Design method for reinforcing structures for rectangular steel pipe columns

Abstract

To provide an easy design method for a square steel pipe column reinforcement structure that can appropriately improve deformability, and a square steel pipe column reinforcement structure.SOLUTION: A design method for a square steel pipe column reinforcement structure of this invention comprises: a third step to calculate an inclusive-type elastic local buckling yield strength and a non-inclusive-type elastic local buckling yield strength respectively based on values of parameters temporarily set by a second step; and a fourth step to compare the inclusive-type elastic local buckling yield strength and the non-inclusive-type elastic local buckling yield strength to select one of the deformation states. It is possible to select one deformation state that has high chance to occur between the inclusive type and the non-inclusive type in the condition with the values of the temporarily-set parameters. The design method comprises a fifth step to calculate the performance of the square steel pipe column reinforcement structure based on the elastic local buckling yield strength of one of the deformation states, and a sixth step to finalize parameters according to the temporarily-set values in the case the computed performance satisfies the required performance. Parameters satisfying the required performance with the selected deformation state can be easily determined.SELECTED DRAWING: Figure 16

Description

[Technical Field]

[0001] This invention relates to a design method for a square steel pipe column reinforcement structure, and to a square steel pipe column reinforcement structure. [Background technology]

[0002] The seismic performance of a building is evaluated based on the load-bearing capacity and deformation performance of its constituent members. In the case of rectangular steel pipe columns, if the width-to-thickness ratio (outer diameter / plate thickness) is large, local buckling occurs at the end of the column when subjected to external forces, leading to a premature loss of load-bearing capacity and poor deformation performance, which is a problem. In response to this, architectural design verifies safety by increasing the design external force according to the width-to-thickness ratio of the rectangular steel pipe column. On the other hand, in order to improve the seismic performance of rectangular steel pipe columns, construction methods have been proposed to improve the load-bearing capacity or deformation performance of the column, and many of these cases aim to improve load-bearing capacity.

[0003] In this context, reinforcing structures are sometimes employed that involve placing reinforcing materials at the ends of square steel pipe columns in order to improve their load-bearing capacity or deformation performance. For example, rib plate reinforcement and cover plate reinforcement methods may be used as reinforcement methods intended to improve the load-bearing capacity of square steel pipe columns. For instance, the latter method is summarized as a means of seismic retrofitting for existing buildings in the "(General Incorporated Foundation) Japan Building Center; 2018 Edition Cold Formed Square Steel Pipe Design and Construction Manual Supplement "STKR Column Reinforcement Design and Construction Manual"".

[0004] Furthermore, a reinforcement method intended to improve the deformation performance of square steel pipe columns is known, as described in Patent Document 1. Patent Document 1 describes a structure that aims to improve the deformation performance of a square steel pipe column by placing reinforcing material through a gap from at least one side of the outer or inner surface of the end of the square steel pipe column, so that the reinforcing material comes into contact with the square steel pipe column when it undergoes local buckling deformation and can restrict the local buckling deformation. Alternatively, as a repair method intended to restore the load-bearing capacity of a damaged square steel pipe column, the "(General Incorporated Foundation) Japan Building Disaster Prevention Association; Criteria for Classifying the Degree of Damage to Earthquake-Damaged Buildings, etc. and Guidelines for Restoration Technology (2015)" describes a method in which a cover plate is applied from the outside to the area where local buckling deformation has occurred in a square steel pipe column damaged by an earthquake and welded, thereby restoring the load-bearing capacity to the same level as the original steel pipe. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2012-136929 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Here, square steel pipe columns with a large width-to-thickness ratio have the problem of poor deformation performance because they lose their load-bearing capacity early when subjected to external forces. Furthermore, conventional reinforcement methods for square steel pipe columns are often aimed at improving load-bearing capacity, and excessive increases in load-bearing capacity can raise concerns about the impact on the design of surrounding members. Therefore, there has been a need for a simple design method that appropriately improves deformation performance without excessively increasing load-bearing capacity.

[0007] This invention was made to solve these problems, and aims to provide a design method for a square steel pipe column reinforcement structure and a square steel pipe column reinforcement structure that can appropriately improve deformation performance with an easy design method. [Means for solving the problem]

[0008] The present invention relates to a design method for a square steel pipe column reinforcement structure, comprising a square steel pipe column and a plate-shaped reinforcing member provided at a position spaced apart from the longitudinal end face of the square steel pipe column, on at least one of the outer and inner surfaces of the side wall portion of the square steel pipe column, comprising: a first step of setting the required performance of the square steel pipe column reinforcement structure; a second step of provisionally setting parameters related to the reinforcing member; a third step of calculating the elastic local buckling strength of the winding type and the elastic local buckling strength of the non-winding type, respectively, based on the values ​​of the parameters provisionally set in the second step; a fourth step of comparing the elastic local buckling strength of the winding type and the elastic local buckling strength of the non-winding type and selecting one of the deformation modes; a fifth step of calculating the performance of the square steel pipe column reinforcement structure based on the elastic local buckling strength of the one deformation mode; and a sixth step of determining the parameters using the provisionally set values ​​if the calculated performance satisfies the required performance.

[0009] The design method for this square steel pipe column reinforcement structure comprises a third step of calculating the elastic local buckling strength of the wrapped type and the elastic local buckling strength of the non-wrapped type, respectively, based on the parameter values ​​provisionally set in the second step, and a fourth step of comparing the elastic local buckling strength of the wrapped type and the elastic local buckling strength of the non-wrapped type and selecting one of the deformation modes. This makes it possible to select the deformation mode that is more likely to occur with the provisionally set parameter values, between the wrapped type and the non-wrapped type. Furthermore, the design method for the square steel pipe column reinforcement structure comprises a fifth step of calculating the performance of the square steel pipe column reinforcement structure based on the elastic local buckling strength of one of the deformation modes, and a sixth step of determining the parameters with the provisionally set values ​​if the calculated performance meets the required performance. In this case, the parameters that satisfy the required performance with the selected deformation mode can be easily determined. Thus, deformation performance can be appropriately improved with a simple design method.

[0010] In the fifth step, the standardized width-to-thickness ratio of one deformation mode may be calculated based on the elastic local buckling strength of one deformation mode, and the plastic deformation ratio corresponding to the standardized width-to-thickness ratio may be calculated. In this case, the performance of the square steel pipe column reinforcement structure can be easily calculated by using the standardized width-to-thickness ratio and the plastic deformation ratio.

[0011] The standardized width-thickness ratio of one deformation mode may be calculated based on the relationship between the standardized width-thickness ratio and the elastic local buckling bearing capacity. In this case, the standardized width-thickness ratio of one deformation mode can be easily calculated by basing on a predetermined relationship.

[0012] Specifically, the aforementioned relationship between the standardized width-thickness ratio and the elastic local buckling bearing capacity of the reinforced square steel pipe column defines the standardized width-thickness ratio as S HR , the yield point of the unreinforced square steel pipe column as σ y , the plastic section modulus of the unreinforced square steel pipe column as Z p , the elastic local buckling bearing capacity of the reinforced square steel pipe column as P cr , and the length of the square steel pipe column as 2L, then it may be expressed by Formula (12).

Formula

[0013] The plastic deformation magnification of one deformation mode may be calculated based on the relationship between the plastic deformation magnification of one deformation mode and the standardized width-thickness ratio of one deformation mode. In this case, the plastic deformation magnification of one deformation mode can be easily calculated by basing on a predetermined relationship.

