JP3908816B2 - Construction method of suspended floor slab bridge - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention, thin relates concrete plate member strategy for Tsuridoko slab bridge was stretched relates especially how to build a Tsuridoko slab bridge in which the bridge length is laid continuously increased in a plurality of span.
[0002]
[Prior art]
As shown in FIG. 7A, the suspended floor slab bridge has a structure in which a concrete floor slab 102 containing a high-strength steel material is stretched between abutments 101 and 111 firmly fixed to the ground or rock by an anchor 104 or the like. Format. As shown in FIG. 7B, the concrete slab 102 is a member that is extremely thin compared to the span length, and prestress is introduced in the axial direction of the bridge, and the tensile resistance of the steel material 105 causes the gap between the abutments. It is supported by suspension. And the upper surface of this floor slab becomes a bridge surface. Also, in such a structure, the concrete floor slab is suspended and supported, resulting in a large deflection and a gradient in the bridge surface, but a pillar is provided on this concrete floor slab to support the short girder between the branches, The structure which forms a flat bridge surface may be sufficient.
The concrete floor slab 102 is flexible because the thickness of the member is small. Instead of supporting the load with the bending rigidity of the member, the concrete floor slab 102 is supported by suspension from the abutments 101 and 111 on both sides by axial tension. To do.
[0003]
Such a structure has the disadvantage that the amount of deformation increases due to the loading of a live load and the vibration due to a live load or wind load increases, but it is possible to bridge long diameters with a simple structure. It has a structure that is suitable for pedestrian bridges such as deep valleys.
[0004]
[Problems to be solved by the invention]
However, when the span length of the suspended floor slab bridge as described above is about 200 m or more, the wind and the vibration caused by the pedestrian on the bridge increase and exceed the allowable limit, which may impair the stability. To solve this problem, it is conceivable to provide a suspended floor slab bridge with a plurality of spans with short spans between the abutments at both ends, but depending on the terrain of the construction site, a high strut must be provided. In many cases, a large foundation is required. Further, a large amount of temporary members for constructing the support, such as scaffolding / supporting support / temporary support, may be required, resulting in a large construction cost.
[0005]
The present invention has been made in view of the circumstances as described above. The purpose of the present invention is to provide a support member at an appropriate position according to the terrain even when the bridge length is increased, and to stabilize vibration and vibration. It is to provide a method for constructing a suspended floor slab bridge with excellent properties.
[0006]
[Means for Solving the Problems]
In order to solve the above problem, the invention according to claim 1 is provided with a step of providing two abutments so as to face both sides of the bridge point, and fixing to the ground or the rock by an anchor, and a lower end below the abutment An oblique strut supported on the ground or bedrock is raised obliquely upward, one end of the first cable is fixed to the head of the oblique strut, and the other end is fixed to one of the abutments. A step of stretching a second cable between the head of the diagonal column and the other column or the other of the abutment, and a plurality of the first cable and the second cable. Suspending and supporting a plate-like concrete block with a gap; embedding the first cable and the second cable, and casting the concrete so that these cables and the plurality of concrete blocks are integrated; Setting Further, a step of placing concrete between the concrete blocks to form a series of concrete slabs, and a cable for introducing prestress in a duct provided in the axial direction of the concrete slab, And a method for constructing a suspended floor slab bridge including a step of introducing a compressive force in an axial direction of the concrete slab.
[0007]
The invention according to claim 2 is the construction method of the suspended floor slab bridge according to claim 1 , wherein the step of raising and supporting the oblique struts obliquely upward is substantially vertical with the lower end supported rotatably. A strut is constructed, one end of the first cable is fixed to the head, the first cable is held against the abutment, and the cable is gradually sent out to incline the strut, at a predetermined angle. After that, the cable is fixed to the abutment.
[0008]
In the above suspension deck bridge , the concrete floor slab is made of concrete having a compressive strength of about 300 to 600 kg / cm ^2. Even if the concrete floor slab is deformed by vibration or shaking, the concrete strain is almost elastic. The member thickness is determined so as to be within a range showing a typical behavior.
