JP2008285862A - Ceiling structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance fire resistance, particularly, in consideration of an influence of heat radiation caused by a steel plate covering the outer periphery of a lighting, in a ceiling structure with the embedded-in-ceiling type lighting, excellent in the fire resistance. <P>SOLUTION: This ceiling structure is provided with the lighting fixture 2 which is inserted into an embedment opening 20, opened in a ceiling surface, from a bottom side, and in which the outer periphery of a lighting for applying light into an indoor space is covered with the steel plate 22. A ceiling board 11 composed of a rock-wool sound-absorbing plate is screw-fixed to undersurfaces of ceiling furring strips 12 which are arranged at a predetermined interval in parallel with each other, or placed among a plurality of supporting members 46 without being fixed. A steel beam 3 for supporting a floor board 41 on an upper floor is provided above the ceiling board 11, and composed of fire resisting steel. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a ceiling structure having a ceiling-embedded lighting fixture.

  Conventionally, steel frames have been used for beams and columns constituting steel structures such as apartment houses and buildings. For these steel beams and steel columns, the level of performance required for each member is stipulated by the number of floors as the time to withstand a normal fire in Article 107 of the Building Standard Law Enforcement Ordinance. Members meeting the criteria of Article 107 of the Ordinance are called fireproof structures and are approved by the Minister as satisfying the performance of the Article 107 of the Ordinance and those specified by the Minister (exemplified by the Ministry of Construction Notification No. 1399 in 2000) There are two types of fish.

  For this reason, a method has been devised for the latter in which a surface of a steel beam or a steel column is coated with a fireproof coating material having excellent fire resistance.

  For example, the Tiger board type Z (registered trademark) made by Yoshino Gypsum Co., Ltd. has a board thickness of 21 mm and surrounds the three surfaces except the upper surface in contact with the floor slab of steel beams. : FP060BM-9152). This Tiger board type Z (registered trademark) is a reinforced gypsum board, and is improved in fire resistance and strength at the time of fire by mixing inorganic fibers into normal gypsum board. In addition, for example, there is a one-hour fire-resistant structure (fireproof approved by the Minister of Land, Infrastructure, Transport and Tourism: FP060CN-0002) that surrounds four sides of a steel column with a board thickness of 21 mm of Tiger board type Z (registered trademark).

  On the other hand, a membrane method using a surface material such as rock wool sound absorbing board or gypsum board directly under the steel beam as a ceiling finishing material has been proposed as one of the techniques for improving the fire resistance performance of the steel beam.

  For example, in the technology disclosed in Patent Document 1, a floor structure and a ceiling material that form a ceiling space are made of a fireproof material, and a large beam and a small beam that support them are arranged in the ceiling space. The fireproof structure of is shown. This Patent Document 1 is intended for a three-story unit building, and the steel types of large beams and small beams are not particularly mentioned, but it can be estimated that it is 400 MPa class ordinary steel because of three stories. Further, it is disclosed that the ceiling material is formed of a fire resistant material having a fire resistance performance of 1 hour or more, such as a calcium silicate plate having a thickness of 25 mm or more, and is screwed to a steel field edge. It is also shown that when the entire space behind the ceiling, including beams and beams, is viewed as a floor, fire resistance of 1 hour or more can be obtained.

  Further, in Patent Document 2, a rock wool sound absorbing plate is used as a base material and a screw is fixed to a steel field edge, a gypsum board is used as an upper material, and an upper screw is used as a base material in a position that does not overlap with a base screw. A ceiling membrane structure that is penetrated and fixed to a steel field edge is disclosed. It can be seen from the description of claim 1 of this Patent Document 2 and the drawings that the ceiling material is double-tensioned, and that the second floor board 6 is indicated in the drawings, so that the two-story building is the object. In this Patent Document 2, because of the two-story structure, the steel type of the beam is not particularly mentioned, but it is a 400 MPa class ordinary steel, and the fire resistance of 1 hour or more as a membrane structure is a target. It can be inferred from technical common sense in the technical field.

