JP7171153B2 - How to reuse structures - Google Patents

Description

The present invention relates to a method for reusing a structure when the roof frame of a large-scale structure such as a large-scale exhibition hall constructed for expositions and the like and used only for a short period of time is reduced in size and reused.

Conventionally, for example, large-scale exhibition halls constructed for expositions, etc., are sometimes constructed as temporary buildings for short-term use. It was constructed.

Although there is no problem if the same building is reused, for example, in the building 1 shown in FIG. 2, when reusing as a reduced-scale building 1a, only the central frame 2a (planar dimensions A ₁ x B ₁ , beam depth D) of the roof frame 2 is left, and the other parts are left. If the frame part is omitted, even if the plane dimension ratio is A ₁ /A=B ₁ /B, the frame after reuse (central frame 2a) is similar to the original frame (roof frame 2). Therefore, since the stress distribution is completely changed, the strength of the reused member is not necessarily sufficient.

In other words, it is not always possible to reuse existing members as they are, and it is necessary to examine the strength of the members and, if the strength is insufficient, design and manufacture new members.

Prior art relating to the reuse of structures includes, for example, Patent Document 1 and Patent Document 2. In Patent Document 1, a rigid-frame structure using strong H-section steel in the span direction and a rigid-frame structure using weak H-section steel in the girder direction and earthquake-resistant studs using H-section steel as a strong shaft are combined. , discloses a method of constructing a steel-framed building structure in which three-dimensional frames of fixed dimensions are used as independent unit blocks. According to this construction method, the building can be expanded or contracted by continuing the blocks in the girder direction and the span direction.

That is, even in an existing building, the number of blocks can be reduced or increased so as to achieve a required scale. However, if the scale (building area) increases or decreases, the number of pillars will only increase or decrease proportionally. Not applicable if you try.

In Patent Document 2, as a roof frame suitable for relatively large-span roofs such as competition facilities and event facilities, a tensioned string beam whose lower chord is a tendon and a tensioned chord beam whose upper chord is a tendon are perpendicular to each other, and a bundle member is installed at the intersection. A strung string beam structure is disclosed in which a prestress is introduced into the tendon, based on forming a cross beam by interposing a . Since the joints between these members are simple pin joints, the frame can be easily assembled and dismantled, and each member can be highly reused.

The invention of Patent Document 2 belongs to the field of roof frames for large-space structures, which is the object of the present invention. Therefore, it is impossible to reduce the size of the roof frame after reuse (reduction of the string beams). Therefore, it cannot be applied to the case where the scale is reduced and reused, which is assumed by the present invention.

JP-A-2006-46023 Patent No. 3918715

When the roof structure of a large-scale structure such as a large-scale exhibition hall constructed for an exposition or the like and used only for a short period of time is reduced in size and reused, the present invention can be applied to almost all types of structures without changing the size. To provide a method for reusing a structure capable of reusing existing members.

The means of the present invention for solving the above-mentioned problems is, in the case of reusing the frame of a structure such as an exhibition hall, the shape and dimensions of the frame after scale reduction are similar to the original frame, and the original frame is constructed. One end or a part of both ends of the member before scale reduction is cut off so that the internode length of each member after scale reduction is a length that matches the ratio of the similar shape. It is a reuse method of the structure.

In addition, when reusing the roof frame of a structure such as an exhibition hall, if the shape and dimensions of the roof frame after scale reduction are similar to the original roof frame, and after scale reduction of each member that constitutes the original roof frame One end or a part of both ends of the member before scale reduction is cut off so that the length between the nodes of the structure matches the ratio of the similar shape. The method.

Further, the present invention provides, for example, a frame of a structure in which the roof frame is a multi-layer or single-layer truss structure and includes members twisted around an axis, wherein the length between nodes of the member is the above-mentioned One end or part of both ends of the twisted member before scale reduction is cut off so that the length matches the ratio of the similar shape, and the shape of the roof frame after scale reduction is adjusted. A method of reusing said structure, characterized in that said twisted member after being scaled down is subjected to additional twisting about its axis so as to achieve a twisting angle.

