Reinforcement structure for rectangular steel pipe columns, and design method for reinforcement structure for rectangular steel pipe columns

Abstract

To provide a square steel pipe column reinforcement structure which has a simple structure and suppresses a weight and can improve the performance of a square steel pipe column, and a design method for the square steel pipe column reinforcement structure.SOLUTION: In a square steel pipe column reinforcement structure 100, by selecting an appropriate reinforcing material size according to a square steel pipe column 1 to be reinforced, local buckling of the square steel pipe column 1 is allowed, but the buckling deformation is appropriately restrained, thereby slowing down the decline in proof strength after local buckling and improving deformation performance. Furthermore, by limiting reinforcement to ends of the square steel pipe column 1 where local buckling may occur, a significant increase in the number of man-hours can be avoided. In addition, by attaching a reinforcing material 20 at a certain interval from a longitudinal end surface of the square steel pipe column 1, it is possible to prevent an excessive increase in proof strength of the square steel pipe column 1, which would affect the design of surrounding members.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a square steel pipe column reinforcement structure and a method for designing 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] In addition, as a reinforcement method intended to improve the deformation performance of a square steel pipe column, the one described in Patent Document 1 is known. Patent Document 1 describes a structure in which a reinforcing member is arranged with a gap from at least one side of the outer surface or the inner surface of the end portion of the square steel pipe column, and when the square steel pipe column undergoes local buckling deformation, the reinforcing member abuts to restrict the local buckling deformation, aiming to improve the deformation performance of the square steel pipe column. Alternatively, as a repair method intended to recover the bearing capacity of a damaged square steel pipe column, in "(Japan Building Disaster Prevention Association; Disaster Damage Classification Judgment Criteria and Restoration Technology Guidelines for Earthquake-Damaged Buildings, etc. (2015))", etc., there is described a method of recovering the bearing capacity to be equivalent to the original steel pipe by applying a cover plate from the outside and welding it to the location where local buckling deformation has occurred in a square steel pipe column damaged by an earthquake.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Here, a square steel pipe column with a large width-to-thickness ratio has a problem that when it receives an external force, it loses its bearing capacity early and thus has poor deformation performance. In addition, many of the conventional reinforcement methods for square steel pipe columns mainly aim to improve the bearing capacity, and excessive improvement in the bearing capacity may raise concerns about the impact on the design of surrounding members. When reinforcing, the interaction between the reinforcing member and the wall material may become a problem. A construction method with a complex structure may cause a significant increase in the number of man-hours to be a problem.

[0007] The present invention has been made to solve such problems, and an object thereof is to provide a square steel pipe column reinforcement structure that can improve the performance of a square steel pipe column with a simple structure and a structure that suppresses weight.

Means for Solving the Problems

[0008] The rectangular steel pipe column reinforcement structure according to the present invention comprises a rectangular steel pipe column and a plate-shaped reinforcing member provided at a position spaced apart from the longitudinal end face of the rectangular steel pipe column, with respect to at least one of the outer and inner surfaces of the side wall portion of the rectangular steel pipe column, and the assumed solution for non-wrapping type elastic local buckling resistance is P cr1 Assuming that the assumed solution for the winding-type elastic local buckling resistance is P cr2 Assuming that the plate thickness of the rectangular steel pipe column is t, and that the cross-sectional area of ​​the reinforcing material is evenly distributed around the outer circumference of the rectangular steel pipe column, the increased plate thickness of the rectangular steel pipe column is t. r If we assume this, the relationship in equation (1) holds true.

