JPH111973A - Control method for explosion of concrete structure - Google Patents

Abstract

(57) [Problem] To improve reliability of fire safety of a concrete structure by accurately controlling the degree of explosion occurring at the time of fire in each member of the concrete structure. SOLUTION: The service performance required for a concrete structure at the time of a fire and after a fire is set in advance, and based on the service performance, the amount of cross-sectional loss allowed for each member constituting the concrete structure is determined. Based on this calculation, the depth of the delamination depth due to the explosion of the concrete, which is assumed to occur in each member, is adjusted based on the cross-sectional loss. In making this adjustment, one or both of the water-cement ratio of the concrete constituting each member and the amount of the material for preventing explosion mixed into the concrete are adjusted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the explosion of a concrete structure for controlling the occurrence of a phenomenon (explosion) of the concrete when the concrete structure is fired.

[0002]

2. Description of the Related Art In recent years, concrete materials called high-strength concrete, which has a higher compressive strength than ordinary ordinary concrete, have been actively used. Although such high-strength concrete is expected to be used for various structures due to its design standard strength, in the event of a fire, the expansion pressure of water vapor contained inside increases, and It is said that when a steady thermal stress is generated, a phenomenon (explosion) of peeling from the surface in a scale-like manner tends to occur.

Therefore, in a structure using high-strength concrete, each member explodes in a fire,
There is a concern that the progress of this will cause safety issues in the structure, and therefore, high-strength concrete used when constructing the structure, as a measure to prevent explosion,
Incorporation of synthetic fibers such as polypropylene has been studied.

[0004]

However, up to now, when mixing such a synthetic fiber into concrete, no consideration has been given to the difference in the strength of the concrete. There is a problem that the effect of suppressing the above cannot be obtained.
Therefore, there has been a demand for a technique capable of more reliably obtaining the effect of suppressing explosion by considering conditions such as the strength of concrete.

[0005] When high-strength concrete mixed with synthetic fibers is actually used for construction work,
A large amount of synthetic fiber is required and its cost increases, it is not always easy to knead the synthetic fiber evenly in the concrete, and concrete mixed with synthetic fiber has a higher fluidity than that without fiber. Therefore, there is a problem that it is difficult to reach every corner inside the formwork at the time of casting on site. For this reason, while ensuring the reliability and soundness of structures during and after a fire, the use of synthetic fibers mixed into concrete is reduced as much as possible, thereby reducing construction costs and There has been a demand for a technology that facilitates construction of a structure.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to precisely control the degree of explosion occurring at the time of a fire in each member of a structure, and to prevent fire of concrete structures. The purpose is to improve the reliability of the property. Another object is to improve the economical efficiency and workability of concrete structure construction by minimizing the amount of synthetic fibers kneaded in concrete.

[0007]

In order to solve the above-mentioned problems, the present invention focuses on the water-cement ratio of concrete as a quantity representing the physical properties of concrete. By adjusting both the amounts of the materials used, the peeling depth of the explosion of concrete was controlled. The following briefly describes the relationship between the peeling depth due to the explosion occurring in concrete and the water-cement ratio of concrete.

[0008] In general, in concrete, the smaller the water cement ratio, the greater the peeling depth due to explosion,
Conversely, it is known that the greater the water cement ratio, the smaller the peel depth due to the explosion. This is thought to be because the larger the water-cement ratio, the larger the pores in the concrete structure and the more easily water and air can pass through.

FIG. 3 is a graph showing an example of the relationship between the water-cement ratio of concrete and the explosion depth of concrete. The example given here is for steel
This is a case where a reinforced concrete column of 0 mm is heated by a method according to a fire resistance test specified in ISO834.

In FIG. 3, the vertical axis represents the dimension of the peeling depth due to the explosion of the concrete, and the horizontal axis represents the water-cement ratio of the concrete.の in the figure indicates that the synthetic fiber is not mixed into the concrete (the synthetic fiber mixed amount is 0.
0 kg / m ³ ), and the solid line is the result of linear regression of the data marked by ○. Thus, when the synthetic fiber is not mixed into the concrete, it can be seen that the explosion depth of the concrete decreases almost linearly as the water-cement ratio increases. Also, △ in the figure
Is the case where the synthetic fiber is mixed in the concrete at a rate of 1.0 kg / m ^3. According to this, if the water-cement ratio is the same, the synthetic fiber is 1.0 kg / m ^{3 in} the concrete.
/ M ³ , the peeling depth due to the explosion is 1
It can be seen that it can be reduced by 7 to 18 mm.

Table 1 below shows another experimental example different from the graph shown in FIG.

[Table 1] As is clear from this table, the explosion depth of concrete becomes smaller as the mixing ratio of synthetic fiber increases when the water-cement ratio is the same. There is a tendency that the larger the is, the smaller it becomes.

As described above, the present invention focuses on the fact that the depth dimension of explosion of concrete is affected by both the water-cement ratio of concrete and the amount of explosion-preventing material such as synthetic fibers. It was done.

