JP7238654B2 - Longitudinal structure of steel sheet piles - Google Patents

Description

The present invention relates to a tandem structure for steel sheet piles.

BACKGROUND ART Steel walls constructed by driving steel sheet piles and connecting them to the left and right are used as earth retaining walls, underground structures, and foundation structures in the field of civil engineering and construction. Depending on the construction conditions of the steel wall using steel sheet piles, long steel sheet piles exceeding the length that can be shipped from the rolling mill are required, or when road space is limited in mountainous areas and long steel sheet piles cannot be transported. In cases where it is not possible to secure the installation space due to structures, etc., above the steel sheet pile installation location, it is necessary to connect the steel sheet piles in the longitudinal direction at the processing plant or site, that is, to splice the steel sheet piles. .

As a general technique for longitudinally splicing two steel sheet piles in the longitudinal direction (material axial direction), there is a welding method using a reinforcing plate proposed by the Steel Pipe Pile/Steel Sheet Pile Technical Association. In this construction method, the steel sheet pile end surfaces, excluding joints, are beveled and full-section welding is performed, and reinforcing plates are attached by welding across the longitudinal joints.
When joining steel sheet piles in the longitudinal direction (longitudinal splicing) during construction at a construction site, one side of the steel sheet pile edge (the end in the longitudinal direction (material axial direction)) is beveled in advance at the factory. Then, with the end faces of the upper and lower steel sheet piles facing each other, the groove part is welded and connected. However, since the joint has a complicated shape, it is difficult to perform grooving and welding, and if the weld metal melts out and remains in the joint, the joints of adjacent steel sheet piles must be fitted together and driven. Since it becomes a resistance to placing and becomes a hindrance, it is not grooved or welded, and is made to be in surface contact in a butted state.

When driving steel sheet piles, depending on the ground conditions, excessive compressive force and pull-out force may act on the steel sheet piles. power must be ensured. Therefore, in order to compensate for the cross-sectional area loss equivalent to the joint portion where welding is not performed, a reinforcing plate is attached by welding in a form straddling the longitudinal joining line of the upper and lower steel sheet piles to secure the cross-sectional area for the cross-sectional loss.

As a reinforcing plate, in addition to securing the axial resistance during placement, the specifications are determined in consideration of the performance to secure the bending strength as a wall body (steel wall) during use. there is When a bending moment acts on the wall, in order to avoid local stress concentration, the vertical joints should be at least 1m between adjacent steel sheet piles so that the vertical joints are not at the same depth between adjacent steel sheet piles. They are arranged in a zigzag arrangement while securing a distance between them (see Patent Documents 1 and 2, for example). A steel sheet pile having a standard cross section without vertical joints and a steel sheet pile with vertical joints are used as a set of two units to ensure bending strength as a wall body. Determine the weld length and leg length of the reinforcing plate so that the load corresponding to the stress load generated in the reinforcing plate when the bending moment acts on the steel wall can be transmitted.

Structural specifications have also been proposed in which a reinforcing plate is joined to a steel sheet pile body with bolts (see Patent Documents 3 and 4, for example). However, it is necessary to drill bolt holes in the steel sheet pile body, which causes cross-sectional defects, the bolt holes reduce the water stoppage, and stress relaxation occurs in the bolts due to vibration when driving the steel sheet piles, reducing the tightening strength of the bolts. It is used only under special construction site conditions, such as when welding cannot be performed on site.

Japanese Patent No. 4419198 JP 2016-156247 A Japanese Patent No. 5182251 Japanese Patent Application Laid-Open No. 2017-66702

By the way, when the steel sheet pile becomes large, the joint part becomes large, and the cross-sectional area that is lost at the longitudinal joint part becomes large. According to the specifications of , the thickness and width required for the reinforcing plate also increase. As a result, the reinforcement plate attached to the web of the steel sheet pile is particularly large and heavy, which reduces the efficiency of transportation and welding work. Furthermore, the amount of welding for fixing the reinforcing plate is also increased, resulting in a longer welding time and an increase in cost. As the amount of welding increases, the number of steel sheet piles that can be driven per day decreases, and the construction cost of the entire steel sheet pile increases.

In the past, it was assumed that on-site welding could secure only about 80% or about 90% of the yield strength of factory welding.
However, as welding technology has improved and on-site construction management and quality control have improved, welders with appropriate skills are required to perform welding under an appropriate welding environment, and non-destructive inspections and records of the construction process are required. It has become possible to secure the same level of yield strength as factory welding if the same level of control as factory welding is performed by conducting quality control through standardization, etc. (For example, technical standards and explanations for port facilities , May 2018, Japan Port and Harbor Association, supervised by the Port and Harbor Bureau of the Ministry of Land, Infrastructure, Transport and Tourism, p.472).

Therefore, as described above, after performing the same management as factory welding, the upper and lower steel sheet pile end faces are butted together, and the groove part of this butt part is securely welded on the whole cross section to bend it into a steel sheet pile with a longitudinal joint structure. As a result of testing, it has been found that the yield strength of the tandem line can be secured even without the reinforcing plate attached to the web.

The present invention has been made in view of the above circumstances, and provides a tandem structure for steel sheet piles that is capable of reducing costs and improving workability while ensuring the necessary proof strength in a tandem structure having a cross-sectional area defect in a joint. intended to

In order to achieve the above object, the tandem structure of steel sheet piles of the present invention is a tandem structure of steel sheet piles for connecting steel sheet piles having a steel sheet pile main body and a joint portion in the material axial direction,
At least part of the steel sheet pile bodies are joined by full-section welding, and the joint portions are not welded together,
A reinforcing plate is welded between the steel sheet piles so as to straddle the longitudinal connection line,
The reinforcing plate is characterized by satisfying all of the following conditions (1) to (3).
(1) The reinforcing plate is attached to a steel sheet pile portion other than the web at the center portion in the width direction of the steel sheet pile body.
(2) The total cross-sectional area of the reinforcing plate in the cross section of the longitudinal connection line is equal to or greater than the total cross-sectional area of the cross-sectional missing portions of the steel sheet piles where the steel sheet piles are not fully cross-sectionally welded to each other.
(3) The total geometrical moment of inertia of the reinforcing plate in the cross section of the longitudinal connection line with respect to the neutral axis of the steel sheet pile cross section of the steel sheet pile is equal to or greater than the total geometrical moment of inertia of the missing section portion.

Here, examples of the steel sheet piles include hat-shaped steel sheet piles, U-shaped steel sheet piles, and Z-shaped steel sheet piles.
The hat-shaped steel sheet pile includes a steel sheet pile body and joint portions formed at both widthwise end portions of the sheet pile body. The steel sheet pile body includes a web, flange portions formed at both side end portions thereof, and arm portions formed at the outer side ends of the flange portion. Therefore, the "steel sheet pile portion other than the web" means the flange portion, the arm portion, or the joint portion, and the reinforcing plate is preferably attached to the arm portion.

In addition, the U-shaped steel sheet pile includes a steel sheet pile main body and joint portions formed at both widthwise end portions thereof, and the steel sheet pile main body includes a web and flange portions formed at both side end portions thereof. and Therefore, the "steel sheet pile portion other than the web" means the flange portion or the joint portion, and the reinforcing plate is preferably attached to the flange portion near the joint portion. Further, the reinforcing plate may be attached to the outer surface facing the outside of the flange portion, the inner surface facing the inside, or both the outer surface and the inner surface.

