JP4728262B2 - Saddle structure - Google Patents

Description

  The present invention relates to a saddle structure provided in a main tower such as a cable-stayed bridge or an extradosed bridge. In particular, the present invention relates to a saddle structure capable of reducing the thickness of an inner tube among members constituting the saddle structure.

  Cable-stayed bridges and extradosed bridges are known as bridges provided on arterial roads and railway tracks. These cable-stayed bridges and extradosed bridges are configured to support the main girder by a plurality of cables extending obliquely from a main tower arranged perpendicular to the main girder.

  It has been proposed to use a saddle structure in the main tower of the cable-stayed bridge or the extradosed bridge as described above. The saddle structure is configured such that an intermediate portion of a cable whose both ends are fixed to a main girder is held by a main tower portion. Examples of such a saddle structure include those described in Patent Document 1 and Patent Document 2.

  FIG. 12 is a schematic configuration diagram of a saddle structure having a configuration similar to that of the saddle structure described in Patent Document 1. The saddle structure 100 is mainly composed of an outer pipe 120 embedded in a main tower 200 made of concrete and an inner pipe 110 disposed inside the outer pipe 120. The position of the inner tube 110 in the outer tube 120 is fixed by the inner tube spacer 150. A plurality of tensioned strands 130 are inserted into the inner tube 110, and the strands 130 are integrated with the inner tube 110 by a grout 140. Here, the saddle structure is designed by considering a plurality of strands as one set and a single cable. Further, a ring nut 180 is screwed to the outer peripheral surface at both ends of the inner tube 110, and the ring nut 180 is held against a pressure bearing plate 181 fixed to the main tower 200. By having such a configuration, the tension difference introduced into the cable due to the vibration of the main girder is transferred from the cable to the main tower 200 via the grout 140, the inner tube 110, the ring nut 180, and the bearing plate 181. Communicated.

  Of the constituent members of the saddle structure 100 described above, the inner tube 110 includes a curved pipe portion 111 having a gentle curvature and straight pipe portions 112 formed at both ends of the curved pipe portion 111 (FIG. 12B )). The bent pipe section 111 deflects a cable (a set of a plurality of strands) extending from one cable fixing point to the other cable fixing point at the main tower 200 portion. On the other hand, the straight pipe portion 112 is formed so as to extend straight from the end portion of the curved pipe portion 111, and guides the cable from the end portion of the curved pipe portion 111 to the cable fixing point of the main girder.

  Further, in the inner pipe straight pipe portion 112 of the saddle structure 100, the strands 130 are held by the cable spacer 190 at a predetermined interval. It becomes easy to form the water stop structure 195 by providing a space between the strands 130. The water stop structure 195 prevents the grout 140 from leaking from the inner pipe 110.

  On the other hand, FIG. 13 is a schematic configuration diagram of a saddle structure having the same configuration as the saddle structure described in Patent Document 2. The saddle structure 101 uses a so-called multi-cable 230 in which a plurality of strands 231 are accommodated in a covering material 235 and collected into one cable, and a cable spacer is not required. Therefore, the use of the multi-cable 230 changes the structure of the exit portion from the saddle structure of FIG. Here, since the basic structure of the saddle structure other than the outlet portion is the same as that of FIG. 12, the same members as those described with reference to FIG. Omitted.

  FIG. 13B is an enlarged view of the exit portion of the saddle structure using a multi-cable. In the saddle structure 101, a slide pipe 210 is screwed to the end of the straight pipe portion 112, and a rubber boot 220 is attached to the end of the slide pipe 210. The rubber boot 220 seals the gap between the end portion of the slide pipe 210 and the multi-cable 230, and prevents the grout 140 from leaking out from the inner tube 110.

  Here, the straight pipe part of the inner pipe in the saddle structure of Patent Documents 1 and 2 described above is formed at both ends of the bent pipe part so that the cable extending from the inner pipe can be guided to the cable fixing point of the main girder. As already described, there is a case where the axis of the straight pipe portion is not arranged so as to penetrate the cable fixing point of the main girder. Since the cable extending obliquely from the main tower to the cable fixing point hangs down by its own weight, it does not extend straight from the end of the straight pipe portion to the cable fixing point, but draws a suspension line. For this reason, if the straight pipe part is arranged so that the axis of the straight pipe part penetrates the cable fixing point, the cable may be bent at the end of the straight pipe part or the cable may be It is conceivable that the load level applied to the straight pipe portion by pressing downward increases. In order to solve such a problem, in the conventional saddle structure, in consideration of the amount of cable sag (cable sag), the cable axis of the portion protruding from the straight pipe portion at the outlet portion of the straight pipe portion The curvature of the curved pipe portion is adjusted so that the axis of the inner pipe straight pipe portion coincides.

JP 2003-55911 A Japanese Patent Laid-Open No. 11-280021

  However, even if the saddle structure is designed in consideration of the cable sag as described above, the cable at the outlet portion of the straight pipe portion of the inner pipe is caused by processing errors in each member of the saddle structure and construction errors during construction. There is a risk that the cable may be bent at an angle due to a shift of the axis of the inner tube and the axis of the inner pipe straight pipe portion.