Further, in Patent Document 3, a steel joiner is sandwiched between ceiling joint portions, a screw A that penetrates the steel joiner from the surface of the face material and reaches the steel field edge, and the steel joiner is used as a ceiling base. , A reinforcing structure for a ceiling joint in which a screw B reaching the steel joiner is driven is disclosed. From the technique disclosed in Patent Document 3, it is understood that a new ceiling joint reinforcement structure called a steel joiner and its construction are necessary to prevent the ceiling material from falling off.
JP 63-156143 A Japanese Patent Laid-Open No. 10-325204 Japanese Patent Laid-Open No. 11-30007

  By the way, when a plasterboard is used as a single board as a ceiling finishing material, or a double-ply structure using a plasterboard as an underlaying material and a rock wool sound absorbing board as an upholstery material, it receives heat from the fire relatively early. It will drop out. On the other hand, when the rock wool sound absorbing plate is configured as a single plate as a ceiling finishing material, or when the rock wool sound absorbing plate is made of a double tension structure with an underlay material, it falls off even if it receives heat from a fire. Hateful.

  For this reason, most of the conventional fireproof ceiling structures are intended to prevent the ceiling material from falling off.

  However, such a conventional fireproof ceiling structure hardly considers the existence of a lighting fixture embedded and fixed in the ceiling. The outer periphery of the lighting fixture embedded and fixed in the ceiling is covered with a steel plate. For this reason, the heat from the fire is absorbed by the steel plate, and the absorbed heat is radiated from the surface of the steel plate, so that the steel beam located immediately above the lighting fixture is heated by the radiation. As a result, the steel material temperature rises due to the radiant heat, the necessary high-temperature proof stress cannot be secured, and as a result, the steel beam collapses.

  Therefore, the present invention has been devised in view of the above-described problems, and the object of the present invention is a ceiling structure having a fire-resistant ceiling having a ceiling-embedded lighting fixture, particularly on the outer periphery of the lighting fixture. The purpose is to propose a ceiling structure that improves the fire resistance in consideration of the influence of heat radiation by the coated steel sheet.

  In order to solve the above-described problems, the present inventor fixed the ceiling plate made of rock wool sound absorbing plates to the lower surface of the ceiling field edge arranged in parallel with each other at a predetermined interval. A ceiling structure was invented in which a steel beam for supporting an upper floor is provided above and the material of the steel beam is made of fireproof steel.

  That is, the ceiling structure according to the present invention is a ceiling structure having a lighting fixture in which an outer periphery of an illumination unit that is inserted from a bottom side into a filling opening opened in a ceiling surface and irradiates light into an indoor space is covered with a steel plate. The ceiling plate made of rock wool sound-absorbing plate is screw-fixed to the lower surface of the ceiling field edge arranged in parallel with each other at a predetermined interval, or placed unfixed between a plurality of support members, A steel beam supporting an upper floor is provided above the ceiling plate, and the steel beam is made of refractory steel.

  In the present invention, the rock wool sound absorbing plate is used as the ceiling plate, and the fire-resistant steel having the above-described configuration is used as the steel beam. Therefore, in the ceiling structure excellent in fire resistance having the ceiling-mounted lighting fixture, It becomes possible to improve the fire resistance in consideration of the influence of heat radiation by the steel plate coated on the outer periphery of the lighting fixture.

  Hereinafter, as a best mode for carrying out the present invention, a ceiling structure excellent in fire resistance having a ceiling-embedded lighting fixture will be described in detail with reference to the drawings.

  FIG. 1 is a perspective view of a ceiling structure 1 to which the present invention is applied, and FIG. 2 is a front view thereof. The ceiling structure 1 includes a ceiling plate 11 that is screw-fixed to the lower surface of the ceiling edge 12, a lighting fixture 2 that is inserted and fixed to the filling port 20 opened in the ceiling plate 11 from the bottom side, and a ceiling plate 11 is provided with a steel beam 3 that supports a floor board 41 on an upper floor above 11, and a ceiling back space 4 is formed from the ceiling board 11 to the floor board 41.

  The ceiling board 11 consists of a rock wool sound-absorbing board, for example. This rock wool sound-absorbing plate is obtained by molding rock wool fibers with a starch binder, and is an interior material for ceilings that is lightweight and excellent in sound-absorbing properties, heat-insulating properties, workability, and design. By the way, this rock wool fiber is melted at a high temperature of 1500 to 1600 ° C. using blast furnace slag, basalt, and other natural rocks having excellent heat resistance as a main raw material, and then blown away by a centrifugal force into a fiber shape. An artificial mineral fiber.

  The ceiling field edge 12 is made of steel and is formed in a rectangular tube shape having a cross-sectionally B-shaped cross section. The ceiling field edges 12 are arranged in parallel to each other, and are fixed to each other in a state in which other ceiling field edges 13 are arrayed in a direction perpendicular to the ceiling field edges 12.

