KR101468302B1

KR101468302B1 - Girder Anchorage Method by Placing Cable througth Concrete Curved Box Section

Info

Publication number: KR101468302B1
Application number: KR1020130043284A
Authority: KR
Inventors: 연정흠
Original assignee: 인하대학교 산학협력단
Priority date: 2013-04-19
Filing date: 2013-04-19
Publication date: 2014-12-02
Also published as: KR20130047720A

Abstract

This method is about a cable girder fixing method in a concrete box girder supported by a cable, such as a cable-stayed bridge or an extrados dojo bridge. In the conventional girder mounting block, a large concentrated sectional force is generated due to the tension of the cable, which may damage the fixing block and discontinuity of the moment distribution occurs. In this method, the cable is installed in a curved box section and inserted into the duct so that the cable is fixed across the curved box section. Within the section, the tension of the cable is reduced by the friction, but the cable tension generates the sectional force distributed in the insertion section of the cable. The cross-sectional force due to the cable tension can be controlled by the height ratio to the width of the cross-section and the insertion angle of the cable, which makes it possible to more effectively apply the cable tension to the moment distribution due to the external load.

Description

{Girder Anchorage Method by Placing Cable Througth Concrete Curved Box Section} A method of fixing a cable girder by arranging a cross-

The present invention relates to the fixing of a girder portion of a cable in a concrete bridge supported by a cable, such as a cable-stayed bridge or an extradosed bridge, The present invention relates to a method of fixing a cable to a girder by installing a cable so as to pass through a web and a lower flange of a section of a concrete box having a curved shape such as a half ellipse and a part of an ellipse.

A cable-stayed bridge is a bridge supporting a girder by installing a cable at an angle to a main tower on a pier. The extrados bridge is a bridge that increases the tension and eccentricity of a cable to increase moment and axial force of the girder. These cable support bridges enable the design of the economic and cosmetic aesthetics of the Changdaegyo with spans over 100 m. The cable of the cable supporting bridge is generally fixed to the girder fixing block 6 provided on the side of the upper flange of the girder as shown in Fig. 1, and the fatigue and vibration reduction device (Patent Document 1) is used, or the upper flange (Patent Document 2) or an ultra high-performance bottom plate (Patent Document 3) and a crank-type edge girder (Patent Document 5). In some cases, the fixing block is installed in the inside of the lower flange (patent document 4) or outside (patent document 7). In the case of a single main tower, a fixing block is installed at the center of the upper flange (Patent Document 6).

However, in the fixing block of the conventional cable girder fixing method using the fixing block, as shown in Fig. 2, a large concentrated sectional force 17 is generated in the vertical direction and the throttling direction due to the tension of the cable. In order to support the concentrated sectional force, the fixing block must be designed very precisely, and the bending moment due to the cable tension 4 at the position of the fixing block (Fig. 2) and the sudden change in axial load result in discontinuity of the load . Particularly when a girder fixing block is installed on the outer side of a relatively wide upper flange or slab, a large tensile stress can be generated laterally in the lower flange of the center portion of the girder.

[Document 1] Domestic Application 10-2011-0050274 May 25, 2011 [Document 2] Domestic Application 10-2010-0043348 2010.05.10 [Document 3] Domestic Application 10-2009-0109012 2009.11.12 [Document 4] Domestic Application 10-2009-0094509 Oct. 10, 2009 [Literature 5] Domestic Application 10-2008-0111566 2008.11.11 [Document 6] Domestic Application 10-2007-0128320 2007.12.11 [Literature 7] Domestic Application 10-2007-0092214 2007.09.11

This method is a method of arranging cables across a section of a concrete curved box of a cable supporting bridge. The concentrated sectional force 17 (FIG. 2) generated in a conventional cable girder fixing block 6 is divided into sectional forces To minimize the tensile force 21 generated in the transverse direction 8 on the lower flange of Fig. 8 to enable more efficient utilization of the cable tensions of the cable support bridges The purpose of the cable is to settle the girder.

