Design Method for Erection Alignment of Main Arch Rib of Bridge and Load-bearing Cable of Cable Crane

Abstract

The present invention provides a method for designing the erection alignment of the main arch rib of a bridge and the load-bearing cable of a cable crane, belonging to the technical field of bridge construction. The method includes the following steps: designing the alignment of the main arch rib of the bridge, designing the cable crane system according to the alignment of the main arch rib of the bridge, manufacturing the measured data of the linear measurement points according to the alignment of the arch rib, superimposing the absolute displacements of the measurement points obtained by finite element software analysis, combining the main arch temperature and the variation law of the arch rib alignment, deriving the erection coordinates, achieving the dual goals of precise installation inside the segment and precise control of the as-built alignment, designing the parameters of the cable crane system, then conducting a trial hoisting operation, analyzing and calculating the alignment, sag, and tension of the load-bearing cable of the cable crane, and then hoisting and constructing the main arch rib of the bridge using the cable crane system. The dual goals of precise installation inside the segment and precise control of the as-built alignment are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of bridge construction, and particularly to a design method for the erection line shape of the main arch rib of a large bridge and the load-bearing cable of a cable crane. Background Art

[0002] With the comprehensive promotion of various infrastructure projects in China, arch bridge projects spanning various complex geographical conditions such as river valleys, mountain valleys, and sea surfaces have been successively launched, and the required span of arch bridges has been continuously increasing. The traditional support method of construction can no longer meet the requirements, and the cable hoisting method is increasingly becoming the mainstream construction method for long-span arch bridges. In view of the characteristics of large numbers of hoisting segments, heavy loads, and long hoisting distances in long-span concrete-filled steel tube arch bridges. In conventional steel tube arch projects, welding has a very flexible adjustment margin, and the manufacturing errors of segments can be corrected by adding shims, adjusting cable forces, etc. during the hoisting process to make the arch line shape reach the control target. In bolted structures, the bolt clearance margin is only 3 mm, and the manufacturing errors and installation requirements of arch rib segments are extremely high. Therefore, it plays a very important role in both the line shape design and the load-bearing hoisting of the large bridge. Therefore, a design method for the erection line shape of the main arch rib of the large bridge and the load-bearing cable of the cable crane is required. Summary of the Invention

[0003] The purpose of the present invention is to provide a design method for the erection line shape of the main arch rib of a large bridge and the load-bearing cable of a cable crane, and to solve the technical problem that the accuracy cannot reach the requirements during the construction process of the existing main arch rib erection of the large bridge. It is necessary to design an erection line shape of the main arch rib to achieve the dual goals of precise installation inside the segment and precise control of the bridge line shape.

[0004] In order to achieve the above purpose, the technical scheme adopted by the present invention is as follows:

[0005] A design method for the erection line shape of the main arch rib of a large bridge and the load-bearing cable of a cable crane, the method comprising the following steps:

[0006] Step 1: Design the line shape of the main arch rib erection of the large bridge, and design the cable crane system according to the line shape of the main arch rib erection of the large bridge;

[0007] Step 2: Measure the actual data of the manufacturing line shape measurement points according to the line shape of the arch rib erection, superimpose the absolute displacements of the measurement points obtained by finite element software analysis, and combine the main arch temperature and the change law of the arch rib line shape to deduce the erection coordinates to achieve the dual goals of precise installation inside the segment and precise control of the bridge line shape;

[0008] Step 3: Conduct parameter design on the cable crane system, and then conduct a trial hoisting operation;

[0009] Step 4: Analyze and calculate the line shape, sag, and tension of the load-bearing cable of the cable crane, and then hoist and construct the main arch rib erection of the large bridge according to the use of the cable crane system.

[0010] Further, in Step 1, the alignment control of the fully bolted arch bridge is to control the overall alignment quality during the vertical assembly stage, and restore the relative attitude of the vertical assembly in the air. The first step is to obtain the theoretical manufacturing alignment. The manufacturing alignment is obtained by adding a camber on the basis of the design alignment. The main arch rib frame model of the bridge includes arch rib members, columns, transition piers, and steel girders. The arch rib members, columns, transition piers, and steel girders are all established with beam elements;

[0011] The tower of the cable crane system adopts a cable buckle separation structure. The buckling and cable system of the cable buckle separation structure operate independently without interference. The cable force and the assembled alignment are easier to control. Moreover, by moving the cable tower backward, space is provided for the cable system to lift the steel girder on the approach bridge deck, realizing the lifting and assembly of the superstructure of the main bridge;

[0012] The anchor of the cable crane system adopts a gravity anchor structure, which provides horizontal resistance through the friction force generated by its own weight and the foundation;

[0013] The lifting weight of the cable crane system adopts an independent lifting structure. The independent lifting structure reduces the time of transverse movement during the hoisting of the main arch ring and reduces the time in the state of the large cantilever of the arch ring, which can reduce the safety risk. Moreover, by reducing the transverse movement, it can better avoid the Z-shaped hoisting of the arch rib.

