Aeroelastic model of truss girder and cable-stayed bridge tower

Abstract

The invention relates to the technical field of bridge engineering, and particularly discloses a truss girder and cable-stayed bridge tower aeroelastic model which comprises a truss girder and a bridge tower. The truss beam is divided into a plurality of beam sections, and each beam section comprises a chord member core beam, a vertical web member core beam and a cross beam core beam; the bridge tower comprises an upper tower column core beam, two or more layers of parallel steel bar sets are installed at the bottom of the upper tower column core beam, each steel bar set comprises four steel bars, and the four steel bars extend in four directions respectively. The four lower tower column core beams are connected to the end parts of the four steel bars, and the two lower tower columns are connected to the end parts of the four steel bars; the upper tower column core beam and the lower tower column core beam are sleeved with a second outer mold. The invention aims to provide a truss girder and cable-stayed bridge aeroelastic model which is used for meeting the damping ratio requirement of the truss girder in a full-bridge aeroelastic model wind tunnel test.

Description

Technical Field

[0001] The present invention relates to the technical field of bridge engineering, and particularly to an aeroelastic model of a truss beam and a cable-stayed bridge tower. Background Art

[0002] The wind tunnel test of the full-bridge aeroelastic model of a long-span bridge is an important means to ensure the wind resistance safety of the bridge and also an important research means to study the wind resistance performance of the bridge. The full-bridge aeroelastic model refers to a scaled model that satisfies aerodynamic similarity. According to the requirements of the similarity ratio, the main girder model must meet the similarity requirements of shape, mass, damping ratio, vertical bending stiffness, lateral bending stiffness, and torsional stiffness. The bridge tower model must meet the similarity requirements of shape, mass, axial stiffness, bending stiffness, and torsional stiffness. The similarity of shape and mass is achieved through the outer mold and counterweights, and the similarity of stiffness is achieved through the core beam.

[0003] The truss beam and the cable-stayed bridge tower are parts of the bridge. For the truss beam, since the beam core cannot be completely hidden inside the outer mold, the main girder of the truss beam is divided into multiple beam segments, each beam segment is composed of a core beam and an outer mold, and the beam segments are connected by U-shaped springs. The current beam segment design is as follows: the chord members form a hollow shell by the outer mold, the core beam is completely filled in the shell, and the web members, cross beams, and bridge decks connecting the chord members are all composed of the outer mold. This causes the outer mold that undertakes the connection function to be prone to large deformation, thus greatly increasing the damping ratio of the bridge.

[0004] For the cable-stayed bridge tower, hereinafter simply referred to as the bridge tower, the tower columns of the actual bridge tower usually adopt a hollow cross-section to reduce the material consumption and achieve the purpose of greater bending stiffness. For diamond-shaped, A-shaped, and inverted Y-shaped bridge towers, the upper tower columns are connected by two or four middle tower columns. During the model design, reasonable connection forms can be set at the junction of the middle tower columns and the upper tower columns to meet the similarity requirements of the natural vibration frequency and vibration mode of the bridge tower. In the existing designs, two connection forms are usually adopted. One is to connect the tower limbs and the upper tower column through a steel plate, and the bending stiffness similarity requirement of the bridge tower is met by adjusting the thickness of the steel plate, but the axial stiffness and torsional stiffness will be coupled with the bending stiffness and cannot meet their similarity requirements. The other way is to connect the tower limbs and the upper tower column through steel bars at the junction of the middle tower columns and the upper tower columns. The similarity requirements of two of the stiffnesses of the bridge tower can be met by adjusting the height and width of the steel bars, but the third stiffness is coupled with the former two and cannot meet its similarity requirements. In summary, the above two connection methods cannot simultaneously meet the overall axial stiffness and bending stiffness of the bridge tower in the same direction. Summary of the Invention

[0005] The purpose of the present invention is to provide an aeroelastic model of a truss beam and a cable-stayed bridge tower, which is used to meet the damping ratio requirement of the truss beam in the wind tunnel test of the full-bridge aeroelastic model.