  Even if the axis of the cable matches the axis of the inner pipe straight pipe part, for example, when the train or vehicle passes over the bridge, the cable vibrates and the cable presses the straight pipe part. Bending stress may act on the straight pipe part. In the first place, when the cable is tensioned, a force (normal component force) that presses the straight pipe portion perpendicular to the axial direction of the straight pipe portion acts on the straight pipe portion (Fig. 12 ( B), see the direction of the arrow in 13 (B)), even when the cable is not vibrating, a strong bending stress is acting on the straight pipe. As shown in FIG. 12 (C) and FIG. Therefore, it is necessary to increase the thickness of the inner pipe including the straight pipe portion so that it can withstand the bending stress caused by the normal component force or the like.

  Furthermore, in recent years, there has been a demand for a bridge that can withstand this tension even when tension equivalent to Level 2 ground motion acts on the cable, based on the lessons learned from the Great Hanshin-Awaji Earthquake, and the inner pipe must be made thicker. It was. Thus, when the thickness of the inner pipe is increased, the unit price of the member is increased and the construction cost is increased. The definition of Level 2 ground motion is based on the activity report of the Level 2 Earthquake Motion Research Subcommittee of the Civil Engineering Society of Japan in March 2000.

  On the other hand, it has been proposed to form the end portion of the straight pipe portion of the inner tube in a trumpet shape to prevent the cable from being bent at the end portion and to reduce the bending stress applied to the end portion. However, since the trumpet-shaped end portion of the inner pipe straight pipe portion is difficult to form by cutting, it is generally formed by plastic working. However, such plastic working is complicated and expensive. . Moreover, even if the end portion of the straight pipe portion is formed into a trumpet shape, the normal component force still acts on the straight pipe portion, so that the thickness of the straight pipe portion has to be increased after all.

  In addition, when the curvature of the cable changes between the intermediate portion of the inner tube curved tube portion and the inner tube straight tube portion, the position of the end portion of the cable spacer 190 (especially in FIG. (Position (a) in (B)), in the saddle structure of Patent Document 2, it acts on the cable due to the corner bending of the strand at the end position of the covering material 235 (particularly, position b in FIG. 13 (B)). There was a possibility that the applied stress would increase.

  Therefore, a main object of the present invention is to provide a saddle structure having a structure in which excessive bending stress does not act on the straight pipe portion of the inner pipe at the outlet portion of the saddle structure.

  The inventors of the present invention focused on how the normal component force acts and studied various configurations for reducing the normal component force. As a result, the normal component force was adjusted by adjusting the angle of the straight pipe portion of the inner tube. The knowledge that can be greatly reduced. The present invention is defined based on this finding.

  The saddle structure of the present invention includes an inner pipe through which a plurality of independent strands fixed at both ends to the main girder of the bridge in a tensioned state are inserted, and an outer circumference of the inner pipe embedded in the main tower portion of the bridge. An outer tube for covering and a cable spacer for separating a plurality of independent strands from each other at an end of the inner tube. The inner tube of the saddle structure includes a bent tube portion and a straight tube portion that is formed at both ends of the bent tube portion and protrudes from the end portion of the outer tube. And when considering the plurality of strands as one set as a single cable, the angle formed between the horizontal line and the axis of the straight pipe portion is considered in consideration of the sag of the cable extending from the horizontal line and the straight pipe portion to the main girder. It is characterized in that it is larger than the angle formed by the axis of the virtual straight pipe portion at that time.

  With the above configuration, the normal component force can be greatly reduced in the saddle structure in which a plurality of independent strands are arranged inside the inner tube. In addition, at the end of the cable spacer, the bending angle of the strand located particularly at the upper part of the inner tube can be made gentle.

  In the saddle structure of the present invention using a plurality of independent strands, the angle of the straight pipe part with respect to the horizontal line is changed by changing the curvature of the inner pipe curved pipe part. However, when comparing the conventional saddle structure (see FIG. 12B) with the saddle structure of the present invention (FIG. 2 showing the saddle structure of Example 2 described later), the angle of the straight pipe portion is Except for the above, there is no change in appearance. However, in the inner tube 10 shown in FIG. 2, the bending angle of the strand 31 at the end of the cable spacer 90 on the bent tube portion 11 side (corresponding to the position a in FIG. 12B) can be reduced. . Further, since the bending angle of the strand 31 at this portion can be reduced, the normal component force acting on the inner pipe straight pipe portion 12 can be reduced. Therefore, the thickness of the straight pipe portion 12 can be made thinner than that of the conventional saddle structure.

  In this saddle structure, when the bending radius of the bent pipe part is 2.5 m or more, the angle difference between the straight pipe part axis and the straight pipe part axis when considering cable sag is 3 ° or less. Is preferred. If the angle difference exceeds 3 °, the cable may be bent in the opposite direction to the conventional case. This angle difference may be appropriately selected within a range not exceeding 3 ° depending on the mechanical characteristics and dimensions of the member. For example, when using a 12S cable manufactured by Sumitomo Electric Steel Wire Co., Ltd., if the minimum bending radius is 2.5 m or more, the angle difference is 0.5 °. When using a 27S cable, if the minimum bending radius is 3.5 m or more, the angle difference is It should be 1.0 °. Here, the 12S cable is considered to be a single cable with a set of 12 strands arranged inside the inner tube. Similarly, the 27S cable is also considered as a single cable with a set of 27 strands.

  Further, another saddle structure of the present invention includes an inner pipe through which a multi-cable that is fixed at both ends to the main girder of the bridge in a tensioned state, and an outer circumference of the inner pipe embedded in the main tower portion of the bridge. And an outer tube covering. The inner tube of the saddle structure includes a bent tube portion and a straight tube portion formed at both ends of the bent tube portion and protruding from the outer tube. And, at the opening end portion of the straight pipe portion formed at the end portion of the inner pipe, the angle formed by the horizontal line and the axis line of the straight pipe portion is made larger than the angle formed by the horizontal line and the axis line of the multi-cable. To

  With the above configuration, the normal force can be significantly reduced in the saddle structure using a multi-cable. Here, the multi-cable is a cable in which a plurality of strands are arranged inside the covering material and are combined into one.

