JPWO2020045119A1 - Hat shaped steel sheet pile - Google Patents

Abstract

The hat-shaped steel sheet pile extends from both ends of the web in the width direction to both sides in the width direction and has a flange angle θ between the web extending in the width direction and the flange angle θ in the width direction in a cross section orthogonal to the longitudinal direction. A pair of flanges, a pair of arms extending from each end of the pair of flanges along the width direction and toward both sides in the width direction, and a pair of flanges of each pair of arms. Includes a pair of fitting joints formed at the opposite ends. The ratio of the total length of the web, the pair of flanges, and the pair of arms in the cross section to the average plate thickness of the web, the pair of flanges, and the pair of arms is 120 or more. The effective width B, effective height h, and flange angle θ in the cross section are constants C (1.01 ≦ C ≦ 1.13) in the range where the flange plate thickness ratio to the web is 0.6 or more and 1.0 or less. The condition of the following equation (i) using the above is satisfied, and the relationship of effective width B, web length Bw in cross section, cross section height H and flange angle θ satisfies the relationship of B-Bw-2H / tan θ> 0.

Description

The present invention relates to a hat-shaped steel sheet pile.

Hat-shaped steel sheet piles are widely used in civil engineering and construction work for placing them in the ground to construct walls for retaining soil and stopping water. Therefore, the bending performance of the wall body has been emphasized conventionally. Further, in order to improve economic efficiency, that is, to reduce the weight of the wall body, the cross section of the hat-shaped steel sheet pile tends to be widened and thinned.

On the other hand, as the performance and economy of the hat-shaped steel sheet pile have improved, the peripheral technology of the hat-shaped steel sheet pile has been developed, and the range of application and applications have expanded. An example of peripheral technology development is the increase in size of heavy construction equipment. The purpose of increasing the size of heavy construction equipment is, for example, to enable construction in a harder stratum or a deeper stratum, and to improve construction efficiency. When the construction heavy equipment becomes large in this way, not only bending stress is applied to the hat-shaped steel sheet pile after casting, but also a large axial force acts during construction.

In addition, the scope of application of hat-shaped steel sheet piles has been expanded. Specifically, for example, in addition to the conventional wall body, a hat-shaped steel sheet pile is often used as a foundation. For example, Patent Document 1 describes a technique for using a steel sheet pile as a basic structure. Patent Document 2 describes a technique for improving the bearing capacity by providing a closing portion only at the tip of the hat-shaped steel sheet pile in order to improve the performance when the hat-shaped steel sheet pile is used as a base. As described above, when the hat-shaped steel sheet pile is used as a foundation to bear the bearing capacity, it is required to improve the performance of the hat-shaped steel sheet pile as an axial force member.

Here, in general, it is necessary to consider buckling in the axial force member. In particular, in a cross section made of a thin-walled plate material such as a hat-shaped steel sheet pile, it is necessary to pay sufficient attention to local buckling even in buckling. From this point of view, Patent Document 3 proposes a technique of forming a bent-formed portion at a corner portion in a cross section of a hat-shaped steel sheet pile to improve buckling resistance. Considering that the cross section of the hat-shaped steel sheet pile tends to be wider and thinner as described above, it is considered that it will be necessary to improve the buckling resistance of the hat-shaped steel sheet pile against the axial force in the future.

Japanese Patent No. 3832845 Japanese Patent No. 4916932 Japanese Patent No. 4088041

However, although the technique described in Patent Document 3 is efficient when the hat-shaped steel sheet pile is viewed as an axial force member, it leads to a reduction in the amount of steel material in the web portion. There is a possibility that the bending performance of the wall body, which is the performance originally expected for the sheet pile, will be reduced. In addition, since the cross-sectional shape becomes complicated, a very advanced technique is required in the rolling manufacturing process, and it is difficult to improve the manufacturing efficiency. Considering these points, it is desirable to improve the buckling resistance to the axial force while maintaining the basic cross-sectional shape of the hat-shaped steel sheet pile such as the web, the flange, and the arm.

Therefore, an object of the present invention is to provide a new and improved hat-shaped steel sheet pile capable of improving the buckling resistance against an axial force while maintaining the basic cross-sectional shape of the hat-shaped steel sheet pile. And.

