JP2010037726A - Structure for temporarily fixing pc girder of column capital section in cantilever erection method - Google Patents

Abstract

Provided is a column head PC girder temporary fixing structure in which removal of a column head PC girder temporary fixing member is easily performed in a short time.
A concrete temporary bridge 12 is interposed between a bridge column head PC girder 11 and an upper end of a substructure 10 and a PC tension member 13 is temporarily used for the substructure 10. When temporarily fixing the column head of the overhanging construction PC girder to be fixed, the temporary anchor 12 has a number of shear keys 24 integrally projecting on the upper and lower surfaces, and the shear key 24 is provided on the lower surface of the column head PC girder on the upper surface side of the temporary anchor. It is fitted to the upper surface of the substructure, and the shear key 24 is used to counter the horizontal shearing force between the temporary tack 12 and the column head PC girder 11 and the substructure 10.
[Selection] Figure 1

Description

  The present invention relates to an overhanging construction method constructed by sequentially projecting bridge girders in a cantilevered manner, in which a column head PC girder temporary in an overhanging construction method for temporarily fixing a column head PC girder installed on a substructure such as a bridge pier is provided. It relates to a fixed structure.

    In general, in the overhanging construction method of PC bridge, prestress is introduced to the entire continuous girder after erection, but during the overhanging construction, a substructure such as a pier and a column head PC supported on the substructure. The girders are temporarily fixed to ensure the stability when erected.

  Further, after the end portions of the beams that are sequentially projected to face each other are attached to each other to form a continuous beam, it is necessary to release the temporary fixing in order to introduce prestress to the entire continuous beam. .

  The conventional temporary fixing structure is generally the structure shown in FIG. 5 (for example, Patent Document 1). In the figure, 1 is a substructure mainly composed of piers, and 2 is a column head PC girder. When forming the column head PC girder 2, a temporary steel rod 3 made of reinforced concrete is installed on the substructure 1, and the PC tension material 4 having the lower end fixed in the substructure 1 is penetrated into the temporary frame 3. The upper end of the pillar head PC girder 2 is supported on the upper surface side of the pillar head PC girder 2 to fix the tension, thereby countering the vertical moment of rotation of the overhanging girder.

On the other hand, both ends of the H-shaped steel 5 are installed in a state where both ends of the H-shaped steel 5 are embedded in the substructure 1 and the column head PC girder 2 to counter the horizontal shearing force at the time of an earthquake.
Japanese Patent Laid-Open No. 7-71007

  In general, in the above-mentioned continuous girder type overhang construction method, prestress is introduced to the entire continuous girder in a state where opposing girder ends that are formed by cantilevering are joined, and the girder ends are joined. After this, it is necessary to quickly introduce prestress, but prestress is difficult to be introduced if the space between the column head PC girder and the substructure is temporarily fixed. For this reason, it is necessary to release the temporary fixing promptly.

  However, in the conventional column head PC girder temporary fixing structure described above, the temporary anchor receiving the vertical force is often made of reinforced concrete, and the concrete must be suspended and the reinforcing bar cut to remove it. The work is extremely difficult.

  In addition, the H-shaped steel that is responsible for the shear resistance in the horizontal direction has its upper and lower ends embedded in the column head PC girder and the substructure, so it must be cut with gas, etc. The cut surface will be exposed, and the exposed surface must be rust-proofed.

  As described above, since the conventional column head PC girder temporary fixing requires many difficult operations, removal in a short time is difficult and there are problems such as durability.

  In view of such a conventional problem, the present invention provides an overhanging structure in which the column head PC girder temporary fixing member can be easily removed in a short time and the prestress can be introduced in a short time after the girder is continued. The purpose is to provide a column head PC girder temporary fixing structure in the construction method.