[0014] Specifically, for the relationship between the non-wrapping type plastic deformation magnification and the wrapping type standardized width-thickness ratio, when the non-wrapping type plastic deformation magnification is defined as n η 90% , and the standardized width-thickness ratio of the non-wrapping type square steel pipe column is defined as n S HR , it is expressed by Formula (13); and for the relationship between the wrapping type plastic deformation magnification and the wrapping type standardized width-thickness ratio, when the wrapping type plastic deformation magnification is defined as c η 90% , and the standardized width-thickness ratio of the wrapping type square steel pipe column is defined as c S HR , it may be expressed by Formula (14).

Formula

[0015] In the second step, the thickness of the reinforcing plate, the width of the reinforcing plate, and the length of the reinforcing plate may be provisionally set as parameters. In this case, the elastic local buckling strength can be easily calculated from the provisionally set parameters.

[0016] In the third step, the elastic local buckling resistance of the wrapped type may be calculated based on the relationship between the parameters and the elastic local buckling resistance of the wrapped type, and the elastic local buckling resistance of the non-wrapped type may be calculated based on the relationship between the parameters and the elastic local buckling resistance of the non-wrapped type. In this case, the elastic local buckling resistance of both the wrapped and non-wrapped types can be easily calculated based on predetermined relationships.

[0017] Specifically, the relationship between the parameters and the non-entrapment type elastic local buckling resistance is as follows: n P cr Let D be the diameter of the rectangular steel pipe column, 2L be the length of the rectangular steel pipe column, t be the plate thickness of the rectangular steel pipe column, E be the Young's modulus of the rectangular steel pipe column, ν be the Poisson's ratio of the rectangular steel pipe column, Z be the section modulus of the rectangular steel pipe column, and t be the plate thickness of the reinforcing material. r The reinforcement length from the end face to the end of the reinforcing material is set to h r The width of the reinforcing material is set to b r In this case, the relationship between the parameter and the elastic local buckling strength of the wrap-around type is given by equation (10), and the elastic local buckling strength of the wrap-around type is given by c P cr Let D be the diameter of the square steel pipe column, 2L be the length of the square steel pipe column, t be the plate thickness of the square steel pipe column, E be the Young's modulus of the square steel pipe column, ν be the Poisson's ratio of the square steel pipe column, and t be the plate thickness of the reinforcing material. r The width of the reinforcing material is set to b r Assuming that the cross-sectional area of ​​the reinforcing material is evenly distributed around the outer circumference of the square steel pipe column, the increased thickness of the square steel pipe column is t r If we assume that the section modulus of the assumed rectangular steel pipe column is Z', then it can be expressed by equation (11).

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[0018] In the sixth step, if the calculated performance does not meet the required performance, the process may return to the second step and tentatively set the parameters with other values. This allows for the parameter to be tentatively set again to meet the required performance.

[0019] The square steel pipe column reinforcement structure according to this embodiment is manufactured using the design method for the square steel pipe column reinforcement structure described above. This square steel pipe column reinforcement structure provides the same functions and effects as the design method for the square steel pipe column reinforcement structure described above. [Effects of the Invention]

[0020] According to the present invention, deformation performance can be appropriately improved with a simple design method. [Brief explanation of the drawing]

[0021] [Figure 1] This is a perspective view showing a column-beam joint structure to which the design method for a rectangular steel pipe column reinforcement structure according to an embodiment of the present invention is employed. [Figure 2] This is a diagram showing the entire rectangular steel pipe column. [Figure 3] This diagram shows a reinforced structure for square steel pipe columns. [Figure 4] This is a diagram showing the test specimen. [Figure 5] This is a table showing a list of test specifications and test results. [Figure 6] This is a graph showing the test results. [Figure 7] This is a diagram illustrating the overview of the nonlinear analysis model. [Figure 8] This is a diagram showing the types of deformation patterns. [Figure 9] This graph shows the relationship between the thickness of the reinforcing material and its deformation performance (plastic deformation ratio). [Figure 10] This graph shows the relationship between the thickness of the reinforcing material and its deformation performance (plastic deformation ratio). [Figure 11] This model shows an unreinforced rectangular steel pipe column. [Figure 12]This diagram illustrates how to replace the local buckling phenomena of both non-wound and wound types with unreinforced square steel pipe columns. [Figure 13] This figure shows a model in which a square steel pipe column reinforced with reinforcing material is replaced with an unreinforced square steel pipe column. [Figure 14] This graph shows the ratio of analytical solutions to assumed solutions for the elastic local buckling strength corresponding to non-wound and wound elastic buckling modes of reinforced square steel pipe columns, and the correspondence with the approximation formulas. [Figure 15] This graph shows the evaluation of the deformation performance of reinforced square steel pipe columns using the standardized width-to-thickness ratio for both non-wrapped and wrapped types. [Figure 16] This is a flowchart illustrating the design method for a rectangular steel pipe reinforced structure. [Figure 17] This is a flowchart illustrating the design method for a rectangular steel pipe reinforced structure. [Figure 18] This figure shows the reinforcing material for a modified rectangular steel pipe column reinforcement structure. [Modes for carrying out the invention]

[0022] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[0023] Figure 1 is a perspective view showing a column-beam joint structure 50 employing a square steel pipe column reinforcement structure 100 according to an embodiment of the present invention. Figure 2 is a diagram showing the entire square steel pipe column 1. As shown in Figures 1 and 2, the column-beam joint structure 50 comprises a square steel pipe column 1, a beam 2 joined to the square steel pipe column 1, and a joint core 3. Note that Figures 1 and 2 merely show an example of an application for the square steel pipe column reinforcement structure, and the application can be changed as appropriate.

[0024] The rectangular steel pipe column 1 is constructed from a steel pipe having a rectangular cross-section. The upper rectangular steel pipe column 1 and the lower rectangular steel pipe column 1 are connected to each other in the vertical direction via a connecting core 3. The rectangular steel pipe column 1 has four side walls 10. The rectangular steel pipe column 1 has a lower end face 1a and an upper end face 1b in the longitudinal direction (vertical direction).

[0025] The four beams 2 are joined to the square steel pipe columns 1 via connecting cores 3. The beams 2 have an H-shaped cross-section and consist of upper and lower flanges 2a and 2b, and a web portion 2c that connects the flanges 2a and 2b.

[0026] The connecting core 3 comprises a steel pipe section 3a having a rectangular cross-section, and diaphragms 3b and 3c formed on the upper and lower end faces of the steel pipe section 3a. The lower end face 1a of the upper rectangular steel pipe column 1 is joined to the diaphragm 3b of the connecting core 3. The upper end face 1b of the lower rectangular steel pipe column 1 is connected to the diaphragm 3c of the connecting core 3. In addition, the upper and lower flanges 2a and 2b of the beam 2 are also joined at the positions of the upper and lower diaphragms 3b and 3c.

[0027] The square steel pipe column reinforcement structure 100 comprises the square steel pipe column 1 described above and a plurality of reinforcing members 20. The reinforcing members 20 are rectangular plate-shaped members provided on at least one of the outer and inner surfaces of the side wall portion 10 of the square steel pipe column 1, at positions spaced apart from the end faces 1a and 1b of the square steel pipe column 1. In this embodiment, the reinforcing members 20 are formed in a rectangular shape and are fixed to the outer surface of the side wall portion 10. The reinforcing members 20 are provided on all four side wall portions 10 near the lower end face 1a of the square steel pipe column 1. The reinforcing members 20 are provided on all four side wall portions 10 near the upper end face 1b of the square steel pipe column 1. Therefore, a total of eight reinforcing members 20 are provided for one square steel pipe column 1.