  In another saddle structure of the present invention using a multi-cable, by changing the angle of the straight pipe portion with respect to the horizontal line, the angle of the straight pipe portion changes, and of course, the appearance changes in the structure of the outlet portion. Is recognized. As a specific change in appearance, as in the saddle structure of Example 1 described later (see FIG. 1), the multi-cable passes almost through the middle portion of the slide pipe. Accordingly, the rubber boots that are substantially concentric with each other are attached to the end of the slide pipe. On the other hand, as a change in the inner pipe, the multi-cable floats from the straight pipe portion at the outlet side end of the straight pipe portion, and does not come into contact with the straight pipe portion. Thus, in the saddle structure of the present invention, the point where the normal component force acts on the straight pipe portion can be moved to the ring nut side as compared with the conventional saddle structure. The bending moment can be reduced and the normal force acting on the straight pipe can be suppressed. Further, the cable bending angle can be made gentle at the portion where the strand starts to be exposed (corresponding to the position b in FIG. 13B).

  In this saddle structure, when the bending radius of the bent pipe portion is 2.5 m or more, the angle difference between the axis of the straight pipe portion and the axis of the multi-cable is preferably 3 ° or less. If the angle difference exceeds 3 °, the cable may be bent in the opposite direction to the conventional case. The angle difference between the axis of the straight pipe portion and the axis of the multi-cable may be appropriately selected depending on the mechanical characteristics and dimensions of the member. For example, when using a multi-epoxy cable made of Sumitomo Electric Steel Wire, the angle difference may be set to the following value.

Cable type Minimum bending radius Angle difference
12S cable 2.5m or more 0.5 °
19S cable 3.0m or more 1.0 °
27S cable 3.5m or more 1.5 °
37S cable 4.0m or more 2.0 °
Here, the 12S cable is a multi-cable in which 12 strands are arranged inside the covering material. In other multi-cables, the number before S represents the number of strands arranged in the multi-cable.

  In designing the saddle structure as described above, in order to increase the angle of the inner pipe straight pipe part with respect to the horizontal line, the curvature of the inner pipe curved pipe part may be reduced, but the curvature of the inner pipe curved pipe part is merely used. There is a possibility that the normal component force at the saddle exit portion cannot be alleviated only by reducing. For example, when the curvature of the inner tube curved pipe portion is reduced, if the center position of the inner tube bent tube portion rises or falls from the initial position, the cable alignment may change from the initial alignment. In this case, the state of the stress acting on each part of the saddle structure may change, and the normal component force may not be relaxed. In order to solve such problems, the present inventors have considered a design philosophy considering the following two points.

[1] Decreasing the curvature of the curved pipe part with the central lower point of the inner pipe curved pipe part designed with cable sag fixed.
[2] When a cable is inserted into the inner pipe, the strands that are evenly arranged at a predetermined interval in the inner pipe straight pipe section are biased to the lower part of the bent pipe section at the center of the inner pipe bent pipe section. Therefore, the amount by which the entire cable moves downward is taken into consideration.

Based on the design concept described above, a specific method for designing a saddle structure using a multi-cable will be described.
First, consider the case where the cable sag shown in FIG. First, the axis of the straight pipe portion 12 at both ends of the inner pipe is extended in the center direction of the main tower to obtain an intersection (inner pipe virtual intersection X1). At the same time, the axis of the cable at the open end of the straight pipe portion is extended in the center direction of the main tower to obtain the intersection (cable virtual intersection Y1). Since the cable is pulled downward in the figure due to the tension force or the weight of the cable, the cable is not in the center of the inner tube but in a position where it contacts the inner tube along the lower portion of the inner tube. Therefore, the line obtained by extending the cable axis is shifted below the line obtained by extending the axis of the straight pipe portion. Here, since the inner pipe is designed in consideration of the cable sag, the two axes described above are parallel to each other. At this time, an angle formed by a horizontal line and a line obtained by extending the axis of the straight pipe portion (and the axis of the cable) is α, and A is a lower point of the inner pipe located at the center of the inner pipe.

  Next, the curvature of the bent tube portion 11 is reduced without moving the position of the cable. That is, the curvature of the bent tube portion 11 is reduced in a state where the lower point B of the inner tube located at the center of the inner tube in FIG. 3B is made coincident with the point A in FIG. By reducing the curvature of the curved pipe section 11, the straight pipe section 12 in FIG. 3 (B) is slightly turned downward compared to the straight pipe section in FIG. The intersection (inner pipe virtual intersection X2) obtained by extending the axis of the straight pipe portion 12 at both ends of the pipe in the center direction of the main tower is located above X1. Therefore, the angle β formed by the horizontal line and a line obtained by extending the axis of the straight pipe portion 12 is larger than α. Here, when the curvature of the bent tube portion 11 is reduced without fixing the central lower point of the bent tube portion 11, the normal component force changes almost only by reducing the bending radius of the cable in the bent tube portion 11. Absent.