In addition, the Z-shaped steel sheet pile is provided with a steel sheet pile main body and joint portions formed at both ends in the width direction thereof, and the steel sheet pile main body is composed of diagonally arranged webs and both side ends thereof. and a flange portion formed on the . Therefore, the "steel sheet pile portion other than the web" means the flange portion or the joint portion, and the reinforcing plate is preferably attached to the flange portion near the joint portion. Also, the reinforcing plate may be attached to both sides of the flange portion, or only to one side.

In the present invention, since the total cross-sectional area of the reinforcing plate in the cross section of the longitudinal connection line is equal to or greater than the total cross-sectional area of the cross-sectional defect of the steel sheet pile, when the steel sheet pile is driven into the ground or pulled out, the steel sheet pile With respect to the tensile load acting on the vertical joint, the yield strength of the longitudinal joint is equal to or greater than that of the steel sheet pile base material (steel sheet pile without longitudinal joint).
In addition, with respect to the neutral axis of the steel sheet pile cross section of the steel sheet pile, since the total geometrical moment of inertia of the reinforcing plates in the cross section of the steel sheet pile is greater than or equal to the total geometrical moment of inertia of the cross-sectional defect part of the steel sheet pile, the steel sheet pile It compensates for the cross-sectional loss of the steel sheet pile and secures the bending rigidity of the steel sheet pile.
Further, the reinforcing plate is attached to the steel sheet pile portion other than the web in the width direction central portion of the steel sheet pile body.
Therefore, it is possible to provide a tandem structure of steel sheet piles capable of reducing costs and improving workability while ensuring the required yield strength in the tandem structure having a cross-sectional area defect in the joint portion.

Further, in the above configuration of the present invention, the steel sheet pile includes a web, a pair of flange portions formed on both side ends of the web, and a pair of flange portions formed on the outer side ends of the pair of flange portions. A hat-shaped steel sheet pile comprising the steel sheet pile body having arm portions of and a pair of the joint portions formed at the outer side ends of the pair of arm portions,
The reinforcing plate may be attached only to the arm portion.

According to such a configuration, when a bending moment acts on the steel sheet piles and a force acts on the unwelded joints at the longitudinal joints of the steel sheet piles to open them, the joints will be broken. Since the reinforcing plate is attached to the formed arm portion, such force can be efficiently resisted, and the opening of the joint portions can be suppressed.

Further, in the above configuration of the present invention, the reinforcing plate may be attached to both sides of the arm portion, or only one side. preferably installed.

Here, the two sides of the arm part refer to two sides perpendicular to the height direction of the steel sheet pile (the direction perpendicular to the width direction and the longitudinal direction of the steel sheet pile). Further, the one side of the arm portion is either one of the two sides, and is either the side farther from the neutral axis or the side closer to the neutral axis.

According to such a configuration, by attaching the reinforcing plates to both sides of the arm portion, the load to be borne by the reinforcing plates is dispersed. can be reduced, and the welding length can be increased more efficiently than when there is only one reinforcing plate, so the steel weight of the entire reinforcing plate can be reduced.
In addition, by attaching the reinforcing plate to only one side of the arm portion, the installation position of the welding machine can be set only on one side of the arm portion, thereby reducing the setup work for welding.
Furthermore, by attaching a reinforcing plate to one side of the arm on the far side from the neutral axis, it is possible to efficiently secure the geometrical moment of inertia necessary for the reinforced part, and reduce the thickness of the reinforcing plate to reduce the bending moment. Since the edge stress can be reduced, the total welding volume of the welding point between the reinforcing plate and the arm can be reduced, leading to a reduction in the cost of welding materials.

Further, in the above configuration of the present invention, the thickness of the reinforcing plate on the side of the joint portion may be thicker than the thickness of the side opposite to the joint portion. It may be thicker as it approaches .

When a bending moment acts on the longitudinal joint of the steel sheet pile and a tensile load acts on the arm side of the steel sheet pile cross section, that is, on the missing joint, when the bending moment increases, the welding of the longitudinal joint butt part in the width direction of the steel sheet pile will occur. There is a risk that cracks may occur from the weld toes of the arm portions, which are both ends. If the bending moment further increases, there is a risk that the crack will progress to the reinforcing plate, and once the crack penetrates the reinforcing plate, the yield strength will decrease significantly.
Therefore, by adopting the above-described configuration, that is, by making the plate thickness of the reinforcing plate on the joint portion side thicker than the plate thickness on the side opposite to the joint portion, crack propagation to the reinforcing plate can be suppressed.

Further, in the configuration of the present invention, an auxiliary member may be fixed between the joint portions so as to straddle the longitudinal connection line.

According to such a configuration, since the auxiliary member is fixed to the joint parts so as to straddle the longitudinal joint line, the longitudinal joint butt part can be prevented before the crack propagates to the reinforcing plate as described above. It is possible to suppress the occurrence of cracks at the weld toes of the arms, which are the weld ends of the arm.

Advantageous Effects of Invention According to the present invention, it is possible to provide a tandem structure of steel sheet piles that is capable of reducing costs and improving workability while ensuring the required yield strength in a tandem structure having a cross-sectional area defect in a joint portion.

BRIEF DESCRIPTION OF THE DRAWINGS It is a perspective view which shows embodiment of this invention and which shows the longitudinal connection structure of a steel sheet pile. It is a perspective view of a reinforcing plate equally. Similarly, (a) is a cross-sectional plan view of a steel sheet pile showing a state in which a reinforcing plate is attached to one side of an arm portion, and (b) is an enlarged cross-sectional plan view of a joint portion. Fig. 3 is a plan cross-sectional view of the steel sheet pile showing a state in which a reinforcing plate is attached to the other side of the arm portion of the same; Fig. 3 is a cross-sectional plan view of the steel sheet pile showing a state in which reinforcing plates are attached to both surfaces of the arm portion of the same; Fig. 3 is a plan cross-sectional view of the main part of the steel sheet pile showing a state in which the reinforcing plate is attached to the joint portion while being shifted. Fig. 3 is a plan cross-sectional view of the main part of the steel sheet pile showing a state in which the reinforcing plate is divided into two and attached to the joint portion. In the same figure, (a) is a plan cross-sectional view of the main part of the steel sheet pile showing the state in which the plate material is additionally fixed to the reinforcing plate attached to the arm, and (b) is the state in which the reinforcing plate made of tapered steel plate is attached to the arm. It is a plane cross-sectional view of the main part of the steel sheet pile shown. Fig. 3 is a cross-sectional plan view of a main part of the steel sheet pile showing a state in which an auxiliary member is attached to a joint portion of the same; Similarly, (a) is a perspective view showing a main part of a longitudinal joint structure of steel sheet piles when the reinforcing plate of the first modified example is attached, and (b) is a cross-sectional view of the main part. Similarly, (a) is a perspective view showing a main part of a longitudinal joint structure of steel sheet piles when the reinforcing plate of the second modification is attached, and (b) is a cross-sectional view of the main part. It is a perspective view which shows the longitudinal joint structure of a steel sheet pile when the reinforcing plate of a 3rd modification is attached. It is a front view which shows the reinforcing plate of a 4th modification equally. It is a front view which shows the reinforcing plate of a 5th modification equally. It is a front view which shows the reinforcing plate of a 6th modification equally. Similarly, it is a diagram for explaining that depending on the set position of the welded portion (the angle of the weld line with respect to the direction in which the load acts), the total resistance can be made equal or greater. FIG. 4 is a diagram for explaining the stress acting on the throat section when a is the component force and the throat thickness with respect to P in an arbitrary direction with respect to the fillet weld, and e is the weld length. It is a graph which shows the relationship between a rhombus peripheral line inclination angle and a shear strength ratio equally. It is a front view which shows the reinforcing plate of a 7th modification equally. Similarly, eighth to twelfth modifications are shown, (a) is a front view of the reinforcing plate of the eighth modification, (b) is a front view of the reinforcing plate of the ninth modification, and (c) is the tenth modification. FIG. 11D is a front view of a reinforcing plate of a modified example, (d) is a front view of a reinforcing plate of an eleventh modified example, and (e) is a front view of a reinforcing plate of a twelfth modified example. Fig. 10, which shows another embodiment of the present invention, is a plan cross-sectional view of a steel sheet pile showing a state in which a reinforcing plate is attached to a flange portion. Fig. 10, which shows another embodiment of the present invention, is a plan cross-sectional view of a steel sheet pile showing a state in which a reinforcing plate is attached to a flange portion.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view showing a longitudinal joint structure of steel sheet piles according to the embodiment.
In this embodiment, the upper steel sheet pile 10 and the lower steel sheet pile 10 are vertically joined.
The steel sheet pile 10 is a hat-shaped steel sheet pile, and includes a steel sheet pile body 11 and joint portions 12 , 12 provided on both side edges of the steel sheet pile body 11 .
The steel sheet pile 10 is not limited to the hat-shaped steel sheet pile, and may be, for example, a U-shaped steel sheet pile, a Z-shaped steel sheet pile, or the like.