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[0009] In this square steel pipe column reinforcement structure, by selecting an appropriate reinforcing material size according to the square steel pipe column to be reinforced, local buckling of the square steel pipe column is permitted, but the buckling deformation is moderately restrained, thereby slowing the decrease in load-bearing capacity after local buckling and improving deformation performance. Furthermore, by limiting the reinforcement to the vicinity of the ends where local buckling of the square steel pipe column is likely to occur, a significant increase in man-hours can be avoided. In addition, by attaching the reinforcing material at a certain interval from the longitudinal end face of the square steel pipe column, an excessive increase in the load-bearing capacity of the square steel pipe column that would affect the design of surrounding members can be prevented. The reinforcing material has a plate-like structure, and the amount of protrusion of the reinforcing material from the surface of the square steel pipe column is small, thus reducing the impact on the interface with wall materials. Furthermore, as a result of diligent research, the inventors have found that the condition for efficiently improving deformation performance while suppressing the amount of steel material is a reinforcement specification in which the elastic local buckling resistance of the square steel pipe column itself reinforced with the reinforcing material satisfies "(non-wrapping type) ≥ (wrapping type)". Furthermore, the inventors have found that this relationship can be approximated using a hypothetical solution for the elastic local buckling resistance. Therefore, the relationship in equation (1) holds, allowing for efficient improvement of deformation performance while reducing the amount of steel used. Thus, the performance of a square steel pipe column can be improved with a simple and lightweight structure.

[0010] The square steel pipe column reinforcement structure according to the present invention includes a square steel pipe column and a plate-shaped reinforcement provided at a position spaced apart from the end surface in the longitudinal direction of the square steel pipe column with respect to at least one of the outer surface and the inner surface of the side wall portion of the square steel pipe column. Let the diameter of the square steel pipe column be D, the length of the square steel pipe column be 2L, the plate thickness of the square steel pipe column be t, and the reinforcement length from the end surface to the end of the reinforcement be h r Let the Young's modulus of the square steel pipe column be E, the Poisson's ratio of the square steel pipe column be ν, the section modulus of the square steel pipe column be Z, and assuming that the cross-sectional area of the reinforcement is evenly distributed on the outer periphery of the square steel pipe column, let the increased plate thickness be t r ’. When the section modulus of the assumed square steel pipe column is Z’, the relationship of Equation (2) holds

Equation

[0011] The square steel pipe column reinforcement structure according to the present invention includes a square steel pipe column and a plate-shaped reinforcement provided at a position spaced apart from the end surface in the longitudinal direction of the square steel pipe column with respect to at least one of the outer surface and the inner surface of the side wall portion of the square steel pipe column. Let the assumed solution of the non-wrapped elastic local buckling resistance be P cr1 Let the assumed solution of the wrapped elastic local buckling resistance be P cr2 Let the diameter of the square steel pipe column be D, the plate thickness of the square steel pipe column be t, the plate thickness of the reinforcement be t r Let the width of the reinforcement be b r ’. When the above are set, the relationship of Equation (14) holds

Equation

[0012] The square steel pipe column reinforcement structure according to the present invention includes a square steel pipe column and a plate-shaped reinforcement provided at a position spaced apart from the end surface in the longitudinal direction of the square steel pipe column with respect to at least one of the outer surface and the inner surface of the side wall portion of the square steel pipe column. Let the diameter of the square steel pipe column be D, the length of the square steel pipe column be 2L, the plate thickness of the square steel pipe column be t, and the reinforcement length from the end surface to the end of the reinforcement be h r Let the Young's modulus of the square steel pipe column be E, the Poisson's ratio of the square steel pipe column be ν, the section modulus of the square steel pipe column be Z, and the plate thickness of the reinforcement be tr 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 the relationship in equation (2) holds.

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[0013] 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, with respect to at least one of the outer and inner surfaces of the side wall portion of the square steel pipe column, wherein the reinforcement specifications are determined such that the winding-type elastic local buckling strength is less than or equal to the non-winding-type elastic local buckling strength. [Effects of the Invention]

[0014] According to the present invention, deformation performance can be efficiently improved while reducing the amount of steel used. [Brief explanation of the drawing]

[0015] [Figure 1] This is a perspective view showing a column-beam joint structure employing a rectangular steel pipe column reinforcement structure according to an embodiment of the present invention. [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 figure shows a comparison of assumed and analytical solutions and approximation formulas for the elastic local buckling resistance. [Figure 15] This graph shows the results of the local buckling characteristic determination using equation (1). [Figure 16] This figure shows the reinforcing material for a modified rectangular steel pipe column reinforcement structure. [Figure 17] This graph shows the relationship between the thickness of the reinforcing material and its deformation performance (plastic deformation ratio). [Figure 18] This graph shows the relationship between the thickness of the reinforcing material and its deformation performance (plastic deformation ratio). [Figure 19] This graph compares the results in Figure 18 with the approximate formula corresponding to the wrap-around type in Figure 14. [Figure 20] This figure shows a comparison of assumed and analytical solutions and approximation formulas for the elastic local buckling resistance. [Modes for carrying out the invention]

[0016] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[0017] 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.

