Method for designing steel frame truss including construction member and steel frame truss

Abstract

To provide a design method of a steel frame truss partially including a binding bolt interval section wider than a general part in which a binding bolt interval of an assembling member is a predetermined dimension or less, and the steel frame truss.SOLUTION: In the design of the steel frame truss using a computer, 1) specifications of a bolt assembly cross-section (BT) material and other members are input by an input device, 2) the specifications of the BT material are stored in a storage device, 3) stresses of all the members are calculated by an arithmetic device, 4) allowable axial proof stresses of the other members are calculated by a general calculation method, 5) the allowable axial proof stress of the BT material is calculated in consideration of an inter-bolt dimension, and 6) when all the members of the BT material and the other members satisfy a stress intensity ratio σ / f ≤ 1.0, a calculation result is output and the design is ended. 7) When the other member σ / f> 1.0 and the BT material σ / f ≤ 1.0, the specifications of the other member are changed and recalculated in the procedures 1 to 6, and 8) when the BT material σ / f> 1.0, the specifications of the BT material are changed, the allowable axial proof stress is recalculated in the procedure 5, and recalculated in the procedures 1 to 7. The above procedure is repeated until all the members satisfy σ / f ≤ 1.0.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a steel truss used as a beam or column of a steel structure. [Background technology]

[0002] In steel trusses consisting of chord members and lattice members, CT steel sections have sometimes been used for the chord members. CT steel sections are manufactured by splitting H-section steel in two at the center of the web, but the thickness of the web of the H-section steel is the same as the flange thickness and is thinner than the flange. In addition, after splitting into two to form a T-section, the cut edge of the web has nothing to restrain the outward direction of the plate, which causes a significant decrease in the compressive buckling strength of the T-section.

[0003] Furthermore, when CT steel is used as the chord material of a steel truss, the lattice material is attached to the web of the CT steel. However, when L-shaped steel is used as the lattice material, the flange surface of the L-shaped steel is usually placed on top of the web surface of the CT steel and joined with bolts or welding.

[0004] However, if the length of the overlapping portion between the lattice material and the web of the CT steel (hereinafter referred to as the lattice joint) is not sufficient, the strength of the lattice joint cannot transmit the axial force of the lattice material, so in that case it was necessary to weld a splice plate to the web of the CT steel to widen the web width.

[0005] As mentioned above, welding a splice plate to the web of a CT steel beam requires additional labor, such as correcting distortion caused by welding heat and grinding the weld bead area to prevent gaps at the contact surface with the lattice material, resulting in problems in terms of time, effort, and cost.

[0006] To address the problem of welding splice plates to partially widen the web width, one method is to weld two flat plates together to form a T-shaped cross section. This method allows the web width to be partially widened as needed, and the web thickness can be selected independently of the flange thickness, making it possible to ensure the compressive buckling strength of the web and also making it easy to ensure the strength of the lattice joints that can fully transmit the axial force of the lattice material.

[0007] However, the method of assembling two flat plates by welding them together to form a T-shaped cross section usually requires a considerable amount of welding, as the flange side is continuously welded to the other side, which will become the web, and the distortion caused by the welding heat must be corrected along the entire length of the member, so it cannot be said that this method necessarily improves on the issues of effort and cost that were present with the CT-shaped steel.

[0008] One possible solution is to use assembled T-section members (hereafter referred to as BT members) in which the flanges and webs are assembled with bolts, using angle irons (or angle iron pieces) as connecting members, rather than welding them together. This method eliminates the labor and cost of welding, including distortion correction, and allows for the creation of T-section chord members in which only the lattice joints have wide webs.

[0009] However, when bolt-assembled BT timbers such as those described above are used as chord members in trusses, there are problems with maintaining the integrity of the BT timbers under compression. Regarding the effective buckling length of assembled members, taking into account the spacing between the staking bolts (equivalent to the buckling length of individual members, where individual members refer to the portion of a member whose length is the distance between the staking bolts; the same applies below), the Architectural Institute of Japan's Steel Structure Design Standards include provisions for assembled members. However, these provisions assume that spacing between staking bolts is as uniform as possible (as per the structural details of the aforementioned regulations). Therefore, if the spacing between staking bolts connecting the flange and web is significantly wider than in general sections for fit reasons, member design that applies these provisions cannot be considered appropriate. Examples of cases where the spacing between staking bolts is significantly wider than in general sections include cases where lattice joints are omitted to avoid interference with lattice members in sections including lattice joints, or to minimize the number of staking bolts in sections with low axial stress.

[0010] The formula for calculating the effective buckling length of an assembled member according to the above regulations assumes that the slenderness ratio of the individual members to the dimension between the joining bolts is in the range of λ1≦50. For example, if the cross-sectional dimensions of a plate material are 16 mm thick x 200 mm wide, the minimum (weak axis) cross-sectional secondary radius i=0.46 cm, so the buckling length of the individual member corresponding to λ1≦50 is l1=0.46 cm×50≦230 mm, and therefore it is quite possible that the dimension between the joining bolts in the section of the chord material including the lattice joint will be longer than 230 mm.

[0011] Therefore, when the chord is made of BT material that includes a section where the spacing between the bolts is longer than in general sections, such as the lattice joints where the flange and web are not integrated, the compressive strength of this section may be smaller than the compressive strength of the chord calculated assuming that the spacing between the bolts of the BT material conforms to the above regulations over its entire length, and therefore this section must be considered separately and individually.

[0012] This problem applies not only to BT materials, but also to any bolt-assembled member that includes a section where the inter-bolt dimension is longer than in a general section, when treating it as a single-section member, and attention must also be paid to H-section members, for example, which are sometimes used in truss members.