The steel sheet pile body 11 includes a web 13 positioned in the center in the width direction, a pair of left and right flanges 14, 14 formed on both side edges of the web 13, and outer side ends of the flanges 14, 14. A pair of left and right arm portions 15, 15 are provided. The joint portions 12 , 12 are formed at the outer side end portions of the pair of arm portions 15 , 15 .
Although illustration is omitted, such steel sheet piles 10 are connected in the lateral direction by fitting the joint portions 12, 12 of the steel sheet piles 10, 10 adjacent to each other on the left and right, thereby forming a steel wall. It is formed continuously from side to side (in the width direction of the steel sheet pile 10).

Also, the upper and lower steel sheet piles 10, 10 are joined. That is, the steel sheet pile bodies 11, 11 of the steel sheet piles 10, 10 are joined together in the plate thickness direction by full-section welding (the full-section welded portion exists continuously along the width direction of the steel sheet pile body 11). ), but a portion near the connection with the joint portions 12, 12, which is the end portion of the steel sheet pile body 11, may include a portion where the full cross-section is not welded. In the steel sheet pile body 11, in order to avoid a sudden change in stress at the end of the butt weld, groove processing is performed near the connection with the joints 12, 12 from one side of the arm portions 15, 15 to the other side. It may be tapered in the width direction to gradually change the amount of welding. In this case, the tapered grooved and welded portion is treated as a cross-sectional defect portion that is not welded at the joint portions 12 , 12 . That is, the "cross-sectional loss of the steel sheet pile 10" in this specification includes, in addition to the cross-sectional loss of the joints 12, 12, in the above case (beveling near the connection part with the joints 12, 12, the arm In the case where the portions 15, 15 are tapered in the width direction from one surface to the other surface, and the amount of welding is gradually changed), the tapered grooving and welded portions are also included.
In this embodiment, the upper and lower steel sheet pile main bodies 11, 11 are welded over the entire cross section in the plate thickness direction. Specifically, although illustration is omitted, when the steel sheet piles 10, 10 are connected (vertical spliced) in the longitudinal direction during placing, the ends of the upper and lower steel sheet pile bodies 11, 11 facing vertically Either one of them, or when the steel sheet piles 10, 10 are placed horizontally and connected (longitudinal joint) in the longitudinal direction before placing, a groove is formed in both, and the weld metal is applied to the groove. The upper and lower steel sheet pile main bodies 11, 11 are welded and joined together in the plate thickness direction by pouring and welding the groove portion over the entire cross section. Moreover, the joint portions 12, 12 of the upper and lower steel sheet piles 10, 10, which are vertically opposed to each other, are not welded to each other, but simply abutted.

In this way, since the upper and lower joint portions 12, 12 are not welded together, the steel sheet piles 10, 10 welded to the upper and lower sides have cross-sectional defects corresponding to the joint portions 12, 12 that are not welded. there is In this embodiment, as described above, the steel sheet pile bodies 11, 11 are fully cross-sectionally welded in the plate thickness direction, so that the above-mentioned "cross-sectional defect of the steel sheet pile 10" is formed in the joints 12, 12. It corresponds to the corresponding cross-sectional defect.
For this reason, in this embodiment, in order to compensate for the cross-sectional defect, the reinforcing plates 20 and 20 are joined to the upper and lower steel sheet pile bodies 11 and 11 by fillet welding on the outer periphery so as to straddle the longitudinal connection line 16. The steel sheet pile main bodies 11 and 11 are also joined by welding by this. Here, the tandem line 16 is a joint line generated when the upper and lower steel sheet piles 10, 10 are butted against each other, and is generated on one side and the other side of the upper and lower steel sheet piles 10, respectively.
The reinforcing plates 20, 20 may be arranged so as to straddle the longitudinal joint line 16 generated on one side of the arm portions 15, 15 of the upper and lower steel sheet pile bodies 11, 11, or may be arranged so as to straddle the longitudinal joint line 16 generated on the other side. It may be arranged so as to straddle the line 16, and furthermore, it may be arranged so as to straddle the tandem lines 16 generated on both sides.

The reinforcing plate 20 is a rectangular flat plate and satisfies all of the following conditions (1) to (3).
(1) The reinforcing plate 20 is attached only to the arm portions 15, 15 on both sides of the steel sheet pile 10;
(2) The total cross-sectional area of the reinforcing plates 20, 20 in the cross section of the longitudinal connection line 16 is equal to or greater than the total cross-sectional area of the cross-sectional missing portions (cross-sectional missing portions of the steel sheet pile 10) corresponding to the joint portions 12, 12 that are not welded. be.
(3) The cross-sectional loss corresponding to the total cross-sectional moment of inertia of the reinforcing plates 20, 20 in the cross section of the longitudinal connection line 16 with respect to the neutral axis na of the steel sheet pile cross section of the steel sheet pile 10 corresponds to the joint portions 12, 12 that are not welded. be equal to or greater than the total geometrical moment of inertia of the part (the cross-sectional loss part of the steel sheet pile 10).
Furthermore, this embodiment also satisfies the following condition (4).
(4) The reinforcing plate 20 is attached to both sides of the arm portions 15, 15, or to only one side.

As shown in FIG. 2, the reinforcing plate 20 attached to the arm portion 15 by welding is a rectangular flat plate, the width of the reinforcing plate 20 is bp, the length of the reinforcing plate 20 is lp, Let t be the plate thickness, and s be the leg length of the welded portion when the reinforcing plate 20 is attached to the arm portion 15 by fillet welding.
As shown in FIG. 1, the reinforcing plate 20 is arranged such that the longitudinal direction of the reinforcing plate 20 is oriented vertically and the central portion of the reinforcing plate 20 in the longitudinal direction is aligned with the longitudinal joint line 16. After being placed on the arm portion 15, the reinforcing plate 20 is attached to the arm portion 15 by fillet welding.

As in condition (1) above, the reinforcing plate 20 is attached only to the arm portions 15, 15 on both sides of the steel sheet pile 10 (see FIGS. 3 to 5).
As in condition (4) above, the reinforcing plate 20 is attached to both sides of the arms 15 (see FIG. 5) or only one side (see FIGS. 3 and 4).
Here, the one side of the arm portion 15 refers to either one of the side 15a on the far side and the side 15b on the side closer to the neutral axis na of the steel sheet pile cross section, and both sides refer to the side 15a and the side 15b. Refers to both sides of 15b.
The neutral axis na is an axis that passes between the web 13 and the arm portion 15 of the steel sheet pile 10 and is parallel to the web 13, and is such that the cross-sectional primary moment of the steel sheet pile 10 is zero.

