JP2006152747A - Fire resistant concrete member and fire resistant segment member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a concrete member superior in explosion resistance for constructing a tunnel or an underground space. <P>SOLUTION: A reinforcement 121 constituted in a grating shape is arranged in a position of the predetermined cover thickness from one side surface of the concrete member 100. Steel fiber is mixed in concrete 112 for constituting the concrete member 100. A segment member is constituted by forming such a concrete member 100 in a curved shape in response to a wall surface shape of the tunnel and the underground space. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fireproof structure of a structure such as a reinforced concrete structure, and more particularly to a fireproof concrete member suitable as a segment member or the like that forms a wall surface of a tunnel or the like.

  When concrete is heated suddenly in the event of a fire, the surface of the concrete member may explode due to rapid expansion of the surface or rapid vaporization / expansion of moisture contained in the concrete, causing the surface layer to peel off. There is. Further, if the reinforcing member, which is a structural member, exceeds about 300 ° C. and the concrete exceeds about 350 ° C., the physical characteristics cannot be maintained, and the structural strength is reduced.

  Therefore, after construction of the concrete structure, it is necessary to perform fireproofing work such as installation of fireproof panels and spraying of fireproof coating materials. However, these methods require additional fireproofing work after concrete placement or precast concrete installation, which requires an extra work period and cost, and covers the surface of the concrete structure. It is difficult to check the situation.

Therefore, as a fireproofing method for preventing explosion without incurring the above-mentioned problems, Patent Document 1 includes a grid formed of steel on the outer periphery of columns, beams, etc. of an ultrahigh strength concrete structure. And a method using a refractory structure for forming a refractory concrete coating layer coated with outer peripheral concrete is described.
Japanese Patent No. 2860369

  However, the above technique is a fireproofing method related to pillars and beams of buildings in which pillars and beams are made of ultra-high-strength concrete, and it is not appropriate to use them as segment materials for tunnels and the like.

  The present invention has been made in view of the above problems, and the present invention provides a concrete member excellent in explosion resistance, which can be applied as a fireproof structure of a wall surface of a tunnel or underground space, which is likely to become a high temperature particularly in a fire. With the goal.

  In order to achieve the above object, the invention of claim 1 is a flat or curved plate-shaped reinforced concrete member provided with reinforcing bars configured in a lattice form at a predetermined cover thickness from one side surface. It is a plate-shaped reinforced concrete member characterized by having.

  A second aspect of the present invention is the reinforced concrete member according to the first aspect, wherein steel fibers are mixed in the concrete constituting the reinforced concrete.

  A third aspect of the present invention is a segment member in which the reinforced concrete member according to the first or second aspect is formed in a curved shape along a wall shape of a tunnel or underground space.

  When the concrete member is exposed to a high temperature, explosion occurs when the water vapor pressure generated in the interior of the concrete vaporizes and exceeds the yield strength of the surface concrete. On the other hand, according to the refractory concrete member of the present invention, the grid-like reinforcing bars restrain the concrete surface layer portion and bear the internal pressure generated by the vaporization and expansion of moisture inside. In addition, water vapor generated inside the concrete can be dissipated through the interface between the concrete and the reinforcing bar. For this reason, it becomes possible to suppress the explosion of concrete.

  In addition, by mixing steel fiber into concrete, the binding force of the concrete structure is improved, and the internal water vapor diffuses through the interface between the concrete and the steel fiber, thereby reducing the internal water vapor pressure. As a result, explosion can be suppressed more effectively.

  In addition, the refractory concrete member of the present invention has a structure in which lattice reinforcing bars are embedded in one surface of a plate-like concrete member, and only one surface thereof has fire resistance. For this reason, it can be easily applied to internal walls such as tunnels and underground spaces where the surface of structural concrete is exposed to high temperatures in the event of a fire.

  One embodiment of the concrete member of the above invention will be described with reference to the drawings. Fig.1 (a) shows sectional drawing of the refractory concrete member 100 which is one Embodiment of this invention, FIG.1 (b) shows the horizontal sectional view of the height containing a grid | lattice reinforcement.

  In the refractory concrete member 100 of the present embodiment, a plate-shaped reinforced concrete member 110 composed of a reinforcing bar 111 and a concrete 112 for a structural member is provided with a grid-like reinforcing bar 121 at a predetermined cover thickness position from one side surface 130 thereof. It is a configuration. The surface layer on the side where the lattice reinforcing bars 121 are provided functions as the refractory layer 120. In the present embodiment, the case where the refractory concrete member 100 has a flat plate shape is shown. However, when the refractory concrete member 100 is a segment member installed on a curved wall surface such as a tunnel wall surface, the refractory concrete member 100 corresponds to the wall surface shape. It is formed in a curved plate shape.