[0013] However, the above regulations do not reflect this point, and it is desirable to establish a design method for assembly members that include a section with a wider bolt spacing than the general section.

[0014] An example of a prior art document relating to steel assembly members fabricated by joining together with bolts is Patent Document 1. The invention described in Patent Document 1 discloses a technology for fabricating steel assembly members with a wide variety of cross-sectional shapes by using at least one flat surface of an open-section steel member formed by bending high-strength steel plates to form multiple flat surfaces in the width direction as a joint, and using bolt holes opened in the joint to pressure-join multiple open-section steel members with ultra-high-strength fasteners.

[0015] In the invention described in Patent Document 1, as can be seen from the uniform spacing of the fastener holes shown in all of the drawings, it is considered reasonable to understand that the premise is that the spacing of the fasteners that fasten the steel assembly members together is a uniform spacing dimension below a certain dimension so that the steel assembly member can fully demonstrate its cross-sectional performance as a single member. In other words, with regard to the design method for assembly members that include a section with a wider spacing between fasteners than the general section, which is the problem related to the present invention, there is no disclosure of the problem or a means leading to a solution, nor any description that suggests it. [Prior art documents] [Patent documents]

[0016] [Patent Document 1] Patent No. 4408274 Summary of the Invention [Problem to be solved by the invention]

[0017] The present invention provides a design method for a steel truss in which, when bolt-assembled members, such as BT material or H-section material, whose cross-section has a flange and a web and is made of plate material, are used as chord members of a steel truss, the bolt spacing of the assembly member includes a section with a wider spacing than the general section below a predetermined dimension, and a steel truss designed using this design method. [Means for solving the problem]

[0018] The first means of the present invention to solve the above problem is to design a steel frame truss, 1) The computer input device inputs at least the following data: the length of the buckling section of the truss chord, the cross-sectional dimensions and bolt spacing of the plates that make up the assembly members used in the chord, and the buckling section length and cross-sectional size of other members (referring to lattice members and beam members; the same applies below). 2) The specification data regarding the assembled member input in step 1) above is stored in the storage device of the computer, which is used in step 5, which is a subroutine for calculating the allowable axial strength of the assembled member.

[0019] 3) Using the input specification data of the assembly member and other members, the calculation unit of the computer calculates stresses in the assembly member and other members. 4) The allowable axial compressive and tensile strengths of the other components are calculated by the computing device. 5) The allowable axial compressive and tensile strengths of the assembled members are calculated by the computing device in the subroutine using the specification data on the assembled members stored in the storage device in step 2).

[0020] In the subroutine procedure 5), the allowable compressive strength of the chord buckling section when the spacing between the bolts of the assembled member is assumed to be equal to or less than a predetermined dimension along the entire length, and the allowable compressive strength of the individual member buckling section, which is the section where the spacing between the bolts exceeds the predetermined dimension, are calculated, and the allowable compressive strength of the assembled member is determined by comparing the two allowable compressive strengths. Here, the chord buckling section includes the sections outside and inside the structural plane of the truss.

[0021] 6) The allowable axial strength of each of the assembly members and other members calculated in steps 4) and 5) above is compared with the calculated stress of the assembly members and other members by the calculation device, and a test is performed to determine whether or not it is within the allowable range for the truss member size. 7) If the test results show that the stress ratio σ / f of all components is 1.0 or less, the components are deemed to be within the allowable range, and the calculation results are output by the computer's output device (step 9), completing the process.

[0022] 8) If σ / f≦1.0 is not satisfied for all members, and the test result of the assembled member is σ / f≦1.0, the process returns to step 1), the specification data of the other members is changed, and the calculation is performed again by the calculation device using steps 1) to 7).On the other hand, if the test result of the assembled member is not σ / f≦1.0, the process returns to step 1), the specification data of the assembled member is changed, its allowable axial strength is recalculated using step 5), and the calculation is performed again using steps 1) to 7). 9) When the stress ratio σ / f of all members is 1.0 or less in the procedure 7), the calculation results are outputted by the output device of the computer and the procedure is completed. This is a design method for a steel truss including assembly members, characterized in that the above procedure is repeated by a computer.

[0023] A second aspect of the present invention is a design method for a steel truss, which is the first aspect of the present invention, in which step 5) is used as a subroutine to calculate the allowable compressive strength of the chord member buckling section as the chord member of the assembled member and the allowable compressive strength for the inter-bolt length of the individual member buckling section using the specification data of the assembled member stored in the storage device of the computer, by the following procedure, by an arithmetic unit of the computer.

[0024] Assuming that the spacing between the bolts in the chord buckling section is uniform throughout the entire buckling section, the effective buckling length of the chord is calculated taking into account the slenderness ratio of the portion of the chord buckling section that corresponds to the spacing between the bolts. The allowable compressive stress corresponding to this effective buckling length is then multiplied by the total cross-sectional area of ​​the chord to obtain the allowable compressive strength N of the chord in the chord buckling section. cr is calculated (step 5-1).

[0025] The sum of the allowable compressive strengths of the flanges and webs as individual members calculated by multiplying the cross-sectional areas of the flanges and webs by the allowable compressive stresses corresponding to the effective buckling lengths of the flanges and webs constituting the portion of the individual member buckling section corresponding to the length between the bolts is the allowable compressive strength for the length between the bolts in the individual member buckling section. P N cr (Step 5-2).

[0026] The allowable compressive strength N of the chord of the chord buckling section calculated from the above steps 5-1) and 5-2) cr and the allowable compressive strength of the individual member in the individual member buckling section P N cr are compared, and N cr ≦ P N cr If so, then the above N cr is the allowable compressive strength of the assembly member B N cr The allowable tensile strength of the assembly member is then calculated, and these become the allowable axial strengths of compression and tension of the assembly member (Step 5-3).