According to one aspect of the present invention, the hat-shaped steel sheet pile is formed from a web extending along the width direction on the first side in the cross-sectional height direction and from both ends in the width direction of the web in a cross section orthogonal to the longitudinal direction. A pair of flanges extending toward the second side in the cross-sectional height direction on both sides in the width direction and forming a flange angle θ with the width direction, and a pair of flanges on the second side in the cross-sectional height direction. A pair of arms extending from each end of the flange along the width direction and toward both sides in the width direction and a pair of arms formed at the end opposite to each pair of flanges. It includes a pair of fitting joints. The ratio of the total length of the web, the pair of flanges, and the pair of arms in the cross section to the average plate thickness of the web, the pair of flanges, and the pair of arms is 120 or more, and the effective width B and the pair of arms in the cross section. The effective height h and the flange angle θ are the following equations using the constant C (1.01 ≦ C ≦ 1.13) in the range where the plate thickness ratio of the flange to the web is 0.6 or more and 1.0 or less. The condition (i) is satisfied, and the relationship between the effective width B, the web length Bw in the cross section, the cross section height H, and the flange angle θ satisfies the relationship of B-Bw-2H / tanθ> 0.

According to another aspect of the present invention, the hat-shaped steel sheet pile has a web extending along the width direction on the first side in the cross-sectional height direction and both ends in the width direction of the web in a cross section orthogonal to the longitudinal direction. A pair of flanges extending from both sides in the width direction and toward the second side in the cross-sectional height direction and forming a flange angle θ with the width direction, and a pair on the second side in the cross-sectional height direction. A pair of arms extending along the width direction from each end of the flange and toward both sides in the width direction, and a pair of arms formed on the opposite end of each pair of flanges. It is provided with a pair of fitting joints. The ratio of the total length of the web, the pair of flanges, and the pair of arms in the cross section to the average plate thickness of the web, the pair of flanges, and the pair of arms is 120 or more. The effective width B, effective height h, and flange angle θ in the cross section are constants C (1.03 ≦ C ≦ 1.13) in the range where the flange plate thickness ratio to the web is 0.7 or more and 1.0 or less. The condition of the following equation (i) using the above is satisfied, and the relationship of effective width B, web length Bw in cross section, cross section height H and flange angle θ satisfies the relationship of B-Bw-2H / tan θ> 0.

According to the above configuration, the buckling resistance to the axial force can be improved while maintaining the basic cross-sectional shape of the hat-shaped steel sheet pile.

It is sectional drawing of the hat-shaped steel sheet pile which concerns on one Embodiment of this invention. It is a graph which shows the relationship between the conversion width-thickness ratio and the web width-thickness ratio in the conventional steel sheet pile product. It is a figure which shows schematic the cross-sectional shape of the hat-shaped steel sheet pile in the first study example. It is a graph which shows the result of the buckling proof stress analysis in the first examination example. It is a graph which shows the local buckling yield strength based on the result shown in FIG. It is a graph which shows the local buckling proof stress based on the result of the buckling proof stress analysis in the 2nd study example. It is a graph which shows the relationship between the flange angle and the aspect ratio in the 3rd study example. It is a graph which shows the relationship between the flange angle and the aspect ratio in the 4th study example together with a part of the 3rd study example. It is a graph which shows the relationship between the flange angle and the aspect ratio in the 3rd and 4th study examples together with the approximate curve of the correlation for each plate thickness ratio. It is a graph which shows the relationship between the flange angle and the aspect ratio in the 3rd and 4th study examples together with the approximate curve of the correlation for each plate thickness ratio.

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the present specification and the drawings, components having substantially the same functional configuration are designated by the same reference numerals, so that duplicate description will be omitted.

FIG. 1 is a cross-sectional view of a hat-shaped steel sheet pile according to an embodiment of the present invention. As shown in FIG. 1, the hat-shaped steel sheet pile 1 has a cross section orthogonal to the longitudinal direction (z direction in the figure) on the first side in the cross-sectional height direction (the back side in the y direction in the figure). Web 2 extending along the width direction (x direction in the figure), both sides in the width direction from both ends in the width direction of the web 2, and the second side in the cross-sectional height direction (front side in the y direction in the figure). ), And flanges 3A and 3B forming a flange angle θ (sharp angle side) with the width direction, and flanges 3A and 3B on the second side in the cross-sectional height direction in the width direction from their respective ends. Includes arms 4A, 4B extending along and to both sides in the width direction, and fitting joints 5A, 5B formed at the ends of the arms 4A, 4B opposite the flanges 3A, 3B, respectively.

