JPS6151524B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for manufacturing embedded formwork used for constructing floor slabs at construction sites.

(Conventional technology) Embedded formwork is a type of formwork that is made of concrete slabs and poured in-situ concrete on top of it, eliminating the need for conventional formwork assembly, disassembly, and movement. It is an effective means of shortening concrete construction time and reducing labor.

In particular, PC concrete slabs made on pretension benches have pretension remaining on the underside of the completed slab, improving the strength of the slab, and are recognized as embedded formwork that can kill two birds with one stone.

(Problems to be Solved by the Invention) This invention is capable of creating its own structure by adding a hollow protrusion with a hollow interior to the top surface of the short PC concrete slab having pretension as its embedded formwork. We came up with the idea that increased rigidity would simplify shoring, increase the effect of reinforcing the slab, reduce the amount of cast-in-place concrete, and reduce the weight of the slab, and we set these as development goals.

(Means for solving the problem) This invention runs a sliding type concrete forming device on a long pretension bench, and forms a flat or upper surface with a length that can take a plurality of embedded formworks. A process of forming a long PC concrete slab with parallel ridges, a dividing process of dividing the PC concrete slab according to the length of the embedded formwork to create short PC concrete slabs of a predetermined length, and the above Almost the entire top surface of each short PC plate is covered with thin-walled cocrete whose size and shape form a hollow in the longitudinal direction.
Placed as ready-made strips or post-cast concrete,
This method of manufacturing an embedded formwork is characterized by comprising the step of fixing it to the short PC plate using bolts, adhesive, or dowel bars.

(Function) In this invention, the embedded formwork, which was conventionally merely a receiving plate for cast-in-place concrete, is constructed by adding a tall reinforcing bone called a hollow protrusion to the short PC concrete slab, and constructing the formwork. By reducing the number of shoring structures, the hollow protrusions remain as cavities to reduce the weight of the slab when the slab is completed, making it possible to easily cast and form lightweight slabs without the need for core work.

Then, the PC that becomes the embedded formwork with hollow protrusions
The manufacturing method for concrete slabs does not rely on conventional techniques for making hollow concrete products, but instead we have developed a manufacturing method that is optimal for construction site planning and embedded formwork, which is essential.

In other words, embedded formwork for deck slabs is most often used in the construction of concrete bridges, but the construction work is intermittent, and the required dimensions (mainly length) of the embedded formwork change for each construction, and once construction begins. There was a need to rapidly manufacture a large amount of embedded formwork and send it to the construction site, and in terms of strength, the embedded formwork that would become the bottom surface of the floor slab had to be pretensioned along its bottom surface. The reason is that it is only necessary to line up the PC steel wires, and there is no need to insert the PC steel wires into the hollow protrusions on the top surface. In response to the unique conditions of embedded formwork, the present invention has been developed by making a long PC concrete slab with PC steel wires arranged on a pretensioning bench in advance, and then forming a hollow hollow without pretensioning. For the projecting strips, after determining the dimensions of the embedding formwork, we placed the long PC concrete slabs above as ready-made strips or post-cast concrete onto short PC concrete slabs and fixed them in place.

Long PC concrete slabs, which are important for strength and require troublesome pretensioning work, take a sufficient amount of time to be made, and are kept on standby so that they can be cut into the required dimensions at any time.Once the dimensions of the embedded formwork have been determined, they can be prepared immediately. This is divided into short PC plates, and hollow protrusions are created by simply placing strips or post-cast concrete on top of them.

(Example) Figures 1 and 2 are PCs for embedded formwork according to the present invention.
The cross sections of two examples 1 and 2 of the concrete slab are shown.
Of course, the entire length is the same plane, and pretensioned steel materials 7 with different diameters are arranged approximately evenly across the entire width, and in this case, a welded wire mesh 8 is incorporated throughout.

While PC concrete version 1 is flat,
PC concrete version 2 has parallel protrusions 3 added to the top surface of an almost flat surface, but other aspects remain the same.