[0018] 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).

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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. r The 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.

[0023] 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 rA full-scale three-point bending test (monotonic / cyclic loading) was conducted with the variable . The test 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 test 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 test specimen for "unreinforced" specimens without reinforcing members 20 was also prepared.

[0024] 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)).

[0025] 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 (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.

[0026] 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). In order to efficiently improve deformation performance compared to an unreinforced square steel pipe column while suppressing the increase in the amount of steel due to reinforcement, it can be confirmed that it is desirable to avoid non-wrapping type buckling and to have a specification that results in at least wrapping type local buckling. However, the number of combinations of square steel pipe column 1 and reinforcing material 20 is enormous, and they influence each other, so it is only through structural experiments and nonlinear analysis that it is possible to confirm which type of local buckling occurs.

[0027] Next, we will examine methods for inducing entrapment-type local buckling. We will investigate the relationship between the elastic buckling mode of the reinforced square steel pipe column 1 and the local buckling behavior in structural experiments and nonlinear analyses. First, to confirm the basic properties, we performed a linear buckling analysis of the reinforced square steel pipe column 1 itself. The analysis summary is as follows: Material properties: Young's modulus: 205000 N / mm 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.

[0028] Linear buckling analysis yields multiple combinations of elastic buckling modes and their corresponding buckling strengths. In this reinforced structure, one or both non-wound and wound elastic buckling modes were obtained for each reinforcement specification. Linear buckling analysis of the reinforced square steel pipe column 1 itself revealed elastic buckling modes with characteristics similar to the non-wound and wound local buckling behaviors observed in structural testing and nonlinear analysis.

[0029] 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.

[0030] Therefore, the condition for efficiently improving deformation performance while reducing the amount of steel used is to ensure that the reinforced square steel pipe column 1 itself has a local elastic buckling strength such that "(non-wrapped type) ≥ (wrapped type)".

[0031] Next, we will examine the evaluation method for the elastic local buckling resistance of the 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" 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". 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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[0032] Here, we consider the assumed solution P for the elastic local buckling resistance of the non-wrapped / wrapped type of square steel pipe column 1 reinforced using the following procedure. cr1 (Non-entrainment type), and assumed solution P cr2 We decided to look for a (wrap-around type).

[0033] (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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[0034] 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 values.

[0035] 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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[0036] The assumed solution P for elastic local buckling resistance derived using the procedure described above. cr1 (Non-wound type), and P cr2 The analytical solution derived from the linear buckling analysis of the reinforced square steel pipe column itself (the elastic local buckling strength derived in paragraphs 0027-0029) was compared with the (wrapped type) solution, and the analytical solution was evaluated as shown in Figure 14 by correcting the assumed solution for the elastic local buckling strength with an approximate formula that determines the reinforcement specification. The approximate formula for the non-wrapped type is shown in equation (8), and the approximate formula for the wrapped type is shown in equation (9). In paragraph 0030, it was mentioned that the condition for efficiently improving deformation performance while suppressing the amount of steel is that the reinforcement specification satisfies the elastic local buckling strength of the reinforced square steel pipe column 1 itself being "(non-wrapped type) ≥ (wrapped type)". This relationship can be replaced with equation (10) by using equations (8) and (9). In other words, since "(non-wrapped type) ≥ (wrapped type)", we derive equation (10) such that "equation (8) ≥ equation (9)", and rearranging equation (10) gives equation (1). Therefore, in order to efficiently improve deformation performance while keeping the amount of steel down, it is sufficient to satisfy equation (1) below using the conditions for the square steel pipe column 1 and the reinforcing material 20. Furthermore, equation (1) can be specifically written using equations (4) and (5) as shown in equation (2). "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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[0037] Figure 15 shows equation (1) in a graph. The grayscale region E1 in Figure 15 represents the range that satisfies equation (1). As can be seen from the plot in Figure 15, this region E1 is the range where non-enveloping types can be avoided and enveloping types can be created.

