A stress calculation method for cable saddle region in partial cable-stayed bridge

Abstract

The application discloses a stress calculation method for a cable saddle area in a partial cable-stayed bridge. First spring units are established between adjacent split tubes, and second spring units are established between the split tubes and cable towers / bridges. The stress calculation method comprises the following steps: a finite element model is established according to design parameters of the split tubes, the stiffness of the first spring units and the second spring units is adjusted in the finite element model for multiple times, then the displacement of each node is accumulated, the second downward pressure of each split tube on concrete is obtained, the second downward pressure is applied to a solid finite element model of the saddle, and finally the stress distribution of the cable saddle area is obtained. The application adopts nonlinear spring units to simulate the contact action between the split tubes and the split tubes and between the split tubes and the concrete, is easy to program, and can obtain relatively accurate calculation results at a relatively small calculation cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bridge engineering, in particular to a stress calculation method for a cable saddle region in a partial cable-stayed bridge. BACKGROUND

[0002] In recent years, the partial cable-stayed bridge has been widely promoted, and has become one of the most competitive bridge types between 100-300m span due to its unique mechanical properties and aesthetic value. At present, the cable systems of the partial cable-stayed bridges built at home and abroad mostly adopt the split-wire pipe cable saddle system, and the material selection, structure, pipe connection mode and geometric arrangement of the split-wire pipe will affect the force transmission effect of the cable saddle, the local stress and reinforcement of the tower, and directly determine the rationality of the cable distance and structural size on the main tower.

[0003] The current bridge specification does not have an inspection standard for the split-wire pipe used in the partial cable-stayed bridge. In order to clarify the spatial stress condition of the main tower concrete around the split-wire pipe and ensure the rationality of the local area reinforcement in the tower, a spatial finite element model is mostly used for stress analysis during the design. For the simulation of the split-wire pipe, the split-wire pipe is currently mostly simulated by coupling it into a whole, but in fact, the split-wire pipe is not a whole between the split-wire pipes except for the full welding on the periphery, and the segment welding between any two pipes inside the split-wire pipe. This simulation method cannot consider the stress redistribution caused by the friction sliding between the split-wire pipes, and the entire cable generates a large tensile stress on the upper edge of the concrete, so the overall calculation result is unsafe. Another possible calculation method in the prior art is to completely ignore the segment welding between the split-wire pipes, and to consider the interaction between the split-wire pipes by setting the friction coefficient between the split-wire pipes and the friction coefficient between the split-wire pipes and the concrete during the calculation. This simulation method can well reflect the stress redistribution caused by the sliding between the split-wire pipes, but the boundary conditions of this calculation method are complex, the calculation is difficult to converge, and it is difficult to be used in engineering practice. SUMMARY

[0004] In view of the above problems, the present application provides a stress calculation method for a cable saddle region in a partial cable-stayed bridge, which overcomes the above problems or at least partially solves the above problems, can solve the problem of inaccurate or impractical stress calculation in the prior art, and can obtain a more accurate calculation result with a small calculation cost.

[0005] Specifically, the present application provides a stress calculation method for a cable saddle region in a partial cable-stayed bridge, the partial bridge comprising a bridge and a tower erected on the bridge, a plurality of split-wire pipes being connected between the bridge and the tower, a first spring unit being arranged between adjacent split-wire pipes, and a second spring unit being arranged between the split-wire pipes and the tower.

[0006] The stress calculation method comprises:

[0007] S1: determining a first downward pressure of each of the sub-wire pipes according to a cable force and an angle of the cable;

[0008] S2: obtaining design parameters of the sub-wire pipes;

[0009] S3: calculating axial compression stiffness and tangential stiffness of the sub-wire pipes according to the design parameters of the sub-wire pipes;

[0010] S4: establishing a finite element model according to the axial compression stiffness, the tangential stiffness, and coordinates of the first spring unit and the second spring unit;

[0011] S5: in the finite element model, applying 1 / 1000 of the first downward pressure value, and calculating a result of node displacement;

[0012] S6: repeating steps S4 and S5 1000 times, accumulating displacement amounts of all nodes, and obtaining a second downward pressure of the sub-wire pipes on concrete according to the node displacement amounts;

[0013] S7: applying the second downward pressure to a solid finite element model of the saddle, so as to obtain a stress distribution of a cable saddle area.

[0014] Optionally, the design parameters are obtained by drawing the sub-wire pipe structure, the first spring unit and the second spring unit in CAD software, and automatically reading the corresponding design parameters.

[0015] Optionally, the design parameters at least include pipe diameters, pipe wall thicknesses and pipe positions of the sub-wire pipes.

[0016] Optionally, in step S3, a plane strain unit is established according to the design parameters of the sub-wire pipes, and the axial compression stiffness and the tangential stiffness of the sub-wire pipes are calculated according to the plane strain unit.

