JP2008184846A - Reinforced concrete slab bridge having small number of main girders - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reinforced concrete slab bridge having a small number of main girders, which solves the problem of fatigue crack having occurred in an upper flange of a transverse girder. <P>SOLUTION: The reinforced concrete slab bridge 10 having a small number of main girders is constructed by setting the plurality of transverse girders 12 between the plurality of main girders 11 at predetermined intervals in a bridge axial direction, and setting a reinforced concrete floor slab 13 on the transverse girders 12. Herein each transverse girder 12 is formed of a lower flange 21, a web 22 erected on the lower flange 21, a joint portion 23 extending upward of the web 22 and embedded in the reinforced concrete floor slab 13, and a number of holes 24 bored therein along an upper side of the joint portion 23. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a reinforced concrete floor slab minority main girder bridge in which a plurality of cross girders are provided at a predetermined interval in the bridge axis direction between a plurality of main girders and a reinforced concrete floor slab is installed on the cross girder.

  With the rationalization or labor saving at the time of designing and constructing steel bridges, PC floor slabs (in the middle branch bridges with spans of 30m to 60m) are more economical than conventional multi-main girder bridges. A two-main girder bridge using a prestressed concrete floor slab or a synthetic floor slab has been adopted (for example, see Non-Patent Document 1).

  As shown in FIG. 6, the PC floor slab 2 main girder bridge 100 is provided with a cross girder 102 having an H or I cross section between two main girders 101, and a PC floor slab 103 is constructed on the upper part. ing. The PC floor slab 103 is fastened with a fixing nut 106 to a PC steel material 105 inserted into the sheath 104. An asphalt pavement 107 is provided on the PC floor slab 103.

  On the other hand, as shown in FIG. 7, the composite floor slab 2 main girder bridge 200 is provided with a cross beam 202 having an H cross section or an I cross section between two main girders 201, and the composite floor slab 203 is disposed on the upper part. Has been built. An asphalt pavement 204 is provided on the synthetic floor slab 203.

  However, PC floor slabs and synthetic floor slabs also have the following problems.

That is,
(1) The construction cost of the superstructure is lower than that of the conventional multi-main girder bridge due to the adoption of the 2-main girder bridge. It is more expensive than RC slabs (reinforced concrete slabs) that have been conventionally used.
(2) When it is necessary to replace the floor slab, the PC floor slab and the composite floor slab are supported by the main girder. The social loss in that case is very large. Even in the case of three or more main girders, PC floor slabs are prestressed in the floor slabs, so replacement with the full width direction is necessary, and traffic is completely stopped.
(3) the case of adopting the PC slab, since design strength of the concrete used in the PC slab is 30 N / mm ² or more, design strength is compared to 24N / mm ² approximately RC slabs, construction site management Therefore, sufficient management is required, and advanced construction technology is required compared to RC floor slab construction.
(4) When a PC floor slab is used with a box girder structure, a problem of prestress loss occurs, and therefore sufficient consideration is required in introducing prestress.

  Therefore, instead of the conventional girder spacing between the floor slab supports, as shown in FIG. 8, the horizontal girders 301 that support the floor slab are arranged more densely in the bridge axis direction than in the prior art, so that the floor slab supports are in the bridge axis direction. Thus, an RC floor slab 2 main girder bridge 300 that allows the RC floor slab 303 to be used with two main girders 302 even if it is wide can be considered.

  However, as shown in FIG. 9A, when the RC floor slab 303 is supported by the cross beam 301, a swinging phenomenon such as arrows a and b occurs in the upper flange 304 of the cross beam 301 by passing the automobile. As a result, fatigue cracks may occur at the weld flange 306 of the upper flange 304 and the vertical reinforcing steel material 305. Since the upper flange 304 of the cross beam 301 is near the neutral axis of the cross section composed of the cross beam 301 and the RC floor slab 303, the upper flange 304 of the cross beam 301 is small as shown in FIG. It has been found that only stress acts.

  On the other hand, when attaching the cross girder 301 to the main girder 302, in order to accurately store the floor slab thickness within a predetermined thickness, as shown in FIG. Since it is necessary to match the height of the upper flange 304, it is necessary to increase the processing degree and installation accuracy of the cross beam, which increases the construction cost of the bridge.

  Further, as shown in FIG. 10, the conventional RC floor slab is provided with a variation in floor slab thickness due to the construction error of the pier 400, the manufacturing error of the main girder 302, and the installation error at the lower part of the RC floor slab 303. Absorption was performed by the constant right and left hunches 308 and 308.

  However, since the conventional RC floor slab 303 has the left and right constant hunches 308 and 308 projecting downward as described above, the formwork on the bottom of the floor slab having an inclined surface for the haunch is accurately measured using plywood or the like. To create well, it required a lot of labor and time, and it became a factor to raise the construction cost of the bridge. For this reason, the demand for the appearance of a so-called hunchless floor slab without a hunch has been increased.