  The luminaire 2 includes a straight tube fluorescent lamp 21 as a light source for irradiating light into an indoor space. The straight tube fluorescent lamp 21 is detachably mounted on a socket holder (not shown) and is electrically connected to a commercial power source. Further, a steel plate 22 is formed on the outer peripheral side including the upper surface portion and the side surface portion of the straight tube fluorescent lamp 21. The steel plate 22 plays a role of protecting the straight tube fluorescent lamp 21 made of glass.

  The steel beam 3 is composed of an upper flange 31, a lower flange 32 and a web 33. A floor plate 41 is attached to the upper surface of the upper flange 31. The arrangement position of the steel beam 3 is described with reference to FIGS. 1 and 2, taking as an example the case where the steel beam 3 is mounted parallel to and directly above the lighting fixture 2, but is not limited to such a case. For example, the steel beam 3 may be attached to the lighting fixture 2 in an orthogonal direction, or may be attached in any direction.

  In the ceiling structure 1 to which the present invention is applied, refractory steel is used as the material of the steel beam 3. As a material of this refractory steel, for example, as shown in JP-A-2-77523, C is 0.04 to 0.15% by weight, Si is 0.6% or less, and Mn is 0.5 to 1. 1.6%, Nb 0.005-0.04%, Mo 0.4-0.7%, Al 0.1% or less, N 0.001-0.006%, the balance being Fe And after heating the steel piece which consists of an unavoidable impurity in the temperature range of 1100 degreeC-1300 degreeC, you may make it utilize what finished the hot rolling in the temperature range of 800-1000 degreeC.

  In addition, as shown in, for example, Japanese Patent Laid-Open No. 5-105947, the refractory steel as the material of the steel beam 3 is prepared by preliminarily deoxidizing molten iron and 0.003 to 0.015% by weight of dissolved oxygen. After being melted in the alloy, C is 0.04 to 0.20% by weight, Si is 0.05 to 0.50%, Mn is 0.4 to 2.0%, and Mo is 0.3% by addition of alloy -0.7%, V is 0.05-0.20%, N is 0.004-0.015%, Ti is 0.005-0.025%, and the balance is Fe and inevitable impurities. In addition, it is deoxidized by adding metal aluminum or ferroaluminum, the Al content is 0.005 to 0.015% by weight, and −0.004 with respect to dissolved oxygen [O%] of the molten steel. ≦ [Al%] − 1.1 [O%] ≦ 0.006 After reheating to a temperature range of 1100 to 1300 ° C., subjected to hot rolling, it may be used refractory steel manufactured by ending the rolling in a temperature range of from 750 to 1,050 ° C..

At this time, the steel beam 3, the yield stress at 600 ° C. has a tensile strength 400 N / mm in the ^second grade of steel 157N / mm ² or more, the tensile strength of 490 N / mm ² class steels 217N / mm ² You may make it use the steel materials which are the above.

Reason for using rock wool sound absorbing board as ceiling board 11

  In the ceiling structure 1 to which the present invention having the above-described configuration is applied, first, a rock wool sound absorbing plate is used as the ceiling plate 11. For this reason, it is possible to prevent the ceiling plate 11 from falling off even in a fire.

  FIG. 3A shows an upper flange 31, a lower flange 32, and a steel plate 3 with respect to the elapsed time in the ISO834 standard fire of a ceiling plate sample A using a 9 mm thick rock wool sound absorbing plate as the ceiling plate 11. The result of having investigated the relationship of the average temperature of the web 33 is shown. FIG. 3 (b) shows the ISO834 standard fire of a ceiling board sample B using a rock wool sound absorbing board having a thickness of 9 mm as the upper board and a 12.5 mm ordinary plaster board as the lower board. The result of having investigated the relationship of the average temperature of the upper flange 31, the lower flange 32, and the web 33 of the steel beam 3 with respect to the elapsed time is shown. In this experiment, the lighting fixtures 2 are not provided by opening the buried entrances in the ceiling plate samples A and B. That is, in this experiment, the temperature rise tendency of the steel beam 3 when the ceiling plate samples A and B are simply provided is examined excluding the influence of the lighting fixture 2.

  The ceiling board sample A gradually increases in temperature until the elapsed time exceeds 120 minutes, and exceeds 600 ° C. at this time. On the other hand, the temperature rise of the ceiling board sample B is more gradual until the elapsed time reaches 70 minutes, but when the elapsed time exceeds 70 minutes, the temperature rapidly rises and then cools. . This is because the ceiling plate sample B falls off after 70 minutes have elapsed, and the steel beam 3 positioned immediately above the sample directly receives heat. For this reason, it is shown from this investigation result that it is preferable to apply the ceiling board sample A from the viewpoint of preventing the falling off of the ceiling.