The concrete box girder transverse section of this method has a curved shape such as a parabola or a semi-ellipse and a partial ellipse in the form of a web and a bottom flange, and is formed of a sheet such that the cable can be arranged in the abdomen, a duct is formed by inserting a sheet. The direction conversion block 2 is installed so that the cable can be smoothly changed in angle in the cable insertion portion instead of the conventional fixing block 6. [ The longitudinal force 18 of the cable axial direction 10 introduced into the end of the concrete box by the tension 16 of the cable causes the cable plane height 12 against the upper flange width 14 of Figures 5 and 6 And the height of the cable plane with respect to the semi-elliptical center height 15 of Fig. 7 in the case of a partial ellipse, and can be controlled in the throttling direction 7 and the vertical direction 7 of Fig. 9) It is a feature of this method that the unit length force (19, 20) can be controlled by the unit length of the cable axial direction force (18) and the cable insertion angle.

A direction changing block 2 is provided in place of the fixing block 6 on the cable inserting portion of the curved box section 1 of the curved box section 1 in FIG. The present method can be expected to have the following effects in comparison with a method of fixing a cable to a fixing block of a conventional concrete box girder.

1. It is possible to control the magnitude of the concentrated sectional force generated in the cable insertion portion by adjusting the insertion angle of the cable in the cable insertion portion or the direction conversion block 2.

The equilibrium condition in the direction conversion block 2 with respect to the cable angle change just before and after the insertion of the cable is as shown in Fig. 2, and in the conventional fixing block, the cable tension immediately after the direction conversion block A relatively large concentrated sectional force 17 is generated in the fixing block 6. [ When the cable is inserted in the state that the angle of the cable is not changed, no sectional force in the throttling direction 7 and the vertical direction 9 is generated, and even when the cable angle of the end insertion portion is changed by using the direction conversion block 2, And the vertical directional sectional force can be significantly reduced. The change in cable tension (4 and 16) at the cable entry is calculated by the change in the coefficient of friction of the direction conversion block and the angle of the cable.

2. The sectional force of the curved section due to the cable tension is distributed continuously in the insertion section of the cable as shown in Fig. 3, and the lateral tensile force 21 of the lower flange is minimized.

The sectional force per unit length acting on the cut surface 1 or the cable plane of the curved box girder of Fig. 1 in the cable axial direction 10 and transverse direction 8 is distributed over the entire section as shown in Fig. The distribution of the unit length leg force 21 in the transverse direction 8 with respect to the height direction 10 exhibits a relatively constant compression in the abdomen and a small tensile force is generated in the center of the lower flange. On the other hand, the lateral (8) distribution of the cross-sectional force 18 per unit length in the cable direction (10) is maximum at the center of the lower flange and decreases toward the insert of the upper flange. The distribution of the unit length section force introduced by the cable of FIG. 3 is derived from the equilibrium condition of FIG. 4, and FIG. 4 (a) And the tensor equilibrium condition for the unit length axial force and the shear force is the same as in FIG. 4 (b), and the axial unit length sectional force formula of FIG. 4 (c) is derived. In FIG. 4, the tangent value is a first derivative value of the curved function, and the curvature radius is calculated from the first and second derivative values of the curved function.

3. Cable Axial Unit Length The magnitude and distribution of the section force 18 can be controlled by the ratio of the height 12 to the width 11 of the cable plane of Figs. 5-7.

5 is a distribution of the unit length longitudinal force 18 in the cable axial direction 10 with respect to the parabolic cross section when the upper width 11 and the cable plane height 12 are given. If the inclination angle of the cable is large and the girder height is small (small height-width ratio), the cable tends to be distributed evenly over the entire height. If the cable inclination angle is small and the girder height is large And a significantly smaller unit length section force 18 is introduced in the upper flange. [Figure 5] and [Figure 6] are section force (18) per unit length in the cable axial direction (10) for half ellipse and partial elliptical section, respectively. In case of semi-elliptical cross section, since the cable insertion angle of the upper flange is 90 degrees, the sectional force (18) per unit length in the cable axis direction (10) does not occur in the upper flange and even when a partial ellipse smaller than half ellipse is used ] Is smaller than the value for the parabola. However, the unit length force (18) of the lower flange is similar to the parabola for semi-ellipses and larger for the same height-width ratio for partial ellipses.

