JP7464914B2 - Precast floor slab installation jig and precast floor slab connection method - Google Patents

Description

The present invention relates to a precast concrete deck installation jig used when connecting two precast concrete decks and a method for connecting precast decks.

In Japan, social and economic infrastructure such as roads, railways, rivers, and ports were built intensively during the period of high economic growth. As a result, they have all been aging simultaneously in recent years, making their maintenance and renewal urgently necessary. In the superstructure of bridges over which roads and railways are built, if the deck is significantly damaged, it becomes necessary to replace it. In cases where the superstructure is a girder in which an RC deck is placed over a steel girder, a widely adopted measure is to replace the RC deck with a precast concrete deck of RC or PC structure (hereinafter simply referred to as a precast deck).

When replacing decks using precast decks, a construction method is used in which the existing decks are removed, the precast decks are lined up along the axis of the bridge, and then PC steel is inserted through the precast decks to introduce tension, thereby connecting the precast decks to each other (Patent Document 1).

On the other hand, instead of completely removing the existing deck, if one of the two lanes is opened to traffic while the other is partially removed and the deck is replaced, it is possible to avoid a complete road closure during the construction period (Patent Document 2).

Here, in the above-mentioned partial removal, if the precast deck is arranged in a direction perpendicular to the bridge axis, the insertion holes for the PC steel will open on both sides of the superstructure, which will pose the problem of having to construct separate scaffolding for the PC steel insertion work and the introduction of prestress via the PC steel. In addition, as the PC steel will be longer, depending on the size of the bridge, not only will it be difficult to insert it into the precast deck, but it will also lead to increased transportation and storage costs.

Therefore, the applicant developed a method of connecting precast decks in which, rather than passing the PC steel through two precast decks and then introducing tension into the PC steel, a connecting unit in which tension has already been introduced into a relatively short PC steel is placed on the two precast decks so that each end of the PC steel is fixed to each of the two precast decks, and then the tension of the PC steel is released to draw the two precast decks together (Patent Document 3).

This connection method eliminates the need to insert long PC steel members into two precast decks at the construction site, and eliminates the need for scaffolding for the insertion work. In addition, the tension of the PC steel members is pre-installed in a factory or other location and can be released at the construction site, so scaffolding for releasing the tension is also not required.

JP 2017-82496 A JP 2016-98490 A JP 2020-165130 A

However, when the tension of the PC steel that constitutes the connecting unit is released, because the precast deck is suspended over the steel girder, friction occurs between the underside of the precast deck and the top of the steel girder. This friction generates tensile stress on the outside of the anchoring end of the PC steel, causing cracks in the nearby concrete.

In addition, the above-mentioned frictional force was offset by part of the tension of the PC steel, which caused the problem that the planned compressive force could not be introduced at the connection point between the two precast decks.

In addition, even in conventional connection methods using long PC steel members, the tension introduced at the ends is partially offset by the frictional force generated between the precast deck and the steel girder, making it impossible to apply the required compressive force to the connection points between the precast decks. There is also concern that even in connection methods that do not use prestress, the above-mentioned frictional force may make it difficult to adjust the relative positions of the precast decks.

Incidentally, flat rollers or friction reduction means are sometimes placed between the precast deck and the steel girders, but even if such friction reduction means are placed, the frictional force is not reduced to zero, so the above-mentioned problems remain unresolved. Furthermore, when friction reduction means are placed, the precast deck becomes unstable in the horizontal direction, and there is a concern that the precast deck may slide due to unexpected horizontal loads.

The present invention was made in consideration of the above-mentioned circumstances, and aims to provide a precast deck installation jig and a precast deck connection method that can prevent cracks from occurring in the precast deck due to frictional forces generated between the underside of the precast deck and the top surface of the girder when a connecting unit is used.

The present invention also provides a precast deck installation jig and a precast deck connection method that can prevent the friction between the precast deck and the girder from impeding the precast deck connection work, even when using a connection method that uses long PC steel or a connection method that does not use prestress.

In order to achieve the above object, the precast deck installation jig of the present invention, as described in claim 1, comprises a support pillar that is loosely inserted into a through opening formed in the precast deck and has its base abutted against the support surface of the girder over which the precast deck is suspended, and a suspension mechanism that is connected to the support pillar and receives a reaction force from the girder via the support pillar, thereby enabling the precast deck to be suspended in a state separated from the girder, and the precast deck can be moved in the in-plane direction, with the movement limit being the clearance that expands between the peripheral surface of the support pillar and the inner peripheral surface of the through opening.

The precast deck installation jig of the present invention has a lifting mechanism that is composed of a lifting arm that extends to the side of the support and a lifting rod that is connected to the protruding portion of the lifting arm and has a tip that can be attached to the precast deck.

The precast deck installation jig according to the present invention has a pair of lifting arms extending in opposite directions from the support pillar, and the lifting rod is a pair of lifting rods connected to each of the lifting arms.

The precast deck installation jig of the present invention is also provided with a protrusion length adjustment mechanism that adjusts the length of the portion of the support that protrudes from the precast deck.

In addition, as described in claim 5, the precast floor slab connecting method according to the present invention is a precast floor slab connecting method for connecting a new precast floor slab, which is a trailing precast floor slab, to a preceding precast floor slab, which is a precast floor slab that has been previously placed,
The trailing precast deck is suspended from the support surface of the girder by applying a reaction force to the girder, and is spaced apart from the girder and is spanned adjacent to the preceding precast deck;
A connecting unit is installed across the preceding precast floor slab and the following precast floor slab so that each end of the PC steel material constituting the connecting unit is fixed near the opposing end portions of the preceding precast floor slab and the following precast floor slab,
By releasing the tension previously introduced into the PC steel material, the trailing precast deck is pulled toward the leading precast deck and connected to the leading precast deck;
The space between the trailing precast deck and the girder is filled with mortar and the strength of the mortar is developed before the tensile force for the suspension is released, or a temporary support material is placed in the space between the trailing precast deck and the girder and then the tensile force for the suspension is released and mortar is filled in the space.