Explaining the condition (2) above, when the steel sheet pile 10 is driven into the ground or pulled out, the yield strength of the longitudinally jointed portion against the tensile load acting on the steel sheet pile 10 is the steel sheet pile base material (longitudinal joint The total cross-sectional area of the reinforcing plates 20, 20 in the cross section of the longitudinal joint line 16 is set to be equal to or greater than the total cross-sectional area of the joint portions 12, 12 that are not welded so as to be equal to or greater than the steel sheet piles with no points.
Here, as shown in FIG. 3B, the cross section of the joint portion 12 means a line segment 12b extending in a curved or straight line from the protrusion 12a of the joint portion 12 toward the arm portion 15 side and an arm in the cross section. It refers to the cross section of the joint portion 12 in the area outside (left side in FIG. 3(b)) of the line L perpendicular to the neutral axis na at the boundary with the edge line 15c of the portion 15. As shown in FIG.
Therefore, in the longitudinal joint structure of steel sheet piles in which the left and right joint portions 12, 12 have the same shape as shown in FIGS. is the area of two cross sections of one joint portion 12 .

Regarding the condition (3), by attaching the reinforcing plate 20 to the arm portion 15, the neutral axis na , the total geometrical moment of inertia of the cross-sectional reinforcing plates 20, 20 in the longitudinal connection line 16 is set to be equal to or greater than the total geometrical moment of inertia of the cross-sectional loss portions corresponding to the joint portions 12, 12 that are not welded.

The specifications of the reinforcing plate 20 are the total cross-sectional area of the reinforcing plates 20, 20 under the condition (2) described above, which is determined from the weld defect portion (cross-sectional defect portion) of the joint portion 12, and the reinforcement under the condition (3). From the condition that the necessary dimensions of the reinforcing plate 20 (width bp of the reinforcing plate 20, length lp of the reinforcing plate 20, thickness t of the reinforcing plate) of the total geometrical moment of inertia of the plates 20, 20 are larger set.

When forming a steel wall with the steel sheet piles 10, the steel sheet piles 10 without longitudinal joints and the steel sheet piles 10 with longitudinal joints are alternately arranged at the same depth. When setting the width, length, thickness, and material of the reinforcing plate 20, in addition to the total cross-sectional area of the reinforcing plates 20, 20 and the total cross-sectional secondary moment of the reinforcing plates 20, 20, the steel sheet piles 10, 10 As the stress generated at the longitudinal joints, the secondary moment of the cross section of the entire combination of the longitudinal joints where the reinforcing plates 20 and 20 are attached and the steel sheet pile body 11 that does not include the longitudinal joints is subjected to the external force. The stress generated according to the distance from the neutral axis na to each part of the reinforcing plates 20, 20 with respect to the bending moment is set to be less than a predetermined allowable stress according to the material of the reinforcing plates 20, 20.

In the welded portion between the reinforcing plates 20, 20 and the arm portion 15 of the steel sheet pile 10, the weld volume (=weld length (L ) x leg length (s)). Since the length of fixing to the steel sheet pile 10 on one side of the two steel sheet piles 10, 10 is the welding length, when using the rectangular reinforcing plate 20, "welding length = reinforcing plate width + reinforcing plate length". Become.

As for the position where the reinforcing plate 20 is attached to the arm portion 15, if the welding work can be performed only from one side due to the scaffolding conditions and interference with surrounding structures, as shown in FIGS. A reinforcing plate 20 is attached only to one side 15a or one side 15b. By doing so, the installation position of the welding machine need only be installed on one side of the arm portion 15, and the setup work for welding can be reduced.

In addition, when the reinforcing plate 20 is welded only to one side 15a or one side 15b of the arm portion 15, if welding can be performed on either side, the geometrical moment of inertia of the reinforcing plate 20 around the neutral axis na can be increased. 3, it is preferable to attach a reinforcing plate 20 to one side 15a of the arm portion 15 farther from the neutral axis na. In this case, compared to the case where the reinforcing plate 20 is attached to the one side 15b of the arm portion 15 closer to the neutral axis na, the reinforcing plate 20 attached to the one side 15a of the arm portion 15 farther from the neutral axis na is In order to secure the same geometrical moment of inertia necessary for the reinforced portion, the plate thickness of the reinforcing plate 20 can be reduced, and the steel material weight of the reinforcing plate 20 can be reduced.

Further, as shown in FIG. 5, the reinforcing plate 20 may be attached to both surfaces 15a and 15b of the arm portion 15. FIG. By attaching the reinforcing plates 20 to both surfaces 15a and 15b of the arm portion 15 in this manner, the load to be borne by the reinforcing plates 20 is dispersed, and the required cross-sectional dimensions can be efficiently secured at the reinforced portions. By attaching the reinforcing plate 20 also to the one surface 15b of the arm portion 15 closer to the neutral axis na than the case where the reinforcing plate 20 is attached only to the one surface 15a of the arm portion 15 farther from the neutral axis na, the neutral axis The plate thickness of the reinforcing plate 20 attached to the one surface 15a of the arm portion 15 on the far side from na is reduced, and the edge stress of the reinforcing plate 20 against the bending moment can be reduced. Therefore, the total welding volume of the welding points between the reinforcing plate 20 and the arm portion 15 can be reduced, leading to a reduction in the cost of welding materials. In addition, by attaching the reinforcing plate 20 to both surfaces 15a and 15b of the arm portion 15, the welding length can be increased more efficiently than when only one reinforcing plate 20 is used. (t), reinforcing plate width (bp), and reinforcing plate length (lp) can be reduced, and the steel weight of the entire reinforcing plate can be reduced (see Table 1).

As the distance from the weld defect (cross-sectional defect) portion of the joint portion 12 to which the reinforcing plate 20 is attached, a distance is secured so that the joint portion 12 is not deformed due to the welding heat. Depending on the shape of the joint and the amount of welding heat input, it is preferable that the reinforcing plate 20 is separated from the joint fitting center of the joint 12 by about 40 to 60 mm depending on the size of the joint 12 . When welding the reinforcing plate 20 to the arm portion 15, the amount of heat input is adjusted based on the leg length and welding speed of fillet welding.

When the reinforcing plate 20 is attached to both surfaces 15a and 15b of the arm portion 15, as shown in FIG. The mounting positions of the reinforcing plates 20, 20 on both surfaces 15a, 15b of the arm portion 15 may be shifted in the width direction of the steel sheet pile so as not to cause a decrease.
Further, as shown in FIG. 7, the reinforcing plate 20 is divided into a plurality of pieces (for example, two pieces) in the width direction of the reinforcing plate to form divided pieces 20a, 20a. By shortening by half, a longer welding length of the reinforcing plate 20 can be ensured at the split point, so the length of the reinforcing plate 20 can be shortened, and the weight of the entire reinforcing plate can be reduced. .

Next, Table 1 shows the specifications of the reinforcing plate of the hat-shaped steel sheet pile 50H (material SYW295) when longitudinal jointing is performed and the reinforcing plate is welded to the arm portion.
The hat-shaped steel sheet pile 50H has an effective width of 900 mm, an effective height of 370 mm, a thickness of 17 mm, a cross-sectional area of 212.7 cm ² and a moment of inertia of 46.000 cm ⁴ .
In addition, when specifying the specifications of the reinforcing plate according to the present invention, the size of the cross-sectional defect that is not welded at the joint, and the allowable stress of steel sheet piles, reinforcing plates, and fillet welding are the same as the conventional specifications. do. The width and length dimensions of the reinforcing plate shown in Table 1 are rounded up to the nearest 10 mm in consideration of ease of manufacture.