[0014] Further, the specific process of Step 2 is as follows:

[0015] First, determine the actual attitude of the vertical assembly. The actual attitude of the vertical assembly is reflected by the measuring points at the arch feet and the arch top. The determination steps are as follows: first set, then collect, and finally mark. Using the measuring points as the carrier of the theoretical three-dimensional deformation of the hoisting attitude, divide the stress-free alignment of the whole arch into 4 rounds according to the pre-assembly method, and rotate it to the horizontal position for easy vertical assembly lofting and manufacturing. After the attitude adjustment of each round is in place, taking the lower edge groove of the chord tube of each round as the starting point, the horizontal direction as the X-axis, and the vertical direction as the Z-axis, and use tools to find the approximate axis of the upper edge of the upper chord tube. At a position 1m above the port, avoid the platform cross beam of the segment arrangement. Set the measuring point mark, and finally collect the measured coordinates of the measuring points. The local coordinates of the left-side measuring points during the vertical assembly stage have a deviation between the central axis of the chord tube and the theoretical distance center value of 6.75m. Reflect the actual coordinates of the measuring points of each round into the local coordinate system, mark the left-side inner chord arch top measuring points on the fourth-round vertical assembly drawing, and convert the local coordinate system of the corresponding round of vertical assembly into the local coordinate system of the arch rib stress-free alignment with the center of the hinge closure surface as the theoretical displacement carrier;

[0016] Displace the theory of the second pair of assembled postures. During the assembly of the steel pipe arch, it is set as a curved beam cable-stayed bridge. The finite element model is established by using the Midas / Civil finite element calculation software to simulate each stage of the arch bridge assembly construction. The control objective of the calculation is that the deviation between the alignment after the arch rib shackle is removed and the alignment of the first-time erection is less than 1 cm, the deviation of the boundary pier and the cable tower during the construction process is less than 2 cm, and at the same time, the cable forces are uniform. After several iterations, the initial cable tension in the assembly construction stage that meets the requirements is obtained. The initial tension reflects the stress-free length of the cable. Substitute the initial tension into the forward model and select the external force to conduct the construction stage analysis to obtain the load effects of the structure during the process, which are used to judge the safety of the structure, including the reactions, stresses, deformations, and displacements of the arch, cable, tower, and anchor. At the same time, the key parameters of the tangential assembly are obtained, the tension value of the cable, and the total displacement of the component. The total vertical displacement is 396 mm, downward displacement, and the total horizontal displacement is 137 mm, towards the arch seat direction, and the axis deviation is 68 mm, deflecting towards the outside;

[0017] Set the coordinates for the third erection. The coordinates for the erection of the first segment are jointly controlled by the measuring points at both ends of the crown and the arch feet. The erection of subsequent segments follows the principle of optimal results and controllable process to control the alignment at the crown end, which is only controlled by the coordinates of the measuring points at the crown end.

[0018] Furthermore, the specific process of step 3 is as follows:

[0019] The cable towers on both banks are respectively arranged on the top of the capping beams of the approach bridge piers. The anchorages on both banks adopt gravity anchorages, which are designed as separated anchorages with an outward eight layout. The Yuqing bank approach bridge is located on a plane curve section, and an integral anchor is set on the left side of the abutment. Combining with the lifting plan of the main bridge components, the cable crane system is designed with two main hoists and two working hoists. The main hoist only traverses when the columns and steel girders are on shore. The saddle is fixed at the axis position of the main bridge arch rib. Through comparative analysis, determine the span combination according to the main span and the length of the approach bridge, select the rated lifting weight according to the weight of the component, determine the working area of the crane according to the lifting points and installation positions of the component, and select the remaining parameters through the calculation results to design the parameters of the cable crane;

[0020] When analyzing the bearing capacity of the cable crane system, the bearing capacity of the cable subsystem, tower subsystem, and anchorage subsystem are respectively checked. The checking of the entire cable crane system is divided into 13 calculation conditions. The working state considers the combined lifting loads of the main hoist and the working hoist and the 6-level wind load, and the non-working state considers the action of the 10-level wind load;

[0021] For the calculation and analysis of the main cable force, when the vertical-span ratio is not greater than 1 / 10, the calculation error can be controlled within 5%, which can meet the accuracy requirements in engineering. Prescribe the maximum sag f of the main cable max = L / 12.5. The rated lifting weight considers a dynamic load coefficient of 1.1, and calculate the horizontal component of the main cable tension under the rated lifting weight according to static analysis:

[0022]

[0023] Where: q is the uniformly distributed load acting on the main cable, L is the main cable span, β is the main cable chord inclination angle, and it is taken as 0 when the cable towers on both sides are of equal height. Q is the concentrated load acting on the main cable. Substituting relevant parameters into the calculation, the horizontal component force and the maximum tension of the main cable are: V is the vertical force component at the top of the tower. The main cable uses 12A60mm steel wire rope. The total breaking force [T] is calculated. The tension safety factor of the main cable under the maximum concentrated load is K = [T] / T max , meet the regulatory requirements;

[0024] The tower was subjected to stress analysis and calculation. The Midas civil finite element analysis software was used to model and calculate the bearing capacity and deformation of the cable tower. In the model, beam units were used to simulate the piers, tower columns and their connecting rods. Tension-only truss units were used to simulate the rear cable wind and ventilation cables. The wind cable anchor end and pier bottom were fully consolidated boundaries.

[0025] Through modeling and calculation, the maximum combined stress of the column steel pipe under the most unfavorable working condition is obtained, and the maximum deviation along the bridge and the deviation to the side span under the most unfavorable working condition of the tower are obtained, which are in line with the recommended values ​​of relevant specifications. At the same time, the buckling mode of the most unfavorable working condition of the overall stability calculation of the cable tower is obtained, which meets the requirements;

[0026] In order to verify the design bearing capacity and working performance of the cable crane system, no-load test, dynamic load test and maximum static load test were carried out in accordance with the principle of step-by-step loading. During the test hoisting process, no anchor displacement or wire rope breakage occurred.