In addition, as described in claim 6, the precast floor slab connecting method according to the present invention is a precast floor slab connecting method for connecting a new precast floor slab, which is a trailing precast floor slab, to a preceding precast floor slab, which is a precast floor slab that has been previously placed,
The trailing precast deck is suspended from the support surface of the girder by applying a reaction force to the girder, and is spaced apart from the girder and is spanned adjacent to the preceding precast deck;
PC steel members are inserted into the preceding precast floor slab and the following precast floor slab along their in-plane directions to introduce tension into the PC steel members;
The space between the trailing precast deck and the girder is filled with mortar and the strength of the mortar is developed before the tensile force for the suspension is released, or a temporary support material is placed in the space between the trailing precast deck and the girder and then the tensile force for the suspension is released and mortar is filled in the space.

In addition, as described in claim 7, the precast floor slab connecting method according to the present invention is a precast floor slab connecting method for connecting a new precast floor slab, which is a trailing precast floor slab, to a preceding precast floor slab, which is a precast floor slab that has been previously placed,
The trailing precast deck is suspended from the support surface of the girder by applying a reaction force to the girder, and is spaced apart from the girder and is spanned adjacent to the preceding precast deck;
The following precast floor slab is moved in an in-plane direction while maintaining the tensile force for the lifting, thereby adjusting the horizontal clearance with the preceding precast floor slab;
The trailing precast deck and the preceding precast deck are interconnected while maintaining the tension force for the lifting ,
The space between the trailing precast deck and the girder is filled with mortar and the strength of the mortar is developed before the tensile force for the suspension is released, or a temporary support material is placed in the space between the trailing precast deck and the girder and then the tensile force for the suspension is released and mortar is filled in the space.

[Precast floor slab installation jig]
In the precast deck installation jig of the present invention, the pillars are loosely inserted into the through openings formed in the precast deck, and the bases of the pillars are abutted against the supporting surface of the girder on which the precast deck is suspended.Therefore, the precast deck is suspended by the lifting mechanism in a state where it receives a reaction force from the girder via the pillars and is spaced apart from the girder, and the precast deck can move in the in-plane direction, up to the limit of the movement width caused by the clearance between the peripheral surface of the pillars and the inner surface of the through opening.

Therefore, when a precast deck placed first (hereinafter referred to as the precast deck) and a precast deck placed adjacent to it (hereinafter referred to as the trailing precast deck) are interconnected using connecting units straddling the precast deck and the trailing precast deck so that the ends of the precast steel are fixed near the opposing ends of the precast deck and the trailing precast deck, when the tension previously introduced into the precast steel is released, the tension is not hindered by the frictional force generated between the trailing precast deck and the girder, and is substantially entirely transmitted as a compressive force along the entire length of the precast steel to the surrounding concrete.

As a result, a sufficiently large compressive force acts on each of the opposing surfaces of the leading precast deck and the trailing precast deck, the trailing precast deck is securely connected to the leading precast deck, and there is no concern that part of the tension of the PC steel will generate tensile stress in the outer area of the anchoring end of the PC steel, so there is no risk of cracks occurring in the concrete extending into that outer area.

Even when long PC steel members are used for connection, there is no concern that the tension introduced into the PC steel members will be partially offset by the above-mentioned frictional force, so a sufficiently large compressive force acts on each opposing surface of the leading precast deck and the trailing precast deck, allowing for a secure connection between the two. Furthermore, even when connecting without using prestress, there is no risk that the above-mentioned frictional force will make it difficult to adjust the relative position with the leading precast deck, allowing for a more appropriate connection.

In addition, because the base of the support column abuts against the support surface of the girder, the load of the precast deck is transmitted to the base of the support column via the lifting mechanism, and a frictional force is generated between the support surface of the girder and the base of the support column depending on the magnitude of the frictional force. This frictional force serves to stably support the precast deck and the precast deck installation jig that suspends it as a whole in the in-plane direction of the precast deck.

The main feature of the precast deck installation jig of the present invention is that when two precast decks are connected using prestress, the precast deck can be moved freely in a direction perpendicular to the opposing surfaces in order to apply a sufficient compressive force to the opposing surfaces. However, as can be seen from the above description of the case where prestress is not used, the problem of the above-mentioned frictional force making it difficult to adjust the relative position with the preceding precast deck can be solved even in a direction parallel to the opposing surfaces. In that sense, whether or not prestress is used when connecting is not a premise of the present invention.

The clearance between the periphery of the support and the inner periphery of the through opening can be determined appropriately according to the amount of in-plane movement of the precast deck required for each connection method. If the connection method uses the connection unit, it can be determined based on the amount of contraction of the anchorage distance when the tension of the PC steel that makes up the connection unit is released. If the connection method uses long PC steel, it can be determined based on the amount of contraction of the trailing precast deck when tension is applied to the PC steel. If the connection method does not use prestress, it can be determined based on the amount of position adjustment required when constructing the joint with the preceding precast deck.

The specific configuration for enabling the in-plane movement of the precast deck is arbitrary, as long as the relative horizontal movement required for the trailing precast deck when it is connected to the preceding precast deck is possible without substantially impeding the connection operation. For example,
(a) Configuring the support columns, the suspension mechanism, or at least a part of the connecting member connecting them to each other so that they can be elastically deformed in the direction of the relative horizontal movement.
(b) Providing a sliding mechanism so that at least a part of the lifting mechanism can move horizontally in the same direction.
(c) It is possible to provide a swinging mechanism in the lifting mechanism so that the precast deck can swing in the same direction.

(a) can be configured, for example, so that the support pillars, the lifting mechanism, or part of the connecting material that interconnects them is made of steel material with a rectangular cross section and is positioned so that its strong axis coincides with the direction of the relative horizontal movement described above, and (b) can be configured as a sliding mechanism that is similar to a traveling rail that suspends a hoist crane so that it can travel freely.