[0017] Optionally, in the finite element model in step S4, initial axial stiffness and tangential stiffness of the first spring unit and the second spring unit are directly or indirectly obtained by using data calculated in step S3.

[0018] Optionally, the initial axial stiffness and the tangential stiffness of the first spring unit are obtained by using data calculated in step S3.

[0019] Optionally, the initial axial stiffness and the tangential stiffness of the second spring unit in the lower half are obtained by using data calculated in step S3.

[0020] Optionally, the initial axial stiffness and tangential stiffness of the second spring unit of the upper half is 1 / 1000 of the data calculated in step S3.

[0021] Optionally, step S5 comprises:

[0022] According to the axial tension of the first spring unit and / or the second spring unit, the axial stiffness and tangential stiffness are adjusted to 1 / 1000 of the original, and when the tangential force of the first spring unit and / or the second spring unit is greater than 0.5 times the axial force, the tangential stiffness is adjusted to 1 / 1000 of the original, and the axial stiffness is unchanged. Adjust the axial stiffness and tangential stiffness of each first spring unit and / or second spring unit.

[0023] Optionally, if there is an unbalanced force after calculation in step S5, the unbalanced force is applied to the finite element model.

[0024] The beneficial effects of the present application are:

[0025] 1. In the stress calculation method provided by the present application, the nonlinear spring unit is used to simulate the contact action between the split wire pipes and the split wire pipes, and between the split wire pipes and the concrete, so that the solving speed is fast, the physical concept is clear, and the program can be easily programmed. Through the programmed program, the designer only needs to draw the diameter, wall thickness and coordinate position of the split wire pipe in the CAD software to complete the modeling, which greatly improves the work efficiency.

[0026] 2. In the stress calculation method provided by the present application, the pre-contact and explicit solving method is used to improve the convergence speed of the solution. By pre-setting the contact conditions between the split wire pipes and the split wire pipes, and between the split wire pipes and the concrete, and using the explicit step-by-step accumulation solving method, the convergence speed is fast.

[0027] 3. Further, according to the stress calculation method provided by the present application, the designer can automatically generate the static model of ABAQUS through the programmed program according to the calculated down pressure calculation result and the imported geometric information, the designer does not need to repeat the modeling, which greatly improves the work efficiency.

[0028] The above and other objects, advantages and features of the present application will become more apparent from the following detailed description of some embodiments thereof, taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0029] Some specific embodiments of the present application will be described in detail below with reference to the accompanying drawings, which are exemplary and not limiting. The same reference signs in the drawings indicate the same or similar components or parts. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings:

[0030] Figure 1 This is a schematic structural diagram of a partially cable-stayed bridge, based on an embodiment of the present invention, for stress calculation in the cable saddle region of a partially cable-stayed bridge.

[0031] Figure 2 This is a schematic cross-sectional view of the bridge along a first direction in a stress calculation method for the cable saddle region in a partially cable-stayed bridge according to an embodiment of the present invention.

[0032] Figure 3 yes Figure 2 A schematic enlarged view of part A in the middle;

[0033] Figure 4 This is a schematic cross-sectional view of the bridge along the second direction in a stress calculation method for the cable saddle region in a partially cable-stayed bridge according to an embodiment of the present invention.

[0034] Figure 5 This is a schematic cross-sectional view of the wire tube in a stress calculation method for the cable saddle region of a partially cable-stayed bridge according to an embodiment of the present invention.

[0035] In the diagram: 100, pier; 200, bridge; 300, tower; 310, saddle; 400, branch pipe; 510, first spring unit; 520, second spring unit. Detailed Implementation

[0036] The following reference Figures 1 to 5 This invention describes a method for stress calculation in the cable saddle region of a partially cable-stayed bridge, according to embodiments of the present invention. In this description, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature, that is, include one or more of that feature. In the description of the present invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified. When a feature "includes or contains" one or more of the features it encompasses, unless otherwise specifically described, this indicates that other features are not excluded and may be further included.

[0037] Unless otherwise expressly specified and limited, the terms "set up," "install," "connect," "link," "fix," and "couple" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art should be able to understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0038] Further, in the description of the embodiments, the first feature being "on" or "under" the second feature can include the first and second features being in direct contact, or can include the first and second features not being in direct contact but being in contact through another feature between them. That is, in the description of the embodiments, the first feature being "on", "above", and "over" the second feature includes the first feature being directly above and obliquely above the second feature, or merely means that the first feature is higher in horizontal height than the second feature. The first feature being "under", "below", or "underneath" the second feature can be the first feature being directly below or obliquely below the second feature, or merely means that the first feature is lower in horizontal height than the second feature.

[0039] In the description of the embodiments, the description with reference to the terms "one embodiment", "some embodiments", "exemplary embodiment", "example", "specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the exemplary description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples.

