JPH07113238B2 - Fireproof building - Google Patents

Description

TECHNICAL FIELD The present invention relates to a steel structure building having a hollow steel pipe as a main skeleton, and more particularly to a high-rise fireproof structure building.

[Prior Art] With respect to steel structures, it is obliged by the building-related laws and regulations to apply a fireproof coating so that the steel material as the main frame does not lose its loading capacity due to thermal damage during a fire. . In order to increase the construction cost and reduce the use space of this fireproof coating, a water-cooled steel pipe has recently been adopted as a steel material, and a fireproof structural building without a fireproof coating has been proposed.

For example, Japanese Utility Model Publication No. 52-16021 discloses a refractory structure in which a water tank is placed on the upper part of a building and a cooling water circulation structure for supplying cooling water to a hollow steel pipe is provided without a fireproof coating. In addition, other publications on similar buildings have been published. As shown in Fig. 8, this fire-resistant building is constructed by connecting the lower ends of the steel pipe columns 1a, 1b of the main frame with cooling water communication pipes 2, and connecting the cooling water tank 3 on the roof and the upper ends of the steel pipe columns 1a, 1b. The cooling water is circulated by connecting the water pipes 4a and 4b. Furthermore, as shown in FIG. 9, it has been proposed to incorporate cooling water descending inner pipes 5a, 5b in the inner cavities of the steel pipe columns 1a, 1b to improve the circulation efficiency of the cooling water.

[Problems to be Solved by the Invention] As described above, providing a cooling water tank on the roof of a building requires that the entire building has a structure with high strength in terms of seismic design, which increases the construction cost. In addition to the above points, the cost of installing a cooling water tank is high, and in the case of installing a cooling water tank indoors, there is the problem of reducing the effective use area in the room. The exposed cooling water tank has an aesthetically unfavorable problem.

INDUSTRIAL APPLICABILITY The present invention does not require a separate cooling water tank as in the prior art by using the steel pipe columns and steel pipe beams, which are main frames, and / or steel pipe braces as they are as cooling water tanks.
Another object of the present invention is to provide a refractory structure that can be economically constructed, and yet another purpose is to provide a refractory structure that is advantageous in terms of strength from the viewpoint of earthquake-resistant structure and has a low construction cost. Another object is to provide high-rise and super high-rise refractory buildings.

[Means for Solving the Problems] In order to achieve the above-mentioned object and solve the problems, the present invention joins steel pipe columns and steel pipe beams and / or steel pipe braces so that respective lumens communicate with each other, In a refractory structure building having a main frame that allows free circulation of cooling water, the main frame is divided into unit cooling blocks in the building height direction, and only the upper floor part of each unit cooling block is fireproof coated to form a cooling water tank. The refractory structure is characterized in that the cooling water tank is provided with a cooling water replenishing device and a steam pipe communicating with the outdoor portion of the building.

[Operation] Since the refractory structure of the present invention uses the steel pipe columns and the steel pipe beams, which are the main frames, and / or the steel pipe braces as cooling water tanks, a separate cooling water tank is not required, which makes the building economical. Can be constructed. Also, because the main frame is divided into unit cooling blocks in the building height direction in consideration of load and water pressure conditions, there is no need to increase the wall thickness and cross-sectional dimensions of the main frame so economical design is possible. is there. In addition, the present invention is heavy, and since there is no cooling water tank to be separately installed at a high place, it is possible to design a structurally advantageous structure in terms of earthquake resistance.
As a building, you can build one with a beautiful appearance. Further, when the cooling water descending inner pipe is incorporated in the main frame, the cooling water circulation effect can be enhanced, which is more advantageous in terms of heat resistance.

In the present invention, since only the frame of the upper floor of each cooling block is provided with the fireproof coating and the other floors are not provided with the fireproof coating, it is possible to significantly reduce the cost of the refractory material, and fires occur on any floor. However, since the cooling water circulation function is not lost, there is no risk of heat damage to the main frame, and the safety of the building is extremely high.

[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 refractory structure building according to the present invention, which is a steel pipe structure consisting of 16 floors above ground (1F to 6F) and 4F below ground (B1 to B4), and the main frame is a steel pipe column. 7a to 7b, a steel pipe beam 8, and a steel pipe brace 9 (the steel pipe beam 8 and the steel pipe brace 9 are represented by only one part as a representative). Only one of the steel pipe beam 8 and the steel pipe brace 9 may be adopted.