FIG. 3 is a sectional view showing an embodiment of the embedded formwork according to the present invention, in which a flat strip material 4 is fixed by covering the parallel protrusions 3, 3 of a PC concrete slab 2 cut into short lengths. be. FIG. 4 shows an example in which a groove-shaped strip 5 is covered instead of a flat strip. It is sufficient to cover the PC concrete slab 1 shown in Fig. 1 with the channel-shaped strip 5 shown in Fig. 4. In any case, by adding strips to the short PC concrete slab, it becomes an embedded formwork with hollow ridges along almost the entire length of the top surface. Of course, the height of the hollow protrusion is not higher than the planned thickness of the cast-in-place concrete F. The hollow parts 6 of the hollow protrusions are not harmful to the bending strength of the concrete slab when it is completed.
The volume must be effective for weight reduction.

In order to compare the strength of completed slabs with and without hollow protrusions on the PC slab as shown in Figures 3 and 4, the first , In addition to the case where short PC concrete slabs 1 and 2 in Figure 2 are used as embedded formwork and concrete is cast on site, the strength of the slab due to the embedded formwork in Figures 3 and 4 is calculated as follows: Let's find the moment at which the prestress (compression) becomes zero. In both cases, the formwork width W is 1000 mm, the thickness of the bases 1 and 2 is 40 mm, the height of the protrusion 3 is 50 mm, the top width is 100 mm, the horizontal part thickness of the flat strip 4 and the groove strip 5 is 30 mm, and the floor slab In order to determine the total thickness as the actual thickness, the values are calculated sequentially starting from Figure 1.
100, 120, 150, 200mm.

Different diameter PC steel materials (diameter 10 mm, 6
The prestress on the upper and lower surfaces due to
Kg/cm ² , and the bottom surface is about +69Kg/cm ² .

The moment Mo that makes the compressive stress on the lower surface zero
are 166, 632, 1504, and 2825 kg-m in order from Figure 1. This shows that by appropriately combining the short PC concrete slab of the present invention and the strips added thereto, the strength of the finished slab can be significantly strengthened and it can be designed over a wide range of areas.

Also, the thickness of PC concrete plate 2 in Figure 2 is 60
When making a floor slab with a thickness of 150 mm and a ridge height of 60 mm, it is possible to cast unsupported concrete with a span of up to 5 m, but the PC concrete slab 2 has a thickness of 50 mm.
When the flat strip 4 of
In addition to being 2.7 times larger, the weight is 52.5 because it is a hollow floor slab.
Kg/ ^m2 reduced. This makes it possible to install floor slabs with a thickness of 200 mm up to a span of 7.5 m without shoring. A floor slab that can withstand a live load of 347 kg/ ^m2 is completed without adding reinforcing bars on site. If you want to further increase the bending strength against loads, you can place additional reinforcing bars on-site at the joints with the adjacent embedded formwork.

Also, the thickness of PC concrete plate 2 in Figure 4 is 60
mm, the height of the protruding strip 3 is also 60 mm, and the height of the channel strip 5 is 120 mm.
mm, and the thickness is 50mm, the above Mo is 6450Kg
- m, it is possible to construct without shoring up to 9 m with a floor slab thickness of 300 mm.

When this is used as an embedded formwork for a second-class road bridge, if the bridge length is 5m, a prestress of 53Kg/ ^cm2 remains on the bottom surface, and even if a design live load moment is applied, there is still a compressive stress of +1Kg/ ^cm2. remains. In other words,
This is a pre-stressed PC composite floor slab. This creates an ideal state in which almost no tensile stress occurs within the cross section.
In calculations, the design moment produces a tensile stress of -18Kg/ ^cm2 on the bottom surface of the deck slab (substrate), and a tensile stress of -39, -64, and -90Kg/ ^cm2 for bridge lengths of 7, 8, and 9m, respectively. , it becomes necessary to reinforce with reinforcing bars. i.e. R.C.
It will have a floor slab structure. In this case, the prestressed steel, reinforcing bars, wire mesh, and reinforcing bars added on site work in accordance with the effective height of the embedded formwork.

Therefore, the designer can appropriately select the cross-sectional shape of the PC concrete slab according to the present invention, and design a slab bridge or other structure with the most preferable stress state, including the cast-in-place concrete and reinforcing bars to be mounted thereon.