[0006] To solve the above technical problems, the technical solutions adopted by the present invention are as follows: An aeroelastic model of a truss beam and a cable-stayed bridge tower, comprising a truss beam and a bridge tower; the truss beam is divided into a plurality of beam segments, and each beam segment includes a chord rod core beam, a vertical web rod core beam and a cross beam core beam; a cushion block is arranged at the end of the chord rod core beam, and a first outer mold is sleeved outside the chord rod core beam. There is a gap between the first outer mold and the chord rod core beam, and the first outer mold is connected to the cushion block; the chord rod core beam includes an upper first chord rod core beam, an upper second chord rod core beam, a lower first chord rod core beam and a lower second chord rod core beam; the upper first chord rod core beam and the upper second chord rod core beam are connected by a cross bar core beam, the lower first chord rod core beam and the lower second chord rod core beam are connected by another cross bar core beam, the upper first chord rod core beam and the lower first chord rod core beam are connected by a vertical web rod core beam, and the upper second chord rod core beam and the lower second chord rod core beam are connected by another vertical web rod core beam.

[0007] Further, the bridge tower includes an upper tower column core beam, and two or more layers of parallel steel bar groups are installed at the bottom of the upper tower column core beam. The steel bar group includes four steel bars, and the four steel bars extend in four directions respectively; it also includes four lower tower column core beams, and two lower tower columns are respectively connected to the ends of the four steel bars; a second outer mold is sleeved outside the upper tower column core beam and the lower tower column core beam.

[0008] Further, it also includes an inclined web rod core beam, which is arranged between two vertical web rod core beams on the same side. The bottom of the inclined web rod core beam is connected to the bottom of the previous vertical web rod core beam, and the top of the inclined web rod core beam is connected to the top of the subsequent vertical web rod core beam.

[0009] Preferably, the number of the steel bar groups is three layers.

[0010] Further, the beam segments are connected by U-shaped springs, and the U-shaped springs pass through the first outer mold and are connected to the ends of the chord rod core beams by first connecting bolts.

[0011] Further, a truss beam counterweight is installed inside the first outer mold.

[0012] Further, the second outer mold is respectively connected to different positions of the upper tower column core beam and the lower tower column core beam by second connecting bolts.

[0013] Further, it also includes a bridge tower counterweight, which is attached to the inside of the second outer mold.

[0014] Compared with the prior art, the present invention has the following advantages and beneficial effects: Truss beam: It reduces the stiffness participation and deformation of the outer formwork of the truss beam, and decreases the contact area between the core beam of the truss beam and the outer formwork of the truss beam. This method can almost entirely transfer the stiffness of the truss beam segment to the core beam of the truss beam, effectively reducing the damping ratio of the truss beam model.

[0015] Bridge tower: It changes the structural form of the core beam of the cable-stayed bridge tower. The unmet axial stiffness of the bridge tower is transformed into the equivalent axial stiffness of the bridge tower through the equivalence of the connection structure, and at the same time, the bending stiffness of the bridge tower is satisfied through the constraint effect of the connection structure on the bending deformation of the bridge tower; the connection structure approximately decouples the axial stiffness, bending stiffness, and torsional stiffness of the bridge tower by increasing the constraint length parameter, improving the design efficiency and design accuracy. Brief Description of the Drawings

[0016] Figure 1 It is a schematic elevation structure diagram of the truss beam of the present invention.

[0017] Figure 2 It is Figure 1 The sectional structure diagram of A-A in

[0018] Figure 3 It is Figure 1 The sectional structure diagram of B-B in

[0019] Figure 4 It is Figure 1 The sectional structure diagram of C-C in

[0020] Figure 5 It is a schematic elevation structure diagram of the bridge tower of the present invention.

[0021] Figure 6 It is a schematic side structure diagram of the bridge tower of the present invention.

[0022] Figure 7 It is Figure 6 The partial enlarged view of the connection structure in

[0023] Figure 8 It is Figure 7 The sectional structure diagram of D-D in

[0024] Figure 9 It is Figure 8 The sectional structure diagram of E-E in

[0025] Figure 10 It is Figure 8 The sectional structure diagram of F-F in

[0026] Figure 11 It is Figure 8 The sectional structure diagram of G-G in

[0027] The interpretations of the reference numerals in the figure are as follows: 1 - chord core beam, 2 - vertical web core beam, 3 - cross beam core beam, 4 - first outer mold, 5 - spacer, 6 - U-shaped spring, 7 - truss beam counterweight, 8 - first connecting bolt, 9 - second outer mold, 10 - upper tower column core beam, 11 - lower tower column core beam, 12 - connecting structure, 13 - steel bar group, 14 - core beam extension section, 15 - second connecting bolt, 16 - bridge tower counterweight. Specific implementation mode

[0028] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention, so as to have a further understanding of the concept of the present invention, the technical problems to be solved, the technical features constituting the technical solutions, and the technical effects brought.

