JP2734985B2 - Cantilever shed and its construction method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cantilever type shed for protecting roads and railway tracks from falling rocks and avalanches, and a method of constructing the same.

[0002]

2. Description of the Related Art When a shed for covering an upper part of a road or the like is constructed, a method of using a precast concrete member manufactured in a factory instead of constructing a formwork on site and placing concrete is used. Has become. For example, as is known from Japanese Patent Publication No. 1-4895 and Japanese Patent Publication No. 1-2722, a roof is formed by integrally tightening a plurality of main girders with a laterally tightening PC steel material extending in the longitudinal direction of the road. A support wall is provided on the mountain side of the road, and a plurality of columns are erected on the valley side of the road, and both sides of the roof in the width direction of the roof are rigidly connected to the support wall and the column, respectively. On the side, a lower foundation work that will be the foundation of the column is being constructed.

In addition to the above-described shed for supporting both ends of the roof, Japanese Patent Application Laid-Open No. 1-244003 discloses that
The overhanging floor slab that becomes the roof is sloping upward toward the valley side, and the floor slab is fixed to the support wall on the mountain side, and the floor slab is fixed to the mountain side with an anchor inserted in the width direction of the road Rockshed has been proposed.

[0004]

In the case of the shed supporting both ends of the roof, it is sometimes difficult to construct a lower foundation work on the valley side of the road, and the width of the road is narrowed by the pillars on the valley side. There was a problem. In addition, there is a problem in that, on a road such as a mountain section where a curve is continuous, the columns of the road block the view, and the surrounding scenery is impaired. Furthermore, in order to construct the shed, there are many construction sites on the mountain side and the valley side of the road, so it was difficult to secure road traffic during the construction period.

In the above-mentioned rock shed, the overhanging floor slab is provided in a cantilever manner, so that the foundation work and columns on the valley side are not required, but the overhanging floor slab is cantilevered upward toward the valley side. In the case of a road having a large width, it is difficult to cover the entire upper portion of the road.In order to increase the width of the floor slab in the width direction of the road, the thickness of the overhanging floor slab is reduced. Larger, factory fabrication was practically difficult. Further, when the thickness of the floor slab is increased, the weight of the single unit increases, so that a specially large heavy machine is required at the time of erection, and the erection work is complicated.

Accordingly, an object of the present invention is to provide a cantilevered shed capable of covering the entire upper portion of a road without providing a structure on a valley side, and securing road traffic during construction. It is an object of the present invention to provide a method for constructing a cantilevered shed that can cover the entire upper part of a road.

[0007]

A cantilevered shed according to the first aspect of the present invention is a precast concrete lower beam member prestressed in the width direction of the road with PC steel, and concrete is integrally formed on the lower beam member. The concrete for floor slab formed by casting is provided diagonally upward toward the mountain side between the valley side of the lower beam member and the mountain side of the road to apply prestress to the concrete for floor slab. And a PC cable.

According to a second aspect of the present invention, a concrete lower beam member prestressed with a PC steel material in the width direction of the road is manufactured at a factory, and a supporting wall is constructed along a mountain wall. The plurality of lower beam members are fixed to the support wall at the mountain side, and a plurality of the beams are arranged side by side in the length direction of the road. P
C cable is stretched, concrete for floor slab is cast on the upper part of the lower beam member, and after the concrete for floor slab hardens,
After loosening the tension of the PC cable, the PC cable is pretensioned to give a prestress to the concrete for floor slab.

[0009]

According to the first aspect of the present invention, a prestressed lower beam member is temporarily provided on site, and the lower beam member is used instead of a formwork to cast concrete for floor slabs. A cantilevered shed is constructed by prestressing concrete for use with a PC cable. Then, a predetermined structural strength can be given to the cantilevered shed by a combined force of the prestress applied to the lower beam member and the prestress applied to the concrete for the floor slab.