Regarding cracks on the bottom surface, which is a problem, when PC concrete slabs are used as embedded formwork for RC deck slabs, numerous experimental results show that the calculated tensile stress on the bottom surface of the slabs is approximately -100Kg/ ^cm2 . to,
No visible cracks occur. That is, according to this invention, it is possible to design a PC floor slab that is extremely resistant to cracking. The degree of safety against cracks ranges from the above-mentioned full prestressing to partial prestressing, which allows for permissible tensile stress, or cracks that occur under the maximum load but disappear completely when the load is removed. At each stage, the appropriate safety level can be selected and designed. long PC
When making concrete slabs, if you incorporate reinforcing bars of different diameters in addition to prestressing steel, you will have both the effect of prestressing, which delays the onset of cracks, and the effect of RC, which suppresses the progression of cracks.

It is also necessary to take into consideration the lateral moment of the floor slab, which is achieved by incorporating welded wire mesh 8 as in the substrates 1 and 2 of the illustrated embodiment, and by incorporating welded wire mesh 8 in the adjacent part of the formwork as shown in Figures 5 and 6. By inserting a welded wire mesh, it can sufficiently withstand lateral moments. This is easier than the conventional method of horizontally tightening PC girders.

Next, we will explain the manufacturing method for long PC concrete slabs.

When the embedded formwork with hollow protrusions according to the present invention is manufactured by a conventional method, several meters of cores are required to create the hollow portion, which is a troublesome work. In addition, the dimensions of the embedded formwork change each time an order is received depending on the situation on site, making it impossible to make to order and resulting in large fluctuations in factory operating rates.

Therefore, the first objective of the manufacturing method according to the present invention is to enable make-to-stock production. The variable dimensions of the embedded formwork of this invention are the length as the embedded formwork and the cross-sectional dimension of the hollow protrusion, and the width is the width of the floor slab, which is made by adjoining them as shown in Figures 5 and 6. It may be constant.

The manufacturing method of this invention is to create a long PC concrete slab from which multiple ordinary embedded forms can be made and divide it into pieces according to the specified length, in order to perform make-to-stock production regardless of variations in the length of embedded formwork. I took it. Next, in order to deal with variations in the dimensions of the hollow protrusions, we decided to manufacture them separately and produce only the long PC concrete slabs that would not vary.

Specifically, as shown in Fig. 11, a sliding concrete forming device 21 is run on the bottom frame 20 of a long pretension bench ranging from several tens of meters to a hundred meters long, and the total length is A long piece that is long enough to take multiple formworks and is flat or has parallel protrusions 3 on the top surface.
The PC concrete slab is formed, cured, and kept on standby until the dimensions of the embedded formwork are determined.
Cut the PC board into specified dimensions using a well-known concrete cutting machine to make the required number of short PC boards, and either fix separately made strips 4, 5, etc. on the top of each board, or add post-cast concrete to the entire length. A hollow protrusion is formed on the surface. However, it is also possible to fix the strips to a long PC plate in advance and then divide them.

There are two ways to create hollow protrusions on the top surface of the PC concrete slab: one is to fix separately manufactured strips 4 or 5 to the PC slab 2 with adhesive, bolts, and nuts, and the other is to fix the separately manufactured strip 4 or 5 to the PC slab 2
This method involves creating formwork on top and pouring concrete. The solid lines in Figures 5 and 6 are examples of the former, where strips 4 and 5 are manufactured separately (no prestressing required) and placed over between the protrusions 3 and 3. In the case on the left side of the figure, they are produced from PC version 2 Tighten anchor bolt 9 and nut 10. It is best to apply cement mortar or resin mortar to the joint surfaces in advance. In addition, as shown on the right side of the figure, the width of the strips 4 and 5 is made slightly narrower, wire mesh 8 or reinforcing bars are made to protrude from the sides, and dowel reinforcements 11 etc. are made to protrude from the side of the PC plate 2, and post-cast concrete or mortar is made. Unify at 12.

In the latter method, a template (dashed line) 13 forming the lower and side surfaces of the strip 4 or 5 shown in the figure is attached with the upper surface of the protrusion 3 to be joined removed, and concrete is poured. Of course, the upper surface of the protrusion 3 is provided with a spiral or other dowel line in advance to strengthen the connection.