[0029] An aeroelastic model of a truss beam and a cable-stayed bridge tower includes a truss beam and a bridge tower; As Figures 1-4 shown, the truss beam is divided into multiple beam segments, and the beam segments are composed of multiple truss beam core beams. The truss beam core beams include a chord core beam 1, a vertical web core beam 2, and a cross beam core beam 3; spacers 5 are provided at both ends of the truss beam core beams, and a first outer mold 4 is sleeved outside the truss beam core beams. There is a gap between the first outer mold 4 and the truss beam core beams, and the first outer mold 4 is connected to the spacers 5. The chord core beam 1 includes an upper first chord core beam, an upper second chord core beam, a lower first chord core beam, and a lower second chord core beam; the upper first chord core beam and the upper second chord core beam are connected by a cross bar core beam, the lower first chord core beam and the lower second chord core beam are connected by another cross bar core beam, the upper first chord core beam and the lower first chord core beam are connected by a vertical web core beam 2, and the upper second chord core beam and the lower second chord core beam are connected by another vertical web core beam 2.

[0030] As Figures 5-8 shown, the bridge tower includes an upper tower column core beam 10. Two or more layers of parallel steel bar groups 13 are installed at the bottom of the upper tower column core beam 10. The steel bar group 13 includes four steel bars, and the four steel bars extend in four directions respectively; it also includes four lower tower column core beams 11, and two lower tower columns are respectively connected to the ends of the four steel bars; a second outer mold 9 is sleeved outside the upper tower column core beam 10 and the lower tower column core beam 11.

[0031] In the truss beam of the present invention, a basic framework is composed of a chord core beam 1, a vertical web core beam 2 and a cross beam core beam 3. A first outer mold 4 is installed outside the truss beam core beam and is connected to the truss beam core beam through a spacer 5, and does not contact the truss beam core beam in other places. The connection method between the truss beam core beam and the first outer mold 4 adopts a local connection method, that is, the first outer mold 4 is only connected to the truss beam core beam through several spacers 5 to ensure that the first outer mold 4 can be attached to the truss beam core beam, but the first outer mold 4 does not contact the truss beam core beam in other places; the spacer 5 is a filling member, and by filling the gap between the first outer mold 4 and the truss beam core beam, the connection and force transmission between the outer mold and the truss beam core beam are achieved; the truss beam counterweight 7 is fixed on the first outer mold 4 and does not contact the truss beam core beam, and the counterweight ensures the similarity requirements of the main beam mass.

[0032] This connection relationship reduces the stiffness participation and deformation of the outer mold of the truss beam, reduces the contact area between the truss beam core beam and the outer mold of the truss beam, and can almost completely transfer the stiffness of the truss beam segment to the truss beam core beam, which can effectively reduce the damping ratio of the truss beam model.

[0033] The truss beam counterweight 7 is attached inside the outer mold of the truss beam and does not contact the truss beam core beam, and the size of the counterweight is determined by calculating the mass similarity relationship. The spacer 5 tightly wraps the chord core beam 1 and is in close contact with the outer mold of the truss beam, playing a role in force transmission.

[0034] Furthermore, the bridge tower in the present invention includes a second outer mold 9, a bridge tower counterweight 16, an upper tower column core beam 10, a lower tower column core beam 11 and a connection structure 12. The second outer mold 9 provides the shape but does not provide stiffness; the bridge tower counterweight 16 is fixed on the second outer mold 9 and does not contact the upper tower column core beam 10 and the lower tower column core beam 11, and the counterweight ensures the similarity requirements of the bridge tower mass; the connection structure 12 includes multiple layers of steel bar groups 13, which are combined with the upper tower column core beam 10 and the lower tower column core beam 11 to form an integral body; the cross-sectional dimensions and the number of layers of the multiple layers of steel bar groups 13 affect the overall axial stiffness and bending stiffness of the cable-stayed bridge tower, and the layer spacing affects the bending stiffness of the cable-stayed bridge tower; to meet the connection conditions of the multiple layers of steel bars, the lower tower column core beam 11 needs to be extended in design, and the extended length depends on the number of layers and the layer spacing of the multiple layers of steel bars, and the extended part is called the core beam extension section 14; the lower tower column core beam 11 adopts the method of equivalent bending stiffness for cross-sectional design.

