JPH07113237B2 - Fireproof building - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fireproof structure building using a steel pipe as a main frame pillar material, and particularly to a high-rise fireproof structure building.

[Prior Art] In order to prevent thermal damage to steel structures such as columns and beams in the event of fire, steel structures are often provided with fireproof coatings necessary for columns and beams in accordance with building-related laws. Although it is obligatory to apply it, in order to increase the construction cost and reduce the space used by such a fireproof coating, a water-cooled steel pipe has recently been adopted for the steel structural material and a fireproof structure without a fireproof coating is proposed. Came to be.

For example, Japanese Utility Model Publication No. 52-16021 discloses a water-cooled refractory structure in which a water tank is placed on the top of a building and cooling water is supplied to hollow pillars. In addition to this, in high-rise buildings, it is known that a water tank is placed on the roof because of water pressure and an indoor tank is provided for each predetermined floor.

[Problems to be Solved by the Invention] As described above, providing a cooling water tank on the roof of a building raises the construction cost because the entire building must have a strong structure in terms of seismic design. In addition, the cost of installing a cooling water tank is high, and in addition to that cost, there is a problem that the effective use area of the room is narrowed, and the cooling water tank exposed on the roof of the building or the outer wall is aesthetically pleasing. There is also an unfavorable problem.

An object of the present invention is to provide a refractory structure building that can be economically constructed by using a part of a water-cooled steel pipe column as it is as a cooling water tank without requiring a separate cooling water tank as in the conventional case. Another object of the invention is to provide a fireproof structure that is structurally advantageous in terms of strength and low in construction cost.

[Means for Solving Problems] The present invention relates to a refractory structure structure in which a water-cooled steel pipe column containing water is used as a main frame column member, and the water-cooled steel pipe column is divided into unit cooling blocks at a building height. In the unit cooling block, only the upper floor portion of the water-cooled steel pipe pillar is fireproof coated to form a cooling water tank, and the cooling water tank is provided with a cooling water replenishing device and a steam discharge pipe communicating with the outdoor portion of the building. It is a characteristic fireproof structure building.

[Operation] The refractory structure of the present invention uses a water-cooled steel pipe column containing water as a main frame column member and uses a part of it as a cooling water tank, so that a separate cooling water tank becomes unnecessary, Can be economically constructed.

Since the water-cooled steel pipe column is divided into unit cooling blocks in consideration of load and water pressure conditions, economical design is possible without having to make the wall thickness and cross-sectional dimension too large. Further, since the water-cooled steel pipe column in the upper floor portion of each unit cooling block is provided with a fireproof coating to function as a cooling water tank, and no fireproof coating is provided on the other floors, it is possible to widen the useful indoor area.

In the present invention, since the structure is heavy and there is no cooling water tank to be separately installed at a high place, a structural design that is seismically advantageous can be performed, and the appearance as a building is also excellent.

Further, when the double water-cooled steel pipe column in which the cooling water descending pipe is built in the water-cooled steel pipe column is used, the circulation effect of the cooling water is enhanced, which is advantageous in heat resistance.

[Embodiment] Next, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic cross-sectional view showing an example of a fireproof structure building according to the present invention, which includes 16 floors above ground (1F to 16F) and 4 floors below ground (B1 to B).
A steel pipe structure consisting of 4), and water-cooled steel pipe columns 2a to 2d, which are the main frame columns, have 5th floors as unit cooling blocks.
~ D block.

In this example, 1st floor (1F), 6th floor (6F), 11th floor (11F), 16
The floor (16F) is the uppermost floor of the unit cooling block, and the water-cooled steel pipe columns 2a to 2d on these floors are covered with fireproof coatings 3a to 3d.

As is clear from FIG. 1, the refractory structure according to the present invention does not have a separate cooling water tank for indoors and outdoors, and the top floor of each cooling block (1F, 6F, 11F, 16F) Since only a considerable part is the cooling water tank, economical design is possible as described above.

Fig. 2 is a schematic vertical cross-sectional view of a water-cooled steel pipe column 2C in block B. The water-cooled steel pipe column 2c extends from floor 7F _{0 on the} 7th floor (7F) to beam 4 on the 12th floor (12F) in the unit cooling block area. The cooling water 5 is injected into the lumen 2C ₁ and the 11th floor (1
1F) Corresponding part, that is, the upper floor part of this example, is provided with a fireproof coating 3b and becomes a cooling water tank 2C ₂ . An upper space 6 is provided above the cooling water tank 2C ₂ , and in the upper space 6, a steam discharge pipe 7 that communicates with the outside of the building, a cooling water supply pipe 8, a water level gauge 9, and a supply control device (not shown). ) Is provided. Due to the action of this cooling water supply facility, the amount of the cooling water 5 is always kept substantially constant.

