JPH053487B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for constructing a multi-span arch bridge in which arch ribs are formed continuously between many piers.

[Conventional technology]

Recently, in bridge pier structures such as roads and railways, deterioration of concrete slabs constructed on the piers,
Damage is becoming a major problem. Deterioration and damage to concrete slabs is due to the material characteristics of concrete that is strong in compression but weak in tension.Dry shrinkage and repeated moving concentrated loads cause cracks, and water that enters through these cracks promotes rusting and expansion of reinforcing bars. It is believed that the concrete is peeling off and the reinforced concrete is deteriorating further.

Therefore, in order to deal with such deterioration of concrete, bridge types that match the characteristics of concrete have been studied, and concrete arch bridges have been attracting attention. This arch bridge is an excellent structural type for a concrete structure because it becomes a compressed member throughout its cross section when a dead load is applied.This type of bridge prevents deterioration of the concrete and greatly improves durability. That is true.

In constructing a multi-span arch bridge, after constructing abutments on both banks and erecting piers between them, arch concrete is constructed in sequence between the abutment piers and each pier. As shown in Fig. 4, the upper ends of the abutments 1 and piers 2, which are the fulcrums of the arch concrete 3, are exposed to horizontal force that tries to push them outward due to the large weight P of the arch concrete 3. P′ will work. Therefore, there will be no problem with the abutment 1, but the pier 2 will be deformed outward as shown by the dotted line in the figure during the construction stage, and the arch concrete 3 will also be deformed outward as shown by the dotted line in the figure. It will be transformed like this. If such deformation is large, not only will the load capacity of both the arch concrete 3 and the pier 2 no longer comply with the design value, but the spacing between the piers to be constructed next will be narrowed, and the construction of the arch concrete 3 will be will also be affected.

By the way, it is economically necessary for the pier 2 supporting the arch concrete 3 to be formed as slender as possible to withstand the load when used as an arch bridge, and especially when the height of the pier is large, the pier The thickness of the pipe will significantly affect the total construction cost.
However, in order to prevent the above-mentioned deformation, the piers must be made thicker than necessary.

In recent years, a review of arch bridges has led to the construction of concrete arch bridges, but as an actual example, the upper end of pier 2 is deformed by 20 to 40 mm outward due to the construction of concrete arch 3. I found out that there are some cases. It is also said that it is necessary to reduce this amount of deformation to less than half, which would be uneconomical as it would be necessary to erect piers that are thicker than necessary.

[Problem that the invention seeks to solve]

When constructing a multi-span arch bridge, it is important to minimize undesirable stress and deformation on the piers by constructing arch concrete in some of the spans, and to reduce the residual stress that remains after construction. This is an important technical issue because it will be possible to make the thickness of the bridge close to the minimum necessary to withstand the load of a bridge.

One possible way to solve this problem is to pour concrete across all spans at the same time. However, although this is possible for arch bridges with 2 to 3 spans, it is economically impossible to simultaneously pour concrete for bridges with more spans, so they are usually constructed in sections.

The present invention was made to solve the technical problem of split construction, and allows construction of arch concrete with piers that are as slender as possible.
The purpose of the present invention is to provide a new construction method for multi-span arch bridges that can be carried out with almost no deformation of the piers and arch concrete.

[Means for solving problems]

Figures 1 and 2 show embodiments of the configuration of the present invention.
To explain with reference to the drawings, the present invention, when constructing arch concrete between a large number of rows of piers, embeds an anchor material in the upper end of the abutment and each pier, and the bridge abutment or A tension rod was stretched between the upper ends of the piers via the anchor material, and after the arch formwork was installed, concrete was poured, and after the formwork was removed, tension on the piers became unnecessary. The feature is that the tension rods are removed at certain times.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2, which show embodiments.

In the figure, 1 is an abutment constructed on the other board A at one end of the arch bridge, and 2 is an abutment erected from this abutment 1 at a predetermined interval.
A plurality of anchor materials 4, 4 are buried at intervals in the width direction of the arch bridge within their upper ends, and the tip portions of each protrude from the concrete, and connecting means 4a such as screws or hooks are provided at the protruding portions. ing.