  Therefore, in the ceiling structure 1 to which the present invention is applied, the ceiling plate 11 is constituted by a single plate of a rock wool sound absorbing plate based on the experimental results described above.

Reasons for limiting to ceiling structures with recessed ceiling lighting fixtures

  In the ceiling structure 1 to which the present invention having the above-described configuration is applied, it is assumed that the lighting fixture 2 is embedded and fixed to the ceiling plate 11.

  As described above, the steel plate 22 is formed on the outer periphery of the lighting fixture 2. For this reason, in the ceiling structure 1 in which the lighting fixture 2 is embedded and fixed, heat from the fire is absorbed by the steel plate 22. The heat absorbed by the steel plate 22 is radiated to the ceiling space 4 side. As a result, the steel beam 3 disposed almost directly above the lighting fixture 2 in the ceiling space 4 is greatly affected by the heat radiated from the steel plate 22.

  Hereinafter, the result of investigating the influence of radiant heat on the steel beam 3 due to the presence of the lighting fixture 2 embedded and fixed to the ceiling plate 11 will be described.

  FIG. 4A shows the result of investigating the relationship of the temperature of the steel beam 3 with respect to the elapsed time in the ISO834 standard fire of the ceiling structure A having the ceiling plate 11 in which the lighting fixture 2 is embedded and fixed. Moreover, FIG.4 (b) has shown the result of having investigated the relationship of the temperature of the steel beam 3 with respect to the elapsed time in the ISO834 standard fire of the ceiling structure B in which the lighting fixture 2 is not arrange | positioned. Incidentally, in the ceiling structures A and B, a rock wool sound absorbing plate having a thickness of 15 mm is assumed as the ceiling plate 11. The temperature measurement was performed by attaching a thermocouple to the steel beam 3.

  In the ceiling structure A, the temperature of the steel beam 3 rises to about 600 ° C after 70 minutes from the occurrence of the fire, and the heating is finished because the temperature of the steel beam 3 reaches around 700 ° C after 80 minutes from the occurrence of the fire. is doing. On the other hand, in the ceiling structure B, the temperature rise gradient is gentle compared to the ceiling structure A, and reaches around 700 ° C. after 160 minutes from the occurrence of the fire.

  That is, the ceiling structure A provided with the lighting fixture 2 is significantly affected by the radiant heat from the steel plate 22 that has absorbed the heat from the fire, and the temperature rise of the steel beam 3 is abrupt. It is proved from the above experimental results that the ceiling structure B in which is not disposed is not particularly affected by the radiant heat from the steel plate 22, and therefore the temperature rise is moderate.

  For this reason, in the design of a fireproof ceiling structure against a fire, the presence or absence of the lighting fixture 2 can be a very dominant factor. When the ceiling structure is designed on the assumption that the lighting fixture 2 is not provided, the temperature rises faster than expected at the time of the design due to the influence of the lighting fixture 2, which is very dangerous. .

  Therefore, in the ceiling structure 1 to which the present invention is applied, it is assumed that the lighting fixture 2 is provided, and the ceiling structure 1 is limited to such a case, thereby reducing the influence of radiant heat from the steel plate 22 in the lighting fixture 2. It is clarified that it is a technical configuration for making it happen.

Reasons for using the above-mentioned refractory steel as the steel beam 3

  In the ceiling structure 1 to which the present invention having the above-described configuration is applied, the steel frame 3 uses the refractory steel having the above-described components.

  The upper part of FIG. 5 shows the result of investigating the relationship between the temperature of the steel beam 3 and the elapsed time in the ISO834 standard fire. In this figure, the allowable temperature of general steel is 450 ° C., the limit temperature of general steel is 550 ° C., the allowable temperature of refractory steel is 600 ° C., and the limit temperature of refractory steel is 650 ° C. Further, in the lower part of FIG. 5, the amount of deflection when general steel and refractory steel are used as the steel beam 3 is shown.

When general steel is used as the steel beam 3, the allowable temperature exceeds 450 ° C. after 45 minutes from the occurrence of the fire as shown in the upper part of FIG. 5, and the deflection amount increases rapidly as shown in the lower part of FIG. Resulting in. Then, after 60 minutes from the occurrence of the fire, the limit temperature reaches 550 ° C., and the deflection amount of the steel beam 3 exceeds L ² / 400d, leading to collapse (L is the distance between the fulcrum of the steel beam 3) And d is the height of the steel beam 3). By the way, this L ² / 400d is the maximum beam load in the load heating test at the designated performance evaluation organization (for example, the Japan Building Comprehensive Testing Laboratory Building Evaluation Center established Fire Resistance Performance Test Method 4.1 Fire Resistance Performance Test / Evaluation Method) If the deflection amount of the steel beam 3 exceeds this condition, which is a condition for determining the deflection amount, the steel beam 3 cannot always support the vertical load, and the ceiling structure is collapsed as it is.

