JP2709279B2 - Saddle structure for cable-stayed cable on main tower side of cable-stayed bridge - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cable stayed bridge and a saddle structure for supporting a cable stayed cable on a main tower side of an extra-dose bridge.

[0002]

2. Description of the Related Art FIG. 5 shows an example of a cable-stayed bridge in a schematic view from the side. The outline of the construction work is as follows. Pier 51
At the time of concrete casting, a projecting portion 52 is formed symmetrically from the main leg 53, and a work table (not shown) is fixed with the projecting portion 52 as a power point to assemble a frame body, and a predetermined main beam 53 is formed. Perform concrete casting over the length, simultaneously cast the main tower 54 on the pier 51, forming a saddle 55,
The cast main beams 53 are supported at both ends of the cable 56 supported by the saddle 55, and when the construction of this portion is completed, the main beam 53 is used as a power point, and the next main beam is symmetrical to the main tower 54. The work piece is advanced to a portion to be 57, a frame is assembled, concrete is cast, and main girders are provided at both ends of a cable 59 supported by a saddle 58 formed above the saddle structure 55 of the main tower 54. In this method, the main steps are continuously formed by repeating the above steps in an overhanging manner. The pier, main tower, and main girder are PC
Necessary reinforcement is provided by steel materials such as steel materials.

[0003] The fixing structure of the cable stayed cable used on the main tower side is roughly classified into a structure using a saddle and a structure where the left and right cable stayed cables are individually fixed to the concrete skeleton above the main tower. The saddle is as described with reference to FIG.
The cables shown on the left and right are separately cable-stayed on the main tower side.
In some cases, the fixing section 60 is configured such that the end of the main tower 54 intersects with the end of the main tower 54.

The saddle shown in FIG. 5 does not fix the cable ends to the main tower as compared with the individual cable fixed in the main tower shown in FIG. In addition, since only cables are passed through, a fixing device for each cable is not required, so that the main tower portion can be realized very economically. If uneven tension occurs at the time of construction or after the completion of the structure, there is a possibility that the cable will slip. As a slip preventing measure against the uneven tension, a method using a saddle structure and friction of a cable, a method of providing a shear cotter 61 for fixing a cable 56 at the center of the saddle structure as shown in FIG. At the body outlet, as shown in FIG. 8, a bearing plate 63 is arranged on a concrete frame 62, an anchor block 64 is arranged, and each PC steel strand 65 of the cable is passed through a hole formed in the anchor block 64, and a fixing wedge is formed. According to 66, a method of fixing the cable is adopted. In each of these methods, a hole is formed in the concrete frame of the main tower so that the cable can pass through, so that the cable can be replaced in the event of a future emergency. .

[0005]

The problem to be solved by the present invention relates to the cable support on the main tower side by the saddle. However, the above-mentioned method relying on friction between the cable and the saddle mainly focuses on the main tower. When the difference between the right and left cable tensions increases, the cable slides, the structure becomes unstable, and there is a problem in safety. In order to avoid this, a method in which a non-slip shear cotter is provided at the center of the saddle is such that when the tension difference is large, a local bending moment Mo = | T ₁ − as shown in FIG. T ₂ | l (where T ₁ ,
(T ₂ , tensile strength, l: length of moment acting) may adversely affect the long-term fatigue characteristics of the included PC stranded wire, for example, when applied to the cable. Further, in order to transmit the non-average tension to the main tower concrete body at the outlet portion of the saddle portion, the method of providing a direct fixing wedge in FIG. 8 is to provide a wedge flaw at a position where the bending stress of the cable due to wind load is considered to be most concentrated. As a result, there was a serious problem in the long-term bending fatigue characteristics of the cable. Further, in the saddle structure shown in FIG. 7, due to a manufacturing error at the time of bending the saddle outer pipe (steel pipe) and an error at the time of mounting the saddle outer pipe on the concrete frame, the cable is not connected at the outlet of the saddle outer pipe as shown in FIG. In the saddle structure according to the above-described method, a local small deflection R ₁ is generated with respect to the curvature R ₀ , the cable 17 is pressed at the outlet end of the outer tube, and a repeated bending stress is applied from the free length portion 67. Fretting corrosi on the cable
There is a concern that the structure according to the method of on) or the method of (1) promotes angle fixing fatigue at the head of the wedge.

[0006]

