JP7828652B2 - Support posts for lighting fixtures and their design method - Google Patents

Description

This invention relates to a support column for lighting fixtures and a design method thereof. More specifically, it relates to a support column with a simple structure that possesses sufficient strength, and a design method thereof, primarily used for installing lighting fixtures in stadiums, soccer fields, and the like.

Lighting is essential in athletics stadiums, soccer fields, baseball fields, and similar venues. Since individual lighting fixtures are quite heavy, the support columns for them must also possess considerable strength. Typical lighting fixture support columns are specially shaped, with the entire column or joint sections constructed from tapered steel pipes. This requires specialized manufacturing equipment, and the limited number of manufacturers contributes to high costs and long lead times.

Generally, support poles for lighting fixtures exceed 15 meters in height. These poles fall under the category of structures (reinforced concrete columns, etc.) as defined in Article 88, Paragraph 1 of the Building Standards Act and Article 138, Paragraph 1, Item 2 of the Enforcement Order of the Building Standards Act (Cabinet Order), and are subject to the regulations. While these poles do not have a uniform diameter throughout their entire length, with the lower members being larger in diameter than the upper members, the aforementioned regulations stipulate that the misalignment of the welds at the joints (the difference between the reference planes of the base materials being welded) must be 5 mm or less.

While using a diaphragm to join square steel pipe columns is a common method, it is primarily used for joining H-beams to square steel pipe columns and is not a design method for joining square steel pipe columns vertically (e.g., Japanese Patent Publication No. 2023-23809). Furthermore, there are proposals for joint structures for steel columns of different diameters (e.g., Japanese Patent Publication No. 2000-8482), but these joint structures utilize a specially shaped column core equivalent to a diaphragm and are not common.

Japanese Patent Publication No. 2023-23809 Japanese Patent Publication No. 2000-8482

As mentioned above, conventional support posts for general lighting fixtures require specialized manufacturing equipment, and the limited number of manufacturers leads to high costs and long lead times. This invention addresses these problems in the prior art, aiming to provide a support post for lighting fixtures and its design method that possesses sufficient strength to support lighting fixture installation, can be manufactured relatively easily without the need for specialized manufacturing equipment, and meets the requirements of the aforementioned government ordinance.

The invention described in claim 1, which solves the above problem, is a method for designing a support column for installing a lighting fixture , which is manufactured by vertically welding together a plurality of steel pipe columns of different diameters via a through diaphragm , such that the lower columns have larger diameters.
The plate thickness of the through diaphragm is set such that the out-of-plane stress generated therein is less than or equal to the short-term allowable stress,
This is a design method for a support column for lighting fixtures , in which the out-of-plane stress generated in the aforementioned through diaphragm is confirmed to be less than or equal to the short-term allowable stress using the following formula (1) .
Here
iMy: Out-of-plane bending moment about the y-axis at point i (unit: Nmm)
jMz: Out-of-plane bending moment about the z-axis at point j (unit: Nmm)
iZy: Section modulus of the cross-section in the y-axis direction at point i (unit: ^mm³ )
jZz: Section modulus of the cross-section in the z-axis direction at point j (unit: ^mm³ )
iQz: Out-of-plane shear force in the Z-axis direction at point i (unit: N)
jQy: Out-of-plane shear force in the y-axis direction at point j (unit: N)
iAy: Cross-sectional area of the y-axis direction at point i (unit: ^mm² )
jAz: Cross-sectional area of the z-axis direction at point j (unit: ^mm² )
i: Any distance from the diaphragm center in the z-axis direction (compression side flange direction is considered positive) (unit: mm)
j: Any distance from the diaphragm center in the y-axis direction (absolute value) (unit: mm)
Y-axis: Direction perpendicular to the direction of maximum wind resistance for the lighting pole's light fixture.
z-axis: Direction of maximum wind resistance for the lighting pole's light fixtures
F: Allowable tensile stress of the diaphragm (unit: N/ ^mm² )

The lighting fixture support column and its design method according to the present invention are as described above. By joining the upper and lower steel pipe columns via a through diaphragm set to satisfy formula (1) above, it is possible to create a lighting fixture support column with sufficient strength to accommodate lighting fixtures without requiring a dedicated manufacturing device.

This is a perspective view showing the overall configuration of the support column for installing lighting fixtures according to the present invention. This is a perspective view showing the configuration of the through-diaphragm for a support column for lighting fixtures according to the present invention. This is a perspective view showing a method for lengthening a square steel pipe column in a support column for lighting fixtures according to the present invention. This figure shows a method for replacing the upper steel pipe in a support column for lighting fixtures according to the present invention. This is a diagram showing the classification of replacement plates. This is a diagram showing a modeled through-diaphragm. This diagram shows the stress generated in the modeled through-diaphragm. This figure shows the out-of-plane bending moment of a through diaphragm.