“Birth of a New Steel Bridge II Revised Edition”, Japan Bridge Construction Association, Kiyoto Noda (Publisher), December 2004, p. 4

  The present invention has been made to solve the above-described problems, and a first object of the present invention is to solve the problem of fatigue cracks occurring in the upper flange of the cross beam. It is to provide a reinforced concrete floor slab minority main girder bridge. The second object of the present invention is to provide a reinforced concrete floor slab minority main girder bridge that can absorb the processing error and installation error of the cross beam and can absorb the construction error of the bridge pier even with the hunchless floor slab.

  In order to solve the above-mentioned problem, a reinforced concrete floor slab minor main girder bridge according to the invention described in claim 1 is provided with a plurality of cross girders between a plurality of main girders at a predetermined interval in the bridge axis direction. In a reinforced concrete floor slab minority main girder bridge on which a reinforced concrete floor slab is installed, the transverse girder is extended to a lower flange, a web erected on the lower flange, an upper part of the web, and the reinforced concrete floor It is characterized by being formed by a joint portion embedded in the plate and a large number of holes provided along the upper side of the joint portion.

  A reinforced concrete floor slab minority main girder bridge according to a second aspect of the present invention is characterized in that, in the first aspect, the holes are provided in a horizontal row in the joint portion.

  A reinforced concrete floor slab minority main girder bridge according to a third aspect of the invention is characterized in that, in the first aspect, the holes are provided in a staggered manner in the joint portion.

  The reinforced concrete floor slab minority main girder bridge according to the invention described in claim 4 is characterized in that, in claim 2 or 3, the reinforcing bars are arranged in the hole in the direction of the bridge axis.

  As described above, the invention according to claim 1 is the reinforced concrete floor slab minority main body in which a plurality of cross beams are provided at a predetermined interval in the bridge axis direction between the plurality of main beams and a reinforced concrete floor slab is installed on the cross beam. In the girder bridge, the horizontal girder includes a lower flange, a web erected on the lower flange, a joint extending above the web and embedded in the reinforced concrete floor slab, Since it is formed by a large number of holes provided along the upper side, the upper flange of the cross beam used in the conventional cross beam is omitted. For this reason, it has become possible to avoid the occurrence of fatigue cracks in the upper flange of the cross beam and the weld toe of the vertical auxiliary member, which has been a concern.

  In addition, by eliminating the upper flange used in the conventional cross beam, the stud gibber that is melted on the upper flange of the cross beam is also omitted. The stud gibber must be individually welded to the upper flange of the cross beam according to the quantity calculated in the design by the non-slip section, and the degree of workability is high. In addition, considering the relationship with floor slab reinforcement, individual welding also requires high accuracy, which is a factor that increases the construction cost of composite structuring with bridge-type reinforced concrete floor slabs having steel main girders. However, it was possible to reduce the construction cost of the bridge by reducing the number of stud gibels. When the floor slab is replaced, in the structure of the present invention, unlike the conventional structure, the direction of the main reinforcing bar of the floor slab is the direction of the bridge axis.

  Further, according to the invention according to claim 1, since the joint portion extending above the web is embedded in the reinforced concrete slab, the work of adjusting the upper flange of the horizontal beam to the height of the upper flange of the main beam is unnecessary. Became. For this reason, it is not necessary to increase the workability and installation accuracy of the cross beams more than necessary, and it is possible to reduce the construction cost of the bridge.

  In addition, the invention according to claim 1 is a so-called hunchless type floor slab in which the joint portion extending above the web is embedded in the reinforced concrete floor slab as described above, and the bottom surface of the reinforced concrete floor slab has no haunch. Even if it exists, a cross beam and a reinforced concrete slab can be joined without changing the slab thickness. For this reason, the design and manufacturing work of the formwork became easy, and the construction cost of the bridge could be suppressed.

  In the invention according to claim 2, since the holes are provided in a row in the joint, the mechanical joint force between the plate-like joint at the upper part of the cross beam and the reinforced concrete floor slab is uneven in the transverse direction of the joint. And uniform.

  In the invention according to claim 3, since the holes are provided in a staggered manner in the joint, the mechanical coupling force between the plate-like joint at the upper part of the cross beam and the reinforced concrete floor slab becomes stronger.

  In the invention according to claim 4, since the reinforcing bars are arranged in the hole in the direction of the bridge axis, not only the positioning of the reinforcing bars becomes easy, but also the reinforcing bars can be mechanically arranged.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, for example, in the case of a reinforced concrete floor slab 2 main girder bridge 10, a plurality of cross beams 12 are provided between the two main girders 11, 11 at a predetermined interval in the bridge axis direction, and A reinforced concrete floor slab 13 is supported by the cross beam 12. Asphalt pavement 14 is applied to the reinforced concrete floor slab 13.

  As shown in FIGS. 4 and 5, the cross beam 12 includes a lower flange 21, a web 22 erected on the lower flange 21, a joint 23 extending above the web 22, and the joint It is formed by a large number of holes 24 provided along the upper side of 23.