According to the second aspect of the invention, after the concrete for the floor slab is cast, in the cantilever state where only the valley side is fixed, tension is generated in the PC cable by the weight of the lower beam member and the concrete for the floor slab. Supports the lower beam member and the concrete for the floor slab. However, the concrete for the floor slab hardened in this state is not subjected to tension by the PC cable. Further, even if concrete for floor slab is cast on the lower beam member in a state where both ends are supported, the tension by the PC cable does not act on the hardened concrete for slab. For this reason, a predetermined prestress can be given to the concrete for floor slab by loosening the PC cable once and then performing the main tension. Then, a predetermined structural strength can be given to the cantilevered shed by a combined force of the prestress applied to the lower beam member and the prestress applied to the concrete for the floor slab.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 to 10 show an embodiment of the present invention, in which a roof 1 of a shed provided in a cantilever manner on an upper portion of a road R is provided with a plurality of lower beams 2 made of precast concrete. It is constructed by connecting a plurality of juxtaposed in the longitudinal direction and placing concrete 3 for the floor slab on the upper part at the top, and the size of one lower beam member 2 is, for example, 8.7 meters in the road width direction. , Formed in a large size with a longitudinal direction of about 2 meters and covering the entire upper part of the road R. Reference numeral 4 denotes a concrete supporting wall, which is fixed to the ground G on the mountain side by a fixing member 5 such as a PC steel material.
At the upper part, a step-shaped beam fixing portion 6 projecting toward the valley side is formed. The lower beam member 2 has a flat top plate 7.
A web 8 projecting from the lower surface of the top plate 7 and continuing in the width direction of the road; and cross beams 9 and 9A projecting from the lower surface of the top plate 7 on the mountain side and the valley side and continuing in the longitudinal direction of the road. An upper cross beam portion 10 protruding from the upper surface of the valley side of the top plate portion 7 and continuing in the longitudinal direction of the road. The top plate portion 7 and the web 8 are pretensioned by a plurality of PC steel materials 11 or post. Prestress is applied in the width direction of the road by a tension method. Further, a plurality of ducts 12 are formed in the cross beams 9, 9A in the longitudinal direction, and each of the continuous ducts 12 is formed.
A plurality of lower beam members 2 are integrally tightened by a post-tensioning method. As shown in FIGS. 3 and 4, a plurality of ducts 14 are formed on the upper cross beam portion 10 on both sides in the longitudinal direction of the road with the web 8 interposed therebetween, and the ducts 14 are formed obliquely upward toward the mountain side. A recess 15 is formed on the upper surface of the valley-side end of the upper cross beam portion 10 corresponding to the duct 14, and a fixing plate 16 is fixedly provided at the valley-side end of the duct 14. The PC cable 17 with the sheath 17A inserted into the duct 14 is fixed in the recess 15 by screwing a nut 18 as a fixing tool to a male screw portion at a valley side end, and a central portion is used for the floor slab. The support 3 is inserted into the concrete 3, and the mountain side is inserted into a duct 19 formed in the support wall 4, and the end of the mountain is fixed on the mountain-side back surface of the support wall 4 by a fixing device 20. The upper surface of the concrete 3 for the floor slab is formed in parallel to the upper surface of the upper cross beam portion 10 so as to be parallel to the PC cable 17 and inclined upward toward the mountain side, and the upper surface thereof is 6.34.
The lower beam member 2 is provided to be inclined downward by about 5 degrees toward the mountain side. Further, a fixing surface 10A that is orthogonal to the duct 14 at substantially 90 degrees is formed in the upper horizontal beam portion 10. Furthermore, a plurality of vertical mounting holes 22 for inserting anchor bolts 21 are formed in the beam fixing portion 6, and a vertical duct 23 is formed in the lower beam member 2 corresponding to the mounting holes 22, This duct 23 is aligned with the mounting hole 22, and a rubber bearing (not shown) is interposed between the upper surface of the beam fixing portion 6 and the lower surface of the cross beam portion 9,
Insert the anchor bolt 21 from the duct 23 into the mounting hole 22
The lower hole member 2 is connected to the support wall 4 by filling the mounting hole 22 and the duct 23 with non-shrinkable mortar (not shown). On the back side of the support wall 4, a plurality of reinforcing steel materials 24 such as H-section steels are buried in the vertical direction.

In the drawing, reference numeral 25 denotes an enclosing block, and reference numeral 26 denotes a sand cushion laid on the concrete 3 for the floor slab. In addition, the concrete beam member 2 and the concrete
Thus, the main girder 27 is formed. Further, a plurality of dowel bars 28 are fixed to the lower beam member 2 at equal intervals in the length direction and at equal intervals in the width direction.