  Next, consider a state in which a multi-cable is arranged in the inner pipe of FIG. 3 (B) (see FIG. 4 (C)). At this time, both ends of the cable 30 are positioned at the cable fixing points of the main girder (not shown), and the middle part is positioned by the point B. Also, because the cable 30 is tensioned and the cable 30 itself is rigid. In addition, the cable sag is not changed by a slight change in the curvature of the curved pipe portion 11. That is, the axis of the cable 30 at the opening end of the straight pipe portion 12 is the same as that shown in FIG. 3A, and the angle of the cable is α.

  Finally, as in an actual saddle structure, a state is considered in which the covering material 30c of the multi-cable 30 in the inner pipe is peeled and the strand 30s is exposed (see FIG. 4D). Specifically, considering that the strand 30s in the central portion of the inner tube is biased toward the lower portion of the inner tube at the middle portion of the inner tube, the entire cable 30 is translated downward in the drawing. By this parallel movement, the cable virtual intersection moves from Y1 to Y2. At this time, the covering material 30c comes into contact with the straight pipe portion 12 only at the end of the covering material 30c on the intermediate side of the main tower. Then, the multi-cable 30 can pass through almost the middle of the slide pipe 95 at the end of the slide pipe 95 on the cable fixing point side.

  The above design concept can also be applied to a saddle structure having a structure in which a plurality of independent strands are separated by a cable spacer. When using a cable spacer, as in the case of using a multi-cable, the curvature of the bent pipe portion is reduced with the lower point A of the inner pipe bent pipe portion fixed, and the cable bias in the inner pipe bent pipe portion is reduced. Consider it.

  According to the saddle structure of the present invention, the normal force acting on the straight pipe portion of the inner pipe can be greatly reduced as compared with the conventional saddle structure. Therefore, the thickness of the inner pipe including the straight pipe portion can be reduced. Further, even when a tension difference corresponding to level 2 earthquake motion acts on the cable, the normal component force is greatly reduced, and as a result, the durability of the saddle structure itself is improved.

<Example 1>
Here, the case where the saddle structure of the present invention is applied to a main tower of a bridge such as a cable-stayed bridge or an extradosed bridge will be described as an example. These bridges are constituted by a main girder extending substantially parallel to the ground, a main tower extending substantially perpendicular to the main girder, and a diagonal cable (cable) extending from the main tower to the main girder. The cable used in this embodiment is a so-called multi-cable in which a plurality of strands are combined into one with a covering material. In this embodiment, first, the overall configuration of the saddle structure will be described, and then each component will be described.

(Overview of overall configuration)
FIG. 1 (A) is a partially enlarged view of an exit portion of a saddle structure using a multi-cable. The saddle structure 1 is composed of an outer pipe 20 embedded in a main tower of the bridge and an inner pipe 10 arranged inside the outer pipe 20 as main components, and a multi-cable 30 inserted into the inner pipe 10 to bridge the bridge. The main girder is suspended.

  The outer pipe 20 of the saddle structure 1 is embedded in the concrete main tower so that both end portions thereof open to opposite side walls of the main tower. A reinforcing bar 70 that reinforces the main tower along the longitudinal direction of the outer tube 20 is disposed on the outer periphery of the outer tube 20. In addition, a pressure bearing plate 81 is disposed in the vicinity of the opening end of the outer tube 20 in the side wall of the main tower.

  The inner tube 10 is disposed inside the outer tube 20 and opens at opposite side walls of the main tower so that both end portions thereof protrude from the outer tube 20. Further, the inner tube 10 is fixed inside the outer tube 20 by an inner tube spacer. At this time, a gap is formed between the inner pipe 10 and the outer pipe 20, and a grout discharge hose 63 is inserted into this gap. Further, a ring nut 80 is screwed to the outer peripheral surface of the straight pipe portion 12 formed at the end of the inner pipe 10, and this ring nut 80 is connected to the above-mentioned support plate 81 via a pressure adjusting plate 85. Pressing.

  The multi-cable 30 is inserted into the inner tube 10, and both ends are fixed to a main girder (not shown). The grout 40 is filled between the multi-cable 30 and the inner tube 10, and the multi-cable 30 and the inner tube 10 are integrated via the grout 40. In addition, the slide pipe 95 is screwed to the end of the straight pipe 12 so that the grout 40 does not leak from the gap between the multi-cable 30 and the inner pipe 10 at the inner pipe end (inner pipe straight pipe 12). Further, a rubber boot 96 is attached to the end of the slide pipe 95.

  Hereinafter, each component will be described.

(cable)
The multi-cable 30 is obtained by storing a plurality of strands 30s in a covering material and collecting them together. In this example, the multi-cable 30 was used in which 37 strands 30s coated with epoxy were arranged in a polyethylene coating material (coating material 30c) and combined into one. When the saddle structure 1 is constructed using the multi-cable 30, a part of the polyethylene covering material 30c is peeled off in order to increase the adhesion between the cable 30 and the grout 40. Specifically, with the exception of both ends of the multi-cable 30, when the polyethylene cable 30 is inserted into the inner tube 10, the portion of the polyethylene covering material 30 c located inside the inner tube 10 is peeled to expose the strands 30 s.

(Outer pipe)
The outer tube 20 is not particularly limited as long as it has a predetermined strength and has good adhesion performance with concrete. In this example, a bent tube made of polyethylene was used. The curvature of the outer tube 20 substantially matches the curvature of the bent tube portion of the inner tube 10 described later.

