JPH1193295A - Rupture preventive construction method of high strength reinforced concrete structure member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the rupture caused at the time of heating by fire by covering a surface of a high strength reinforced concrete structure member with a thin steel plate. SOLUTION: Reinforcements 3 and 7 are assembled by using a leveling form by a thin steel plate 2, and a surface of a high strength reinforced concrete structure member 1 is covered with the thin steel plate 2 by placing high strength concrete 4. Next, it is important that the thin steel plate 2 can endure placing pressure of the high strength concrete 4, and a rib is welded to a surface of the thin steel plate 2 as its means. Next, a change in a surface temperature of the high strength concrete 4 when the reinforced concrete structure member 1 is heated at the time of fire, shows a temperature characteristic in which a rising tendency of a surface temperature of the thin steel plate 2 and a surface temperature of the high strength concrete 4 becomes fairly slower than a rising tendency of a fire heating temperature. As a result, the surface of the high strength concrete does not rupture even if it is heated by fire.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technical field for securing fire resistance of a high-strength reinforced concrete structural member at the time of fire heating, and more particularly, a high-strength reinforced concrete structural member is generated at the time of fire heating. It relates to a method of preventing explosion.

[0002]

2. Description of the Related Art Reinforced concrete structural members (for example, columns,
Beams, walls, floors, etc.) are recognized as fire-resistant structures according to the Building Standards Law if they have a predetermined cross-sectional area and a reinforced concrete covering thickness. However, in recent years, the design standard strength (F
_C ) High-strength concrete of 600 kgf / cm ² or more has been applied to buildings. It is said that high-strength concrete is different from ordinary concrete in material properties at high temperature, and that the structure constituting the concrete is particularly dense, so that explosion tends to occur at high temperature. Explosion (a phenomenon in which the surface of concrete breaks off when exposed to high temperatures) is a unique phenomenon caused by the effect of rapid heating (thermal shock). The following two mechanisms are considered as mechanisms that cause this phenomenon.

[0003] 1) Due to rapid heating of the concrete surface, the moisture contained in the bubbles in the concrete evaporates, and the water vapor expands rapidly, destroying the concrete from the inside at once and causing explosion. 2) Due to the rapid heating of the concrete surface, a large temperature difference occurs between the vicinity of the surface where moisture evaporates in the concrete and the interior where the moisture remains, and thermal stress acts between the interior and the interior as the vicinity of the surface tries to expand. As a result, strain occurs, and a burst occurs when the proof stress limit is exceeded.

[0004] Regardless of either of the above mechanisms, it can be seen that concrete with a high moisture content tends to cause explosion. In addition, it can be understood that rapid heating by a fire is the cause of either mechanism. FIG. 5 shows the relationship between the fire time and the surface temperature of the concrete 4 for the bare high-strength reinforced concrete structural member 1 shown in FIG. Reference numeral 7 in the drawing indicates a hoop muscle wound around the main muscle 3. According to the example of FIG.
During a minute (D in the figure), the surface temperature of the concrete 4 shows a rising tendency substantially the same as the heating temperature of the fire, and the temperature rises sharply and explosion occurs in the range of 700 ° C to 900 ° C. It is shown.

[0005] When a high-strength reinforced concrete structural member explodes, the cross section of the member is deficient, and the reinforced concrete is not covered, so that the temperature rise of the reinforcing steel is accelerated and the proof strength as a structural member may be lost. Therefore, quality assurance of concrete in the event of a fire is essential. Conventionally, various methods have been proposed for preventing explosion of a high-strength reinforced concrete structural member that occurs when a fire is heated.
For example, the following are referenced. The method for preventing explosion of high-strength reinforced concrete structural members disclosed in Japanese Patent Publication No. 53-10372 discloses a method of forming paper, asbestos slate, asbestos, and gypsum board on the heating surface side of high-strength reinforced concrete structural members with a lower rigidity than high-strength concrete. In this configuration, a plate made of a soft material such as plastic is embedded at a required interval (5 to 200 mm) in a direction in which the surface of the plate is orthogonal to the surface of the high-strength concrete. The method of preventing explosion of a high-strength reinforced concrete structural member disclosed in Japanese Patent Application Laid-Open No. 3-122338 is a chamotte that is hardly neutralized, has heat insulation properties, and does not cause explosion on the heating surface side of the high-strength concrete structural member. Alternatively, a mortar layer obtained by mixing an emulsion resin with vermicilite is several c.
This is a construction method in which the material is cast in advance by a thickness of m and then the high-strength concrete of the member body is cast.