[0009]
The cable can be made of high-strength steel (PC steel) widely used for prestressed concrete, and includes steel wire, steel strand, steel bar, and the like. These steel materials are fixed in the concrete of the abutment or the concrete of the floor slab. For fixing, those widely known as fixing tools when introducing prestressed into the concrete can be used.
[0010]
For example, as shown in FIG. 1, the oblique struts support the concrete floor slab from an obliquely lower part at an intermediate portion between two abutments, and do not necessarily have to be arranged symmetrically near the abutments on both sides. The height, the angle, etc. may be asymmetric, and one may be arranged vertically as shown in FIG. 6 (a). Moreover, as shown in FIG.6 (b), it may be arrange | positioned only at one side.
[0011]
(Function)
In the suspended floor slab bridge constructed by the method of the present invention, since it has diagonal struts supporting the middle part of the concrete floor slab stretched between the abutments from diagonally below, the deflection amount of the concrete slab, that is, the abutment Can significantly reduce the amount of sag from the position supported by, and can suppress vibration and deformation due to the loading of a live load and wind.
Further, by supporting from obliquely below, even if the landform of the bridge point is steep, it can be effectively supported with a short member length. Furthermore, as shown in FIG. 1, the oblique struts arranged in an oblique direction are stably integrated with an abutment fixed to a rock or ground and a concrete slab connecting the abutment and the head of the oblique strut. The horizontal component of the reaction force of the diagonal support is not required to balance the force with the reaction force of the abutment or support on the opposite side. For this reason, even if it is an asymmetrical structure, excessive force does not act on each member, and the structure according to the condition of bridge | crosslinking points, such as topography, can be selected.
[0012]
Furthermore, since at least a part of the steel material arranged in the concrete slab is fixed at both ends near the head of the above-mentioned diagonal column and the abutment behind it, the number of steel materials arranged in this part or the disconnection The area can be increased from the central span of the bridge, and a rational arrangement of steel materials is possible.
[0013]
And in the construction method of the suspended floor slab bridge according to claim 1, one end of the first cable is fixed to the head of the slant strut that is raised obliquely upward, and the other end is the abutment that is behind the slant strut. Since the first cable is used as a steel material included in the concrete floor slab, the temporary material for supporting the oblique strut can be reduced and inexpensively. Reasonable construction is possible.
[0014]
Moreover, in the construction method of the suspended floor slab described in claim 2, since the diagonal strut is constructed substantially vertically and is rotated around the lower end to a predetermined angle, it is easy to support the construction of this diagonal strut. Thus, the temporary material can be reduced.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic shape view and a sectional view showing a suspended floor slab bridge constructed by the method of the invention according to claim 1 or claim 2 . FIG. 2 is a partially enlarged view of the same suspended floor slab bridge.
This suspension floor slab bridge is a pedestrian bridge built in a slightly deep valley, and two abutments 1 and 11 provided to face both sides of the bridge point, and a concrete floor slab 2 stretched between these abutments And the main part is comprised by the two diagonal support | pillars 3 and 13 which support the said concrete floor slab 2 from diagonally downward.
[0016]
The abutments 1 and 11 are made of reinforced concrete, are installed on a rock, and are firmly fixed to the ground by a plurality of ground anchors 4.
The concrete floor slab 2 is a thin concrete plate-like member as shown in FIG. 1 (b). A plurality of steel strands 21 are arranged in the axial direction of the bridge, and the tensile force when stretched between abutments. On the other hand, the steel strand 21 and the concrete resist each other.
[0017]
The steel strand 21 is arranged by dividing the two abutments 1 and 11 into three parts, and as shown in FIG. 2, one end of the first cable 21a is fixed in the concrete of the first abutment 1. The other end is fixed on the second abutment 11 side slightly from the joint portion with the first oblique column 3. One end of the second cable 21b is fixed on the first abutment 1 side slightly from the joint with the first oblique support column 3, and the other end is fixed on the second abutment 11 side slightly from the second oblique support column 13. In the third cable (not shown), one end is fixed to the first abutment 1 side slightly from the joint portion with the second oblique column 13, and the other end is fixed to the second abutment 11. ing. Thus, each cable is arrange | positioned so that a mutual end part may wrap in the junction part with the diagonal support | pillars 3 and 13, and can resist a tensile force over the full length of the concrete floor slab 2. FIG.