Since the present invention is the means described above, when reusing the roof frame of a structure such as an exhibition hall, if the shape and dimensions of the frame after scale reduction are similar to the original frame, the frame can be reused. All of the constituent members are shortened according to the similarity ratio, but the stiffness ratio of each member remains the same, so even if the stress value changes, the stress distribution state does not change. Moreover, since the load effect acting on the frame is reduced due to the scale reduction, the stress value is reduced, and the strength of these members is increased from that of the original frame. That is, since the same member can be reused simply by shortening the member length (that is, the member cross-sectional size remains the same), there is no need to redesign and manufacture the member.

As for the joints of the nodes where the members are connected to each other, if the original joint method is bolt joints, the cut ends of the members are made bolt holes so that they fit the nodal joint members of the nodes. If processed, it can be reused as it is.

但し、ｗ：鉛直等分布荷重、L：梁の長さ（支点間寸法）
Ｅ：ヤング係数、I：梁の断面二次モーメント The relationship between member dimensions (length, cross section) and stress and deformation will be explained. For example, as a very simple example (see FIGS. 7(a) and (b)), the maximum bending moment M and the maximum deflection δ is given by the following equation.

However, w: vertical uniform load, L: length of beam (dimension between fulcrums)
E: Young's modulus, I: Area moment of inertia of beam

As can be seen from the above (Formula 1) and (Formula 2), the bending moment M acting on the member (simple beam G) is proportional to the square of the length L, and the deflection δ is proportional to the fourth power of the length L. .

Here, assuming that the simple beam G is a trussed beam T (see FIG. ₈ ) having the following cross _- sectional performance, the bending strength M1 and the deflection _δ1 of the trussed beam T1 after being similarly reduced are: State the impact.

但し、Ｆ：材料強度

（トラス梁Ｔ₁）
相似比率をα（＜1.0）として（式３）、（式４）のｊ、Lをαｊ、αLに置換えて、断面係数Ｚ₁＝（a・ｊ）・α、 断面二次モーメントＩ₁＝（a・ｊ²/2）・α²

(truss beam T)
Section modulus Z=a・j, Sectional moment of inertia I=a・j ² /2
However, a: the cross-sectional area of one side of the chord (same for upper and lower chords)
j: Dimension between center of gravity of upper and lower chord members

However, F: material strength

(truss beam _T1 )
With the ratio of similarity α (<1.0) and replacing j and L in (Equation 3) and (Equation 4) with αj and αL, the section modulus Z ₁ = (a j) · α and the moment of inertia I ₁ = (a・^j2 / ² )・α2

As can be seen from the comparison of (Equation 3) and (Equation 4) with (Equation 5) and (Equation 6), (Equation 3) and (Equation 4) and (Equation 5) and (Equation 6) are: Equations 5) and (6) are the same except that the similarity _ratio α and the square of the similarity ratio α are multiplied, respectively. ₀ is reduced by a factor of α and the original moment of inertia I, ie the deflection δ ₀ , is reduced by a factor of α ² .

On the other hand, if the member (truss girder) length L is multiplied by α, the bending moment M will decrease in proportion to the square of the length L as described above, resulting in a ^double α. If the shape and dimensions are similar to the original after scale reduction, and the length L of the truss beam and the dimension j between the centers of gravity of the upper and lower chord members are 50% (= α), the bending strength will be α times. Since the acting bending moment M is decreased by a factor of α ² , the margin of bending strength of the truss beam after scale reduction is α/α ² =2.0 times. Also, the deflection is greatly improved to α ² =0.25 times.

The above was the case of a simple beam, but as a more complicated case, for example, a cylindrical three-dimensional truss frame as shown in Fig. 9 is made similar to the side lengths A and B and the beam length D while keeping the member cross-sectional size as it is. 2/3 in 2012, and the reduced frame as shown in Fig. 13 is used for verification. The symbols and design conditions in these figures are as follows.

(Common) △ mark: fulcrum, arrow: fulcrum movable direction and (partially) H-294x200x8x12, lattice material: φ-139x4.5 and (only near the fulcrum) φ-165.2x5 or φ-190.7x5.3, fixed load (vertically uniform distribution): 1907N/m ²

(Figs. 13 to 16: reduced frame) Span A ₁ × girder B ₁ : 40m × 40m, truss length d: 2m, upper and lower chords: H-300x150x6.5x9 and (partially) H-294x200x8x12, lattice material : φ-139×4.5 and (near the fulcrum only) φ-165.2×5 or φ-190.7×5.3, fixed load: 2293 N/m ²
Since the reduced frame has a similar shape to the original frame, naturally the arrangement of each member is also the same.

