JPH11264222A - Prestressed concrete footboard and manufacture of footboard - Google Patents

Abstract

PROBLEM TO BE SOLVED: To constitute a concrete footboard capable of enhancing flexural strength, capable of restraining a crack of concrete and having a footboard width of only about 1.8 to 3.0 m. SOLUTION: A riser projecting strip 22 is formed over the width directional total length on the upper surface of the inmost side 21a end part of a footboard main body 21, antislipping grooves 23, 23 are formed on the upper surface of this side 21b end part, and a draining groove 24 is formed on the under surface of this side 21b end part to constitute a footboard 20 having a width L. The other side of a nut member 13 exposed to the width L directional end surface of a footboard 20 is exposed, screw holes 25, 25 are formed, and a welding wire net is embedded along an outside surface shape of the footboard main body 21 and the riser projecting strip 22. A tension member 8 by introducing stress (about 10 to 30 kgf/cm<2> to a cross section of the footboard), is embedded over the whole width in the footboard 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prestressed concrete tread and a method for manufacturing the tread.

[0002]

2. Description of the Related Art In the case of a steel frame staircase, a tread is formed by welding a checker plate made of a checker plate and welding a steel plate girder, or welding a steel plate having a recess formed therein and filling the recess with mortar. Was. In another technique, the tread is made of precast concrete (hereinafter referred to as "PCa") and is fixed to a steel plate girder with bolts or the like.

[0003]

In buildings used by an unspecified number of people, such as large stores, station buildings, theaters, stadiums, and the like, stairs of a required width according to the floor area and the number of people are required. . When the width of the tread is wide, the conventional tread has the following problems.

On the welding stairs, in the case of a checker plate, noise caused by walking, generation of rust when used outdoors, and design defects have been caused because welding marks are visible on the surface. Also,
In the case of the mortar filling type, rust was generated, and the non-slip fittings were worn or dropped due to walking by a large number of people. In order to prevent rust, it is conceivable to hot-dip galvanize the treads, but it takes time to transport to the plating factory, and the stairs are too large to be put into a general plating tank. was there.

[0005] Further, in the case of PCa, even when a reinforcing material is embedded, the strength of concrete is limited, and even when fiber-reinforced concrete is used, the width is about 2 m. Also, if you increase the thickness, you can make it somewhat wider,
There has been a problem in that the increase in weight causes a transportation obstacle, and the design has a problem in that it is difficult to settle down. In addition, when the shape is wide and wide, cracks are liable to occur, and there is a problem that the tread is broken at the time of transportation, assembling stairs, or mounting at the site. Further, once cracks occur, there is a problem that the resilience is poor, cracks are noticeable, and rust is generated on the internal reinforcing material (reinforcing bar, wire mesh, metal fiber, etc.).

[0006]

According to the present invention, however, the above-mentioned problem has been solved by embedding a tension member in which stress is introduced over the entire width of the tread.

[0007] That is, the present invention is a prestressed concrete tread, wherein a tension member to which stress is introduced is buried over the entire width of the tread. Further, in the above, the tread is a lower surface of the front end of the plate-like tread body,
Alternatively, it is desirable to form a rising ridge over the entire length in the width direction on the upper surface of the rear end. Further, it is desirable to embed a reinforcing wire mesh in the cross section of the tread plate along the outer shape. Further, it is desirable that the threaded surfaces of the nut members embedded along the width direction face both end surfaces in the width direction.

The present invention also provides a mold having a sectional shape corresponding to the sectional shape of a tread to be manufactured and having a concave portion having a predetermined length in the width direction of the tread, for each required tread width. A partition plate capable of partitioning the frame is arranged, and then, over the entire length in the concave portion, a predetermined tension member is disposed through the partition plate, and the tension member is pulled with a predetermined tension, and then, A method for manufacturing a tread, characterized in that concrete is filled in a concave portion of a formwork, and after the concrete is solidified, the tension member is loosened, and the tension member is cut for each partition plate to introduce tension into the solidified concrete. is there. Furthermore,
In the above, it is desirable to temporarily fix a nut member having screw holes for attaching a slab girder on both surfaces of the partition plate in the longitudinal direction of the concave portion.

[0009] The tension members in the above are various PC steel materials, and a steel wire, a steel rod, a steel stranded wire, carbon fiber, aramid fiber or the like is appropriately selected and used.

The nut member in the above is a member for forming a screw hole so that a bolt for attaching the tread plate to the slab can be screwed. For example, a long nut or a structure in which a steel rod is connected to the other side of the long nut.

The width of the stairs in the above is mainly 1.8 m to
The target is about 3.0 m.

The tension in the above is usually about 10 to 30 kgf / cm ^{2 with} respect to the cross section of the tread.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a forming mold, concave portions having a cross-sectional shape corresponding to the cross-sectional shape of a tread to be manufactured and having a length several times the width of the tread are formed in parallel. . The inside of the concave portion can be partitioned by a partition plate according to the required tread width.