On the other hand, when refractory steel is used as the steel beam 3, the limit temperature does not reach 650 ° C. until about 80 minutes from the occurrence of the fire as shown in the upper part of FIG. Until this time, the situation exceeding L ² / 400d is not reached. Thus, by using refractory steel as the steel beam 3, the collapse of the steel beam 3 can be delayed for a long time. In particular, as the steel beam 3, the yield stress at 600 ° C. is, in the tensile strength of 400 N / mm ² class steels 157N / mm ² or more, the tensile strength of 490 N / mm ² class steels 217N / mm ² or more Even in the case of using the steel material, it is possible to delay the collapse of the steel beam 3 over a long time.

  Article 107 of the Building Standards Law Enforcement Ordinance requires that the top floor and the number of floors counted from the top are 2 or more and within 4 and that rooftop pillars, beams, floors, and load-bearing walls are required to be fireproof for 1 hour, and a fire occurs. The ceiling structure must remain without collapse even after 1 hour has passed. In particular, in the present invention, when the lighting fixture 2 is used, as shown in FIG. 4 (a), the temperature may reach 600 ° C. after 70 minutes, but in the present invention, the steel beam 3 is used. By using refractory steel, even if it reaches 600 ° C., it is at an allowable temperature, and since it has not reached the limit temperature of 650 ° C., the collapse of the ceiling structure 1 itself can be suppressed. Specifically, the required fire resistance time of 72 minutes (= 60 minutes × 1.2 times) or more in the 1 hour fire resistance certification test is possible.

  The present invention is not limited to the embodiment described above. For example, as shown in FIG. 6, it may be applied as a ceiling structure 5 as another embodiment constructed by a so-called system construction method. In the ceiling structure 5, the same components and members as those of the above-described ceiling structure 1 are denoted by the same reference numerals, and the following description is omitted.

  The ceiling plate 11 is placed between the plurality of support members 46 without being fixed. The support members 46 are arranged in parallel with each other at a predetermined interval and are suspended through a hanging hanger (not shown). Of course, the above-described effects can also be obtained in this system construction method.

It is a perspective view of the ceiling structure to which the present invention is applied. It is a front view of the ceiling structure to which the present invention is applied. It is a figure which shows the relationship of the temperature of a steel beam with respect to the elapsed time in ISO834 standard fire. It is a figure which shows the result of having investigated the influence by the presence or absence of a lighting fixture regarding the relationship of the temperature of the steel beam with respect to elapsed time. It is a figure for demonstrating the effect by utilizing a refractory steel about the relationship of the temperature of the steel beam with respect to the elapsed time in ISO834 standard fire. It is a perspective view of the ceiling structure constructed by the system construction method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 5 Ceiling structure 2 Illumination fixture 3 Steel beam 4 Ceiling back space 11 Ceiling board 12, 13 Ceiling field edge 20 Implant 21 Direct pipe type fluorescent lamp 22 Steel plate 31 Upper flange 32 Lower flange 33 Web 41 Floor board 46 Support member

Claims (3)

In the ceiling structure having a lighting fixture in which the outer periphery of the lighting means that is inserted from the bottom side into the filling opening opened in the ceiling surface and irradiates light into the indoor space is covered with a steel plate,
The ceiling plate made of rock wool sound absorbing plate is screw-fixed to the lower surface of the ceiling field edge arranged in parallel with each other at a predetermined interval, or is placed unfixed between a plurality of support members,
A steel beam that supports the floor board of the upper floor is provided above the ceiling board,
A ceiling structure characterized in that the steel beam is made of refractory steel. That said steel beam is yield stress at 600 ° C. is, in the tensile strength of 400 N / mm ² class steels 157N / mm ² or more, the tensile strength of 490 N / mm ² class steels is 217N / mm ² or more The ceiling structure according to claim 1. Ceiling structure when performing fire tests steel beams for ceiling structure according to the claim 1 or 2, deflection of the steel beams start of heating after 72 minutes is equal to or more than L ^{2 /} 400d.
Here, L is the distance between the fulcrums of the steel beam, and d is the height of the steel beam.

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