[0028] Next, with reference to Figure 3, the dimensional relationship of the square steel pipe column reinforcement structure 100 will be explained. Note that Figure 3 shows the lower configuration of the square steel pipe column 1, but the upper configuration is similar. As shown in Figure 3(a), the diameter of the square steel pipe column 1 is D. The plate thickness of the square steel pipe column 1 is t. As shown in Figure 3(b), the reinforcement length from the lower end face 1a of the square steel pipe column 1 to the end 20a of the reinforcing material 20 that is spaced apart from the end face 1a is h. r The gap from the lower end face 1a of the square steel pipe column 1 to the end 20b of the reinforcing member 20 that is closer to the end face 1a is defined as S. rThe ends 20a and 20b are parallel to the end face 1a of the square steel pipe column 1. The width of the reinforcing member 20 is b. r The reinforcing member 20 is positioned in the center of the side wall portion 10 in the width direction. The ends 20c and 20d of the reinforcing member 20 in the width direction are parallel to the ends 10a and 10b of the side wall portion 10, at positions spaced inward in the width direction from the ends 10a and 10b. The plate thickness of the reinforcing member 20 is t r The length of the square steel pipe column 1 is set to 2L. Specifically, for "diameter D × plate thickness t of the square steel pipe column", the range may be "□200 × 6 to □550 × 19" for cold roll-formed square steel pipes, and "□350 × 12 to □1000 × 32" for cold press-formed square steel pipes. The gap is "0 ≤ S". r The value / D≦0.27 may be used. The material of the reinforcing material 20 shall be steel, and its strength class shall be equivalent to or within one rank above or below the square steel pipe column 1.

[0029] Next, we will explain the preferred dimensional relationships for each part of the square steel pipe column reinforcement structure 100. First, referring to Figures 4 to 6, we will explain the test for the load-bearing capacity of the square steel pipe column reinforcement structure 100. Specifically, in order to confirm the reinforcement effect of the square steel pipe column reinforcement structure 100, the plate thickness t of the reinforcing material 20 r , reinforcement length h r A full-scale three-point bending test (monotonic / cyclic loading) was conducted using as the variable. The specimens shown in Figure 4(a) were prepared. An enlarged view of the part indicated by "A" in the figure is shown in Figure 4(b). Two specimens were prepared, each with reinforcing members 20 attached to all four sides of a rectangular steel pipe column 1. The end of each rectangular steel pipe column 1 on the side with the reinforcing member 20 was supported by a support member 32. The opposite ends of each rectangular steel pipe column 1 were supported by support members 31. A load was applied to the central support member 32, and measurements were taken to observe the characteristics of local buckling. A specimen for "unreinforced" (without reinforcing members 20) was also prepared.

[0030] The tests were conducted under two conditions: "monotonically applied load" and "repeatedly applied load." Figure 5 shows a summary of the test specifications and test results. Figure 6(a) shows the test results for the load-deformation relationship under monotonically applied load, and Figure 6(b) shows the test results for the load-deformation relationship under repeated loading. From Figure 5, it was confirmed that the maximum load-bearing capacity with reinforcement was equal to or greater than that of the unreinforced column, and that the load-bearing capacity was equal to or greater than that of the original square steel pipe column. Furthermore, "reinforcement 2.3 × 360" showed the highest reinforcement effect, and the deformation performance was 1.36 times the plastic deformation ratio under monotonically applied load and 1.60 times the cumulative plastic deformation ratio under repeated loading compared to the unreinforced column. In the cases in which the tests were conducted, local buckling of the wrapping type occurred in the two test specimens with the longest reinforcement length of 360 mm, and local buckling of the non-wrapping type occurred in the test specimen with the shortest reinforcement length of 240 mm, confirming that wrapping type buckling is more effective in improving deformation performance. The term "wrapped type" refers to a deformation mode in which the local buckling deformation of a rectangular steel pipe column is restrained by the reinforcing material as the deformation progresses (see, for example, Figure 8(b)). The term "non-wrapped type" refers to a deformation mode in which the reinforcing length h is the distance from the end face of the rectangular steel pipe column joined to the diaphragm to the end of the reinforcing material. r This refers to a deformation pattern in which local buckling occurs, where the peak of buckling appears in the unreinforced section beyond a certain point, and the deformation continues in that manner (see, for example, Figure 8(a)). The gap type described later refers to the gap S from the end face of the square steel pipe column joined to the diaphragm to the end of the reinforcing material on the side closest to that end face. r This refers to a type of deformation in which local buckling occurs, where the peak of buckling appears internally, and the deformation continues in that state (see, for example, Figure 8(c)).

[0031] The nonlinear analysis will be explained with reference to Figures 2, 3, and 7-9. Here, the mechanical behavior of a rectangular steel pipe column 1 of length 2L subjected to double curvature bending as shown in Figure 2 can be roughly predicted by a cantilever column model in which one end is fixed and the other end is free, and a lateral load is applied to the free end of the rectangular steel pipe column 1 of length L, as shown in Figure 7. Therefore, the analysis was examined using the cantilever column model shown in Figure 7. <Analysis overview> (1) Square steel pipe column: width-to-thickness ratio D / t = 33.3, shear span ratio L / D = 5 (2) Reinforcement material: Rectangular plate • Reinforcement plate thickness ratio t r / t=0.13, 0.26, 0.36, 0.50, 0.67 (Example: Square steel pipe □300×9, t r If / t=0.50, t r (=4.5mm) • Reinforcement length ratio h r / D=0.4, 0.6, 0.8, 1.0, 1.2, 2.2 (Example: Square steel pipe □300×9, h r If / D=0.60, h r (=240mm) ·Reinforcement width ratio b r / D=0.2, 0.5, 0.8 • Gap ratio s r / D=0.2 is fixed (3) Material properties: Determined based on the tensile test results of the materials used in the structural test.

[0032] The results of the nonlinear analysis revealed three types of local buckling behavior, as shown in Figure 8. These deformation patterns are similar to those described in the structural tests mentioned earlier. Figure 9 is a graph showing the relationship between the plate thickness of the reinforcing material 20 and the deformation performance (plastic deformation ratio). The effect of improving deformation performance varies greatly depending on the reinforcement specifications, and it can be confirmed that this is related to the local buckling behavior. Furthermore, in order to efficiently improve deformation performance while suppressing the increase in the amount of steel material due to reinforcement, it is desirable to be able to select a reinforcement specification that satisfies the required performance of the square steel pipe column 1 from the viewpoint of material availability, cost, and constructability. However, since the combinations of square steel pipes and reinforcement specifications are enormous and mutually affecting, it is necessary to determine which local buckling behavior occurs and what degree of deformation performance is achieved only after conducting structural experiments and nonlinear analyses.

[0033] Next, we will examine the relationship between the elastic buckling mode of the reinforced square steel pipe column and the local buckling behavior observed in structural experiments and nonlinear analyses. To analyze the local buckling behavior, a linear buckling analysis of the reinforced square steel pipe column 1 itself was performed as follows. The material properties were defined as "Young's modulus: 205000 N / mm²". 2 Except for setting Poisson's ratio to 0.3, the conditions for the square steel pipe column 1 and reinforcing member 20 were the same as those for the nonlinear analysis in Figure 7 above.

[0034] Linear buckling analysis of this reinforced structure revealed elastic buckling modes with characteristics similar to the non-enveloping / enveloping local buckling behavior observed in structural tests and nonlinear analyses. However, it was not always the case that only one type of elastic buckling mode would appear for a given reinforcement specification; for example, some lower-order modes might exhibit non-enveloping characteristics, while others exhibit enveloping characteristics, resulting in the appearance of both types.