A tension member is disposed through the partition plate over the entire length in the recess, and the tension member is pulled. Reinforcing members such as necessary wire mesh and lattice reinforcement are arranged, and concrete is filled in the recesses of the formwork. The concrete is solidified by steam curing. After that, loosen the tension member, cut each partition plate, introduce tension into the solidified concrete,
Demold and take out the tread (solidified concrete).

[0015]

Embodiment 1 An embodiment of the present invention will be described with reference to FIGS.

The molding form 1 used in the embodiment of the present invention comprises:
Two recesses 2, 3 having a cross-sectional shape corresponding to the cross-sectional shape of the tread to be manufactured are formed continuously and in parallel in the width direction of the tread. The depressions 2 and 3 are composed of depression main bodies 2a and 3a forming the base of the tread plate and deep depressions 2b and 3b forming the riser portion of the tread plate. Also, the concave body 2a, 3a
The convex members 4 and 4 for forming the non-slip groove 23 are incorporated in the groove.

Further, a holding mold 6 having projections 5, 5 for forming a drain groove 24 on the lower surface of the tread plate is used in combination. The convex portions 5, 5 are arranged in the concave portions 2, 3 respectively by the holding mold frame 6.

(1) Four PC steel wires (stranded wire: 2.9 mm SWPD3) 8 are evenly arranged (pitch: 100 mm) over the entire length in the recesses 2 and 3 of the forming mold frame (pitch: 100 mm). The PC steel wires 8, 8 are locked to abutments (tension reaction force tables, not shown) arranged outside both ends in the length direction of the PC steel.

(2) Each of the PC steel wires 8, 8 is tensioned at 1 ton.

(3) A reinforcing wire mesh (φ3.2 mm, width direction ＠ 50 mm) 9 is arranged in the recesses 2 and 3 of the forming mold frame.
The partition plates 11, 11 are inserted into the concave portions 2, 3 of the molding form for each required length (width of the tread plate), and the concave portions 2, 3 are inserted in the longitudinal directions 2A, 2B,. , ...). The partition plate 11 is provided with a support plate 12b along the outer periphery of the partition body 12a corresponding to the cross-sectional shape of the concave portion so as to maintain a right angle position (FIG. 10A).
(B)). Further, a through hole 18 for inserting the PC steel wire 8 and a through hole 19 for locking the nut member 13 are formed in the partition body 12a (FIG. 10B).

(4) The nut members 13, 13 are temporarily fixed in the through holes 19 of the partition plates 11, 11 of the forming mold frame 1 in the longitudinal direction. The nut members 13, 13 have a reinforcing steel bar 15 inserted into one side of the long nut 14, and the other side edge is separated from the partition plate 1.
It is in contact with 1. In addition, a holding form 6 is provided on the upper end of the forming form.
Install. In the figure, reference numeral 17 denotes a side frame.

(5) Concrete is poured into the recesses 2 and 3. The material of this concrete consists of cement, kneading water, fine aggregate, coarse aggregate, water reducing agent, etc.
Slump: 8 ± 2.5 cm, water cement ratio: 38%, unit cement amount: about 400 kg / m ³ .

(6) After finishing the trowel, predetermined curing is performed. When the curing is completed, the tension of the abutment is relaxed and prestress is introduced. The PC steel wires 8 are cut for each partition plate 11.

(7) When the member is taken out of the molding frame 1 and subjected to edge treatment, the tread plate 20 of the present invention is completed.
2, FIG. 4 (a)).

The tread plate 20 is located on the back side 21 of the tread plate main body 21.
a, on the upper surface of the end a, over the entire length in the width direction,
Are formed, and non-slip grooves 23 are formed on the upper surface of the end of the near side 21b, and a drain groove 24 is formed on the lower surface of the end of the near side 21b.

Further, the other side of the nut member 13 exposed at the end surface in the width direction of the tread is exposed, and screw holes 25, 25 are formed. Further, the tread plate main body 21 and the riser ridge 22 are provided.
The welding wire mesh 9 is buried along the outer surface shape of.

The use of the tread 20 of the present invention is the same as that of the conventional tread.

For example, the treads 20, 20 are arranged in a step-like manner, and this
And bolts 28, 28 are screwed into screw holes 25, 25 of each tread plate 20, 20 from the side of the slab girder 27, and the stairs 30.
Is configured. Numeral 29 in FIG. 3 denotes a landing member constituting the landing.

The tread 20 of the stairs 30 can easily form a wide stair having a length of about 2500 mm without supporting the tread 20 at an intermediate position in the width direction.