SUMMARY OF THE INVENTION The present invention proposes a saddle structure for a cable stayed cable, which eliminates the above-mentioned problems and allows a conventional cable replacement. This is illustrated by the embodiment shown and the associated figures. In order to save labor at the construction site, the saddle structure is usually assembled in a factory based on the design and transported to the site. In FIG. 1, the saddle structure comprises a saddle outer tube 1 and a saddle inner tube 2 inserted therein. Both ends of the saddle inner tube 2 are exposed to substantially the same length as the both ends of the outer tube 1. 2
A thread groove 3 is formed at the end of the ring nut 4.
As shown in FIG. 4, a single row or a plurality of rows of steel projections 18 are formed on the upper side (ceiling side) of the inner tube 2 of the saddle, as shown in FIG. I have. In order to provide a through hole for a cable in the main tower, the saddle outer tube 1 is made of a flexible tube such as PE or a thin corrugated steel tube, and is provided inside a bent steel saddle inner tube 2 installed therein. To be in contact with the entire curved shape inside the saddle bending radius. In order to achieve this, at the time of the assembling, a spacer 5 made of PE which can be removed in the future is arranged in the upper gap between the two pipes, and they are firmly fixed to each other. It is supported and fixed by the fixing member 6. The upper gap is filled with urethane foam 19. The temporary fixing members 6 at both ends hold the outer peripheral surface of the flanged tube 7 fitted into the end of the saddle outer tube 1 and are fixed to the outer peripheral surface by, for example, welding 10. The lower part of the temporary fixing member 6 is fixed to the base 11. In addition, pipe 7 with flange
The support plate 8 is fixed to the upper position of the outer periphery of the support plate, two grout hoses 9 are pulled in at the position of one support plate 8, and one grout hose 9 is opened at the position of the saddle inner tube 2 immediately below. The other grout hose 9 is connected to a hole formed at the center of the saddle inner tube at the position of the inner tube 2, and the other grout hose 9 is connected to the other support plate 8 at the position of the other support plate 8. Is drawn in,
Immediately below it, it is connected to a hole made in the inner tube 2.

FIG. 2 is an enlarged view of the saddle outlet structure of the saddle structure shown in FIG. The screw groove 3 is formed at the end of the inner tube 2 of the saddle as described above. The inner diameter of the inside of the inner region indicated by S in FIG. A socket region is formed by performing socket processing that expands conically, and as shown, the end of the saddle inner tube 2 having this socket region is integrally formed with the saddle inner tube 2 by welding or the like as a saddle inner tube. ing. As already described, the saddle outer tube 1 is located outside the saddle inner tube 2, and is fitted with a flanged tube 7 at the end of the saddle outer tube 1, so that the saddle portion is cast into concrete. At this time, the surface of the flanged pipe 7 is cast so as to be substantially flush with the surface of the main tower concrete frame 12. As shown in FIG. 3, the porous spacer 13 is fitted into the outlet portion of the saddle inner tube 2 having an inner diameter substantially equal to the outer diameter of the porous spacer (for example, made of PE) 13 having a flange. To the end face. Further, a mortar fastening plate 14 having the same number of holes at the same position as that of the porous spacer 13, for example, a structure made of PE is fitted to the end surface of the outlet portion of the inner tube 2 of the saddle 2, and the two are tightened with screws 15. A structure for fitting into the screw groove 3 is adopted.

FIG. 10 shows a state before the PC steel strand is inserted into the saddle of the main tower. The saddle structure C shown in FIG. The flanged pipe 2 (FIG. 6) is embedded and fixed in a state where the end face of the pipe 2 is exposed from the surface of the cast concrete body. In FIG. 10, the main cable 70 extends from the anchoring portion of the main girder symmetrically laid in the main tower T in the direction of the exits at both ends of the saddle structure C of the main tower T, penetrates the concrete frame, and connects with the back surface. The main girder cables 70 are tensioned between the fixing portions, and the main ropes 70 are each maintained with a suspension ring 71 by a spacing rope 72, and the suspension ring 71 holds a PE protection tube 73. The working window is formed by leaving the end of the protective tube 73 at a predetermined interval W, and is opposed to the outlet of the saddle inner tube of the saddle structure. Referring to FIGS. 2, 4 and 10, the PC steel strands 17 (strands) constituting the cable of the cable-stayed bridge are passed through the protective tube 72 from the fixing part of the main girder one by one, and the working window After exiting W, with the ring nut 4 of the saddle structure, the grout retaining plate 14 and the porous spacer 13 removed, the strand 17 is first passed through the grout retaining plate 14, then through the porous spacer 13, and the saddle inner tube is removed. 2 and the work window W on the opposite side of the main tower T is reached, and then the porous spacer 13 and the grout retaining plate 14 are sequentially passed in this order, and the PC strand is pulled obliquely downward. Pass through the fixing part on the main girder side located at the symmetrical position. By repeatedly performing such operations, after inserting all the strands of PC steel, the porous spacer and the mortar fastening plate are moved and set to the predetermined positions described above.

Next, the cable is tightened simultaneously from the fixing portions on both sides on the main girder side. In this case, it is desirable to synchronize the jack operation and tension the cable so as not to move at the fixed point in the center of the saddle.

After the tension, the resin is partially injected into the spout 16 of the mortar retaining plate 14 in FIG. 2 and after the grout is hardened,
Non-breathing type high-strength non-shrink grout is injected into the saddle inner tube 2. This grout is injected from the socket region by the grout hose 9 in FIG. 1, and the overflow is discharged from the center portion, which is the top, by the grout hose 9, so that there is no mortar void in the saddle inner tube. Reference numeral 19 denotes a cable cover which is thereafter covered over the entire cable-stayed cable and filled with grout.