SM490 and SM570, which are the materials of the reinforcing material, are specified in rolled steel plates for welded structures (JISG 3106).
As is clear from Table 1, when the reinforcing plate is attached to the arm of the hat-shaped steel sheet pile by welding, it is better to attach the reinforcing plate to one side of the arm that is farther from the neutral axis than to attach the reinforcing plate to one side of the arm that is closer to the neutral axis. It can be seen that the weight of the entire reinforcing plate, the welding length, and the welding volume are smaller than when the reinforcing plate is attached. Also, it can be seen that the weight of the entire reinforcing plate, the welding length, and the welding volume are smaller when the reinforcing plate is attached to both sides of the arm portion than when the reinforcing plate is attached to one side of the arm portion.

When a bending moment acts on the longitudinal joints of the steel sheet piles spliced as described above, and a tensile load acts on the arm side of the steel sheet pile cross section, that is, on the cross-sectional defect of the joint, when the bending moment increases, the steel In the sheet pile width direction, cracks may occur from the weld toes of the arms, which are the weld ends of the butt joints of the longitudinal joints. A further increase in bending moment may cause cracks to propagate into the reinforcing plate. Once the crack penetrates the reinforcing plate, the reduction in yield strength becomes significant.

Therefore, it is effective to increase the plate thickness of the entire reinforcing plate in order to suppress the propagation of cracks to the reinforcing plate. Therefore, as shown in FIGS. A tandem structure of steel sheet piles 10 having reinforcing plates 20 attached to 15a and 15b is preferable.
For example, as shown in Table 1, the total thickness of the reinforcing plate when the reinforcing plate is attached to both sides of the arm is 16 mm + 12 mm = 28 mm, whereas one side of the arm (the side far from the neutral axis) ) has a thickness of 19 mm, and the thickness of the reinforcing plate attached to the other side of the arm (the side closer to the neutral axis) is 22 mm. Since the plate thickness of the entire reinforcing plate is thicker, crack propagation to the reinforcing plate can be more effectively suppressed.

Further, as shown in FIG. 8A, a plate material 21 is added to the reinforcing plate 20, or as shown in FIG. It is also effective to locally increase the plate thickness of the reinforcing plate 20 by attaching the reinforcing plate 26 to the arm portion 15 by welding at the location where the crack progresses to the reinforcing plate 20 .
In the longitudinal joint structure of steel sheet piles shown in FIG. are attached by welding or the like. The surface of the plate member 21 facing the joint portion 12 side is flush with the surface of the reinforcing plate 20 facing the joint portion 12 side. Further, the plate width of the plate member 21 is smaller than the plate width (bp) of the reinforcing plate 20, and the length of the plate member 21 is equal to the length of the reinforcing plate 20 (lp). By adding the plate member 21 to the reinforcing plate 20, the plate thickness of the reinforcing plate can be locally increased at the location where crack propagation to the reinforcing plate 20 starts. Note that the reinforcing plate 20 and the plate material 21 may be integrally formed.

In the steel sheet pile tandem structure shown in FIG. 8B, a reinforcing plate 26 made of a tapered steel plate is attached by welding to one side 15a of the arm portion 15 on the far side from the neutral axis na. The reinforcing plate 26 has a tapered surface such that the plate thickness increases toward the joint portion 12 side, and the thickness of one end portion of the reinforcing plate 26 on the joint portion 12 side is equal to the thickness of the reinforcing plate 20. The thickness of the other end of the reinforcing plate 26 is smaller than the thickness of the one end and is substantially equal to or smaller than the thickness of the reinforcing plate 20 .
Further, the width and length of the reinforcing plate 26 are equal to the width and length of the reinforcing plate 20 .
In this manner, by locally increasing the plate thickness of the reinforcing plates 20 and 26 at locations that are starting points for crack propagation to the reinforcing plates, crack propagation to the reinforcing plates 20 and 26 can be suppressed.

In addition, as shown in FIG. 9, before the crack propagates to the reinforcing plate 20, in order to suppress the occurrence of cracks at the weld toe portions of the arm portions 15, which are both ends of the longitudinal butt welding, the joint portion 12 The auxiliary member 25 may be attached to the by welding.
In order to ensure the fitability of the joint portion 12 and prevent the occurrence of a gap between the upper and lower steel sheet piles 10 at the weld defect (section defect) of the joint portion 12, the width direction of the steel sheet pile 10 It is effective to attach the auxiliary member 25 to the bottom surface of the joint portion 12 near the end. As the auxiliary member 25, a plate material or a rod-shaped member is used. When the auxiliary member 25 is welded to the joint portion 12, if excessive heat input is applied, the joint portion 12 is deformed. Therefore, it is preferable to perform welding while controlling the amount of heat input.

As described above, according to the present embodiment, the total cross-sectional area of the reinforcing plates 20, 20 in the cross section of the longitudinal connection line 16 of the steel sheet piles 10, 10 corresponds to the joint portions 12, 12 that are not welded. Since the total cross-sectional area of the missing portion is greater than or equal to the total cross-sectional area of the missing portion, the yield strength of the longitudinal joint portion is greater than the steel sheet pile base material (longitudinal equivalent to or better than steel sheet piles without joints).
In addition, with respect to the neutral axis na of the steel sheet pile cross section of the steel sheet pile 10, the total cross-sectional secondary moment of the reinforcing plates 20, 20 in the cross section at the longitudinal connection line 16 is the cross section corresponding to the joint portions 12, 12 that are not welded. Since it is equal to or greater than the total geometrical moment of inertia of the missing portion, the cross-sectional loss of the joint portions 12, 12 can be compensated for, and the bending rigidity of the steel sheet piles 10, 10 can be ensured.
Furthermore, since the reinforcing plates 20 and 20 having a geometrical moment of inertia corresponding to the weld loss (cross-sectional loss) of the joints 12 and 12 with respect to the neutral axis na of the steel sheet pile body 11 are used, the neutral axis of the longitudinal joint is A predetermined proof stress or The entire cross-section of steel sheet piles can be efficiently utilized to ensure rigidity.
Furthermore, the reinforcing plate 20 is attached only to the arm portions 15 on both sides of the steel sheet pile 10 .
Therefore, while ensuring the necessary yield strength at the tandem joints 12, 12 having a cross-sectional area defect, the weight is large, the cost and workability are adversely affected, and the welding management of the tandem butt portions is hindered. It is possible to eliminate the need for 13 reinforcing plates 20 and provide a tandem structure of steel sheet piles having the minimum number of reinforcing plates 20 required.

Also, by eliminating the need for a large reinforcing plate to be attached to the web 13, the material cost of the reinforcing plate and welding material can be reduced, and the shortened welding time can reduce the material and construction cost of the entire steel sheet pile construction. In particular, when the construction space is narrow, such as when constructing under the girder of a bridge, it is necessary to use many short steel sheet piles and the number of longitudinal joints increases. the effect becomes more pronounced.
In addition, since the reinforcing plates 20 and 26 are only small plate members to be attached to the arm portion 15, the welding work is labor-saving. Furthermore, by reducing the number of welding points and the amount of welding on-site, on-site management becomes easier and welding quality can be easily secured.

