JP7778649B2 - Connection structure between corrugated steel web and sub-deck slab in corrugated steel web bridges - Google Patents

Description

The present invention relates to the joint structure between a corrugated steel web and a lower deck slab in a corrugated steel web bridge, which comprises a corrugated steel web, a concrete lower deck slab connected to the lower end of the corrugated steel web, and a concrete upper deck slab connected to the upper end of the corrugated steel web.

A corrugated steel web bridge is equivalent to a concrete box girder bridge in which the web is replaced with corrugated steel plates. Compared to concrete box girder bridges, corrugated steel web bridges have a structure that allows for reduced dead weight, longer spans, and less construction labor. When erecting a corrugated steel web bridge on steep terrain, the cantilever erection method is often used, as assembling supports supported directly on the ground raises safety and construction concerns.

For example, Patent Documents 1 and 2 describe a method in which a block of corrugated steel web is attached by overhanging it, the lower deck slab is constructed using suspension supports, precast concrete ribs and form plates are attached to the upper end of the corrugated steel web, concrete is poured onto the form plates, and the form plates and the poured concrete are integrated to form the upper deck. Furthermore, Patent Document 3 describes a method in which a mobile cart is used to attach a block of corrugated steel web by overhanging it, precast concrete form plates are attached to the lower end of the corrugated steel web, concrete is poured onto the form plates, and the form plates and the poured concrete are integrated to form the lower deck.

Japanese Patent Application Laid-Open No. 2004-116059 Japanese Patent Application Laid-Open No. 2004-116060 Japanese Patent Application Laid-Open No. 2006-118314

In the construction methods described in Patent Documents 1 to 3, at least the main body portions of the lower deck and upper deck are formed by pouring ready-mixed concrete at the construction site. When multiple concrete bridges are constructed in close proximity, such as when building a highway in a mountainous region, there is a risk that the demand for ready-mixed concrete will exceed the production capacity of the ready-mixed concrete plant in that area. Because on-site mixed concrete is not suitable for mass production and requires a great deal of labor to produce, it is difficult to make up for a shortage of ready-mixed concrete with on-site mixed concrete.

In order to reduce the amount of cast-in-place concrete, it is possible to consider using precast concrete members for the main parts of the lower deck, but the problem is how to join the precast concrete members to the corrugated steel web.

In light of the above background, the present invention aims to provide a suitable joint structure between a corrugated steel web and a sub-deck including a precast sub-deck member in a corrugated steel web bridge.

In order to solve the above-mentioned problems, one aspect of the present invention is a corrugated steel web bridge (1) comprising a plurality of corrugated steel webs (5) having corrugated steel plate portions (8) extending in the bridge axis direction and spaced apart from one another in the bridge width direction, a lower deck (6) connected to the lower end of the corrugated steel webs, and an upper deck (7) connected to the upper end of the corrugated steel webs, the corrugated steel webs and the lower deck are connected to a joint structure (18) in which the joint structure (18) comprises a lower flange (9) constituting a part of the corrugated steel webs and connected to the lower end of the corrugated steel plate portions, a precast lower deck member (11) constituting a part of the lower deck and having both ends in the bridge width direction placed on the lower flanges of two adjacent corrugated steel webs, a plurality of flat steel plate portions (21b) fixed to the upper surface of the lower flange so as to be spaced apart from one another in the bridge axis direction and perpendicular to the bridge axis direction, and a plurality of flat steel plate portions (21b) spaced apart from one another in the bridge axis direction and fixed to the upper surface of the lower flange so as to be spaced apart from one another in the bridge axis direction and perpendicular to the bridge axis direction. The system comprises a plurality of first reinforcing bars (22) located above the plate portion and protruding from the corrugated steel plate portion toward the precast lower deck member; a plurality of second reinforcing bars (23) spaced apart in the bridge axis direction, protruding from the concrete side surface of the precast lower deck member in the bridge width direction, and having hook portions (23b) that at least partially overlap the flat steel plate portion when viewed from the bridge axis direction; a plurality of third reinforcing bars (24) spaced apart in the bridge axis direction, located above the second reinforcing bars, protruding from the concrete side surface toward the corrugated steel plate portion and forming lap joints with the first reinforcing bars; and a cast-in-place concrete portion (12) cast between the end of the precast lower deck member on the lower flange in the bridge width direction and the corrugated steel plate portion so as to embed the flat steel plate portion and the first to third reinforcing bars.