Water-cooled steel pipe pillar 2C, other floors (10F) except 11th floor (11F)
~ 7F) has no fireproof coating except for rust prevention and / or decorative coating. So, for example, the 10th floor (10F)
If there is a fire 10 in the water-cooled steel pipe column 2C on the 10th floor
Although it is directly heated by the heat input by the cooling water 10, the temperature of the steel pipe column 2C does not rise above the specified temperature, for example, 350 ° C. due to the cooling effect of the cooling water 5. As is clear from FIG. 2, the 11th floor (11F) of the water-cooled steel pipe column 2C functions exactly like a conventional cooling water tank, so there is no need to install a separate cooling water tank as in the conventional case. .

Next, the point that a part of the water-cooled steel pipe column functions as a cooling water tank will be described in more detail according to the fire resistance calculation.

The following conditions a and b are set as the premise of fire resistance calculation.

(Condition a) It is assumed that each floor has a floor as a fire protection zone, and that a fire will occur only on a specific floor.

(Condition b) There is no spread of fire from other fire-blocks on each floor, and the duration of the fire depends only on the combustion conditions (amount of combustibles, opening area, etc.) in the fire-block.

Heat conduction amount Q from the fire space to the structural members under the conditions a and b
Is obtained, the following equations (1) and (2) are obtained.

Generally, heat conduction due to radiation is sufficiently larger than that due to convection, so the amount of heat conduction per unit surface area Q (Kc
al / m ² · h) is Q = Cs × Ef × Ec × [(Tf / 100) ⁴ − (Tc / 100) ⁴ ] ……
(1) However, Cs; Blackbody radiation coefficient 4.88Kcal / m ² · h ・ ° C Ef; Overall radiation ratio of fire space 0.75 Ec; Emission ratio of structural member surface 0.85 Tf; Fire temperature ° K Tc; Structural member surface temperature ° K Therefore Q = 3.11 × [(Tf / 100) ⁴ − (Tc / 100) ⁴ ] ……
(2) Next, regarding the fire temperature ° K, the following case [1],
Set the fire temperature characteristic curve for three cases [2] and [3].

Case [1] is JIS A 1304, and Case [2] is the Swedish Steel Structural Association (Sweden i)
An equivalent fire load of 24 Mcal / m ² (per indoor surface area), a floor area of about 15 kg / m ² and an opening ratio of 0.8 (corresponding to an apartment house / school hospital) were adopted in the case [3 ] Is the equivalent fire load of 36 Mcal / m
² (per indoor surface area), about 25kg / m ² per floor area,
Use an aperture ratio of 0.8 (equivalent to an office). The total heat input to the structural member per unit surface area is Q _M (Kcal / m ² ), the column first floor is Q _T (Kcal), the water evaporation amount is V _W (liter), and the required tank capacity is V _Q (liter). ), And the depth of the cooling water tank (the tank depth of the upper floor part in the lumen of the steel pipe) is _D H (m). In addition, the water evaporation amount V _W (liter) is the latent heat of water evaporation r = 535 Kcal
Calculated as / kg.

In the water-cooled steel pipe column used in the present invention, since the area of the free water surface is small, it is possible that the rate of decrease in the amount of water due to evaporation is smaller than the rate of increase in the amount of water due to volume expansion in the early stages of a fire. Is added to the required tank volume.

Volume expansion is Q _T (Kcal) for total heat input and K for water cooling
The average temperature rise of water in the column is D _T (° K is) D, where V (m ³ ) is the volume of one floor of the water-cooled steel column, and a (° K ^-1 ) is the volumetric thermal expansion coefficient of water. _T = Q _T / (V × 10 ³ × K) Required tank capacity V _Q (liter) is V _Q = Q _T / r + V × 10 ³ × K × D _T × a = Q _T (1 / r + a) It does not depend on the number of floors K. Also, a = 21 ×
Since it is 10 ^-5, a / (1 / r) = 0.112, which is 11.2% of the water evaporation amount.
Was calculated as the volume expansion amount.