[0035] Such as Figures 7-11As shown in the figure, the upper tower column core beam 10 and the lower tower column core beam 11 in the present invention are connected by more than two layers of steel bar groups 13, and more than two layers of steel bar groups 13 and the top of the lower tower column core beam 11 form a one-way multi-point elastic constraint model. The multi-point elastic constraint model can be regarded as a mechanical model in which multiple rows of springs are installed on the vertical member along the direction of the member to constrain the member. The one-way multi-point elastic constraint model is controlled by the steel bar thickness b, the steel bar width d, and the total layer spacing H. According to the mechanical properties of the model, the stiffness of the bridge tower can be approximately decoupled, so that the stiffness of the bridge tower model in three directions can be adjusted by adjusting the ratio of these three types of parameters. Through the multi-layer design of the steel bar group 13 in the present invention, the overall axial stiffness and bending stiffness of the bridge tower are controlled by different parameters respectively, improving the design efficiency and design accuracy of the four-limb bridge tower aeroelastic model. Changing the connection structure 12 between the upper tower column core beam 10 and the lower tower column core beam 11 in the bridge tower, the unsatisfied axial stiffness of the bridge tower is converted into the equivalent axial stiffness of the bridge tower through the equivalence of the connection structure 12, and then through the constraint effect of the connection structure 12 on the bending deformation of the bridge tower, the bending stiffness of the bridge tower is satisfied at the same time; the connection structure 12 realizes approximate decoupling of the axial stiffness, bending stiffness and torsional stiffness of the bridge tower by increasing the constraint length parameter, improving the design efficiency and design accuracy.

[0036] Taking the middle tower of a long-span three-tower two-main-span cable-stayed bridge as an example, a full-bridge aeroelastic model is fabricated according to the structural design of the present invention at a geometric scale ratio of 1:160, and the design parameters of each structure are calculated according to the similarity theory.

[0037] Table 1 shows the test frequencies and damping ratios of the full-bridge aeroelastic model under different vibration modes, as well as the design parameter values of each structure calculated according to the scale ratio.

[0038] Table 1 Test Frequencies and Damping Ratios 。

[0039] In Table 1, the design frequency is obtained by establishing a finite element model of the structure using finite element software, calculating the natural vibration frequency of the structure through modal analysis, and then calculating the design frequency of the model according to the similarity relationship of the aeroelastic model. The test frequencies and damping ratios are obtained by using a laser displacement meter to test the free decay curve of the structure, and calculating the vibration frequency and damping ratio of the model according to the free decay curve.

[0040] The simultaneous satisfaction of the axial stiffness, flexural stiffness, and torsional stiffness of the bridge tower is reflected in that the error between the natural vibration frequencies of the structure in different modes and the design frequencies meets the specification requirement of within 5%. The torsional stiffness of the bridge tower is reflected in the antisymmetric transverse bending mode of the main girder, i.e., Data No. 1; the axial stiffness of the bridge tower is reflected in the antisymmetric vertical bending mode of the main girder, i.e., Data No. 3; the flexural stiffness of the bridge tower is reflected in the bending mode of the bridge tower, i.e., Data No. 6 and No. 7. Through calculation, the error meets the specification requirement that the error of the low-order frequencies is within 5%. The damping ratios in each mode of the model (i.e., Data No. 1 to No. 7) are all controlled near 0.50%, which is in line with the actual situation. Data No. 2, 4, and 5 illustrate that the damping ratios in different modes can all be well controlled.

[0041] Further, it also includes inclined web member core beams, and the inclined web member core beams are arranged between two vertical web member core beams 2 on the same side. The bottom of the inclined web member core beam is connected to the bottom of the previous vertical web member core beam 2, and the top of the inclined web member core beam is connected to the top of the subsequent vertical web member core beam 2. A triangular structure is formed between the inclined web member core beam and the vertical web member core beam 2. Preferably, the number of the steel bar groups 13 is three layers.