The arch concrete 3, 3, etc. to be constructed between the abutment 1 and the pier 2, and between the piers 2, 2, are first constructed over the abutment 1 and the next pier 2, and then built in order. Construction will proceed between the bridge piers 2 and 2, and first, the arch formwork 5 will be installed between the bridge abutment 1 and the bridge pier 2. As shown in FIG.
It is common to construct a bridge and then erect an arch-shaped formwork on top of it to support it. Furthermore, as it is known that conventional formwork is extremely troublesome to assemble and remove, and has poor construction efficiency, mobile formwork has been adopted in place of this formwork. Sometimes I do.

After the arch formwork 5 is installed, the anchor materials 4 of the abutment 1 and the anchor materials 4 of the abutment 2 are connected to each other via a connecting means by a tension rod 8 equipped with an expansion/contraction adjuster 8a, and the abutment 1 and Tension rod 8 between pier 2
Stretch it. Then, the arch concrete 3 is poured onto the arch formwork 5. As concrete is poured, an outward horizontal force P' acts on the upper end of the pier 2, as explained earlier, but the upper end of the pier 2
The outward deformation is suppressed by the drag force of the tension rods 8, 8... connected between the
It will remain upright. After the poured concrete has hardened, the arch formwork 5, arch truss 7, and shoring 6 are removed as shown in FIG. Due to their removal, the arch concrete 3 will receive an even larger outward horizontal force P ₁ acting on the upper end of the pier 2 due to its own size and weight P. Also against P', the outward deformation of the pier 2 is prevented by the drag force of the tension rod 8. Note that the tension rod will elongate under load, but if this elongation becomes a problem, the tension can be increased by operating the expansion/contraction adjuster 8a.

After completing the construction of the arch concrete 3 between the abutment 1 and the pier 2 in this way, the arch concrete 3 between the piers 2 and 2, which is the next span, is completed.
The construction is carried out in the same manner as described above, by installing the formwork 5 and tensioning the tension rods 8, pouring concrete, and removing the formwork. Then, concrete arches 3, 3, etc. between each pier are successively constructed.

Therefore, the removal of the tension rod 8 installed between the piers is as follows:
The horizontal force P ₁ exerted on the pier 2 after constructing the arch concrete 3 by the weight of the arch concrete 3
This should be done when there is no longer any risk of deformation, or when the amount of deformation is tolerable. Normally, when the construction of the arch concrete 3 has completed three spans, the amount of deformation at the upper end of the pier 2 in the first span will be in a state where there is no practical problem. However, if greater safety is desired, it is better to tension all the tension rods 8, 8, . . . until the construction of the arch concrete 3 in the front span is completed. Note that it is usually not necessary to install tension rods between the pier and the abutment, which is the final span.

〔Effect of the invention〕

As explained above, the method for constructing arch concrete according to the present invention is that when constructing arch concrete, anchor materials are buried in the upper part of the abutment and each pier, and the anchor materials are inserted between the piers. Since the arch concrete is constructed with the tension rods in tension, outward deformation of the piers caused by the construction of the arch concrete can be prevented, and deformation of the arch concrete and piers can be prevented.
This eliminates residual internal stress, making it possible to minimize the slenderness of the piers and arch concrete, resulting in significant savings in construction materials and construction costs. Moreover, the means to prevent the deformation of the piers are
It has many excellent effects, such as being extremely simple and easy to work with just by installing tension rods.

[Brief explanation of drawings]

Figures 1 to 3 are drawings illustrating embodiments of the present invention; Figure 1 is a side view showing a state in which a formwork is installed in the span and a tension rod is stretched; Figure 2 is a plan view of the same. ,
FIG. 3 is a side view showing the cast concrete with the formwork removed after hardening, and FIG. 4 is a side view illustrating problems in conventional arch concrete construction. 1... Bridge abutment, 2... Pier, 3... Arch concrete, 4... Anchor material, 5... Arch formwork,
6... Shoring, 7... Arch truss, 8... Tension rod.

Claims (1)

[Claims] 1. When constructing arch concrete between a large number of rows of piers, anchor materials are buried in the upper ends of the abutments and each pier, and the anchor materials are placed between the upper ends of the abutments or piers on which arch concrete is to be constructed. At the same time, tension rods are installed through the piers, concrete is poured after the arch formwork is installed, and after the formwork is removed, the tension rods are removed when the tension on the piers is no longer needed. Features: Arch concrete construction method for multi-span arch bridges.