JPH11303245A - Explosion control method of concrete structure, method for predicting concrete explosion depth, and synthetic fiber mixed concrete having explosion resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly determine kinds, size and a use amount of synthetic fiber mixed in concrete while conditions with regard to performance required in a structure, workability and costs in executing the structure are considered. SOLUTION: At the time of a fire and after the fire, performance required to a concrete structure is previously set (B1), on the basis of the performance, a cross section loss amount allowed in each member constituting the concrete structure is calculated (B2), and on the basis of the cross section loss amount, peeling depth size by concrete explosion in which occurrence is assumed is adjusted (B3). At the time of adjustment, water cement ratio (water coupling material ratio) of concrete constituting each member, the kind of synthetic fiber mixed in concrete, size of the synthetic fiber, and one or more of the mixed rate of the synthetic fiber for 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, and a method for controlling the explosion of the concrete structure. The method for predicting the concrete explosion depth due to the explosion caused by the explosion caused by the explosion caused by the explosion, and the formation of the explosion phenomenon was suppressed by mixing synthetic fibers in advance. The present invention relates to explosion-resistant synthetic fiber-mixed concrete.

[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,
It is feared that the structure will be destroyed as this proceeds, and various explosion prevention measures are being studied.

It is said that the above-mentioned explosion phenomenon of concrete tends to occur more easily as the strength of the concrete is higher. One of the causes of the explosion is considered to be an increase in the water vapor pressure inside the concrete.

[0005] In view of this, synthetic fibers which melt in the event of a fire are mixed into concrete in advance, and in the event of a fire, the concrete is melted through voids formed by the melting of the synthetic fibers.
A method has been proposed in which water vapor inside concrete is released to the outside, thereby preventing the occurrence of explosion.

[0006]

However, to date, when mixing such a synthetic fiber into concrete, the difference in the strength of the concrete is not taken into account, and depending on the conditions, an effect of suppressing explosion is obtained. There was a problem that it was not possible.

The type, size, and amount of synthetic fibers to be mixed into concrete not only contribute to the degree of explosion prevention performance, but also increase the cost and workability when actually using a structure for construction. Has a significant effect. For example, the total amount of the types and amounts of synthetic fibers affect the construction cost, and the flowability of concrete changes depending on the size and amount of synthetic fibers. The workability at the time of installation will be affected. From these facts, considering the type of synthetic fiber to be mixed in and the amount of the related fiber, etc., work on construction of the structure while ensuring the reliability and soundness of the structure at the time of fire and after the fire There has been a demand for a technology that keeps performance and cost within appropriate ranges.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and determines the type, size and amount of synthetic fibers to be mixed into concrete to determine the performance and performance required for a structure. The purpose of this study is to provide technology for making appropriate decisions while taking into account conditions related to workability and costs.Specifically, concrete members are required to accurately control the degree of explosion that occurs during A method for controlling the explosion of a concrete structure that improves the reliability of the structure for fire safety, a method for estimating the explosion depth of concrete such that the peeling depth due to the explosion occurring in the concrete can be predicted in advance, and It is an object of the present invention to provide a synthetic fiber-mixed concrete having explosion resistance that can appropriately suppress the occurrence of explosion.

[0009]

Means for Solving the Problems To solve the above problems, the present invention employs the following means. That is,
The method for controlling explosion of a concrete structure according to claim 1 comprises:
Assuming that the concrete structure receives a fire, the 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, the concrete structure is Calculate the amount of cross-sectional loss allowed for each of the constituent members, and adjust the peeling depth dimension due to the explosion of concrete assumed to occur in each of the members based on the amount of cross-sectional loss. Adjust at least one or more of a water binder ratio of concrete constituting each member, a type of synthetic fiber mixed into the concrete, a size of the synthetic fiber, and a mixing ratio of the synthetic fiber to the concrete. It is characterized by the following.

[0010] Because of the above-mentioned configuration, in this method for controlling the explosion of a concrete structure, the difference in the strength of the concrete and the type, size, mixing amount, etc. of the synthetic fibers mixed in the concrete are determined. Can be reflected in the control of explosion phenomena.

The method for controlling explosion of a concrete structure according to claim 2 is characterized in that the water-binding material ratio of the concrete constituting each member is based on both the allowable cross-sectional loss of each member and the service performance. While determining the adjustable amount of the, the type of synthetic fiber to be mixed into the concrete constituting each member, the dimensions of the synthetic fiber, and the It is characterized in that the mixing ratio of the synthetic fiber to concrete is determined.

In this method for controlling the explosion of a concrete structure, in order to reduce the amount of cross-sectional loss caused by the explosion of each member due to the explosion of each member, first, the ratio of the water binder to the concrete (for example, the ratio of water cement) is set. In view of the service performance of the structure, when it is impossible to adjust the cross-sectional loss amount only by the water binder ratio, a material for preventing explosion can be used. Therefore, it is possible to minimize the amount of the material for preventing explosion to be used.

According to a third aspect of the present invention, there is provided a method for predicting a concrete explosion depth, the method comprising: estimating a concrete peeling depth associated with an explosion occurring on a surface of the concrete when the concrete is heated; The relationship between the mass reduction rate when the concrete is heated and the type of synthetic fiber mixed in the concrete, the size of the synthetic fiber, and the mixing rate of the synthetic fiber in the concrete is checked in advance, and the prediction is made. In this case, based on the type of synthetic fiber mixed in the concrete to be predicted, the size of the synthetic fiber, and the mixing ratio of the synthetic fiber to the concrete, it is assumed that the concrete occurs when the concrete is heated. The mass loss rate is predicted, and based on the predicted mass loss rate and the water binder ratio in the concrete to be predicted, Characterized by calculating the peeling depth Te.

According to the method for predicting the explosion depth of concrete, the type of the synthetic fiber, the size, and the mixing ratio with the concrete are calculated through the physical property amount of the mass reduction ratio of the concrete. It can be taken into account for explosion depth prediction.