Here, in FIG. 1, the dimensions of each part of the hat-shaped steel sheet pile 1, specifically, the length Bw and the plate thickness tw of the web 2, and the length Bf and the plate thickness tf of the flanges 3A and 3B are shown. The length Ba and the plate thickness ta of the arms 4A and 4B are shown. Here, the length Bw is the distance between the plate thickness center line of the web 2 and the two intersections formed between the plate thickness center lines of the flanges 3A and 3B, respectively. Similarly, the length Bf is the distance between the thickness centerline of the flange 3A and the two intersections formed between the respective thickness centerlines of the web 2 and the arm 4A. The length Ba is the distance between the intersections formed between the thickness center line of the thickness center line and the flange 3A of the arms 4A, a fitting center E _A fitting joint 5A. Since the cross-sectional shape of the hat-shaped steel sheet pile 1 is symmetrical with respect to the neutral axis in the width direction (y-axis in the drawing), the flange 3B has the same length Bf as the flange 3A, and the arm 4B also has the arm 4A. The length is Ba as in the case of.

Further, FIG. 1 shows the effective width B, the cross-sectional height H, and the effective height h of the hat-shaped steel sheet pile 1. Here, the effective width B is the distance between the mating fitting 5A, each of the mating centers _E A of 5B, _{E B.} The cross-sectional height H is the cross-sectional height of the hat-shaped steel sheet pile 1 including the thickness of the web 2 and the arms 4A and 4B and not including the overhang of the fitting joints 5A and 5B, and the effective height h is the cross-sectional height. H = H- (tw / 2 + ta / 2), which is obtained by subtracting half of the plate thicknesses of the web 2 and the arms 4A and 4B from H. When the shape of the hat-shaped steel sheet pile 1 shown in FIG. 1 is geometrically established, the total width B, the web length Bw, the cross-sectional height H, and the flange angle θ are B-Bw-2H / tanθ> 0. Meet the relationship.

Here, for the hat-shaped steel sheet pile 1 according to the present embodiment, the ratio B _TTL / t _AVE to the average plate thickness t _{AVE of the total length B TTL} is defined as the “converted width-thickness ratio”. As will be described later, in the hat-shaped steel sheet pile 1, the converted width-thickness ratio B _TTL / t _AVE is 120 or more, and the effective width B and the effective height h in the cross section and the flange angle θ satisfy a predetermined relationship. Here, the total length B _TTL is the total length of the web 2, the flanges 3A, 3B, and the arms 4A, 4B, and is calculated by the following equation (1). The average plate thickness t _AVE is the average plate thickness of the web 2, the flanges 3A and 3B, and the arms 4A and 4B, and is calculated by the following formula (2).

FIG. 2 is a graph showing the relationship between the converted width-thickness ratio and the web width-thickness ratio (Bw / tw) in the conventional steel sheet pile product. The present inventors have studied a method for improving the buckling resistance against axial force while maintaining the basic cross-sectional shape of the hat-shaped steel sheet pile. Since the cross section of the sheet pile becomes more apparent in the tendency of widening and thinning, the hat-shaped steel sheet pile that is wider or thinner than the currently known hat-shaped steel sheet pile should be considered. Is rational. Here, as shown in FIG. 2, steel sheet piles having a converted width-thickness ratio of 120 or more have not been industrially realized not only in hat-shaped steel sheet piles but also in U-shaped steel sheet piles. The study targets hat-shaped steel sheet piles with a converted width-thickness ratio of 120 or more, which are wider or thinner than conventional steel sheet pile products.

In the study, buckling strength analysis (proprietary value analysis based on elasticity theory) was performed for hat-shaped steel sheet piles with a converted width-thickness ratio of 120 or more in various cross-sectional shapes with varying effective width, cross-sectional height, and plate thickness. After identifying the local buckling mode, the relationship between the buckling strength of the hat-shaped steel sheet pile and the representative elements of the cross-sectional shape was analyzed. As a result, the discoveries described below were made.