(Inner pipe)
The inner tube 10 includes a bent tube portion 11 having a gentle radius of curvature and a straight tube portion 12 formed at both ends of the bent tube portion 11. The straight pipe portion 12 and the curved pipe portion 11 may be one continuous member, or may be joined as another member by welding or the like. The material of the inner tube 10 is not particularly limited as long as it has a predetermined strength and has good adhesion performance with the grout 40. In this example, a steel bent pipe and a straight pipe were welded to produce an inner pipe.

  The bent pipe portion 11 of the inner pipe has a constant length over the entire length of the bent pipe portion 11 so that the cable 30 disposed inside the inner pipe is not bent and excessive lateral pressure is not locally applied to the cable 30. Has curvature. Further, the curvature of the curved pipe portion 11 is determined so that the cable 30 is not bent to the allowable minimum bending radius or less and the safety of the saddle structure 1 is not impaired. In the saddle structure 1 of the present invention, the curvature of the curved pipe portion 11 is determined based on the design concept already described while considering the minimum bending radius.

  The straight pipe portion 12 of the inner pipe 10 is formed straight from both ends of the curved pipe portion 11. Accordingly, the angle of the straight pipe portion 12 with respect to the horizontal line is determined by the curvature of the curved pipe portion 11. In this example, in consideration of the length and curvature of the inner tube 10, the strength of the cable 30 and the minimum bending radius, the inclination of the axis of the straight tube portion 12 with respect to the horizontal line is a multi-cable with respect to the horizontal line at the end of the straight tube portion 12. It was made 1.5 ° larger than the inclination of 30 axes.

(Grout and grout inlet, grout discharge hose)
The grout 40 is for integrating the inner tube 10 and the cable 40 by filling the inside of the inner tube 10 and hardening. The grout 40 may be a commercially available one. Further, the grout inlet 62 and the grout discharge hose 63 for filling the grout 40 in the inner tube 10 are communicated with the slide pipe 95 and the bent tube portion 11 of the inner tube 10, respectively. The filling of the grout 40 into the inner pipe 10 ends when the grout is injected from the inlet 62 and discharged from the discharge hose 63.

(Slide pipe and rubber boots)
Slide pipes 95 and rubber boots 96 provided at both ends of the inner pipe straight pipe part 12 hold the grout 40 in the inner pipe 10 until the grout 40 is hardened and prevent leakage to the outside of the inner pipe 10. It is. The slide pipe 95 only needs to have a predetermined strength, and a steel pipe is used here. The slide pipe 95 is screwed into the end portion of the straight pipe portion 12 of the inner pipe 10 so that the grout 40 does not leak from the screw fitting portion.

  On the other hand, a known rubber boot 96 may be used. The rubber boot 96 includes a small diameter portion and a large diameter portion, and the large diameter portion covers the end of the slide pipe 95, and the small diameter portion covers the covering member 30c of the multi-cable 30. The inner diameter of the large-diameter portion of the rubber boot 96 before mounting is smaller than the outer diameter of the slide pipe 95, and the inner diameter of the small-diameter portion is smaller than the outer diameter of the covering material 30c. Accordingly, the gap between the slide pipe 95 and the multi-cable 30 at the end of the slide pipe 95 can be sealed by the rubber boot 96, and the grout 40 can be prevented from leaking from both ends of the inner tube 10. .

(Ring nut, bearing plate)
The ring nut 80 is a member that is screwed to the outer periphery of the inner pipe straight pipe portion 12 and presses the side wall of the main tower. The pressure bearing plate 81 is a plate-like member that is embedded in the side wall of the main tower so that the surface is exposed and receives the pressing force from the ring nut 80.

(Pressure adjustment plate)
The pressure adjusting plate 85 is a member for filling a gap formed between the ring nut 80 and the bearing plate 81 when the ring nut 80 is screwed to the straight pipe portion 12. A through-hole through which the inner pipe straight pipe portion 12 can be inserted is provided at the center of the pressure adjusting plate 85. In this example, two taper plates 85p are overlapped to form a pressure adjusting plate 85 (see FIG. 5). The taper plate 85p is a thin steel plate with one surface being flat and the other surface being an inclined surface. That is, when the taper plate 85p is viewed from the side, one end is thick and the other end is thin. In this example, the inclined surfaces of the two tapered plates 85p are overlapped so as to face each other, and the thickness can be changed by rotating the disc (see FIG. 5B). For example, if the right plate 85p in FIG. 5 (B) is rotated 180 °, a pressure adjusting plate having a thick upper end and a thin lower end can be obtained. The surface of the taper plate 85p is treated with Teflon (registered trademark) to make the inclined surface slippery.

  A screw hole 85s to which a screw (for example, a hexagon socket set screw) can be attached is formed in the peripheral portion of the taper plate 85p. By attaching a screw to the screw hole, the screw can protrude outward in the radial direction of the taper plate 85p. By operating a screw projecting radially outward of the taper plate 85p, the taper plate 85p sandwiched between the ring nut 80 and the bearing plate 81 can be easily rotated. Further, by confirming the position of the screw hole 85s, the relative degree of rotation of the two taper plates can be easily confirmed.

(Reinforcing bars)
The reinforcing bar 70 is a member used for increasing the strength of the main tower. A commercially available reinforcing bar 70 was used. In the saddle structure 1 of this example, the reinforcing bars 70 are arranged so as to surround the entire length of the outer tube 20.