Further, from the vicinity of both edges of the concrete slab 2, a rail 6 that is continuous in the axial direction is raised, and the concrete slab 2 is appropriately paved to form a walking path.
[0018]
Since such a concrete floor slab 2 has a very small member thickness with respect to the span length, it easily bends and is stretched between two abutments like a flexible strip member. Since the bending stress generated in the concrete is small due to the small thickness of the member, and the tensile force of the steel strand is introduced so that compressive stress acts on the concrete in the axial direction, the concrete slab vibrates.・ Even if shaking or deflection due to the weight of pedestrians occurs, harmful cracks will not occur in concrete.
[0019]
The diagonal strut is a reinforced concrete member, the lower ends of which are supported by concrete foundations 5 and 15 provided below the abutment, are raised obliquely upward toward the center of the bridge, and the head is integrated with the concrete floor slab 2. It is joined to become.
[0020]
In such a suspended floor slab bridge, even if the bridge length is increased, the intermediate part is supported by the oblique struts 3 and 13, so the height difference due to the drooping of the suspended concrete floor slab 2 can be greatly reduced, Vibration and shaking caused by wind etc. can be suppressed to a small level.
In addition, since the columns are arranged obliquely, the concrete floor slab 2 can be effectively supported without making the column height too large even on steep terrain. Furthermore, since almost no bending moment is generated in the concrete floor slab 2, there is no large bending moment in the column even if the column is placed at an angle, and it is possible to avoid excessive construction costs by reducing the member dimensions. Can do.
[0021]
Next, the construction method of the suspended floor slab bridge will be described. This construction method is an embodiment of the invention described in claim 1 or claim 2.
First, the slope at the bridge point is excavated, and abutments 1 and 11 made of reinforced concrete are installed as shown in FIG. This abutment is firmly fixed to the rock by the ground anchor 4. The ground anchor 4 is fixed to the rock by inserting PC steel into a borehole drilled in the rock and applying mortar grout.
[0022]
On the other hand, the foundation 5 of the diagonal support 3 is provided below the abutment. On this foundation, as shown in FIG. 3 (b), the oblique strut 3 is constructed substantially vertically, the first cable 21 a is fixed to the head thereof, and this cable is temporarily fixed to the abutment 1. Then, the lower end of the oblique column 3 can be rotated, and the first cable 21a is gradually sent out from the abutment 1 to incline the oblique column 3, and when the predetermined angle is reached as shown in FIG. 1 cable 21 a is fixed to the abutment 1. Similarly, the second oblique column 13 is also raised on the foundation 15 provided below the opposite abutment 11 and is tilted while being supported by the third cable 21c. The cable 21c is fixed to the abutment 11.
[0023]
Next, as shown in FIG. 4A, the second cable 21 b is stretched between the head of the first diagonal column 3 and the head of the second diagonal column 13. Then, as shown in FIG. 4B, a plurality of plate-like concrete blocks 22 are suspended and supported by the first cable, the second cable, and the third cable at intervals. The number and the cross-sectional area of the second cable 21b are determined so that the second cable 21b has a cross-sectional amount sufficient to suspend and support the concrete block. Further, if the first cable 21a and the third cable 21c are not enough to suspend and support the concrete block, only the cables used when the oblique struts are rotated and moved are additionally arranged.
As shown in FIG. 5 (a), the concrete block has a groove-like recess 22a in the axial direction on the upper surface, and an anchor bolt 23a planted at the bottom of the groove-like recess 22a, The cable 23 is suspended and supported by the cable 21 by the nut 23b screwed to the plate and the plate 23c locked to the anchor bolt, and the cable 21 is fixed so as to be accommodated in the groove-shaped recess 22a.
Then, concrete 22b is cast in the groove-shaped recess 22a, and as shown in FIG. 5 (b), the cable 21 is embedded, and concrete is also cast between the concrete blocks, so that the two abutments 1, A concrete floor slab 2 continuous between 11 is constructed.