  In the present embodiment, the grid-like reinforcing bar 121 is provided at a predetermined cover thickness position from the surface of the reinforced concrete member 110. However, the grid-like reinforcing bar is positioned at the cover thickness position from the surface of the steel concrete member or the steel reinforced concrete member. It is good also as a structure which provides.

  According to the above configuration, even when the refractory layer 120 of the refractory concrete member 100 is exposed to a high temperature, the lattice-shaped reinforcing bars 121 are embedded at the position of the predetermined cover thickness, so that the moisture in the concrete is reduced. Even if it becomes water vapor and causes a large pressure in the concrete, the lattice rebar 121 bears the load due to the pressure. In addition, there is an effect that the water vapor is dissipated from the interface between the concrete 122 and the grid-like reinforcing bars 121 and the internal pressure is reduced. Thus, since the grid | lattice-like reinforcement 121 is embed | buried, it becomes possible to suppress the explosion of a concrete member.

  Further, even when a blasting occurs from the heating surface, the progress of the blasting stops at the grid-like reinforcing bars 121 of the refractory layer 120, so that a cross-sectional defect of the structural member can be prevented and a decrease in the proof stress of the structural member can be prevented. . Moreover, since the concrete 122 which remained without exploding functions as a heat insulation layer, the rise of internal temperature can be suppressed and progress of explosion can be suppressed.

  Here, the experiment regarding the explosion-proof performance of the refractory concrete member of the present invention will be described. In this experiment, as shown in Table 1, when a reinforcing bar diameter of 6 mm was used for the grid-like reinforcing bar 121, the pitch of the reinforcing bar was 100 mm, and the cover thickness of the reinforcing bar was 25 mm (Example I), Example I, diameter and cover When the pitch of the grid is 50 mm without changing the thickness (Example II), when the diameter of the reinforcing bar is 13 mm without changing the pitch of the grid and the reinforcing bar cover thickness of Example II (Example III) A comparison was made between Example III and the case where the cover thickness was 50 mm without changing the diameter of the reinforcing bar and the pitch of the grid (Example IV), and the case where there was no grid-like reinforcing bar 121 in the refractory layer 120 (Comparative Example).

[Table 1]

  The system used for the experiment will be described with reference to FIG. The concrete specimen 210 of the present invention is attached to the test furnace 200, heated by the burner 220, and the temperature at points of 50 mm, 100 mm, 150 mm, and 200 mm is measured using a thermocouple from the heating surface, and the fire resistance is compared. did. As heating conditions, a RABT curve simulating the rise in temperature in the tunnel was used, and measurements were performed on each of the specimens 210 in which the grid reinforcing bars 121 were formed as Examples I to IV and Comparative Example.

  Table 2 shows the depth of the concrete member that has been scraped off by the explosion (hereinafter referred to as the explosion depth) under each condition. When comparing each condition with a comparative example in which no grid reinforcing bars are provided, the average value of the explosion depths of Examples I to IV is smaller than that of the comparative example.

[Table 2]

  It can be confirmed that the explosion can be suppressed by providing the grid-like reinforcing bars 121 at a predetermined depth from the heating surface 130.

  FIG. 3 shows the maximum temperature at the measurement point for each condition. Compared with the comparative example in which the grid-like reinforcing bars 121 are not provided, the other Examples I to IV have a lower maximum temperature at all depths. This is because in the comparative example, the surface is scraped by explosion and the heat insulating effect of the concrete is reduced, and the temperature is transmitted more than in Examples I to IV. Also from this, by providing the lattice reinforcing bars 121, It can be confirmed that it becomes possible to improve fire resistance and prevent explosion.

  Furthermore, when Example I and Example II, Example I and Example III, Example III and Example IV are compared, the following can be confirmed. As in Example I and Example II, when other conditions are the same and only the lattice width of the lattice reinforcing bar 121 is changed, the fire resistance becomes stronger when the lattice width is reduced. Moreover, when the diameter of a reinforcing bar is compared like Example I and Example III, the one where the diameter of the reinforcing bar is larger becomes stronger in fire resistance.

  Increasing the number of reinforcing bars or increasing the diameter of the reinforcing bars increases the total cross-sectional area of the reinforcing bars. Since the binding force of the reinforcing bar is proportional to the cross-sectional area of the reinforcing bar, the binding force on the concrete is increased. Moreover, since the area of the interface between a reinforcing bar and concrete also increases, the amount of water vapor escaped inside the concrete increases and the internal pressure can be reduced. As described above, it can be confirmed from the above results that the explosion resistance is improved when the diameter of the reinforcing bar is increased or the lattice width is reduced.

  Furthermore, when Example III and Example IV are compared, it can be confirmed that the fire resistance becomes stronger as the cover thickness is smaller. This is because the progress of the explosion is stopped by the grid-like reinforcing bars, and when the cover thickness is larger, the surface layer portion is scraped off by the explosion, so that the heat insulation effect is reduced and heat is transferred to the inside of the concrete.