In other words, the method for controlling explosion of a concrete structure according to the first aspect of the present invention is based on the assumption that the concrete structure receives a fire, and the service performance required for the concrete structure during and after a fire. Is set in advance, and based on the service performance, the amount of cross-sectional loss allowed for each member constituting the concrete structure is calculated, and occurrence is assumed in each of the members based on the amount of cross-sectional loss. The depth dimension of the explosion of the concrete is adjusted, and at the time of the adjustment, one or both of the water-cement ratio of the concrete constituting each member and the amount of the explosion-preventing material mixed into the concrete are adjusted. Features.

This method of controlling explosion of a concrete structure balances the depth dimension of the explosion expected to occur in each member constituting the structure with the water-cement ratio of the concrete and the mixing amount of the material for preventing explosion. In this way, accurate control can be performed, and thereby the cross-sectional loss of each member due to the explosion can be kept within an allowable range.

Further, the method for controlling explosion of a concrete structure according to claim 2 is a method for controlling explosion of a concrete structure according to claim 1, wherein the amount of cross-sectional defect allowed for each member and the service performance are provided. Based on both, determine the adjustable amount of the water-cement ratio of the concrete constituting each of the members, and from the adjustable amount of the water-cement ratio and the cross-sectional loss amount, to the concrete constituting each of the members It is characterized in that the amount of the material for preventing explosion to be mixed is determined.

In this method for controlling the explosion of a concrete structure, the water-cement ratio of the concrete is first adjusted in order to suppress the cross-sectional loss due to the explosion of each member to an allowable range. Considering that, it is possible to use a material for preventing explosion when the amount of sectional loss cannot be adjusted only by the water cement ratio. Therefore, it is possible to minimize the amount of the material for preventing explosion to be used.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a flowchart showing an example of a method for controlling explosion of a concrete structure according to the present invention. The method for controlling the explosion of a concrete structure according to the present embodiment, as shown in FIG.
To the block B3. In the block B1, the service performance of each member constituting the concrete structure after the fire is set, and in the block B2, the amount of section loss allowed for each member constituting the concrete structure is calculated. In B3, the separation depth dimension due to the explosion that is assumed to occur in each member during a fire is adjusted.

The post-fire service performance of each member set in the block B1 is based on the strength of the member when the member is a load-bearing member such as a column, a beam, a load-bearing wall, or the like. When the member is a non-bearing member such as a floor, a partition wall, or an outer wall, the fire prevention performance of the member is used. Further, in the block B2, the allowable amount of the cross-sectional loss of each member due to the explosion is calculated so as to realize the above-mentioned performance after the fire. Further, block B3
In, the water-cement ratio of concrete and the amount of synthetic fibers (material for preventing explosion) mixed into concrete are determined so that the cross-sectional loss due to explosion is equal to or less than an allowable amount.

Next, referring to the flowchart of FIG.
A procedure specifically performed in each of the blocks B1 to B3 shown in FIG. 1 will be described. As shown in FIG. 2, first, in the block B1, it is determined whether or not each member (column, beam, wall, or the like) constituting the concrete structure is a load-bearing member (step S1). If it is a load-bearing member, the expected strength performance of the member after the fire is set (step S2). If this is not a load-bearing member, the expected fire prevention performance of the member after the fire is set. (Step S3).

In the block B2, the strength performance set in the step S2 and the step S2
In order to realize the fire-prevention performance set in 3 above, the cross-sectional area and the cross-sectional width required for each member in the structural design or the fire prevention design are calculated. A cross-sectional defect amount allowed later is obtained (step S4).

Further, in the block B3, it is determined again whether or not each member is a bearing member (step S5). If this is a load-bearing member, the water-cement ratio is not adjusted because the compressive strength required for concrete is already determined in structural design. That is, the adjustable amount of the water-cement ratio is set to 0 (step S6), and the minimum amount of synthetic fiber that makes the cross-sectional loss due to the explosion of the concrete equal to or less than the allowable amount at this water-cement ratio is calculated (step S7). By kneading this amount of synthetic fibers into the concrete, the degree of explosion expected to occur in the concrete is controlled.

On the other hand, in the block B3, when the constituent members of the concrete structure are not load-bearing members, the compressive strength of the concrete structure is reduced to the extent that no problem occurs in the concrete, and the water-cement ratio can be adjusted in that case. The amount is calculated (step S8). Further, step S8
When the water-cement ratio of concrete is adjusted according to the adjustable amount of water-cement ratio calculated in the above, it is determined whether the amount of cross-sectional loss due to explosion is below the allowable amount without mixing synthetic fibers ( Step S9). In this case, when the assumed cross-sectional loss amount is equal to or less than the allowable amount, the degree of explosion expected to occur in concrete is controlled only by adjusting the water-cement ratio (step S10). If the amount of cross-sectional loss due to explosion cannot be suppressed to an allowable amount or less only by adjusting the cement ratio, the minimum amount of synthetic fiber to be reduced to the allowable amount or less is calculated (step S).
7) By kneading the calculated minimum amount of synthetic fibers into concrete, the degree of explosion expected to occur is controlled.