[0027] Furthermore, basic assumptions are made first: the hanger is perpendicular to the longitudinal direction of the bridge, the horizontal force of the main cable is the same over the entire span, the cable between the connection nodes of the main cable and the hanger is assumed to be a straight line rather than a parabola, and the coordinates of the two ends of the load-bearing cable, the sag in the middle of the span, and the position of the hanger point of the hanger on the stiffening beam are known quantities;

[0028] Then, the preliminary form-finding is performed. The specific process of preliminary form-finding is to create a model, define the material and cross-sectional properties of load-bearing cables, cable towers, main beams, hangers and other components, model the main cables according to the actual bulk density, diameter and modulus, set the bulk density of the main beams and hangers to the minimum to facilitate model convergence, enter the suspension bridge modeling assistant, input the positions of the rear anchor, cable tower top and mid-span according to the actual situation, and generate the initial equilibrium state model;

[0029] Then, the initial equilibrium state of the empty cable is used to iterate the line shape of the empty cable to achieve accurate shape finding. Finally, in the PostCS stage of the construction phase, non-construction load loading is carried out. The hoisting weight can be loaded at any position to quickly and accurately calculate the line shape, sag, and tension of the entire length.

[0030] Steps for accurate form finding:

[0031] (1) Delete the geometric non - linear analysis control dialog box on the initial equilibrium state model where the initial form - finding is successful.

[0032] (2) Fix the top of the cable tower, delete the suspender and the main girder, and modify it into the state of the load - bearing cable.

[0033] (3) Select all nodes in the structure group as the update group, select the nodes at the top of the cable tower and at the mid - span as the vertical point group, and the vertical point group serves as the nodes that remain unchanged in the accurate form - finding.

[0034] (4) Select all structures as the overall structure group; select all boundaries as the overall boundary group; select all loads as the overall boundary group, and conduct construction stage analysis. The purpose is to conduct non - linear analysis to find the form that meets the sag requirements under self - weight.

[0035] The present invention has the following beneficial effects due to the adoption of the above - mentioned technical solutions:

[0036] Based on the measured data of the manufacturing form measurement points of the present invention, the absolute displacements of the measurement points obtained by the finite element software analysis are superimposed. Combining the main arch temperature and the variation law of the arch rib form, the erection coordinates are deduced to achieve the dual goals of accurate installation inside the segment and accurate control of the as - built form. A suspension bridge modeling assistant is developed. Using the initial equilibrium state of the empty cable, the form of the empty cable in the actual state is iteratively obtained, and the form, sag, and tension can be quickly and accurately calculated when loading the hanging weight at any position, which can ensure the accuracy during the installation and hoisting process. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is the conversion diagram of the manufacturing form and the erection attitude of the present invention;

[0038] Figure 2 is the marking diagram of the arch crown measurement point of the left - hand side of GL12 in the fourth - round erection of the present invention;

[0039] Figure 3 is the cable - stayed and buckled model diagram of the bridge of the present invention;

[0040] Figure 4 is the total displacement diagram of the vertical tangent erection of the present invention;

[0041] Figure 5 is the total displacement diagram of the transverse - bridge - direction tangent erection of the present invention;

[0042] Figure 6 is the calculation model diagram of the tower of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0043] To make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the following preferred embodiments are given with reference to the accompanying drawings to further elaborate on the present invention. However, it should be noted that many details listed in the specification are merely for enabling the reader to have a thorough understanding of one or more aspects of the present invention, and these aspects of the present invention can be implemented even without these specific details.

[0044] Method for designing the erection line type of the main arch rib of a bridge and the load-bearing cable of a cable crane, the method comprising the following steps:

[0045] Step 1: Design the line type of the main arch rib of the bridge and design the cable crane system according to the line type of the main arch rib of the bridge. Taking the Wujiang Extra-large Bridge as an example, the Wujiang Extra-large Bridge is a control project of the Guizhou Deyu Expressway, with a total length of 1834 m, of which the main bridge span is 504 m, and it is a through-type concrete-filled steel tube arch. It is divided into 15 segments from the column foot to the arch crown, and the arch rib segment numbers are GL1 to GL15. There are a total of 60 segments in the whole bridge, and the maximum lifting weight of a segment is 157 tons. The diameter of the arch rib chord tube is 1.4 m, and C70 self-compacting micro-expansion concrete is poured into the tube. K braces and X braces are arranged between the arch ribs for connection, and the whole arch is connected by 93,000 bolts.

[0046] The idea of the linear control of a fully bolted arch bridge is to control the overall linear quality during the erection stage and restore the relative attitude of the erection in the air. The first step is to obtain the theoretical manufacturing line type.

[0047] The manufacturing line type is obtained by considering the camber on the basis of the design line type.

[0048] The model of the Wujiang Extra-large Bridge is as Figure 4 shown. In the model, each member of the arch rib, the column, the transition pier, and the steel beam are all established with beam elements. There are 2255 nodes and 3996 elements in the calculation model. The camber of the main arch rib is set according to Article 6.2.3 of the "Design Code for Concrete-Filled Steel Tube Arch Bridges of Highways" (JTG / T D65-06-2015). The calculated camber value should be the sum of the cumulative deformation of the dead load, the creep deflection of the concrete-filled steel tube, and 1 / 2 of the live load deflection. After considering the nonlinearity of the camber, according to the specification requirements, the finite element deformation calculation results are extracted. The camber value at the arch crown = (65.1 cm + 11.5 cm + 5.9 / 2 cm) × 1.25 = 99.4 cm. The manufacturing line type at the cross-section position is shown in Table 1.