In this configuration, the flat steel plate portion and the second reinforcing bar are positioned so that they partially overlap in the bridge axis direction, allowing them to resist shear forces in the bridge axis direction, and the lap joint between the first and third reinforcing bars allows them to resist forces in the bridge width direction, resulting in an ideal joint structure.

In the above aspect, the first and third reinforcing bars (22, 24) may include enlarged protruding ends (22d, 24b).

According to this aspect, the protruding end portion can shorten the anchorage length of the first and third reinforcing bars and the length of the lap splice, thereby reducing the size of the cast-in-place concrete section.

In the above aspect, the concrete side surface of the precast lower deck member (11) may include a lower side surface (11d) from which the second reinforcing bar (23) protrudes, and an upper side surface (11e) from which the third reinforcing bar (24) protrudes and which is recessed in the bridge width direction relative to the lower side surface.

This aspect ensures that the necessary length is secured at the top of the cast-in-place concrete section across the bridge width without making the lower section too long, thereby reducing the amount of cast-in-place concrete used.

In the above aspect, the first to third reinforcing bars (22, 23, 24) may include joint portions (22b, 23a, 24a) that are at least partially embedded in the cast-in-place concrete portion (12).

According to this configuration, the first to third reinforcing bars can be spliced after the precast lower deck component is placed on the lower flange, so the first to third reinforcing bars do not interfere with the work of placing the precast lower deck component on the lower flange.

In the above aspect, the bridge may further include a fourth reinforcing bar (25) extending in the bridge axis direction and embedded in the cast-in-place concrete section (12), the flat steel plate section (21b) having a through hole (21c) through which the fourth reinforcing bar is inserted, and the hook section (23b) of the second reinforcing bar (23) may include a portion that passes between the fourth reinforcing bar and the corrugated steel plate section (8).

In this configuration, the second and fourth reinforcing bars resist forces that move the corrugated steel web and the precast lower deck member apart in the bridge width direction, making the connection between the two stronger.

The above aspects provide a suitable joint structure between the corrugated steel web and the lower deck, including the precast lower deck member, in a corrugated steel web bridge.

FIG. 1 is a cross-sectional view of a corrugated steel web bridge according to an embodiment, the cross-sectional view being perpendicular to the bridge axis direction. An explanatory diagram showing the construction process of a corrugated steel web bridge according to an embodiment. FIG. 1 is a perspective view showing the construction process of a corrugated steel web bridge according to an embodiment. FIG. 1 is a diagram showing a horizontal cross section of a joint between a corrugated steel web and a lower deck in a corrugated steel web bridge according to an embodiment. FIG. 1 is a cross-sectional view of the lower part of the corrugated steel web of a corrugated steel web bridge according to an embodiment, which is perpendicular to the bridge axis direction. FIG. 1 is a cross-sectional view perpendicular to the bridge axis direction of a joint between a corrugated steel web and a lower deck in a corrugated steel web bridge according to an embodiment. Plan view of the lower deck during construction of the corrugated steel web bridge according to the embodiment An explanatory diagram showing a method for extending the erection tendons of a corrugated steel web bridge according to an embodiment.

The corrugated steel web bridge 1 according to the embodiment will now be described with reference to the drawings. As shown in Figures 1 and 2, the corrugated steel web bridge 1 comprises multiple substructures 2, box girders 3 spanning the multiple substructures 2, and wall parapets 4 fixed to both ends of the box girders 3 in the bridge width direction.

In Figure 2, the substructure 2 is indicated by a support symbol, and the substructure 2 shown on the right edge of Figure 2 is an abutment, while the substructure 2 shown in the center and left edge of Figure 2 are piers. There are other piers and abutments to the left of these, but they are not shown in the illustration.

As shown in Figure 1, the box girder 3 comprises two corrugated steel webs 5 extending in the bridge axis direction and spaced apart in the bridge width direction, a lower deck 6 connected to the lower ends of the two corrugated steel webs 5, and an upper deck 7 connected to the upper ends of the two corrugated steel webs 5. The corrugated steel web bridge 1 according to this embodiment is a road bridge in which a paved section 20 (see Figure 3 (F)) is provided on the upper deck slab 7, and the box girder 3, like the road surface, has a longitudinal gradient and a transverse gradient for draining rainwater. Note that Figure 1 omits the illustration of reinforcing bars, tendons, etc. included in the lower deck slab 6 and upper deck slab 7.