Further, reference numeral 31 denotes a temporary設支coercive Engineering, formed in partnership and steel, the height adjustment jack 32 for adjusting the valley height of the lower beam member 2 is provided at its upper portion ing. Reference numeral 33 denotes a revolving crane provided with a telescopic arm 33A, which is used for lifting the lower beam member 2, the PC cable 17, and the like. Reference numeral 34 denotes a tensioning jack for adjusting the tension of the PC cable 17. The tensioning jack 34 is suspended and held by the crane 33 or the crawler type mini crane 35 running on the main girder 27. Numeral 36 denotes a concrete pump truck for casting concrete from the tip of a pressure feed pipe 36A. Reference numeral 37 denotes a scaffold with handrails provided at the tip of the lower beam member 2. Further, 38 is a back-filling concrete and Da設between the walls of the rear and mountain of the support wall 4, is construction in the rack設前the lower beam member 2.

Next, a method of applying the shed will be described. First, a formwork is assembled on site and concrete is cast to construct a support wall 4. Temporary support work on the valley side of Road R
As shown in FIG. 5, the lower beam member 2 is lifted by using a crane 33, and is erected between the beam fixing portion 6 and the temporary supporter 31. It is fixed to the beam fixing part 6 and the valley side is placed on a height adjusting jack 32 of the support frame 16. In this case, as shown in FIG. 5, the road R below the lower beam member 2 can pass through places other than the construction work vehicle such as the crane 33. Then, when the lower beam member 2 is arranged in one section in the road length direction, for example, five sheets are arranged in parallel, the laterally tightening PC steel material 13 is inserted into the duct 12 and tightened with a predetermined tension, and the plurality of lower beam members 2 are connected. Tighten and integrate laterally. Also, as shown in FIG. 6, the PC cable 17 is inserted into the ducts 19 and 14, the nut 18 and the fixing tool 20 are attached, and between the valley side of each lower beam member 2 and the support wall 4, A PC cable 17 that extends obliquely upward toward the mountain side is stretched. In this case, the PC cable 17 having a sheath 17A is used. When the PC cable 17 is lifted by the crane 33, the PC cable 17 is extended from the rolled transport package using a suspending jig that does not deform the sheath 17A. When
Make it possible to work safely using a turntable or the like. Also, since the weight of each PC cable 17 is large, a heavy winch (not shown) is fixed on the support wall 4, and work is performed using the crane 33, a lever block (not shown), or the like. I do. When the PC cable 17 is stretched, a tension jack 34 arranged on the valley side is used.
Is used to calculate the tension of the PC cable 17, ie, P
The valley side of the lower beam member 2 is supported by the C cable 17, and thereafter, the tension is adjusted so that the floor slab concrete 3 can be cast on the lower beam member 2, and the height is checked. Confirm the valley side height of the lower beam member 2 with
After adjusting the tension of the PC cable 17 so as to adjust the height of the PC cable 17, the height adjusting jack 32 is slowly lowered. At this time, the adjustment is performed sequentially from the PC cable 17 at the center position of the five lower beam members 2 aligned to the PC cables 17 of the lower beam members 2 on both sides, and a height adjusting jack supporting each lower beam member 2. After descending all 32, that is, temporary support 31
Is released, the tension of each PC cable 17 is adjusted again by the tension jack 32. By this adjustment, at least the weight of the lower beam member 2 and the load caused by the concrete 3 for the floor slab and the concrete 3
The required strength is given to the load of a worker or the like who rides on the floor.
Gives the strength that can be cast. By supporting the valley side of the lower beam member 2 by the tension of the PC cable 17 in this manner, as shown in FIG.
Can be removed. When finished the rack set in the shape having a lower beam member 2 pieces over a similar process is repeated all the region, set the reinforcement of the concrete 3 parts for deck for each section, butt type on both sides of one section A frame is erected, and the valley side of the lower beam member 2 is supported by a temporary support 31 as shown in FIG. 10 as necessary, and as shown in FIG.