[0049] Table 1 Coordinates of the manufacturing line type

[0050]

[0051] Wujiang River Extra-large Bridge is a through type concrete-filled steel tubular variable cross-section truss arch bridge with a main span of 475m. The construction technology of cable hoisting + cable-stayed suspension is adopted, and the maximum hoisting weight of components is 155t. Considering the complex geological conditions, large hoisting weight and long span of this bridge, this paper makes a comparison and selection from aspects such as the combination mode of the cable tower and the hoisting tower, the structural form of the anchor, the crane load, etc., and then determines the design parameters of the cable crane. Considering 13 kinds of load condition combinations, the bearing capacity of each subsystem of the cable crane is checked. The main cable is calculated by the approximate analytical method. At the same time, the bearing capacity and deformation of the cable tower are calculated by modeling with finite element analysis software, and a comparative analysis is carried out with the measured load values. The load test shows that the detection indexes of the cable crane system of this bridge all meet the specification requirements and reach the design service conditions, which can provide reference for the design and calculation of similar cable cranes.

[0052] According to the current hoisting plan of the main bridge components, there are a total of 60 segments for the main arch ring, with a maximum net hoisting weight of 155t. Two sets of main cable crane systems are used to hoist the arch rib segments on the upstream and downstream sides respectively, and the single-limb arch ribs are installed separately. After the arch ribs of the same segment on the left and right sides are hoisted in place, the connecting wind braces and cross braces between the segments are installed to complete a double-rib segment unit. The columns and steel girders are first transported by water to the position below the mid-span of the bridge, and then hoisted ashore through the cable crane across the position of the arch top wind brace, and then transported and stored by the hydraulic modular vehicle. To meet the requirements of the lifting space, the wind brace at the arch top is not installed temporarily after the arch rib is closed. After the concrete-filled steel tube is poured and all the columns and steel girders on the arch are hoisted ashore, the arch top wind brace is installed. Among them, the maximum weight of the column is 46.1t, and the weight of the steel girder (including the column top part) is 54.9t. The columns are temporarily stored on the Dejiang side approach bridge, and the steel girders are temporarily stored on the Yuqing side approach bridge, and then hoisted and installed by the cable crane after being assembled into a whole. All steel girder segments are assembled into hoisting segments on the Yuqing bank approach bridge, and then transported to the bridge deck in front of the tower by the hydraulic modular vehicle for hoisting, and two sets of cable cranes are used for lifting and hoisting. For example, if the mid-span is installed first, the initial installed beam segments are 2C + 2A3 + longitudinal and transverse girders with a total weight of 219.43t, and the maximum hoisting weight for lifting is proposed to be 220t. If the installation is carried out from the transition pier to the mid-span, the maximum is 160t. Therefore, the previous working condition is taken for checking during design.

[0053] The tower of the cable crane system adopts a cable-hoisting separation structure. The cable-hoisting and cable systems of the cable-hoisting separation structure operate independently without interference, and the cable force and assembly alignment are easier to control. And by moving the cable tower backward, space is provided for the cable system to hoist the steel girder on the approach bridge deck, realizing the lifting and assembly of the upper structure of the main bridge onto the bridge.

[0054] The anchor of the cable crane system adopts a gravity-type anchor structure, which provides horizontal resistance through the self-weight and the friction force generated by the foundation.

[0055] The lifting weight of the cable crane system adopts an independent lifting structure. The independent lifting structure reduces the transverse movement time during the hoisting of the main arch ring and the time in the state of large cantilever of the arch ring, which can reduce the safety risk. Moreover, by reducing the transverse movement, it can better avoid the Z-shaped hoisting of the arch ribs.

[0056] Step 2: Measure the actual data of the linear measurement points according to the alignment of the arch rib frame, superimpose the absolute displacements of the measurement points obtained by finite element software analysis, and combine the main arch temperature and the variation law of the arch rib alignment to deduce the erection coordinates, so as to achieve the dual goals of precise installation inside the segment and precise control of the as-built alignment.

[0057] The actual attitude of the vertical assembly is reflected by the measurement points at the arch feet and the arch tops. The determination steps are as follows: first set, then collect, and finally mark. And use the measurement points as the carrier of the theoretical three-dimensional deformation of the hoisting attitude. As Figure 1 shown, divide the stress-free alignment of the whole arch into 4 rounds according to the pre-assembly methods of 3+1 and 4+1, and rotate it to the horizontal position for vertical assembly lofting and manufacturing. After the attitude adjustment of each round is in place, take the lower edge groove of the chord tube of each round as the starting point, the horizontal direction as the X-axis, and the vertical direction as the Z-axis. And use a specific tool to find the approximate axis of the upper edge of the upper chord tube. At a position approximately 1m away from the port on it, avoid the crossbeam of the segment arrangement platform and set the measurement point mark. Finally, collect the actual coordinates of the measurement points again. As shown in Table 3, the local coordinates of the measurement points of the left side of GL12 in the vertical assembly stage. At this time, the distance from the center of the inner chord is not necessarily 6.75m. The main reason is that the measurement points are not necessarily on the central axis. In addition, due to manufacturing errors, there is a deviation between the central axis of the chord tube and the theoretical distance from the center value of 6.75m. Reflect the actual coordinates of the measurement points of each round into the local coordinate system. As Figure 2 shown, mark the measurement point at the top of the inner chord of the left side of GL12 on the vertical assembly drawing of the fourth round, and convert the local coordinate system of this round of vertical assembly to the local coordinate system of the arch rib stress-free alignment with the center of the hinge closure surface as the carrier of the theoretical displacement.