Each corrugated steel web 5 includes a corrugated steel section 8, a bottom flange 9 connected to the lower end of the corrugated steel section 8, and an top flange 10 connected to the upper end of the corrugated steel section 8. The corrugated steel section 8 is formed from steel plate shaped to corrugate inward and outward in the bridge width direction as it moves in the bridge axis direction. The bottom flange 9 and top flange 10 are flat steel plates that are approximately perpendicular to the vertical direction. They are fixed to the lower and upper ends of the corrugated steel section 8 by welding or other means, and protrude inward and outward in the bridge width direction beyond the corrugated steel section 8. The inward protrusion length of the lower flange 9 in the bridge width direction is longer than the inward protrusion length of the upper flange 10 in the bridge width direction.

The lower deck 6 includes multiple precast lower deck members 11 placed on the lower flanges 9 at both ends in the bridge width direction and divided in the bridge axis direction, and a cast-in-place concrete section 12 formed by pouring ready-mixed concrete into a recess defined by the upper surface of the lower flanges 9, the inner surface of the corrugated steel plate section 8 in the bridge width direction, and the side surface of the precast lower deck member 11 in the bridge width direction. The precast lower deck member 11 is a flat precast concrete member and includes lower horizontal reinforcement 11a and upper horizontal reinforcement 11b (see Figure 6) that are reinforcing bars extending in the bridge width direction, vertical reinforcement bars (not shown) that are reinforcing bars extending in the bridge axis direction, and a concrete section 11c (see Figure 6) in which these reinforcing bars are embedded. The upper horizontal reinforcement 11b is positioned above the lower horizontal reinforcement 11a so as to be vertically aligned with the lower horizontal reinforcement 11a. To enable the precast lower deck member 11 to be dropped from above and placed on the lower flange 9, the length of the precast lower deck member 11 in the bridge width direction is shorter than the distance between the opposing side edges of the two upper flanges 10 and longer than the distance between the opposing side edges of the two lower flanges 9. Hereinafter, the term "precast" begins with "precast" and refers to a precast concrete member.

The upper deck slab 7 is placed on the upper flanges 10 of the two corrugated steel webs 5 and includes a plurality of precast ribs 13 extending in the bridge width direction and spaced apart in the bridge axis direction, a plurality of precast formwork plates 14 spanning between the precast ribs 13 and extending in the bridge axis direction, and an upper deck body 15 formed by pouring ready-mixed concrete onto the upper flanges 10 and the precast formwork plates 14.

Each precast rib 13 is a flat plate-shaped member that is perpendicular to the bridge axis. Both ends of the precast rib 13 in the bridge width direction are located outward in the bridge width direction from the corrugated steel plate web 5, and are aligned with both ends of the upper deck slab 7 in a plan view.

Each precast formwork plate 14 is a flat member whose main surface rests on the upper edge of the precast rib 13. The multiple precast formwork plates 14 are not placed directly above the upper flange 10, but are placed adjacent to each other without any gaps in the bridge width direction on the upper edges of the precast ribs 13 other than the area directly above the upper flange 10.

The concrete that makes up the upper deck body 15 embeds reinforcing bars and tension members (not shown) that extend in the bridge axis direction and width direction, as well as headed studs (not shown) that protrude upward from the upper flange 10.

Next, we will explain the erection method of the corrugated steel web bridge 1. The lower deck 6 and upper deck 7 are constructed so that they overhang each block, and Figure 3 shows one of these blocks.

First, workers install the column capital 16 on the substructure 2, as shown in Figure 2 (A). The column capital 16 is part of the box girder 3.

Next, workers span the corrugated steel web 5 between adjacent column capitals 16, as shown in Figures 2(B) and 3(A). The corrugated steel web 5 may be erected using a crane (not shown), or by the cantilever erection method or the extrusion erection method. The corrugated steel web 5 is erected over the entire span at least for each span, prior to the construction of the lower deck 6 and upper deck 7. The corrugated steel web 5 may also be erected for the entire corrugated steel web bridge 1, prior to the construction of the lower deck 6 and upper deck 7.