[0015] The explosion-resistant synthetic fiber-mixed concrete according to claim 4 is used at a temperature of 100 ° C to 3 ° C with respect to the concrete.
A synthetic fiber that undergoes volume reduction due to softening or melting at 00 ° C. or decomposes and volatilizes is 0.05 vol% to 0.5 vol
%.

Due to the above-mentioned structure, in the synthetic fiber mixed concrete, the volume of the synthetic fiber mixed in the concrete is reduced at the time of fire, or the synthetic fiber is decomposed and volatilized, so that the concrete is mixed. Voids are generated inside, thereby enabling the water vapor in the concrete to be released to the outside.

The explosion-resistant synthetic fiber-mixed concrete according to claim 5 is the explosion-resistant synthetic fiber-mixed concrete according to claim 4, wherein the concrete has a water binder ratio of 35% or less. The synthetic fiber has a length and a diameter of 6 to 50 mm and 10 to 500 μm, respectively.

In order to obtain the water binder ratio as described above,
This concrete mixed with synthetic fibers can exhibit sufficient strength, and since the length of the synthetic fibers is within the above range, the workability (fluidity) of the concrete is reduced. Without significant damage
The required explosion prevention performance can be obtained. Further, since the diameter of the synthetic fiber is in the above-described range, a continuous void sufficient to release the internal water vapor pressure, which is one of the causes of the explosion, to the outside of the member can be formed.

[0019]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram 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.
It is composed of four procedures from 1 to block B4.

In the block B1, the retained fire resistance performance of each member constituting the concrete structure and the required fire resistance performance required for each member are determined, and the retained fire resistance performance and the required fire resistance performance are compared. Note that, in this case, the possessed fireproof performance includes fireproof performance and proof stress performance that can be exhibited after a fire when a blast occurs in the concrete constituting the member.

If it is determined in the block B1 that the retained fire resistance exceeds the required fire resistance, it is not necessary to adjust the explosion of the member, so that the explosion control is terminated.

On the other hand, if it is determined that the possessed fire resistance is lower than the required fire resistance, the block B2 calculates the allowable cross-sectional loss due to the explosion in the member to be controlled in the block B2 based on the required fire resistance. I decided to.

In this case, in the following block B3, the adjustment amount of the water cement ratio (water binder ratio) in the member to be subjected to the explosion control is determined based on the permissible amount of the sectional loss calculated in the block B2. Do.

At this time, specifically, first, it is determined whether or not the water-cement ratio can be adjusted in the member to be controlled for explosion. If the water cement ratio can be adjusted, a calculation is made as to how much the water cement ratio should be adjusted so that the cross-sectional loss due to the explosion can be controlled within an allowable amount. Furthermore, if the cross-section loss can be controlled within the allowable range within the adjustable range of the water-cement ratio calculated in this way, the cross-section loss is within the allowable range only by adjusting the water-cement ratio. And the explosion control method ends.

If it is impossible to adjust the water cement ratio or if it is determined that the amount of cross-sectional loss cannot be controlled within the allowable amount by adjusting only the water cement ratio, in the next block B4, Determine the type and dimensions of the synthetic fiber mixed into the concrete and the mixing ratio of the synthetic fiber into the concrete, taking into account the workability of the member and the required strength characteristics, etc., so that the cross-sectional loss is within the allowable amount. I will go.

Next, with reference to the flowcharts shown in FIGS. 2 to 4, a procedure specifically performed in each of the blocks B1 to B4 shown in FIG. 1 will be described. As shown in FIG. 2, in the block B1, first, conditions for a structure of a member to be controlled by the explosion phenomenon (hereinafter, referred to as a target member) are set (step S1). Then, step S1
From the conditions set in the above, various conditions required for the workability, strength characteristics, durability and fire resistance required for the target member are set (step S2).

Next, based on the workability, strength characteristics, and durability among the various conditions set in step S2, a base concrete to be used in the target member (concrete serving as a base before mixing synthetic fibers) is determined. Then, referring to the experimental results, etc., the explosion depth expected to occur when this base concrete is subjected to a fire under predetermined conditions is predicted. If it occurs in the member, the fire resistance performance and the proof stress performance that the target member can exhibit during and after the fire are predicted (step S3).

On the other hand, the fire resistance required for the target member is set based on the fire resistance of the target member set in step S2. Specifically, first, it is determined whether or not the target member is a load-bearing member in the structure (step S4). If the target member is a load-bearing member, the target member is subjected to a fire, and the explosion phenomenon causes the fire. Even if the cross-sectional area is reduced, the minimum proof stress performance to be exhibited during and after the fire is set (step S5). If the target member is not a load-bearing member, even if the target member receives a fire and its cross-sectional area decreases due to the explosion, the minimum partition performance to be exhibited during and after the fire is set (step S).
6).

Then, the retained fire resistance performance of the target member set in step S3 (the fire resistance performance and proof stress performance held by the target member) and the required fire resistance performance of the target member set in step S5 or step S6 (during fire and fire) (The minimum load-bearing performance or compartment performance required later)
(Step S7). If the possessed fire resistance exceeds the required fire resistance, control of the explosion phenomena is not required for the target member. Then, control of the explosion is terminated (see FIG. 4). On the other hand, when the possessed fire resistance performance of the target member is lower than the required fire resistance performance, the process proceeds to the next block B2 in order to perform a new procedure related to explosion control.

In the block B2, the cross-sectional area and the width of the cross-section of the target member necessary for the target member to have a performance higher than the required fire resistance performance are calculated, whereby the target member is allowed to stand after the fire. The amount of cross-sectional loss is calculated (step S8), and thereafter, the process proceeds to the figure.