[0058] During the assembly of the steel pipe arch, it is similar to a curved beam cable-stayed bridge. Referring to the construction control concept of the cable-stayed bridge, use the Midas / Civil finite element calculation software to establish a finite element model, simulate each stage of the arch bridge assembly construction. The control goal of the calculation is that the deviation between the alignment after the arch rib shackle is removed and the alignment of the first-stage erection is less than 1cm, the deviation of the intermediate pier and the cable tower during the construction process is less than 2cm, and at the same time the cable forces are uniform. After multiple iterations, obtain the initial cable tension in the assembly construction stage that meets the above requirements. The initial tension reflects the stress-free length of the cable. Substitute the initial tension into the forward model and select the external force to conduct the construction stage analysis to obtain the load effects of the structure during the process, which are used to judge the safety of the structure, including the reactions, stresses, deformations, and displacements of the arch, cable, tower, and anchor. At the same time, obtain the key parameters of the tangent assembly, the cable tension value and the total displacement of the component. As Figure 3 、 4As shown in Figure 5, the total vertical displacement is 396 mm, with downward displacement; the total horizontal displacement is 137 mm, towards the abutment; the axis deviation is 68 mm, deflecting outwards.

[0059] The main construction process is shown in Table 2. Since there is an angle between the back cable and the axis, to avoid the cumulative deflection of the buckling tower and resulting in excessive transverse deviation of the arch rib, the left and right arch ribs are advanced in a zigzag pattern, which is reflected in the construction stages in the model.

[0060] Table 2 Main Construction Stages

[0061]

[0062] The erection coordinates of the first segment are jointly controlled by the measuring points at both ends of the crown and the arch feet. For the subsequent segments, the erection follows the principle of optimal results and controllable process to control the crown alignment, which is only controlled by the coordinates of the crown measuring points. Table 3 shows the displacement calculation steps of the inner chord crown measuring points on the left side of GL12, demonstrating the calculation process of superimposing the theoretical deformation on the basis of the actual erection attitude while ensuring the relative attitude.

[0063] Table 3 Displacement Calculation Steps of the Inner Chord Measuring Points on the Left Side of GL12

[0064]

[0065] The linear expansion coefficient of the steel is 1.2×10 -5 , the system temperature and gradient temperature affect the elongation of the arch and the cable. Especially as the cantilever length of the arch rib increases, the back cable also grows, and the influence of temperature on the arch rib alignment becomes gradually significant, resulting in obvious deformation and displacement of the entire cable-stayed buckling hanging system.

[0066] The reason for the temperature is environmental factors, including atmospheric temperature, arch rib temperature, cable temperature, and sunshine angle. Using the Leica TS60 measuring robot, the alignment data of the arch rib is automatically collected all-weather. The data includes the superimposed influence of wind load on the arch rib alignment, and the relationship between the arch rib alignment and the environment is obtained.

[0067] Step 3: Design the parameters of the cable crane system and then conduct a trial hoisting operation. After comparing the design schemes, the cable crane system of Wujiang Extra-large Bridge adopts a tower layout scheme with cable and buckle separation. The cable towers on both banks are respectively arranged on the top of the capping beams of Pier 24# and 28# of the approach bridge. Gravity-type anchorages are used for both banks' anchorages. Affected by the position of the approach bridge on the Dejiang bank, it is designed as a separated anchorages with an outward eight layout. The approach bridge on the Yuqing bank is located in a plane curve section, and an integral anchorage is set on the left side of the 34# abutment. The overall layout of the cable crane is shown in Figure 2-3Combined with the hoisting plan of the main bridge components, the cable crane system is designed with two groups of main hoists, with a rated hoisting capacity of 160t for a single group, and two groups of working hoists, with a rated hoisting capacity of 20t for a single group. The main hoist only traverses when the columns and steel girders come ashore. In other cases, the saddle is fixed at the axis position of the main bridge arch rib. Based on the above comparative analysis, the span combination is determined according to the main span and the length of the approach bridge, the rated hoisting capacity is selected according to the weight of the components, the working area of the crane is determined according to the lifting points and installation positions of the components, and the remaining parameters are selected based on the calculation results. The specific design parameters of the cable crane are shown in Table 4.

[0068] Table 4 Basic Technical Parameters of Cable Crane

[0069]

[0070]

[0071] When calculating the cable crane system, it is necessary to separately check the bearing capacity of each subsystem of the cable, tower, and anchor. Combining the actual hoisting working conditions, the checking calculation of the entire cable crane system is divided into 13 calculation working conditions. The working state considers the combination of various hoisting loads of the main hoist and the working hoist as well as the 6-level wind load, and the non-working state considers the action of the 10-level wind load. The summary of the calculation working conditions is shown in Table 5.

[0072] Table 5 Summary of Calculation Working Conditions

[0073]

[0074]

[0075] In engineering, the approximate analytical method based on the parabola theory is usually adopted for the calculation of the main cable. When the sag-span ratio is not greater than 1 / 10, the calculation error can be controlled within 5%, which can meet the accuracy requirements of the project. In this project, the maximum sag f of the main cable is max = L / 12.5 = 49.92m. Considering a dynamic load coefficient of 1.1 for the rated hoisting weight, the horizontal component of the main cable tension under the rated hoisting weight is calculated according to static analysis:

[0076]

[0077] In the formula: q is the uniform load acting on the main cable, L is the span of the main cable, β is the chord inclination angle of the main cable, which is taken as 0 when the cable towers on both banks are of the same height, Q is the concentrated load acting on the main cable. Substituting the relevant parameters, H max = 9585kN is obtained. Thus, the maximum tension of the main cable V is the vertical component force at the top of the tower. The main cable uses 12A60mm steel wire ropes, and the total breaking force [T] = 12×2400 = 28800kN. Therefore, the safety factor K of the main cable tension under the maximum concentrated load is K = [T] / T max = 3.1 ≥ 3, meeting the specification requirements.