[0035] Figure 10 is the graph from Figure 9 showing the relationship between the plate thickness of the reinforcing material 20 and its deformation performance (plastic deformation ratio), with the gap-type results removed. Figure 10 shows the correspondence between the elastic buckling mode that gives the minimum elastic local buckling strength and the local buckling behavior in structural testing and nonlinear analysis. In Figure 10, the filled symbols indicate cases where the elastic buckling mode that gives the minimum elastic local buckling strength obtained in linear buckling analysis differs from the local buckling behavior in structural testing and nonlinear analysis. Among the non-wrapping type or elastic buckling modes with similar characteristics to the wrapping type in a certain reinforcement specification, it was confirmed that the elastic buckling mode that gives the minimum elastic local buckling strength and the local buckling behavior in structural testing and nonlinear analysis generally correspond.

[0036] Therefore, the local buckling behavior in a given reinforcement specification can be determined by whether the elastic buckling mode corresponding to the minimum elastic local buckling strength obtained by linear buckling analysis is non-wound type or wound type. Next, we examined the relationship between the variables related to the square steel pipe column and reinforcement specification and the elastic local buckling strength.

[0037] This paper examines the relationship between the elastic local buckling resistance of a reinforced square steel pipe column 1 and the determination of local buckling. Conventionally, the elastic local buckling resistance of an unreinforced square steel pipe column, considering the load conditions, has been theoretically derived, and an approximate formula (equation (3) below) is known. This approximate formula is described, for example, in "Kousuke Sato, Kikuo Igarashi: Calculation of coupled local buckling resistance of a square hollow section member subjected to biaxial bending shear force and axial force; Journal of Structural Engineering, Architectural Institute of Japan, Vol.79, pp.1909-1918, 2014.12 (Non-patent Literature 1)" and "Kousuke Sato, Kikuo Igarashi: Local buckling behavior and structural performance evaluation method of a square hollow section member subjected to bending shear force; Journal of Structural Engineering, Architectural Institute of Japan, Vol.82, pp.123-133, 2017.1 (Non-patent Literature 2)". This approximate formula is only applicable to unreinforced square steel pipe columns 1 as shown in Figure 11, and therefore cannot be directly applied to this reinforced structure. cr The variables are: ∫: Elastic local buckling moment, L: Length of the material, Z: Section modulus, E: Young's modulus, ν: Poisson's ratio, D: Diameter of the rectangular steel pipe, and t: Thickness of the rectangular steel pipe plate. The elastic local buckling moment is the elastic local buckling moment of the rectangular steel pipe column 1 under the load and boundary conditions shown in Figure 11.

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[0038] Based on the results of the linear buckling analysis described above, it is possible that both non-wrapping and wrapping elastic buckling modes can be obtained for a single reinforcement specification in this reinforcement structure. Therefore, we first investigated the relationship between the elastic local buckling strength corresponding to each elastic buckling mode and the square steel pipe column 1 and the reinforcement specification using the following procedure.

[0039] (Procedure 1) First, replace the column with an unreinforced square steel pipe column 1 so that the local buckling phenomena of both the non-wound type and the wound type can be observed. Figure 12 shows a conceptual diagram of this replacement. For the non-wound type, the reinforcement length h is exactly from the fixed end. r Assuming that the dangerous section is located at a distance of h from the original square steel pipe column, r Let's assume that we replace it with an unreinforced square steel pipe column with a shorter length (Figure 13, "P cr1(See "). The wrap-around type assumes that the end with the maximum bending moment is the critical section, and distributes the total cross-sectional area of ​​the reinforcing material 20 evenly around the outer circumference of the square steel pipe column 1. r Let's assume that it is replaced with an unreinforced square steel pipe column that has been thickened by only that much (Figure 13, "P cr2 "reference). (Step 2) Apply equations (4) and (5) to each of the above-mentioned unreinforced square steel pipe columns that were replaced, and calculate the assumed solution P for the elastic local buckling resistance of the non-wrapped / wrapped type. cr1 , P cr2 We will find this. Equation (4) is a rewrite of equation (3) using i. In this case, the quantities used in the calculation are those shown in Figure 13.

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[0040] Note that "P cri : Assumed solution for elastic local buckling resistance, "M cri : Elastic local buckling moment, L i : Length", "Z i : Section modulus, E: Young's modulus, ν: Poisson's ratio, D i : Diameter of square steel pipe column, t i : Plate thickness of square steel pipe column, "t r ': This is the increased plate thickness assuming that the cross-sectional area of ​​the reinforcing material is evenly distributed around the outer circumference of the square steel pipe column. The letters with the subscript i are the assumed solutions P for the elastic local buckling resistance of non-wrapping type / wrapping type. cr1 , P cr2 The values ​​in Figure 13 correspond to each of these, and are used.

[0041] Note that the increased plate thickness t r ' is the diameter D of the original square steel pipe column, and the thickness t of the reinforcing plate. r , reinforcement width b r It can be calculated from the following. Specifically, if a square steel pipe has a radius of curvature at the corner, and the radius of curvature on the outside of the corner is R, then the increased plate thickness t can be calculated by formula (6). r ' can be calculated. If there is no radius of curvature at the corner of the square steel pipe, the increased plate thickness t can be calculated by formula (7). r It is possible to calculate '.

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[0042] (Step 3) The assumed solution P of the elastic local buckling resistance derived in the above procedure. cr1 (Non-entrainment type), and assumed solution P cr2 The correspondence between the (wrap-around type) and the analytical solution derived from the linear buckling analysis of the reinforced square steel pipe column itself (the elastic local buckling resistance derived in paragraphs 0032 to 0034) is confirmed, and the analytical solution is expressed by increasing the assumed solution from (procedure 2) by a correction value. This correction value is derived by performing a regression analysis on the ratio of the assumed solution to the analytical solution.

[0043] Following the procedure described above, the analytical solution for the elastic local buckling strength corresponding to the non-wound / wound elastic buckling modes of the reinforced square steel pipe column, and the assumed solution P for the elastic local buckling strength are obtained. cr1 (non-involving type), assumed solution P cr2 The ratio of the (wound type) was evaluated using an approximate formula as shown in Figure 14. Analytical solution of the elastic local buckling resistance of the non-wound type. n P cr And the assumed solution P cr1 The relationship between this and the approximation formula is given by equation (8). Analytical solution of the elastic local buckling resistance of the encircling type c P cr And the assumed solution P cr2 The relationship between and the approximation formula is given by equation (9). Assumed solution P cr1 (non-involving type), assumed solution P cr2 To express the (wrap-around type) in more detail, equations (8) and (9) become equations (10) and (11), respectively. "Z'" is the section modulus of the square steel pipe column, assuming that the cross-sectional area of ​​the reinforcing material is evenly distributed around the outer circumference of the square steel pipe column.

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[0044] Next, we will explain the relationship between deformation performance and reinforcement specifications. Following Non-Patent Document 2, we will describe the deformation performance (plastic deformation ratio η) of the reinforced square steel pipe column 1. 90% ) the standardized width-to-thickness ratio S for both non-wrapped and wrapped types. HRUsing Equation (12), evaluations were performed with Equation (13) and Equation (14) (Figure 15). Here, in the evaluation of Equation (13) and Equation (14), the elastic local buckling strength of the non-wraparound type (Equation (10)) / wraparound type (Equation (11)) determined by the reinforcement specification n P cr / c P cr , the smaller one of which is substituted for P in Equation (12) cr to obtain the normalized width-thickness ratio S HR ( n expressed as S if P cr is smaller n , and S HR c expressed as S if P cr is smaller) c was determined, and regression analysis was carried out. HR [Formula]

[0045] Regarding Equation (12), "σ y : Yield point of unreinforced square steel pipe column", "Z p : Plastic section modulus of unreinforced square steel pipe column", "P cr : Elastic local buckling strength of reinforced square steel pipe column", and "L: Member length". Regarding Equation (13) and (14), "η 90% : Plastic deformation magnification (value obtained by normalizing the absorbed energy until reaching 0.9M after the maximum bending moment M is reached in the monotonic loading M-θ relationship) max max with M p ·θ p ", "M p : Full plastic moment of unreinforced square steel pipe column", "θ p : Value obtained by dividing M p by the initial elastic stiffness", and "S HR : Normalized width-thickness ratio of reinforced square steel pipe column" are defined.