但し、C₁、C_2、C₂ ^’：係数（無次元）、p₀：鉛直等分布の単位荷重（kN/m²）、
L：辺長（ｍ）、E：ヤング係数（kN/m²）、ｔ：版厚（ｍ）、
I：版の断面二次モーメント（ｍ⁴/ｍ）
即ち、最大曲げモーメントは長さの２乗に比例し、最大たわみは長さの４乗に比例しかつ版の断面二次モーメントに反比例する。 Here, the relationship between the stress/deformation and the frame size in the plate-shaped frame as described above will be described by analogy with a square plate of a continuous body such as a concrete slab. It is known that the maximum bending moment M _s and the maximum deflection δ _s in the case of four-sided simple support (same as the fulcrum condition of the space truss frame) occur at the center of the slab and are given by the following equations.

However, C ₁ , C _{2 ,} C ₂ ^' : Coefficient (dimensionless), p ₀ : Unit load of vertical uniform distribution (kN/m ² ),
L: side length (m), E: Young's modulus (kN/m ² ), t: plate thickness (m),
I: Plate moment of inertia (m ⁴ /m)
That is, the maximum bending moment is proportional to the square of the length, the maximum deflection is proportional to the fourth power of the length and inversely proportional to the area moment of inertia of the plate.

但し、ｓ：１台のトラス梁の支配幅（ｍ）
となる。 Since the above formula is for a continuum, if it is applied to the space truss frame as described above, which is not a continuum, the geometrical moment of inertia I ₁ of one truss girder is a·j ² /2 as described above. Considering that the area moment of inertia I in (Equation 8) is a value per unit width of the slab, I can be set as I=I ₁ /s, where s is the governing width of one truss girder. Therefore, (Formula 8) is

However, s: Controlled width of one truss beam (m)
becomes.

最大たわみは、（式９）のL、ｊ、ｓをそれぞれαL、αｊ、αｓと置いて、

となる。 Next, when the length is similarly reduced by α times, it becomes as follows.
The maximum bending moment is given by putting L in (Formula 7) as αL,

The maximum deflection is given by putting L, j, and s in (Formula 9) as αL, αj, and αs, respectively.

becomes.

As can be seen from the comparison of (Equation 7) and (Equation 9) with (Equation 10) and (Equation 11), (Equation 7) and (Equation 9) and (Equation 10) and (Equation 11) are: 10) and (Equation 11) are the same except that the square of the similarity ratio α and the cube of the similarity ratio α are multiplied, so the reduced frame with the similarity ratio α has the maximum bending moment is ^doubled as α, and the maximum deflection is ^tripled as α.

Since α=2/3 in the space truss frame of the example, the maximum bending moment is (2/3) ² =0.444 times and the maximum deflection is (2/3) ³ =0.296 times. However, as can be seen from (Equation 10) and (Equation 11), these are proportional to the vertically uniformly distributed load p ₀ per unit area, so correction is required when the vertically uniformly distributed load p ₀ changes.

As an example, the results of three-dimensional stress analysis under fixed (vertical) load in the cylindrical space truss frame of FIGS. 9 and 13 are shown in FIGS. 10 to 12 and FIGS. 14 to 16, respectively. 10 and 14 show the upper chord member, FIGS. 11 and 15 show the lower chord member, and FIGS. 12 and 16 show the axial force of the lattice member. The wider the line width, the greater the axial force. Force, unhatched is tensile force. The large numbers shown in each figure are the maximum tension and compression axial force values (kN).

The maximum value of the axial force in the frame of Fig. 9, which is the original frame, is Fig. 10 upper chord member (tensile 272.0 kN, compression 730.9 kN), Fig. 11 lower chord member (tensile 444.9 kN, compression 490.5 kN), Fig. 12 lattice member ( 185.5 kN in tension and 223.6 kN in compression). On the other hand, in the frame of Fig. 13 after reduction, Fig. 14 upper chord member (tensile 140.4 kN, compression 381.5 kN), Fig. 15 lower chord member (tensile 235.4 kN, compression 259.1 kN), Fig. 16 lattice member (tensile 95.9 kN, compression 117.1 kN) kN).