As shown in FIG. 3, after performing the procedure up to FIG. 2, it is determined in block B3 how much the water cement ratio of the target member is adjusted. That is, first, it is determined whether or not the target member is a load-bearing member in the structural design (step S9). If the target member is a load-bearing member, the strength of the target member determined in the structural design is determined. Since it is impossible to lower the strength (if the strength of the load-bearing member is reduced, the entire structural design must be redone), there is no room for adjusting the water-cement ratio. It is assumed that the adjustable amount of the water-cement ratio (water-binding material ratio) of the concrete that constitutes is 0 (step S10).
In addition, when the target member is not a structural load-bearing member, it is possible to reduce the strength of the target member to some extent. The quantity is calculated based on the partition performance and the like required for the target member (step S11). Then, within the range of the water cement ratio adjustable amount calculated in step S11, it is determined whether or not the sectional loss amount of the target member can be controlled within the allowable amount only by adjusting the water cement ratio (step S11). S1
2) If controllable, only the water cement ratio (water binder ratio) is adjusted (step S13), and the process shifts to the one shown in the figure without performing a new procedure relating to the control of explosion. The control of the explosion is terminated (see FIG. 4).

On the other hand, if the adjustable amount of the water cement ratio is set to 0 in step S10,
In 12, when it is determined that it is impossible to control the cross-sectional loss amount due to the explosion within the allowable amount by adjusting only the water cement ratio, the next block B5 is executed in order to perform a new procedure related to explosion control. (In the figure).

In block B5, as shown in FIG. 4, first, the type of synthetic fiber to be mixed with concrete is determined (step S14). In this case, an appropriate type of synthetic fiber is determined in consideration of the material cost of the synthetic fiber and the like. Next, the allowable range (A) of the fiber diameter, length, and mixing ratio is calculated from the allowable cross-sectional loss amount of the target member obtained earlier (step S15).
In calculating the allowable range (A), when a predetermined type of synthetic fiber is mixed into concrete in advance, the diameter and length of the mixed synthetic fiber, the mixing ratio with concrete, and the mixing ratio in the concrete. Calculate the relationship with the explosion depth to be generated, and use this calculation result to determine the allowable range of the synthetic fiber diameter, length, and mixing ratio with concrete so that the cross-sectional loss is within the allowable range. And The method of calculating the explosion depth of concrete when any synthetic fiber is mixed (expected explosion depth prediction method) will be described later.

After calculating the permissible range (A) of the fiber diameter, length, and mixing ratio in step S15, the diameter and length of the synthetic fiber are set so that the workability of the target member is within the permissible range. , And the allowable range (B) of the mixing ratio is calculated (step S16). In this case, specifically, the relationship between the diameter, length, and mixing ratio of the fiber mixed with the concrete and the slump flow of the concrete mixed with the fiber is examined by experiments and the like, and from this relationship, The specifications (diameter, length, and mixing ratio of the fiber) of the synthetic fiber are calculated so that the slump flow of the synthetic fiber mixed concrete falls within a predetermined allowable range.

Further, after that, the range of the strength characteristic required for the target member is set based on, for example, the proof stress performance or the partitioning performance set in step S5 or step S6, and the strength characteristic of the target member is set to this value. The allowable range (C) of the diameter, the length, and the mixing ratio of the synthetic fiber is calculated so as to fall within the range of the required strength characteristic set as described above (step S17). In this case, the relationship between the diameter, length, and mixing ratio of the fiber mixed with the concrete and the compressive strength of the synthetic fiber mixed concrete is examined in advance by experiments, etc., and from this relationship, the synthetic fiber mixed Specifications for synthetic fibers that are within the range of concrete compressive strength and required strength characteristics (fiber diameter, length,
And the mixing ratio).

Then, steps S15, S16, S17
The range of the diameter, the length, and the mixing ratio of the synthetic fiber that satisfies all the allowable ranges (A), (B), and (C) of the diameter, the length, and the mixing ratio of the synthetic fiber calculated in (1) are examined ( Step S18). At this time, these (A), (B),
If there is a range that satisfies all of (C) (that is, (A∩B∩C) ≠ φ), the synthetic fiber within this range (ie, (A∩B∩C)) The diameter, the length, and the mixing ratio with respect to the concrete are determined (step S24).

On the other hand, when there is no range that satisfies all of (A), (B), and (C) (that is, (A∩B∩)
In the case of C) = φ), first, under the condition of (A), it is determined whether the workability, the strength characteristics, or both of them can be improved by using the admixture in the base concrete of the target member. (Step S1
9).

When the workability and strength characteristics of the target member can be improved by using the admixture, the workability and strength characteristics of the improved target member are confirmed (step S21). It is checked whether these workability and strength characteristics are good (step S22).
The determination as to whether or not the workability and strength characteristics are good in step S22 is based on the fact that these workability and strength characteristics are within the allowable range of workability and the required strength characteristics based on the calculations in steps S16 and S17. It is determined based on whether or not. If it is determined in step S22 that the workability or strength characteristics are good, the diameter, length, and mixing ratio of the synthetic fibers are determined within the range of (A) (step S24). Further, when it is determined that the workability or the strength characteristic is not good, it is determined whether another fiber other than the fiber determined in step S14 can be substituted (step S23). If the substitute can be made with another fiber, the process returns to step S14 to determine the fiber type again. If the substitute cannot be made with another fiber, the process returns to step S19.
The admixture mixed with the base concrete will be adjusted to determine whether the workability or strength properties can be improved.

If it is determined in step S19 that the workability and strength characteristics of the target member cannot be improved even by the use of the admixture, the tolerance of the target member is increased by increasing the section size of the member or by means of fireproof coating. The cross-sectional loss is increased (step S20), and the diameter, length, and mixing ratio of the synthetic fiber to be mixed are determined based on the conditions set in step S20 so as to satisfy other conditions (step S20). Step S24). Then, as shown in the figure, when the diameter, length, and mixing ratio of the synthetic fiber are determined in step S24, the present method is terminated.