(Method for forming saddle structure)
In order to form the saddle structure 1 as described above, the inner pipe 10 is arranged inside the outer pipe 20 at the factory, and both ends of the inner pipe 10 open to the opposite side walls of the main tower at the construction site. To. Next, the multi-cable 30 is inserted into the inner tube 10, and both ends of the cable 30 are fixed to fixing points of a main girder (not shown). Further, the slide pipe 95 is screwed to the end portion of the inner pipe 10 and the rubber boot 96 is attached to the end portion of the slide pipe 95 to seal the inner pipe 10. Next, after tensioning the cable 30, the grout 40 is injected into the inner pipe 10 using the grout inlet 62 of the slide pipe 95 and the grout discharge hose 63 communicating with the inner pipe 10, and the cable 30 and the inner pipe 10 are connected. Try to be united. Then, a ring nut 80 is screwed onto the outer peripheral surface of the straight pipe portion 12 of the inner pipe 10, and the ring nut 80 is abutted against the support plate 81 via the pressure adjusting plate 85.

<Test Example 1>
Next, a test structure was produced using the saddle structure of Example 1, and a test for evaluating the soundness of the saddle structure of Example 1 was performed. In this test example, when the angle of the straight pipe portion of the inner pipe in the saddle structure was changed, changes in strain and displacement generated in the straight pipe portion were measured. Furthermore, the amount of cable lift at the end of the inner pipe straight pipe was measured.

  FIG. 6 shows a test structure used for this test. The test structure has a structure in which the saddle structure 1 is embedded in the simulated main tower 3 made of concrete, and the cable 30 extending from both ends of the saddle structure 1 can be tensioned by the jack 86. The jack 86 is attached to the simulated main tower 3 via the ram chair 87 so that the cable 30 can be tensioned with a predetermined load.

  In this test, a saddle structure 1 having the curvature of the outer tube and the inner tube taken into account when cable sag is taken into consideration was embedded in the simulated main tower 3 to produce a test structure. A base plate having an inclination is disposed between the pressure control plate of the saddle structure 1 and the bearing plate of the simulated main tower 3. By changing the inclination of the base plate, the angle between the axis of the straight pipe portion and the horizontal line was changed.

  In carrying out the test, the rubber boot and the slide pipe were removed at the exit portion of the saddle structure, and a strain gauge and a displacement meter were installed in the straight pipe portion of the inner pipe in the saddle structure. The displacement meter was installed at the end of the straight pipe portion (position a in FIG. 1), which is considered to have the largest displacement when the normal component force is applied. On the other hand, the strain gauge was provided in the vicinity of the ring nut (position b in FIG. 1) where the bending moment concentrated. Then, the strain value and the deflection amount (displacement amount) of the straight pipe portion when the angle difference between the axis of the straight pipe portion and the axis of the cable at the opening end of the straight pipe portion was changed were measured. In addition, for each of the changed angular differences, the strain value of the straight pipe section when the tension to be introduced into the cable is changed between 0.1 Pu to 0.6 Pu (Pu is the tensile tension determined by the JIS standard). The amount of deflection was also measured. The results are shown in FIGS. Further, FIG. 9 shows the result of measuring the cable lift at the end of the straight pipe portion (position c in FIG. 1) when a predetermined tension (0.6 Pu) is introduced.

  FIG. 7 is a graph showing the angle of the straight pipe portion and the deflection amount (displacement amount) of the straight pipe portion when the tension force introduced into the cable is changed. The horizontal axis indicates the angle difference between the straight pipe portion and the cable, and the vertical axis indicates the amount of bending of the straight pipe portion. Since the angle of the straight pipe portion when considering the sag is equal to the angle of the cable, the angle difference between the straight pipe portion and the cable when considering the sag is 0 °. In addition, the angle difference between the straight pipe part and the cable when the sag is not considered is -0.2 °, and the angle of the straight pipe part is larger than the angle of the straight pipe part when the sag is taken into consideration. The angle difference between the straight pipe portion and the cable is 0.5 °, 1.0 °, and 1.5 °. Note that the definition of the angle difference in the graphs of FIGS. 8 and 9 to be described later is the same as in FIG.

  As is clear from FIG. 7, when the angle difference between the straight pipe portion and the cable is 0.5 °, 1.0 °, and 1.5 °, the straight pipe portion is larger than when the angle difference is 0 ° and −0.2 °. The amount of bending at the end of the was greatly reduced. Further, when the angle difference was 0.5 °, 1.0 °, and 1.5 °, the increase amount of the bending amount was small even if the tension introduced into the cable was increased. In particular, when the angle difference was 1.0 ° and 1.5 °, the amount of deflection hardly changed even when the tension introduced into the cable was increased.

  On the other hand, FIG. 8 is a graph showing the strain value of the straight pipe portion when the angle of the straight pipe portion and the tension force introduced into the cable are changed. The horizontal axis represents the angle difference between the straight pipe portion and the cable, and the vertical axis represents the strain value of the straight pipe portion. Further, the broken line in FIG. 8 indicates the yield strain value (1044 μ) of the straight pipe portion used in the conventional saddle structure having the scale of the first embodiment. This straight pipe part is made of steel and its thickness is 15 mm.

  As shown in FIG. 8, the strain value decreased as the angle difference between the straight pipe portion and the cable increased. Moreover, the greater the angle difference, the smaller the increase in strain value even when the tension introduced into the cable was increased. Therefore, in the saddle structure having the angular difference (0.5 °, 1.0 °, 1.5 °) of the embodiment, it is considered that the thickness of the straight pipe portion can be made thinner than before. Here, in the conventional saddle structure (0 ° or −0.2 °), when a tension exceeding 0.6 Pu, for example, a tension corresponding to a level 2 earthquake motion is applied to the cable, the stress acting on the straight pipe portion is It is assumed to be larger than the saddle structure having the angular difference (0.5 °, 1.0 °, 1.5 °) of the embodiment.