[0078] Midas civil finite element analysis software is used to model and calculate the bearing capacity and deformation of the cable tower. In the model, beam units are used to simulate piers, tower columns and their connecting rods. Tension-only truss units are used to simulate rear cable wind and ventilation cables. The wind cable anchor end and pier bottom use fully consolidated boundaries. The calculation model is shown in Figure 6 .

[0079] Through modeling calculation, the most unfavorable working condition for the column steel pipe is working condition 5, with the maximum combined stress of -169.3MPa, which is less than the design value of steel strength 305MPa. The most unfavorable tower deviation is working condition 10, with the maximum deviation along the bridge direction of 18cm, and the deviation to the side span, which meets the requirements of the relevant specifications that the recommended value is not greater than H / 400=18.2cm. The most unfavorable calculation of the overall stability of the cable tower is working condition 8, with the buckling mode of 21.2, which is greater than 4 and meets the requirements.

[0080] In order to verify the design bearing capacity and working performance of the cable crane system, no-load test, dynamic load test and maximum static load test were carried out in accordance with the principle of step-by-step loading. During the test hoisting process, there was no displacement of anchors or breakage of wire ropes. The anchors and connectors were stable and firm. The runners and pulleys operated normally. The winch and its control system worked normally. According to the measured data of the test hoisting, the sag of the main cable was highly consistent with the theoretical calculated value. The stress of the cable tower column and the displacement of the tower frame were basically consistent with the overall trend of the theoretical calculation. However, the specific values ​​showed certain differences. The measured value of the tower column stress was generally smaller. The main reasons for this difference may be:

[0081] (1) In theoretical calculation, the cable tower model in working condition was analyzed with a level 6 wind load applied in the unfavorable direction. However, in actual operation, the direction and magnitude of the wind load on the cable tower vary within a certain range and are not fixed values.

[0082] (2) During modeling and calculation, the tower is a continuous rigid connection structure. In reality, bolts are used to connect the spliced ​​segments of the tower. The former is a linear deformation, while the latter will present certain nonlinear characteristics due to the difference in the tightening degree of the bolts.

[0083] The model load takes into account the dynamic coefficient and has a certain degree of amplification, and the relevant loads are generally conservatively taken, which is larger than the actual loads.

[0084] Step 4: Analyze and calculate the linear shape, sag, and tension of the cable crane load-bearing cables, and then use the cable crane system to install the main arch rib frame of the bridge.

[0085] To verify the design bearing capacity and working performance of the cable crane system, the no-load test, dynamic load test, and maximum static load test were carried out successively in accordance with the principle of step-by-step loading. During the trial hoisting process, no anchor displacement or wire rope fracture occurred. All anchor fittings and connectors were stable and firm. The running car and pulley operated normally, and the winch and its control system worked normally. According to the measured data of the trial hoisting, the sag of the main cable was highly consistent with the theoretically calculated value, as shown in Figure 5 , the stress of the cable tower column and the deviation of the tower frame were basically consistent with the overall trend of the theoretical calculation, but there were certain differences in the specific values. Among them, the measured value of the tower column stress was generally on the small side, as shown in Figure 6 . The main reasons for this difference may be:

[0086] (3) During theoretical calculation, a 6-level wind load was applied to the cable tower model in the unfavorable direction for the analysis of the working state. However, during actual operation, the direction and magnitude of the wind load acting on the cable tower changed within a certain range and were not fixed values;

[0087] (4) During modeling calculation, the tower frame was a continuous rigid connection structure, while in actuality, the tower frame splicing segments were connected by bolts. The former was linear deformation, and the latter would exhibit certain non-linear characteristics due to differences in bolt tightening degrees.

[0088] The dynamic coefficient was considered in the model load, resulting in a certain amplification, and the relevant loads were generally taken on the conservative side, being larger than the actual loads.

[0089] (1) The suspender is perpendicular to the longitudinal direction of the bridge.

[0090] (2) The horizontal force of the main cable is the same across the entire span.

[0091] (3) It is assumed that the cable between the connection nodes of the main cable and the suspender is in a straight line shape rather than a parabolic shape.

[0092] (4) The coordinates of both ends of the load-bearing cable, the mid-span sag, and the suspension point positions of the suspenders on the stiffening girder are known quantities.

[0093] Steps for preliminary shape finding:

[0094] (1) Create a model and define the materials and cross-sectional properties of components such as the load-bearing cable, cable tower, main girder, and suspenders. The main cable is modeled based on the actual unit weight, diameter, and modulus. The unit weight of the main girder and suspenders is set to a very small value to facilitate model convergence.

[0095] (2) Enter the suspension bridge modeling assistant and input the positions of the back anchor, cable tower top, and mid-span according to the actual situation.

[0096] (3) Generate the initial equilibrium state model

[0097] Steps for precise shape finding:

[0098] (1) Delete the "Geometric Nonlinear Analysis Control" dialog box on the initial equilibrium state model where the initial form-finding is successful.

[0099] (2) Fix the top of the cable tower, delete the suspenders and the main girder, and modify it to the load-bearing cable state.

[0100] (3) Select all the nodes in the structure group as the update group, select the nodes at the top of the cable tower and at the mid-span as the hanging point group, and the hanging point group is the nodes that remain unchanged in the accurate form-finding.