Next, a method of estimating the explosion depth for calculating the explosion depth of an arbitrary synthetic fiber used in step S15 will be described. The method for predicting the explosion depth is based on the general presumption of the mass loss rate of the concrete when the concrete is heated, the type of the synthetic fiber mixed in the concrete, the size of the synthetic fiber, and the mixing rate of the synthetic fiber in the concrete. When examining the physical relationship and actually predicting the concrete peeling depth,
Based on this relationship, the mass loss rate was calculated from the type and size of the synthetic fiber mixed into the concrete to be predicted, and the mixing ratio of the synthetic fiber, and the calculated mass loss rate and the water-cement ratio of the concrete to be predicted were calculated. Thus, the structure is used to check the peeling depth due to the explosion occurring in the concrete.

For example, the relationship between the mass reduction rate of the concrete when the concrete is heated, the type of synthetic fiber mixed in the concrete, the size of the synthetic fiber, and the mixing rate of the synthetic fiber in the concrete is shown in FIG. 5 and FIG. This can be represented as a graph as shown in FIG.

FIGS. 5 and 6 show a cylindrical specimen having a diameter of 150 mm and a height of 300 mm formed of concrete mixed with synthetic fiber having a water cement ratio of 25% by the method specified in ISO834. It is the experimental result which investigated the mass reduction rate of the concrete specimen at the time of heating for 1 hour. FIG. 5 shows the results of an experiment using polyolefin fibers as synthetic fibers, and FIG.
It is an experimental result at the time of using a polyvinyl alcohol type fiber as a synthetic fiber.

Here, an index indicating the correlation with the explosion depth is defined as follows using the mass reduction rate obtained from the test experiment results at the specimen level shown in FIGS. (Index indicating correlation with explosion depth: I _WD ) = (mass reduction rate) ^1/3 According to this, the type, size, and mixing rate of synthetic fiber are determined by the physical property amount of mass reduction rate and the explosion depth. Can be related. Therefore, various types, dimensions,
The explosion depth can be empirically calculated by examining the mass reduction rate of the concrete mixed with the synthetic fiber having the mixing ratio.

On the other hand, the explosion depth of concrete is also affected by the water-cement ratio of concrete. FIG.
Is a graph showing an example of the relationship between the water-cement ratio of the concrete and the explosion depth of the concrete, the example given here is a reinforced concrete column with a cover thickness of the reinforcing steel of 40 mm,
This is a case in which heating is performed by a method according to a fire resistance test specified in ISO834.

In FIG. 7, the vertical axis shows the dimension of the peeling depth due to the explosion of the concrete column, and the horizontal axis shows the water-cement ratio of the concrete. In the figure, ○ indicates that the synthetic fiber is not mixed into the concrete (the synthetic fiber mixing amount is 0.
0 kg / m ³ ), and the solid line is a linear regression of the data marked with ○. Thus, when the synthetic fiber is not mixed in the concrete, it can be seen that the explosion depth of the concrete decreases almost linearly as the water-cement ratio increases.

In the figure, △ indicates the case where polyolefin fiber (diameter: 100 μm, length: 19 mm, mixing ratio: 0.1 vol%) was mixed into concrete, and according to this, the water-cement ratio was reduced. If they are the same, it can be seen that by mixing a certain amount of synthetic fibers of a predetermined shape into concrete, the peeling depth due to explosion can be reduced by 17 to 18 mm.

From these facts, it was found that the given polyolefin fiber (diameter: 100 μm, length: 19 mm, mixing ratio: 0.1 vol%)
It is considered that when water is mixed in concrete, the depth of delamination due to explosion changes with the same slope as the solid line in the figure, as shown by the broken line in the figure, by changing the water-cement ratio of the concrete.

Therefore, the value of the y-intercept of the regression equation shown by the broken line in FIG. 7 (that is, the explosion depth of the synthetic fiber mixed concrete when the water-cement ratio of the concrete is 25%) is shown in FIG. Assuming that there is a correlation with the _IWD obtained from the above experimental results, the concrete, in which the type, size, and mixing ratio of the mixed synthetic fiber is arbitrary, and the water cement The explosion depth can be predicted in consideration of the ratio.

In this case, the formula for calculating _IWD using the experimental results as shown in FIGS. 5 and 7 and further converting _IWD to explosion depth is as follows.

(Equation 1) In the above equation, ・ 57.4 is the value of the y-intercept of the regression equation for fiber-free concrete shown in Fig. 7 ・ 19.7 = 57.4-39.7, where 39.7 is the value of the y-intercept of the regression equation for fiber-concrete concrete ・ 2.03 is Polyolefin fiber (diameter: 100 μm, length: 19
mm, mixing ratio: slope of the regression equation in I _WD · 2.37 is I _WD · 0.968 no fibers mixed concrete 7 to about 0.1 vol%)

Using the method as described above, the blasting depth of a reinforced concrete column mixed with polyolefin fibers is predicted by changing the fiber diameter, length, mixing ratio, and water-cement ratio of the concrete. Table 1 below shows the obtained values.

[Table 1]

Table 2 below shows the results of the experiments shown in FIGS. 6 and 7 using the same method as described above, and based on the fiber diameter, length, and fiber length for the reinforced concrete columns mixed with polyvinyl alcohol-based fibers. It is a table which shows the predicted value of the explosion depth by changing the mixing ratio and the water-cement ratio of the concrete.

[Table 2]

The main configuration of the method for controlling the explosion of a concrete structure in the present embodiment has been described above.
A specific example in the case where the above explosion control method is actually applied to the design of a structure will be described.