[0027] N cr ≦ P N cr If not, the process returns to step 1) of the first means of the present invention, and the specification data of the assembly member is changed. The above procedure is repeated. The above is the second means of the design method for a steel truss including assembly members, using the first means of the present invention.

[0028] In the second means, the allowable compressive strength N of the chord buckling section cr and the allowable compressive strength of the individual member buckling section P N cr In direct comparison with N cr ≦ P N cr If N cr The allowable compressive strength of the assembly member B N cr Therefore, the idea is to avoid the occurrence of buckling in the individual member buckling section. On the other hand, the allowable compressive strength of the assembly member B N cr It is also possible to consider that the buckling strength may occur in either the chord member buckling section or the individual member buckling section. In this case, the smaller of the two allowable compressive strengths is set as the allowable compressive strength of the assembled member. B N cr It will be decided that.

[0029] Therefore, the third aspect of the present invention is to provide the allowable compressive strength N cr and the allowable compressive strength of the individual member buckling section P N cr After the calculation, the smaller of the two {min(N cr , P N cr )} is the allowable compressive strength of the assembly member B N cr This is a design method for a steel truss including assembly members using the first means of the present invention, characterized in that the method proceeds to step 5-3a) of:

[0030] The second or third means of the present invention is to calculate the allowable compressive strength N of the chord buckling section.cr and the allowable compressive strength of the individual member buckling section P N cr and directly compare them to determine whether they are the allowable compressive strength of the assembly member. B N cr These methods can be used even when the length of the individual member buckling section is set arbitrarily, and are therefore versatile, but if it is assumed that buckling will not occur in the individual member buckling section, it is necessary to repeat trial and error by modifying the specification data such as the cross-sectional dimensions of the plate material or the dimensions between the bolts to achieve such a length of the individual member buckling section.

[0031] Here, the allowable compressive strength of the individual member buckling section is P N cr and the allowable compressive strength N of the chord buckling section cr Considering that the ratio of the slenderness to the effective buckling length of these buckling sections determines the allowable compressive strength of the individual buckling sections, P N cr is the allowable compressive strength N of the chord buckling section cr It is possible to set in advance the actual dimension between the bolts in the individual member buckling section so that the slenderness ratio is equal to or greater than this.

[0032] Therefore, a fourth means of the present invention is a design method for a steel truss including assembly members using the first means of the present invention, characterized in that, with regard to the spacing between the bolts of the plate materials constituting the assembly member input in step 1) of the first means of the present invention, the actual spacing between the bolts of the individual member buckling section, which is a section of the assembly member where the spacing between the bolts exceeds the predetermined dimension, is initially input by the input device of the computer in step 1), where the slenderness ratio to the effective buckling length of the individual member buckling section, which is a section of the assembly member where the spacing between the bolts exceeds the predetermined dimension, is set so that it is not greater than the slenderness ratio to the effective buckling length of the chord buckling section where the spacing between the bolts set over the entire length of the assembly member is considered to be equal to or less than the predetermined dimension.

[0033] It should be noted that the effective buckling length of the individual material buckling section is the same as the actual dimension between the bolts if the constraint conditions at both ends of this section are completely pinned, i.e., the effective buckling length coefficient k is 1.0. However, in reality, it is somewhere between completely fixed (k=0.5) and completely pinned (k=1.0). Therefore, if we assume k=0.7, for example, it is important to note that the effective buckling length is the value obtained by multiplying the actual dimension between the bolts of the individual material buckling section set as described above by k=0.7.

[0034] Furthermore, the present invention relates to a steel truss designed by the design method of a steel truss including an assembly member according to any one of the first to fourth means, and when an assembly member assembled with bolts is used as a chord member of the steel truss, the allowable compressive strength N of the chord member buckling section of the chord member is calculated by regarding the entire length of the assembly member as being equal to or less than the predetermined dimension in the chord member that includes a section with a wider bolt spacing than a general section where the bolt spacing is equal to or less than the predetermined dimension. cr and the allowable compressive strength of the individual member buckling section of the individual member, which is the section between the bolts with a dimension exceeding the predetermined dimension. P N cr and are compared, and either of these two allowable compressive strengths is the allowable compressive strength of the assembly member. B N cr A steel truss including assembly members characterized in that:

[0035] Here, in the steel truss according to the present invention, the essential item (essential condition) for the assembly member used as the chord member to be used as a structural member that receives compressive axial force is that the evaluation process for the integration state of the materials (plurality of plate materials) that reflects the installation state of the joint elements (joint bolts) is carried out based on the allowable compressive strength ( B N cr ) is incorporated into the calculation process.

[0036] Here, the evaluation process for the integration state of the materials (plurality of plate materials) is a calculation process in which the allowable compressive strength is calculated taking into account the spacing of the bolts in a specific section of the assembled member. That is, in the chord member that includes a section (i.e., a specific section) where the spacing of the bolts in the assembled member is wider than the general section where the spacing is equal to or less than a predetermined dimension, the allowable compressive strength N of the chord member buckling section of the chord member is calculated assuming that the spacing of the bolts in the assembled member is equal to or less than the predetermined dimension over the entire length. cr and the allowable compressive strength of the individual member buckling section of the individual member, which is the section between the bolts (i.e., the specific section) that exceeds the predetermined dimension. P N cr and either of these two allowable compressive strengths is the allowable compressive strength of the assembly member. B N cr This is a calculation process that is determined as follows.