[0046] From the above examinations, the descriptions of (i) and (ii) hold true for the present reinforcement structure. (i) For the square steel pipe column 1 with diameter D, plate thickness t, member length 2L, section modulus Z, yield point σ y , Young's modulus E, and Poisson's ratio ν, the reinforcing material plate thickness t​​​r , reinforcement width b r , reinforcement length h r , gaps r When reinforcing with, "t r >0, 0 r ≤0.8D, s r <h r ≤ L, s r Assuming "<0.27D", the required performance of the square steel pipe column 1 d The reinforcing plate thickness t is determined in the flow chart of Figure 16 to satisfy η. r , reinforcement width b r , reinforcement length h r It is possible to determine this. (ii) If aiming for a wrap-around type, the reinforcing plate thickness t can be calculated backward using the flow in Figure 17. r , reinforcement width b r , reinforcement length h r It is possible to determine this.

[0047] Regarding (i), we will now explain the details of the flow shown in Figure 16. As shown in Figure 16, first, the required performance d Set η (step S10). Note that the timing of executing step S10 is not particularly limited and can be performed at any time before steps S70 and S110 described later. Next, set the reinforcing plate thickness t. r , reinforcement width b r , reinforcement length h r The parameters of the reinforcing material 20 are provisionally set (step S20). At this time, the designer may provisionally set each parameter of the reinforcing material 20 as they see fit. Next, the reinforcing material plate thickness t that was provisionally set in step S20 is set. r , reinforcement width b r , reinforcement length h r By substituting this into equations (10) and (11), the elastic local buckling resistance of non-wound type / wound type can be obtained. n P cr , c P cr Calculate each of these (step S30). Next, the elastic local buckling strength calculated in step S30 n P cr and elastic local buckling resistance c P cr The relative sizes of the two are compared, and one of the deformation modes is selected (step S40). ​

[0048] In step S40, n P cr < c P cr When the relationship '' holds true, the non-wrapping type is selected as the deformation mode, and the elastic local buckling resistance of the non-wrapping type n P cr Using the normalized width-to-thickness ratio n S HR Calculate (step S50). In step S50, the right-hand side of equation (12) is "P cr "Step S30 non-wound elastic local buckling resistance n P cr Substitute the following. Next, the plastic deformation ratio n η 90% Calculate the normalized width-to-thickness ratio calculated in step S50 (step S60). In step S60, the normalized width-to-thickness ratio calculated in step S50 is calculated. n S HR The right side of equation (13) n S HR Substitute this into the equation. Next, the plastic deformation ratio calculated in step S60 n η 90% However, the required performance set in step S10 d It is determined whether the requirement of η or greater is met (step S70). If it is determined in step S70 that the requirement is met, the reinforcing plate thickness t, which was provisionally set in step S20, is determined. r , reinforcement width b r , reinforcement length h r The determination is made in step S80. On the other hand, if it is determined in step S70 that the requirements are not met, the process returns to step S20, and the reinforcing plate thickness t is determined by other values. r , reinforcement width b r , reinforcement length h r Set this as a temporary value.

[0049] In step S40, n P cr ≧ c P cr When the relationship '' holds true, the wrapping type is selected as the deformation mode, and the elastic local buckling resistance of the wrapping type c P cr Using the normalized width-to-thickness ratio c S HRCalculate (step S90). In step S90, the right-hand side of equation (12) is "P cr "Step S30 wrap-around elastic local buckling resistance c P cr Substitute the following. Next, the plastic deformation ratio c η 90% The normalized width-to-thickness ratio calculated in step S90 is calculated (step S100). In step S100, the normalized width-to-thickness ratio calculated in step S90 is calculated. c S HR The right-hand side of equation (14) is "S HR Substitute this into the equation. Next, the plastic deformation ratio calculated in step S100 c η 90% However, the required performance set in step S10 d It is determined whether the requirement of η or greater is met (step S110). If it is determined in step S110 that the requirement is met, the reinforcing plate thickness t, which was provisionally set in step S20, is determined. r , reinforcement width b r , reinforcement length h r The determination is made in step S80. On the other hand, if it is determined in step S110 that the requirements are not met, the process returns to step S20, and the reinforcing plate thickness t is determined by other values. r , reinforcement width b r , reinforcement length h r Set this as a temporary value.

[0050] If the process returns to step S20 in steps S70 and S110, the newly provisionally set reinforcing plate thickness t r , reinforcement width b r , reinforcement length h r Then, the process from steps S30 to S110 is repeated. This repetition is performed when the reinforcing plate thickness t r , reinforcement width b r , reinforcement length h r This process is repeated until a decision is made.

[0051] Next, regarding (ii), we will explain the details of the flow in Figure 17. As shown in Figure 17, first, the required performance d Set η (step S210). Next, the required performance d A standardized width-to-thickness ratio of a wrap-around type that satisfies η c SHR Calculate (step S220). In step S220, the left side of equation (14) c η 90% "Required performance d Substitute η. Next, the normalized width-to-thickness ratio calculated in step 220. c S HR Corresponding to the winding type elastic local buckling resistance c P cr Calculate (step S230). In step S230, the left side of equation (12) is "S HR Standardized width-to-thickness ratio c S HR The value of "P" can be obtained by substituting it. cr The value of "Elastic local buckling resistance" c P cr Let's assume that.

[0052] Next, the thickness of the reinforcing plate t r and reinforcing material width b r One of them is tentatively set (step S240). Next, the elastic local buckling strength calculated in step S230 c P cr Then, from the value provisionally set in step S240, the reinforcing plate thickness t r and reinforcing material width b r The other value of the two is calculated (step S250). In step S250, the elastic local buckling resistance is added to the left side of equation (11). c P cr Substitute the value and find the reinforcing plate thickness t on the right side. r and reinforcing material width b r Substitute the provisionally set value into one of the values.

[0053] Next, the reinforcing plate thickness t set in steps S240 and S250. r and reinforcing material width b r Using, n P cr ≧ c P cr Reinforcement length h such that the condition is met r The conditions are calculated (step S260). In step S260, the reinforcing plate thickness t set in steps S240 and S250 is calculated. r and reinforcing material width b r Substitute this into the right-hand side of equation (10) and obtain the elastic local buckling resistancec P cr The reinforcement length h such that the value is less than or equal to the right-hand side. r Next, we determine the conditions for the reinforcing plate thickness t. r , reinforcement width b r , reinforcement length h r Determine the reinforcement length h that satisfies the conditions determined in step S260 (step S270). In step S270, determine the reinforcement length h that satisfies the conditions determined in step S260. r Determine the thickness of the reinforcing plate t. r , reinforcement width b r This will be determined by the value provisionally set in steps S240 and S250.