[0006]

Considering the mechanism of the explosion based on the relationship between the surface of the high-strength concrete structural member and the fire time illustrated in FIG. 5, the surface of the high-strength concrete is rapidly abruptly heated during a fire. I can come up with a measure to prevent heating. However, the explosion-prevention method of the high-strength reinforced concrete structural member described in the section of the prior art directly exposes the surface of the high-strength reinforced concrete member to fire. Further, plastic used as a soft material generates smoke and toxic gas when burned. Asbestos is becoming a carcinogenic harmful substance and is not used as a building material.
There is a drawback that the use of this increases the construction period.

In the above-mentioned method for preventing explosion of a high-strength reinforced concrete structural member, since a mortar layer is further provided on the surface of the high-strength reinforced concrete member, the section of the member becomes large, and the effective use area of the space is reduced. In addition, the wet construction method such as mortar advance placement requires a long construction time and curing, and has a disadvantage that the construction period is long. Accordingly, an object of the present invention is to prevent the surface of high-strength concrete from being rapidly heated at the time of fire heating, which is a cause of explosion, without using hazardous materials such as harmful substances as a means, and effectively using space. An object of the present invention is to provide a method for preventing explosion of a high-strength reinforced concrete structural member, which does not reduce a use area and shortens a construction period and a period of curing.

[0008]

As means for solving the above-mentioned problems, a method for preventing explosion of a high-strength reinforced concrete structural member according to the first aspect of the present invention is to reduce the surface of the high-strength reinforced concrete structural member 1 by thinning. It is characterized by being coated with a steel plate 2. In the method for preventing explosion of a high-strength reinforced concrete structural member according to the invention as set forth in claim 2, a high-strength reinforced concrete is obtained by assembling reinforcing bars 3 and 7 and casting high-strength concrete 4 using a discarded frame made of a thin steel plate 2. It is characterized in that the surface of the structural member 1 is coated with a thin steel plate 2.

A third aspect of the present invention is characterized in that the thin steel plate 2 according to the second aspect is reinforced with a plurality of ribs 5 so as to withstand the casting pressure of the high-strength concrete 4. The invention described in claim 4 is characterized in that the thin steel plate 2 according to claim 2 is reinforced by lattice bars and ribs 5 so as to withstand the driving pressure of the high-strength concrete 4.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is suitable as a method of preventing explosion of a high-strength reinforced concrete structural member caused by heating by slowing the transfer of heat to the high-strength concrete surface and the temperature rise. Will be implemented. In the method for preventing explosion of a high-strength reinforced concrete structural member according to the first aspect of the present invention, as shown in FIG. 1, the surface of the high-strength reinforced concrete structural member 1 (the surface of the concrete 4) is irrespective of the construction method. 0.8mm ~
It is characterized in that it is covered with a 3.2 mm thin steel plate 2.
The surface of high-strength reinforced concrete structural member 1 is made of thin steel plate 2
The method of covering with the above-mentioned method may be, for example, a case where the surface of the existing high-strength reinforced concrete structural member 1 is wound and coated as a retrofit, or a case where the thin steel plate 2 is previously used as a disposable form as described below for covering. .

When the high-strength reinforced concrete structural member 1 is heated in the event of a fire, the surface temperature of the concrete 4 changes as shown in FIG. In addition, the surface temperature of the concrete 4 shows a temperature characteristic in which the rising tendency is considerably slow. As a result, the surface of the high-strength concrete 4 does not explode even when heated by a fire.

