JPS586004B2 - Construction method of arch bridge - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a diagonal suspension construction method for a lower deck type arch bridge.

One of the construction methods for constructing arch bridges (arch bridges, Rose girders, Langer girders, etc.) in mountainous areas is the cable erection method. Conventionally, direct suspension methods, diagonal suspension methods, and a combination of both methods have been used. ing.

With the diagonal suspension method, there is no need to suspend the entire steel weight except for the Langer girder; after only the arch section is erected using the diagonal suspension method, the stiffening girder, floor assembly, etc. can be loaded onto the arch ribs themselves, so it is not necessary to suspend the entire steel weight. Lowering method (mainly direct hanging method)

Even with the diagonal suspension method, the entire steel weight of the Langer girder is suspended.

) The scale of the hanging equipment (temporary equipment) can be smaller than that of the previous version.

However, in the diagonal suspension method, as shown in Figure 5 a to h, the horizontal force of the diagonal suspension rope a acts on the support part c of the arch b, and the arch part b is completed as shown in Figure 5 g. Even after this, a horizontal component force as an arch is generated until the stiffening girder d or the tie is connected, as shown in Fig. 5h.

Moreover, the horizontal force is generally maximum in the state shown in FIG. 5h, which is just before the stiffening girder or tie is connected.

Among arch-based bridges, for the upper deck type and middle deck type, the arch support section is usually able to withstand the forces during construction, but in the case of the lower deck type, the completed structure requires no compensation. The rigid girder or tie receives the horizontal force of the arch,
The support part or substructure of an arch is usually designed with only the horizontal force at the time of an earthquake or typhoon in mind.

Therefore, when constructing a lower passage type using the diagonal suspension method, it is sufficient to design the substructure by taking into consideration the acting forces during erection, but in general, it is necessary to design the substructure in consideration of the forces acting during erection. The horizontal force that sometimes acts is very large, and the substructures, other than bridge abutments on good ground, become very large and uneconomical.

In addition, if the substructure does not have the strength to withstand the horizontal force during erection, the direct suspension method will be used, but with this direct suspension method, not only the arch section but almost the entire steel weight must be suspended. As a result, the scale of the hanging equipment becomes large and the installation cost is extremely high.

The present invention was made in order to eliminate the drawbacks of the conventional construction method described above, and it is possible to erect a lower deck type arch bridge using the diagonal suspension method without applying a large horizontal force to the substructure. The aim is to significantly reduce construction costs.

In other words, the horizontal component force during construction using the diagonal suspension method acts in opposite directions at both ends of the bridge, so by tying the arch near the support with a temporary tie (wire rope, tension rod, etc.), the horizontal component force can be reduced. can be canceled out so that only the horizontal force corresponding to the unbalance is applied to the substructure.

The present invention is an improved method of diagonal suspension construction based on this principle.

An embodiment of the present invention will be explained below with reference to FIGS. 1 to 4.

In the figure, 1 is a river, 2 is on both banks, 3 is a bridge abutment, 4 is a steel tower on both banks, 5 is a restraining cable, 6 is an anchor block, 7 is a crane cable stretched between the steel towers 4, 8 is a steel tower The crane carrier, 9 is an arch rib, and 10 is a diagonal hanging rope that hangs each arch rib 9 diagonally from the steel tower 4.

In the present invention, when assembling the arch ribs 9 sequentially via the diagonal suspension ropes 10 using the abutments 3 on both left and right banks 2 as supporting points,
At the initial stage, the arch ribs 9 at both left and right ends are connected by a connecting member 11 such as a wire rope or a tension rod whose length is adjustable.

FIG. 4 shows an example of the configuration of the connecting member 11.
Reference numeral 12 denotes a bracket protruding from the lower surface of the arch rib 9 at both ends, 13 a connecting fitting that fits with the bracket 12, and 14
15 is a connecting pin, 15 is a beam integrated with the connecting fitting 13, 16
17 is a screw type cable length adjusting device, and 18 is a pulley for the connecting cable 11.

Further, 19 is a rope for temporarily connecting the abutment 3 and the beam 15, 20 is a pulley thereof, and 21 and 22 are connecting fittings.

At the initial stage of this diagonal suspension method, the tension of the connecting member 11 may be small because the horizontal force due to the assembled arch ribs 9 is small, but the arch ribs 9 can be assembled sequentially from both the left and right banks toward the center of the bridge. As the cable 11 is extended, the horizontal force also increases, so the cable length adjustment device 17 is used to tension the cable 11 each time.

Then, as shown in FIG. 1, when the last arch rib 9 is transported to a predetermined position by the cable carrier 8 and the assembly of the entire arch is completed, the connecting member 11 is adjusted and the diagonal suspension rope 10 is released. .

Next, as shown in FIG.
After the construction of all the lower chord members 23 is completed, the connecting member 11 is released, and the cable crane equipment, iron equipment, etc. are dismantled.

Since the construction method of the present invention is as described above, according to this construction method, most of the large horizontal force generated in the bridge support part in the conventional diagonal suspension construction method can be absorbed by the connecting member stretched between both ends of the bridge. This eliminates the need to make substructures such as bridge abutments unnecessarily exaggerated.

Therefore, the construction method of the present invention has the excellent effect of shortening the construction period and greatly reducing construction costs.

As an example, the bridge shown in Figure 5 has a vertical dead load reaction force of 97.
0t, and the total steel weight is 640t. However, according to the conventional diagonal suspension method, the horizontal reaction force H at the support portion C of the arch 5b in the state shown in Fig. 5f is 150t, and in Fig. 5g, the total steel weight is 640t. =2
44t, and H=524t in FIG. 5h.

On the other hand, the designed horizontal force in the axial direction of this bridge during an earthquake is 290 t on the fixed side of the bridge, and 145 t on the movable side.

Therefore, the completed structure of this bridge only needs to have the capacity to withstand the horizontal force at the time of the earthquake described above, but since the maximum horizontal force at the time of erection using the conventional diagonal suspension method is 5241, the lower structure must be able to withstand that much more. This required extra strength, which in turn increased construction costs.

However, according to the construction method of the present invention, most of the maximum horizontal force during construction can be canceled out by balancing the left and right sides, so the construction cost for lower structures such as bridge abutments and the like can be significantly reduced.

Incidentally, the estimated construction cost for constructing the bridge using the conventional direct suspension method is 170,000 yen/t, whereas the cost for the construction method of the present invention is 140,000 yen/t.

Therefore, the construction method of the present invention is extremely useful.

[Brief explanation of the drawing]

Figure 1 is an elevation view showing the state of construction of an arch bridge by the construction method of the present invention, Figure 2 is its plan view, Figure 3 is an elevation view showing the process after Figure 1, and Figure 4a is A partial elevation view showing an example of the structure of the connecting member, FIG. 5B is a plan view thereof, and FIGS. 1...river, 2...both banks, 3...
・Abutment, 4... Steel tower, 5... Back rope,
6... Anchor block, 7... Crane cable, 8... Crane carrier, 9...
... Arch rib, 10 ... Oblique sling, 11
...Connecting member, 17...Cable length adjustment device, 23...Lower chord member, 24...
Hanging material.

Claims (1)

[Claims] 1. When constructing an arch-type bridge using the diagonal suspension method, in the initial stage, both ends of the diagonally suspended arch are connected via a temporary connecting member whose tension can be adjusted, and as the arch ribs extend. An arch-type bridge characterized in that by increasing the tension of the connecting member, the horizontal component force caused by the diagonal suspension method is canceled out, so that only unbalanced horizontal force acts on the lower structure of the bridge support part. construction method.