The depth of the cooling water tank is _D H (m), the height of the first floor of the water-cooled steel pipe column is H (m), the surface area of the first floor of the water-cooled steel pipe column is A ₁ (m ² ),
Assuming that the cross-sectional area of the water-cooled steel pipe column is A ₂ (m ² ), and the volume of the first floor of the water-cooled steel pipe column is V (m ³ ), Q _T ＝ Q _M × A ₁ V _W ＝ Q _T / r V _Q = 1.112 V _{W D} H = V _Q / A ₂ × 10 ^-3 . Therefore, For a circular steel pipe of diameter D (m), A ₁ = D × π × HA ₂ = (D / 2) ² × π For a square steel tube with one side D (m), A ₁ = 4 × D × HA ₂ = D ² Furthermore, for regular octagonal steel pipes with a diameter of D (m) Becomes Therefore, in the case of a circular water-cooled steel pipe column, the cooling water tank depth _D H (m) is Is required as.

A circular water-cooled steel pipe column with a diameter of 500 mm and the height of the first floor is 3.5 m
The case [1], [2],
When the specifications of [3] are obtained, the values shown in Table 1 are obtained.

Next, the tank depth _D H (m) for each diameter of the water-cooled steel pipe column is obtained by conducting heat conduction analysis for each diameter. As an example, the tank depth for each diameter D (mm) for 60 min of the case [2] above. _D H
(M) is shown in Table 2 below.

As is clear from Table 2, the floor height H is 3.
It turns out that if it is 5 m, it can function sufficiently as a water cooling tank. Also, in the most severe case [1]
In order to cope with the case of 120 min, it is necessary to cover the water-cooled steel pipe columns on the top floor and the next floor with fireproof coating to function as a water-cooled tank.

Further, the design of the inner pipe, the support plate, and the reinforcing plate at the joint between the column and the beam is determined by calculating the cooling water circulation amount, the flow velocity, etc. based on the above-mentioned fire resistance calculation.

In addition to using potassium nitrite KNO ₂ as an internal corrosion inhibitor for water-cooled steel pipe columns, potassium carbonate K ₂ CO ₃ is used as an antifreezing agent in cold regions. For example, 100 water at -30 ° C
For example, 60 parts of K ₂ CO ₃ and 1 part of KNO ₂ (weight ratio) are used.

In the graph of Fig. 3, the vertical axis represents temperature (° C) and the horizontal axis represents time (mi).
n) is taken to show the change in room temperature (° C) at the time of fire and the change in surface temperature (° C) of the water-cooled steel pipe column used in the present invention, which is obtained based on JIS A 1304. The temperature (° C) and temperature curve 12 indicate the surface temperature (° C) of the steel pipe column in the case [1].

When a fire occurs, the room temperature 11 rises rapidly, reaches 700 ° C 10 minutes later, and then rises slowly. On the other hand, the surface temperature of the water-cooled steel tube column 12 rises sharply for the first 10 minutes, then gradually rises and reaches 220 ° C 60 minutes later, but it is clear that it is below the specified value of 350 ° C.

Next, FIG. 4 is a schematic view showing a partially cut vertical cross section of the water-cooled steel pipe column 2C used in the present invention, which is mainly related to the 11th floor (11F) part and the space 13 of the floor beam 4 on the 12th floor (12F). The steam discharge pipe 7 projects toward the water-cooled steel pipe column 2C. The steam discharge pipe 7 communicates with an exhaust wall (not shown) that is appropriately provided on the outer wall surface of the building or on the rooftop (in the case of the uppermost floor). Reference numeral 8 is a cooling water supply pipe for maintaining the amount of cooling water in a normal state, and 14 is an opening / closing valve. The water level gauge 9 detects the excess or deficiency of the cooling water 5 and transmits it to a control device (not shown). In response to this, the on-off valve 14 is operated to replenish the cooling water.

With the above-described configuration, the steam generated in the water-cooled steel pipe column 2C at the time of a fire is safely discharged to the outside through the steam discharge pipe 7, so there is no risk of a secondary disaster due to the steam. The volume of the upper space 6 of the cooling water tank 2C ₂ is determined in consideration of the thermal expansion amount of the cooling water and the steam discharge by the steam discharge pipe 7.

As described in FIG. 2, when a fire occurs in the B cooling block, the cooling water circulates as shown by arrows 15a to 15c, and the temperature of the water-cooled steel pipe column 2C is further increased by absorbing the latent heat by the evaporation of the cooling water. It is possible to keep it below the specified value.
Reference numerals 16a and 16b denote, for example, fireproof concrete floors having a function as a fireproof section.

The B cooling block has been explained above, but fires A, C, D
Even if it occurs in any of the cooling blocks, the water-cooled steel pipe columns are sufficiently cooled by the cooling water circulation.