(First study example)
First, the effective width B of the hat-shaped steel sheet pile 1 was set to 1350 mm, and the plate thickness was set to 9.0 mm for each of the web plate thickness tw, the flange plate thickness tf, and the arm plate thickness ta. Under this condition, the moment of inertia of area per 1 m of wall width of the steel sheet pile wall in which a plurality of hat-shaped steel sheet piles 1 are fitted to each other by fitting joints 5A and 5B and joined in the width direction is about 10,000 cm. ^A plurality of cross-sectional shapes of 4 / m were set. Table 1 shows the effective height h (mm) and the flange angle θ (degrees) of the set cross-sectional shapes, and FIG. 3 schematically shows each cross-sectional shape.

Here, as shown in Table 1 and FIG. 3, when the magnitude of the moment of inertia of area per 1 m of the wall width is maintained, the effective height h increases as the flange angle θ decreases. This is because it is necessary to compensate for the decrease in the moment of inertia of area due to the decrease in the flange angle θ by increasing the effective height h.

FIG. 4 is a graph showing the results of buckling proof stress analysis in the first study example. In FIG. 4, the horizontal axis shows the length (longitudinal dimension) of the hat-shaped steel sheet pile, and the vertical axis shows the buckling resistance (elastic analysis result) of the hat-shaped steel sheet pile. In the graph of FIG. 4, it is observed that the local buckling mode occurs at the position indicated by the arrow (1) and the proof stress decreases. In this study, the proof stress in this local buckling mode (local buckling proof stress) was treated as a result, and the local buckling proof stress in each cross-sectional shape was compared. The arrows (2) in the graph of FIG. 4 are, in order from the top, Example 1 (θ = 70 °), Example 2 (θ = 60 °), ..., Example 9 (θ) at the intersections of the arrows. = 29 °) means that the result is shown.

FIG. 5 is a graph showing the local buckling yield strength based on the result shown in FIG. In FIG. 5, the horizontal axis shows the flange angle θ of each cross-sectional shape, and the vertical axis shows the local buckling proof stress. In the graph of FIG. 5, it is observed that the local buckling yield strength increases rapidly from a small value to a large flange angle θ, but shows a maximum value at a certain angle and then gradually decreases as the flange angle θ increases. Will be done. In the case of the example shown in FIG. 5, the optimum flange angle θ at which the local buckling proof stress is considered to show a maximum value is 33.5 °. From these results, the flange angle θ greatly contributes to the suppression of out-of-plane deformation due to local buckling of each part (web 2, flanges 3A, 3B and arms 4A, 4B) of the hat-shaped steel sheet pile 1. it is conceivable that. That is, according to the above result, in the cross-sectional design of the hat-shaped steel sheet pile 1, the flange angle θ is appropriately determined, and the effective height h is further determined according to the relationship between the flange angle θ and the moment of inertia of area. Therefore, the optimum solution that maximizes the local buckling resistance is obtained.

(Second study example)
Next, the effective width B of the hat-shaped steel sheet pile 1 remained 1350 mm, the web plate thickness tw and the arm plate thickness ta were set to 10.0 mm, and the flange plate thickness was set to tf8.0 mm. Under these conditions, a plurality of cross-sectional shapes were set in which the moment of inertia of area per 1 m of the wall width of the steel sheet pile wall was about 10,000 cm ^{4 / m.} Table 2 shows the effective height h (mm) and the flange angle θ (deg) of the set cross-sectional shape.

FIG. 6 is a graph showing the local buckling proof stress based on the result of the buckling proof stress analysis in the second study example. In the graph of FIG. 6, as in FIG. 5, it is observed that the local buckling proof stress changes with a maximum value with respect to the flange angle θ. In the case of the example shown in FIG. 6, the optimum flange angle θ at which the local buckling proof stress is considered to show a maximum value is 35.7 °. According to the results shown in FIGS. 5 and 6, even when the plate thickness, which is a factor having a great influence on local buckling, is changed, the flange angle θ, the flange angle θ, and the moment of inertia of area The effective height h, which is determined by the relationship, gives the optimum solution that maximizes the local buckling strength.