  FIG. 9 is a graph showing the amount of cable lift at the end of the inner pipe straight pipe part. The horizontal axis indicates the angle difference between the straight pipe portion and the cable, and the vertical axis indicates the amount of cable lift from the lower portion of the straight pipe portion at the end of the straight pipe portion. In addition, the dotted line in a figure shows the amount of lifting of a cable (19 mm) when a cable exists in the center of a straight pipe part in the exit side edge part of a straight pipe part. As shown in the figure, when the angle difference between the straight pipe part and the cable is 0 ° or -0.2 °, the cable is not lifted at all, and the cable and the straight pipe part are in contact with each other over the entire length of the straight pipe part. there were. It can be inferred that the fact that the cable was not lifted at all was one of the reasons for the high distortion and deflection of the straight pipe when the angle difference was 0 ° or -0.2 ° (see Figs. 7 and 8). ).

  From the results of these test examples 1, the saddle structure using the multi-cable reduces the bending moment acting on the straight pipe portion because the cable does not contact the straight pipe portion at the end of the straight pipe portion. The straight pipe is less bent. Moreover, even if the tension force introduced into the cable is increased, the strain generated in the straight pipe portion hardly changes, so that the thickness of the inner pipe including the straight pipe portion can be made thinner than the conventional one. Specifically, it is also possible to use a straight steel pipe portion having a thickness of 10 mm.

<Example 2>
In Example 2, unlike Example 1, a saddle structure using a plurality of independent strands instead of a multi-cable was manufactured. By using a plurality of independent strands, the structure of the outlet portion is changed from the saddle structure of the first embodiment. Here, the same members as those in the first embodiment are denoted by the same reference numerals, description thereof is omitted, and only differences from the first embodiment will be described.

  FIG. 2 is a view showing an outlet portion of a saddle structure that is considered as one cable with a plurality of independent strands as a set. Since the saddle structure 2 of the present example uses a plurality of independent strands 31, in this saddle structure 2, the plurality of strands 31 are fixed to the end of the straight pipe portion 12. After being inserted through the through hole, it was inserted into the inner tube 10. The inner tube 10 is fixed inside the outer tube 20 by an inner tube spacer 50. A plurality of through holes of the cable spacer 90 are provided, and one strand 31 is inserted into each through hole. Further, since the through holes are arranged at a predetermined interval, the strands 31 inserted through the cable spacer 90 are arranged at a predetermined interval at the end portion of the inner pipe straight pipe portion 12. Further, a water stop structure 91 is provided at the end of the cable spacer 90 so that the grout 40 does not leak from the inner pipe 10. The cable spacer 90 and the water stop structure 91 may be conventional ones. In this example, the same one described in Patent Document 1 was used. The grout 40 was injected from a grout injection hose communicating with the inner pipe straight pipe portion 12, and was discharged from the grout discharge hose 63.

<Test Example 2>
In this test example, the soundness of the saddle structure of Example 2 is evaluated by measuring strain in the straight pipe portion of the saddle structure shown in Example 2. This test was performed using a test structure in which the saddle structure portion of the test structure used in Test Example 1 was replaced with the saddle structure of Example 2. Therefore, the description of the test structure is omitted.

  In this test example, when a strain gauge is installed at the locations a to c in FIG. 2 and the angle of the straight pipe portion of the inner pipe in the saddle structure is changed, the change in strain value generated in the straight pipe portion is measured. did. Here, a is in the vicinity of the ring nut of the straight pipe portion, b is provided at a position in contact with the ring nut on the outer side (main girder side) of the ring nut, and c is provided at a position in contact with the ring nut on the inner side (main tower side) of the ring nut. It was. The measurement results are shown in FIGS.

  FIG. 10 is a graph showing the strain value of the straight pipe portion (strain value at the position a in the figure) when the angle of the straight pipe portion and the tension introduced into the cable are changed. The horizontal axis represents the angle difference between the axis of the straight pipe used for the test and the axis of the virtual straight pipe when the sag is taken into consideration. The vertical axis indicates the strain value of the straight pipe portion. Here, when the angle of the straight pipe portion is increased with respect to the horizon compared to the case where sag is taken into consideration, it is assumed to be positive, and when it is reduced, it is assumed to be negative. Further, the broken line in FIG. 10 indicates the yield strain value (1044 μ) of the steel inner pipe having a thickness of 15 mm.

  As is clear from FIG. 10, in the saddle structure (0.5 °, 1.0 °, 1.5 °) of Example 2 compared to the conventional saddle structure (0 °, −0.2 °), the distortion of the straight pipe portion is increased. The value was very small. Further, even when the tension introduced into the cable was increased, the fluctuation of the strain value was small.

  FIG. 11 is a graph comparing the strain values of the conventional saddle structure (−0.2 °) and the saddle structure (1.5 °) of Example 2 particularly in the portion adjacent to the ring nut. The vertical axis indicates the strain value of the straight pipe portion at the measurement point (b and c in the figure). The left box of the graph shows the value of the conventional saddle structure, and the right box shows the value of the saddle structure of the second embodiment.

  As is clear from FIG. 11, the saddle structure of Example 2 has a very small strain acting on the inside and outside of the ring nut compared to the conventional saddle structure, and is significantly lower than the yield strain value of the inner pipe. It was.