[0040] Figure 1 is a schematic structural diagram of a partial cable-stayed bridge according to an embodiment of the stress calculation method for the cable saddle region in the partial cable-stayed bridge, as shown in Figure 1 , and with reference to Figures 2 to 5 , the embodiment of the present application provides a stress calculation method for the cable saddle region in a partial cable-stayed bridge. The partial cable-stayed bridge comprises bridge piers 100 arranged at intervals and a bridge 200 fixed on the bridge piers 100, and the bridge 200 is vertically provided with a cable tower 300. As shown in Figures 2 to 4 , the cable tower 300 is fixed with a plurality of cable saddles 310 penetrating through it, and the two ends of each cable saddle 310 are connected with one end of a plurality of filament tubes 400, and the other end of the plurality of filament tubes 400 is connected with the bridge 200. The filament tubes 400 connected with the bridge 200 are arranged in sequence and at intervals along the extension direction of the bridge 200. The part of the filament tube 400 connected with each cable saddle 310 is arranged in close proximity. As shown in Figure 5 , a first spring unit 510 is arranged between adjacent filament tubes 400, and a second spring unit 520 is arranged between the filament tube 400 and the cable tower 300; each first spring unit 510 has two nodes and four degrees of freedom, so that the filament tube 400 has axial stiffness and tangential stiffness. The axial stiffness is used to simulate the compression of the pipeline, and the tangential stiffness is used to simulate the shear deformation of the pipeline.

[0041] When the spring is axially tensioned, the axial stiffness and the tangential stiffness will be set to 0 to simulate that the pipes are no longer in contact with each other; when the tangential force provided by the spring is greater than the maximum static friction force, the tangential stiffness will be set to 0 to simulate that the pipes slide with each other, the concrete boundary at the bridge 200 or the cable tower 300 in contact with the split wire pipe 400 can establish multiple nodes, and these nodes establish a second spring unit 520 with the adjacent split wire pipe 400, and the nodes on the concrete boundary will be completely fixed to simulate the concrete saddle.

[0042] The stress calculation method comprises:

[0043] S1: according to the cable force and the angle of the cable, determine the first downward pressure of each split wire pipe 400 channel;

[0044] S2: draw the split wire pipe 400 structure and spring unit as shown in the attached Figure 5 drawing in the CAD software, automatically read the design parameters of the split wire pipe 400, such as the pipe diameter, pipe wall thickness, pipe position, etc. of the split wire pipe 400 by programming.

[0045] S3: according to the diameter and wall thickness of the split wire pipe 400, establish a plane strain unit, and then calculate the axial compression stiffness and tangential stiffness of the pipe;

[0046] S4: according to the axial compression stiffness and tangential stiffness calculated in step S3, and the position of the first spring unit 510 and the second spring unit 520 drawn in step S1, establish a finite element model. The initial axial stiffness and tangential stiffness of the first spring unit 510 between the split wire pipes 400 adopt the stiffness calculated in step S3. The initial axial stiffness and tangential stiffness of the second spring unit 520 between the lower split wire pipes 400 and the concrete adopt the stiffness calculated in the second step, and the initial axial stiffness and tangential stiffness of the second spring unit 520 between the upper split wire pipes 400 and the concrete adopt 1 / 1000 of the stiffness calculated in the second step, thereby establishing an initialized truss finite element model;

[0047] S5: in the finite element model, apply 1 / 1000 of the first downward pressure of the split wire pipe 400 determined in step S1, and adjust the stiffness of each first spring unit 510 and second spring unit 520 according to the calculation results of the node displacement. Specifically, according to the principle that when the unit is axially tensioned, the axial stiffness and the tangential stiffness are adjusted to 1 / 1000 of the original, when the tangential force of the unit is greater than 0.5 (the friction coefficient of the split wire pipe 400) times the axial force, the tangential stiffness is adjusted to 1 / 1000 of the original, and the axial stiffness remains unchanged, and the stiffness of the rest remains unchanged. If there is an unbalanced force after the last solution, the unbalanced force is applied to the system, and the displacement of each node is accumulated.

[0048] S6: repeating steps S4, S5 1000 times, accumulating the displacement amount of each node, and obtaining the second pressing force of each filament tube 400 on the concrete according to the node displacement amount;

[0049] S7: applying the second pressing force to the entity finite element model of the saddle, so as to obtain the stress distribution of the region of the cable saddle 310.

[0050] Compared with the prior art, the embodiment of the application adopts a special nonlinear spring unit to simulate the contact action between the filament tubes 400 and between the filament tubes 400 and the concrete, has fast solving speed, clear physical concept, and is easy to program; through the programmed program, the designer only needs to draw the diameter, wall thickness and coordinate position of the filament tube 400 in the CAD software to complete the modeling, and the work efficiency is greatly improved.