The lifting mechanism can be configured with a lifting arm extending to the side of the support and a lifting rod connected to the protruding portion of the lifting arm and having its tip attached to the precast deck. In this configuration, if the lifting rod is structurally joined to the lifting arm and the precast deck as a pin, the precast deck can swing freely by the lifting mechanism, so this corresponds to the above-mentioned configuration (c), and if the lifting rod is rigidly joined to the lifting arm or the precast deck, this corresponds to the above-mentioned configuration (a).

In either case, in such a configuration, it is preferable that the hanging arm is a pair of hanging arms extending in opposite directions across the axis of the support pillar, and the hanging rod is a pair of hanging rods connected to each of the hanging arms.

Because the precast deck needs to be spaced apart from the girder, the columns need to be loosely inserted into the through openings formed in the precast deck and the bases of the columns need to protrude from the precast deck. However, if a protrusion length adjustment mechanism is provided to adjust the length of the protruding parts, the manufacturing precision of the columns can be relaxed, making on-site response easier.

If the extension length adjustment mechanism is provided on the support or the suspension mechanism, for example, it can be configured to be extendable and retractable to allow the overall length to be variable; if it is provided at the connection between the support and the suspension mechanism, it can be configured to connect them by screwing and then adjust the depth and position of the screwing; if it is provided on the deck side end of the suspension mechanism, it can be configured to be screwed into a female thread provided in the precast deck so that the depth can be adjusted.

[How to connect precast floor slabs]
(1) Connection method using a connecting unit In the precast deck connection method of the present invention, to connect a trailing precast deck to a leading precast deck using a connecting unit, first, the trailing precast deck is suspended by applying a reaction force from the support surface of the girder, and is then hung on the girder so that it is spaced apart from the girder and adjacent to the leading precast deck.

Next, the connecting unit is installed across the leading precast deck and the trailing precast deck so that each end of the PC steel member that constitutes the connecting unit is fixed near the opposing ends of the leading precast deck and the trailing precast deck. A typical example of a configuration is where a joint is provided between the leading precast deck and the trailing precast deck, sandwiched between their opposing surfaces. It is desirable for the constituent material of the joint (such as concrete) to be continuously integrated with the concrete to which each end of the PC steel member is fixed.

Next, the tension previously applied to the PC steel is released.

In this way, the tension is not offset in any way by the frictional force that occurs between the trailing precast deck and the girder, and essentially all of it is transmitted as a compressive force to the surrounding concrete along the entire length of the PC steel.

As a result, a sufficiently large compressive force acts on the opposing surfaces of the leading precast deck and the trailing precast deck, and the trailing precast deck is securely connected to the leading precast deck.

In addition, at this time, there is no concern that part of the tension of the PC steel will generate tensile stress in the outer region of the fixed end of the PC steel as a reaction force against the above-mentioned friction force, so there is no risk of cracks occurring in the concrete extending into that outer region.

Once the trailing precast deck is connected to the leading precast deck, the space between the trailing precast deck and the girder is filled with mortar, and once the strength of the mortar has been exerted, the tensile force for lifting is released.

Alternatively, a temporary support material may be placed in the space between the trailing precast deck and the girder, and then the tensile force for the suspension may be released and mortar may be filled in the space.

(2) Connection method using long PC steel members In the precast deck connection method of the present invention, to connect the trailing precast deck to the leading precast deck using long PC steel members, first, the trailing precast deck is suspended by applying a reaction force from the support surface of the girder, and is then hung on the girder so that it is spaced apart from the girder and adjacent to the leading precast deck.

Next, PC steel is inserted into the leading precast deck and the trailing precast deck along their in-plane direction, and tension is then applied to the PC steel. Note that a typical example is a configuration in which, prior to the process of applying tension to the PC steel, a joint made of concrete or other structural material is provided in advance between the leading precast deck and the trailing precast deck, sandwiched between their opposing surfaces.

In this way, the tension is transmitted to the trailing precast deck without being offset in any way by the frictional force that occurs between the trailing precast deck and the girder.

As a result, a sufficiently large compressive force acts on the opposing surfaces of the leading precast deck and the trailing precast deck, and the trailing precast deck is securely connected to the leading precast deck.

Once the trailing precast deck is connected to the leading precast deck, the space between the trailing precast deck and the girder is filled with mortar, and the tensile force for lifting is released once the strength of the mortar has been exerted, just as in the connection method using a connecting unit.

Alternatively, a temporary support material may be placed in the space between the trailing precast deck and the girder, and then the tensile force for the suspension may be released and mortar may be filled in the space.

(3) Connection method without prestress In the precast deck connection method of the present invention, to connect the trailing precast deck to the leading precast deck without using prestress, first, the trailing precast deck is suspended by applying a reaction force from the support surface of the girder, and is then hung on the girder so that it is spaced apart from the girder and adjacent to the leading precast deck.

Next, the trailing precast deck is moved in-plane to adjust the horizontal clearance with the leading precast deck.

Here, because no friction occurs between the trailing precast deck and the girder over which it is suspended, the trailing precast deck can be freely moved in the in-plane direction, making it easy to adjust the horizontal clearance with the leading precast deck.

Once the horizontal clearance between the trailing precast deck and the leading precast deck has been adjusted, reinforcement bars are placed in the horizontal clearance as necessary, and concrete is then poured into the horizontal clearance to interconnect the trailing precast deck and the leading precast deck.

Once the trailing precast deck is connected to the leading precast deck, the space between the trailing precast deck and the girder is filled with mortar, and the tensile force for lifting is released once the strength of the mortar has been exerted, just as in the connection method using a connecting unit.

Alternatively, a temporary support material may be placed in the space between the trailing precast deck and the girder, and then the tensile force for the suspension may be released and mortar may be filled in the space.