[0101] (4) Select all the structures as the overall structure group; select all the boundaries as the overall boundary group; select all the loads as the overall boundary group, and perform the construction stage analysis. The purpose is to perform nonlinear analysis to find the form that meets the sag requirements under self-weight.

[0102] Taking the rated lifting load of 160 tons per single group as an example, demonstrate the calculation process of the finite element method. For the sag in the unloaded cable state, the mid-span node is 46, the Z coordinate is 105.65 m, and the cable tower top node is 31, the Z coordinate is 137.7 m. Subtracting them gives the sag in the unloaded cable state as 32.05 m.

[0103] For the sag with a 160-ton load at the mid-span, the mid-span node is 46, and the vertical displacement is 18.032 m based on the unloaded cable state. Therefore, the sag with a 160-t load at the mid-span is 32.05 + 18.032 = 50.082 m.

[0104] For the internal force in the unloaded cable state, the position with the maximum tension appears at the saddle, which is 23.5 t. For the internal force with a 160-ton load at the mid-span, the position with the maximum tension appears at the saddle, which is 81.7 t.

[0105] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. Design method for erection alignment of main arch rib of bridge and load-bearing cable of cable crane, characterized in that, The method includes the following steps: Step 1: Design the alignment of the main arch rib of the bridge, and design the cable crane system according to the alignment of the main arch rib of the bridge; Step 2: Measure the actual data of the linear measurement points according to the alignment of the arch rib, superimpose the absolute displacement of the measurement points obtained by finite element software analysis, combine the main arch temperature and the variation law of the arch rib alignment, and deduce the erection coordinates to achieve the dual goals of precise installation inside the segment and precise control of the as-built alignment; Step 3: Design the parameters of the cable crane system and then conduct a trial hoisting operation; Step 4: Analyze and calculate the alignment, sag, and tension of the load-bearing cable of the cable crane, and then hoist and construct the main arch rib of the bridge using the cable crane system; The specific process of Step 2 is as follows: First, determine the actual attitude of the vertical assembly. The actual attitude of the vertical assembly is reflected by the measurement points at the arch foot and the arch top. The determination steps are as follows: first set, then collect, and finally mark. Using the measurement points as the carrier of the theoretical three-dimensional deformation of the hoisting attitude, divide the stress-free alignment of the entire arch into 4 rounds according to the pre-assembly method and rotate it to the horizontal position for easy vertical assembly lofting and manufacturing. After the attitude adjustment of each round is in place, taking the lower edge groove of the chord tube of each round as the starting point, with the horizontal direction as the X-axis and the vertical direction as the Z-axis, and using tools to find the approximate axis of the upper edge of the upper chord tube. At a position 1m above the port, avoid the crossbeam of the segment arrangement platform and set the measurement point mark. Finally, collect the actual coordinates of the measurement points. The local coordinates of the left-side measurement points in the vertical assembly stage have a deviation of 6.75m between the central axis of the chord tube and the theoretical center distance value. Reflect the actual coordinates of the measurement points of each round into the local coordinate system, mark the left-side inner chord arch top measurement point on the fourth-round vertical assembly drawing, and convert the local coordinate system of the corresponding round of vertical assembly to the local coordinate system of the arch rib stress-free alignment with the center of the hinge closure surface as the carrier of the theoretical displacement; Second, displace the theory of the assembly attitude. During the assembly of the steel pipe arch, it is set as a curved beam cable-stayed bridge. Use the Midas / Civil finite element calculation software to establish a finite element model to simulate each stage of the arch bridge assembly construction. The control objective of the calculation is that the deviation between the alignment after the arch rib shackle removal and the alignment of the first-time erection is less than 1cm, the deviation of the intermediate pier and the cable tower during construction is less than 2cm, and at the same time, the cable force is uniform. After several iterations, obtain the initial cable tension in the assembly construction stage that meets the requirements. The initial tension reflects the stress-free length of the cable. Substitute the initial tension into the forward model and select the external force to conduct a construction stage analysis to obtain the load effect of the structure during the process for judging the safety of the structure, including the reaction force, stress, deformation, and displacement of the arch, cable, tower, and anchor. At the same time, obtain the key parameters of the tangent assembly, the cable tension value, and the total displacement of the component. The total vertical displacement is 396mm, downward displacement, the total horizontal displacement is 137mm, towards the arch seat direction, and the axis deviation is 68mm, deflecting outward; Third, set the erection coordinates. The erection coordinates of the first segment are jointly controlled by the measurement points at both ends of the arch top and the arch foot. The subsequent segments are erected following the principle of optimal results and controllable process, controlling the alignment of the arch top, which is only controlled by the coordinates of the measurement points at the arch top.

2. The design method for erection alignment of main arch rib of bridge and load-bearing cable of cable crane according to claim 1, characterized in that: In Step 1, the alignment control of the fully bolted arch bridge is to control the overall alignment quality during the erection stage and restore the relative erection attitude in the air. The first step is to obtain the theoretical manufacturing alignment. The manufacturing alignment is obtained by adding a camber on the basis of the designed alignment. The main arch rib frame model of the bridge includes arch rib members, columns, transition piers, and steel girders. The arch rib members, columns, transition piers, and steel girders are all established with beam elements. The tower of the cable crane system adopts a cable and buckle separation structure. The buckling and cable systems of the cable and buckle separation structure operate independently without interference. The cable force and erection alignment are easier to control. Moreover, by moving the cable tower backward, space is provided for the cable system to lift the steel girder on the approach bridge deck, realizing the lifting and assembly of the superstructure of the main bridge. The anchor of the cable crane system adopts a gravity anchor structure, which provides horizontal resistance through the friction force generated by its own weight and the foundation. The lifting weight of the cable crane system adopts an independent lifting structure. The independent lifting structure reduces the time of transverse movement during the hoisting of the main arch ring and the time in the state of large cantilever of the arch ring, which can reduce the safety risk. Moreover, by reducing the transverse movement, it can better avoid the Z-shaped hoisting of the arch rib.

