Patent Application
20120240487
1. Field of the Invention
The present invention relates to an installation structure of a base of an exterior wall that can be used at the time of external renovation of a wooden framework house in order to improve a seismic performance of the house.
2. Description of Related Art
An example of conventional methods for improving the seismic performance of a wooden framework house is a structure in which an iron bracing material (brace) or frame material is attached to an outer side of a building for reinforcement. However, even though such a method has an advantage in that an occupant of a house can dwell in that house during reinforcement work because the reinforcement material is installed externally, the bracing material or the frame material attached to the outer side of an exterior wall will significantly reduce the aesthetic appearance of the house.
On the other hand, in the case of a seismic performance improvement method in which the reinforcement work is performed from the interior of a building, even though an existing exterior wall can be left intact and reused, the occupant comfort during a reinforcement work period will be significantly impaired, and furthermore, despite the costly repair work, an improvement in the quality of the house such as renewal of the appearance of the house cannot be achieved.
When many years have elapsed after a house was built, a mismatch occurs between the lifestyle of the occupant and the room layout or the interior design of the house. Thus, the occupant desires to renovate the interior of the building in accordance with a change in the lifestyle of the occupant. Furthermore, these days, there also have been increasing demands for exterior renovation, that is, renewal of the appearance of buildings, in addition to interior renovation.
Performing interior and exterior renovation simultaneously with seismic reinforcement of a building is desirable in that it is less wasteful of resources than constructing a new building.
As a method for improving the seismic performance of a wooden framework house at the same time as performing exterior renovation of that building, a method that uses a bearing face material as an exterior wall base member is known.
In this method that uses the bearing face material as the exterior wall base member, after removal of an existing external wall, a decayed or deteriorated portion of a skeleton of the house is repaired and joint metals are placed in proper positions, and then the bearing face material is installed, and this reinforcement is followed by finishing with ceramic siding or the like. The above-described method is widely known as a method that can perform seismic reinforcement and exterior renovation at the same time in compliance with diverse construction specifications.
JP 2010-7454A
JP 2006-28805A
JP 2003-3676A
JP 2003-3592A
When performing exterior renovation of wooden framework houses using a bearing face material as the exterior wall base member, it is required to perform the most suitable seismic reinforcement for various construction conditions of existing buildings, including differences in base configurations, such as the pillar size, the presence or absence of a stud, and a reinforcing post; differences in building elements, such as an ordinary wall portion, a corner wall portion, and an opening wall portion; and the like. When an existing building experiences seismic reinforcement, seismic design is performed with respect to the building whose structure has already been completed. Thus, unlike seismic design for construction of a new building, there are many restrictions, and it is required to perform seismic design under restrictions on the degree of freedom of design. Therefore, there are cases where only some of bearing walls are required to have a high wall strength factor.
As a method for enhancing the wall strength factor of only some of bearing walls, a method in which the wall strength factor of a bearing face material is changed by increasing the weight per unit area thereof by, for example, changing the type of the bearing face material according to the required wall strength factor is conceivable. However, the method in which the type of some of bearing face materials is changed leads to an increase in the number of types of bearing face materials and thus impairs the ease of installation. Moreover, although it is also possible to use bearing face materials of the same type with different thicknesses, this method leads to the occurrence of unevenness in the wall base member, and therefore this method significantly impairs the ease of installation as well.
As a method for enhancing the wall strength factor other than the above-described methods, a method in which the number of nails to be driven in to fix the bearing face material to a structural member of a wooden framework house is increased or the thickness of the nails is increased is conceivable. However, increasing the number of nails to be driven in causes cracking of the bearing face material or the structural member and thus increases the likelihood of an installation defect. On the other hand, the method in which the thickness of the nails is increased increases the risk of breakage of the bearing face material by a nailhead, that is, the occurrence of punching shear and the resulting breakage of the bearing face material by the nail. In particular, in the case of a bearing face material having a low specific gravity, the risk of breakage increases. Thus, it is not easy to enhance the wall strength factor by the method in which the number of nails to be driven in is increased or the method in which the thickness of the nails is increased.