Further, when welding the butt portions of the upper and lower steel sheet piles 10, 10, in order to ensure full cross-section welding, after welding from one side, the weld surface on the opposite side is scraped by gouging in order to remove the poor penetration portion. It is necessary to perform welding after welding, or perform Uranami welding to ensure that the deposited metal is also filled on the other side, which is time-consuming. However, in an actual site, in order to facilitate the work of installing and aligning the upper steel sheet pile 10 on the lower steel sheet pile 10, a reinforcing plate is first attached to the web of the lower steel sheet pile head. Therefore, the upper steel sheet pile 10 may be erected, and the welded part of the butt part of the longitudinal joint is covered with the reinforcing plate, and it may be scraped by gouging or it may not be possible to confirm the Uranami weld. I have something to do. In particular, the reinforcement plate attached to the web 13, which has a large width at the longitudinal joint, has a large area that covers the butt part, and if by any chance the full cross-section welding is not performed reliably, the influence of the yield strength reduction on the entire longitudinal joint will occur. To make it possible to surely confirm that full cross-section welding is performed on the web line over the entire length by eliminating a large reinforcing plate attached to the web 13, although it becomes large, and to facilitate welding management of the butt part. can be done.
Further, since it is not necessary to attach a reinforcing plate to the web 13, when the steel sheet pile 10 needs to be coated with a heavy anti-corrosion coating, the web 13 can be easily coated with a heavy anti-corrosion coating while avoiding interference with the coating range of the heavy anti-corrosion coating.

In addition, since the plate thickness of the reinforcing plate 20 and the reinforcing plate 26 to which the plate material 21 is added on the side of the joint portion 12 is thicker than the plate thickness on the side opposite to the joint portion 12, crack propagation to the reinforcing plates 20 and 26 can be suppressed. .
Furthermore, since the auxiliary member 25 is fixed between the joints 12, 12 so as to straddle the longitudinal joint line 16, the longitudinal joint butt portion can be removed before the crack develops to the reinforcing plate 20 as described above. It is possible to suppress the occurrence of cracks at the weld toe portions of the arm portion 15, which are the welded end portions of the arm portion 15.

FIG. 10 is for explaining the first modification of the reinforcing plate, (a) is a perspective view showing the main part of the longitudinal joint structure of the steel sheet pile when the reinforcing plate 27 of the first modification is attached, ( b) It is a cross-sectional view of the main part.
FIG. 11 is for explaining a second modification of the reinforcing plate, and FIG. 11(a) is a perspective view showing a main part of a longitudinal joint structure of steel sheet piles when the reinforcing plate 28 of the second modification is attached. , (b) is a cross-sectional view of the main part thereof.

Although the reinforcing plate 20 described above is a rectangular flat plate and the reinforcing plate 26 is made of a tapered steel plate, the reinforcing plate 27 shown in FIG. , is formed to have a substantially semicircular cross section.
In addition, both the reinforcing plate 27 and the reinforcing plate 28 satisfy all the conditions (1) to (4) described above, and the longitudinal connection line 16 is connected to the arm portions 15, 15 of the upper and lower steel sheet pile bodies 11, 11. The outer periphery is joined by fillet welding so as to straddle.

The reinforcing plate 27 shown in FIG. 10 gradually decreases in plate thickness in a tapered manner along the longitudinal direction as it separates from the longitudinal joint line 16 in the longitudinal direction of the steel sheet piles 10, 10, and has the thickest plate thickness at the longitudinal center. is located on the splicing line 16 .
In this way, the thickness of the reinforcing plate 27 gradually decreases so as to taper in the longitudinal direction of the steel sheet pile 10 from the longitudinal center portion, that is, on the longitudinal joint line 16, so that when the steel sheet pile 10 is driven into the ground, The resistance from the ground received by the reinforcing plate 27 can be reduced as compared with the reinforcing plates 20 and 26 described above.

The reinforcing plate 28 shown in FIG. 11 has a plate thickness that gradually decreases in an arc shape along the longitudinal direction as it separates from the longitudinal joining line 16 of the steel sheet piles 10, 10. is located on the splicing line 16 .
In this way, the thickness of the reinforcing plate 28 gradually decreases so as to taper in the longitudinal direction of the steel sheet pile 10 from the longitudinal center portion, that is, on the longitudinal joint line 16, so that when the steel sheet pile 10 is driven into the ground, The ground resistance received by the reinforcing plate 28 can be reduced as compared with the reinforcing plates 20 and 26 described above.

FIG. 12 is for explaining a third modified example of the reinforcing plate, and is a perspective view showing a longitudinal joint structure of steel sheet piles when the reinforcing plate 30 of the third modified example is attached. Also, FIG. 13 is a front view showing a reinforcing plate 31 of a fourth modified example.
The reinforcing plate 30 of the third modified example and the reinforcing plate 31 of the fourth modified example are rhombic reinforcing plates formed in a rhombic shape. In order to secure a certain amount of weld length with the same leg length, the steel material weight of the reinforcing plate can be reduced by using a diamond shape rather than a rectangular shape. The reinforcing plate 30 of the third modified example and the reinforcing plate 31 of the fourth modified example satisfy all the conditions (1) to (4) described above, and the arm portions 15, 15 of the upper and lower steel sheet pile bodies 11, 11 The outer periphery is joined by fillet welding so as to straddle the longitudinal joint line 16 .

That is, as shown in FIG. 12, the reinforcing plate 30 of the third modified example is arranged so that a straight line 30a connecting obtuse angles of the plate surfaces facing each other coincides with the longitudinal connecting line 16. As shown in FIG. A total of two reinforcing plates 30 are attached to the arm portions 15, 15 which are vertically adjacent to each other so as to straddle the longitudinal joint line 16, one each on the left and right sides.
Also, if the welding length along the four circumferences of the reinforcing plate 30 is L, the welding length L is equal to or longer than the welding length along the four circumferences of the rectangular reinforcing plate 20. However, the area of the reinforcing plate 30 when viewed from the front is smaller than that of the reinforcing plate 20 . Further, the thickness of the reinforcing plate 30 is approximately equal to the thickness of the reinforcing plate 20 .

In addition, in the fourth modification, as shown in FIG. 13, two reinforcing plates 31, 31 are provided instead of one reinforcing plate 30, and the two reinforcing plates 31, 31 are provided on the plate surfaces thereof. The straight lines 31 a , 31 a connecting obtuse angles facing each other are arranged so as to coincide with the longitudinal connecting line 16 . The two reinforcing plates 31, 31 are joined to the arm portion by fillet welding after being placed adjacent to each other with their obtuse-angled portions facing each other.
One reinforcing plate 31 has an area of 1/4 of one reinforcing plate 30 in a front view, has a shape similar to that of the reinforcing plate 30, and has substantially the same plate thickness as that of the reinforcing plate 30. It's becoming
The total width dimension of the two reinforcing plates 31 , 31 along the longitudinal joint line 16 is equal to the width dimension of one reinforcing plate 30 along the longitudinal joint line 16 .
The two reinforcing plates 31, 31 are arranged adjacent to each other with their obtuse angle portions facing each other, but are spaced apart by a predetermined distance in the longitudinal direction of the longitudinal joint line 16 (the width direction of the steel sheet pile 10). may be placed.

The reinforcing plate 30 of the third modification has substantially the same plate thickness as the rectangular reinforcing plate 20 described above, and has a smaller area in front view than the reinforcing plate 20, but has the same length as the reinforcing plate 20 or more. of welding length is secured. Therefore, the steel sheet piles 10, 10 spliced by the reinforcing plate 20 have the same axial resistance and bending resistance, and the weight of the reinforcing plate 30 can be made smaller than that of the reinforcing plate 20. It has the advantage of reducing the overall weight of 10,10.
Further, the two reinforcing plates 31, 31 of the fourth modified example can ensure the same welding length as that of the single reinforcing plate 30, and the area in front view is half that of the single reinforcing plate 30. can be Therefore, the steel sheet piles 10, 10 longitudinally spliced by the reinforcing plate 30 have the same axial resistance and bending resistance, and the weight of the two reinforcing plates 31, 31 can be made smaller than that of the single reinforcing plate 30. Therefore, there is an advantage that the overall weight of the spliced steel sheet piles 10, 10 can be further reduced.