[0042] Further, the beam segments are connected by U-shaped springs, and the U-shaped springs pass through the first outer mold 4 and are connected to the ends of the chord member core beam 1 through the first connecting bolts 8.

[0043] Further, a truss beam counterweight 7 is installed inside the first outer mold 4.

[0044] Further, the second outer mold 9 is respectively connected to different positions of the upper tower column core beam 10 and the lower tower column core beam 11 through the second connecting bolts 15.

[0045] Further, it also includes a bridge tower counterweight 16, and the bridge tower counterweight 16 is attached inside the second outer mold 9.

[0046] In the description of the present invention, the terms "connection" and "fixation" can be fixed connection, machining forming, welding, or mechanical connection. Understand the specific meanings of the above terms in the present invention according to the specific situation.

[0047] In the description of the present invention, for the terms "center", "upper", "lower", "horizontal", "inner", "outer", etc., the indicated orientation or positional relationship is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation. Therefore, it cannot be understood as a limitation to the present invention.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the various embodiments of the present invention.

Claims

1. An aeroelastic model of a truss beam and a cable-stayed bridge tower, characterized in that: It includes a truss beam and a bridge tower; The truss beam is divided into multiple beam segments, and the beam segment includes a chord core beam (1), a vertical web core beam (2) and a cross beam core beam (3); A cushion block (5) is arranged at the end of the chord core beam (1), a first outer mold (4) is sleeved outside the chord core beam (1), there is a gap between the first outer mold (4) and the chord core beam (1), and the first outer mold (4) is connected to the cushion block (5); The chord core beam (1) includes an upper first chord core beam, an upper second chord core beam, a lower first chord core beam and a lower second chord core beam; the upper first chord core beam and the upper second chord core beam are connected by a cross bar core beam, the lower first chord core beam and the lower second chord core beam are connected by another cross bar core beam, the upper first chord core beam and the lower first chord core beam are connected by a vertical web core beam (2), and the upper second chord core beam and the lower second chord core beam are connected by another vertical web core beam (2).

2. The aeroelastic model of a truss beam and a cable-stayed bridge tower according to claim 1, wherein the bridge tower includes an upper tower column core beam (10), and two or more layers of parallel steel bar groups (13) are installed at the bottom of the upper tower column core beam (10), the steel bar group (13) includes four steel bars, and the four steel bars extend in four directions respectively; it also includes four lower tower column core beams (11), and two lower tower columns are respectively connected to the ends of the four steel bars; a second outer mold (9) is sleeved outside the upper tower column core beam (10) and the lower tower column core beam (11).

3. The aeroelastic model of a truss beam and a cable-stayed bridge tower according to claim 1, wherein: It also includes an inclined web core beam, and the inclined web core beam is arranged between two vertical web core beams (2) on the same side. The bottom of the inclined web core beam is connected to the bottom of the previous vertical web core beam (2), and the top of the inclined web core beam is connected to the top of the next vertical web core beam (2).

4. The aeroelastic model of a truss beam and a cable-stayed bridge tower according to claim 3, characterized in that: The number of the steel bar groups (13) is three layers.

5. The aeroelastic model of a truss beam and a cable-stayed bridge tower according to claim 1, characterized in that: The beam segments are connected by U-shaped springs, and the U-shaped springs pass through the first outer mold (4) and are connected to the ends of the chord core beam (1) by first connecting bolts (8).

6. The aeroelastic model of a truss beam and a cable-stayed bridge tower according to claim 1, wherein: A truss beam counterweight (7) is installed inside the first outer mold (4).

7. The aeroelastic model of a truss beam and a cable-stayed bridge tower according to claim 2, characterized in that: The second outer mold (9) is respectively connected to different positions of the upper tower column core beam (10) and the lower tower column core beam (11) by second connecting bolts (15).

8. The aerodynamic elastic model of a truss beam and a cable-stayed bridge tower according to claim 1, characterized in that: It also includes a bridge tower counterweight (16), and the bridge tower counterweight (16) is attached to the inside of the second outer mold (9).

Images