[0054] Next, the operation and effects of the design method for the square steel pipe column reinforcement structure according to this embodiment will be described. Note that the expressions "first step," "second step," and "third step" in the claims are numbers assigned for convenience, and if there is no expression in the claims that specifies the order, the order is not specified and may be changed as appropriate.

[0055] A design method for a square steel pipe column reinforcement structure 100, as shown in Figure 17, comprises a square steel pipe column 1 and a plate-shaped reinforcing member 20 provided on at least one of the outer and inner surfaces of the side wall portion 10 of the square steel pipe column 1 at a position spaced apart from the longitudinal end face of the square steel pipe column 1, and comprises: a step S210 to set the required performance of the square steel pipe column reinforcement structure 100; steps S220, S230 to calculate the winding-type elastic local buckling strength based on the set required performance; steps S240, S250 to provisionally set some parameters relating to the reinforcing member 20; a step S260 to calculate the conditions for other parameters relating to the reinforcing member 20 using the calculated winding-type elastic local buckling strength and the provisionally set some parameters; and a step S270 to determine the parameters using the conditions calculated in step S260.

[0056] The design method for this square steel pipe column reinforcement structure 100 includes steps S220 and S230, which calculate the winding-type elastic local buckling resistance based on the set required performance. This makes it possible to design the square steel pipe column 1 so that a winding-type deformation mode, which efficiently improves deformation performance, is more likely to occur. Furthermore, the design method for the square steel pipe column reinforcement structure 100 includes steps S240 and S250, which provisionally set some parameters related to the reinforcing material 20, and step S260, which calculates the conditions for other parameters related to the reinforcing material 20 using the calculated winding-type elastic local buckling resistance and the provisionally set some parameters. In this way, by provisionally setting some parameters related to the reinforcing material 20 so that the winding-type elastic local buckling resistance satisfies the required performance, and calculating the conditions for the remaining parameters based on these provisional settings, the parameters required to satisfy the required performance can be easily determined. Thus, deformation performance can be appropriately improved with a simple design method.

[0057] In steps S220 and S230, the standardized width-to-thickness ratio of the wrapped type that satisfies the set required performance is calculated (step S220), and the elastic local buckling strength of the wrapped type corresponding to the standardized width-to-thickness ratio is calculated (step S230). In this case, the elastic local buckling strength of the wrapped type can be easily calculated by using the standardized width-to-thickness ratio.

[0058] The standardized width-to-thickness ratio of the wrap-around type may be calculated based on the relationship between the plastic deformation ratio of the wrap-around type and the standardized width-to-thickness ratio of the wrap-around type. In this case, the standardized width-to-thickness ratio of the wrap-around type can be easily calculated based on a predetermined relationship.

[0059] Specifically, the relationship between the plastic deformation ratio of the wrap-around type and the standardized width-to-thickness ratio of the wrap-around type is as follows: c η 90% The standardized width-to-thickness ratio of the wrap-around type square steel pipe column is c S HR In that case, it can be shown by equation (14).

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[0060] The elastic local buckling resistance of a wrapped-type column may be calculated based on the relationship between the standardized width-to-thickness ratio and the elastic local buckling resistance of the reinforced square steel pipe column. In this case, the elastic local buckling resistance of a wrapped-type column can be easily calculated based on a predetermined relationship.

[0061] Specifically, the relationship between the standardized width-to-thickness ratio and the elastic local buckling resistance of the reinforced square steel pipe column is given by setting the standardized width-to-thickness ratio to S HR Assuming the yield point of an unreinforced square steel pipe column is σ y Assuming that the plastic section modulus of an unreinforced square steel pipe column is Z p The elastic local buckling resistance of the reinforced square steel pipe column is given by P cr If the length of the square steel pipe column is 2L, then it can be expressed by equation (12).

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[0062] In steps S240 and S250, one of the parameters, the thickness of the reinforcing plate and the width of the reinforcing material, may be provisionally set (step S240), and the other value may be calculated based on the relationship between the elastic local buckling strength of the wrap-around type, the thickness of the reinforcing plate, and the width of the reinforcing material (step S250). In this case, the elastic local buckling strength of the wrap-around type can be easily calculated based on a predetermined relationship. In this case, both the thickness of the reinforcing plate and the width of the reinforcing material 20 can be provisionally set based on a predetermined relationship.

[0063] Specifically, the relationship between the elastic local buckling strength of the wrap-around type, the thickness of the reinforcing plate, and the width of the reinforcing plate is as follows: c P cr Let D be the diameter of the square steel pipe column, 2L be the length of the square steel pipe column, t be the plate thickness of the square steel pipe column, E be the Young's modulus of the square steel pipe column, ν be the Poisson's ratio of the square steel pipe column, and t be the plate thickness of the reinforcing material. r The width of the reinforcing material is set to b r Assuming that the cross-sectional area of ​​the reinforcing material is evenly distributed around the outer circumference of the square steel pipe column, the increased thickness of the square steel pipe column is t rIf we assume that the section modulus of the assumed rectangular steel pipe column is Z', then it can be expressed by equation (11).

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[0064] In steps S240 and S250, some parameters, such as the thickness and width of the reinforcing plate, are provisionally set. In step S260, using the provisionally set thickness and width, the conditions for the reinforcement length, which is another parameter, may be calculated so that the elastic local buckling strength of the wrap-around type is less than or equal to the elastic local buckling strength of the non-wrap-around type, based on the relationship between the elastic local buckling strength of the non-wrap-around type, the thickness of the reinforcing plate, the width of the reinforcing plate, and the reinforcement length. In this case, the other parameters can be calculated under conditions that allow for efficient improvement of deformation performance due to the predetermined relationship between the elastic local buckling strength of the non-wrap-around type, the thickness of the reinforcing plate, the width of the reinforcing plate, and the reinforcement length, and the occurrence of the wrap-around deformation mode.

[0065] Specifically, the relationship between the elastic local buckling strength of the wrap-around type, the thickness of the reinforcing plate, and the width of the reinforcing plate is as follows: c P cr Let D be the diameter of the square steel pipe column, 2L be the length of the square steel pipe column, t be the plate thickness of the square steel pipe column, E be the Young's modulus of the square steel pipe column, ν be the Poisson's ratio of the square steel pipe column, and t be the plate thickness of the reinforcing material. r The width of the reinforcing material is set to b r Assuming that the cross-sectional area of ​​the reinforcing material is evenly distributed around the outer circumference of the square steel pipe column, the increased thickness of the square steel pipe column is t r Assuming that the section modulus of the assumed square steel pipe column is Z', the relationship between the non-wrapping elastic local buckling strength, reinforcing plate thickness, reinforcing width, and reinforcing length is given by equation (11), and the non-wrapping elastic local buckling strength n P cr Let D be the diameter of the rectangular steel pipe column, 2L be the length of the rectangular steel pipe column, t be the plate thickness of the rectangular steel pipe column, E be the Young's modulus of the rectangular steel pipe column, ν be the Poisson's ratio of the rectangular steel pipe column, Z be the section modulus of the rectangular steel pipe column, and t be the plate thickness of the reinforcing material. r The reinforcement length from the end face to the end of the reinforcing material is set to h rThe width of the reinforcing material is set to b r In this case, the formula is shown in equation (10), and in step S260, the provisionally set reinforcing plate thickness and reinforcing width are used. n P cr ≧ c P cr You may calculate the condition for the reinforcement length, which is another parameter, so that it results in the above.