FIG. 14 is a front view showing a reinforcing plate of the fifth modified example.
The reinforcing plate 32 of this fifth modification is a rhombic reinforcing plate formed in a rhombic shape, and satisfies all the conditions (1) to (4) described above, and the arm portions 15 of the upper and lower steel sheet pile bodies 11, 11 , 15 by fillet welding so as to straddle the tandem line 16 thereof.
The three reinforcing plates 32 , 32 , 32 are arranged so that the straight lines 32 a , 32 a , 32 a connecting obtuse angles of the plate surfaces facing each other are aligned with the longitudinal connecting line 16 . The three reinforcing plates 32, 32, 32 are joined to the arm portion by fillet welding after being adjacently arranged with their obtuse-angled portions facing each other. The three reinforcing plates 32, 32, 32 may be arranged at predetermined intervals in the longitudinal direction of the longitudinal joint line 16 (the width direction of the steel sheet pile 10).
One reinforcing plate 32 is 1/9 the size of one reinforcing plate 30 and has a shape similar to that of the reinforcing plate 30 .
Furthermore, the total width dimension of the three reinforcing plates 32 , 32 , 32 along the longitudinal joining line 16 is equal to the width dimension of the reinforcing plate 30 along the longitudinal joining line 16 .
The three reinforcing plates 32 , 32 , 32 of the fifth modification can ensure the same welding length as that of one reinforcing plate 30 , and the area in front view is ⅓ that of one reinforcing plate 30 . can be For this reason, the steel sheet piles 10, 10 longitudinally spliced by the reinforcing plate 30 or the reinforcing plate 31 have the same axial resistance and bending resistance, and the weight of the three reinforcing plates 32, 32, 32 is reduced to one sheet. Since it can be made smaller than the reinforcing plate 30, there is an advantage that the overall weight of the spliced steel sheet piles 10, 10 can be further reduced.

If the rhombic reinforcing plates 30, 31, and 32 of the third to fifth modifications are used as they are as reinforcing plates, the number of sharp points at the corners increases, and stress concentration at the weld ends increases the risk of fatigue cracks. It is feared that there will be an increase in Therefore, it is possible to avoid stress concentration by making the acute-angled portion into a gentle curve, as in the reinforcing plate 33 of the sixth modified example shown in FIG.
In the case of the reinforcing plate 33 in the sixth modification, that is, the reinforcing plate in which the acute-angled portions of the rhombus-shaped reinforcing plate are formed by smooth curved surfaces, the acute-angled portions at both ends of the rhomboidal steel sheet pile material in the axial direction are gently curved. If the following formula (1) is satisfied for the rhombic outer peripheral inclination angle (θ) with respect to the tangential line, the shear strength of the fillet weld can be secured, and the outer peripheral length of the reinforcing plate can be shortened and the steel weight can be reduced. .

As shown in FIG. 16, the total weld length is shortened when the acute-angled line (portion of length c) is replaced with the curved portion (portion of width d) at the acute-angled point of the rhombus of reinforcing plate 33 . However, with respect to the tensile load (P), the component force acting on each weld is different, and the stress generated in the weld is different for each part. ), the total resistance can be made equal or greater.
As shown in FIG. 17, the force component for a tensile load P in an arbitrary direction with respect to the fillet weld is as follows.
X-direction force component: T = Psin θ
Y-direction force component: Ncosα=Pcosθ・cosα
Z direction force component: Nsinα=P cos θ・sinα

When the throat thickness of the fillet weld is a and the weld length is e, the stress acting on the throat section is as follows.
X-direction stress: τ _T = (P/ae) sin θ
Y-direction stress: τ _N = (P / ae) cos θ · cos α
z-direction stress: σ _N = (P/ae) cos θ · sin α

Based on the theory of shear strain energy, from the experimental result that the fracture stress of simple shear is 0.75 times the fracture stress of simple tension, the sum of the stress components in each direction is determined as the condition for fracture at the fillet weld. The following equation is generally shown as the relational expression of .

よって、荷重Ｐに対して、ある方向の溶接断面に発生する応力ｐ_０は以下のようになる。

Therefore, the stress _p0 generated in the weld cross section in a certain direction with respect to the load P is as follows.

曲線部における抵抗力Ｒ_ｄは、曲線部におけるのど厚をａ_ｄとし、引張荷重に対して直交する縦継ラインと平行な部分へ投影して近似すると、以下のように求められる。
Ｒ_ｄ＝０．８５σ_Ｐ・ａ_ｄ×ｄ
ここで、Ｒ_ｄ≧Ｒ_Ｃであれば、鋭角ラインを曲線部に置換しても、隅肉溶接部における引張荷重Ｐに対する抵抗力が縮小することなく、合計の溶接長を削減できる。鋭角ラインと曲線部の関係として、
２Ｃ・ｃｏｓθ＝ｄが成り立つことから、以下の式を満足させることが条件となる。

The resistance R _C of the acute-angled line of the rhombus is obtained as follows by setting the throat thickness of the acute-angled line to a _C and substituting α=45° into the above equation.

The resistance _Rd at the curved portion can be obtained as follows by approximating the throat thickness at the curved portion as ad and projecting it onto a portion parallel to the longitudinal _connection line perpendicular to the tensile load.
R _d =0.85σ _P ·a _d ×d
Here, if R _d ≧R _C , the total weld length can be reduced without reducing the resistance to the tensile load P at the fillet weld even if the sharp-angled line is replaced with the curved portion. As the relationship between the acute angle line and the curved part,
Since 2C·cos θ=d is established, it is a condition that the following expression is satisfied.

As for the curvature of the curved line, it is possible to smooth the flow of stress by making the curvature gentler than the curvature at which the rhombic straight line is tangent to the curved line at the intersection of the rhomboidal straight line and the curved line.
For example, if the throat thickness at the curved portion is 10 mm and the throat thickness at the acute-angled line is 6 mm, as shown in FIG. It is possible to ensure resistance to force.

As in the reinforcing plate 33 of the sixth modification, it is possible to avoid stress concentration by making the acute-angled portion a gentle curve, but as shown in FIG. You can make it elliptical and eliminate sharp points. If the welding leg length is not increased while the welding length is shortened by the curved shape, the amount of welding will be insufficient. Therefore, as shown in FIGS. The number of welding points may be increased by providing circular holes 33a and 34a penetrating through.
In this case, the total welding length obtained by adding the welding length along the edges of the holes 33a and 34a to the welding length of the outer circumference of the reinforcing plate 33 or 34 is set to be equal to or greater than the welding length of the outer circumference of the reinforcing plate 30.

In the reinforcing plate 33 of the sixth modification, since the acute-angled portion is formed by a smooth curved surface, the reinforcing plate 33 can By welding along the edge of the hole 33a provided in the hole 33a, the total weld length, which is the weld length along the edge of the hole 33a plus the outer circumference weld length of the reinforcing plate 33, is greater than or equal to the outer circumference weld length of the reinforcing plate 30. By welding the reinforcing plate 33 to the arm portion 15 of the steel sheet pile main body 11 so as to have a sufficient welding amount, the necessary yield strength can be ensured.

In addition, in the reinforcing plate in which the acute-angled portion of the rhombus-shaped reinforcing plate is formed by a smooth curved surface, when the acute-angled portions at both ends of the rhombic-shaped steel sheet pile material in the axial direction are gently curved, the outer circumference of the rhombus with respect to the longitudinal connection line If the inclination angle (θ) satisfies the above formula (1), the shear strength of the fillet weld can be secured, and the outer circumference of the reinforcing plate can be shortened, thereby reducing the steel weight.