As shown in Fig. 1, considering the various conditions such as load and water pressure on the main frame, each 5th floor is divided into unit cooling blocks (A to D), and the 1st floor (1F), 6th floor (6F), The 11th floor (11F) and 16th floor (16F) are used as the upper floors and fireproof coatings (10a-10d) are applied.

Since the main skeleton is joined so as to communicate the lumens in each unit cooling block, the circulation of the injected cooling water is performed in each unit block.

Next, since the upper floor is fire-resistant coated, even if a fire occurs in the upper floor, the main frame will not be abnormal, and when a fire occurs in another floor, Since the main frame functions like a conventional cooling water tank, the main frame of the floor is efficiently cooled and there is no risk of thermal damage. Since fire resistant coatings are not applied to the main frames on the floors other than the upper floor, the fire resistant material cost and construction cost are significantly reduced.
The floor space used is large and the cooling water tank is not installed separately, so the construction cost is low and the utilization efficiency is extremely high.

Next, FIG. 2 is a schematic explanatory view showing a situation in which a fire 11 has occurred in the refractory structure 6, and the main frame is composed of steel pipe columns and steel pipe beams, and is an embodiment having no steel pipe bracing.

The steel pipe column 7C and the steel pipe beam 8a generate convection as shown by the arrow, and the heat removal effect does not cause the temperature of the steel pipe column 7C to exceed 350 ° C, for example. Also, due to the heat insulation effect of the floor 12 of the 12th floor (12F) where the fire 11 occurred, there is almost no effect on the 11th floor (11F) of the lower floor, and even if there is heat transferred through the floor 12, the steel pipe beam
Since it is diffused by the cooling water in 8b, there is no problem in the main frame.

FIG. 3 is an example in which the cooling water descending inner pipe 13a is incorporated in the A block and the cooling water descending inner pipe 13b is incorporated in the B block for the steel pipe column 7C, and the cooling efficiency is improved by 5 to 10%.

FIG. 4 is a schematic cross-sectional view showing a portion where a steel pipe column, a steel pipe beam, and a steel pipe brace are joined as a main frame. The steel pipe column 7C has a built-in cooling water descending inner pipe 13b, and further steel pipe beams 8b, 8c, 8h and steel pipe braces 9a-9d are joined so that cooling water can communicate freely.

Further, although an auxiliary metal fitting for connection is often used for connecting the steel pipe braces 9a to 9d to the steel pipe column 7C, it is omitted for convenience of explanation.

FIG. 5 is a schematic explanatory view of a water supply device and a steam discharge pipe for constantly replenishing cooling water mounted on a part of the steel pipe beam 8b,
14 is a water level gauge, 15 is a water supply pipe, the detection signal of the water level gauge 14 is transmitted to a control device (not shown), and the on-off valve 16 provided in the water supply pipe 15 is controlled to maintain a preset water level. To be done. Furthermore, 17 opens in the upper space 18 of the steel pipe beam 8b,
The other end is a steam discharge pipe opened to the outside of the building through a safety valve (not shown), and steam generated from the cooling water at the time of fire is discharged from the steam discharge pipe 17.

FIG. 6 is a schematic perspective view showing a part of the main skeleton of the unit cooling block for the refractory structure of the embodiment according to the present invention. The steel pipe columns 19a and 19b, the steel pipe beams 20a to 20h, and the steel pipe braces 21a to
Reference numeral 21d is connected so that the cooling water can freely circulate, and each has a cooling water descending inner pipe (represented by 22a, 22b, and 22c) built therein. This example is adopted especially when it is desired to enhance the cooling efficiency.

Next, a description will be made in detail according to the fire resistance calculation regarding the fact that the steel pipe columns and the steel pipe beams and / or the steel pipe braces are provided with a fire resistant coating only on the upper floor portion of each unit cooling block to function as a cooling water tank.

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 fire spread from other fire-prevention compartments on each floor, and the duration of the fire depends only on the combustion conditions (amount of combustibles, opening area, etc.) of the fire-prevention compartment.

When the heat conduction Q from the fire space to the main frame, that is, the structural member is obtained under the conditions a and b, 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) where Cs; radiation coefficient of black body 4.88Kcal / m ² · h · ℃ Ef; radiation ratio of the structural member surface 0.85 Tf;; flame temperature ° K Tc; overall radiation ratio 0.75 Ec fire spatial structure member surface temperature ° K thus Q = 3.11 × [(Tf / 100) 4 - ( Tc / 100) ⁴ ] …… (2) Next, regarding temperature ° K, the following cases [1], [2],
Set fire temperature characteristic curves for the three cases of [3].