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[0066] The design method for the square steel pipe column reinforcement structure 100 shown in Figure 16 comprises a square steel pipe column 1 and a plate-shaped reinforcing member 20 provided at a position spaced apart from the longitudinal end face of the square steel pipe column 1 on at least one of the outer and inner surfaces of the side wall portion 10 of the square steel pipe column 1, and the design method for the square steel pipe column reinforcement structure 100 comprises a step S10 (first step) of setting the required performance of the square steel pipe column reinforcement structure 100, a step S20 (second step) of provisionally setting parameters related to the reinforcing member 20, and based on the values ​​of the parameters provisionally set in step S20 (second step), a wrap-around type elastic local The method comprises: step S30 (third step) of calculating the buckling strength and the non-wrapping elastic local buckling strength, respectively; step S40 (fourth step) of comparing the wrapping-type elastic local buckling strength and the non-wrapping-type elastic local buckling strength and selecting one of the deformation modes; steps S50, S60, S70, S90, S100, S110 (fifth step) of calculating the performance of the square steel pipe column reinforcement structure 100 based on the elastic local buckling strength of the one deformation mode; and step S80 (sixth step) of determining the parameters with provisionally set values ​​if the calculated performance meets the required performance.

[0067] The design method for the square steel pipe column reinforcement structure 100 includes a step S30 (third step) in which, based on the parameter values ​​provisionally set in step S20 (second step), the elastic local buckling strength of the wrapped type and the elastic local buckling strength of the non-wrapped type are calculated, respectively, and a step S40 (fourth step) in which the elastic local buckling strength of the wrapped type and the elastic local buckling strength of the non-wrapped type are compared and one of the deformation modes is selected. This makes it possible to select the deformation mode that is most likely to occur at the provisionally set parameter values, between the wrapped type and the non-wrapped type. Furthermore, the design method for the square steel pipe column reinforcement structure 100 includes a step S50, S60, S70, S90, S100, S110 (fifth step) in which the performance of the square steel pipe column reinforcement structure is calculated based on the elastic local buckling strength of one of the deformation modes, and a step S80 (sixth step) in which, if the calculated performance meets the required performance, the parameters are determined at the provisionally set values. In this case, the parameters that satisfy the required performance can be easily determined for the selected deformation mode. Therefore, deformation performance can be appropriately improved with a simple design method.

[0068] In steps S50, S60, S70, S90, S100, and S110 (the fifth step), the standardized width-to-thickness ratio of one deformation mode is calculated based on the elastic local buckling strength of one deformation mode (steps S50 and S90), and the plastic deformation ratio corresponding to the standardized width-to-thickness ratio is calculated (steps S60 and S100). In this case, the performance of the square steel pipe column reinforcement structure 100 can be easily calculated by using the standardized width-to-thickness ratio and the plastic deformation ratio.

[0069] The standardized width-to-thickness ratio for one deformation mode may be calculated based on the relationship between the standardized width-to-thickness ratio and the elastic local buckling resistance. In this case, the standardized width-to-thickness ratio for one deformation mode can be easily calculated based on a predetermined relationship.

[0070] Specifically, the aforementioned relationship between the standardized width-to-thickness ratio and the elastic local buckling resistance of the reinforced square steel pipe column is given by setting the standardized width-to-thickness ratio to S HR Assuming the yield point of an unreinforced square steel pipe column is σ y Assuming that the plastic section modulus of an unreinforced square steel pipe column is Zp The elastic local buckling resistance of the reinforced square steel pipe column is given by P cr If the length of the square steel pipe column is 2L, then it can be expressed by equation (12).

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[0071] The plastic deformation ratio of one deformation mode may be calculated based on the relationship between the plastic deformation ratio of the one deformation mode and the standardized width-to-thickness ratio of the one deformation mode. In this case, the plastic deformation ratio of one deformation mode can be easily calculated based on a predetermined relationship.

[0072] Specifically, the relationship between the plastic deformation ratio of the non-wrapping type and the normalized width-to-thickness ratio of the wrapping type is as follows: n η 90% The standardized width-to-thickness ratio of non-wrapped rectangular steel pipe columns is n S HR In this case, the relationship between the plastic deformation ratio of the wrap-around type and the standardized width-to-thickness ratio of the wrap-around type is given by equation (13), where the plastic deformation ratio of the wrap-around type is c η 90% The standardized width-to-thickness ratio of the wrap-around type square steel pipe column is c S HR In that case, it can be shown by equation (14).

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[0073] In step S20 (the second step), the thickness of the reinforcing plate, the width of the reinforcing material 20, and the length of the reinforcing material may be provisionally set as parameters. In this case, the elastic local buckling strength can be easily calculated from the provisionally set parameters.

[0074] In step S30 (the third step), the elastic local buckling resistance of the wrapped type may be calculated based on the relationship between the parameters and the elastic local buckling resistance of the wrapped type, and the elastic local buckling resistance of the non-wrapped type may be calculated based on the relationship between the parameters and the elastic local buckling resistance of the non-wrapped type. In this case, the elastic local buckling resistance of both the wrapped and non-wrapped types can be easily calculated based on predetermined relationships.

[0075] Specifically, the relationship between the parameters and the non-entrapment type elastic local buckling resistance is the analytical solution of the non-entrapment type elastic local buckling resistance. n P cr Let D be the diameter of the rectangular steel pipe column, 2L be the length of the rectangular steel pipe column, t be the plate thickness of the rectangular steel pipe column, E be the Young's modulus of the rectangular steel pipe column, ν be the Poisson's ratio of the rectangular steel pipe column, Z be the section modulus of the rectangular steel pipe column, and t be the plate thickness of the reinforcing material. r The reinforcement length from the end face to the end of the reinforcing material is set to h r The width of the reinforcing material is set to b r In this case, the relationship between the parameter and the elastic local buckling resistance of the wrap-around type is given by the analytical solution of the elastic local buckling resistance of the wrap-around type. c P cr Let D be the diameter of the square steel pipe column, 2L be the length of the square steel pipe column, t be the plate thickness of the square steel pipe column, E be the Young's modulus of the square steel pipe column, ν be the Poisson's ratio of the square steel pipe column, and t be the plate thickness of the reinforcing material. r The width of the reinforcing material is set to b r Assuming that the cross-sectional area of ​​the reinforcing material is evenly distributed around the outer circumference of the square steel pipe column, the increased thickness of the square steel pipe column is t r If we assume that the section modulus of the assumed rectangular steel pipe column is Z', then it can be expressed by equation (11).

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[0076] If the calculated performance in step S80 (the sixth step) does not meet the required performance, the process may return to step S20 (the second step) and provisionally set the parameters with other values. This allows for provisionally setting the parameters again to meet the required performance.

[0077] The square steel pipe column reinforcement structure 1 according to this embodiment is manufactured using the design method for the square steel pipe column reinforcement structure 1 described above. With this square steel pipe column reinforcement structure 1, the same functions and effects as those of the design method for the square steel pipe column reinforcement structure 1 described above can be obtained.

[0078] The present invention is not limited to the embodiments described above. The dimensions described in the embodiments above are merely examples and may be modified as appropriate without departing from the spirit of the present invention.

[0079] For example, the shape of the reinforcing member 20 is not limited to the embodiments described above. For example, the shape shown in Figure 18 may be used. In Figure 18, the reinforcing member 20 provided on one side wall portion 10 is divided into two. The number of divisions and the method of division are not particularly limited.