[0051] Since the embodiment of the application adopts the pre-contact and explicit solving method, the convergence speed of solving is improved. By pre-setting the contact conditions between the filament tubes 400 and between the filament tubes 400 and the concrete, and adopting the explicit step-by-step accumulation solving method, the convergence speed is fast.

[0052] According to the embodiment of the application, the designer can automatically generate the static model of ABAQUS through the programmed program according to the calculation result of the pressing force and the imported geometric information, the designer does not need to repeat the modeling, and the work efficiency is greatly improved.

[0053] According to the embodiment of the application, the designer only needs to input the diameter, wall thickness and coordinate position of the filament tube 400 into the system, and the modeling analysis can be completed, so that the interaction between the filament tubes 400 can be accurately analyzed at a small calculation cost, the analysis speed is fast, and the work efficiency is improved. Since complex contact setting and convergence adjustment are not needed, the work efficiency is greatly improved, the analysis result can better guide the reinforcement design, the reinforcement of the cable saddle 310 is no longer blind, and good economic benefits are obtained.

[0054] At this point, those skilled in the art should recognize that, although the multiple exemplary embodiments of the application have been shown and described in detail herein, many other variations or modifications can be determined or deduced directly from the disclosure of the application according to the principles of the application without departing from the spirit and scope of the application. Therefore, the scope of the application should be understood and recognized as covering all these other variations or modifications.

Claims

1. A stress calculation method for a cable saddle region in a partially cable-stayed bridge, characterized by, The partial cable-stayed bridge comprises a bridge and a cable tower erected on the bridge, a plurality of split wire pipes are connected between the bridge and the cable tower, a first spring unit is arranged between adjacent split wire pipes, and a second spring unit is arranged between the split wire pipe and the cable tower; The stress calculation method comprises: S1: determining a first downward pressure of each split wire pipe according to a cable force and an angle of the cable; S2: obtaining design parameters of the split wire pipe; the design parameters at least include a pipe diameter, a pipe wall thickness and a pipe position of the split wire pipe; S3: calculating an axial compression stiffness and a tangential stiffness of the split wire pipe according to the design parameters of the split wire pipe; S4: establishing a finite element model according to the axial compression stiffness, the tangential stiffness and coordinates of the first spring unit and the second spring unit; S5: in the finite element model, 1 / 1000 of the first downward pressure value is applied, and a node displacement result is calculated; The stiffness of each first spring unit and / or second spring unit is adjusted according to the following principles: When the first spring unit and / or the second spring unit is axially tensioned, the axial stiffness and the tangential stiffness are adjusted to 1 / 1000 of the original; When the tangential force of the first spring unit and / or the second spring unit is greater than 0.5 times the axial force, the tangential stiffness is adjusted to 1 / 1000 of the original, and the axial stiffness remains unchanged; In other cases, the stiffness remains unchanged; If there is an unbalanced force after the last solution, the unbalanced force is applied to the system, and the displacement of each node is accumulated; S6: repeating steps S4 and S5 1000 times, accumulating the displacement of each node, and obtaining a second downward pressure of each split wire pipe on the concrete according to the node displacement; S7: applying the second downward pressure to the solid finite element model of the saddle to obtain the stress distribution of the cable saddle area.

2. The stress calculation method for the cable saddle area in the partial cable-stayed bridge according to claim 1, wherein the design parameters are obtained in CAD software by drawing the split wire pipe structure, the first spring unit and the second spring unit, and automatically reading the corresponding design parameters.

3. The stress calculation method for the cable saddle area in the partial cable-stayed bridge according to claim 1, wherein in step S3, a plane strain unit is first established according to the design parameters of the split wire pipe, and the axial compression stiffness and the tangential stiffness of the split wire pipe are calculated according to the plane strain unit.

4. The stress calculation method for the cable saddle area in the partial cable-stayed bridge according to claim 1, wherein in the finite element model in step S4, the initial axial stiffness and the tangential stiffness of the first spring unit and the second spring unit are directly or indirectly obtained by calculation in step S3.

5. The stress calculation method for the cable saddle area in the partial cable-stayed bridge according to claim 4, wherein the initial axial stiffness and the tangential stiffness of the first spring unit are obtained by calculation in step S3.

6. The stress calculation method for the cable saddle area in the partial cable-stayed bridge according to claim 4, wherein ​ ​ ​ ​ The initial axial stiffness and the initial tangential stiffness of the second spring unit of the lower half are calculated using the data obtained in step S3. 7.The stress calculation method for a cable saddle region in a partial cable-stayed bridge according to claim 4, wherein, The initial axial stiffness and the initial tangential stiffness of the second spring unit of the upper half are 1 / 1000 of the data calculated in step S3.

Images