Case [1] is JIS A 1304, and Case [2] is the Swedish Steel Structural Association (Sweden I) considering the fire cooling area.
NSTITUTE of Steel Construction) Equivalent fire load 24Mcal / m ² according to the proposal (per room area), a per floor area taken about 15 Kg / m ^2, the aperture ratio 0.8 (corresponds to apartment houses and schools hospitals) 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 structural member is divided into a structural material 1 (for example, a steel pipe column), a structural material 2 (for example, a steel pipe bracing), and a structural material 3 (for example, a steel pipe beam), and the specifications for the first floor of the building are determined as follows.

Surface area A ₁ , A ₂ , A ₃ (m ² ) Volume V ₁ , V ₂ , V ₃ (liter) Cross-sectional area S ₁ , S ₂ , S ₃ (m ² ) Length L ₁ , L ₂ , L ₃ ( m) Total surface area _AT (m ² ) Total volume V _T (liter) Also, the total heat input Q _M (Kcal / m ² ) to the structural members per unit surface area Total heat input Q _T ( Kcal) Water evaporation V _W (liter) Required tank capacity V _Q (liter) The water evaporation amount V _W (liter) was calculated as the latent heat of water evaporation r = 535 Kcal / kg.

In the structural member used in the present invention, since the area of the free water surface is small, there is a possibility 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. Add to the tank volume.

If the volume expansion is the number of floors shared by water cooling and the volume temperature expansion coefficient of water K is a (° K ^-1 ), the average temperature rise DT (° K) of water in the structural member is D _T = Q _T / (V × 10 ³ × K) The required tank capacity V _Q (liter) is V _Q = Q _T / r + V × 10 ³ × K × D _T × a = Q _T (1 / r + a), and does not depend on the water cooling share floor 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.

When the above specifications are calculated, Q _T = Q _M × A _T = Q _M × (A ₁ + A ₂ + A ₃ ) V _W = Q _T / r V _Q = 1.112V _W V _T = V ₁ + V ₂ + V ₃ = It becomes S ₁ × L ₁ + S ₂ × L ₂ + S ₃ × L ₃ . Therefore Generally, the structural materials 1 and 2 are circular steel pipes or square steel pipes. In this case, the specifications of the structural member for the first floor of the building are the surface area A (m ² ), the cross-sectional area S (m ² ), and the length L (m). Then, A / (S × L) = 4 / D for a circular steel pipe with a diameter D (m) and A / (S × L) = 4 / D for a square steel pipe with one side S (m). When a closed cross-section material is used for 3, it is an unequal square steel pipe, the long side is D ₁ (m), the short side is D ₂ (m), and considering that heat is not input from the short side in contact with the floor directly above, A / (S × L) = (2 × D ₁ + D ₂ ) / (D ₁ × D ₂ ) Here, since generally D ₂ = 0.4 × D _1, A / (S × L) = 6 / D ₁ Becomes The ratio of structural materials 1 to 3 varies depending on the building,
Approximately if A / (S × L) = 5 / D on average For example, V _Q / V _T = 1.0, that is, the total heat input per unit surface area to the structural member that can cover the capacity of the cooling water tank with the structural member of the first floor is D _M = 500 mm Q _M = 48,112 Kcal / m ² Becomes

For the cases [1], [2], and [3], the total heat input Q _M to each structural member per unit surface area and the depth _D H (m) of the structural member corresponding to the cooling water tank capacity are obtained. And the values in Table 1 are obtained. Here, the height of the first floor of the building is 3.5m.

Next, the depth _D H (m) of the structural member corresponding to the capacity of the cooling water tank for each diameter of the structural member is obtained by conducting heat conduction analysis for each diameter. As an example, the diameter D for 60 min of case [2] above
(M) Another structural part _D H (m) is shown in Table 2.

As is clear from Table 2, in each case, if the height of the first floor of the building is 3.5 m, it can be fully functioned as a water cooling tank.

Also, 120m in the most severe case [1]
In order to deal with the case of in, it is necessary to cover the structural members on the uppermost floor and the next floor with fireproofing to function as a cooling tank.

The fire-resistant coating in the present invention is sufficient to have specifications according to the building-related regulations. For example, a fire-resistant material such as sprayed asbestos, lath mortar, concrete, etc. is used as standard. Further, the design of the inner pipe, the support plate, and the reinforcing plate in the connection between the column and the beam is determined by calculating the circulating amount of cooling water, 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 steel pipe structural materials, 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.