In the case of Fig. 5, the space between the parallel protrusions 3 and 3 is filled with dry sand, a vinyl sheet or the like is placed over it to serve as the template 13, and after the concrete is poured and hardened, it is tilted and the sand is poured. You can take it out.

The edges that contact the adjacent embedded formworks are the same as those of the conventional embedded formwork, but two rows of welded wire mesh 8 for joints added to the above-mentioned adjacent areas are shown in FIGS. 5 and 6.

Next, this long PC concrete slab manufacturing apparatus will be explained with reference to the embodiments shown in FIGS. 7 to 10.

This manufacturing device mass-produces long PC plates according to the manufacturing method described above. This is similar to the patent application No. 114025/1983 developed by the present inventor, ``PC Concrete Plate Manufacturing Apparatus'', and uses, for example, 50 to 100 m pretension bench equipment, as shown in the embodiment shown in Figure 11. , flat concrete material 1
4 are connected together and a steel plate is pasted on the upper surface to form a bottom frame 20, and fixing members 15 made of PC steel materials 7 of different diameters and tensioning jack mounting members 16 are connected to both ends. After applying tension to the PC steel material 7 with the jack 17, the bottom frame 2
0, concrete is poured into the bottom frame 20 intermittently, and the sliding forming device 21 is pulled by a winch (not shown) to move the bottom frame 20 from one end of the bottom frame 20 to the other end.
By sliding on the top, it is successively shaped into the desired cross section.

The parallel protrusions 3 of the PC concrete plate are on the top side that contacts the cast-in-place concrete, but when using the above-mentioned sliding forming device, if the parallel protrusions 3 are formed on the bottom frame 20 side, this method of sliding forming is also easy. It is.
However, in that case, there is the trouble of having to replace the bottom frame every time the dimensions of the protrusion 3 change.

Therefore, this device follows the sliding forming method of the previous application in which the flat part of the PC plate 2 is advanced by leveling the heaped concrete, and the parallel protrusions 3 standing on the top surface are the hopper of the sliding device itself. They adopted a composite method of pouring and forming concrete from scratch.

The main parts of the embodiment shown in FIGS. 7 to 11 are a long bottom frame 20 whose entire length is the same in cross section as shown in FIG.
5, 16, sliding forming device 2 that moves on the bottom frame 20
1, this sliding forming device 21 includes a scraper 22 that flattens the concrete poured intermittently onto the bottom frame 20, an upper frame 23 that forms the product, a vibrator 24 that vibrates these, and a vibrator 24 that vibrates them. Following the frequency converter 24a and the rear of the upper frame 23,
A ridge forming frame 25 that forms the ridges on the top surface of the product, and a concrete frame 25 provided above the front part of the forming frame 25.
Hopper 26 etc.

In this case, the bottom frame 20 consists of a bottom plate 20a laid on concrete materials 14, 14, which are fastened with PC wires on both left and right sides, and side frames 20b that also serve as left and right rails. The scraper 22 is located at the front part of the sliding forming device 21, and uses three chevron-shaped plates 22b in the front and rear directions within the U-shaped peripheral wall 22a to break up the piles of the poured concrete and spread it left and right to make it almost flat. A large number of vibration bars 22c are attached to the chevron plate 22b, which energizes the concrete stagnant in front of the chevron plate 22b. 22
d is an adjustment damper.

The concrete that has entered under the upper frame 23 from the scraper 22 becomes flat and has a thickness close to that of the PC plate 2, and then enters under the ridge forming frame 25 that follows. There, concrete for the ridge is supplied from the hopper 26, and this is supplied to the surrounding plate 2 as shown in Fig. 10.
6a to form the desired cross-sectional shape. The top surface of the product will be the bottom of the embedded mold, so it is desirable that it be a rough surface, and it is not necessary to mold it smoothly. Rather, it is desirable that this sliding forming device 21 be followed by a roller with protrusions that roughen the surface.