[0037] That is, the allowable compressive strength N cr and P N cr Without the calculation process to calculate the allowable compressive strength of the assembly member B N cr cannot be determined, and it is impossible to design a steel truss including the assembly member according to the present invention.

[0038] Furthermore, in practice, the number and types (plate thickness, bolt spacing, etc.) of the specific sections in the structural design process for the entire truss structure can be quite large, so calculating each component individually would be extremely time-consuming and unrealistic. Therefore, it is extremely reasonable to use any of the design methods of the first to fourth means of the present invention, which utilize a computer, to solve this problem.

[0039] The assembly member is intended to be an assembly member having a cross section with a flange and a web, including a T-shaped cross section and an H-shaped cross section, assembled by bolt assembly. [Effects of the Invention]

[0040] The present invention relates to a steel truss using the above-described assembly members as chord members, and therefore has the following effects. (1) The present invention provides a design method for calculating the allowable compressive strength of an assembled member subjected to compressive axial force, even in the case of a steel truss using, as an assembled member, for example, BT material made of two flat plates assembled with bolts as a chord member, even if the assembled member includes a section of the chord member including a lattice joint where the bolt spacing is wider than in general sections below a predetermined dimension. (2) From the above (1), the calculation method of the allowable compressive strength of assembled members according to the present invention can be applied even to compression members that are outside the scope of application of the conventional design formulas for assembled members. (3) In the fabrication of steel trusses, the labor and cost of welding, including distortion correction, can be eliminated, and chord members with T-shaped cross sections, in which only the sections including the lattice joints have wide webs, can be obtained.

[0041] (4) Assembly members consisting of flanges and webs, such as BT materials or H-section materials, can be manufactured separately for the thickness and shape of the flanges and webs, allowing for free selection of thickness. Furthermore, assembly members can be easily manufactured not only in straight lines but also in arcs or free curves. (5) In particular, the intersection angle between the flange and web of T-shaped or H-shaped cross-section members, which are often used in trusses, does not always have to be a right angle. Therefore, even if the truss structural surface is twisted, such as in a free-form roof truss, by adjusting the intersection angle, it is possible to join the ends of the BT or H-shaped cross-section members, which are the chord members, to match the inclination angle of the joint surface of the plate material at the truss node. (6) According to the design method of the present invention, even for assembled members other than BT material or H-shaped cross section, the allowable compressive strength of the member buckling section as a single member calculated by assuming that the spacing between the closing bolts is equal to or less than a predetermined dimension along the entire length can be calculated by comparing the allowable compressive strength of the individual member buckling section of an individual member in which the spacing between the closing bolts exceeds the predetermined dimension. [Brief explanation of the drawings]

[0042] [Figure 1]The diagram shows an example of a simple beam of a steel truss using BT materials for the chord members, subjected to a concentrated load P. (a) shows the flange 2a and web 2b joined by a number of connecting members 6 (angle iron pieces) and fastening bolts 7, while (b) shows the case where the flange 2a and web 2b are joined by connecting member 6a (angle iron of a specified length) and fastening bolts 7. [Figure 2] 2A and 2B are diagrams illustrating the buckling deformation pattern of the steel truss in Figure 1 when the upper chord member is subjected to a compressive axial force due to a concentrated load P. (a) is a cross-sectional arrow view of the steel truss in Figure 1 taken along the line I-I, where the dashed line indicates the state in which the upper chord member 2 has buckled outside the truss structural plane. (b) is a schematic elevational view of the steel truss in Figure 1, where the dashed line indicates the state in which the portion of the upper chord member 2 between the beams 5, 5 has buckled within the truss structural plane. [Figure 3] This is a detailed view of part A in Figure 1, and is a schematic diagram showing the state (dotted line) in which the flange 2a of the upper chord member 2 of the bolt-assembled BT material is locally buckled in the lattice joint section due to the action of compressive axial forces N1, N2, Ns and tensile axial force Tr. [Figure 4] 1 is a flowchart illustrating a method for designing a steel truss according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0043] First, an example of a steel truss according to the first aspect of the present invention will be explained using BT materials with reference to Figures 1 to 4. Figure 1 shows an example of a truss beam 1 in which BT materials are used for the upper and lower chords 2, 3 of a simple beam supported vertically at both ends, and explains the buckling state of the upper chord 2, which is on the compression side, when a concentrated load P is applied to the center of the beam. The only difference between Figures 1(a) and (b) is whether the angle members of the connecting members 6 or 6a attached to both sides of the web 2b are divided or not.

[0044] The upper and lower chord members 2, 3 are BT members assembled with bolts, and the lattice members 4, 4, ... and struts 5, 5, ... are, for example, L-shaped steel. Both ends of the truss beam 1 and the upper and lower ends of the struts 5, 5 at the center of the beam and both support points where concentrated load P acts are restricted from moving outside the truss structural plane (perpendicular to the paper) (▽△ marks in Figure 2(a)). When concentrated load P acts on the center of such a truss beam 1, a compressive axial force acts on the upper chord member 2.

[0045] Figure 2(a) is a cross-sectional view of the arrow I-I in Figure 1, and shows the state when the upper chord 2 buckles due to the compressive axial force by the dashed line. The upper chord 2 is restrained from moving outside the truss plane at both ends and the center of the truss beam 1, so the buckling length outside the truss plane is L shown in Figure 2(a). k The deformation mode is an S-shape as shown by the dashed line. Also, the upper chord 2 may buckle and deform so that the portion between the beams 5, 5 protrudes into the truss structural plane, as shown by the dashed line in Figure 2(b).