[Conditions of Target Member] The preconditions for the target member in performing the explosion control are as follows. 1. Member condition Pillar 2. Conditions required for concrete (conditions related to workability, strength characteristics and durability)-Water-cement ratio of concrete: 30%-Slump flow required for concrete: 60 cm ± 10
cm · concrete required compression strength: 90 N / mm ² or more concrete formulation strength: 110N / mm ² 3. Fire resistance Strength members: Load bearing capacity during and after a 3-hour fire (standard fire)

[Example of Control of Explosion Phenomenon According to Flow]
Here, based on the above preconditions, FIGS.
An example in which the explosion control of a concrete structure is actually performed will be described with reference to the flowchart shown in FIG.

(Step S1) Based on the above prerequisites, the member condition is set to pillar. (Step S2) From the above preconditions: ・ Conditions related to workability: Slump flow of concrete is 60 cm ± 10 cm.・ Conditions for strength characteristics and durability: water-cement ratio of concrete is 30% and compressive strength is 90N
/ mm ² or more, and the compounding strength is 110 N / mm ² .・ Conditions for fire resistance: It is necessary to have a load-bearing capacity during and after a 3-hour fire (standard fire).

(Step S3) Based on the conditions set in step S2, the preparation of the base concrete (concrete containing no fiber) is determined. Subsequently, the fire condition is set to a standard fire of 3 hours, and the explosion depth is predicted. The prediction of the explosion depth in this case is performed based on the known experimental data shown in FIG. 7, and specifically, the explosion at a water cement ratio of 30% in the regression equation graph shown by the solid line in FIG. Read the depth. Thus, the explosion depth when a standard fire is applied to the base concrete is estimated to be 29 mm. Furthermore, based on the above fire conditions and the explosion depth expected to occur when synthetic fibers are not mixed into the base concrete, it is exhibited when the target member is formed from the base concrete (without mixing synthetic fibers). In this design example, detailed calculations are omitted, and it is assumed that the fire resistance is 2 hours.

(Step S4) Since the target member is a pillar, it is determined that the target member is a bearing member, and the routine goes to the next step S5.

(Step S5) From the above preconditions and the result of step S4, it is necessary that the target member has a load supporting capacity during and after a 3-hour fire (standard fire). Is set as the proof stress performance.

(Step S7) From the results of step S3 and step S5, "retained fire performance <required fire performance"
Becomes

(Step S8) Here, it is assumed that the cross-sectional defect amount allowed for the target member is calculated. However, detailed calculations are omitted for simplicity, and the right value is assumed. "Allowable cross-sectional loss: 10 mm".

(Step S 9) Here, since the column as the load-bearing member is handled, the flow shifts to step S 10.

(Step S10) According to the result of step S9, the water cement ratio cannot be adjusted, and the adjustable amount of the water cement ratio is set to 0, and the process proceeds to step S14.

(Step S14) In consideration of material costs, polyolefin fibers are used here. (Step S15) The allowable range (A) of the fiber diameter, length, and mixing ratio is selected based on the allowable cross-section loss set previously and the explosion depth prediction results shown in Table 1. However, regarding the predicted value of the explosion depth at an arbitrary fiber mixing ratio, the mixing ratio of 0% and 0.05%, the mixing ratio of 0.05%
% And 0.10%, and 0.1% and 0.3
It is assumed that linear interpolation can be performed in each of three sections of the% section. That is, it can be calculated by the following equation.

(Equation 2) Here, α: fiber mixing ratio (%) when explosion depth X _D (mm) α _L : maximum value (%) of mixing ratio in the section to be interpolated α _S : minimum value of mixing ratio in the section to be interpolated (%) X _D : Explosion depth desired to be controlled (mm) _XL : Explosion depth at contamination rate α _L (mm) X _S : Explosion depth at contamination rate α _S (mm)

In Table 1, the range of the mixing ratio at which the water cement ratio is 30% and the explosion depth is 10 mm can be read as follows.・ In the case of fiber diameter 100μm, length 12mm: section of 0.1% to 0.3% of mixing rate ・ In case of fiber diameter 100μm, length 19mm: mixing rate of 0.05% to 0.1%
・ Section of fiber diameter 48μm, length 10mm: Mixing rate of 0% to 0.05% ・ Section of fiber diameter 48μm, length 20mm: Mixing rate of 0% to 0.05%

From these readings and the equation (1), the mixing ratio at which the explosion depth is equal to or less than the allowable value is as follows.・ For fiber diameter 100μm, length 12mm: 0.17% or more of mixing rate ・ For fiber diameter 100μm, length 19mm: mixing rate of 0.075% or more ・ For fiber diameter 48μm, length 10mm: mixing rate of 0.04% or more ・ Fiber 48 μm diameter and 20 mm length: 0.037% or more

(Step S16) Next, from the allowable range of workability required for the target member, the fiber diameter, length,
The allowable range (B) of the mixing ratio is calculated. As shown in the above precondition, the allowable range of workability of the target member is that the slump flow of the concrete is 60 cm ± 10 cm.

By the way, the relationship between the slump flow of the concrete and the mixing ratio of the synthetic fibers is as shown in FIGS. These FIGS.
FIG. 8 is a graph showing the experimental results of the relationship between the slump flow ratio of fiber-concrete concrete to the slump flow of base concrete and the mixing ratio of synthetic fibers.
Medium, solid line is a regression equation when synthetic fiber of diameter 48μm, length 10mm is mixed into concrete, and broken line is diameter 48μm,
The regression formula when synthetic fiber having a length of 20 mm is mixed with concrete is shown. In FIG. 10, the solid line is the regression formula when synthetic fiber having a diameter of 100 μm and a length of 12 mm is mixed with concrete. , The broken line is diameter 100μm, length 19mm
Respectively show the regression formulas when the synthetic fibers of the above are mixed into concrete.

The slump flow of the base concrete is set to 60
cm, slump flow after fiber mixing is 60 ± 10cm
In order to satisfy the condition, the ratio of “slump flow of fiber-concrete concrete” to “slump flow of base concrete” must be 0.84 or more and 1.17 or less. Taking this into account, the following mixing rate is read from the graphs of FIGS. 8 and 10 so that the slump flow is within the allowable range.