[0024]
The concrete block 22 is provided with a duct 22c in the axial direction. A sheath is connected between the blocks so that the duct communicates, and prestressing is performed before or after placing the concrete between the blocks. A cable for introduction (secondary cable) is inserted and tensile force is introduced after the cast-in-place concrete between the concrete blocks is hardened. As a result, the amount of deflection of the concrete slab 2 (the amount of sag when suspended) is reduced, and axial compressive stress is introduced to the entire area of the concrete slab 2, as shown in FIG. 4 (c). Complete a suspended floor bridge.
[0025]
In the above embodiment, the diagonal struts 3 and 13 are provided on both sides of the bridge length. However, as shown in FIG. 6A, the structure is substantially the same even when the right bank strut 33 is vertical. It can be. Further, as shown in FIG. 6B, in the structure having no support on the right bank side, the other end of the second cable having one end fixed near the head of the oblique support 3 is directly fixed to the abutment 41 on the opposite side. Is done.
[0026]
【The invention's effect】
As described above, in the suspended floor slab bridge constructed by the method according to the present invention, since the concrete floor slab is provided with the oblique support that supports the concrete floor slab from obliquely below, the height difference of the floor slab upper surface due to the floor sag hanging. And vibration and vibration due to wind, live load, etc. are suppressed. In addition, even if the bridge point is steep terrain, it is possible to install a support post in the middle of the bridge without increasing construction costs. It can be arbitrarily selected depending on the case.
[Brief description of the drawings]
FIG. 1 is a schematic view and a cross-sectional view showing a suspended floor slab bridge constructed by the method of the invention according to claim 1 or claim 2 ;
FIG. 2 is a partially enlarged view of the suspended floor slab bridge shown in FIG. 1;
3 is an embodiment of the invention according to claim 1 or claim 2, and is a construction diagram showing a construction method of the suspended floor slab bridge shown in FIG.
FIG. 4 is a construction diagram showing a construction method of the suspended floor slab bridge shown in FIG. 1;
FIG. 5 is a cross-sectional view of a concrete slab during construction of the suspended floor slab bridge shown in FIG.
FIG. 6 is a schematic view showing another example of a suspended floor slab bridge that can be constructed by the method according to the first or second aspect of the present invention.
FIG. 7 is a schematic diagram and a cross-sectional view of a conventionally known suspended floor slab bridge.
[Explanation of symbols]
1,11,41 Abutment 2 Concrete slab 3,13,33 Diagonal strut 4 Ground anchor 5,15 Diagonal strut foundation 6 High rail 21 Cable (primary cable)
22 Concrete block 23a Anchor bolt 23b Nut 23c Plate

Claims (2)

Providing two abutments so as to face both sides of the bridge point, and fixing to the ground or rock with anchors;
An oblique strut supported at its lower end on the ground or bedrock below the abutment is raised obliquely upward, one end of the first cable is fixed to the head of the oblique strut, and the other end is fixed to one of the abutments And supporting the oblique struts;
Stretching the second cable between the head of the oblique strut and the other strut or the other of the abutment;
Suspending and supporting a plurality of plate-like concrete blocks with a gap between the first cable and the second cable;
The first cable and the second cable are embedded, concrete is placed so that these cables and the plurality of concrete blocks are integrated, and concrete is placed between the concrete blocks to form a series. A concrete floor slab of
Including a step of placing a cable for introducing a prestress in a duct provided in an axial direction of the concrete slab, and introducing a compressive force in an axial direction of the concrete slab by introducing a tensile force. How to build a suspended floor slab bridge. In the construction method of the suspended floor slab bridge according to claim 1,
The step of raising and supporting the oblique struts obliquely upward,
Constructing a substantially vertical support with the lower end pivotably supported, fixing one end of the first cable to this head,
The suspended floor slab is characterized in that the first cable is held with respect to the abutment, and the cable is gradually sent out to incline the support column so that the cable is fixed to the abutment after a predetermined angle. How to build a bridge.

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