Next, as shown in Figure 2(B), workers set up a mobile scaffolding 17 that includes a work platform 17a that is supported movably in the bridge axial direction on the upper flange 10 of the corrugated steel web 5 and is located below the lower flange 9. The mobile scaffolding 17 is primarily used as a scaffolding for constructing the joint structure 18 between the corrugated steel web 5 and the lower deck slab 6, as shown in Figures 4 to 6. In the example shown, the lower deck slab 6 and upper deck slab 7 are constructed so that they project one block at a time from the column capital 16 in the center of Figure 2 toward the column capitals 16 on the left and right, but the lower deck slab 6 and upper deck slab 7 may also be constructed from adjacent column capitals 16 toward each other.

Next, as shown in Figure 3(B), workers use a crane (not shown) to drop the precast lower deck member 11 onto the lower flange 9, and then use the mobile scaffolding 17 to construct the joint structure 18 shown in Figures 4 to 6. The structure and construction method of the joint structure 18 will be described later.

After constructing the joint structure 18 for that block, workers move the mobile scaffolding 17 by the length of one block in a direction that extends beyond the column capital 16, as shown in Figure 2(C), and construct the lower deck slab 6 of the new block in the same manner as above, while also constructing the upper deck slab 7 of the previous block above the portion where the lower deck slab 6 has already been constructed, as shown in Figures 3(C) to 3(E).

When constructing the upper deck slab 7 in each block, workers first use a crane (not shown) to place multiple precast ribs 13 on the two upper flanges 10 so that they span between the two corrugated steel webs, as shown in Figure 3(C). The multiple precast ribs 13 are spaced apart in the bridge axis direction and arranged so that their main surfaces are perpendicular to the bridge axis direction. Next, as shown in Figure 3(D), workers use a crane (not shown) to place multiple precast formwork plates 14 on these precast ribs 13, and then place reinforcing bars, tendons extending in the bridge width direction, and sheaths (not shown) for inserting the tendons extending in the bridge axis direction on the multiple precast formwork plates 14. Finally, they install formwork 19 that connects the bridge width end of the upper flange 10 to the end of the precast formwork plate 14 located directly above it. Next, as shown in Figure 3(E), workers pour concrete onto the upper flange 10 and precast formwork plates 14 to form the upper deck body 15, and tension the tendons extending in the bridge width direction. To suppress deflection due to the weight of the protruding upper deck slab 7, temporary tendons (not shown) extending in the bridge axis direction may be placed using external cables to apply prestress to the protruding upper deck slab 7. Note that precast formwork plates 14 may also be used as the formwork 19.

As shown in Figure 2 (D), workers then construct the lower deck 6 of each block, in a protruding manner, while also constructing the upper deck 7 of the block immediately preceding it. When the lower deck 6 and upper deck 7 reach the adjacent column capitals 16 (the column capitals 16 on the left and right sides of the page in Figure 2), the protruding lower deck 6 and upper deck 7 are closed with the column capitals 16. It is preferable that the fill concrete used for closing be low-heat, low-shrinkage concrete.

Then, as shown in Figure 3 (F), workers install the balustrades 4 at both ends of the upper deck slab 7 in the bridge width direction, and construct the pavement 20 on the upper deck slab 7. Note that instead of installing the balustrades 4 after the entire upper deck slab 7 is completed, they may be installed on each block as construction of the upper deck slab 7 is completed. Instead of constructing the upper deck slab 7 one block at a time, construction of multiple blocks located above the completed lower deck slab 6 may be performed all at once.

The joint structure 18 will be described with reference to Figures 4 to 6. In addition to the lower flange 9, the precast lower deck member 11, and the cast-in-place concrete section 12, the joint structure 18 includes an angle dowel 21 fixed to the upper surface of the lower flange 9, a plurality of first reinforcing bars 22 located above the angle dowel 21 and protruding from the corrugated steel plate section 8 toward the precast lower deck member 11, a plurality of second reinforcing bars 23 having hook portions 23b that protrude from the concrete side surface of the precast lower deck member 11 in the bridge width direction, a plurality of third reinforcing bars 24 located above the second reinforcing bars 23 and protruding from the concrete side surface of the precast lower deck member 11 in the bridge width direction toward the corrugated steel plate section 8, a fourth reinforcing bar 25 extending in the bridge axis direction, and an unevenness adjustment section 26 formed between the lower flange 9 and the precast lower deck member 11 by mortar. The angle dowel 21 and the first to fourth reinforcing bars 22, 23, 24, and 25 are embedded in the cast-in-place concrete section 12.