When the fiber diameter is 100 μm and the length is 12 mm: the mixing rate is 0.27% or less. When the fiber diameter is 100 μm and the length is 19 mm: the mixing rate is 0.24% or less. When the fiber diameter is 48 μm and the length is 10 mm: the mixing rate is 0.23%. -When the fiber diameter is 48 µm and the length is 20 mm: the mixing rate is 0.19% or less

(Step S17) Next, the allowable range (C) of the fiber diameter, length, and mixing ratio is calculated from the strength characteristics required for the target member. As indicated in the previous assumptions, the strength properties required for the target member, Formulation strength of the base concrete 110N / mm ^2, the required compression strength is 90 N / mm ^2, further, wherein It is assumed that the concrete strength after fiber incorporation must be 105 N / mm ² or more.

The relationship between the compressive strength of concrete and the mixing ratio of synthetic fibers is shown in FIGS. 9 and 11 through experiments. These FIGS. 9 and 1
1 is a graph showing an experimental result of a relationship between a ratio of the strength of the fiber-mixed concrete to the strength of the base concrete and a mixing ratio of the synthetic fiber. In FIG. 9, the solid line is 48 μ in diameter.
m, the regression equation when mixing synthetic fiber with a length of 10 mm into concrete, the broken line indicates the regression equation when mixing synthetic fiber with a diameter of 48 μm and 20 mm in length into concrete, and In FIG. 11, the solid line indicates a diameter of 100 μm and a length.
The regression equation when the synthetic fiber of 12 mm is mixed in the concrete, and the broken line shows the regression equation in the case of mixing the synthetic fiber having a diameter of 100 μm and a length of 19 mm into the concrete.

When the mixing strength of the base concrete and the concrete strength required after mixing the fibers are set as described above, the ratio of the “fiber-mixed concrete” to the “strength of the base concrete” must be 0.96 or more. Taking this into consideration, a fiber mixing ratio that makes the strength of the fiber-mixed concrete equal to or more than a predetermined amount is calculated from the graphs of FIGS. 9 and 11 as follows.

When the fiber diameter is 100 μm and the length is 12 mm: the mixing rate is 0.19% or less. When the fiber diameter is 100 μm and the length is 19 mm: the mixing rate is 0.17% or less. When the fiber diameter is 48 μm and the length is 10 mm: the mixing rate is 0.3%. -When the fiber diameter is 48 µm and the length is 20 mm: the mixing rate is 0.25% or less

(Step S18) Here, step S18
15, S16, S17, whether or not there is a range (A∩B∩C) that satisfies all the diameters, lengths, and mixing ratios (A), (B), and (C) of the fibers obtained. Find out.

Based on the above results, the mixing ratio of the fiber satisfying A∩B∩C can be obtained as follows.・ When the fiber diameter is 100μm and the length is 12mm: 0.17% or more 0.1
9% or less ・ Fiber diameter 100μm, length 19mm: 0.075% or more
17% or less-Fiber diameter 48μm, length 10mm: mixing rate 0.04% or more 0.3%
-When the fiber diameter is 48 µm and the length is 20 mm: the mixing ratio is 0.037% or more and 0.2
5% or less

(Step S24) Here, step S24
The fiber having the smallest fiber mixing ratio is selected from the range of the fiber diameter, length, and mixing ratio (A∩B 混入 C) determined in step 18. In this case, a fiber having a diameter of 48 μm and a length of 20 mm is selected. As for the mixing rate, a safety factor for preventing explosion is assumed to be 10%. Based on these, the following fibers are selected in controlling the explosion of the target member.

· Type: polyolefin fiber · Diameter: 48 µm · Length: 20 mm · Mixing ratio: 0.04 vol%

In the above-described method for controlling the explosion of a concrete structure, the service performance of the concrete structure at the time of fire and after the fire is set in advance, and the allowable amount of the cross-sectional defect due to the explosion that realizes the service performance is set. In order to control the peeling depth due to the explosion within the allowable range, the respective members constituting the structure are controlled. It is configured to adjust at least one or more of water cement ratio (water binder ratio) of concrete used for concrete, kind and size of synthetic fiber mixed into concrete, and mixing ratio of synthetic fiber to concrete. I have. Conventionally, as a measure for preventing explosion of concrete, simply changing the amount of synthetic fibers mixed in concrete to adjust the peeling depth of explosion was considered. By adjusting the water cement ratio (water binder ratio) of the concrete, the type and size of the synthetic fiber to be mixed into the concrete, and the mixing ratio of the synthetic fiber to the concrete, the concrete can be more accurately compared to the conventional method. It is possible to control the peeling depth due to the explosion, and to control the peeling depth within an allowable range, thereby ensuring the fire safety of the structure.

Furthermore, according to the present embodiment, even in the case where the peeling depth due to the explosion cannot be controlled within a safe range simply by adjusting the amount of the synthetic fiber to be mixed in the related art, By adjusting the type and size of the synthetic fiber to be mixed and the water cement ratio (water binder ratio) of the concrete, it is possible to cope with the problem. In addition, by considering the type, dimensions, and mixing ratio of synthetic fibers, it is possible to control explosion in a form that reflects material costs, workability of structures, required strength characteristics, and the like.

As described above, according to the method for controlling the explosion of a concrete structure according to the present embodiment, it is possible to improve the reliability of the concrete structure with respect to fire safety as compared with the related art, and to improve the structure. It is possible to control explosion by reflecting various conditions in constructing an object.