FIG. 1 is an overall perspective view of a precast deck installation jig 1 according to this embodiment. Front view of precast deck installation jig 1. FIG. 2 is an explanatory diagram showing the operation of the precast deck installation jig 1. A diagram showing the procedure for connecting a precast deck 2 to a preceding precast deck using a precast deck installation jig 1. Continuing the steps of the connection process. Continuing on, this figure shows the connection procedure, where (a) is a plan view and (b) is a cross-sectional view taken along line A-A. FIG. 13 is a diagram further illustrating the connection procedure, and also shows the load balance. FIG. 13 is a diagram showing the load balance in a conventional connection method. Continuing the steps of the connection process. FIG. 11 is a front view showing a precast deck installation jig according to a modified example. FIG. 11 is a front view showing a precast deck installation jig according to another modified example. FIG. 11 is a front view showing a precast deck installation jig according to another modified example. FIG. 11 is a front view showing a precast deck installation jig according to another modified example. FIG. 11 is a front view showing a precast deck installation jig according to another modified example. FIG. 11 is a front view showing a precast deck installation jig according to another modified example. This is a diagram showing how precast deck slabs are connected, where (a) is a detailed plan view and (b) is a detailed cross-sectional view along line B-B.

Below, an embodiment of the precast deck installation jig and precast deck connection method according to the present invention will be described with reference to the attached drawings.

[Precast floor slab installation jig]
As shown in Figures 1 and 2, the precast deck installation jig 1 of this embodiment is used for connecting a previously installed precast deck (not shown) to a subsequently installed precast deck 2, and is equipped with four support bolts 5 as pillars and a lifting mechanism 7 connected to the support bolts. The support bolts 5 are arranged to penetrate the precast deck 2, and one end (the lower end in Figures 1 and 2; hereinafter referred to as the bolt leg) is abutted as a base 6 against the support surface 4 of the girder 3 on which the precast deck is spanned. The lifting mechanism 7 is capable of suspending the precast deck 2 by receiving a reaction force from the girder 3 via the four support bolts 5.

The four support bolts 5 each have a nut 8 screwed onto the other end (the upper end in Figs. 1 and 2, hereafter referred to as the bolt top), and the bolt top is inserted into a bolt insertion hole 10 drilled in the top plate 9 with the nut abutting against it, and the load from the above-mentioned lifting mechanism 7 is supported via the top plate 9 and a connecting member 11 extending near its center.

The above configuration using the nut 8 allows the length of the portion of the support bolt 5 that protrudes from the precast deck 2, in other words the distance Δh (Figure 2) of the precast deck 2 from the support surface 4 of the girder 3, to be adjusted by changing the screwing position, and functions as the protrusion length adjustment mechanism of the present invention.

The protrusion length (gap dimension Δh) can be determined appropriately taking into consideration the ease of filling the gap with grout and the load transmission performance of the filled grout.

The above-mentioned protrusion length adjustment mechanism using the nut 8 and support bolt 5 also functions as a conventional level adjustment screw that adjusts the installation level of the precast deck 2, and in that sense, the protrusion length is appropriately determined while taking into account the desired installation level.

As shown in Figures 1 and 2, the four support bolts 5 are arranged to face the top plate 9 and are inserted into bolt insertion holes 14 in the bottom plate 13 connected to the top plate via the side plates 12, 12, and are configured to be held in a generally vertical position relative to the top plate 9.

Here, the four support bolts 5 are inserted into hollow tubes 15 embedded in the precast deck 2, and the hollow tubes function as through openings for allowing the support bolts 5 to pass loosely through the precast deck 2.

The lifting mechanism 7 is composed of a pair of lifting arms 21, 21 connected to the connecting material 11 on the side opposite the top plate 9 and extending in opposite directions across the axis of the connecting material, and a pair of PC steel members 22, 22 as lifting rods connected to the protruding parts of the lifting arms. The male threaded portions 24, 24 at the ends of the PC steel members can be screwed into the female threads 23, 23 embedded in the precast deck 2.

In this embodiment, the pair of lifting arms 21, 21 are made from a single square steel pipe, as can be seen in each figure.

Each PC steel member 22 is inserted into a bolt hole formed in the suspension arm 21 and connected to the suspension arm by screwing in a nut 25.

The suspension mechanism 7 is configured to receive a reaction force from the girder 3 via the four support bolts 5 as described above, so that the precast deck 2 can be suspended at a distance Δh from the girder 3. As shown in FIG. 3, the PC steel 22 that constitutes the suspension mechanism 7 elastically deforms, so that the precast deck 2 can move in the in-plane direction as shown in FIG. 3(a), with the movement limit being the clearance δd that expands between the circumferential surface of the support bolt 5 and the inner circumferential surface of the hollow tube 15 (FIG. 3(b)).

Note that Figure 3(a) shows how the PC steel 22 that constitutes the suspension mechanism 7 deforms as the precast deck 2 moves in the in-plane direction, with the degree of deformation exaggerated for ease of understanding the invention. In reality, the clearance δd is the limit of the movement range, as shown in Figure 3(b).

Clearance δd can be set appropriately depending on how much in-plane movement of the trailing precast deck is desired relative to the leading precast deck when connecting the trailing precast deck to the leading precast deck.

For example, when two precast decks are connected by applying prestress to their opposing ends (vertical joints), the compressive strain generated in the concrete is calculated as follows, assuming that the stress to be applied to the vertical joint is 5 N/ ^mm2 and the Young's modulus of concrete is 30 kN/ ^mm2 :
Compressive strain = 5/30000
= 170μ
Therefore, if the prestressing distance (the distance between the anchor plates) is 4.5 m, the amount of shrinkage of the concrete is
Concrete shrinkage = 4.5 x 170/1000
= 0.77 mm ≒ 0.8 mm
It can be seen that the clearance δd required to prevent tensile strain from occurring in the concrete is 0.8 mm when the advance precast deck is fixed.

In this case, if the length of the PC steel 22 (height H from the top surface of the precast deck 2 to the bottom surface of the lifting arm 21) is, for example, 2 m, the force (restoring force) that causes the precast deck 2 to return to its original position is expressed as follows, assuming that the weight of the precast deck 2 is W:
Restoring force = W x 0.8/2000
= 0.0004 W
However, this is negligible compared to the magnitude of the prestress introduced, and it is understood that this does not impede the connection work.