[0046] Here, the assembly of the flange 2a and web 2b plates that make up the upper chord 2 is as shown in Figure 3. If the flange 2a and web 2b are joined to each other over their entire length using connecting members 6, 6, ... with bolts 7, 7, ... at the flange 2a and web 2b, respectively, with a bolt spacing of l1, then the effective slenderness ratio λ of the upper chord 2 is ye The following formula (from the Architectural Institute of Japan's "Steel Structure Design Standards") may be used to calculate this. λ ye =√(λ y 2 +m λ1 2 / 2) However, when λ1≦20, λ ye =λ y It can be regarded as such. λ y : Slenderness ratio when the material (in this example, the flange 2a and web 2b) is considered to be a complete unit m: The number of materials assembled by the binding material (in this example, m = 2) λ1=l1 / i1 λ1: Slenderness ratio of the section of the binding material (in this example, between the binding bolts) l1: Dimension of the section of the binding material (in this example, between the binding bolts) i1: Minimum cross-sectional radius of the material (In this example, the material portion having the bolt spacing dimension l1 as its material length is referred to as an individual material.)

[0047] If we assume that the flange 2a and the web 2b are uniformly connected over the entire length of the upper chord 2 with the dimension l1 between the bolts, then the effective slenderness ratio λ ye can be calculated using the above formula, and the corresponding allowable compressive stress f c The allowable compressive strength of the upper chord 2 is calculated by multiplying this by the total cross-sectional area of ​​the flange 2a and web 2b.

[0048] In the above, it was assumed that the distance between the bolts is uniform at l1 along the entire length of the upper chord member 2, but for example, in a truss beam 1, lattice members 4 are attached, so it is necessary to ensure a length where the lattice members 4 come into contact with the surface of the web 2b of the upper chord member 2. As shown in Figure 3, in the joint section of the lattice member 4 where the width of the web 2b widens (dimension between the bolts L1), the tip of the lattice member 4 may be joined as close as possible to the flange 2a. As a result, it may not be possible to attach the connector 6, and the distance between the bolts L1 may become significantly longer than the distance between the bolts l1 in the general part of the upper chord member 2.

[0049] When the truss beam 1 is subjected to a concentrated load P (see Figure 1), compressive axial forces N1, N2, and N3 are applied near the joints of the lattice members 4 as shown in Figure 3. s , tensile axial force T r In this case, since the flange 2a at the bolt spacing L1 is separated from the web 2b, the flange 2a may buckle locally as shown by the dashed line. In other words, the compressive strength of the joint section of the lattice member 4 may fall below the allowable compressive strength of the upper chord member 2. Therefore, it is necessary to determine and consider the allowable compressive strength of the flange 2a and web 2b in this section.

[0050] The allowable compressive strength of the flange 2a is calculated by calculating the slenderness ratio λ1 = L1 / i1 of the individual member (between the bolts) from the minimum cross-sectional secondary radius i1 of the plate (material) of the flange 2a only, and the corresponding allowable compressive stress f c The allowable compressive strength of the flange 2a can be calculated by multiplying this by the cross-sectional area of ​​the flange 2a.

[0051] Furthermore, regarding the allowable compressive strength of the web 2b in the portion with the dimension L1 between the bolts, since the lattice material 4 is joined so as to restrain the out-of-plane protrusion of the web 2b, if it is assumed that buckling will not occur, it can be calculated by multiplying the allowable stress of the material (= allowable tensile stress ft) by the effective cross-sectional area of ​​the web 2b in this portion (for example, to be on the safe side, it can be assumed to be the same cross-sectional area as the web 2b in the portion with the dimension l1 between the bolts).

[0052] The allowable compressive strength of the flange 2a and web 2b is then added together to determine the allowable compressive strength of the bolt spacing L1, and it can be confirmed that this is equal to or greater than the allowable compressive strength of the upper chord 2. If this is not the case, the upper chord 2 will not be able to fully demonstrate its compressive strength as an assembled member, which is uneconomical, and the conditions will need to be changed and the calculations will be re-done.

[0053] Furthermore, the length and cross-sectional size of the components that make up the truss will differ depending on their position in the truss frame (the center or end of the beam, or the capital of the column, etc.), as well as the angle and joint fit of the lattice material joined to the chord material. Therefore, the compressive strength of such localized areas, which was not considered in conventional designs, will need to be considered for all assembled components.

[0054] Changing the conditions and performing repeated calculations as described above poses the problem of significantly increasing the amount of work and time required for design, so the above design work is carried out using a computer to enable efficient design of steel trusses that include BT materials, which is an embodiment of the solution according to the present invention shown in the flowchart in Figure 4. The design procedure will be explained based on this flowchart, with the term "assembly member" in the figure being read as "BT material" in this embodiment. It is assumed that the necessary conditions such as the shape and dimensions of the truss, boundary conditions, and load conditions are given in advance.

[0055] The first aspect of the present invention is to provide a method for designing a steel frame truss, 1) The computer input device inputs at least the following data: the length of the truss chord member buckling zone, the cross-sectional dimensions of the plate material constituting the BT material used for the chord member and the dimensions between the bolts, and the buckling zone length and cross-sectional size of other members. 2) The specification data for the BT material input in step 1) is stored in the computer's memory device and used in step 5), which is a subroutine for calculating the allowable axial strength of the BT material. 3) Using the input specification data of the BT material and other materials, the stress of the BT material and other materials is calculated by the arithmetic unit of the computer.

[0056] 4) The allowable axial compressive and tensile strengths of the other components are calculated by the computing device using a general calculation method. 5) The allowable axial compressive and tensile strengths of the BT material are calculated by the computing device using the specification data on the BT material stored in the storage device in the procedure of 2).