The concrete 3 for floor slabs is cast. And when the casting is nearing the end, the PC cable is connected by the tension jack 34.
Adjust the tension of 17 and remove the temporary support 31. Similarly, concrete 3 for floor slab is cast in each section. In the state shown in FIG. 8, the lower beam member 2 is combined with the lower beam member 2 and the PC cable 17 so that the lower beam member 2 has its own weight, the load of the floor slab concrete 3 and the floor slab concrete 3.
After the PC cable 17 is stretched and adjusted to a predetermined tension, it is not necessary to support the valley side by the temporary support 31 after the PC cable 17 is stretched and adjusted to a predetermined tension. However, the temporary support 31 supports the valley side of the lower beam member 2 at the time of placing concrete.
This is to prevent the cable 17 from being stretched, and the height adjusting jack 32 is adjusted so that a part of the tension of the PC cable 17 generated at the time of concrete casting is supported by the temporary support 31. Before placing concrete, lower beam member 2
The lower beam member 2 and the concrete 3 for the floor slab are satisfactorily integrated with each other by sprinkling water on the upper surface of the slab and maintaining the wet state. ,
As shown in FIG. 10, when one section is completed, the next section is skipped to perform a staggered pattern, and concrete 3 for floor slab is poured into each section. Then, if necessary, watering curing and heat curing are performed, and after confirming that the predetermined strength has been obtained in the concrete 3 for the floor slab, as shown in FIG.
Do book tension. When the concrete for floor slab 3 is hardened, tension is applied to the PC cable 17, but no prestress is introduced since the concrete for floor slab 3 is not subjected to any displacement. For this reason, once the PC cable 17 is loosened to lower the tension or released to reduce the tension to zero, the pre-stress is introduced into the concrete for floor slab 3 by re-tensioning. The specific procedure is
The valley- side end of the PC cable 17 is once pulled out to the extent that the nut 18 can be loosened by the tension jack 34.
Then, when the tension of the PC cable 17 is reduced to zero, the nut 18 is returned to zero by loosening the nut 18 until the PC cable 17 can be completely contracted, or the nut 18 is adjusted to reduce the tension. Thereafter, the tension is again applied by the tensioning jack 34 until the tension reaches a predetermined final tension, and the nut 18 is tightened and fixed to perform the main tension, and a predetermined prestress is applied to the concrete 3 for the floor slab. In this case, the work of loosening the PC cable 17 and the work of this tension are performed for each predetermined number, for example, for each one. There are a plurality of PC cables 17 in one section, and one of the PC cables 17 is released from the tension. Since it is loosened or opened for a short time, there is no need to support using the temporary support 31. After the lower beam member 2 is erected in this manner, the concrete 3 for the floor slab is cast and the plurality of lower frame members 2 are integrated. After the concrete 3 for the floor slab hardens, the PC cable 17 is post-tensioned. The main tension is applied by the method and a predetermined tension is applied, and the prestress of the PC cable 17 by the post-tension method and the pre-stress of the PC steel material 11 by the pre-tension method or the post-tension method are further combined with the lower beam member 2. The main girder can be integrated with the concrete for floor slab 3
27 is given a predetermined structural strength. That is, a predetermined structural strength is given to the cantilever type shed against the roof 1, the sand cushion 18, the surrounding block 17, the worker and the like, and a predetermined falling rock load. After the PC cable 17 is fully tensioned, the surrounding block 25 is attached to the upper part of the main girder 27, and the sand cushion 26 is laid. In addition, when the temporary support 31 is removed after the concrete for floor slab 3 is hardened, that is, the concrete for floor slab 3 is supported while both ends of the lower beam member 2 are supported.
Even when the concrete is hardened, no tension is applied by the PC cable 17 to the concrete 3 for the slab after the hardening, so the PC cable 17 is temporarily loosened to lower the tension or released to reduce the tension to zero. After that, the prestress can be introduced into the concrete for floor slab 3 by re-tensioning.