[Method of connecting precast floor slabs using precast floor slab installation jig 1]
Figures 4 to 9 show an example of the procedure for connecting a trailing precast deck 2 to a leading precast deck using a precast deck installation jig 1, using a connecting unit.

As shown in these figures, to connect the precast deck 2 to the preceding precast deck, first, as shown in Figure 4(a), the manufactured precast deck 2 is installed horizontally in a factory or the like. At this time, the bottom surface of the precast deck 2 is appropriately raised above the floor surface 43 using end thickening material 41 so that the base 6 of the support bolt 5 can protrude from the bottom surface of the precast deck 2.

Next, the precast deck installation jig 1 is temporarily placed on the precast deck 2 by sandwiching the spacer 42 between the bottom plate 13 and the precast deck 2. In this state, the upper ends of the PC steel members 22, 22 are inserted into the bolt insertion holes formed in the lifting arms 21, 21, and the nuts 25 are screwed in, while the male threaded portions 24, 24 at the lower ends (tips) are screwed into the female threads 23, 23 embedded in the precast deck 2.

As already mentioned, when the prestress force for connection is applied to the opposing ends of the two precast decks, the screw-in position of the nut 25 is appropriately adjusted so that the length of the PC steel 22 (height H from the top surface of the precast deck 2 to the bottom surface of the lifting arm 21) is a length that can sufficiently reduce the restoring force of the precast deck 2. In addition, to enable the length of the PC steel 22 to be adjusted, the length of the connecting material 11 is also appropriately determined, or it is configured to be extendable so that its length can be changed.

At the same time as or before or after the above work, the support bolt 5 is inserted through the bolt insertion hole 10 in the top plate 9 and the bolt insertion hole 14 in the bottom plate 13, and the nut 8 is screwed onto the support bolt.

When adjusting the screwing position of the nut 8, the protrusion amount Δh' of the base 6 of the support bolt 5 from the underside of the precast deck 2 is adjusted to the following value when the upper surface of the nut is in contact with the lower surface of the top plate 9:
Δh′=Δh+Δp
Δh: Distance dimension of the precast deck 2 from the support surface 4 of the girder 3 Δp: The amount of elastic deformation of the PC steel when the weight of the precast deck 2 acts on the PC steel 22. This is because when the precast deck 2 is placed on the girder 3, the weight of the precast deck acts on the PC steel 22, stretching it, and the base 6 of the support bolt 5 recedes toward the precast deck 2 by that amount.

Once the precast deck installation jig 1 has been installed on the precast deck 2, it is transported to the connection work site and lowered onto the girder 3 as shown in Figure 4(b).

Figure 5 shows how the trailing precast slab 2 is lowered adjacent to the leading precast slab 51. In this embodiment, two precast slab installation jigs 1 are installed on the precast slab 2, and the precast slab is then spanned across girders 3, 3, with the bases 6 of the support bolts 5 that make up the precast slab installation jigs 1 abutting against the support surfaces 4 of the girders.

In this way, the support bolts 5 of the precast deck installation jig 1 are loosely inserted into the hollow tubes 15, which are through openings formed in the precast deck 2, and the bases 6 of the support bolts 5 are abutted against the support surface 4 of the girder 3 on which the precast deck is suspended. As explained in Figures 2 and 3, the precast deck 2 is suspended by the suspension mechanism 7 in a state where it receives a reaction force from the girder 3 via the support bolts 5 and is spaced apart from the girder 3 by Δh, and can move in the in-plane direction up to the limit of the movement caused by the clearance δd that expands between the circumferential surface of the support bolts 5 and the inner surface of the hollow tubes 15.

In this way, the precast deck 2, which is the trailing precast deck, is placed across the girder so as to be spaced apart from the girders 3, 3 and adjacent to the precast deck 51, which is the leading precast deck. Then, as shown in Figure 6, a connecting unit 61 is placed so as to straddle the opposing ends of the precast deck 51 and the precast deck 2.

The connecting unit 61 has an anchor plate attached near each end of the PC steel rod, and tension has been applied to the PC steel rod in advance. By releasing the tension (releasing the compressive force that acts as a reaction force to maintain the tension), a compressive force can be applied to the surrounding concrete via the anchor plate. However, the specific configuration can be appropriately selected from known technologies, for example, and therefore a detailed explanation will be omitted here.

As shown in the figure, the opposing ends of the precast deck 51 and the precast deck 2 are each provided with cutouts 62a, 62b that open to the opposing ends, so when placing the connecting unit 61, it is positioned so that one of the anchor plates that make up the connecting unit 61 is placed in the cutout 62a of the precast deck 51, and the other anchor plate is placed in the cutout 62b of the precast deck 2.

Once the connecting unit 61 has been placed, concrete is then poured into the notches 62a and 62b so that the connecting unit is embedded and integrated into the notches.

When pouring concrete, the area around the release mechanism is left as a work space without concrete being poured so that the tension of the PC steel rods that make up the connecting unit 61 can be released after the strength is developed, and concrete can be poured into the work space after the tension is released as necessary.

Next, after the concrete poured into the notches 62a and 62b has developed its strength, the tension of the PC steel rods that make up the connecting unit 61 is released.

In this way, the tension acts in a direction that draws the precast deck 2 toward the precast deck 51, as shown in FIG. 7. However, the precast deck is suspended by the precast deck installation jig 1 in a state where it receives a reaction force from the girder 3 and is spaced from the girder 3 by Δh as described above, and is in a state where it can move in the in-plane direction up to the movement width due to the clearance δd. Therefore, the precast deck 2 moves toward the precast deck 51 without being hindered by the frictional force generated between the precast deck 2 and the girder 3, and almost all of the tension introduced into the PC steel rod that constitutes the connecting unit 61 is transmitted as a compressive force along the entire length of the PC steel rod, including the concrete in the notches 62a and 62b, to the concrete area near the opposing ends of the precast deck 2 and the precast deck 51.

Figure 7(b) shows how the release of tension in the connecting unit 61 balances the tension in the PC steel bar with the compressive force of the concrete extending between the anchor plates, and shows that no tensile force is transmitted to the concrete area extending outside the anchor plates.