The feature of the invention according to claim 1 for solving the conventional problems as described above and achieving the intended purpose is that the bridge column head PC girder for overhanging construction is placed between the upper end of the substructure. In the column head temporary fixing structure of the overhanging construction PC girder in which a concrete temporary fence is interposed and the column head PC girder is temporarily fixed to the substructure using a PC tension material,
The temporary tack has a plurality of shear keys integrally projecting on the upper and lower surfaces, and the shear keys are fitted to the lower surface of the column head PC girder and the lower construction surface on the upper face of the temporary tack, This is to counter the horizontal shearing force between the column head PC girder and the substructure.

  According to a second aspect of the present invention, in addition to the structure of the first aspect, the temporary tack has a steel shell constituting a side peripheral surface, and the steel shell is filled with unreinforced concrete. There is in being.

  According to a third aspect of the present invention, in addition to the configuration of the first or second aspect of the invention, the shear key is configured so that the ridges in the direction orthogonal to the bridge axis direction are alternately arranged in the bridge axis direction. That is, it is configured by forming the wave shape to be arranged.

  In the present invention, as a temporary tack, use a thing having a large number of shear keys integrally projecting on the upper and lower surfaces, the shear key is fitted to the bottom face of the column head PC girder on the upper face side of the temporary tack and the lower work surface, By using the shear key to oppose the horizontal shearing force between the anchor and the column head PC girder and the substructure, there is no need for the H-shaped steel that provides the horizontal shearing resistance that has been used in the past. Therefore, the temporary fixation release work for the column head PC girders is completed by releasing the tension of the PC tendon and removing the temporary tacks. Can be completed.

  Further, since the H-shaped steel that imparts horizontal shear resistance is not used, the cutting work and the rust prevention work after the cutting work are not required, and the number of work steps is significantly reduced.

  Further, in the present invention, the temporary tack has a steel shell constituting the side peripheral surface, and is constituted by filling the steel shell with unreinforced concrete, so that the temporary tack is removed when the steel is removed. The shell can be easily removed by cutting by gas cutting or the like, and the concrete remaining after the removal of the steel shell is straight, so it can be removed easily and in a short time by a concrete breaker.

  Furthermore, in the present invention, the shear key is formed by forming a corrugated shape in which the ridges in the direction perpendicular to the bridge axis direction are alternately arranged in the bridge axis direction, so that the match key type is used as the temporary key. The corresponding surfaces of the lower substructure and the upper column head PC girder can be easily formed in a shape that matches the upper and lower shear keys.

  Next, embodiments of the present invention will be described based on the examples shown in FIGS. In the figure, reference numeral 10 denotes a substructure such as a pier, and 11 denotes a column head PC girder temporarily fixed on the substructure 10. This temporary fixing is performed by the temporary tack 12 and the PC tension material 13. The lower end of the PC tension member 13 is buried and fixed in the substructure 10, the upper end side is penetrated to the column head PC girder 11 through the temporary anchor 12, and the upper end is tension fixed by the fixing tool 14 via the bearing plate. .

  As shown in FIGS. 2 to 4, the temporary tack 12 includes a steel shell 20 made of steel on the side peripheral surface excluding the upper and lower surfaces, and is constructed by placing concrete 21 therein. Has an unreinforced concrete structure that does not use rebar.

  The steel shell 20 constitutes the side peripheral surface of the temporary tack 12, and is integrally provided with a partition wall 22 for partitioning the interior into a plurality of compartments, and each compartment is filled with concrete 21. ing.

  The upper and lower surfaces of the temporary tack 12 are protruded from the upper and lower edges of the steel shell 20 by the height of a shear key, which will be described later, and concrete 21 is placed thereon, and a number of shear keys 24 are integrally formed on the upper and lower surfaces. Is formed.

  The upper and lower surfaces of the temporary tack 12 are formed by alternately arranging the concave grooves 24 a and the protrusions 24 b, so that the cross section is formed into a corrugated shape, and the corrugated convex portion serves as the shear key 24. The shear key 24 composed of the ridges 24a is installed in a direction perpendicular to the bridge axis direction of the column head PC girder 11.

  The lower surface of the column head PC girder 11 and the upper surface of the lower work 10 to be joined to the upper and lower surfaces of the temporary tack 12 are formed to fit with each other, and the lower surface of the column head PC girder 11 is interposed between the shear keys 24 of the temporary tack. In addition, the shear key 25 on the upper surface of the lower work is closely fitted.