As shown in Figures 5 and 6, multiple angle dowels 21 are arranged on the upper surface of the portion of the lower flange 9 that protrudes inward in the bridge width direction, spaced apart from each other in the bridge axis direction. Each angle dowel 21 is a steel material formed by bending a rectangular flat plate 90 degrees, and includes a bottom plate portion 21a fixed by welding or other means so that its surface abuts the upper surface of the lower flange 9, and a flat steel plate portion 21b arranged perpendicular to the bridge axis direction. The flat steel plate portion 21b has a through hole 21c that passes through in the bridge axis direction. The through holes 21c provided in each flat steel plate portion 21b are aligned in the bridge axis direction, and a fourth reinforcing bar 25 is inserted into the through hole 21c.

As shown in Figures 4 and 5, the first reinforcing bar 22 includes a base 22a fixed to the corrugated steel plate portion 8 by welding or the like, and an extension portion 22c connected to the tip of the base 22a via a joint portion 22b. The joint portion 22b is formed, for example, by enclosed welding. The first reinforcing bar 22 protruding from the corrugated steel plate portion 8 toward the precast lower deck member 11 includes an expanded protruding end portion 22d, which is the end of the extension portion 22c opposite the joint portion 22b. The joint portion 22b is positioned closer to the corrugated steel plate portion 8 than the side surface of the precast lower deck member 11 in the bridge width direction, so that the precast lower deck member 11 can be dropped in from above. The first reinforcing bar 22 may be positioned so as to overlap the flat steel plate portion 21b of the angle dowel 21 in a plan view, or may be offset in the bridge axis direction relative to the flat steel plate portion 21b.

As shown in Figure 6, the second reinforcing bar 23 is connected to the lower horizontal bar 11a of the precast lower deck member 11 via a joint portion 23a. The joint portion 23a may be, for example, a mechanical joint in which the externally threaded lower horizontal bar 11a and the second reinforcing bar 23 are screwed into an internally threaded sleeve. In this case, at least a portion of the sleeve is embedded so as to be exposed on the side surface of the concrete portion 11c of the precast lower deck member 11 in the bridge width direction. The second reinforcing bar 23 includes a hook portion 23b bent upward. The bending angle of the hook portion 23b is preferably 180°, but may also be 135° or 90°. The hook portion 23b includes a portion that passes between the fourth reinforcing bar 25 and the corrugated steel plate portion 8. The second rebar 23 is positioned offset in the bridge axis direction relative to the flat steel plate portion 21b of the angle dowel 21, and the hook portion 23b at least partially overlaps the flat steel plate portion 21b of the angle dowel 21 when viewed from the bridge axis direction.

As shown in Figures 5 and 6, the third reinforcing bar 24 is connected to the upper horizontal bar 11b of the precast lower deck member 11 by a joint portion 24a. The joint portion 24a is, for example, a mechanical joint similar to the joint portion 23a of the second reinforcing bar 23. The third reinforcing bar 24 protruding from the precast lower deck member 11 toward the corrugated steel plate portion 8 includes an enlarged protruding end portion 24b. The third reinforcing bar 24 is preferably arranged so that it is aligned vertically with the second reinforcing bar 23. The height at which the third reinforcing bar 24 is arranged is approximately the same as the height at which the first reinforcing bar 22 is arranged, and the third reinforcing bar 24 forms a lap joint with the first reinforcing bar 22. To facilitate the work of joining the extension portion 22c of the first reinforcing bar 22 to the base portion 22a and the work of joining the third reinforcing bar 24 to the upper horizontal bar 11b, it is preferable that the third reinforcing bar 24 be positioned offset in the bridge axis direction relative to the first reinforcing bar 22 so as to form an open lap joint with the first reinforcing bar 22.

The side surfaces of the concrete portion 11c of the precast lower deck member 11 in the bridge width direction include a lower side surface 11d from which the second reinforcing bars 23 protrude, and an upper side surface 11e from which the third reinforcing bars 24 protrude and which is recessed in the bridge width direction relative to the lower side surface 11d.