[0080] [Form 1] Square steel pipe columns and A method for designing a reinforced rectangular steel pipe column structure, comprising: a plate-shaped reinforcing member provided on at least one of the outer and inner surfaces of the side wall portion of the rectangular steel pipe column at a position spaced apart from the longitudinal end face of the rectangular steel pipe column; A first step of setting the required performance of the aforementioned square steel pipe column reinforcement structure, A second step involves provisionally setting parameters related to the reinforcing material, A third step involves calculating the elastic local buckling strength of the wrapped type and the elastic local buckling strength of the non-wrapped type, respectively, based on the parameter values ​​provisionally set in the second step. A fourth step involves comparing the elastic local buckling resistance of the wrapped type with the elastic local buckling resistance of the non-wrapped type and selecting one of the deformation modes. A fifth step of calculating the performance of the square steel pipe column reinforcement structure based on the elastic local buckling resistance of the aforementioned deformation mode, A design method for a square steel pipe column reinforcement structure, comprising: a sixth step of determining the parameters using provisionally set values ​​if the calculated performance satisfies the required performance. [Form 2] The design method for a square steel pipe column reinforcement structure according to Embodiment 1, wherein in the fifth step, the standardized width-to-thickness ratio of the one deformation mode is calculated based on the elastic local buckling strength of the one deformation mode, and the plastic deformation ratio corresponding to the standardized width-to-thickness ratio is calculated. [Form 3] The design method for a square steel pipe column reinforcement structure according to Embodiment 2, wherein the standardized width-to-thickness ratio of one of the deformation modes is calculated based on the relationship between the standardized width-to-thickness ratio and the elastic local buckling resistance. [Form 4] The relationship between the standardized width-to-thickness ratio and the elastic local buckling resistance of the reinforced square steel pipe column is as follows: Standardized width-to-thickness ratio is S HR year, The yield point of the unreinforced square steel pipe column is σ y year, The plastic section modulus of the unreinforced square steel pipe column is Z p year, The elastic local buckling resistance of the reinforced square steel pipe column is P cr year, The design method for the square steel pipe column reinforcement structure described in Embodiment 3, given that the length of the square steel pipe column is 2L, is shown by equation (12).

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[0081] 1...Square steel pipe column, 10...Side wall section, 20...Reinforcement material, 100...Square steel pipe column reinforcement structure.

Claims

1. Square steel pipe columns and A method for designing a reinforced rectangular steel pipe column structure, comprising: a plate-shaped reinforcing member provided on at least one of the outer and inner surfaces of the side wall portion of the rectangular steel pipe column at a position spaced apart from the longitudinal end face of the rectangular steel pipe column; A first step of setting the required performance of the aforementioned square steel pipe column reinforcement structure, A second step involves provisionally setting parameters related to the reinforcing material, A third step involves calculating the elastic local buckling strength of the wrapped type and the elastic local buckling strength of the non-wrapped type, based on the parameter values ​​provisionally set in the second step, A fourth step involves comparing the elastic local buckling resistance of the wrapped type with the elastic local buckling resistance of the non-wrapped type and selecting one of the deformation modes. A fifth step of calculating the performance of the square steel pipe column reinforcement structure based on the elastic local buckling resistance of the one deformation mode described above, A design method for a square steel pipe column reinforcement structure, comprising: a sixth step of determining the parameters using provisionally set values ​​if the calculated performance satisfies the required performance.

2. The design method for a square steel pipe column reinforcement structure according to claim 1, wherein in the fifth step, the standardized width-to-thickness ratio of the one deformation mode is calculated based on the elastic local buckling strength of the one deformation mode, and the plastic deformation ratio corresponding to the standardized width-to-thickness ratio is calculated.

3. The design method for a square steel pipe column reinforcement structure according to claim 2, wherein the standardized width-to-thickness ratio of one of the deformation modes is calculated based on the relationship between the standardized width-to-thickness ratio and the elastic local buckling resistance.

4. The relationship between the standardized width-to-thickness ratio and the elastic local buckling resistance of the reinforced square steel pipe column is as follows: Standardized width-to-thickness ratio is S ＨＲ year, The yield point of the unreinforced square steel pipe column is σ ｙ year, The plastic section modulus of the unreinforced square steel pipe column is Z. ｐ year, The elastic local buckling resistance of the reinforced square steel pipe column is P ｃｒ year, The design method for a square steel pipe column reinforcement structure according to claim 3, given that the length of the square steel pipe column is 2L, is shown by formula (12). [Math 1]

5. The design method for a square steel pipe column reinforcement structure according to claim 2, wherein the plastic deformation ratio of the one deformation mode is calculated based on the relationship between the plastic deformation ratio of the one deformation mode and the standardized width-to-thickness ratio of the one deformation mode.

6. The relationship between the plastic deformation ratio of the non-wrapping type and the normalized width-to-thickness ratio of the wrapping type is: Non-entrapment type plastic deformation ratio ｎ η ９０％ year, The standardized width-to-thickness ratio of the non-wrapped rectangular steel pipe column is ｎ S ＨＲ In that case, it is shown in equation (13), The relationship between the plastic deformation ratio of the wrap-around type and the standardized width-to-thickness ratio of the wrap-around type is: The entrainment-type plastic deformation magnification is ｃ η ９０％ defined as, The standardized width-to-thickness ratio of the wrapped-type rectangular steel pipe column is ｃ S ＨＲ In this case, the design method for the square steel pipe column reinforcement structure according to claim 5, as shown by formula (14). [Math 2]

7. The design method for a square steel pipe column reinforcement structure according to claim 1, wherein in the second step, the reinforcing plate thickness, reinforcing width, and reinforcing length of the reinforcing material are provisionally set as parameters.

8. The design method for a square steel pipe column reinforcement structure according to claim 1, wherein in the third step, the elastic local buckling strength of the wrapped type is calculated based on the relationship between the parameters and the elastic local buckling strength of the wrapped type, and the elastic local buckling strength of the non-wrapped type is calculated based on the relationship between the parameters and the elastic local buckling strength of the non-wrapped type.

9. The relationship between the aforementioned parameters and the non-entrapment type elastic local buckling resistance is as follows: Non-entrapment type elastic local buckling strength ｎ P ｃｒ year, Let D be the diameter of the aforementioned rectangular steel pipe column. The length of the aforementioned rectangular steel pipe column is 2L, Let the plate thickness of the aforementioned rectangular steel pipe column be t. Let E be the Young's modulus of the aforementioned rectangular steel pipe column. Let ν be the Poisson's ratio of the aforementioned rectangular steel pipe column. Let Z be the section modulus of the aforementioned rectangular steel pipe column. The thickness of the reinforcing material is t ｒ year, The reinforcement length from the end face to the end of the reinforcing material is h ｒ year, The width of the reinforcing material is b ｒ In that case, it is shown by equation (10), The relationship between the aforementioned parameters and the elastic local buckling resistance of the wrap-around type is: The elastic local buckling resistance of the wrap-around type ｃ P ｃｒ year, Let D be the diameter of the aforementioned rectangular steel pipe column. The length of the aforementioned rectangular steel pipe column is 2L, Let the plate thickness of the aforementioned rectangular steel pipe column be t. Let E be the Young's modulus of the aforementioned rectangular steel pipe column. Let ν be the Poisson's ratio of the aforementioned rectangular steel pipe column. The thickness of the reinforcing material is t ｒ year, The width of the reinforcing material is b ｒ year, Assuming that the cross-sectional area of ​​the reinforcing material is evenly distributed around the outer circumference of the rectangular steel pipe column, the increased thickness of the rectangular steel pipe column is t. ｒ 'year, The design method for a reinforced rectangular steel pipe column according to claim 8, given that the section modulus of the assumed rectangular steel pipe column is Z', is shown by equation (11). [Math 3]

10. The design method for a square steel pipe column reinforcement structure according to claim 1, wherein if the calculated performance in the sixth step does not meet the required performance, the process returns to the second step and the parameters are provisionally set to other values.

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