Air permeability for discharging moisture within a house to the outside of the house is one of important performances requisite for a bearing face material. Known examples of a bearing face material having good air permeability are low-specific-gravity bearing face materials having an air dried specific gravity of about 0.6 to 1.0, such as softwood plywood, an MDF, a volcanic silicates fiber reinforced multi-layer board, and a pulp-silicate mixed cement board. However, due to the low specific gravity, these bearing face materials have low nail-holding power and also are susceptible to punching shear, and therefore it has not been easy to achieve a high wall strength factor with these materials.
The present invention has been made to solve problems as described above, and it is an object thereof to obtain a base of an exterior wall that can be used in external renovation of a wooden framework house in which a highly air-permeable bearing face material is used as an exterior wall base member and that provides a high degree of freedom of seismic design and, furthermore, facilitates installation of an exterior material such as ceramic siding after seismic reinforcement.
In order to solve the problems as described above, a first aspect of the present invention proposes a installation structure of a base of an exterior wall that can be used in external renovation of a wooden framework house in which a bearing face material is used as an exterior wall base member, wherein a reinforcement member for preventing punching shear is interposed between a bearing face material of a wall that is required to have a high wall strength factor by a seismic design and a nailhead of a nail for fixing the bearing face material to a structural member.
According to a second aspect of the invention, the reinforcement member is temporarily attached to the bearing face material beforehand.
According to a third aspect of the invention, at least two nails are driven in a single, continuous piece of the reinforcement member.
According to a fourth aspect of the invention, a type and a thickness of the bearing face material of the wall that is required to have a high wall strength factor by the seismic design are the same as those of a bearing face material of a wall that is not required to have a high wall strength factor.
According to a fifth aspect of the invention, the nails are of a single type and a single size.
According to a sixth aspect of the invention, the reinforcement member is a thin steel sheet.
According to a seventh aspect of the invention, the reinforcement member is a sheet selected from a glass fiber sheet and a carbon fiber sheet.
Hereinafter, the operation and effects of the present invention will be described.
As numerical values for judgement for evaluating means for enhancing the wall strength factor, single shear capacity of a nailed connection was used to perform the evaluation. As a method for determining the shear capacity of a nailed connection in which a bearing face material is used as a side member, the reference allowable stress and reference rigidity of joints (based on a monotonous loading test of joints) described in the “2002 Wakugumikabekoho Kenchikubutsu Kozokeisan Shishin (2002 guidelines for structural calculation of wood frame construction buildings)” of the Japan Two-by-Four Home Builders Association were adopted, and the single shear capacity of a nailed connection was determined.
This test was conducted using Japanese cedar as a structural member 1 serving as a main member; a sheet of structural plywood, a volcanic silicates fiber reinforced multi-layer board (manufactured by Daiken Corporation; product name: Dailite MS), and a pulp-silicate mixed cement board coated with an acrylic resin on both sides (manufactured by Nichiha Corporation; product name: Anshin), all having a thickness of 9 mm, as a bearing face material 2 serving as a side member; an iron wire nail N50 and an iron wire nail N75 (JIS A 5508:2009) as a nail 3; and a prepainted hot-dip 55% aluminum-zinc alloy-coated steel sheet (JIS G 3322:2008) having a thickness of 0.35 mm as a reinforcement member 4.
The results of the above-described test are shown in Table 1 below.