The fire-resistant coating 3b in the present invention is sufficient in the specifications according to the building-related regulations, and is constructed in accordance with the standard by using a fire-resistant material such as sprayed asbestos, lath mortar or concrete.

Next, in the present invention, the point of dividing the water-cooled steel pipe column into unit cooling blocks in the building height direction will be described.

When the water-cooled steel pipe column is a steel material specified in SM50, the long-term allowable stress is 2,200 Kg / cm ² , the short-term allowable stress is 3,300 Kg / cm ^2, so the allowable stress is added to the existing stress by hydraulic pressure. Design to be within degrees. When a circular steel pipe or square steel pipe with an inner diameter Dcm and a plate thickness tcm is selected as the water-cooled steel pipe column, the height of the unit cooling block is set to Hm, and K ₂ CO ₃ , K
If the specific gravity γ of the cooling water containing NO ₂ is 1.36 t / m ³ , the water pressure P
Is as in the following formula (3).

P = γ ・ H = 0.136 HKg / cm ² (3) Stresses σ ₁ and σ ₂ of the water-cooled steel pipe column due to water pressure are circular water-cooled steel pipe column σ ₁ = 0.068 × H × K Kg / cm ² Square water-cooled steel pipe Column σ ₂ = 0.068 × H × K (1 + K) Kg / cm ² (corner) Therefore, in the case of steel tube with H of 40 m, inner diameter D of 46.2 cm, and plate thickness t of 1.9 cm, stress of circular water-cooled steel tube σ ₁ = 66.1Kg / cm ² Stress of rectangular water-cooled steel tube σ ₂ = 1,674.3Kg / cm ² Therefore, when it is desired to make the unit cooling block large, it is preferable to adopt a circular water-cooled steel pipe column.

The unit cooling block is usually divided into 5th to 30th floors, and it is often economical to design the unit cooling block into 10th to 20th floors.

In the present invention, the upper floor portion means, as is clear from the above description, the case where the cooling function is satisfied by the portion equivalent to the first floor,
In some cases, water-cooled steel pipe columns equivalent to or more than the third floor may be continuously fireproof coated and used as a cooling water tank, and all of them are determined in consideration of the satisfaction of the cooling function by the fireproof calculation.

When it is necessary to further enhance the cooling function, as shown in FIG. 5, support fittings 17a, 17 fixed to the inside of the water-cooled steel pipe column 2C
When the cooling water descending inner pipe 18 is supported via b to form a double water-cooled steel pipe column, the cooling efficiency can be improved by 10 to 15%.

[Effects of the Invention] The refractory structure of the present invention uses a water-cooled steel pipe column having a cooling water tank by itself as a main frame pillar material and does not require a separate cooling water tank. It has excellent properties. In addition, the construction cost is low because economical design is possible for the construction.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a refractory structure according to the present invention, FIG. 2 is a schematic partial longitudinal cross-sectional view of a water-cooled steel pipe column, and FIG. 3 is a room temperature (° C.) at the time of fire and the surface of the water-cooled steel pipe column. FIG. 4 is a partially cutaway vertical sectional view of a water-cooled steel pipe column, and FIG. 5 is a partial vertical sectional schematic view of a double water-cooled steel pipe column. DESCRIPTION OF SYMBOLS 1 ... Fireproof structure building, 2a-2d ... Water-cooled steel pipe column, 2c ₁ ... Lumen, 2c ₂ ... Cooling water tank, 3a-3d ... Fireproof coating, 4 ... Beam,
5 ... Cooling water, 6 ... Upper space, 7 ... Steam discharge pipe, 8 ... Cooling water supply pipe, 9 ... Water level gauge, 10 ... Fire, 11, 12 ... Temperature curve, 13 ... Space, 14 ... Open / close valve, 15a ... 15c ... Arrows, 16a, 16b
… Fire-resistant concrete floor, 17a, 17b… Support metal fittings, 18… Cooling water descending inner pipe.

Claims (2)

[Claims] 1. A refractory structure building in which a water-cooled steel pipe column containing water is used as a main frame column material, the water-cooled steel pipe column is divided into unit cooling blocks in a building height direction, and the unit cooling block is located on an upper floor. A refractory structure building characterized in that only a portion of the water-cooled steel pipe pillar is fireproof coated to form a cooling water tank, and the cooling water tank is provided with a cooling water supply device and a steam discharge pipe communicating with the outdoor portion of the building. 2. The refractory structure building according to claim 1, wherein a double water-cooled steel pipe column having a cooling water descending inner pipe built therein is used as the water-cooled steel pipe column.