JP5565866B2 - Fire damage reduction structure - Google Patents

Description

  The present invention relates to a fire damage reducing structure.

  Conventionally, when a reinforced concrete building is damaged by a fire, in order to reuse this building, the part which has received the fire is repaired. Specifically, a portion of the building beam or column that has received heat of 300 ° C. or more is suspended, and then concrete is placed in the suspended portion.

  By the way, even if an attempt is made to suspend a part of the column, since a large axial force is acting on the column, it is necessary to first install a temporary member that temporarily receives the axial force acting on the column. Therefore, there was a problem that it took considerable time to repair the pillar.

In order to solve this problem, the following two methods have been proposed.
First, a method of covering the surface of a reinforced concrete column member with a thin steel plate has been proposed (see Patent Document 1). This thin steel plate is in contact with the concrete surface.
According to this proposal, since the heat of the fire is transmitted to the thin steel plate, it is possible to prevent the temperature of the concrete surface of the column member from abruptly rising, thereby preventing concrete explosion.

Secondly, it has been proposed to provide a calcium silicate plate on the surface of a reinforced concrete member (see Patent Document 2). An air layer is provided between the calcium silicate plate and the concrete surface.
According to this proposal, since an air layer is provided between the calcium silicate plate and the concrete surface, this air layer becomes a heat insulating layer, so that the surface of the concrete is compared with the case where the calcium silicate plate is provided directly on the concrete surface. The rise in the temperature can be suppressed, and concrete explosion can be prevented.

Japanese Patent Laid-Open No. 11-93295 JP 2004-360193 A

However, in the first method, since the thin steel plate is in contact with the concrete, the heat of the fire is transmitted to the concrete and the concrete explosion cannot be effectively suppressed.
Further, in the second method, since the air layer becomes a heat insulating layer, the rise in the temperature of the concrete surface is mitigated, but the thickness of the calcium silicate plate needs to be increased, and the size of the column is increased.

  An object of the present invention is to provide a fire damage reduction structure capable of effectively suppressing concrete explosion while suppressing an increase in size of a member.

The fire damage reducing structure according to claim 1 includes a reinforced concrete frame and a steel cover provided with an air layer on the surface of the frame, and the frame is a column having a rectangular cross section. The cover part is provided with four substantially L-shaped steel plates, each of the steel plates is arranged so as to straddle the four corners of the columnar column of the housing, and the ends of the steel plates It is characterized by surrounding the periphery of the housing by overlapping .

According to this invention, since an air layer becomes a heat insulation layer and the raise of a housing temperature is relieve | moderated, it can suppress effectively that the concrete of a housing explodes.
Moreover, since the cover part is made of steel, the thickness of the cover part can be reduced, so that the increase in the size of the member can be suppressed.

  In addition, once explosion occurs, the concrete in the exploded part is newly exposed, and this exposed concrete is heated by an open flame and further explodes. By repeating the explosion in this way, the fire damage may reach deep inside the housing. However, according to the present invention, even if the concrete in the casing explodes, the cover part holds down the exploded concrete pieces, so that it is possible to prevent the explosion from occurring continuously, and to reduce fire damage.

In the fire damage reducing structure of the present invention, it is preferable that a fireproof paint is applied to the surface of the cover portion .

Even if the fireproof paint is applied directly to the surface of the concrete frame, the fireproof paint film is not uniformly heated on the concrete base, so a uniform heat insulation layer cannot be formed, and the concrete frame cannot be sufficiently protected. There was a problem.
However, according to the present invention, since the fire-resistant paint is applied to the surface of the steel cover portion, the fire-resistant paint film is uniformly heated by the steel base to form a uniform heat-insulating layer. Can protect the concrete frame.

In the fire damage reducing structure of the present invention, the thickness of the air layer is preferably about 5 mm .

  According to this invention, since the thickness of the air layer is approximately 5 mm, it is possible to reliably form the heat insulating layer while minimizing the thickness of the air layer and suppressing the size of the member from increasing.

In addition, according to the first aspect of the present invention, since the cover portion is configured by combining four substantially L-shaped steel plates, even if there is some construction error in the cross-sectional size of the column, the column 4 One side can be covered reliably.

  According to this invention, since an air layer becomes a heat insulation layer and the raise of a housing temperature is relieve | moderated, it can suppress effectively that the concrete of a housing explodes. Moreover, since the cover part is made of steel, the thickness of the cover part can be reduced, so that the increase in the size of the member can be suppressed. In addition, even if the concrete in the casing explodes, the cover portion holds down the exploded concrete pieces, so that the occurrence of continuous explosions can be suppressed, and fire damage can be reduced.