Comparing FIGS. 10-12 with FIGS. 14-16, it can be seen that the respective maximum axial force generating members are at the same position, and the tensile and compression maximum axial force values of FIGS. 10 and 14 upper chord material (tensile 0.517, compression 0.522), figures 11 and 15 lower chord (tensile 0.529, compression 0.528), and figures 12 and 16 lattice material (tensile 0.517, compression 0.524). It has become.

Let us compare the above results with the results estimated from (Equation 10) and (Equation 11). Since the chord axial force N of the truss beam has the relationship of N = M / truss thickness (D = 3m, d = 2m), the relationship of (Equation 10) and (Equation 11) can be directly applied to the chord axial force also fits.

Therefore, here, comparison with the chord material axial force of the analysis result will be made. 13 to 16 with respect to the original frame in FIGS. 9 to 12 is 2/3, the chord axial force is α ² =(2/3) ^twice from (Equation 10). be. However, since the cross-sectional size of the truss member remains the same, the ratio of the weight per unit area w of the reduced frame in Fig. 13 to the original frame in Fig. 9 is 2239/1907 = 1.20 times, which is corrected. Then, the equivalent magnification β of the chord axial force is β=(2/3) ² x1.2=0.533 times.

14 to 16 with respect to FIGS. 10 to 12 of the member axial force maximum value according to the analysis result is, as described above, 0.52 to 0.53 times, so it is in good agreement with β. That is, even in the case of a space truss frame as shown in FIG. 9, according to the method of reducing the frame in a similar manner, the stress distribution state remains almost unchanged and the absolute value of the stress decreases according to the similarity ratio. The yield strength of each member uniformly increases compared to the original frame.

As for the deformation analysis results (not shown), the maximum deflection occurred at the central node, 9.8 cm for the original frame in FIG. 9 and 3.4 cm for the reduced frame in FIG. 3.4/9.8=0.347. On the other hand, if α ³ in (Formula 11) is corrected by the ratio of weight w per unit area (= 1.2), the equivalent magnification β of the maximum deflection is β = (2/3) ³ x 1.2 = 0.356 times So they are almost identical.

From the above, when the roof frame of the structure is similarly reduced and reused, there is no damage even if the same member is reused simply by shortening the member length (i.e., keeping the member cross-sectional size unchanged). As long as there is no structural problem with stress and deformation.

In the roof structure of large-scale exhibition halls, etc., the bending moment, which has the greatest effect on the magnitude of the stress generated in the members that make up the roof structure, is generated mainly by vertical loads. The effect as described above can be most expected in the roof structure of the large-scale exhibition hall.

Since the present invention is based on the means described above, the following effects are obtained. According to the method of reusing the roof frame of structures such as exhibition halls so that the shape and dimensions of the frame after scale reduction are similar to the original roof frame,
(1) The strength of the members that make up the roof structure after scale reduction will have more margin than when the original roof structure was used. Therefore, almost all of the same members can be reused while keeping the member cross-sectional size unchanged.

(2) Therefore, there is no need to redesign and manufacture members.
(3) By shortening the original roof frame members, almost all the members can be reused as they are, which greatly contributes to the effective use of resources.