On the other hand, in the case of the conventional method of connecting the precast deck 2 to the girder 3, 3 without using the precast deck installation jig 1, as shown in FIG. 8(a), when the tension of the connecting unit 61 is released, a frictional force ΔP occurs as a reaction force between the precast deck 2 and the girder 3, and between the precast deck 51 and the girder 3, respectively. Therefore, the tension of the PC steel bar that constitutes the connecting unit 61 and the compressive force of the concrete spreading between the anchor plate are balanced by a load (P-ΔP) with the frictional force ΔP reduced, as shown in FIG. 8(b). Between the anchor plate that constitutes the connecting unit 61 and the girder 3 (outside the anchor end area), a tensile force is generated to balance the frictional force ΔP, as shown in FIG. 8(c), and cracks occur in the concrete area 81.

When the work of connecting the precast deck 2 and the precast deck 51 with the connecting unit 61 is completed, as shown in Figure 9 (a), mortar 91 is filled between the girder 3 and the precast deck 2. After the mortar has developed its strength, the nut 25 is loosened to unload the PC steel 22, the male threaded portion 24 at its lower end is removed from the female threaded portion 23, and the support bolt 5 is cut at the top surface of the precast deck 2. As shown in Figure 9 (b), the precast deck installation jig 1 is removed with the bolt portion 5b remaining on the precast deck 2. If masking tape is wrapped around the support bolt 5, the periphery of the support bolt is cut off from the mortar 91, so that the support bolt 5 can be removed without cutting it.

The removed precast deck installation jig 1 can be reused appropriately for the next connection work.

[Effects of the embodiment]
As described above, according to the precast deck installation jig 1 of this embodiment, the support bolt 5 is loosely inserted into the hollow tube 15, which is a through opening formed in the precast deck 2, and the base 6 of the support bolt 5 is abutted against the support surface 4 of the girder 3 on which the precast deck is spanned. Therefore, the precast deck 2 is suspended by the suspension mechanism 7 in a state in which it receives a reaction force from the girder 3 via the support bolt 5 and is spaced apart from the girder 3 by Δh, and can move in the in-plane direction up to the movement width caused by the clearance δd that expands between the circumferential surface of the support bolt 5 and the inner surface of the hollow tube 15. Therefore, a sufficiently large compressive force acts on the opposing surfaces of the precast deck 51 and the precast deck 2.

As a result, the precast deck 2 is securely connected to the precast deck 51, and no frictional force is generated between the precast deck 2 and the girder 3, so there is no risk of cracks occurring in the concrete area 81 between the anchor plate that constitutes the connecting unit 61 and the girder 3, as occurs with conventional connecting methods.

In addition, according to the precast deck installation jig 1 of this embodiment, the base 6 of the support bolt 5 abuts against the support surface 4 of the girder 3, so the load of the precast deck 2 is transmitted to the base 6 via the suspension mechanism 7, and a frictional force is generated between the support surface 4 of the girder 3 and the load depending on the magnitude of the load. This frictional force serves to stably support the precast deck 2 and the precast deck installation jig 1 that suspends it as a whole in the in-plane direction of the precast deck 2.

Therefore, there is no risk of the precast deck becoming unstable in its in-plane direction, as occurs with conventional connection methods in which friction reduction means are interposed between the precast deck and the girder.

In addition, according to the precast deck installation jig 1 of this embodiment, the axial rigidity of the PC steel material 22 can be kept low, so that even if traffic vibrations occur in the precast deck 51, which is an existing precast deck, the precast deck 2 will vibrate in tandem with the precast deck 51, thus eliminating concerns about poor adhesion between the concrete poured in the cutouts 62a, 62b and the reinforcing bars that reinforce it.

[Modifications related to precast deck installation jigs]
In this embodiment, the PC steel 22 that constitutes the lifting mechanism 7 is rigidly connected to the lifting arm 21 and the precast deck 2, and the PC steel elastically deforms to move the precast deck 2 in an in-plane direction. However, if the connections between the PC steel 22 and the lifting arm 21 and the precast deck 2 can be considered to be pin joints in structure, the precast deck 2 can also be moved in an in-plane direction by a swinging mechanism with the lifting arm 21 as a fulcrum, rather than by elastic deformation of the PC steel 22.

The specific configuration for allowing the precast deck to move in the in-plane direction is arbitrary, so long as the relative horizontal movement required for the trailing precast deck when it is connected to the preceding precast deck is possible without substantially impeding the connecting operation. For example, as shown in Figure 10, this may be achieved by elastic deformation of the connecting material 11.

In addition, in this embodiment, the nuts 8 are screwed onto the support bolts 5, and the tops of the bolts are inserted into the bolt insertion holes 10 drilled in the top plate 9 with the nuts abutting against each other. By changing the screwing position of the nuts, the length of the support bolts 5 protruding from the precast deck 2 (the distance Δh of the precast deck 2 from the support surface 4 of the girder 3) can be adjusted. However, the protrusion length adjustment mechanism of the present invention is not limited to this configuration. For example, as shown in FIG. 11, the length of the protruding part from the precast deck 2 can be changed by changing the screwing position of the nuts 25 screwed into the PC steel material 22 or the screwing depth of the male thread 24 into the female thread 23.

In this configuration, instead of using nuts 8, as shown in the figure, four support bolts 112 are attached to a base plate 111 as pillars that penetrate the precast deck 2 and whose lower ends abut the support surface 4 of the girder 3 as a base 6, and a connecting member 11 is extended on the opposite side of the base plate and its tip is connected to the hanging arms 21, 21.

The protrusion length adjustment mechanism of the present invention is not an essential component, and if there is no need to adjust the length of the portion of the support bolt 5 that protrudes from the precast deck 2, it may be omitted.