In the case where the reinforcement member 4 was not employed and the N50 nail 3 was used, when a load 5 was applied, “pull-out”, which is a form of breakage of a nailed joint, occurred for all of the bearing face materials. Specifically, in “pull-out”, a nail body 3b slips out of the structural member 1 while a situation in which a nailhead 3a cuts into the bearing face material 2 to cause the nail 3 to come out does not arise, as shown in
In the case where the reinforcement member 4 was not employed and the N75 nail 3 was used, when the load 5 was applied, “punching shear”, which is a form of breakage of a nailed joint, occurred for all of the bearing face materials. Specifically, in “punching shear”, the nailhead 3a cuts into the bearing face material 2 to cause the nail 3 to come out of the bearing face material 2 before the nail body 3b slips out of the structural member 1, as shown in
In the case where the reinforcement member 4 was employed and the N75 nail 3 was used, when the load 5 was applied, “pull-out”, which is a form of breakage of a nailed joint, occurred for all of the bearing face materials. Specifically, in “pull-out”, the nail body 3b slips out of the structural member 1 while a situation in which the nailhead 3a cuts into the bearing face material 2 to cause the nail 3 to come out does not arise, as shown in
As described above, with the installation structure of a base of an exterior wall according to the present invention, even when a combination susceptible to punching shear, of the bearing face material 2, the structural member 1, and the nail 3 is used, it is possible to prevent punching shear by interposing the reinforcement member 4 between the nailhead 3a and the bearing face material 2. Accordingly it is possible to achieve a high load value of shear capacity of nailed connection.
Therefore, in external renovation of a wooden framework house, even when a bearing face material that has good air permeability but is regarded as having a low strength against pull-out by a nailhead is used, it is possible to achieve a high wall strength factor by adopting the installation structure, in which a reinforcement member for preventing punching shear is interposed between a bearing face material serving as an exterior wall base member and a nailhead for fixing the bearing face material to a structural member, for a wall that is required to have a high wall strength factor by seismic design calculation. Therefore, a flat base of a wall can be obtained even when nails of a single type are used together with bearing face materials of the same type and the same thickness, and thus it is possible to perform design and installation in such a manner that walls having a high wall strength factor and walls having an ordinary wall strength factor coexist.
Therefore, the use of the installation structure of a base of an exterior wall according to the present invention eliminates the necessity to use an additional reinforcing metal fitting in order to enhance the wall strength factor, makes it possible to form a flat and smooth-surfaced base of a wall, and thus facilitates installation of an exterior material. Furthermore, since a bearing face material having good air permeability can be used, it is possible to impart a high wall strength factor to only a wall that is required to have a high wall strength factor by seismic design calculation while adopting a bearing face material having good air permeability. Consequently, an installation structure of a base of an exterior wall that provides a high degree of freedom of seismic design and a great ease of installation can be obtained.
Hereinafter, the best mode for carrying out the present invention will be specifically described with reference to the drawings.
With the installation structure of a base of an exterior wall according to the present invention, seismic reinforcement of an exterior wall portion of an existing conventional wooden framework house is performed in the following manner: an existing exterior building material is removed, and then a bearing face material serving as an exterior wall base member is retrofitted for seismic reinforcement, and then a finishing material such as ceramic siding is installed for exterior renovation.
In order to design for seismic reinforcement, seismic design is performed using a wall strength factor of each installation specification that is defined for each bearing face material designated for each pillar size, framework configuration, and building element.
First, an exterior wall of a portion to be renovated of a house that experiences exterior renovation is removed to reveal a skeleton. Then, if a sill, a pillar, or the like is decayed or deteriorated, it is repaired or replaced.
In the present invention, the cross-sectional size of pillars, sills, beams, girths, and crossbeams is set to at least 105×105 mm, and bearing walls have pillars at their ends. It should be noted that the size of studs is set to at least 27×105 mm, and the cross-sectional size of joint studs on which bearing face materials are joined is set to at least 45×105 mm.
In the case where the pillars have different cross-sectional sizes, an adjustment material such as wood can be used to level an exterior surface. The adjustment material is required to be reliably attached to a pillar or a stud using an iron wire nail or the like.
With respect to capitals and bases of the pillars, a pull-out preventing measure appropriate for the wall magnification (effective magnification) of the relevant portions is taken in conformity with a previously created seismic reinforcement plan.
It should be noted that when an adhesive tape is previously affixed to a surface of the reinforcement member 4 that comes into contact with the bearing face material 2, the necessity to use the covering tape is eliminated, and therefore the ease of installation and the installation quality are improved.
