JP7143891B2 - Manufacturing method of hat-shaped steel sheet pile - Google Patents

Description

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

Hat-shaped steel sheet piles are widely used in civil engineering and construction work for constructing walls for retaining earth and stopping water by driving them into the ground. Therefore, conventionally, the bending performance of the wall has been emphasized. In addition, there is a tendency for the cross section of the hat-shaped steel sheet pile to be widened and thinned in order to improve economy, that is, to reduce the weight of the wall.

On the other hand, as the performance and economic efficiency of hat-shaped steel sheet piles have improved, peripheral technologies for hat-shaped steel sheet piles have been developed, and the range of application and usage has expanded. An example of peripheral technology development is the enlargement of construction heavy machinery. The purpose of increasing the size of construction heavy machinery is, for example, to enable construction to harder strata or deeper strata, and to increase construction efficiency. When construction heavy machinery is enlarged in this way, not only is bending stress applied to the hat-shaped steel sheet pile after placement, but also a large axial force acts during construction.

In addition, the scope of application of hat-shaped steel sheet piles is being expanded. Specifically, for example, hat-shaped steel sheet piles are often used as foundations in addition to conventional walls. For example, Patent Literature 1 describes a technique of using steel sheet piles as a foundation structure. Patent Document 2 describes a technique for improving the bearing capacity by providing a closed 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 foundation. Thus, when the hat-shaped steel sheet pile is used as a foundation to bear the supporting force, 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 composed of thin plate materials such as hat-shaped steel sheet piles, it is necessary to pay sufficient attention to local buckling among other types of buckling. From this point of view, Patent Literature 3 proposes a technique for improving the buckling resistance by forming bent portions at the corners in the cross section of the hat-shaped steel sheet pile. Considering that the cross section of hat-shaped steel sheet piles tends to be widened and thinned as described above, it is considered that improvement of the buckling strength against axial force of hat-shaped steel sheet piles will become more and more necessary in the future.

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

However, although the technology 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 deteriorate. 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 strength against axial force while maintaining the basic cross-sectional shape of the hat-shaped steel sheet pile, which is the web, flange, and arm.

Accordingly, the present invention provides a novel and improved method for manufacturing a hat- shaped steel sheet pile that can improve the buckling resistance against axial force while maintaining the basic cross-sectional shape of the hat-shaped steel sheet pile. intended to provide

According to one aspect of the present invention, the hat-shaped steel sheet pile includes, in a cross section perpendicular to the longitudinal direction, 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. A pair of flanges extending toward 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 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 the end of each of the pair of arms opposite to the pair of flanges. and a pair of mating 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 effective height h and the flange angle θ are the following formula using a constant C (1.01 ≤ C ≤ 1.13) in the range of the thickness ratio of the flange to the web of 0.6 or more and 1.0 or less The condition (i) is satisfied, and the effective width B, the web length Bw in the section, the section height H and the flange angle θ satisfy the relationship BBw-2H/tan θ>0.

According to another aspect of the present invention, the hat-shaped steel sheet pile includes, in a cross section orthogonal to the longitudinal direction, a web extending along the width direction on a first side in the cross-sectional height direction, and both ends of the web in the width direction. A pair of flanges extending from both sides in the width direction and toward the second side in the height direction of the cross section and forming a flange angle θ with the width direction, and a pair on the second side in the height direction of the cross section A pair of arms extending along the width direction and toward both sides in the width direction from the respective ends of the flanges of the pair of arms, and the ends of the pair of arms opposite to the pair of flanges. and a pair of mating joints. The ratio of the total length of the web, the pair of flanges and the pair of arms in 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 effective height h in the cross section and the flange angle θ are constant C (1.03 ≤ C ≤ 1.13) in the range of the plate thickness ratio of the flange to the web of 0.7 or more and 1.0 or less and the effective width B, the web length Bw in the section, the section height H and the flange angle θ satisfy the relationship BBw-2H/tan θ>0.

According to the above configuration, the basic cross-sectional shape of the hat-shaped steel sheet pile can be maintained, and the buckling strength against the axial force can be improved.