[0057] In the subroutine procedure 5), the allowable compressive strength of the chord buckling section when the spacing between the BT material's bolts is assumed to be equal to or less than a predetermined dimension along the entire length, and the allowable compressive strength of the individual member buckling section, which is the section where the spacing between the bolts exceeds the predetermined dimension, are calculated, and the allowable compressive strength of the BT material is determined by comparing the two allowable compressive strengths. Here, the chord buckling section includes sections both outside and inside the structural plane of the truss (see Figures 2(a) and (b)).

[0058] 6) The allowable axial strength of the BT material and other members calculated in steps 4) and 5) above is compared with the stress of the BT material and other members by the computing device, and a test is performed to determine whether or not it is within the allowable range for the truss member size. 7) If the result of the test is that the stress ratio σ / f≦1.0 for all components, it is determined that they are within the allowable range and the procedure proceeds to step 9), where the calculation results are output by the computer's output device and the process is completed.

[0059] 8) If σ / f≦1.0 is not true for all members, and the test result for the BT material is σ / f≦1.0, the allowable axial strength of the other members is insufficient, so the process returns to step 1), the specification data for the other members, such as the size, is changed, and the calculation device recalculates using steps 1) to 7).On the other hand, if the test result for the BT material is not σ / f≦1.0, the process returns to step 1), the specification data for the BT material, such as the bolt spacing or cross-sectional dimensions of the plate, is changed, and the allowable axial strength is recalculated using step 5), and then recalculated using steps 1) to 7). 9) When the stress ratio σ / f of all members is 1.0 or less in the procedure 7), the calculation results are outputted by the output device of the computer and the procedure is completed. Using the above procedure, calculations are repeated by computer until the stress ratio σ / f of all components becomes 1.0 or less.

[0060] In the embodiment of the second means of the present invention, the procedure 5 of the flowchart shown in FIG. 4 described in the embodiment of the first means is used as a subroutine to calculate the length of the chord buckling section of the BT material as a chord (L in FIG. 2). k or L k The allowable compressive strength for the length between bolts in the individual member buckling section (L1 in Figure 3) is calculated by the calculation device as follows using the specification data of the assembly members stored in the storage device of the computer.

[0061] The chord buckling section (L in Figure 2) k or L k Assuming that the dimension between the bolts (l1 in Figure 3) of the buckling section (part of the buckling section) is uniform throughout the entire buckling section, the effective slenderness ratio λ of the chord is calculated using Equation 1, taking into account the slenderness ratio λ1 of the part of the buckling section corresponding to the dimension between the bolts l1. yeThe allowable compressive stress corresponding to the above is multiplied by the total cross-sectional area of ​​the chord to obtain the allowable compressive strength N cr is calculated (step 5-1).

[0062] The sum of the allowable compressive strengths of the flanges 2a and webs 2b as individual members calculated by multiplying the cross-sectional areas of the flanges 2a and webs 2b by the allowable compressive stresses corresponding to the effective buckling lengths of the flanges 2a and webs 2b constituting the length L1 between the bolts in the individual member buckling section (L1 portion in Figure 3) is the allowable compressive strength for the length L1 between the bolts in the individual member buckling section (L1 portion). P N cr (Step 5-2).

[0063] The chord buckling section (L k or L k / 2 part) as a chord member allowable compressive strength N cr and the allowable compressive strength of the individual member in the individual member buckling section (L1 part) P N cr are compared in step 5-3, and N cr ≦ P N cr If so, then the above N cr The allowable compressive strength of the BT material is B N cr (Step 5-4), and then the allowable tensile strength of the BT material is calculated (Step 5-5), and these become the allowable axial compressive and tensile strengths of the BT material as an assembly member.

[0064] N cr ≦ P N cr If not, the process returns to step 1) of the first means of the present invention, and the specification data such as the dimension between the bolts of the BT material or the cross-sectional dimension of the plate material is changed. The above procedure is repeated in an embodiment of the second means of the present invention using the first means.

[0065] In the embodiment of the third means of the present invention, in the embodiment of the second means, instead of step 5-3 shown in the flowchart of FIG. 4, the chord buckling section (L in FIG. 2) k or L k / 2) allowable compressive strength N cr and the allowable compressive strength of the individual member buckling section (L1 part in Figure 3) P N cr The smaller of {min(N cr , P N cr )} is the allowable compressive strength of the BT material B N cr This is the method to proceed to step 5-3a). That is, the allowable compressive strength of the BT material B N cr This is the idea that buckling may occur in either the chord member buckling section or the individual member buckling section.

[0066] In the embodiment of the fourth means of the present invention, in the embodiment of the first means, for the dimension between the bolts of the plate material constituting the BT material input in step 1) shown in the flowchart of FIG. 4, the bolt interval l1 set over the entire length of the BT material is considered to be less than a predetermined dimension (for example, less than 50 times the minimum secondary radius of area of ​​the plate material), and the chord buckling section (L in FIG. 2) is considered to be less than the predetermined dimension (for example, less than 50 times the minimum secondary radius of area of ​​the plate material). k or L k / 2) slenderness ratio λ to effective buckling length ye The actual spacing between bolts L1 of the individual material buckling section is set so that the slenderness ratio λ1 of the individual material buckling section, which is the spacing between bolts dimension section (L1 part in Figure 3) exceeding the predetermined dimension of the BT material, does not become too large. The spacing between bolts L1 of the individual material buckling section is first input in step 1), and the allowable compressive strength of the BT material is calculated. B N cr This is the method by which the above is calculated.

[0067] In the fourth means, the slenderness ratio of the individual member buckling section is set in advance so as not to be longer than the slenderness ratio of the chord member buckling section, so that the allowable compressive strength of the individual member buckling section is necessarily P N cris the allowable compressive strength N of the chord buckling section cr Therefore, the result of step 5) in the flowchart in Figure 4 is always N cr ≦ P N cr This eliminates the need for repeated trial and error using this subroutine, making it more efficient.