An example of the original roof structure made up of a truss structure is shown, (a) is a plan view of the roof structure, and (b) is a cross-sectional view of (a) taken along line I-I. Fig. 1 shows an example of a case where the scale is reduced while leaving the central part of the roof frame. be. 1 is a first embodiment of the present invention, (a) is a roof frame plan after the roof frame of FIG. be. FIG. 3 shows a second embodiment of the present invention, in which the roof is cylindrical and the roof frame is scaled down in the same manner as in FIG. (The roof structure plan is omitted). FIG. 4 is a diagram explaining a method of reducing the shape and dimensions of a truss to a similar shape in an embodiment of the present invention, where (a) shows the original truss and (b) shows the truss after reduction. FIG. 4 is an enlarged plan view of the P portion near the ridge portion of the roof frame 2c (corresponding to the P portion in FIG. 3(a)), showing the positional relationship between the upper chord member 10 and the lower chord member 11 of the truss near the ridge portion. It is a figure explaining. Figures (a) and (b) are diagrams explaining the effects of the member dimension L on the bending moment M and the deflection δ, respectively, using a simple beam G as an example. It is a figure which shows the shape dimension at the time of making the simple beam G of FIG. 7 into the truss beam T. FIG. It is an example of a space truss frame, and shows a frame drawing. FIG. 9 shows a three-dimensional stress analysis result of the space truss frame shown in FIG. 9 under a fixed (vertical) load, showing an axial force diagram of the upper chord member. FIG. 9 shows a three-dimensional stress analysis result of the space truss frame shown in FIG. 9 under fixed (vertical) load, showing an axial force diagram of the lower chord member. FIG. 9 shows a three-dimensional stress analysis result of the space truss frame shown in FIG. 9 under a fixed (vertical) load, showing an axial force diagram of a lattice material. It is a case where the space truss frame of FIG. 9 is similarly reduced to 2/3, and shows the space truss frame structure after reduction. FIG. 13 shows a three-dimensional stress analysis result of the space truss frame shown in FIG. 13 under a fixed (vertical) load, showing an axial force diagram of the upper chord member. FIG. 13 shows a three-dimensional stress analysis result of the space truss frame shown in FIG. 13 under a fixed (vertical) load, showing an axial force diagram of the lower chord member. FIG. 13 shows a three-dimensional stress analysis result when the space truss frame shown in FIG. 13 is subjected to a fixed (vertical) load, showing an axial force diagram of a lattice material. Fig. (a) is a perspective view of the prototype, and Fig. (b) is a perspective view of a structure that has been reused by reducing the size of the original structure. be. Figures (a) to (d) are diagrams for explaining how to reduce the size of a unit frame of a ball-joint type space truss in a manner similar to the prototype.

A first embodiment of the present invention will be described with reference to FIGS. 3 to 5. FIG. FIG. 3 shows a case where the roof frame 2 of the original building 1 shown in FIG. 1 is similarly scaled down to become the roof frame 2b of the building 1a. The shape of the roof is a flat plate, and the roof frame 2b has a shape similar to that of the roof frame 2. As shown in FIG. Since the roof structure dimension ratio A ₁ /A (=B ₁ /B) and the truss structure dimension ratio d/D are the same, the lengths of all the members of the roof structure 2b are shortened according to the similarity ratio.

FIG. 4 is a cross-sectional view of the roof frame 2c (corresponding to the cross-sectional arrows of FIG. 3) after the roof frame 2c is scaled down in the same manner as in FIG. 3, in the case where the roof shape is cylindrical.

A method of shortening each member 10, 11, 12, 13 after contraction will be described. As shown in FIG. 5, _one end or part of both ends of each original member 10, 11, 12, 13 (hatched line in FIG. 5(a) part) is cut off and reassembled into a truss of similar shape and size as shown in Fig. 5(b).

A new bolt hole (not shown) for joining to each nodal joint J is opened at the cut-side end of each member 10, 11, 12, 13 after reduction. At this time, each nodal joint J, J, . . . is reused as it is. This point needs to be taken into consideration when determining the dimensions of the top chord member 10 after reduction.

Further, since the shape and dimensions of the truss after reduction are similar to those of the original truss, the inclination angle θ of the lattice member 12 is the same.

As described above, the present invention is a method in which the roof frame 2 is reduced to a similar shape and reused. It becomes possible to reuse the members of

FIG. 6 is a partial truss profile and cross-sectional axis of the truss structure roof structure according to the second embodiment of the present invention when the upper and lower chords are not parallel (twisted positional relationship). It is a composition diagram. It corresponds to the part P (near the ridge) in FIG. 3(a) and FIG.

A multi-layer truss structure in which the upper and lower chord members are not parallel is known, for example, from Japanese Patent No. 6450707, and is characterized in that the upper and lower chord members are each twisted around the member axis. is. There are also single-ply truss structures, which are not multi-ply but consist of members twisted about member axes, as known for example from Japanese Patent No. 3,418,660.

A second embodiment of the present invention is for a multi-layer truss structure or a single-layer truss structure roof structure having members (chords) twisted about the member axes.

In a multi-layered (or single-layered) truss structure roof structure with a cylindrical roof shape or two-way curvature, as shown in Fig. 6, the upper and lower chord members are not parallel (in the case of a multi-layer truss), and they A member may be constructed twisted about an axis.

One or both ends of each member of the truss is cut and shortened so as to reduce the shape and dimensions of the original roof frame to a similar shape. is twisted around its axis, if its length is shortened, even if the twist angle per unit length is the same, the twist angle at the end of the member will be smaller than when the length of the member is original. As shown in 5(b), when jointed with the nodal joint J that is reused as it is, the joint surfaces of the two do not match, resulting in a skin gap.