FIGS. 20A to 20E are front views showing reinforcing plates of eighth to twelfth modifications, respectively.
The reinforcing plates 35 to 39 in such eighth to twelfth modifications also satisfy all the conditions (1) to (4) described above, and the reinforcing plates 35 to 39 are the arms of the upper and lower steel sheet pile bodies 11 and 11, respectively. The outer circumferences of the portions 15, 15 are joined by fillet welding so as to straddle the longitudinal joint line 16. - 特許庁

In addition, in the reinforcing plates 35 to 39 in the eighth to twelfth modifications, by providing a notch portion inward from the outer peripheral line of the reinforcing plate 30, the total outer peripheral length of each of the reinforcing plates 35 to 39 is , It is possible to reduce the weight of the steel material by reducing the cross-sectional area compared to the rhombus while securing the length of the reinforcing plate 30 and the outer circumference of one sheet, thereby reducing the material cost, improving the work efficiency, and increasing the construction speed. can bring about improvement.

Further, in the reinforcing plate 38 of the eleventh modified example, circular holes 38a, 38a are provided through the reinforcing plate 38 in the thickness direction. The added total weld length is greater than or equal to the outer circumference weld length of the reinforcing plate 30 .
By thus providing the holes 38a, 38a inside the reinforcing plate 38, the weight of the reinforcing plate 38 is reduced. These holes 38a, 38a can be used as a gripping portion during transportation, and when the amount of welding is insufficient only by welding on the outer periphery, the amount of welding can be secured by welding along the holes 38a, 38a, and the necessary strength can be secured. .

Further, in the reinforcing plate 39 of the twelfth modified example, two triangular holes 39a, 39a are provided in order to reduce the weight of the reinforcing plate 39. As shown in FIG. The two holes 39a, 39a are formed in the shape of an isosceles triangle, and by aligning the sides opposite to the apex angles of the holes 39a and 39a, a rhombic shape similar to the outer shape of the rhombus is formed.
The positions of the reinforcing plates 38 and 39, the holes 38a and 38a, and the holes 39a and 39a in the eleventh and twelfth modifications are the vertical positions in order to ensure the tensile strength of the reinforcing plates 38 and 39 at the longitudinal joint line 16. In order to secure the shear strength between the holes 38a, 38a and between the holes 39a, 39a located on both sides of the joint line 16, the distance f from the longitudinal joint line 16 to the edges of the holes 38a, 39a is set by the reinforcing plate 38. , 39 is secured. Assuming that two shear failure surfaces are formed between the holes 38a and 38a and between the holes 39a and 39a on both sides of the tether line 16 in the reinforcing plates 38 and 39, the shear strength is In order to achieve a tensile strength of 16 or more, it is necessary to satisfy the following equation.

これを式変形すると以下のようになる。

If this formula is transformed, it becomes as follows.

In addition, in the eighth to tenth modifications, even when a notch portion is provided inward from the rhombic outer peripheral line, the distance from the above formula should be secured as the distance from the longitudinal connecting line 16 to the nearest point of the notch portion. is preferred.

In the present embodiment, the case where the present invention is applied to a spliced structure in which the hat-shaped steel sheet piles 10, 10 are longitudinally spliced has been described as an example. As an embodiment of , it can also be applied to a tandem structure in which a U-shaped steel sheet pile 40 as shown in FIG. 21 and a Z-shaped steel sheet pile 50 as shown in FIG. 22 are spliced.

The U-shaped steel sheet pile 40, as shown in FIG. and a flange portion 44 formed at the end.
When longitudinally joining such a U-shaped steel sheet pile 40 , the reinforcing plate 20 is attached to the flange portion 44 of the steel sheet pile body 41 . The reinforcing plate 20 is preferably attached to the tip of the flange portion 44 , that is, in the vicinity of the joint portion 42 . Further, the reinforcing plate 20 may be attached to the outer surface facing the outside of the flange portion 44, the inner surface facing the inside, or both the outer surface and the inner surface.
Further, instead of the reinforcing plate 20, the reinforcing plates 26 to 28 and 30 to 39 described above, or the plate member 21 and the auxiliary member 25 may be attached to these reinforcing plates.

The Z-shaped steel sheet pile 50, as shown in FIG. It has a web 53 arranged on the rim and flanges 54, 54 formed on both side ends thereof.
When longitudinally joining such a Z-shaped steel sheet pile 50 , the reinforcing plate 20 is attached to the flange portion 54 of the steel sheet pile body 51 . The reinforcing plate 20 is preferably attached to the tip of the flange portion 54 , that is, in the vicinity of the joint portion 52 . Further, the reinforcing plate 20 may be attached to the surface of the flange portion 54 facing the web, the surface facing away from the web, or both surfaces.
Further, instead of the reinforcing plate 20, the reinforcing plates 26 to 28 and 30 to 39 described above, or the plate member 21 and the auxiliary member 25 may be attached to these reinforcing plates.

Reference Signs List 10, 40, 50 Steel sheet pile 11, 41, 51 Steel sheet pile body 12, 42, 52 Joint portion 13, 43, 53 Web 14, 44, 54 Flange 15 Arm portion 16 Longitudinal connection line 20, 26, 27, 28, 30 ~39 Reinforcing plate 21 Plate material 25 Auxiliary member na Neutral shaft

Claims (7)

A longitudinal joint structure of steel sheet piles for connecting steel sheet piles having a steel sheet pile main body and a joint part in the material axial direction,
At least part of the steel sheet pile bodies are joined by full-section welding, and the joint portions are not welded together,
A reinforcing plate is welded between the steel sheet piles so as to straddle the longitudinal connection line,
The steel sheet pile tandem structure characterized in that the reinforcing plate satisfies all of the following conditions (1) to (3).
(1) The reinforcing plate is attached only to the steel sheet pile portion other than the web at the center portion in the width direction of the steel sheet pile body.
(2) The total cross-sectional area of the reinforcing plate in the cross section of the longitudinal connection line is equal to or greater than the total cross-sectional area of the cross-sectional missing portions of the steel sheet piles where the steel sheet piles are not fully cross-sectionally welded to each other.
(3) The total geometrical moment of inertia of the reinforcing plate in the cross section of the longitudinal connection line with respect to the neutral axis of the steel sheet pile cross section of the steel sheet pile is equal to or greater than the total geometrical moment of inertia of the missing section portion. The steel sheet pile body has a web, a pair of flanges formed on both side ends of the web, and a pair of arms formed on the outer side ends of the pair of flanges. and a pair of joint portions formed at the outer side ends of the pair of arm portions, respectively.
The tandem structure of steel sheet piles according to claim 1, wherein the reinforcing plate is attached only to the arm portion. 3. The tandem structure of steel sheet piles according to claim 2, wherein the reinforcing plate is attached to at least one of the two surfaces of the arm portion that is farther from the neutral axis. The tandem structure of steel sheet piles according to claim 3, wherein the reinforcing plates are attached to both surfaces of the arm portion. The tandem structure of steel sheet piles according to any one of claims 1 to 4, wherein the thickness of the reinforcing plate on the side of the joint portion is thicker than the thickness of the side opposite to the joint portion. 6. The tandem structure of steel sheet piles according to claim 5, wherein the plate thickness of the reinforcing plate increases toward the joint portion. The tandem structure of steel sheet piles according to any one of claims 1 to 6, wherein an auxiliary member is fixed between the joint portions so as to straddle the tandem line.

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