As described above, in the present embodiment, the lower beam member 2 made of precast concrete to which the prestress is applied in the width direction of the road by the PC steel material 11 and the concrete is integrally cast on the lower beam member 2. And a PC cable 17 provided between the valley side of the lower beam member 2 and the mountain side of the road so as to be diagonally upward toward the mountain side and applying a prestress to the floor slab concrete 3. Therefore, the lower beam member 2 to which prestress has been applied is temporarily provided at the site, and the lower beam member 2 is used instead of the formwork to cast concrete 3 for the floor slab. A prestress can be applied to the slab concrete 3 by the PC cable 17 to form a cantilevered shed. In addition, the prestress applied to the lower beam member 2 and the slab concrete 3
A predetermined structural strength can be given to the cantilevered shed by the combined force with the prestress given to the cantilever.

As described above, in this embodiment, the concrete lower beam member 2 prestressed in the width direction of the road with the PC steel material 11 is manufactured at the factory, and the support wall 4 is constructed along the mountain wall. Then, a plurality of lower beam members 2 are fixed to the support wall 4 and the plurality of lower beam members 2 are arranged side by side in the road length direction. A PC cable 17 that is inclined obliquely upward is stretched, concrete 3 for floor slab is cast on the upper part of the lower beam member 2, and after the concrete 3 for floor slab hardens, the tension of the PC cable 17 is relaxed. Since the prestress is applied to the floor slab concrete 3 by the main tension, the predetermined prestress is effectively applied to the floor slab concrete 3 by loosening the PC cable 17 and then performing the main tension. And loosen the PC cable 17 every predetermined number It is not necessary to use the temporary support 31 in a cantilevered state since the main tension is performed later. A predetermined structural strength can be given to the shed by the combined force of the prestress applied to the lower beam member 2 and the prestress applied to the concrete 3 for the floor slab.
The cross section of the road can be reduced in size and its structural strength can be effectively increased, and there is no need to provide a structure on the valley side, and the entire upper part of the road can be covered. Further, since the lower beam member 2 manufactured at the factory is relatively small and light, the installation work on the site is easy and the workability is improved. Since the concrete 3 for floor slab is cast, the mold for the concrete for floor slab 3 becomes unnecessary, and the construction cost can be reduced. Moreover, the concrete 3 for the floor slab makes it possible to use gibber reinforcing bars.
The plurality of lower beam members 2 are integrated through the intermediary of the main beam 27, and high strength is obtained in the main girder 27.

Also, as an effect of the embodiment, a PC cable
After the tension of the PC cable 17, the valley side of the lower beam member 2 is supported by the tension of the PC cable 17 to remove the temporary support 31. Therefore, the valley side of the lower beam member 2 is supported by the PC cable 17. by, becomes unnecessary temporary支保Engineering 31 of the valley side on the rack after casting the lower beam member 2, traffic stopped due to the construction work can be minimized. in addition, all other under a beam member 2 and floor work It can be performed on the plate concrete 3. Further, it is possible to a PC cable 17 which imparts pre-stress to the slab concrete 3 by the tension, which also serves as a support for the lower beam member 2 valley racks設時.

Further, as an effect of the embodiment, after the PC cable 17 is stretched, the valley side of the lower beam member 2 is supported by the tension of the PC cable 17, and the cantilever fixed at one end to the tension of the PC cable 17 is provided. Since it gives the strength that allows the concrete 3 for floor slab to be cast on the lower beam member 2 in the state,
After the PC cable 17 is stretched, there is no need to support the lower beam member 2 with the valley side. Further, in response to a moment generated in the cantilevered main girder 27, the lower beam member 2 is directed downward toward the mountain side, and the upper surface of the concrete for floor slab 3 is formed upward toward the mountain side. By increasing the section height of the section toward the hill side, a structure excellent in strength against the moment can be obtained. In addition, cantilevered main girder 27
A tensile force acts on the upper part of the cross section, but since the PC cable 17 is embedded in the upper part of the concrete 3 for the floor slab, the tensile strength of the PC cable 17 acts on the tensile force, so that the structural strength can be effectively increased. . Further, by integrating the plurality of lower beam members 2 in the length direction of the road with the laterally tightening PC steel material 10, the strength of the roof 1 is increased, and even if the predetermined number of PC cables 17 are loosened during construction, The main girder 27 does not bend,
After this, you can get nervous well. Further, the PC cable 17 is disposed obliquely with respect to the lower beam member 2, one end of which is inserted into the beam member 2 at the valley side of the lower beam member 2, and the other end of the PC cable 17 is connected to the beam fixing portion. When the beam fixing portion 6 is set as a reference point of moment by fixing to the supporting wall 4 at an interval from the distance 6, when the tension of the PC cable 17 is balanced with the load on the roof 1 and the load from the falling rock, etc. The PC cable 17
And the strength of the main girder 1 can be improved effectively. Further, since the upper horizontal beam portion 10 has a fixing surface 10A orthogonal to the duct 14 at substantially 90 degrees,
The tension of the C cable 17 can be effectively applied to the concrete 3 for the floor slab. Furthermore, on the tip side of the lower beam member 2,
A recess 15 having an open upper part of the valley side is formed.
By arranging the valley-side end of the cable 17, the work of tensioning the PC cable 17 by the tensioning jack 34 can be easily performed from the upper surface side of the lower beam member 2, and the ridge-side end of the PC cable 17 is supported. The cable protrudes from the rear surface of the wall body 4 and the protruding mountain side end is fixed by a fixing device 20 such as a nut.
17 can be easily installed. Furthermore, since there are no pillars on the valley side, it is full of open feeling and does not hinder the driver's field of view. Since the lower surface of the lower beam member 2 faces upward toward the valley side, the lighting is excellent.