In the above embodiment, four PC steel wires 8 were used.
As long as the steel wires do not interfere, the number of wires does not matter. For example,
A total of eight PC steel wires 8, 8 can be evenly arranged in the upper and lower two stages (FIG. 4 (b)).

[0031]

[Test Example] Referring to FIGS.
0 and the conventional tread plate 32 are compared by a bending test.

The tread of the present invention is manufactured according to the first embodiment. The outer diameter of the tread is L (= 2,500 mm) and D (= 340 m) as shown in FIG.
m), the height (thickness) of the tread body H (= 80 mm), the overall height H ₁ (= 160 mm) including the riser, and the thickness (depth) D ₁ (= 40 mm) (FIG. 12A, FIG. 1).

On the other hand, in the conventional precast tread 32, the outer diameter of the tread 20 is the same, and it is finished by the same curing (FIG. 12B). The precast tread 32 does not introduce prestress and uses fiber reinforced concrete.

Here, the concrete material is composed of cement, kneading water, fine aggregate, water reducing agent, steel fiber, etc., and its composition is as follows: slump: 7 ± 2 cm, water-cement ratio: 39
%, Unit cement amount: 600 kg / m ³ , fiber mixing ratio:
It is about 1% (volume ratio).

A φ16 round steel bar is buried in the conventional precast tread plate 32 over substantially the entire length in the width direction (L direction), and a high nut (M1
6) are fixed respectively, and the end face (opening edge of the screw hole) of the high nut is exposed to the portion. Also, inside the tread body, φ
A mesh bar (□ 100 mm) made of the reinforcing bar of No. 6 is embedded (FIG. 13).

As shown in FIG. 14, each specimen (tread plate 2
0, 32) with bolts to support side plates (thickness 12
mm. (Sarasashi sashimi) 34, 34 are fixed, the central part is pressed by a pressing plate 35, and the strain is measured with a strain gauge attached to the lower surface of the test specimen.

As shown in FIG. 15, the conventional precast tread 32 has an initial crack at a load of 400 kgf, a large deflection due to an increase in the load P, and a maximum load of 130.
It was 0 kgf, the restoring force after removing the load P was poor, and the residual deflection was 30 mm.

The tread 20 of the present invention has a load of 800
The initial crack occurs at kgf, and the deflection caused by the increase of the load P is smaller than that of the conventional precast tread 32.
With a maximum load of about 1900kgf (deflection about 30mm),
The restoring force after removing the load P was rich, and the residual deflection was 5 mm.

[0039]

Embodiment 2 Another structure of the tread of the present invention will be described with reference to FIGS. In this case, of course, the cross-sectional shapes of the concave portions 2 and 3 of the molding frame 1 are also formed correspondingly (not shown).

The tread plate 20 is made of the rising ridge 2 of the first embodiment.
2 can be formed low (FIG. 5A).
(B)). In this case, a gap is formed between the upper and lower treads 20, 20, and light can be collected (FIG. 5C).

In the above-described embodiment, the riser ridge 22 is formed on the upper surface of the tread plate main body 21;
(See FIG. 6).

Further, it is also possible to form treads in which kick-up ridges 22 are formed on the edge of the back side 21a of the upper surface of the tread plate main body 21 and the edge of the front side 21b of the lower surface, respectively (FIG. 7).

Further, in the above-described embodiment,
Although the reference numerals 2 and 22a are formed at the edge of the tread main body 21, the tread 20 may be formed with a kick-up ridge 22a formed at the center of the lower surface of the tread main body 21 (FIG. 8).

Furthermore, it is also possible to omit the riser ridges 22 and form the plate-like tread 20 only from the tread body 21 (FIG. 9).

[0045]

The tread of the present invention is excellent in bending strength, and even if the width of the stairs is about 1.8 to 3.0 m, the tread can be held at both ends without increasing the weight by suppressing the increase in thickness. There is an effect that stairs can be constructed only by support. Further, even if a crack occurs, the bending is suppressed by the tension of the tension member, and there is an effect that the crack is not noticeable and the repair is easy. Therefore, there is an effect that the range of use of the concrete tread having advantages such as quiet walking sound and no rust can be greatly expanded.

Further, according to the manufacturing method of the present invention, if the length of the concave portion is made sufficiently longer than the length of the step, there is an effect that a large amount can be produced at a time on a long line. Further, by adjusting the partition plate, tread plates having the same cross section and different stair widths can be manufactured at the same time, and the manufacturing efficiency can be increased.

Further, since the nut member for fixing to the girder is temporarily fixed to the partition plate as a separate member, the tread plate can be manufactured without preparing a member for each different width or different cross-sectional shape of the tread plate to be manufactured. Can be made more efficient.

[Brief description of the drawings]

FIG. 1 is a plan view of a prestressed concrete tread according to the present invention, in which (a) is a plan view, (b) is a front view, and (c) is a right side view.