Further, in the above-described method for controlling the explosion of a concrete structure, first, the water-cement ratio (water-binder ratio) of the concrete is adjusted in order to keep the amount of cross-sectional loss due to the explosion of each member within an allowable range. If this is not possible, the type and size of the synthetic fibers and the mixing ratio with concrete are adjusted. Therefore, compared to the case where the depth of the explosion is controlled simply by adjusting only the amount of the synthetic fiber mixed, the amount of the synthetic fiber used can be reduced,
This makes it possible to facilitate the operation of placing concrete and to achieve an economical fire safety design.

The method for predicting the explosion depth used in the above explosion control method for a concrete structure is based on the following methods: the mass reduction rate when the concrete is heated, the type and size of the synthetic fiber mixed in the concrete, and the Before examining the relationship with the synthetic fiber mixing ratio and predicting the explosion depth, the type of synthetic fiber mixed into the concrete to be predicted, the dimensions of the synthetic fiber, and the mixing of synthetic fiber into the concrete Based on the rate, we first estimate the rate of mass loss expected to occur when concrete is fired, and calculate the expected rate of mass loss and the water cement ratio (water binder ratio) in the concrete to be predicted. It is configured to predict the concrete peeling depth based on the

Thus, it is possible to incorporate the type, size, and mixing ratio of the synthetic fiber into the concrete into the prediction of the explosion depth through the physical property amount of the mass reduction rate of the concrete. In doing so, accuracy can be improved. In addition, by using the physical property amount of the mass reduction rate of the concrete, the prediction can be performed in consideration of the nonlinearity of the influence of the type and size of the synthetic fiber and the mixing ratio of the synthetic fiber on the explosion depth.

As described above, the concrete used in designing and constructing a structure in consideration of the explosion resistance of concrete includes the fiber mixing ratio and mass reduction as shown in FIG. 5 or FIG. As can be seen from the relationship with the rate, the fiber mixing rate is 0.05 vol% or more, since a remarkable effect of reducing the mass reduction rate can be obtained, the fiber mixing rate is preferably set to 0.05 vol%. is there. In addition, if the fiber mixing ratio is excessive, the strength of the concrete is reduced, or, since there is a risk of causing problems when kneading the fiber in the concrete, the fiber mixing ratio is, 0.5 vol% or less is preferable. In addition, the effect of preventing explosion of concrete by mixing synthetic fibers is because the synthetic fibers are heated and the volume decreases or disappears, forming an escape path for water vapor in the concrete, and the water vapor is easily released to the outside. Therefore, it is desirable that the synthetic fiber be one which causes a volume reduction by softening or melting or decomposes and volatilizes at 100 ° C to 300 ° C.

In this case, the water cement ratio (water binder ratio) of the concrete is determined in consideration of the strength of the concrete.
It is better to be 35% or less, and by setting the length of the synthetic fiber within the range of 6 to 50 mm, without significantly impairing the workability (fluidity) of the concrete,
The effect of reducing explosion of concrete can be obtained. Furthermore, if the diameter of the synthetic fiber to be mixed is 10 to 500 μm,
Not only can a continuous void be formed enough to release the internal water vapor pressure, which is one of the causes of the explosion, to the outside of the member, but also the concrete explosion phenomenon can be improved without significantly impairing the workability (fluidity) of the concrete. A reduction effect can be obtained.

[0086]

As described above, according to the method for controlling explosion of a concrete structure according to the first aspect, conventionally, as a measure for preventing explosion of concrete, the amount of synthetic fibers mixed in concrete is changed. Adjusting the water binder ratio of concrete, the type and size of synthetic fiber to be mixed into concrete, and the mixing ratio of synthetic fiber to concrete, while only considering adjusting the peeling depth of the explosion As a result, it is possible to control the peeling depth due to the explosion of concrete more accurately than in the past, and by controlling this peeling depth within an allowable range, the fire safety of the structure can be improved. Can be secured. Furthermore, according to the present embodiment, conventionally, even when 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 type and size of the fiber and the ratio of the water binder in the concrete, it is possible to cope with the problem. In addition, by considering the type, dimensions, and mixing ratio of synthetic fibers, it is possible to control explosion in a form that reflects material costs, workability of structures, required strength characteristics, and the like.

In the method for controlling the explosion of a concrete structure according to the second aspect, the ratio of the water-binding material 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. If this is not possible, we will adjust the type, size and mixing ratio of the synthetic fiber to the concrete, so we will try to control the depth of the explosion by simply adjusting only the amount of the synthetic fiber mixed. Compared to the case, the amount of synthetic fiber used can be reduced, thereby making it possible to facilitate the work during concrete casting and to enable an economical fire safety design. .

In the method for predicting the explosion depth of concrete according to the third aspect, the type, size, and mixing ratio of the synthetic fiber into the concrete are incorporated into the prediction of the explosion depth through the physical property of the mass reduction rate of the concrete. It is possible to improve the accuracy in estimating the explosion depth as compared with the related art. In addition, by using the physical property amount of the mass reduction rate of the concrete, the prediction can be performed in consideration of the nonlinearity of the influence of the type and size of the synthetic fiber and the mixing ratio of the synthetic fiber on the explosion depth.

In the concrete mixed with synthetic fibers according to the fourth aspect, the synthetic fibers which are softened or melted at 100 ° C. to 300 ° C. or whose volume is reduced, or the synthetic fibers which decompose and volatilize are 0.05%
Since vol% to 0.5 vol% is mixed, the mass reduction rate due to the explosion phenomenon at the time of fire can be suppressed well, and the safety of the structure at the time of fire can be improved. In addition, since the mixing ratio of the synthetic fibers does not become excessive, it is possible to secure workability when kneading the synthetic fibers into the concrete.