[0068] Furthermore, an embodiment of a steel truss including an assembly member according to the present invention is a steel truss designed by any one of the design methods of the first to fourth means of the present invention. For example, in the case of a truss beam 1 as shown in FIG. 1, the allowable compressive strength of the upper chord member 2 on the compression side as a BT member is B N cr Regarding the buckling length (L k or L k / 2) allowable compressive strength N cr and the allowable compressive strength of the individual member of the lattice joint section (L1 part) shown in Figure 3. P N cr The allowable compressive strengths of the BT material are compared. B N cr This is a steel truss that was determined and designed as follows.

[0069] The allowable compressive strength N cr and P N cr The calculation of the allowable compressive strength of the BT material is an essential calculation process. B N cr Therefore, it is not possible to design a steel truss including the assembly member according to the present invention.

[0070] Furthermore, in practice, in the structural design process for the entire truss frame, there can be a considerable number of locations and types (plate thickness, spacing of spacing of spacing bolts, etc.) of sections (specific sections) with wider spacing between spacing bolts than the general sections of the upper chord member 2, such as the lattice joint section (L1 section) shown in Figure 3, so it is impractical to calculate each member individually, as it would require a great deal of time and effort. Therefore, by using any of the design methods of the first to fourth means of the present invention that utilize a computer, it becomes possible to design a steel truss including assembly members in an extremely rational manner.

[0071] Although this example is for a T-section member, the same design method can be applied to an H-section member, which is sometimes used in trusses.

[0072] Here, we will describe the results of a structural comparison using an FEM analysis model between a steel truss girder according to the present invention, in which the upper and lower chord members are made of BT materials assembled with bolts, and a steel truss girder in which the upper and lower chord members are made of T-section materials assembled with welding.The analysis model for bolt-assembled BT materials is a model in which angle members of a specified length (see connecting members 6a in Figure 1(b)) are attached to both sides of the web 2b, and the connecting members 6a are connected to the flange 2a and web 2b only by bolts at specified intervals (not shown).

[0073] In addition, the analytical model of a welded T-section member is a model (not shown) in which the flange 2a and web 2b are integrated (assuming welding assembly) without the angle member (joining member 6a) that joins the flange 2a and web 2b in the above analytical model.

[0074] As mentioned above, in the case of bolt-assembled BT materials, the stress transmission between the flange 2a and web 2b that make up the chord material is carried out only at the positions of the joining bolts 7, 7, ... spaced at predetermined intervals via the joining material 6a, so the purpose was to confirm, within the elastic range, the difference from when the flange and web are integrated.

[0075] The assumptions are as follows: Truss dimensions: Total length = 8m, truss depth = 2m Material size: (chord material) assembly T-150 x 200 x 9 x 16, (Lattice, beam) 2L-75 x 6, (Joint material / BT material only) L-50 x 50 x 4 (both web sides) Binding bolt (BT material only) : M16 (shear bolt) assumed, 5,5 spans (L k / 2 section) 6 locations (Bolt spacing: (end) 200mm, (middle) 300mm, 400mm) Support conditions: pin on one end, roller on the other end Displacement restraint: Out-of-plane direction of both ends of the truss and the upper and lower central nodes Applied load: 100kN downward concentrated load on the central upper node of the truss

[0076] Looking only at the analysis results, both the maximum deformation and maximum axial stress were nearly identical, and the deflection (maximum value) at the center of the truss beam, where the concentrated load is applied, was 0.415 cm for the bolt-assembled model and 0.407 cm for the welded assembly model. Since the binding bolts 7, 7, ... in the bolt-assembled model are treated as shear bolts, it is believed that the angle iron of the connecting member 6a contributes very little to the effective cross section of the assembled member. However, if the binding bolts 7, 7, ... were friction-connected with high-tensile bolts, the integrity of the assembled member would be improved, which would likely slightly increase the axial rigidity as a compression chord, and so it is estimated that the maximum deflection would be a little smaller.

[0077] A comparison of these model analyses shows that a steel truss using bolt-assembled BT material as the chord member is in no way inferior to one assembled together by welding, provided there is no localized buckling of the individual members between the joining bolts.

[0078] The assembly members in the above examples have been explained using BT materials, but in the case of H-section members, I-section members, or square cross-section members which are assembled by bolts and have a similar cross-sectional shape with flanges and webs, it is also a matter of relative comparison between the chord buckling strength of the assembled member and the local individual member buckling strength, so it goes without saying that the design method of the present invention can also be applied to assembly members of these cross-sectional shapes. [Industrial Applicability]

[0079] The present invention provides a steel truss in which the flanges and webs are assembled with bolts rather than by welding, and the chord members are made of assembled components such as BT materials. This not only eliminates the welding work and costs involved in welding assembly, including distortion correction, but also allows for flexible combinations of flange and web plate thicknesses, contributing to the supply of steel truss structures with a wide variety of member cross sections. [Explanation of symbols]

[0080] 1: Truss beam 2:Top chord material 2a: flange 2b:Web 3: Lower chord 4: Lattice material 5: Bundle material 6, 6a: Bonding material 7: Spelling Bolt L k : Buckling length of chord L1, l1: Dimensions between bolts P: Concentrated load N1, N2, N s : Compressive axial force T r : Tensile axial force