Although the present invention has been described above with reference to a small number of embodiments, it goes without saying that depending on the design conditions, a designer can implement various embodiments using known techniques. For example, the width of the concrete slab should not be 1m.
2m, with three parallel protrusions 3 and a protrusion hollow part 6.
It can be widely varied and applied, such as by placing them in parallel.

(Effects of the invention) By using a PC concrete slab with hollow ridges as the embedded formwork, this invention is not only a means of improving work efficiency, but also improves the strength and reduces the weight of the slab made by this. It paved the way for great work.

In other words, in terms of strength, the PC concrete slab with hollow striations, which is a reinforcement bone that is tall compared to its volume,
In addition to increasing its own bending strength, highly reliable hollow reinforcing bones are added to the underside of the slab, which can also be used as a hollow internal floor slab, and as mentioned above, the need for reinforcement work for the slab can be significantly reduced. I made it.

The following reduction in deck weight is the most important effect of this invention.

This invention replaces the conventionally strong buried formwork, which was merely a receiving plate for cast-in-place concrete, with a formwork that carries cavities (hollow ridges) to reduce the weight of the floor slab, making it possible to use cast-in-place concrete for the first time. It is now possible to obtain a defect-free cavity floor just by pouring it. This dramatically simplifies the design and construction of lightweight floor slabs.

Moreover, the manufacturing method of the PC concrete slab with hollow ridges goes against conventional wisdom and is optimized for the special circumstances of embedded formwork. In other words, floor slab construction is carried out intermittently, and once it starts, it is necessary to prepare a large amount of long products, so the embedded formwork is made separately from the PC concrete slab and hollow ridges. For PC plates that require pretension, several long plates are made in advance and cured using a long pretension bench and sliding forming device. After determining the dimensions of the buried formwork, the long PC board is divided into those dimensions, and ready-made strips or post-cast concrete are placed on top of each piece to form the required hollow protrusions, completing the buried formwork. do. Therefore, the pretension bench increases operating rates through make-to-stock production and significantly reduces the number of days from sizing to shipping. Since the cross-sectional shape of the base is simple, even if the dimensions and shape of the buried formwork change, it can be accommodated simply by changing the shape of the strips placed on top or the post-cast concrete.

In addition, unlike conventional PC concrete embedded formwork, it has hollow ridges, which adds maximum bending resistance to the formwork itself with minimal weight increase, while also reducing the weight of the floor slab. It cannot be overlooked that the need for shoring during formwork erection has been significantly reduced.

In other words, this invention provides designers with a powerful means of reinforcing and reducing the weight of concrete slabs, and allows builders to eliminate form work, drastically reduce the need for shoring and reinforcing bars, shorten construction time, and reduce costs. This will help frame manufacturers average factory operating rates, reduce costs, and shorten delivery times.

[Brief explanation of the drawing]

Figures 1 and 2 are cross-sectional views of two types of PC concrete slabs for embedded formwork according to the present invention, and Figures 3 and 4 are the above.
Figures 5 and 6 are cross-sectional views of two embodiments of the present invention, in which hollow protrusions are attached to a PC plate to form an embedded formwork, and cast-in-place concrete is poured on top of the formwork. 7 is a side view of an embodiment of the manufacturing apparatus of the present invention, FIG. 8 is a plan view thereof, FIG. 9 is a front sectional view thereof, and FIG. 10 is a perspective view of the protrusion forming frame;
FIG. 11 is a schematic diagram of the manufacturing apparatus. 1, 2...PC concrete plate, 3...Parallel ridges forming the lower part of the hollow ridges, 4, 5...Strip material forming the upper part of the hollow ridges, 6...Hollow part of the hollow ridges.

Claims (1)

[Scope of Claims] 1. A long pretension bench that is flat or has parallel ridges on its upper surface and is long enough to form multiple embedded forms by running a sliding concrete forming device on the long pretension bench. A process of forming a PC concrete plate; A dividing process of dividing the PC concrete plate according to the length of the embedded formwork to create short PC plates of a predetermined length; A process of placing thin concrete with a size and shape that forms a longitudinal hollow on almost the entire surface as ready-made strips or post-cast concrete, and fixing it to the short PC plate with bolts, adhesive, or dowel bars. The manufacturing method of embedded formwork is characterized by its characteristics.