JP2020020128A - Steel plate floor - Google Patents

Abstract

To provide a steel plate floor capable of space-saving by suppressing the height of a lateral rib.SOLUTION: At least one of a longitudinal rib 12 and a lateral rib 13 of a steel plate floor 10 has a plate surface extending in a lengthwise direction and a direction orthogonal to the lengthwise direction, being formed of an anisotropic steel plate in which the Young's modulus differs between a first direction on the plate surface and a second direction orthogonal to the first direction, and the Young's modulus in the first direction is set higher than the Young's modulus in the second direction. Since the longitudinal rib 12 has its first direction oriented in the bridge axis direction when the longitudinal rib 12 is formed of the anisotropic steel plate and the transverse rib 13 has its second direction oriented in the vertical direction when the transverse rib 13 is formed of the anisotropic steel plate, space-saving is possible by reducing the web height of the transverse rib 13.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a steel slab for a bridge.

  Demand for steel slabs for bridges is increasing especially in the infrastructure renewal market due to their light weight and rapid construction. As an example of a steel floor slab, the one described in Patent Document 1 is known. The steel deck includes a deck plate, a flat longitudinal rib joined to the lower surface of the deck plate and extending in the bridge axis direction, and a longitudinally extending bridge axis perpendicular to the bridge axis direction. And horizontal ribs arranged orthogonally to the ribs. The transverse rib has a web joined to the lower surface of the deck plate, and a lower flange joined to the lower end of the web. The vertical rib is inserted into a notch formed at the upper end of the web of the horizontal rib, and the edge of the notch of the horizontal rib and the vertical rib are joined by turn welding.

In such a steel floor slab, by setting the web of the horizontal ribs high, a portion where a fatigue crack is generated from the toe on the web side at the weld portion of the turn welding that joins the vertical rib and the horizontal rib crossing each other. The local stress in can be reduced efficiently.

Japanese Patent No. 6072946

  In order to reduce the local stress at the place where the fatigue crack occurs in this way, that is, when the web height of the transverse rib is increased from, for example, a standard 500 mm to 600 mm in order to secure the fatigue durability, Since the height of the steel slab itself (up and down dimensions) increases, it goes against the need to reduce the girder height of the entire bridge, especially for small and medium-sized bridges, and the height of the horizontal ribs reduces the space required for the steel slab. Hindering, resulting in a low girder height barrier.

By the way, in the steel slab, at the intersection (weld portion) of the vertical rib and the horizontal rib, the vertical rib and the horizontal rib restrain each other's deformation, and as a result, additional stress is generated. In such an intersection, there is a possibility that the generated stress can be reduced by changing the rigidity of the member. For example, a horizontal rib restrained by the deformation of the vertical rib and forcibly deformed generates locally high stress at the joint with the vertical rib, so that locally high stress is generated. It is considered that by lowering the rigidity (making it easier to deform), the area to be deformed can be expanded, and local stress concentration can be reduced. However, in order to change the rigidity of the lateral ribs, there is a concern that the processing cost will increase due to the additional processing, and the strength as a structural member will decrease due to a decrease in the plate thickness.
On the other hand, there has been developed a steel sheet having a Young's modulus different from that of a normal steel sheet, that is, an anisotropic steel sheet in which the Young's modulus in a specific direction is increased while the Young's modulus in a direction orthogonal to the specific direction is reduced. This anisotropic steel plate was developed with the primary aim of increasing the rigidity associated with increasing the Young's modulus in a specific direction. The member is formed by using the direction as follows. Therefore, in a member in a simple deformed state (for example, a girder that resists a vertical load), the deformation is suppressed by utilizing the property of a high Young's modulus. Is suppressed, but the generated stress itself remains unchanged.

In such a situation, as a result of the inventors' earnest research, in order to reduce the local stress generated at the intersection of the vertical ribs and the horizontal ribs and to lower the height of the bridge, a plurality of members were found. In places where the generated stress is determined by constraining each other's deformation, it has been found that the generated stress can be controlled by applying an anisotropic steel plate and changing the rigidity of the member. If the stress generated at the intersection between the vertical ribs and the horizontal ribs can be reduced, the height of the horizontal ribs can be reduced and the space can be reduced, thereby reducing the height of the girder while suppressing the occurrence of fatigue cracks. I came to the conclusion that I can do it.
The present invention has been made in view of the above circumstances, and stably suppresses the occurrence of fatigue cracks at the intersections of vertical ribs and horizontal ribs, while suppressing the height of the horizontal ribs. It is an object of the present invention to provide a steel slab capable of increasing space.