1 is a cross-sectional view of a hat-shaped steel sheet pile according to an embodiment of the present invention; FIG. Fig. 10 is a graph showing the relationship between the converted width-thickness ratio and the web width-thickness ratio in conventional steel sheet pile products. It is a figure which shows roughly the cross-sectional shape of the hat-shaped steel sheet pile in the 1st examination example. 4 is a graph showing the results of buckling strength analysis in the first study example; 5 is a graph showing local buckling strength based on the results shown in FIG. 4; 7 is a graph showing local buckling strength based on the results of buckling strength analysis in the second study example. FIG. 11 is a graph showing the relationship between the flange angle and the aspect ratio in the third study example; FIG. FIG. 11 is a graph showing the relationship between the flange angle and the aspect ratio in the fourth study example together with part of the third study example. FIG. FIG. 11 is a graph showing the relationship between the flange angle and the aspect ratio in the third and fourth study examples, together with the approximate curve of the correlation for each plate thickness ratio; FIG. FIG. 11 is a graph showing the relationship between the flange angle and the aspect ratio in the third and fourth study examples, together with the approximate curve of the correlation for each plate thickness ratio; FIG.

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the present specification and drawings, constituent elements having substantially the same functional configuration are denoted by the same reference numerals, thereby omitting redundant description.

FIG. 1 is a cross-sectional view of a hat-shaped steel sheet pile according to one embodiment of the present invention. As shown in FIG. 1, the hat-shaped steel sheet pile 1, in a cross section orthogonal to the longitudinal direction (the z direction in the figure), has A 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 (the front side in the y direction in the figure) ) and form a flange angle θ (acute angle side) with the width direction, and the second side in the cross-sectional height direction from each end of the flanges 3A and 3B in the width direction arms 4A, 4B extending along and toward both sides in the width direction, and fitting joints 5A, 5B formed at the ends of the arms 4A, 4B opposite to the flanges 3A, 3B, respectively.

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

Further, FIG. 1 shows the effective width B, cross-sectional height H, and effective height h of the hat-shaped steel sheet pile 1 . Here, the effective width B is the distance between the mating centers E _A and E _B of the mating joints 5A and 5B, respectively. The cross-sectional height H is the cross-sectional height of the hat-shaped steel sheet pile 1 including the plate thicknesses of the web 2 and the arms 4A and 4B but not including the overhangs of the fitting joints 5A and 5B, and the effective height h is the cross-sectional height. H minus half the plate thickness of the web 2 and arms 4A, 4B, ie h=H−(tw/2+ta/2). In addition, when the shape of the hat-shaped steel sheet pile 1 shown in FIG. meet the relationship.

Here, regarding the hat-shaped steel sheet pile 1 according to the present embodiment, the ratio B _TTL /t _AVE of the total length B _TTL to the average plate thickness t _AVE is defined as the "converted width-thickness ratio". As will be described later, in the hat-shaped steel sheet pile 1, the converted width-to-thickness ratio B _TTL /t _AVE is 120 or more, and the effective width B and 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 formula (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 conventional steel sheet pile products. The present inventors have studied a method for improving the buckling strength against axial force while maintaining the basic cross-sectional shape of the hat-shaped steel sheet pile. Hat-shaped steel sheet piles, which are wider or thinner than the currently known hat-shaped steel sheet piles, should be considered because the cross-section of sheet piles tends to become wider and thinner. is reasonable. Here, as shown in FIG. 2, steel sheet piles with a converted width-to-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. In the study, a hat-shaped steel sheet pile with a converted width-to-thickness ratio of 120 or more, which is wider or thinner than conventional steel sheet pile products, is targeted.

In the study, buckling strength analysis (eigenvalue analysis based on elastic theory) was performed on hat-shaped steel sheet piles with a converted width-to-thickness ratio of 120 or more in various cross-sectional shapes with different effective widths, cross-sectional heights, and plate thicknesses. 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 following discoveries 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 web thickness tw, the flange thickness tf, and the arm thickness ta were all set to 9.0 mm. Under these conditions, a plurality of hat-shaped steel sheet piles 1 are fitted to each other by the fitting joints 5A and 5B and connected in the width direction. A plurality of cross-sectional shapes of ⁴ /m were set. Table 1 shows the set effective height h (mm) and flange angle θ (degrees) of the set cross-sectional shape, and FIG. 3 schematically shows each cross-sectional shape.