The construction method for the joint structure 18 will be explained with reference to Figures 4 to 6. With the base 22a of the first reinforcing bar 22 fixed to the corrugated steel plate section 8, the worker spans the corrugated steel plate web 5 between the column capitals 16 (see Figure 2 (B)). The worker pours mortar to form the unevenness adjustment section 26 on the inner end of the lower flange 9 in the bridge width direction. The worker uses a crane or the like (not shown) to drop the precast lower deck member 11 from above and place both ends of the precast lower deck member 11 in the bridge width direction onto the lower flange 9 via the unevenness adjustment section 26. The worker connects the extension portion 22c of the first rebar 22 to the base portion 22a, connects the second rebar 23 to the lower horizontal bar 11a of the precast lower deck member 11, connects the third rebar 24 to the upper horizontal bar 11b of the precast lower deck member 11, and inserts the fourth rebar 25 through the through hole 21c in the flat steel plate portion 21b. Next, the worker pours ready-mixed concrete between the side of the precast lower deck member 11 in the bridge width direction on the lower flange 9 and the corrugated steel plate portion 8 so as to embed the angle dowel 21 and the first to fourth rebars 22, 23, 24, and 25, forming the cast-in-place concrete portion 12.

As shown in Figure 7, the lower deck 6 includes a plurality of permanent tendons 27 extending in the bridge axis direction and maintained in a tensioned state after completion, and a plurality of temporary tendons 28 extending in the bridge axis direction, tensioned during construction, and removed after completion. The temporary tendons 28 are tensioned during construction to suppress deflection due to the weight of the overhanging lower deck 6, thereby prestressing the overhanging lower deck 6. One end of the temporary tendons 28 is fixed to the column capital 16 (see Figure 2), and the other end is extended each time construction of the lower deck 6 of a new block is completed to prestress the lower deck 6 of the new block. Two rectangular cutouts 29 in plan view are formed in the end of the precast lower deck member 11 of the newly installed block facing the existing block in the bridge axis direction, through which the temporary tendons 28 pass. The cutouts 29 may also be provided at the end of the precast lower deck member 11 of the existing block in the bridge axis direction that faces the new block. The cutouts 29 are used to extend the temporary tendons 28, and after the temporary tendons 28 are extended, ready-mixed concrete is poured into the cutouts 29 to form the post-filled concrete section 30. The temporary tendons 28 are extended one by one, with the other temporary tendons 28 tensioned before or after extension. The temporary tendons 28 are preferably PC steel bars.

The method of extending the temporary tendons 28 will be explained with reference to Figure 8. In the explanation using Figure 8, of the precast lower deck members 11 that were prestressed by the temporary tendons 28 in the pre-extension state, the precast lower deck member 11 located at the end in the overhanging direction will be referred to as existing block B(n), and the newly installed precast lower deck member 11 will be referred to as new block B(n+1). Here, n is an integer greater than or equal to 1, and in the state shown in Figure 8(A), blocks B(1) to B(n) are prestressed by the temporary tendons 28. Furthermore, in Figures 8(B) to 8(F), the reference numerals for components that have not changed from the figures above have been omitted.

As shown in Figure 8 (A), the existing portion 28a of the temporary tensioning member 28 is fixed in a tensioned state to the protruding end of the existing block B(n) in the bridge axis direction by a fixing device 33 including a nut 31 threaded onto the existing portion 28a of the temporary tensioning member 28 and a bearing plate 32 sandwiched between the existing block B(n) and the nut 31. The existing portion 28a and its extension 28b of the temporary tensioning member 28 are inserted into a sheath 34 embedded in the precast lower deck member 11. The temporary tensioning member 28 is of the unbonded type. A first coupler sheath 35 is provided on the side of the sheath 34 of the new block B(n+1) facing the existing block B(n). The first coupler sheath 35 includes a fixed portion 35a fixed to the new block B(n+1) and a core portion 35b partially received within the fixed portion 35a and slidable relative to the fixed portion 35a so as to be exposed from the fixed portion 35a.

As shown in Figure 8 (B), after releasing the tension on the temporary tension member 28, the worker removes the fixing device 33 from the existing portion 28a of the temporary tension member 28.

Next, as shown in Figure 8(C), the worker attaches a second coupler sheath 36, which can be connected to the core portion 35b of the first coupler sheath 35, to the sheath 34 of the existing block B(n).

Next, as shown in Figure 8 (D), the worker uses a mechanical joint 37 to connect the extension portion 28b to the existing portion 28a of the temporary tension member 28.

Next, as shown in Figure 8(E), the worker slides the core portion 35b to connect it to the second coupler sheath 36, tensions the temporary tension member 28, which is made up of the existing portion 28a and the extension portion 28b, and uses the fixing device 33 (see Figure 8(A)) to fix the temporary tension member 28 to the end face of the new block B(n+1) that protrudes in the bridge axis direction, thereby applying prestress from the column capital 16 (see Figure 2) to the new block B(n+1). To improve sealing, it is preferable to place a water-swelling nonwoven fabric 38 at the joint of the core portion 35b to the second coupler sheath 36 and between the fixing portion 35a and the core portion 35b when the core portion 35b is connected to the second coupler sheath 36.