The method for preventing explosion of a high-strength reinforced concrete structural member according to the second aspect of the present invention is achieved by assembling rebars 3 and 7 and pouring high-strength concrete 4 using a discarded frame made of a thin steel plate 2. This is implemented as a construction method of coating a thin steel plate 2 on the surface of the high-strength concrete structural member 1 and constructing the high-strength reinforced concrete structural member 1 as shown in FIG. Therefore, at the time of fire, the change in the surface temperature of the high-strength concrete 4 of the high-strength reinforced concrete structural member 1 exhibits the temperature characteristic shown in FIG. Does not explode when heated.

In the case of this embodiment, it is essential that the thin steel plate 2 can withstand the casting pressure of the high-strength concrete 4, and as a means therefor, it is reinforced with a plurality of ribs 5 as shown in FIGS. 2A and 2B. Is done. The rib 5 in FIG. 2A shows a case where a steel material is joined to the surface of the thin steel plate 2 by welding, and the rib 5 in FIG. 2B shows a case where the thin steel plate 2 is bent. Although not shown in the drawings, the thin steel plate 2 may be reinforced by lattice bars arranged together with the ribs 5. The thin steel plate 2 and the lattice bar are joined by welding.

[0014]

According to the method for preventing explosion of a high-strength reinforced concrete structural member according to the present invention, a thin steel plate prevents rapid heating of the surface of high-strength concrete at the time of fire heating, which is a cause of explosion. As a result, the quality of the high-strength concrete structural member is guaranteed, and the proof stress of the structural member does not decrease. In addition, since thin steel plates that are not dangerous materials such as harmful substances are used, there is no danger to everyday life in the building. Moreover, the effective use area of the space is not reduced. There is no inconvenience that the method of the present invention restricts the design plan.

According to the method for preventing explosion of a high-strength concrete structural member according to the second aspect of the present invention, since thin steel plates are used as the scrap frames, the reinforced concrete work can be rationalized, and the work period and the period of curing and the like can be improved. And the cost can be set at a low cost.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a high-strength reinforced concrete structural member embodying the present invention.

FIGS. 2A and 2B are perspective views showing examples of ribs for reinforcing a thin steel plate as a scrap frame.

FIG. 3 is a diagram showing a relationship between a concrete surface temperature and a fire time in a high-strength reinforced concrete structural member embodying the present invention.

FIG. 4 is a cross-sectional view of a conventional bare high-strength reinforced concrete structural member.

FIG. 5 is a diagram showing a relationship between a concrete surface temperature and a fire time in a conventional bare high-strength reinforced concrete structural member.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 High-strength reinforced concrete structural member 2 Thin steel plate 3 Main bar 4 High-strength concrete 5 Rib

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kenro Mitsui 1-5-1, Otsuka, Inzai City, Chiba Prefecture Inside Takenaka Corporation Technical Research Institute, Inc. (72) Inventor Akio Furuhira 1-5-1, Otsuka, Inzai City, Chiba Prefecture (72) Inventor Hirokazu Ohashi 1-5-1, Otsuka, Inzai City, Chiba Pref.

Claims (4)

[Claims] 1. A method for preventing explosion of a high-strength reinforced concrete structural member, wherein the surface of the high-strength reinforced concrete structural member is covered with a thin steel plate. 2. A high-strength reinforced concrete structure, comprising: assembling a reinforcing steel using a discarded frame made of a thin steel plate, casting high-strength concrete, and coating the surface of the high-strength reinforced concrete structural member with the thin steel plate. Explosion prevention method. 3. A method for preventing explosion of a high-strength reinforced concrete structural member, wherein the thin steel plate according to claim 2 is reinforced with a plurality of ribs so as to withstand the driving pressure of the high-strength concrete. 4. A method for preventing explosion of a high-strength reinforced concrete structural member, wherein the thin steel plate according to claim 2 is reinforced by lattice bars and ribs so as to withstand the casting pressure of high-strength concrete.