In addition, in this embodiment, when the support bolts 5 are loosely inserted into the precast deck 2, each support bolt 5 is individually inserted into the hollow tube 15 provided in the precast deck 2. However, any structure can be used for the through openings provided in the precast deck. As shown in FIG. 12, for example, one opening 131 may be provided so as to have a rectangular shape in plan view, and four support bolts 5 may be inserted through the opening 121.

In addition, in this embodiment, the suspension mechanism 7 is configured so that the PC steel members 22, 22 are parallel to the connection direction with the preceding precast deck (the left-right direction in Figure 2), but the suspension mechanism of the present invention can be arranged at any angle around an axis that is vertical in the installed position (an axis that extends vertically in Figure 2). For example, as shown in Figure 13, it may be configured by rotating 90 degrees around the vertical axis from the configuration of the embodiment shown in Figures 1 and 2.

In addition, in the modified example of Figure 13, instead of placing the precast deck installation jig 1 above the girder 3, it is possible to adopt the configuration of Figure 14 in which brackets 141 are extended on both sides of the girder 3, and the precast deck installation jig 1 is placed above each bracket as a new girder, or the configuration of Figure 15 in which the top plate and bottom plate are made into a shared top plate 9' and a shared bottom plate 13' in the same configuration, and the lifting mechanism 7 is combined into one.

In addition, in this embodiment, after the connection work between the precast deck 2 and the precast deck 51 by the connection unit 61 is completed, the mortar 91 is filled and the precast deck installation jig 1 is removed after waiting for the strength to develop. However, instead, if a spacer is sandwiched between the girder 3 and the precast deck 2 to temporarily support the precast deck 2 and the mortar 91 is filled in this state, it is possible to remove the precast deck installation jig 1 without waiting for the strength to develop in the mortar 91.

In addition, in this embodiment, the precast deck installation jig of the present invention has been described as an example of application to a connection method using a connection unit 61, but the precast deck installation jig of the present invention is not intended to be used in conjunction with the connection unit 61. Even when connecting using long PC steel members, there is no concern that the tension introduced into the PC steel members will be partially offset by the frictional force generated between the PC steel members and the girder, so that a sufficiently large compressive force acts on the surface facing the preceding precast deck, enabling a reliable connection to the preceding precast deck. Furthermore, even when connecting without using prestress, there is no risk that the above-mentioned frictional force will make it difficult to adjust the relative position with the preceding precast deck, allowing for a more appropriate connection.

[Modifications regarding precast floor slab connection method]
In addition, in this embodiment, the connecting method of precast decks according to the present invention (connecting method using a connecting unit) has been described using the precast deck installation jig of the present invention, but the connecting method of precast decks according to the present invention (connecting method using a connecting unit) can be achieved by suspending the trailing precast deck using a reaction force from the support surface of the girder, and suspending it across the girder so that it is spaced apart from the girder and adjacent to the leading precast deck, and it is not necessarily necessary to use the precast deck installation jig of the present invention.

In addition, the method of connecting precast decks according to the present invention is not limited to the connection method using a connecting unit, but can also be applied when connecting a trailing precast deck to a leading precast deck using long PC steel members.

In this case, the PC steel is inserted into the leading precast deck and the trailing precast deck along their in-plane directions, and tension is then introduced into the PC steel. At this time, the tension is not offset in any way by the frictional force generated between the trailing precast deck and the girder, and is transmitted as a compressive force to the concrete that constitutes the trailing precast deck. As a result, a sufficiently large compressive force acts on the opposing surfaces of the leading precast deck and the trailing precast deck, making it possible to securely connect the trailing precast deck to the leading precast deck.

In addition, in connection methods using long PC steel members, the above-mentioned clearance δd can be appropriately determined based on the amount of shrinkage of the trailing precast deck when tension is applied to the long PC steel members.

The precast deck connection method of the present invention can also be applied when connecting a trailing precast deck to a leading precast deck without using prestress.

In this case, the horizontal clearance with the leading precast deck is adjusted by moving the trailing precast deck in a plane direction. In this case, since there is no friction between the trailing precast deck and the girder over which it is suspended, the trailing precast deck can be freely moved in a plane direction, and the horizontal clearance with the leading precast deck can be easily adjusted.

In addition, in connection methods that do not use prestress, the above-mentioned clearance δd can be determined based on the amount of position adjustment required when constructing the joint with the preceding precast deck.

Although not specifically mentioned in this embodiment, a typical example is a procedure in which a joint is interposed between the precast deck 2 and the precast deck 51 when connecting the precast deck 2 to the precast deck 51 using the connecting unit 61.

In other words, when positioning the connecting unit 61 in Figure 6, as shown again in Figure 16, the precast deck 2 is positioned relative to the precast deck 51 so that the opposing surfaces 162a, 162b of the precast deck 2 and the precast deck 51 are spaced apart from each other, and the connecting unit is positioned so that the anchor plate 161a attached to one of the PC steel rods 163 constituting the connecting unit 61 is positioned within the cutout 62a of the precast deck 51, and the anchor plate 161b attached to the other is positioned within the cutout 62b of the precast deck 2.

Next, concrete is poured into the notches 62a and 62b, and in the space extending between the opposing surfaces 162a and 162b of the precast deck 2 and the precast deck 51, except for the operating work area 164 for operating the reaction force release mechanism 165 for releasing the tension previously introduced into the PC steel bar 163.

In this way, a tensile force transmission section 167a is provided in the cutout 62a in a form that is continuous and integrated with the precast deck 51, and an anchor plate 161a is embedded in the tensile force transmission section. Similarly, a tensile force transmission section 167b is provided in the cutout 62b in a form that is continuous and integrated with the precast deck 2, and an anchor plate 161b is embedded in the tensile force transmission section.

In addition, a joint 166 is provided in the space extending between the opposing surfaces 162a, 162b of the precast deck 2 and the precast deck 51, so as to be continuously and integrally connected to the precast decks 51, 2.