  First, the temporary anchor 12 is formed as a concrete block with a steel shell 20, and when the upper surface of the substructure is formed, the temporary anchor 20 is placed on the upper surface of the substructure before the substructure concrete is solidified. By placing, the shear key 25 is formed in a shape in which the lower surface of the temporary tack 20 fits closely to each other, and the column head PC girder 11 is directly attached to the upper face of the temporary tack 20 thus installed on the upper face of the substructure 10. By placing the concrete to be formed, the shear key 25 can be formed in a shape in which the upper surfaces of the temporary tacks 20 are in close contact with each other.

  The shear keys 24 and 25 described above are formed in a corrugated cross section in this embodiment, but other than this, the cross section may be a square-shaped protrusion such as a trapezoid, and furthermore, a lattice-like concave. It may be a square protrusion formed by forming a groove.

  In this way, the temporary shank 20 having the shear keys on the upper and lower surfaces is used, and the shear keys 24 on the upper and lower surfaces are closely fitted to the lower surface of the column head PC girder 11 and the upper surface of the lower work 10, and By applying a load in the direction of pulling between the work 10 and the column head PC girder 11, the presence of the shear key 24 can sufficiently counter the horizontal shearing force generated during the construction of the bridge girder, which has been conventionally used. In addition, no H-shaped steel for shear resistance is required.

  Further, buckling is prevented by the steel shell 20 on the outer peripheral surface against a vertical load acting on the temporary anchor 12 at the time of temporary fixing and bridge girder extension construction, and it can withstand the same as or more than reinforced concrete.

  And, when releasing the temporary fixation, after releasing the tension by the PC tendon 13 as in the conventional case, the steel shell 20 on the peripheral surface of the temporary tack 12 can be easily removed by cutting from the surface, Since the concrete 21 remaining after the steel shell 20 is removed is unreinforced concrete in which no reinforcing bars are embedded, it can be easily removed by a simple device such as a concrete breaker.

  As described above, the temporary fixation after the continuous girder between the substructures is completed is released by the tension release by the PC tension member 13 and the above-described easy removal work of the temporary tack 12 in a short time. Since the removal of the H-shaped steel as described above is unnecessary, the prestress introduction work for the continuous girder can be performed at an early stage.

It is a longitudinal cross-sectional view which shows the temporarily fixed state of the column head PC girder with respect to the substructure which is one Example of this invention. It is an expanded sectional view of the temporary tack part currently used for the Example shown in FIG. It is a top view of the temporary tack used for the Example shown in FIG. FIG. It is a longitudinal cross-sectional view which shows the temporarily fixed state of the column head PC girder with respect to the conventional substructure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Substructure 11 Column head PC girder 12 Suspension bar 13 PC tension material 14 Fixing tool 20 Steel shell 21 Concrete 22 Bulkhead 24 Shear key 24a Groove 24b Projection 25 Shear key

Claims (3)

A concrete temporary fence is interposed between the column head PC girder of the bridge for overhanging construction and the upper end of the substructure, and the column head PC girder is temporarily fixed to the substructure using a PC tension material. In the column head temporary fixing structure of overhanging construction PC girder,
The temporary tack has a plurality of shear keys integrally projecting on the upper and lower surfaces, and the shear keys are fitted to the lower surface of the column head PC girder and the lower construction surface on the upper face of the temporary tack, Column head temporary fixing structure of overhanging PC girder characterized in that it is made to resist horizontal shearing force between the column head PC girder and substructure.   The column head temporary fixing structure of an overhanging construction PC girder according to claim 1, wherein the temporary rod has a steel shell constituting a peripheral surface of the side portion and is filled with unreinforced concrete in the steel shell. .   The overhanging construction PC according to any one of claims 1 and 2, wherein the shear key is formed by forming a corrugation in which concave and convex strips oriented in a direction perpendicular to the bridge axis direction are alternately arranged in the bridge axis direction. Girder head temporary fixing structure.

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