(Third study example)
Next, when the effective width B of the hat-shaped steel sheet pile 1 is 1100 mm, 1300 mm, and 1500 mm, respectively, the moment of inertia of area per 1 m of the wall width of the steel sheet pile wall is about ^{9,000 cm 4} / m (9000 class). ) ~ Approximately ^{55,000 cm 4} / m (55,000 class). Classes of effective width B (mm), effective height h (mm), web plate thickness tw (mm), aspect ratio B / h, flange angle θ (degrees), and moment of inertia of area of the set cross-sectional shape. It is shown in Tables 3 to 5.

Here, in the example shown in Table 3, the web plate thickness tw and the arm plate thickness ta are both 9.0 mm, but the flange plate thickness tf is thinned to 6.3 mm (flange plate thickness with respect to the web). The ratio is 0.7). In the example shown in Table 4, the web plate thickness tw, the flange plate thickness tf, and the arm plate thickness ta are all 9.0 mm (the flange plate thickness ratio to the web is 1.0). In the example shown in Table 5, the web plate thickness tw and the arm plate thickness ta are both 12.5 mm, but the flange plate thickness tf is 7.5 mm (the flange plate thickness ratio to the web is 0.6). In each of the examples in Tables 3 to 5, the same buckling proof stress analysis as in the examples shown in FIGS. 4 to 6 was performed in the cross-sectional shape, and the optimum result is considered to show the maximum value of the local buckling proof stress. A flange angle θ and a corresponding effective height h are set.

FIG. 7 is a graph showing the relationship between the flange angle and the aspect ratio in the third study example. In the graph of FIG. 7, between the flange angle θ and the aspect ratio B / h of the hat-shaped steel sheet pile 1 when the plate thickness ratio is 1.0, 0.7, and 0.6, respectively. It is observed that there is a correlation that does not depend on the effective width B or the moment of inertia of area.

(Fourth study example)
Next, with the same effective width B as in the third study example described above, the plate thickness was increased within the range where the converted width-thickness ratio was 120 or more. Effective width B (mm), effective height h (mm), web plate thickness tw (mm), aspect ratio B / h, flange angle θ (degrees), and moment of inertia of area of the cross-sectional shape set in this example. The classes of are shown in Table 6.

Here, in each of the examples shown in Table 6, the plate thickness ratio is 0.7. That is, in each example, the web plate thickness tw and the arm plate thickness ta are equal, and the flange plate thickness tf is 0.7 times the web plate thickness tw. In each example of Table 6, the same buckling proof stress analysis as the examples shown in FIGS. 4 to 6 was performed in the cross-sectional shape, and the optimum flange angle considered to show the maximum value of the local buckling proof stress in the result. θ and the corresponding effective height h are set.

FIG. 8 is a graph showing the relationship between the flange angle and the aspect ratio in the fourth study example together with a part of the third study example (example of plate thickness ratio 0.7 shown in Table 3). Also in the graph of FIG. 8, it is observed that there is a correlation between the flange angle θ of the hat-shaped steel sheet pile 1 and the aspect ratio B / h that does not depend on the effective width B or the moment of inertia of area. Further, in the graph of FIG. 8, in each example in which the web plate thickness tw is different but the plate thickness ratio (0.7) is common, the flange angle θ and the aspect ratio B / h are correlated on a substantially common curve. It is observed to show a relationship.

(Summary of study examples)
9 and 10 are graphs showing the relationship between the flange angle and the aspect ratio in the third and fourth study examples together with an approximate curve of the correlation for each plate thickness ratio. Here, when the economic viewpoint and the restrictions such as the manufacturing equipment are taken into consideration as described above, the range in which the plate thickness ratio of the hat-shaped steel sheet pile 1 can be realistically taken is approximately 0.6 to 1.0. The third and fourth study examples include the upper limit and the lower limit of the range of such a plate thickness ratio. Therefore, the conditions that can be used in the design of a realistic hat-shaped steel sheet pile 1 are expressed by the following equation (3) using the constant C based on the two approximate curves shown in the graphs of FIGS. 9 and 10. be able to. Here, FIG. 9 shows a case where the range of the plate thickness ratio of the hat-shaped steel sheet pile 1 is 0.6 or more and 1.0 or less, and the range of the constant C is 1.01 ≦ C ≦ 1.13. .. On the other hand, FIG. 10 shows a case where the range of the plate thickness ratio of the hat-shaped steel sheet pile 1 is 0.7 or more and 1.0 or less, and the range of the constant C is 1.03 ≦ C ≦ 1.13.