  From the results of Test Example 2 above, it can be seen that even in the saddle structure that holds a plurality of strands at the end of the inner pipe straight pipe portion by the cable spacer, the bending stress acting on the inner pipe straight pipe portion can be reduced. It was. For example, it is possible to use a straight steel pipe portion having a thickness of 10 mm.

  The present invention can be suitably used for cable-stayed bridges, extradosed bridges, and the like. In particular, it can be used for bridges that can withstand earthquakes corresponding to Level 2 ground motion.

It is a schematic block diagram which shows the exit part of this invention saddle structure using several independent strand. It is a schematic block diagram which shows the exit part of the saddle structure of this invention using a multi cable. It is explanatory drawing of the design theory of this invention saddle structure, (A) shows the saddle structure which considered the cable sag, (B) shows the saddle structure which changed the curvature of the curved pipe part of (A). . FIG. 4 is an explanatory view of the design theory of the saddle structure of the present invention, in which (C) is a saddle structure in which a multi-cable is arranged on the saddle structure in (B) of FIG. 3, and (D) is a multi-cable covering. The saddle structure in a partially peeled state is shown. It is a figure which shows a taper plate, (A) is a top view, (B) shows a side view. It is a figure which shows the test structure of Test Example 1 and Test Example 2. It is a figure which shows the result of the test example 1, and is a graph which shows the deflection amount in an inner pipe straight pipe part. It is a figure which shows the result of the test example 1, and is a graph which shows the distortion value in an inner pipe straight pipe part. It is a figure which shows the result of the test example 1, and is a graph which shows the amount of lifting of the cable in the edge part of an inner pipe straight pipe part. It is a figure which shows the result of the test example 2, and is a graph which shows the distortion value in an inner pipe straight pipe part. It is a figure which shows the result of Test Example 2, and is a graph which shows the distortion value in an inner pipe straight pipe part, especially a ring nut vicinity. It is a schematic block diagram of the conventional saddle structure using several independent strand, Comprising: (A) shows the whole structure, (B) shows an exit part, (C) shows an A-A 'cross section. It is a schematic block diagram of the conventional saddle structure using a multi-cable, (A) shows the whole structure, (B) shows an exit part, (C) shows a B-B 'cross section.

Explanation of symbols

1,2 Saddle structure 3 Simulated main tower
10 Inner pipe 11 Curved pipe 12 Straight pipe 20 Outer pipe
30 Multi-cable 30s Strand 30c Covering material 31 Strand
40 Grout 50 Inner tube spacer
61 Grout inlet hose 62 Grout inlet 63 Grout outlet hose
70 Reinforcing bar 80 Ring nut 81 Bearing plate 85 Pressure adjusting plate
85p taper plate 85s screw hole
86 Jack 87 Lamb Chair
90 Cable spacer 91 Waterproof structure 95 Slide pipe 96 Rubber boot
100,101 Saddle structure 200 Main tower
110 Inner pipe 111 Curved pipe section 112 Straight pipe section 120 Outer pipe
130 Strand 140 Grout 150 Inner pipe spacer 160 Grout hose
170 Reinforcement bar 180 Ring nut 181 Bearing plate
190 Cable spacer 195 Waterproof structure
210 Slide pipe 220 Rubber boots
230 Multi-cable 231 Strand 235 Coating material

Claims (5)

An inner pipe through which a plurality of independent strands fixed at both ends to the main girder of the bridge in tension are inserted, an outer pipe buried in the main tower portion of the bridge and covering the outer periphery of the inner pipe, and an inner pipe A saddle structure having a cable spacer that separates a plurality of independent strands from each other at an end thereof,
The inner pipe is formed of a bent pipe part and a straight pipe part formed at both ends of the bent pipe part and protruding from the end part of the outer pipe,
It is a virtual straight pipe portion that is designed in consideration of the cable sag of the cable, considering the plurality of strands as a set , and the virtual cable axis near the exit of the virtual straight pipe portion. When defining a virtual straight pipe that is designed to have parallel axes,
The angle formed by the axis of the virtual straight pipe portion and the horizontal line is α,
If the angle formed by the axis of the straight pipe part and the horizontal line is β,
A saddle structure characterized by β> α . 2. The saddle structure according to claim 1, wherein β−α ≦ 3 ° when the bending radius of the bent pipe portion is 2.5 m or more. A saddle structure comprising an inner pipe through which a multi-cable fixed to both ends of a bridge main girder is inserted in tension and an outer pipe buried in the main tower portion of the bridge and covering the outer circumference of the inner pipe There,
The inner pipe is composed of a curved pipe part and a straight pipe part formed at both ends of the curved pipe part and protruding from the outer pipe,
In the opening end portion of the straight pipe portion formed at the end portion of the inner pipe, the angle formed by the horizontal line and the axis line of the straight pipe portion is made larger than the angle formed by the horizontal line and the axis line of the multi-cable. Saddle structure.   The saddle structure according to claim 3, wherein when the bending radius of the bent pipe part is 2.5 m or more, an angle difference between the axis of the straight pipe part and the axis of the multi-cable is 3 ° or less. body. A bearing plate fixed to the side wall of the main tower in the vicinity of the end of the outer tube, a ring nut screwed to the outer periphery of the inner tube, and a pressure adjusting plate interposed between the bearing plate and the ring nut Prepared,
5. The structure according to claim 1, wherein the pressure adjusting plate is configured to transmit the pressing force of the ring nut evenly to the support plate so that no gap is generated between the support plate and the ring nut. The saddle structure described in Crab.

Images