3. The design method for erection alignment of main arch rib of bridge and load-bearing cable of cable crane according to claim 1, characterized in that: The specific process of Step 3 is as follows: The cable towers on both banks are respectively arranged on the top of the pier capping beams of the approach bridges. The anchors on both banks adopt gravity anchor structures, which are designed as separated anchors arranged in an outward V shape. The Yuqing bank approach bridge is located in a plane curve section, and an integral anchor is set on the left side of the abutment. Combining with the hoisting plan of the main bridge components, the cable crane system is designed with two main hoists and two working hoists. The main hoist only moves transversely when the columns and steel girders are hoisted onto the shore. The saddle is fixed at the axis position of the main bridge arch rib. Through comparative analysis, the span combination is determined according to the main span and the length of the approach bridge, the rated lifting weight is selected according to the weight of the components, the working area of the crane is determined according to the lifting points and installation positions of the components, and the other parameters are selected through the calculation results, and the parameters of the cable crane are designed. During the bearing capacity analysis of the cable crane system, the bearing capacity of the cable subsystem, tower subsystem, and anchor subsystem are respectively checked. The check of the entire cable crane system is divided into 13 calculation conditions. The working state considers the combination of the hoisting loads of the main hoist and working hoist and the 6-level wind load, and the non-working state considers the action of the 10-level wind load. For the force calculation and analysis of the main cable, when the sag-span ratio is not greater than 1 / 10, the calculation error can be controlled within 5%, which can meet the accuracy requirements of the project. The maximum sag f of the main cable is specified as max = L / 12.

5. Considering a dynamic load factor of 1.1 for the rated lifting weight, the horizontal component of the main cable tension under the rated lifting weight is calculated according to static analysis: Where: q is the uniformly distributed load acting on the main cable, L is the span of the main cable, β is the chord inclination angle of the main cable, which is taken as 0 when the cable towers on both banks are of the same height, Q is the concentrated load acting on the main cable, and the horizontal component force is calculated by substituting relevant parameters, and the maximum tension of the main cable V is the vertical component force at the top of the tower. The main cable uses 12A60mm steel wire rope, and the total breaking force [T] is calculated. The tensile safety factor K of the main cable under the maximum concentrated load is K = [T] / T max , meeting the requirements of the specification; For the force analysis and calculation of the tower, the Midas civil finite element analysis software is used to model and calculate the bearing capacity and deformation of the cable tower. In the model, beam elements are used to simulate the pier columns, tower column and its connecting rods, and only tension truss elements are used to simulate the rear guy cables and ventilation cables. The full consolidation boundary is adopted for the cable anchor end and the pier bottom. Through the modeling calculation, the maximum combined stress of the most unfavorable condition of the column steel pipe is obtained, the maximum deviation in the longitudinal direction of the most unfavorable condition of the tower deviation is obtained, and the deviation is towards the side span, which meets the recommended values of relevant specifications. At the same time, the buckling mode of the most unfavorable condition of the overall stability calculation of the cable tower is obtained, which meets the requirements. To verify the designed bearing capacity and working performance of the cable crane system, the no-load test, dynamic load test, and maximum static load test are successively carried out in accordance with the principle of step-by-step loading. During the test hoisting process, no anchor displacement or wire rope fracture occurred.

4. The design method for erection alignment of main arch rib of bridge and load-bearing cable of cable crane according to claim 1, characterized in that: First, make basic assumptions. The suspension rod is perpendicular to the longitudinal direction of the bridge, the horizontal force of the main cable is the same across the entire span. Assume that the cable between the connection nodes of the main cable and the suspension rod is in a straight line shape, rather than a parabolic shape. The coordinates of both ends of the load-bearing cable, the mid-span sag, and the suspension point positions of the suspension rods on the stiffening girder are known quantities; Then, perform preliminary shape finding. The specific process of preliminary shape finding is to create a model, define the materials and cross-sectional properties of the components of the load-bearing cable, cable towers, main girders, and suspension rods. The main cable is modeled according to the actual unit weight, diameter, and modulus. The unit weights of the main girder and suspension rods are set to the minimum to facilitate model convergence. Enter the suspension bridge modeling assistant, input the positions of the back anchor, cable tower top, and mid-span according to the actual situation, and generate the initial equilibrium state model; Next, use the initial equilibrium state of the unloaded cable to iterate the unloaded cable alignment and achieve accurate shape finding. Finally, in the PostCS stage of the construction stage, apply non-construction stage loads. The hanging weight can be applied at any position to quickly and accurately calculate the alignment, sag, and tension of the entire length; Steps for accurate shape finding: (1) Delete the geometric non-linearity analysis control dialog box from the initial equilibrium state model with successful preliminary shape finding; (2) Fix the cable tower top, delete the suspension rods and main girders, and modify them to the load-bearing cable state; (3) Select all nodes in the structure group as the update group, and select the nodes at the cable tower top and mid-span as the vertical point group. The vertical point group is the invariant node in the accurate shape finding; (4) Select all structures as the overall structure group; select all boundaries as the overall boundary group; select all loads as the overall boundary group, and perform construction stage analysis. The purpose is to perform non-linearity analysis to find the alignment that meets the sag requirements under self-weight.

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