Claims

1. In designing steel frame trusses, 1) The computer input device inputs at least the following specification data: the length of the buckling section of the truss chord, the cross-sectional dimensions and bolt spacing of the plates that make up the assembly members used in the chord, and the buckling section length and cross-sectional size of other members (lattice members and beam members). 2) The specification data regarding the assembled member input in step 1) is stored in the storage device of the computer, which is used in step 5), which is a subroutine for calculating the allowable axial strength of the assembled member. 3) Using the input specification data of the assembly members and other members, the calculation unit of the computer calculates stresses in the assembly members and other members. 4) The allowable axial compressive and tensile strengths of the other members are calculated by the computing device. 5) The allowable axial compressive and tensile strengths of the assembled members are calculated by the computing device in the subroutine using the specification data on the assembled members stored in the storage device in step 2). In the subroutine procedure 5), the allowable compressive strength of the chord member buckling section when the spacing between the bolts of the assembly is assumed to be equal to or less than a predetermined dimension along the entire length, and the allowable compressive strength of the individual member buckling section, which is the section where the spacing between the bolts exceeds the predetermined dimension, are calculated, and the allowable compressive strength of the assembly member as a whole is determined by comparing the allowable compressive strengths of both. 6) The allowable axial strengths of the assembly members and other members calculated in steps 4) and 5) above are compared with the calculated stresses of the assembly members and other members by the computing device, and a test is performed to determine whether or not they are within the allowable range for the truss member size. 7) If the test results in a stress ratio σ / f≦1.0 for all members, they are deemed to be within the allowable range, and the calculation results are output by the computer's output device (step 9), and the process is completed. 8) When σ / f≦1.0 is not satisfied for all members, if the test result of the assembled member is σ / f≦1.0, the process returns to step 1), the specification data of the other members is changed, and the calculation is performed again by the calculation device using steps 1) to 7).On the other hand, if the test result of the assembled member is not σ / f≦1.0, the process returns to step 1), the specification data of the assembled member is changed, its allowable axial strength is recalculated using step 5), and the calculation is performed again using steps 1) to 7). 9) When the stress ratio σ / f of all members is 1.0 or less in the procedure of 7), the calculation results are outputted by the output device of the computer, and the procedure is completed. A method for designing a steel truss including assembly members, characterized in that the above steps are repeated by a computer.

2. 2. A design method for a steel truss including an assembly member according to claim 1, wherein step 5) is a subroutine in which the allowable compressive strength of the chord member buckling section as a chord member of the assembly member and the allowable compressive strength for the inter-bolt length of the individual member buckling section are calculated by an arithmetic unit of the computer using specification data of the assembly member stored in the storage device of the computer, by the following procedure: Assuming that the spacing between the bolts in the chord buckling section is uniform throughout the entire buckling section, the effective buckling length of the chord is calculated taking into account the slenderness ratio of the portion of the chord buckling section corresponding to the spacing between the bolts. The allowable compressive stress corresponding to this effective buckling length is multiplied by the total cross-sectional area of ​​the chord to obtain the allowable compressive strength N of the chord in the chord buckling section. cr is calculated (step 5-1). The sum of the allowable compressive strengths of the flanges and webs as individual members calculated by multiplying the cross-sectional areas of the flanges and webs by the allowable compressive stresses corresponding to the effective buckling lengths of the flanges and webs constituting the portion of the individual member buckling section corresponding to the length between the bolts is the allowable compressive strength for the length between the bolts in the individual member buckling section. P N cr (Step 5-2). The allowable compressive strength N of the chord of the chord buckling section calculated from the steps 5-1) and 5-2) above cr and the allowable compressive strength of the individual member in the individual member buckling section P N cr are compared, and N cr ≦ P N cr If so, then the N cr is the allowable compressive strength of the assembly member B N cr Then, the allowable tensile strength of the assembly member is also calculated, and these are the allowable axial strengths of compression and tension of the assembly member (step 5-3). The N cr ≦ P N cr If not, the process returns to step 1) of claim 1, and the specification data of the assembly member is changed. A method for designing a steel truss including assembly members, characterized in that the above steps are repeated.

3. In the design method of a steel truss including an assembly member according to claim 1, the allowable compressive strength N of the chord member buckling section is cr and the allowable compressive strength of the individual member buckling section P N cr After calculating the smaller of the two, {min(N cr , P N cr )} is the allowable compressive strength of the assembly member B N cr 2. The method for designing a steel truss including assembly members using a computer according to claim 1, further comprising the steps of:

4. 2. A method for designing a steel truss including assembly members according to claim 1, wherein, for the spacing between the splicing bolts of the plate materials constituting the assembly member input in step 1), the actual spacing between the splicing bolts of the individual member buckling sections, which are sections of the assembly member with spacing between the splicing bolts exceeding a predetermined dimension, are initially input by an input device of the computer in step 1), the actual spacing between the splicing bolts of the individual member buckling sections being set so that the slenderness ratio to the effective buckling length of the chord member buckling section, where the spacing between the splicing bolts set over the entire length of the assembly member is considered to be equal to or less than a predetermined dimension, is not greater.

5. 5. A steel truss designed by the design method for a steel truss including an assembly member according to any one of claims 1 to 4, wherein when an assembly member assembled by bolt assembly is used as a chord member of the steel truss, the allowable compressive strength N of the chord member buckling section of the chord member is calculated by regarding the entire length of the assembly member as being equal to or less than the predetermined dimension in the chord member that includes a section with a wider bolt spacing than a general section where the bolt spacing is equal to or less than the predetermined dimension. cr and the allowable compressive strength of the individual member buckling section of the individual member, which is the section between the bolts with a dimension exceeding the predetermined dimension. P N cr and are compared, and either of these two allowable compressive strengths is the allowable compressive strength of the assembly member. B N cr A steel truss including assembly members, characterized in that:

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