[0038] Next, the operation and effects of the square steel pipe column reinforcement structure 100 according to this embodiment will be described.

[0039] The rectangular steel pipe column reinforcement structure 100 according to this embodiment comprises a rectangular steel pipe column 1 and a plate-shaped reinforcing member 20 provided at a position spaced apart from the longitudinal end face of the rectangular steel pipe column 1 on at least one of the outer and inner surfaces of the side wall portion of the rectangular steel pipe column 1, and the assumed solution for non-wrapping type elastic local buckling resistance is P cr1 Assuming that the assumed solution for the winding-type elastic local buckling resistance is P cr2 Assuming that the plate thickness of the rectangular steel pipe column 1 is t, and that the cross-sectional area of ​​the reinforcing material 20 is evenly distributed around the outer circumference of the rectangular steel pipe column 1, the increased plate thickness of the rectangular steel pipe column 1 is t. r If we assume this, the relationship in equation (1) holds true.

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[0040] In this square steel pipe column reinforcement structure 100, by selecting an appropriate reinforcing material size according to the square steel pipe column 1 to be reinforced, local buckling of the square steel pipe column 1 is permitted, but the buckling deformation is moderately restrained, thereby slowing the decrease in load-bearing capacity after local buckling and improving deformation performance. Furthermore, by limiting the reinforcement to the vicinity of the ends of the square steel pipe column 1 where local buckling may occur, a significant increase in man-hours can be avoided. In addition, by attaching the reinforcing material 20 at a certain interval from the longitudinal end face of the square steel pipe column 1, an excessive increase in the load-bearing capacity of the square steel pipe column 1 that would affect the design of surrounding members can be prevented. The reinforcing material 20 has a plate-like structure, and since the amount of protrusion of the reinforcing material 20 from the surface of the square steel pipe column 1 is small, the impact on the interface with wall materials can be reduced. Furthermore, as a result of diligent research, the inventors have found that the condition for efficiently improving deformation performance while reducing the amount of steel is to use a reinforcement specification in which the elastic local buckling strength of the square steel pipe column 1 itself, reinforced with the reinforcing material 20, satisfies "(non-wrapping type) ≥ (wrapping type)". The inventors have also found that this relationship can be approximated using an assumed solution for the elastic local buckling strength. Therefore, by satisfying the relationship in equation (1), it is possible to efficiently improve deformation performance while reducing the amount of steel.

[0041] The rectangular steel pipe column reinforcement structure 100 according to this embodiment comprises a rectangular steel pipe column 1 and a plate-shaped reinforcing member 20 provided at a position spaced apart from the longitudinal end face of the rectangular steel pipe column 1 on at least one of the outer and inner surfaces of the side wall portion of the rectangular steel pipe column 1, wherein the diameter of the rectangular steel pipe column 1 is D, the length of the rectangular steel pipe column 1 is 2L, the plate thickness of the rectangular steel pipe column 1 is t, and the reinforcement length from the end face to the end of the reinforcing member 20 is h. r Let E be the Young's modulus of the rectangular steel pipe column 1, ν be the Poisson's ratio of the rectangular steel pipe column 1, and Z be the section modulus of the rectangular steel pipe column 1. Assuming that the cross-sectional area of ​​the reinforcing material 20 is evenly distributed around the outer circumference of the rectangular steel pipe column 1, the thickness of the increased thickness of the rectangular steel pipe column 1 is t. r If we assume that the section modulus of the assumed rectangular steel pipe column is Z', then the relationship in equation (2) holds.