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

FIG. 4 is a graph showing the results of buckling strength analysis in the first study example. In FIG. 4, the horizontal axis indicates the length (longitudinal dimension) of the hat-shaped steel sheet pile, and the vertical axis indicates the buckling capacity (elastic analysis result) of the hat-shaped steel sheet pile. In the graph of FIG. 4, it is observed that a local buckling mode occurs at the location indicated by the arrow (1) and the yield strength decreases. In this study, the yield strength in this local buckling mode (local buckling strength) was treated as a result, and the local buckling strength in each cross-sectional shape was compared. Note that arrows (2) in the graph of FIG. 4 indicate, from the top, example 1 (θ=70°), example 2 (θ=60°), . . . , example 9 (θ = 29°) is shown.

FIG. 5 is a graph showing local buckling capacity based on the results shown in FIG. In FIG. 5, the horizontal axis indicates the flange angle θ of each cross-sectional shape, and the vertical axis indicates the local buckling strength. In the graph of FIG. 5, it can be observed that the local buckling strength increases rapidly as the flange angle θ increases from a small value, reaches a maximum value at a certain angle, and then gradually decreases as the flange angle θ increases. be done. In the case of the example shown in FIG. 5, the optimum flange angle θ at which the local buckling resistance exhibits the maximum value is 33.5°. From these results, it can be concluded that the flange angle θ greatly contributes to the suppression of out-of-plane deformation associated with local buckling of each portion (web 2, flanges 3A and 3B, and arms 4A and 4B) of the hat-shaped steel sheet pile 1. it is conceivable that. That is, according to the above results, in the cross-sectional design of the hat-shaped steel sheet pile 1, the flange angle θ should be appropriately determined, and the effective height h should be determined according to the relationship between the flange angle θ and the moment of inertia of area. gives the optimal solution that maximizes the local buckling strength.

(Second study example)
Next, the effective width B of the hat-shaped steel sheet pile 1 was kept at 1350 mm, the plate thickness was set to 10.0 mm for the web plate thickness tw and the arm plate thickness ta, and for the flange plate thickness tf to 8.0 mm. Under these conditions, a plurality of cross-sectional shapes were set such that the secondary moment of area per meter of 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 strength based on the buckling strength analysis results in the second study example. In the graph of FIG. 6 as well, it is observed that the local buckling resistance shows a maximum value with respect to the flange angle .theta. In the case of the example shown in FIG. 6, the optimum flange angle θ at which the local buckling strength is considered to exhibit 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 that greatly affects local buckling, is changed, the relationship between the flange angle θ, the flange angle θ, and the moment of inertia of area The effective height h 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 1,100 mm, 1,300 mm, and 1,500 mm, respectively, the geometrical moment of inertia per 1 m of wall width of the steel sheet pile wall is about 9,000 cm ⁴ /m (9,000 class ) to about 55,000 cm ⁴ /m (55,000 class). Effective width B (mm), effective height h (mm), web plate thickness tw (mm), aspect ratio B/h, flange angle θ (degrees), and geometrical moment of inertia class 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 reduced to 6.3 mm (flange plate thickness with respect to the web ratio of 0.7). In the example shown in Table 4, the web thickness tw, the flange thickness tf, and the arm thickness ta are all 9.0 mm (the thickness ratio of the flange to the web is 1.0). In the example shown in Table 5, the web thickness tw and the arm thickness ta are both 12.5 mm, but the flange thickness tf is 7.5 mm (the thickness ratio of the flange to the web is 0.6). In each of the examples in Tables 3 to 5, buckling strength analysis similar to the examples shown in FIGS. 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, when the plate thickness ratio is 1.0, 0.7, and 0.6, the relationship between the flange angle θ and the aspect ratio B/h of the hat-shaped steel sheet pile 1 is , 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, the plate thickness was increased within a range in which the converted width-to-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 geometrical moment of inertia of the cross-sectional shape set in this example are shown in Table 6.