It is the cross-sectional view and side view of the pillar of the building to which the fire damage reduction structure which concerns on embodiment of this invention was applied. It is the cross-sectional view and longitudinal cross-sectional view of the corner | angular part of the column which concern on the said embodiment. It is a figure which shows the temperature distribution at the time of heating the concrete frame which concerns on the comparative example and Example of this invention for 1 hour. It is a figure which shows the temperature distribution at the time of heating the concrete frame which concerns on the comparative example and Example of this invention for 2 hours. It is a figure which shows the temperature distribution at the time of heating the concrete frame which concerns on the comparative example and Example of this invention for 3 hours. It is a figure which shows the temperature change of the concrete which concerns on the comparative example and Example of this invention.

FIG. 1 is a cross-sectional view and a side view of a pillar 10 of a building to which a fire damage reducing structure according to an embodiment of the present invention is applied. FIG. 2 is a transverse sectional view and a longitudinal sectional view of a corner portion of the column 10.
The column 10 includes a column housing 20 having a rectangular cross section made of reinforced concrete, and a steel cover portion 40 provided on the surface of the column housing 20 with an air layer 30 interposed therebetween.
The thickness of the air layer 30 is approximately 5 mm.

A fireproof paint is applied to the outer surface of the cover portion 40 to form a coating film 50. A white paint is applied to the inner surface of the cover 40 and the concrete surface of the columnar frame 20.
The cover portion 40 is composed of four substantially L-shaped steel plates 41. Specifically, each steel plate 41 includes a flat plate portion 411, a bent portion 412 where one end side of the flat plate portion 411 is bent, and a flat plate-like spacer 413 attached to the inner surface of the flat plate portion 411.

The cover part 40 is assembled in the following procedures.
First, the steel plate 41 is arrange | positioned so that the specific corner | angular part of the column housing 20 may be straddled. That is, the spacer 413 of the steel plate 41 is brought into contact with another side surface adjacent to this corner portion while the bent portion 412 of the steel plate 41 is hooked to one side surface adjacent to the specific corner portion. As a result, the flat plate portion 411 of the steel plate 41 covers another side surface of the column housing 20 at a predetermined interval.

By repeating the above procedure, each steel plate 41 is disposed so as to straddle the four corners of the columnar frame 20. At this time, as shown in FIG.1 (b), each steel plate 41 is arrange | positioned up and down zigzag.
Then, the edge part of the flat plate part 411 of each steel plate 41 contact | abuts and overlaps on the bending part 412 of the adjacent steel plate 41, and surrounds the four side surfaces of the column housing 20. FIG.
In this state, the backing plate 42 is provided and fillet welded at predetermined intervals to integrate the steel plates 41 with each other.

Here, the reason why the white paint is applied to the inner surface of the cover 40 and the concrete surface of the columnar frame 20 is as follows.
The heat flow rate q flowing into the concrete from the steel plate is represented by the following formula (1). In Equation (1), the steel sheet temperature T _S , the concrete temperature T _C , the steel sheet emissivity ε _S , and the concrete emissivity ε _C are used.

  From the above formula (1), it can be seen that the heat inflow from the steel sheet to the concrete can be reduced by lowering the emissivity. Therefore, the emissivity is lowered by applying a white paint to the inner surface of the steel plate and the concrete surface.

[Examples and Comparative Examples]
Assuming a 600 mm × 600 mm concrete case, heat conduction analysis was performed on the concrete case.
In Comparative Example 1, a concrete frame was directly heated without providing a steel plate.
In Comparative Example 2, a steel plate was directly attached to the surface of the concrete frame and heated from the outside of the steel plate.
In the example, a steel plate was provided on a concrete frame with an air layer in between, and heated from the outside of the steel plate.

3-5 is a figure which shows the temperature distribution at the time of heating the concrete frame which concerns on a comparative example and an Example, respectively for 1 hour, 2 hours, 3 hours.
3 to 5, (a) is Comparative Example 1, (b) is Comparative Example 2, and (c) is an Example.