In the above-described method for controlling the explosion of concrete, the performance of the concrete structure at the time of fire and after the fire is set in advance, and the permissible amount of the cross-sectional loss due to the explosion that realizes this performance is calculated. In order to control the peeling depth due to the explosion within the allowable range, the amount of synthetic fiber mixed into the concrete must be controlled. And the ratio of concrete to water / cement.

Conventionally, as a measure for preventing explosion of concrete, it has been considered to simply adjust the amount of synthetic fibers mixed in concrete to adjust the peeling depth of explosion. In the embodiment, in addition to that, by adjusting the water-cement ratio of the concrete, it is possible to more accurately control the peeling depth due to the explosion of the concrete, as compared with the related art, and
By controlling the peeling depth within an allowable range, fire safety of the structure can be ensured.

Furthermore, according to the present embodiment, even in the conventional case where it is not possible to control the peeling depth due to the explosion within a safe range simply by adjusting the amount of the mixed synthetic fiber, By adjusting the water cement ratio, it is possible to respond.

As described above, according to the concrete structure explosion control method of the present embodiment, the reliability of the concrete structure with respect to fire safety can be improved as compared with the related art.

Further, in the above-described method for controlling the explosion of concrete, the water-cement ratio of the concrete is first adjusted in order to suppress the amount of cross section loss due to explosion of each member to an allowable range. In such cases, the amount of synthetic fiber mixed into concrete is adjusted. Therefore, compared with the case where the depth of the explosion is controlled simply by adjusting only the amount of the synthetic fiber mixed therein, the amount of the synthetic fiber used can be suppressed to be small. Work can be facilitated and economical fire safety design can be achieved.

In the above embodiment, as the type of the synthetic fiber to be mixed into the concrete as the explosion-proof material, for example, polypropylene, vinylon, polyethylene, polyvinyl chloride, nylon, polyethylene terephthalate and the like are preferable. Further, in this case, the dimensions of the fiber are about 5 to 50 mm in length and 10 to 100 μm in thickness.
As for the shape of the fiber having a length of about m, a monofilament type, a reticulated film type, a strand type or the like is suitably used.

In the above embodiment, a part of the configuration may be changed without departing from the gist of the present invention.

[0030]

As described above, in the method for controlling the explosion of a concrete structure according to the first aspect, the concrete structure is supposed to be subjected to a fire, and the concrete structure is subjected to the fire during and after the fire. The required service performance is set in advance, and based on the service performance, the allowable sectional loss of each member is calculated, and the water-cement ratio of the concrete and the concrete By adjusting the amount of the material for preventing explosion mixed in the concrete, the peeling size of the concrete due to the explosion is adjusted. As a result,
It is possible to more reliably control the peeling depth due to the explosion of the concrete, and by controlling this peeling depth within an allowable range, the fire safety of the structure can be ensured. Therefore, the reliability of the concrete structure with respect to fire safety can be improved as compared with the related art.

In the method for controlling the explosion of a concrete structure according to claim 2, the adjustable amount of the water-cement ratio of the concrete constituting each member is based on both the performance of the section loss allowed for each member and the service performance. Is determined, and from the adjustable amount of the water-cement ratio and the amount of cross-sectional loss, the amount of the material for preventing explosion to be mixed into the concrete constituting each of the members is determined. Compared to controlling the depth of explosion by adjusting only the amount of mixing, the amount of synthetic fiber used can be reduced, which enables economical fire safety design and concrete pouring. The work at the time of installation can be facilitated.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating an example of a procedure of a method for controlling explosion of a concrete structure according to the present invention.

FIG. 2 is a flowchart showing each block of the flowchart shown in FIG. 1 in detail.

FIG. 3 is a diagram illustrating an example of an experimental result obtained by heating reinforced concrete, and is a graph illustrating a relationship between a water-cement ratio of concrete and a burst depth.

Claims (2)

[Claims] 1. Assuming a case where a concrete structure receives a fire, service performance required for the concrete structure at the time of fire and after the fire is set in advance, and based on the service performance, Calculate the cross-sectional loss amount allowed for each member constituting the concrete structure, and adjust the peeling depth dimension due to the explosion of concrete expected to occur in each member based on the cross-sectional loss amount, A method for controlling the explosion of a concrete structure, comprising adjusting one or both of a water-cement ratio of concrete constituting each member and an amount of a material for preventing explosion mixed in the concrete. 2. The method for controlling explosion of a concrete structure according to claim 1, wherein the concrete of each of the members is formed based on both a cross-sectional loss amount permitted for each of the members and the service performance. While determining the adjustable amount of the water cement ratio, and determining the amount of the material for preventing explosion to be mixed into the concrete constituting each member from the adjustable amount of the water cement ratio and the cross-sectional loss amount. A method for controlling explosion of a concrete structure.