FIG. 7 shows temperature (° C.) on the vertical axis and time (min) on the horizontal axis, and changes in room temperature (° C.) in a fire experiment determined based on JIS A 1304 and the surface of the structural member used in the present invention. The change in temperature (° C.) is displayed, the temperature curve 23 shows room temperature (° C.), and the temperature curve 24 shows the structural member surface temperature (° C.) in the case [1].

Next, the point of dividing the structural member into unit cooling blocks in the building height direction in the present invention will be described.

If the structural member is a steel specified by SM50, the long-term allowable stress is 2,200 Kg / cm ² , and the short-term allowable stress is 3,300 Kg / cm ^2, so the existing stress should be within the allowable stress by adding the hydraulic stress. Design to be. Inner diameter as structural member Dc
When selecting circular steel pipe and square steel pipe with m and plate thickness tcm,
When the height of the unit cooling block is Hm and the specific gravity γ of the cooling water containing K ₂ CO ₃ and KNO ₂ is 1.36 t / m ³ , the water pressure P is as shown in (3) below.

P = γ ・ H = 0.136 HKg / cm ² (3) Stresses of structural members due to water pressure are σ ₁ and σ ₂ are circular steel pipe structural members σ ₁ = 0.068 × H × K Kg / cm ² Square steel pipe structure Material σ ₂ = 0.068 × H × K (1 + K) Kg / cm
² (corner) Therefore, in the case of steel pipe structural member with H of 40 m, inner diameter D of 46.2 cm, and plate thickness t of 1.9 cm, stress of circular steel pipe structural member σ ₁ = 66.1 Kg / cm ² Stress of square steel pipe structural member σ ₂ = 1,674.3 It becomes Kg / cm ² . Therefore, when it is desired to make the unit block large, it is preferable to employ a circular steel pipe structural member.

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, steel pipe structural members equivalent to or above the third floor are continuously fireproof coated and used as cooling water tanks, and they are all determined in consideration of the satisfaction of the cooling function by fireproof calculation.

[Effects of the Invention] In the fireproof structure building of the present invention, the main frame of the building itself is divided into unit cooling blocks in the building height direction, and only the upper floor portion is used as a cooling water tank, which is installed separately. Since it does not require a cooling water tank, it has a large space for use and is highly earthquake-resistant and highly safe. In addition, the construction cost is low because economical design is possible for the construction.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of a refractory structure according to the present invention, FIG. 2 is a schematic explanatory view showing a fire occurrence and a cooling condition of a main frame, and FIG. 3 is a facility for a cooling water descending inner pipe. Fig. 4 is a schematic partial cross-sectional view of the frame showing the situation, Fig. 4 is a schematic cross-sectional view of the joints of steel pipe columns, beams, and braces, Fig. 5 is an explanatory view of the equipment status of the water supply device and steam discharge pipe, and Fig. 6 is cooling water. FIG. 7 is a partial schematic perspective view of a main frame having a descending inner pipe built-in, FIG. 7 is a diagram showing the relationship between the surface temperature of a steel pipe structural member and room temperature, and FIG. 8 is a conventional water-cooled refractory structure building. It is a partial perspective view of FIG. 1a, 1b ... Steel pipe columns, 2 ... Cooling water communication pipes, 3 ... Cooling water tanks, 4a, 4b ... Water pipes, 5a, 5b ... Cooling water descending inner pipes, 6 ... Fire-resistant structure buildings, 7a-7d ... Steel pipe columns , 8,8a ~ 8c, 8h ... Steel pipe beam,
9,9a-9d ... Steel pipe braces, 10a-10d ... Fireproof coating, 11 ... Fire,
12 ... Floor, 13a, 13b ... Cooling water descending inner pipe, 14 ... Water level gauge, 15 ...
Water supply pipe, 16 ... open / close valve, 17 ... steam discharge pipe, 18 ... upper space,
19a, 19b ... Steel tube column, 20a-20h ... Steel tube beam, 21a-21d ... Steel tube brace, 22a-22c ... Cooling water descending inner tube, 23,24 ... Temperature curve

Claims (2)

[Claims] 1. A fireproof structural building having a main frame in which a steel pipe column, a steel pipe beam and / or a steel pipe brace are connected so that their inner cavities communicate with each other, and cooling water can be freely circulated. Divided into unit cooling blocks in the vertical direction,
A refractory structure characterized in that only the upper floor portion of each unit cooling block 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 pipe communicating with the outdoor portion of the building. object. 2. The refractory structure building according to claim 1, wherein a double water-cooled steel pipe having a built-in cooling water descending inner pipe is used for at least one of steel pipe columns, steel pipe beams, and steel pipe braces.