The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the present invention. For example, the size, size, shape, etc. of the lower beam member can be appropriately selected. Further, the main girder of the present invention is not limited to rock fall and traffic load depending on its use conditions,
A load such as an avalanche may be considered. Further, in the embodiment, the example in which the PC cables are loosened one by one and the tension is applied is shown. However, two or more cables may be loosened at a time according to the number of PC cables per section and the tension may be applied. Good. Further, in FIG. 5, the lower beam member 2 is suspended and supported by the crane 33, and the lower beam member 2 is fixed to the support wall 4 via the anchor bolt 21 without providing a temporary support on the mountain side. After stretching the PC cable 17 and crane 33
May be removed, and the valley side of the lower beam member 2 can be supported by various means instead of the temporary support 31.

[0020]

According to the first aspect of the present invention, the cantilevered shed is
A precast concrete lower beam member prestressed in the width direction of the road with PC steel, a concrete for floor slab formed by integrally casting concrete on the lower beam member, and a valley of the lower beam member And a PC cable that is provided diagonally upward toward the mountain side and applies a prestress to the concrete for floor slab, between the side and the mountain side of the road, and it is necessary to provide a structure on the valley side. And can provide a cantilevered shed that can cover the entire upper part of the road.

According to a second aspect of the present invention, there is provided a construction method comprising:
A concrete lower beam member prestressed in the width direction of the road with steel is manufactured at the factory, a support wall is constructed along the wall of the mountain, and the mountain side of the lower beam member is fixed to the support wall. A plurality of PC cables are arranged in parallel in the length direction of the road, and a PC cable is formed between the valley side of each of the lower beam members and the support wall so as to face obliquely upward toward the mountain side. The concrete for floor slab is cast on the upper part, after the concrete for slab is hardened, the tension of the PC cable is relaxed, and then the main tension is applied to apply prestress to the concrete for floor slab. There is no need to provide a structure on the valley side, road traffic can be ensured during construction, and a cantilevered shed construction method that can cover the entire upper part of the road can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a sectional view of a main girder showing a preferred embodiment of the present invention in a road length direction.

FIG. 3 is an enlarged side view of a valley side of a lower beam member showing one embodiment of the present invention.

FIG. 4 is an enlarged plan view of a valley side of a lower beam member showing one embodiment of the present invention.

FIG. 5 is a cross-sectional view illustrating a construction procedure according to an embodiment of the present invention.

FIG. 6 is a sectional view illustrating a construction procedure according to an embodiment of the present invention.

FIG. 7 is a cross-sectional view illustrating a construction procedure according to an embodiment of the present invention.

FIG. 8 is a cross-sectional view illustrating a construction procedure according to an embodiment of the present invention.

FIG. 9 is a cross-sectional view illustrating a construction procedure according to an embodiment of the present invention.

FIG. 10 is an explanatory front view of a shed showing one embodiment of the present invention.

[Explanation of symbols]

 2 Lower beam member 3 Concrete for floor slab 4 Support wall 11 PC steel material 17 PC cable 31 Temporary support

Claims (2)

(57) [Claims] 1. A precast concrete lower beam member prestressed in the width direction of the road with a PC steel material, a floor slab concrete formed by integrally casting concrete on the lower beam member, A cantilever type comprising: a PC cable that is provided obliquely upward toward the mountain side between the valley side of the lower beam member and the mountain side of the road, and applies a prestress to the concrete for floor slab. Shed. 2. A concrete lower beam member prestressed in the width direction of the road with a PC steel material is manufactured at a factory, a support wall is constructed along a mountain wall portion, and a mountain side of the lower beam member is formed. A plurality of fixing members are fixed to the support wall and are arranged side by side in the road length direction, between the valley side of each lower beam member and the support wall,
After stretching a PC cable obliquely upward toward the mountain side, placing concrete for floor slab on the upper part of the lower beam member, and after hardening the concrete for floor slab, after relaxing the tension of the PC cable A prestress is applied to the concrete for the floor slab by applying tension to the concrete for the floor slab.