The actual cross-sectional shape of the hat-shaped steel sheet pile is not determined only by considering the buckling resistance to the axial force, and for example, the effective width and the effective height are greatly affected by the manufacturing restrictions. In addition, the effective height of the hat-shaped steel sheet pile must be set so that the moment of inertia of area required for the design of the wall body can be obtained. Further, from the viewpoint of economy, it is desirable to make the web plate thickness and the arm plate thickness larger than the flange plate thickness, that is, the plate thickness ratio described above to be smaller than 1.0, but the feasible plate thickness ratio The scope is constrained by manufacturing equipment constraints and technical level.

On the other hand, the correlation between the optimum flange angle for maximizing the local buckling strength and the aspect ratio found in the above study example is as shown in the third study example. It does not depend on the effective width of the sheet pile or the moment of inertia of area. Further, as shown in the fourth study example, although the above correlation is affected by the plate thickness ratio, the effect of the absolute value of the plate thickness is small. That is, according to the result of the above examination, the condition of the cross-sectional shape that maximizes the local buckling yield strength is specified by the flange angle θ and the two dimensionless quantities (aspect ratio B / h and plate thickness ratio tf / tw). Will be done. By using this condition, it is possible to design the cross-sectional shape so that the local buckling proof stress is maximized on the premise of the restrictions of the manufacturing equipment and the required moment of inertia of area.

Although the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to such examples. It is clear that a person having ordinary knowledge in the field of technology to which the present invention belongs can come up with various modifications or modifications within the scope of the technical ideas described in the claims. It is naturally understood that these also belong to the technical scope of the present invention.

1 ... hat-shaped steel sheet pile, 2 ... web, 3A, 3B ... flange, 4A, 4B ... arm, 5A, 5B ... fitting joint, _{E A,} E B _... fitting center.

Claims (2)

It is a hat-shaped steel sheet pile
In a cross section orthogonal to the longitudinal direction, a web extending along the width direction on the first side in the cross-sectional height direction, and both ends of the web in the width direction on both sides in the width direction and in the cross-sectional height direction. From each end of a pair of flanges extending toward the second side and forming a flange angle θ with the width direction and the pair of flanges on the second side in the cross-sectional height direction. A pair of arms extending along the width direction and toward both sides in the width direction, and a pair of fittings formed at the ends of the pair of arms opposite to the pair of flanges. Equipped with a joint
The ratio of the total length of the web, the pair of flanges, and the pair of arms in the cross section to the average plate thickness of the web, the pair of flanges, and the pair of arms is 120 or more. ,
The effective width B and the effective height h in the cross section and the flange angle θ are constants C (1.01 ≦ C ≦) in the range where the plate thickness ratio of the flange to the web is 0.6 or more and 1.0 or less. The condition of the following formula (i) using 1.13) is satisfied, and the effective width B, the web length Bw in the cross section, the cross section height H and the flange angle θ are B-Bw-2H / tanθ> 0. Hat-shaped steel sheet pile that satisfies the relationship.

It is a hat-shaped steel sheet pile
In a cross section orthogonal to the longitudinal direction, a web extending along the width direction on the first side in the cross-sectional height direction, and both ends of the web in the width direction on both sides in the width direction and in the cross-sectional height direction. From each end of a pair of flanges extending toward the second side and forming a flange angle θ with the width direction and the pair of flanges on the second side in the cross-sectional height direction. A pair of arms extending along the width direction and toward both sides in the width direction, and a pair of fittings formed at the ends of the pair of arms opposite to the pair of flanges. Equipped with a joint
The ratio of the total length of the web, the pair of flanges, and the pair of arms in the cross section to the average plate thickness of the web, the pair of flanges, and the pair of arms is 120 or more. ,
The effective width B and the effective height h in the cross section and the flange angle θ are constants C (1.03 ≦ C ≦) in the range where the plate thickness ratio of the flange to the web is 0.7 or more and 1.0 or less. The condition of the following formula (i) using 1.13) is satisfied, and the effective width B, the web length Bw in the cross section, the cross section height H and the flange angle θ are B-Bw-2H / tanθ> 0. Hat-shaped steel sheet pile that satisfies the relationship.

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