not meeting the preset safety standard; wherein, the main beam geometric size includes the beam height, the web thickness, the top plate thickness and the bottom plate thickness; S52, keeping the girder geometry unchanged, adjusting the arrangement parameters of the prestressed tendons in the following priority order: first adjusting the tensioning sequence of the prestressed tendons, second adjusting the linear arrangement of the prestressed tendons, and finally adjusting the tendon type of the prestressed tendons; S53, generating a prestressed adjustment sub-scheme for each adjustment of the arrangement parameters; wherein the prestressed adjustment sub-scheme includes the adjusted tensioning sequence, linear arrangement, and tendon type; S54, combining each of the generated prestressed adjustment sub-schemes with the current support batch removal scheme to obtain a plurality of prestressed adjustment sub-schemes.

8. The method of claim 6, wherein the method is characterized by: The step S6 includes the following steps: S61, obtaining the girder geometry corresponding to the current support batch removal scheme that still does not meet the preset safety standard after the adjustment of the prestressed tendons in step S5; S62, adjusting the girder geometry in the following priority order: first adjusting the web thickness with an adjustment interval of 5cm~10cm, second adjusting the top plate thickness or bottom plate thickness with an adjustment interval of 5cm~10cm, and finally adjusting the beam height with an adjustment interval of 5cm~10cm; S63, generating a new girder structure scheme after each size adjustment, and returning to step S5 to re-optimize and check the prestressed tendon parameters; S64, repeating steps S62 to S63 until a combination of the geometry and prestressed tendon parameters that meets the safety standard is found, marking the combination as a feasible scheme and entering step S7.

9. The method of claim 1, wherein the method is characterized by: The step S7 includes the following steps: S71, summarizing all feasible schemes; wherein each feasible scheme includes the final geometry of the concrete side span girder, the final arrangement parameters of the prestressed tendons, and the final batch removal scheme of the cast-in-place support; S72, obtaining the reference girder material cost and reference support service period corresponding to the conventional construction scheme; S73, for each feasible scheme, calculating the increase in girder material cost relative to the reference girder material cost; S74, for each feasible scheme, calculating the actual service period of each support grouping according to the removal timing in the final batch removal scheme, and calculating the support material amortization cost; S75, for each feasible scheme, calculating the comprehensive cost according to the increase and the support material amortization cost; S76, comparing the comprehensive costs of all feasible schemes, and selecting the feasible scheme with the minimum comprehensive cost as the optimal construction scheme output.

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