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[0042] Furthermore, by selecting an appropriate reinforcement specification according to the square steel pipe column 1 to be reinforced, local buckling of the square steel pipe column 1 is permitted, but by moderately restraining the buckling deformation, the decrease in load-bearing capacity after local buckling can be slowed down, and the deformation performance can be improved. In addition, by limiting the reinforcement to the ends of the square steel pipe column 1 where local buckling may occur, a significant increase in man-hours can be avoided. Furthermore, by using readily available steel materials, the increase in cost can be kept down. In addition, by attaching the reinforcing material 20 at a certain distance from the diaphragm surface, an excessive increase in the load-bearing capacity of the square steel pipe column 1 can be suppressed. Moreover, the plate thickness of the reinforcing material 20 can be kept below the plate thickness of the square steel pipe column 1, and since the protrusion of the reinforcing material 20 from the face of the square steel pipe column 1 is small, there is little impact on the interface with the wall material.

[0043] The design method for the square steel pipe column reinforcement structure 100 according to this embodiment 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 of the square steel pipe column 1, wherein the reinforcement specifications are determined such that the winding-type elastic local buckling strength is less than or equal to the non-winding-type elastic local buckling strength.

[0044] 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.

[0045] For example, the shape of the reinforcing member 20 is not limited to the embodiments described above. For example, the shape shown in Figure 16 may be used. In Figure 16, 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.

[0046] Figures 9 and 10 show the reinforcement length ratio h r This is the result when / D = 0.4 to 1.2. To include reinforcement lengths greater than this, the reinforcement length ratio h r When "2.2" is added to / D and a graph is created, the graph corresponding to Figure 9 becomes the graph in Figure 17, and the graph corresponding to Figure 10 becomes the graph in Figure 18. As shown in Figure 19, when this result is compared with the approximate formula corresponding to the encirclement type in the aforementioned formula (9) (the solid line graph in the figure), an outlier appears. Therefore, h r Equations (11) and (12), which are modified versions of equations (8) and (9), may be adopted as formulas applicable to all values ​​including / D≧1.2. Figures 20(a) and (b) show a comparison of assumed and analytical solutions for the elastic local buckling resistance of non-wound and wound types of reinforced square steel pipe columns, and the correspondence with equations (11) and (12), respectively.

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[0047] Based on equations (11) and (12), h r As an expression applicable to all values ​​including / D≧1.2, you may adopt expressions (13), (14), and (15), which are rewritten versions of expressions (10), (1), and (2). Note that the expressions (8), (9), (10), (1), and (2) are h r This can be used as a corresponding value for / D=0.4 to 1.2.

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[0048] 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 The rectangular steel pipe column comprises 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, The assumed solution for non-entrapment type elastic local buckling resistance is P ｃｒ１ year, The assumed solution for the winding elastic local buckling resistance is P ｃｒ２ year, Let the plate thickness of the aforementioned rectangular steel pipe column be t. 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 In this case, the relationship in equation (1) holds true for the square steel pipe column reinforcement structure. [Math 1]

2. Square steel pipe columns and The rectangular steel pipe column comprises 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, 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. The reinforcement length from the end face to the end of the reinforcing material is h ｒ year, 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. 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, Given that the section modulus of the aforementioned square steel pipe column is Z', the relationship in equation (2) holds true for the square steel pipe column reinforcement structure. [Math 2]

3. Square steel pipe columns and The rectangular steel pipe column comprises 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, The assumed solution for non-entrapment type elastic local buckling resistance is P ｃｒ１ year, The assumed solution for the winding elastic local buckling resistance is P ｃｒ２ year, Let D be the diameter of the aforementioned rectangular steel pipe column. Let the plate thickness of the aforementioned rectangular steel pipe column be t. The thickness of the reinforcing material is t ｒ year, When the width of the reinforcing material is b ｒ A square steel pipe column reinforcement structure in which the relationship of formula (14) holds. [Math 3]

4. Square steel pipe columns and The rectangular steel pipe column comprises 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, 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. The reinforcement length from the end face to the end of the reinforcing material is h ｒ year, 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 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, A square steel pipe column reinforcement structure in which, given the section modulus of the assumed square steel pipe column as Z', the relationship in equation (15) holds. [Math 4]

5. 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 design method for reinforcing a rectangular steel pipe column, in which the reinforcement specifications are determined so that the elastic local buckling strength of the wrapped section is less than or equal to the elastic local buckling strength of the non-wrapped section.

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