2A is an enlarged sectional view taken along line AA of FIG. 1B, and FIG. 2B is an enlarged sectional view taken along line BB of FIG. 1B.

FIG. 3 is a perspective view illustrating a configuration of a stair using a tread plate.

4A is an enlarged side view of a tread plate, FIG. 4B is an enlarged side view of a tread plate showing an arrangement of another PC steel wire, and FIG. 4C is a partial longitudinal sectional view showing an attached state.

5A and 5B are examples of treads having other shapes, (a) is an enlarged side view of the tread, (b) is an enlarged side view of the tread showing an arrangement of another PC steel wire, and (c) is an attached state. FIG.

FIG. 6 is an embodiment of a tread having another shape, (a) is an enlarged side view of the tread, (b) is an enlarged side view of the tread showing an arrangement of another PC steel wire, and (c) is an attached state. FIG.

FIG. 7 is an embodiment of a tread having another shape, (a) is an enlarged side view of the tread, (b) is an enlarged side view of the tread showing an arrangement of another PC steel wire, and (c) is an attached state. FIG.

8 (a) is an enlarged side view of the tread plate, FIG. 8 (b) is an enlarged side view of the tread plate showing the arrangement of other PC steel wires, and FIG. FIG.

FIG. 9 is an embodiment of a tread plate having another shape, (a) is an enlarged side view of the tread plate, (b) is an enlarged side view of the tread plate showing an arrangement of another PC steel wire, and (c) is an attached state. FIG.

FIG. 10A is a partial plan view of a molding die frame used in the embodiment of the present invention, and FIG. 10B is an enlarged cross-sectional view taken along line DD of FIG. is there.

FIG. 11 is an enlarged cross-sectional view taken along line CC of FIG.

12 (a) is a schematic perspective view of a test piece of a tread of the invention, and FIG. 12 (b) is a schematic perspective view of a test piece of a tread of a conventional example.

13 (a) is a plan view of a tread board of a conventional example, in which (a) is a partially cutaway plan view, (b) is a front view, and (c) is a right side view.

FIG. 14 is a diagram illustrating a bending test method in a test example.
(A) is a front view, (b) is a cross-sectional view taken along line EE of (a).

FIG. 15 is a graph of “load-deflection” comparing the bending properties of the test results.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Forming mold 2 Concave part 3 Concave part 6 Holding form frame 8 PC steel wire 9 Welding wire net 11 Partition plate 13 Nut member 17 Side frame 20 Tread plate 21 Tread plate body 22 Kick-in ridge 27 Sasa girder 30 Stairs 32 Tread plate (conventional example)

 ──────────────────────────────────────────────────続 き Continuing from the front page (71) Applicant 595109959 Cleo Co., Ltd. 1-28-23 Hongo, Bungo-ku, Tokyo Yumichi Chichibu Building (72) Inventor Tatsuo Suenaga 2-9-1-1, Tobita Supplier, Chofu-shi, Tokyo Kashima Construction Co., Ltd.Technical Research Institute (72) Inventor Akihiko Kodama 2-4-2, Daisaku, Sakura-shi, Chiba Prefecture No. Chichibu Onoda Noda Co., Ltd. (72) Inventor Sebun Yokomori 1-29-1 Hatagaya, Shibuya-ku, Tokyo Inside Yokomori Seisakusho Co., Ltd. (72) Inventor Masanori Kikuchi 1-2-28 Hongo, Bunkyo-ku, Tokyo Cleo Co., Ltd.

Claims (6)

[Claims] 1. A prestressed concrete tread, wherein a tension member to which stress is introduced is buried over the entire width of the tread. 2. The prestressed concrete tread according to claim 1, wherein the tread has a kick-up ridge extending over the entire length in the width direction on a lower surface of a front end portion or an upper surface of a rear end portion of the plate-like tread body. 3. The prestressed concrete tread according to claim 1, wherein a reinforcing wire mesh is embedded along the outer shape in a cross section of the tread. 4. The prestressed concrete tread according to claim 1, wherein the threaded surface of the nut member embedded along the width direction faces both end surfaces in the width direction. 5. Forming a mold for each required tread width in a form having a cross section corresponding to a cross section of a tread to be manufactured and having a concave portion having a predetermined length in the width direction of the tread. And a predetermined tensioning member is disposed through the partitioning plate over the entire length of the recess, and the tensioning member is pulled with a predetermined tension. A method of manufacturing a tread plate, comprising filling concrete into the concrete, solidifying the concrete, loosening the tension member, cutting the tension member for each partition plate, and introducing tension into the solidified concrete. 6. The tread plate manufacturing method according to claim 5, wherein a nut member having a screw hole for attaching a girders on both sides of the partition plate is temporarily fixed in a longitudinal direction of the concave portion.