4. The longitudinal and transverse unit longitudinal force 19,20 due to the tension of the cable is distributed continuously in the cable insertion section and the distribution shape of these sectional forces is determined by the cable longitudinal axis unit force 18 and the cable insertion angle Lt; / RTI >

8 and Fig. 3, the unit direction length unit force 19, 20 in the throttling direction 7 and the vertical reverberation 9, which are caused by the tension of the cable passing through the curved box cross section, And the size thereof is controlled according to the sectional force 19 and the insertion angle of the cable. The vertical direction unit length section force 20 is maximum in the lower flange and continuously distributed in the section where the cable is inserted at the minimum point at the cable insertion point 2 and the threshing direction unit length section force 19 is similar to the distribution of the vertical direction sectional force It shows a sharp decrease than one.

[Figure 1] Comparison of the cross-section of the cable box (1) and the cross section of the box with the existing girder fixing block (5)
[Figure 2] In the direction conversion block 2 or the girder fixing block 6,
[Fig. 3] Unit-length sectional force distribution introduced by cable of cable plane
[Figure 4] Equilibrium condition of unit length sectional force at any position of cable plane
[Fig. 5] Cable direction (10) introduced into the parabolic cross section Unit length Cross sectional force (18) Distribution
6] Distribution of cable direction (10) unit length section force (18) introduced into a semi-elliptical section
[Fig. 7] Distribution of cable unit direction (10) unit length section force (18) introduced into a partial oval cross section
8 is a diagram showing the relationship between the crossing axis 7 and vertical (9) unit longitudinal force 19, 20

The cable-supported concrete curved box girder according to this method is carried out as follows.

1. Cable-supported concrete box The height of the section is determined by the conventional design method for the width of the bridge, the design load and the cable tension in the design stage of the box girder, and the abdomen and the bottom flange of the concrete box section are divided into parabolic or semi- And a partial town.

2. Resistance of the expected moment and moment distribution to the cable support bridges in the final state Determine the insertion angle of the cables in the cross-section so that the required cross-sectional forces of the upper and lower flanges can be introduced by cable tension. Calculate the unit length cross-sectional force in the section by cable tension, and adjust the height of the section, the insertion angle of the cable and the cable tension if necessary. If the thickness of the abdomen and bottom flange of the cross-section of the curved box is not sufficient to support the unit length cross-sectional force, an additional block attached to the inside or outside of the cross-section is installed.

3. In the production of the concrete curve type box girder, a sheet is inserted into the inside of the abdomen and the bottom flange or the outer block attached to the duct to form a duct which is inclined in the throttle direction and curved in the transverse direction by the cable insertion angle, A direction conversion block is installed so that the angle change of the cable is smooth.

4. Once the curved box girder is installed, insert the cable into the duct and introduce the necessary cable tension in the cable pylon.

1. Curved box girder across the cable.
2. Curve-shaped box section The directional block of cable insertion (deviation saddle)
3. Main cable tower
4. Cable
5. Conventional PS concrete box girder (PS concrete box girder)
6. Cable girder anchorage block
7. The girder axis
8. Cross-axis
9. Vertical axis
10. Cable axis
11. Width of cable plane
12. The height of the cable plane
13. Height of girder
14. The center of the ellipse (width of ellipse)
15. The height of the half ellipse
16. Direction conversion block (2) Cable tension after passing
17. Cross-sectional force of the cable insertion part (2 or 6)
18. Cable direction (10) Unit length Sectional force
19. Throttling direction (7) Unit length Cross-sectional force
20. Vertical direction (9) Unit length Sectional force
21. Lateral direction (8) Unit length Sectional force

Claims

Cable supporting concrete box girder Bridges and lower flanges of bridges are fabricated in at least one curved form of parabola, half ellipse or partial ellipse,
A duct is installed in the inside of the abdomen and the lower flange or inside the outer block attached to the abdomen and the lower flange so as to be inclined in the transverse direction 8 of the girder section in the curved shape in the throttling direction 7,
A method in which a cable is fixed to a girder by inserting a cable into the duct and arranging it across the cross section of the concrete box girder.