  3 to 5, the part from 0 ° C to 100 ° C is A, the part from 100 ° C to 200 ° C is B, the part from 200 ° C to 300 ° C is C, and the part from 300 ° C to 400 ° C D, 400 ° C to 500 ° C portion E, 500 ° C to 600 ° C portion F, 600 ° C to 700 ° C portion G, 700 ° C to 800 ° C portion H, 800 ° C The portion from 900 ° C. is I, the portion from 900 ° C. to 1000 ° C. is J, the portion from 1000 ° C. to 1100 ° C. is K, and the portion from 1100 ° C. to 1200 ° C. is L.

  As shown in FIGS. 3 to 5, by providing a steel plate with an air layer in between, the temperature rise of the concrete frame is suppressed regardless of the heating time, compared to the case where the steel plate is directly attached or the case where no steel plate is provided. It can be seen that Moreover, it turns out that the suppression effect of a temperature rise becomes high as heating time becomes long.

Next, a heating experiment was performed on the concrete.
In Comparative Example 1, the steel plate was directly heated without providing the steel plate.
In Comparative Example 2, a steel plate was provided in contact with concrete and heated from the outside of the steel plate. No fireproof paint was applied to the steel sheet.
In the example, a steel plate was provided with an air layer sandwiched between concrete, a fireproof paint was applied on the steel plate, and the steel plate was heated from the outside.

  About the above Example and the comparative example, it heated along the standard fire heating temperature curve, and measured the steel plate surface temperature and the concrete surface temperature.

FIG. 6 is a diagram illustrating a temperature change of the concrete according to the comparative example and the example. In FIG. 6, (a) is Comparative Example 1, (b) is Comparative Example 2, and (c) is an Example.
It can be seen from FIG. 6 that when an air layer is provided between the concrete and the steel plate and a fireproof paint is applied on the steel plate, the increase in the concrete surface temperature can be greatly suppressed.

Moreover, it turns out that when the fire-resistant paint is applied to the steel sheet, the increase in the concrete surface temperature can be suppressed as compared with the case where the fire-resistant paint is applied to the concrete surface.
The reason for this is as follows. That is, the refractory paint is heated and foamed to form a heat insulating layer, and the thickness of the foamed layer depends on the film thickness of the paint and the temperature of the coating base surface. Specifically, the thicker the film thickness and the higher the temperature of the base surface, the thicker the foam layer and the better the heat insulation performance. This is because the steel plate has a smaller heat capacity than the concrete, so that the surface of the steel plate becomes high temperature, the thickness of the foamed layer is increased, and the heat insulation performance is increased.

According to this embodiment, there are the following effects.
(1) Since the air layer 30 becomes a heat insulation layer and the temperature rise of the columnar body 20 is mitigated, it is possible to effectively suppress the concrete of the columnar body 20 from exploding.
Moreover, since the cover part 40 is made of steel, the thickness of the cover part 40 can be reduced, so that the increase in size of the member can be suppressed.

  Moreover, even if the concrete of the pillar frame 20 explodes, the cover portion 40 holds down the exploded concrete pieces, so that it is possible to prevent the explosions from occurring continuously and to reduce fire damage.

  (2) Since the fire-resistant paint film 50 is formed on the surface of the steel cover 40, the fire-resistant paint film 50 is uniformly heated by the steel base, and the paint film 50 forms a uniform heat insulating layer. Since it forms, the pillar frame 20 can be protected.

  (3) Since the thickness of the air layer 30 is approximately 5 mm, the heat insulating layer can be reliably formed while suppressing the increase in the size of the member by minimizing the thickness of the air layer.

  (4) Since the cover portion 40 is configured by combining four substantially L-shaped steel plates 41, the four side surfaces of the column housing 20 can be reliably secured even if there is some construction error in the cross-sectional size of the column housing 20. Can be covered.

  It should be noted that the present invention is not limited to the above-described embodiment, and modifications, improvements, etc. within a scope that can achieve the object of the present invention are included in the present invention.

DESCRIPTION OF SYMBOLS 10 ... Pillar 20 ... Column housing 30 ... Air layer 40 ... Cover part 41 ... Steel plate 42 ... Backing plate 50 ... Coating film 411 ... Flat plate part 412 ... Bending part 413 ... Spacer

Claims (1)

A reinforced concrete structure, and a steel cover provided with an air layer on the surface of the structure,
The housing is a columnar housing having a rectangular cross section,
The cover part prepares four substantially L-shaped steel plates, arranges each of the steel plates so as to straddle the four corners of the pillar column of the frame, and overlaps the ends of the steel plates. The fire damage reducing structure characterized by surrounding the surrounding of the housing.

Images