  Moreover, although the said hole 24 is provided in the horizontal line along the upper side of the said junction part 23 as shown in FIG. 5, it can also be provided in zigzag form if desired. Moreover, it is preferable that the web 22 and the joint portion 23 are not cut by welding or the like but are cut out from a single steel plate. The diameter of the hole 24 is preferably in the range of 30 mm to 80 mm, more preferably in the range of 50 mm to 70 mm. If the diameter is out of this range, the joining force between the joint 23 and the reinforced concrete floor slab 13 is reduced.

  As shown in FIGS. 2A and 3, the joint portion 23 is embedded in the reinforced concrete floor slab 13 and mechanically joined to the reinforced concrete floor slab 13. Further, in the hole 24 provided in the joint portion 23, a main reinforcing bar 15 is arranged in the bridge axis direction, and a distribution reinforcing bar 16 is arranged in the bridge width direction intersecting with the main reinforcing bar 15. In the figure, the code | symbol 17 has shown concrete. As shown in FIG. 2 (b), the lower surface of the reinforced concrete floor slab 13, that is, the position where the conventional upper girder upper flange is located is strong even if the upper girder upper flange is removed because the stress σ is small. No trouble occurs.

  As described above, according to the present invention, the cross girder 12 includes the lower flange 21, the web 22 erected on the lower flange 21, the upper extension of the web 22, and the reinforced concrete floor slab 13. Since it is formed by the joint portion 23 to be buried and a large number of holes 24 provided along the upper side of the joint portion 23, the upper flange of the cross beam used in the conventional cross beam is omitted. For this reason, it becomes possible to avoid the occurrence of fatigue cracks at the weld toe of the upper flange of the cross beam and the vertical stiffener, which has been regarded as a problem in the past. In addition, by eliminating the upper flange that was used in the conventional cross beam, the stud gibber that has been fused to the upper flange of the cross beam is also omitted, so it was possible to reduce the construction cost of the bridge. .

  On the other hand, according to the present invention, as described above, the plate-like joint portion 23 with a hole extending above the web 22 is embedded in the reinforced concrete floor slab 13 so that the upper flange of the horizontal beam is placed above the main beam. No need to adjust to the height of the flange. For this reason, it is not necessary to increase the processing degree and installation accuracy of the cross beam more than necessary, and it is possible to suppress the construction cost of the bridge.

  In addition, as described above, the present invention embeds a plate-like joint portion 23 with a hole extending above the web 22 in the reinforced concrete floor slab 13 so that the bottom surface of the reinforced concrete floor slab has no haunch. Even if it is a hunchless type floor slab, the cross beam 12 and the reinforced concrete floor slab 13 can be joined without changing the floor slab thickness. For this reason, it becomes easy to design and manufacture the formwork, and to suppress the construction cost of the bridge.

  In the above description, the case of a reinforced concrete floor slab 2 main girder bridge has been described, but the present invention can also be applied to a case of a multi-main girder having three or more main girder.

It is a perspective view including a partial longitudinal section of a reinforced concrete floor slab 2 main girder bridge according to the present invention. (A) The principal part expanded sectional view of the RC floor slab near the cross beam, (b) It is a stress diagram of the same place. It is XX sectional drawing of Fig.2 (a). It is sectional drawing of a cross beam. It is a front view of a horizontal beam. It is sectional drawing of PC floor slab 2 main girder bridge. It is sectional drawing of a composite floor slab 2 main girder bridge. It is a perspective view containing the partial cross section of RC floor slab 2 main girder bridge. (A) The principal part expanded sectional view of the RC floor slab near the cross beam, (b) It is a stress diagram of the same place. It is a perspective view containing the partial cross section of RC floor slab 2 main girder bridge which has a haunch.

Explanation of symbols

10 Reinforced concrete floor slab 2 main girder bridge 11 Main girder 12 Cross girder 13 Reinforced concrete floor slab 21 Horizontal girder lower flange 22 Horizontal girder web 23 Joint between floor slab and cross girder 24 Hole

Claims (4)

  In the reinforced concrete floor slab minority main girder bridge in which a plurality of cross girders are provided at predetermined intervals in the bridge axis direction between the plurality of main girders and the reinforced concrete floor slab is installed on the cross girder, And a web standing on the lower flange, a joint extending above the web and embedded in the reinforced concrete floor slab, and a plurality of holes provided along the upper side of the joint. Reinforced concrete floor slab minority main girder bridge.   The reinforced concrete floor slab minority main girder bridge according to claim 1, wherein the holes are provided in a row in the joint portion.   The reinforced concrete floor slab minority main girder bridge according to claim 1, wherein the holes are provided in a staggered manner in the joint.   The reinforced concrete floor slab minority main girder bridge according to claim 2 or 3, wherein reinforcing bars are arranged in the hole toward the bridge axis direction.

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