The embodiments for carrying out the present invention will be described in detail with reference to the attached drawings. The lighting fixture mounting support column according to the present invention is formed by vertically joining multiple steel pipe columns of different diameters, with the lower columns being of larger diameter. Each of the multiple steel pipe columns is welded together via a through-diaphragm. The thickness of the through-diaphragm is set such that the out-of-plane stress generated therein is below the short-term allowable stress, thereby allowing a maximum misalignment of 50 mm on one side between the upper and lower steel pipe columns. The reason for allowing a maximum misalignment of 50 mm on one side is that it was considered optimal in order to maintain the upper limit of the through-diaphragm's thickness (100 mm).

Figure 1 shows the overall configuration of the lighting fixture support column 1 according to the present invention. The uppermost of the multiple-tiered steel pipe columns is a circular steel pipe 4 equipped with a top plate 3 for mounting a lighting fixture 2 at its upper end, while the other three steel pipe columns are square steel pipes 5, 6, and 7. In the illustrated example, there are three tiers of square steel pipes 5, 6, and 7, but there may also be two or four or more tiers. In the illustrated example, the square steel pipe column 6 is formed by joining two steel pipe columns 6a and 6b of the same diameter on all four sides using a splice plate 11 and high-strength bolts (see Figure 3). This configuration is used when the support column is segmented for convenience during manufacturing and transportation, and then joined at the installation site.

The column cross-sections of each steel pipe column 4 to 7 are varied according to the distance from the top so that the effective slenderness ratio is 200 or less. A column base plate 8 is installed at the lower end of the lowest square steel pipe column 7. The column base plate 8 and the subsequent through diaphragm 10 are made of SN490C, or equivalent TMCP steel, which is the strongest material among the standardized building steel materials. One reason for using a square steel pipe column 7 at the bottom is that, since the foundation (column base plate 8) is generally rectangular, it makes it easier to align the columns with the direction of the foundation. The square steel pipes 5 and 6 above it are designed to match the square steel pipe column 7. Furthermore, because the angle of the lighting and the angle of the foundation may differ, the uppermost steel pipe to which the lighting fixture 2 is attached is a circular steel pipe 4.

The circular steel pipe 4 and the square steel pipe 5, as well as the connections between the square steel pipes 5, 6, and 7, are welded together via a through diaphragm 10. The welding is performed by full penetration welding. As described above, the lighting fixture support column 1 exceeds 15 m in height and is subject to the regulations of the Building Standards Act Enforcement Order. These regulations stipulate that the misalignment of the welds at the joints (the difference between the reference planes of the base materials being welded) must be 5 mm or less.

The lighting fixture mounting support column 1 according to the present invention changes its column cross-section according to the distance from the top so that the effective slenderness ratio is 200 or less. The part where the column cross-section changes is welded together via a through diaphragm 10, and the members joined to the upper and lower sides of the through diaphragm 10 allow for a maximum misalignment of 50 mm on one side. However, this allowable range of misalignment violates the above-mentioned government ordinance, so safety confirmation is required in accordance with the proviso stipulated in the notification of the above-mentioned government ordinance.

The inventors of this invention, through diligent research and development to comply with the above-mentioned government ordinance, have discovered that by adopting a design method that sets the plate thickness of the through-diaphragm 10 so that the out-of-plane stress generated in the through-diaphragm 10 is less than or equal to the short-term allowable stress, it is possible to comply with the proviso stipulated in the notification of the above-mentioned government ordinance, namely, "This shall not apply if appropriate reinforcement is carried out so that the load-bearing capacity of the part is greater than or equal to the load-bearing capacity of the part determined based on the respective allowable stresses for the long-term and short-term forces of the steel material at the joint." This discovery has led to the completion of the present invention.

The design method is described in detail below. In this invention, reinforcement for misalignment is performed by confirming that the through diaphragm 10 is within the short-term allowable stress limit for out-of-plane stress. This confirmation is performed using equation (1), described later, and the plate thickness at each point of the through diaphragm 10 is set to satisfy equation (1). The design procedure for the through diaphragm 10 is as follows.

1) The circular steel pipe 4 and the square steel pipe 5 are transformed into cross-sections using four identical plates with equivalent cross-sectional area and section modulus (see Figure 4).
To replace the rectangular steel pipe 5, we will find b (width of the four plates: mm) and uD (depth of the rectangle formed by the four plates: mm) that satisfy the following conditions.
To replace the circular steel pipe 4, we need to find ut ³ (thickness of 4 plates: mm), b (width of 4 plates: mm), and uD (depth of the rectangle formed by the 4 plates: mm) that satisfy the following conditions.

2) Two sets of plates, with their thickness parallel to the load direction, form the flange, and two sets of plates, with their width parallel, form the web (see Figure 5).

3) The through diaphragm 10 is positioned on a simply supported beam, pinned at the lower square steel pipe position, in the direction of the horizontal load and in the direction perpendicular to the horizontal load (see Figure 6).

4) For simply supported beams in the direction of the load, the stress is determined by considering the axial force acting on the flanges of the four plates with the upper member replaced as the external force. For simply supported beams perpendicular to the load, the stress is determined by considering the axial force acting on the webs of the four plates with the upper member replaced as the load. The stress due to the web is divided into compression and tension sides, and is considered to act on the compression side diaphragm and the tension side diaphragm, respectively, which have a width of half the effective width of the diaphragm (see Figure 7).