In the concrete mixed with synthetic fiber according to claim 5, the ratio of the water binder to the concrete is 35% or less, and the length and diameter of the synthetic fiber are 6 to 50 mm, respectively.
And 10 to 500 μm, it is possible to obtain a good explosion prevention effect while maintaining the strength of the concrete at a predetermined level, and also to ensure the fire resistance of concrete members while securing the workability of concrete required for construction. Can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing 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 details of procedures in blocks B1 and B2 of the block diagram shown in FIG. 1;

FIG. 3 is a flowchart showing details of a procedure in a block B3 of the block diagram shown in FIG. 1;

FIG. 4 is a flowchart showing details of a procedure in a block B4 of the block diagram shown in FIG. 1;

FIG. 5: 150 mm diameter formed by concrete mixed with synthetic fiber having a water cement ratio (water binder ratio) of 25%,
It is a figure which shows the experimental result at the time of heating a cylindrical test object of 300 mm in height by the method prescribed | regulated by ISO834 for 1 hour, and the mass reduction rate of the concrete test sample when using a polyolefin-type fiber as a synthetic fiber. 6 is a graph showing the relationship between the ratio of the synthetic fibers and the mixing ratio of the synthetic fibers.

FIG. 6: 150 mm diameter formed by concrete mixed with synthetic fiber having a water cement ratio (water binder ratio) of 25%;
It is a figure which shows the experimental result at the time of heating the cylindrical test object of 300 mm in height by the method prescribed | regulated by ISO834 for 1 hour, and the mass reduction of the concrete test sample when a polyvinyl alcohol type fiber is used as a synthetic fiber. It is a graph which shows the relationship between a rate and the mixing rate of a synthetic fiber.

FIG. 7 is a view showing an experimental result when a reinforced concrete column having a covering thickness of a reinforcing bar of 40 mm is heated by a method according to a fire resistance test specified in ISO 834, wherein a water cement ratio of concrete (water binder ratio) is shown. 6 is a graph showing the relationship between the depth of a concrete column and the explosion depth.

FIG. 8 shows the results of experiments on synthetic fiber-mixed concrete mixed with synthetic fibers having a fiber diameter of 48 μm, a fiber length of 10 mm, and a length of 20 mm, and the ratio of the slump flow of the synthetic fiber concrete to the slump flow of the base concrete and the ratio of the synthetic fiber. It is a graph which shows the relationship with a mixing ratio.

FIG. 9 is an experimental result of a synthetic fiber-mixed concrete mixed with a synthetic fiber having a fiber diameter of 48 μm, a fiber length of 10 mm, and a fiber length of 20 mm, showing a ratio of a slump flow of the base concrete to a slump flow of the synthetic fiber concrete, and a ratio of the synthetic fiber. It is a graph which shows the relationship with a mixing ratio.

FIG. 10 Fiber diameter 100 μm, fiber length 12 mm, 19 m
FIG. 9 is a graph showing experimental results on concrete mixed with synthetic fibers containing m synthetic fibers, showing the relationship between the ratio of the slump flow of synthetic fiber concrete to the slump flow of base concrete and the mixing ratio of synthetic fibers.

FIG. 11 Fiber diameter 100 μm, fiber length 12 mm, 19 m
6 is a graph showing experimental results on concrete mixed with synthetic fibers containing m synthetic fibers, showing the relationship between the slump flow ratio of the base concrete and the slump flow of the synthetic fiber concrete and the mixing ratio of the synthetic fibers.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasuyuki Yamazaki 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu Corporation (72) Inventor Toshio Yonezawa 1-5-1, Otsuka, Inzai City, Chiba Pref. Inside Takenaka Corporation Technical Research Institute (72) Inventor Akio Kodaira 1-5-1, Otsuka, Inzai City, Chiba Prefecture Inside Takenaka Corporation Technical Research Institute (72) Inventor Hideo Fujinaka 1-5-1, Otsuka, Inzai City, Chiba Prefecture Takenaka Corporation Technical Research Institute Co., Ltd. (72) Inventor Takeo Mitsui 1-5-1, Otsuka, Inzai City, Chiba Prefecture Inside Takenaka Corporation Technical Research Center

Claims (5)

[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, At the time of the adjustment, at least one of the water binder ratio of the concrete constituting each member, the type of the synthetic fiber mixed into the concrete, the size of the synthetic fiber, and the mixing ratio of the synthetic fiber to the concrete. A method for controlling the explosion of a concrete structure, characterized by adjusting the number of explosions. 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. Determine the adjustable amount of the water binder ratio, and, based on the adjustable amount of the water binder ratio and the cross-sectional loss amount, the types of synthetic fibers to be mixed into the concrete constituting each member, A method for controlling explosion of a concrete structure, comprising determining a size and a mixing ratio of the synthetic fiber to the concrete. 3. A prediction method for predicting a delamination depth of a concrete accompanying a burst phenomenon occurring on a surface of the concrete when the concrete is heated, wherein a mass reduction rate when the concrete is heated is determined in advance. The relationship between the type of the synthetic fiber mixed in the concrete, the dimensions of the synthetic fiber, and the mixing ratio of the synthetic fiber in the concrete is checked beforehand. Based on the type of the synthetic fiber, the size of the synthetic fiber, and the mixing ratio of the synthetic fiber with the concrete, a mass reduction rate expected to occur when the concrete is heated is predicted, and the predicted mass is calculated. Calculating the peeling depth based on a reduction rate and a water binder ratio in the concrete to be predicted. Explosion depth prediction method of the REIT. 4. The concrete is characterized in that the volume of the synthetic fiber is reduced by softening or melting at 100 ° C. to 300 ° C. or the synthetic fiber which decomposes and volatilizes is mixed at 0.05 vol% to 0.5 vol%. Explosion-resistant synthetic fiber mixed concrete. 5. The synthetic fiber-mixed concrete having explosion resistance according to claim 4, wherein the concrete has a water binder ratio of 35% or less, and has a length dimension and a diameter as the synthetic fiber. However, synthetic fiber mixed concrete having explosion resistance, characterized in that concrete having a size of 6 to 50 mm and 10 to 500 μm, respectively, is used.