It is preferable to enhance the continuous integration between the precast slab 51 and the tensile force transmission part 167a by appropriately protruding the reinforcing bars (not shown) arranged in the precast slab 51 from the precast slab into the cutout 62a, and to enhance the continuous integration between the precast slab 2 and the tensile force transmission part 167b by appropriately protruding the reinforcing bars (not shown) arranged in the precast slab 2 from the precast slab into the cutout 62b, and to enhance the continuous integration between the precast slab 51, 2 and the joint part 166 by appropriately protruding the reinforcing bars (not shown) arranged in the precast slabs 51, 2 into the space extending from each precast slab to the opposing surfaces 162a, 162b.

Next, after the concrete strength of the tensile force transmission parts 167a, 167b and the joint part 166 is realized, the reaction force release mechanism 165 is operated to release the tension of the PC steel rod 163.

The reaction force release mechanism 165 may be configured, for example, so that the remote ends of two cylindrical reaction members (not shown) arranged coaxially with the PC steel rod 163 are abutted against the anchoring plates 161a and 161b, and the proximal ends are pushed apart to provide a reaction force that supports the tension of the PC steel rod 163, and the tension of the PC steel rod 163 can be released via the anchoring plates 161a and 161b by loosening the pushing and spreading action.

In this way, the tension of the released PC steel rod 163 is balanced with the compressive force in the surrounding concrete through the support pressure of the anchoring plates 161a, 161b, and the compressive force of the concrete is balanced by the compressive reaction forces received from the opposing surfaces 162a, 162b of the precast floor slabs 51, 2, respectively. Thus, the two precast floor slabs 51, 2 are pulled together and connected by the tensile force of the PC steel rod 163, which acts as a reaction force against the compressive forces acting on their opposing surfaces 162a, 162b via the joint 166.

After releasing the tension, the boxed-out operation work area 164 can be filled with concrete or mortar as appropriate.

The above-mentioned connection procedure, in which a joint is interposed between two precast decks, is a typical procedure not only for connection methods using connection units 61, but also for connection methods using long PC steel members. However, such joints are a means for absorbing unevenness on the opposing surfaces 162a, 162b of the precast decks 51, 2 and making the load transfer to the opposing surfaces as even as possible. If there is no risk of uneven load transfer occurring when the opposing surfaces 162a, 162b abut against each other, they may be omitted.

1 Precast deck installation jig 2 Precast deck 3 Girder 4 Support surface 5 Support bolt (pillar)
6 Base 7 Suspension mechanism 8 Nut 11 Connecting material 15 Hollow tube (through opening)
21 Lifting arm 22 PC steel (lifting rod)

Claims (7)

A precast deck installation jig comprising a support pillar that is loosely inserted into a through opening formed in the precast deck and whose base is configured to abut against the support surface of the girder over which the precast deck is spanned, and a suspension mechanism that is connected to the support pillar and receives a reaction force from the girder via the support pillar, thereby enabling the precast deck to be suspended in a state separated from the girder, and characterized in that the precast deck can be moved in an in-plane direction, with the movement width caused by the clearance that expands between the peripheral surface of the support pillar and the inner peripheral surface of the through opening being the limit. The precast deck installation jig according to claim 1, in which the lifting mechanism is composed of a lifting arm extending to the side of the support and a lifting rod connected to the protruding portion of the lifting arm and having a tip that can be attached to the precast deck. The precast deck installation jig according to claim 2, in which the lifting arms are a pair of lifting arms extending in opposite directions from the support columns, and the lifting rods are a pair of lifting rods connected to each of the lifting arms. A precast deck installation jig according to any one of claims 1 to 3, which is provided with a protrusion length adjustment mechanism for adjusting the length of the portion of the support that protrudes from the precast deck. A method for connecting precast floor slabs, which connects a new precast floor slab, a trailing precast floor slab, to a preceding precast floor slab that has been previously placed, comprising:
The trailing precast deck is suspended from the support surface of the girder by applying a reaction force to the girder, and is spaced apart from the girder and is spanned adjacent to the preceding precast deck;
A connecting unit is installed across the preceding precast floor slab and the following precast floor slab so that each end of the PC steel material constituting the connecting unit is fixed near the opposing end portions of the preceding precast floor slab and the following precast floor slab,
By releasing the tension previously introduced into the PC steel material, the trailing precast deck is pulled toward the leading precast deck and connected to the leading precast deck;
A method of connecting precast decks, characterized in that the space between the trailing precast deck and the girder is filled with mortar and the strength of the mortar is developed before the tensile force for lifting is released, or a temporary support material is interposed in the space between the trailing precast deck and the girder, and then the tensile force for lifting is released and mortar is filled in the space. A method for connecting precast floor slabs, which connects a new precast floor slab, a trailing precast floor slab, to a preceding precast floor slab that has been previously placed, comprising:
The trailing precast deck is suspended from the support surface of the girder by applying a reaction force to the girder, and is spaced apart from the girder and is spanned adjacent to the preceding precast deck;
PC steel members are inserted into the preceding precast floor slab and the following precast floor slab along their in-plane directions to introduce tension into the PC steel members;
A method of connecting precast decks, characterized in that the space between the trailing precast deck and the girder is filled with mortar and the strength of the mortar is developed before the tensile force for lifting is released, or a temporary support material is interposed in the space between the trailing precast deck and the girder, and then the tensile force for lifting is released and mortar is filled in the space. A method for connecting precast floor slabs, which connects a new precast floor slab, a trailing precast floor slab, to a preceding precast floor slab that has been previously placed, comprising:
The trailing precast deck is suspended from the support surface of the girder by applying a reaction force to the girder, and is spaced apart from the girder and is spanned adjacent to the preceding precast deck;
The following precast floor slab is moved in an in-plane direction while maintaining the tensile force for the lifting, thereby adjusting the horizontal clearance with the preceding precast floor slab;
The trailing precast deck and the preceding precast deck are interconnected while maintaining the tension force for the lifting ,
A method of connecting precast decks, characterized in that the space between the trailing precast deck and the girder is filled with mortar and the strength of the mortar is developed before the tensile force for lifting is released, or a temporary support material is interposed in the space between the trailing precast deck and the girder, and then the tensile force for lifting is released and mortar is filled in the space.

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