In order to avoid this, it is necessary to add an additional twist to the chord member 10 or 11 around the axis so that the twist angle of the member ends matches the geometry of the roof structure after scaling.

As described above, in the second embodiment, one end or one of both ends of the members 10, 11, 12, and 13 before scale reduction is adjusted so that the length between the nodes of the members is adjusted to the ratio of similar shapes. The parts are cut and drilled, and the shortened chord members 10 or 11 are rotated around the axis so that the twist angle of the member ends matches the shape of the roof structure after scale reduction. A method for reusing a structure, characterized by adding an additional twist to the

FIGS. 17 and 18 show a third embodiment of the present invention, in which a roof structure (a circular dome is exemplified) composed of a ball-joint type three-dimensional truss in which a steel pipe member is joined to a steel ball at a node with a single bolt. ) is similarly reduced in scale and reused.

As shown in Figs. 18(a) to 18(d), the roof structure of this space truss is mainly an assembly of quadrangular pyramids composed of eight steel pipe members. When reusing, as shown in the figure, each member is cut so that the length between nodes matches the ratio of similar shapes, and an end metal fitting with a screw hole is attached to the end of the member on the cut side. are welded anew and each steel pipe is reassembled using new bolts screwed into the threaded holes in the end fittings and the threaded holes in the original steel balls.

Therefore, the materials discarded for reuse are only the removed parts of the member and the removed bolts, and the new members are only the newly welded end fittings and bolts. Since the member size and bolt size remain the same, the steel balls can be reused as they are.

So far, we have discussed the reuse method to similarly reduce the size of the roof frame, but these are not limited to the roof frame. The same is true when the scale is reduced to a smaller size and reused.

That is, the shape and dimensions of the frame after scale reduction are similar to the original frame, and the length between the nodes of the members that make up the original frame after scale reduction is a length that matches the proportion of the similar shape. According to the method in which one end or part of both ends of the member before scale reduction is cut away, the stress distribution state remains almost unchanged, and the absolute value of the stress decreases according to the similarity ratio. The proof stress of each member uniformly increases compared to the original frame, and the maximum deformation is greatly reduced according to the similarity ratio. It is also clear from Thus, the invention is not limited to roof structures.

The present invention is a reuse method that enables the reuse of almost all existing members, particularly in cases where large temporary structures constructed for expositions and the like that are used only for a short period of time are reused after being reduced in scale. , contributes greatly to the effective use of resources.

1: Original building 1a: Building after scale reduction 2: Original roof structure 2a, 2b, 2c: Roof structure after scale reduction 10: Upper chord material 11: Lower chord material 12: Lattice material 13: Bundle material A, A ₁ , B, B ₁ : Roof frame dimensions D, d: Truss construction dimensions G: Beam L: Member (beam) length (distance between fulcrums of beams)
M: Bending moment δ: Deflection S: Dimension between _top chord nodes of truss in original roof frame S1: Dimension between top chord nodes of truss in roof frame after scale reduction e: Dimension from truss node to edge of node joint θ : Inclination angle of lattice material

Claims (3)

In the case of reusing the framework of a structure, the shape and dimensions of the framework after scale reduction are similar to the original framework, and the length between nodes of each member that constitutes the original framework after scale reduction is similar to the similarity. A method for reusing a structure, wherein one end or a part of both ends of each of the members before being scaled down is cut off so as to have a length that matches the ratio of the shape. In the case of reusing the roof frame of a structure, the shape and dimensions of the roof frame after scale reduction are similar to the original roof frame, and the length between nodes after scale reduction of each member that constitutes the original roof frame is a method of reusing a structure, wherein one end or a part of both ends of each of the members before size reduction is cut off so as to have a length corresponding to the ratio of the similar shapes. In the framework of a structure including members twisted around the axis, the length between nodes of the twisted members is adjusted to the ratio of the similarity before scale reduction. One end or part of both ends of the twisted member is removed, and the twisted member after scale reduction is cut so as to have a twist angle that matches the shape of the frame of the structure after scale reduction. 3. A method for reusing a structure according to claim 1 or 2, characterized in that additional twisting is applied around its axis.

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