It is necessary to confirm that the combined stress of bending stress and shear stress in the horizontal load direction and the perpendicular direction is less than or equal to the short-term allowable stress of the through diaphragm 10. This confirmation can be performed using the following equation (1). The stress generated in the through diaphragm 10 must satisfy equation (1) at each point of the through diaphragm 10.

Here, iMy: Out-of-plane bending moment about the y-axis at point i (unit: Nmm)
jMz: Out-of-plane bending moment about the z-axis at point j (unit: Nmm)
iZy: Section modulus of the cross-section in the y-axis direction at point i (unit ^{: mm³} )
jZz: Section modulus of the cross-section in the z-axis direction at point j (unit ^{: mm³} )
iQz: Out-of-plane shear force in the Z-axis direction at point i (unit: N)
jQy: Out-of-plane shear force in the y-axis direction at point j (unit: N)
iAy: Cross-sectional area of the y-axis direction at point i (unit ^{: mm²} )
jAz: Cross-sectional area of the z-axis direction at point j (unit: ^mm² )
i: Any distance from the diaphragm center in the z-axis direction (compression side flange direction is considered positive) (unit: mm)
j: Any distance from the diaphragm center in the y-axis direction (absolute value) (unit: mm)
Y-axis: Direction perpendicular to the direction of maximum wind resistance for the light fixture on the lighting pole. Z-axis: Direction of maximum wind resistance for the light fixture on the lighting pole. F: Allowable tensile stress of the diaphragm (unit: N/ ^mm² )

The above iMy, jMz, iQz, and jQy can be calculated from the following formula.
Here, uL is the value obtained by subtracting the equivalent plate thickness ut' from the cross-sectional depth uD of a set of four identical plates arranged symmetrically on two axes for the upper members.
uL = ud - ut' (unit: mm)
LL: The value obtained by subtracting the plate thickness Lt from the depth LD of the lower square steel pipe. LL = LD - Lt (unit: mm)
NL: Column axial force at the height under consideration (unit: N)
Nf: Axial force acting on the upper member flange due to the bending moment around the y-axis at the height under consideration (unit: N)
Nw: Axial force acting on the upper member web due to the bending moment around the y-axis at the height under consideration (unit: N)

The above equation (1) confirms that the principal axis stress values, due to the bending moment iMy around the y-axis, the bending moment jMz around the z-axis, the shear force iQz in the z-axis direction, and the shear force jQy in the y-axis direction at any point (i, j) on the through diaphragm 10, do not exceed the allowable tensile stress of the diaphragm. This point has been evaluated using a structural performance evaluation (ERI-K22004) as part of the design method's assessment.

The lighting fixture support column and its design method according to the present invention are as described above. By joining the upper and lower steel pipe columns via a through diaphragm set to satisfy a predetermined formula, it is possible to create a lighting fixture support column with sufficient strength to accommodate lighting fixtures without requiring specialized manufacturing equipment, thus offering great industrial applicability.

1. Support pole for lighting fixtures 2. Lighting fixtures 3. Top plate 4. Circular steel pipe column 5, 6, 7. Square steel pipe column
8. Column base plate
10 Through diaphragm

Claims (1)

A method for designing a support column for installing a lighting fixture, which is manufactured by vertically welding together multiple steel pipe columns of different diameters via a through diaphragm, with the lower columns being of larger diameters.
The plate thickness of the through diaphragm is set such that the out-of-plane stress generated therein is less than or equal to the short-term allowable stress,
A design method for a support column for lighting fixtures , which confirms that the out-of-plane stress generated in the aforementioned through diaphragm is less than or equal to the short-term allowable stress using the following formula (1) .
Here
iMy: Out-of-plane bending moment about the y-axis at point i (unit: Nmm)
jMz: Out-of-plane bending moment about the z-axis at point j (unit: Nmm)
iZy: Section modulus of the cross-section in the y-axis direction at point i (unit: ^mm³ )
jZz: Section modulus of the cross-section in the z-axis direction at point j (unit: ^mm³ )
iQz: Out-of-plane shear force in the Z-axis direction at point i (unit: N)
jQy: Out-of-plane shear force in the y-axis direction at point j (unit: N)
iAy: Cross-sectional area of the y-axis direction at point i (unit: ^mm² )
jAz: Cross-sectional area of the z-axis direction at point j (unit: ^mm² )
i: Any distance from the diaphragm center in the z-axis direction (compression side flange direction is considered positive) (unit: mm)
j: Any distance from the diaphragm center in the y-axis direction (absolute value) (unit: mm)
Y-axis: Direction perpendicular to the direction of maximum wind resistance for the lighting pole's light fixture.
z-axis: Direction of maximum wind resistance for the lighting pole's light fixtures
F: Allowable tensile stress of the diaphragm (unit: N/ ^mm² )