After all temporary tendons 28 have been extended and tensioned, workers pour ready-mixed concrete into the cutouts 29 to form the post-filled concrete section 30, as shown in Figure 8 (F).

The effects of the above embodiment are explained below.

As shown in Figures 1 and 2, when constructing the lower deck slab 6 and upper deck slab 7, the corrugated steel plate web 5 can be used as support for constructing the lower deck slab 6 and upper deck slab 7, eliminating the need for support supported on the ground.

Since both ends of the precast lower deck member 11 in the bridge width direction are supported by the lower flanges 9 of the corrugated steel webs 5 spanning between the column capitals 16, the mobile scaffolding 17 does not need to support the lower deck slab 6, unlike the suspended supports described in Patent Documents 1 and 2, and can therefore have a relatively simple structure.

The corrugated steel web 5 has a structure and arrangement that allows the precast lower deck member 11 to be dropped from above and placed on the lower flange 9, allowing precast concrete members to be used for the main part of the lower deck 6, reducing the amount of fresh concrete used at the construction site.

As shown in Figures 4 to 6, the combination of the angle dowel 21 and the second reinforcing bar 23 having the hook portion 23b resists shear force in the bridge axis direction, thereby narrowing the width of the lower part of the cast-in-place concrete section 12 in the bridge width direction. The lap joints of the first and third reinforcing bars 22, 24 resist forces in the bridge width direction. Furthermore, because the first and third reinforcing bars 22, 24 have enlarged protruding ends 22d, 24b, the anchorage lengths of the first and third reinforcing bars 22, 24 can be relatively short, and the length of the lap joints can be relatively short, thereby narrowing the width of the upper part of the cast-in-place concrete section 12 in the bridge width direction. Furthermore, by recessing the upper side surface 11e of the precast lower deck member 11 inward in the bridge width direction relative to the lower side surface 11d, the required length can be secured in the upper part of the cast-in-place concrete section 12 in the bridge width direction without excessively increasing the length of the lower part, thereby reducing the amount of fresh concrete used.

The first to third reinforcing bars 22, 23, and 24 are connected by joints 22b, 23a, and 24a after the precast lower deck member 11 is placed on the lower flange 9. Therefore, the first to third reinforcing bars 22, 23, and 24 do not interfere with the process of dropping the precast lower deck member 11 from above and placing it on the lower flange 9.

The hook portion 23b of the second reinforcing bar 23 passes between the fourth reinforcing bar 25 inserted through the through hole 21c of the angle dowel 21 and the corrugated steel plate portion 8, strengthening the connection between the precast lower deck member 11 and the corrugated steel plate web 5. If the hook portion 23b has a bending angle of 180° and is positioned so as to wrap around the fourth reinforcing bar 25, the connection between the precast lower deck member 11 and the corrugated steel plate web 5 will be even stronger.

As shown in Figures 7 and 8, as the lower deck 6 is constructed to overhang, the temporary tendons 28 are extended, allowing the existing portions 28a of the temporary tendons 28 to be used to apply prestress from the column capitals 16 (see Figure 2) to the newly installed precast lower deck member 11.

The temporary tendons 28 are extended one by one, so a certain degree of prestress can be applied to the lower deck slab 6 even during the extension work.

The precast lower deck member 11 has a cutout 29 through which the temporary tension member 28 passes, making it easy to extend the temporary tension member 28.

The temporary tendons 28 are received in the sheath 34 unbonded, and the connection between the existing section 28a and the extension section 28b is also covered by the first and second coupler sheaths 35, 36. This prevents concrete from adhering to the temporary tendons 28, facilitating release and re-tensioning. The core section 35b of the first coupler sheath 35 includes a water-expanding nonwoven fabric 38, which enhances the sealing ability of the first and second coupler sheaths 35, 36 against the ready-mixed concrete used to form the post-filled concrete section 30, further reducing the possibility of concrete adhering to the temporary tendons 28. After closure, the sheath 34 through which the temporary tendons 28 are inserted is filled with grout (not shown). Because the temporary tendons 28 are continuous between the precast lower deck members 11, this has the effect of improving the ultimate toughness of the completed corrugated steel web bridge 1.