  Next, an experiment relating to the effect of mixing steel fibers into a concrete member will be described. A refractory concrete member (Condition A) using concrete not containing steel fibers and a refractory concrete member (Condition B) of the present invention using concrete containing steel fibers were subjected to a heating test using the same system as described above. It was. In both conditions A and B, no grid reinforcing bars are embedded near the surface.

[Table 3]

  Table 3 shows the measurement results of the explosion depth. Comparing the explosion depth, the maximum value and the average value of the concrete member containing steel fibers are smaller. Thereby, it can confirm that the resistance with respect to concrete peeling was strengthened and the explosion resistance improved by mixing steel fiber.

  Next, the fireproof segment member which is one Embodiment of this invention is demonstrated based on FIG.4 and FIG.5. FIG. 4 is a cross-sectional view of the refractory segment member 400 of the present embodiment, and FIG. 5 is a schematic view of the inner wall of a tunnel formed using the refractory segment member 400. As shown in FIG. 5, the refractory segment member 400 assembles a cylindrical body by mutually connecting the segment members that are in contact with each other, and is connected along the tunnel axial direction as the excavation progresses to form the inner wall surface of the tunnel. Is.

  Such a refractory segment member 400 is formed in a curved surface shape in which a cylindrical ring body is divided into a plurality along the circumferential direction. The refractory segment member 400 of the present invention has a surface vicinity by embedding a reinforcing bar 421 configured in a lattice shape at a predetermined cover thickness from the surface on the side that becomes the inner wall surface of the tunnel when the segment member is assembled. It functions as a refractory layer 420.

  According to the refractory segment member 400 configured as described above, by providing the lattice reinforcing bars 421 on the inner wall side 430 of the segment member, when the temperature rises suddenly due to a fire, the lattice reinforcing bars 421 resist the internal water vapor pressure. And the explosion of the segment member 400 can be suppressed.

  If the reinforcing bar 411 exceeds about 300 ° C. and the concrete 412 exceeds about 350 ° C., the physical properties cannot be maintained, and the structural strength is reduced. On the other hand, according to the present embodiment, the use of the grid-like reinforcing bars 421 can prevent the fireproof covering layer 420 from being damaged, suppress the temperature rise of the concrete 412 and the reinforcing bars 411, and maintain the structural strength. It is possible to prevent the collapse of the sagging tunnel.

  The concrete 412 and 422 constituting the refractory segment member 400 can be of a normal composition, but is preferably concrete mixed with steel fibers. By using steel fiber concrete, water vapor is diffused from the steel fiber interface and the internal water vapor pressure can be reduced, so that explosion can be prevented.

  Furthermore, mixing steel fibers into concrete corrodes the steel fibers existing in the surface layer, preventing the entry of chlorine ions and oxygen from the outside into the concrete, and corrosion of the reinforcing bars of structural members. Also has anti-corrosion effect to prevent.

  In ordinary concrete structures, fire resistance is not sufficient, and therefore, after the concrete is placed or after the precast concrete is installed, a fireproof work such as attaching a fireproof panel or spraying a fireproof coating is necessary. However, by using the concrete member of the present invention, it is not necessary to perform fireproofing work, so the construction period can be shortened and the cost can be reduced.

  Moreover, since the concrete member of the present invention does not require a separate fireproof coating, the concrete surface is exposed. For this reason, it becomes possible to confirm the crack and water leakage status by visual inspection.

Fig.1 (a) is sectional drawing of the concrete member of this invention, FIG.1 (b) is a horizontal sectional view in the surface where the grid | lattice-like reinforcing bar of the concrete member of this invention exists. It is the schematic of the installation which performs a fireproof experiment about the concrete member of this invention. It is the graph which compared about the maximum temperature of the fireproof test in various conditions using the concrete member of this invention. It is sectional drawing of the segment member of this invention. It is a schematic diagram of the tunnel inner wall surface formed using the segment member of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Refractory concrete member of the present invention 110 Reinforced concrete 111 Reinforcement 112 Structural concrete 120 Refractory layer 121 Lattice rebar 122 Fireproof covering concrete 130 Heating surface 200 Test furnace 210 Specimen 220 Burner 400 Refractory segment member 410 Structural member 411 Structural reinforcing bar 412 Structural concrete 420 Refractory layer 421 Lattice rebar 422 Refractory covering concrete 430 Heating surface (wall surface in the tunnel)

Claims (3)

  A flat or curved plate-like refractory concrete member, comprising reinforcing bars arranged in a lattice shape at a predetermined cover thickness from one surface.   The refractory concrete member according to claim 1, wherein steel fibers are mixed in the concrete. A segment member, wherein the refractory concrete member according to claim 1 or 2 is formed in a curved shape along a wall shape of a tunnel or underground space.