Here, in the examples shown in Table 6, the plate thickness ratio is 0.7. That is, in each example, the web thickness tw and the arm thickness ta are equal, and the flange thickness tf is 0.7 times the web thickness tw. For each example in Table 6, buckling strength analysis similar to the examples shown in FIGS. 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 (an example of the plate thickness ratio of 0.7 shown in Table 3). It is observed from the graph in FIG. 8 that there is a correlation between the flange angle θ and the aspect ratio B/h of the hat-shaped steel sheet pile 1, which does not depend on the effective width B or the moment of inertia of the area. Furthermore, in the graph of FIG. 8, even if the web plate thickness tw is different, in each example in which 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 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 approximate curves of the correlation for each plate thickness ratio. Here, when considering the economic viewpoint and the constraints of manufacturing equipment etc. as described above, the range that the plate thickness ratio of the hat-shaped steel sheet pile 1 can realistically take is approximately 0.6 to 1.0. The third and fourth considerations include the upper and lower limits of such thickness ratio ranges. Therefore, the conditions that can be used for designing a realistic hat-shaped steel sheet pile 1 are represented by the following equation (3) using a 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 cross-sectional shape of an actual hat-shaped steel sheet pile is not determined by considering only the buckling strength against axial force, and for example, the effective width and effective height are greatly affected by manufacturing restrictions. In addition, the effective height of the hat-shaped steel sheet pile must be set so as to obtain the geometrical moment of inertia required for the design of the wall. From the viewpoint of economy, it is desirable to make the web thickness and the arm thickness larger than the flange thickness, that is, to make the thickness ratio less than 1.0. The range is limited by manufacturing facility restrictions and technology levels.

On the other hand, the correlation between the optimum flange angle and the aspect ratio that maximizes the local buckling strength found in the above study example is the hat-shaped steel as shown in the third study example. It does not depend on the effective width of the sheet pile or the geometric moment of inertia. 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. In other words, according to the results of the above study, the condition of the cross-sectional shape that maximizes the local buckling strength is specified by the flange angle θ and two dimensionless quantities (aspect ratio B/h and plate thickness ratio tf/tw). be done. By using this condition, it is possible to design the cross-sectional shape so as to maximize the local buckling resistance, on the premise of the constraints of the manufacturing equipment and the required geometric moment of inertia.

Although the preferred embodiments of the present invention have been described in detail above 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 technical field to which the present invention belongs can conceive of various modifications or modifications within the scope of the technical idea described in the claims. It is understood that these also belong to the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1... Hat-shaped steel sheet pile, 2... Web, 3A, 3B... Flange, 4A, 4B... Arm, 5A, _5B ... Fitting joint, EA, _EB ... Fitting center.

Claims (2)

A method for manufacturing a hat-shaped steel sheet pile,
In a cross section orthogonal to the longitudinal direction, the hat-shaped steel sheet pile includes a web extending along the width direction on a first side in the cross-sectional height direction, both sides in the width direction from both ends of the web in the width direction, a pair of flanges extending toward the second side in the cross-sectional height direction 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 from the respective ends of the pair of arms, and the ends of the pair of arms opposite to the pair of flanges a pair of mating joints formed;
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 effective height h in the cross section and the flange angle θ are constant C (1.01 ≤ C ≤ 1.13), and the effective width B, the web length Bw in the cross section, the cross-sectional height H and the flange angle θ are B−Bw−2H/tan θ>0 A method for manufacturing a hat-shaped steel sheet pile, comprising the step of designing the cross section so as to satisfy the relationship of

A method for manufacturing a hat-shaped steel sheet pile,
In a cross section orthogonal to the longitudinal direction, the hat-shaped steel sheet pile includes a web extending along the width direction on a first side in the cross-sectional height direction, both sides in the width direction from both ends of the web in the width direction, a pair of flanges extending toward the second side in the cross-sectional height direction 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 from the respective ends of the pair of arms, and the ends of the pair of arms opposite to the pair of flanges a pair of mating joints formed;
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 effective height h in the cross section and the flange angle θ are constant C (1.03 ≤ C ≤ 1.13), and the effective width B, the web length Bw in the cross section, the cross-sectional height H and the flange angle θ are B−Bw−2H/tan θ>0 A method for manufacturing a hat-shaped steel sheet pile, comprising the step of designing the cross section so as to satisfy the relationship of

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