Tests were conducted using a specimen equipped with the corrugated steel web 5 and lower deck slab 6 of the above embodiment, but without the upper deck slab 7. The lower flange 9 was placed on the test stand, and the upper end of one of the corrugated steel webs 5 was pushed and pulled in the width direction of the bridge using a jack. When the oscillating moment at the design load was reproduced, no gaps were observed at the joint surface between the cast-in-place concrete section 12 and the corrugated steel plate section 8. Furthermore, when a yield moment load was applied, it was confirmed that cracks occurred at the expected cross section of the cast-in-place concrete section 12.

This concludes the explanation of specific embodiments, but the present invention is not limited to the above embodiments and modifications, and can be implemented in a wide variety of ways. There may be three or more corrugated steel webs, and in this case, angle dowels and first rebars are provided on both sides of the lower flange of the corrugated steel web located in the middle of the bridge width direction, and a precast lower deck member is placed on top of it. The corrugated steel webs may also be inclined outward in the bridge width direction as they extend upward.

DESCRIPTION OF SYMBOLS 1: Corrugated steel plate web bridge 5: Corrugated steel plate web 6: Lower deck slab 7: Upper deck slab 8: Corrugated steel plate section 9: Lower flange 11: Precast lower deck slab member 11a: Lower horizontal reinforcement 11b: Upper horizontal reinforcement 11c: Concrete section 11d: Lower side surface 11e: Upper side surface 12: Cast-in-place concrete section 18: Joint structure 21: Angle dowel 21b: Flat steel plate section 21c: Through hole 22: First reinforcing bar 22b: Joint section 22d: Protruding end 23: Second reinforcing bar 23a: Joint section 23b: Hook section 24: Third reinforcing bar 24a: Joint section 24b: Protruding end 25: Fourth reinforcing bar

Claims (5)

A corrugated steel web bridge includes a plurality of corrugated steel webs having corrugated steel plate portions extending in the bridge axis direction and spaced apart from each other in the bridge width direction, a lower deck slab connected to the lower end of the corrugated steel webs, and an upper deck slab connected to the upper end of the corrugated steel webs. The corrugated steel webs and the lower deck slab are joined together in a joint structure,
A lower flange that forms part of the corrugated steel plate web and is connected to a lower end of the corrugated steel plate portion;
A precast lower deck member that constitutes a part of the lower deck and has both ends in the bridge width direction placed on the lower flanges of the two adjacent corrugated steel plate webs;
A plurality of flat steel plate portions fixed to the upper surface of the lower flange so as to be spaced apart from each other in the bridge axis direction and perpendicular to the bridge axis direction;
A plurality of first reinforcing bars spaced apart from each other in the bridge axis direction, located above the flat steel plate portion, and protruding from the corrugated steel plate portion toward the precast lower deck member;
A plurality of second reinforcing bars that are spaced apart from each other in the bridge axis direction, protrude from the concrete side surface of the precast lower deck member in the bridge width direction, and have hook portions that at least partially overlap the flat steel plate portion when viewed from the bridge axis direction;
A plurality of third reinforcing bars that are spaced apart from each other in the bridge axis direction, are located above the second reinforcing bars, protrude from the concrete side surface toward the corrugated steel plate portion, and form lap joints with the first reinforcing bars;
A joint structure comprising a cast-in-place concrete section poured between the end of the precast lower deck member on the lower flange in the bridge width direction and the corrugated steel plate section so as to embed the flat steel plate section and the first to third reinforcing bars. The joint structure described in claim 1, wherein the first and third reinforcing bars include enlarged protruding ends. The joint structure described in claim 1 or 2, wherein the concrete side surface of the precast lower deck member includes a lower side surface from which the second reinforcing bars protrude, and an upper side surface from which the third reinforcing bars protrude and which is recessed in the bridge width direction relative to the lower side surface. The joint structure described in claim 1, wherein the first to third reinforcing bars include joint portions that are at least partially embedded in the cast-in-place concrete portion. Further provided is a fourth reinforcing bar extending in the bridge axis direction and embedded in the cast-in-place concrete portion,
The flat steel plate portion has a through hole through which the fourth reinforcing bar is inserted,
The joint structure according to claim 1 , wherein the hook portion of the second reinforcing bar includes a portion that passes between the fourth reinforcing bar and the corrugated steel plate portion.