[0011]

[Operation and Effect] Both ends of the inner tube of the saddle are socketed into a conical shape whose diameter increases inward as shown in Fig. 2. After the mortar is injected, a part of the stress of the non-average tension is shared by this socket effect. I do. After the tension of the PC steel strand, the mutual contact between the PC steel strands is concentrated at the center of the saddle, which is the fixed point of the cable as shown in FIG. 4 (see FIG. 4). Of course, mutual contact is made at a point where the axial variation factor is minimized, and the fatigue resistance performance of the PC steel wire tension system is significantly improved. Porous spacers are placed at both ends exits, which are the weak points of the saddle, to make each PC steel strand independent, and the adjacent PC steel strands come into contact to generate fretting corrosion, fatigue performance,
It is possible to avoid a drop. The transmission of force from the solidified grout to the inner tube of the saddle is due to the combination of the steel projection protruding inside the saddle and the conical socket areas provided at both ends, and the force applied to the cable is extremely concentrated at a certain portion. These forces are transmitted to the main tower concrete frame by tightening the ring nuts fitted on both sides of the saddle inner tube to the main tower concrete frame. Since the porous spacers (made of PE) provided at both ends of the saddle can maintain a predetermined distance interval between the strands of each PC steel inside the inner tube of the saddle, the grout to be injected can be maintained at each P.
Filled evenly between C steel strands.

The saddle structure of the cable stayed bridge of the present invention can be applied to an extra toe bridge in which the saddle position (height) H of the main tower is smaller than the span S of the bridge girder. The structure of the present invention can also be applied to a bridge pier and a structure in which a main tower constructed on the pier has a steel structure.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of the structure of the present invention.

FIG. 2 is an enlarged view showing an outlet of the saddle structure shown in FIG. 1;

FIG. 3 shows an example of a porous spacer used at the saddle outlet of FIG. 2;

FIG. 4 is a cross-sectional view showing a central portion of the structure when a cable is inserted into the structure of the present invention and tightened.

FIG. 5 shows an example of a cable-stayed bridge in a schematic view from the side.

FIG. 6 shows an example of a cross-fixing structure on the main tower side of the cable stayed cable.

FIG. 7 shows an example of a fixing structure by a shear cotter of a cable in a saddle on a main tower side of a cable-stayed bridge.

FIG. 8 shows an example of a cable anchoring structure using wedges at a saddle end of a main stay of a cable-stayed bridge.

FIG. 9 is an explanatory diagram of a local deflection of a cable that occurs after the cable is tensioned when a conventional saddle structure is manufactured and an installation error occurs.

FIG. 10 is an explanatory view showing a state before a PC steel strand is inserted into a saddle of a main tower.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Saddle outer pipe 2 Saddle inner pipe 3 Screw groove 4 Ring nut 5 Spacer 6 Temporary fixing material 7 Flanged pipe 8
Support plate 9 Grout hose 10 Welding 11 Base 12 Concrete frame 13 Perforated spacer 14 Clamping plate 15 Screw 16 Lobster 17 Steel strand 18 Projection

Claims (7)

(57) [Claims] 1. A saddle outer tube having a flexible inner saddle tube, a porous spacer fitted into both end outlet portions of the inner tube from the outlet portion, and formed at the outer periphery of both end outlet portions of the saddle inner tube. A saddle structure for a cable-stayed cable on a main tower side of a cable-stayed bridge, wherein a ring nut can be attached to a thread groove. 2. The main tower of a cable-stayed bridge according to claim 1, wherein the inner tube of the saddle is made of steel, and an inner tube having a single row or a plurality of rows of steel projections on an inner upper surface side is used. Saddle structure for side-cable cable. 3. An inner tube made of steel as an inner tube of a saddle and having a conical region extending inward on the inner surface of the inner tube from a position inside the porous spacer fitted into the outlet of both ends of the inner tube. 3. A saddle structure for a cable-stayed cable on a main tower side of a cable-stayed bridge according to claim 1 or 2, wherein 4. A grind injection hole is provided in the inner tube inside the porous spacer fitted into both ends of the saddle inner tube, and an inner tube provided with a grout overflow hole at the center top of the inner tube is used. A saddle structure for a cable-stayed cable on a main tower side of a cable-stayed bridge according to claim 2 or 3. 5. The saddle outer tube is made of a flexible PE or a thin corrugated steel tube, and a spacer is arranged in a gap between the upper surface of the curved saddle inner tube and the outer tube to form a mutual pressure contact surface in the inner tube shape. 3. The method according to claim 2,
Saddle structure for cable-stayed cable on main tower side of cable-stayed bridge according to 3 or 4. 6. A saddle outer tube in which a flanged tube is fitted to the outer peripheral surfaces of both ends.
A saddle structure for a cable-stayed cable on the main tower side of a cable-stayed bridge according to 2, 3, 4, or 5. 7. A mortar retaining plate which has been subjected to the same number of porosity processing as the spacers is held for the porous spacers fitted from both outlets of the inner tube.
A saddle structure for a cable-stayed cable on the main tower side of a cable-stayed bridge according to 3, 4, 5, or 6.