The bearing face material 2 is attached to the pillar 10, the sill 12, the girth 8, the studs 9, and the like by nailing the bearing face material 2 and the reinforcement member 4 on top of it with the N50 nails 3 driven at intervals of 100 mm or less along the perimeter and at intervals of 200 mm or less along a central line. At this time, the edge distance of the nails 3 (the distance from an edge of the bearing face material to nailing positions) is set to about 15 mm. Moreover, the distance to which the bearing face material overlaps the sill 12, the pillar 10, or the like is set to at least 30 mm. The nails 3 are driven into portions where the base frame is present, and too small and too large driving depths of the nails 3 should be avoided.
The bearing face material 2 is a rectangular material having a predetermined standardized size and the strength or functions of a bearing wall. For example, a bearing face material composed of structural plywood compliant with the JAS standards, a particleboard compliant with the JIS standards, an MDF, a volcanic silicates fiber reinforced multi-layer board, a pulp-silicate mixed cement board, or the like and having predetermined airtightness and dampproofness can be used. In addition to a single-layer board, composite boards composed of two or more different types of boards can be adopted as the bearing face material.
Particularly preferable examples of the bearing face material 2 in the present invention include highly air-permeable bearing face materials having an air dried specific gravity of about 0.6 to 1.0, such as softwood plywood, an MDF, a volcanic silicates fiber reinforced multi-layer board, and a pulp-silicate mixed cement board.
Preferable examples of the reinforcement member 4 include thin steel sheets having such a thickness that allows the nails to easily pass through, that is, a thickness of about 0.1 to 3.0 mm, such as iron, stainless steel, titanium, aluminum, zinc alloy-coated steel sheet, enameled steel sheet, clad steel sheet, laminated steel sheet (e.g., polyvinyl chloride-coated steel sheet), and sandwich steel sheet (e.g., seismic-response control steel sheet) (naturally, including colored metal sheets obtained by painting these sheets in tones of various colors). Furthermore, temporarily attaching, for example, sticking the reinforcement member 4 to the bearing face material 2 beforehand with an adhesive, a double-sided tape, or the like before fixing the reinforcement member 4 to the bearing face material 2 with the nails 3 makes handling further easier. The reinforcement member 4 formed of a thin steel sheet is not only effective in forming a bearing wall having excellent earthquake resistance once the bearing face material 2 has been fixed to the skeleton, but also facilitates conveyance and installation because the bearing face material 2 is not made bulky and also is not made very heavy, and improves the earthquake resistance of the bearing wall at a low cost.
In addition to the above-described thin steel sheets, any material that does not allow the nails to easily pass through, such as a glass fiber sheet, a carbon fiber sheet, or the like, can be used as the reinforcement member 4 in the same manner as the thin steel sheets. If the strength is the same, lighter reinforcement members provide better workability.
As the reinforcement member 4, when a reinforcement member formed by combining two each of long and short strip-like steel sheets as shown in
Furthermore, as shown in
Table 2 shows the wall strength factor of a base of a wall according to the present invention. Ordinary installation indicates an installation structure in which the reinforcement member 4 is not employed, and installation for achieving a high wall strength factor indicates an installation structure in which reinforcement member 4 is employed. The installation conditions are as follows: a pulp-silicate mixed cement board was used as the bearing face material 2, N50 nails were used as the nails 3, the size of the pillars 10 was set to at least 105 mm, and the bearing face material was installed on an ordinary wall portion provided with the studs 9. It should be noted that in the case of installation for achieving a high wall strength factor, a prepainted hot-dip 55% aluminum-zinc alloy-coated steel sheet specified in JIS G 3322:2008 having a thickness of 0.35 mm and a width of 30 mm was used as the reinforcement member 4.
In the case of installation for achieving a high wall strength factor, the wall strength factor was 7.8 kN/m, and a superior wall strength factor to the wall strength factor 6.5 kN/m in the case of ordinary installation was provided. The installation specifications of the above-described installation for achieving a high wall strength factor are applied to a wall that is required to have a high wall strength factor by a seismic design.
It should be understood that the foregoing description relates to only an embodiment of the installation structure of a base of an exterior wall according to the present invention, and the present invention is not limited to the description of the embodiment and various changes and variations may be made without departing from the gist of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| JP2011-067794 | Mar 2011 | JP | national |