In order to achieve the above object, a steel slab of the present invention is a steel plate comprising a vertical rib extending in a bridge axis direction and a horizontal rib extending in a direction perpendicular to the bridge axis and crossing the vertical rib to support a deck plate. A floor slab,
The transverse ribs have different Young's moduli in a first direction on a plate surface and a second direction orthogonal to the first direction, and have a different Young's modulus in the first direction than the Young's modulus in the second direction. Formed by anisotropic steel sheet,
The lateral rib is characterized in that the second direction is oriented in a vertical direction.

Further, the steel slab of the present invention is a steel slab that supports a deck plate with vertical ribs extending in the bridge axis direction and horizontal ribs extending in the bridge axis orthogonal direction and intersecting with the vertical ribs,
The vertical ribs have different Young's moduli in a first direction on a plate surface and a second direction orthogonal to the first direction, and have a different Young's modulus in the first direction than the Young's modulus in the second direction. Formed by anisotropic steel sheet,
The vertical rib is characterized in that the first direction is directed to a bridge axis direction.

Here, at the intersection where the vertical rib and the horizontal rib intersect, the vertical rib bends and deforms in the vertical direction due to the traffic load, and the horizontal rib is moved out of the plane (in the bridge axis direction) so as to be dragged by the deformed vertical rib. ) Can be considered. The amount of out-of-plane deformation of the horizontal ribs and the amount of vertical bending strain caused by the deformation are determined by the amount of deformation of the vertical ribs, that is, the flexural rigidity of the vertical ribs. Relatively insensitive to Therefore, in the vertical direction of the transverse ribs, the Young's modulus under the condition of constant strain is reduced by arranging an anisotropic steel sheet so that the Young's modulus is low, and the product of the strain and the Young's modulus is thereby reduced. The stress generated in the lateral ribs, which is mainly determined by the above, can be reduced.
In addition, by arranging an anisotropic steel plate as the vertical rib so as to increase its flexural rigidity, the amount of the vertical rib dragging the horizontal rib in the out-of-plane direction is reduced. Is reduced, and as a result, the generated stress of the lateral rib can be reduced.

Therefore, in the present invention, when the vertical ribs are formed of an anisotropic steel plate, the first direction having a high Young's modulus is directed to the bridge axis direction, and the horizontal ribs are formed of the anisotropic steel plate. In the case of the horizontal rib, the second direction in which the Young's modulus is low is directed to the vertical direction in the horizontal rib, so that the stress generated at the intersection of the vertical rib and the horizontal rib can be reduced.
Thereby, the height of the horizontal ribs can be suppressed while suppressing the occurrence of fatigue cracks at the intersections between the vertical ribs and the horizontal ribs, so that the space required for the steel slab can be reduced.

Also, since the transverse ribs are set to have a low Young's modulus in the vertical direction, even if the longitudinal ribs are not anisotropic steel plates (ordinary steel), even if the transverse ribs are at intersections between the webs and the longitudinal ribs. The generated stress can be reduced, whereby the height of the lateral rib can be suppressed while suppressing the occurrence of fatigue cracks.
Further, since the longitudinal ribs are set to have a high Young's modulus in the bridge axis direction, the flexural rigidity of the longitudinal ribs increases, and the amount of the longitudinal ribs dragging the horizontal ribs in the out-of-plane direction is reduced. Thereby, even when the transverse rib is not an anisotropic steel plate (normal steel), the out-of-plane bending stress of the transverse rib can be reduced, and as a result, the transverse rib is generated at the intersection of the web and the longitudinal rib. Since the stress can be reduced, the height of the lateral rib can be suppressed while suppressing the occurrence of fatigue cracks.

Further, in the configuration of the present invention, when the vertical ribs are formed of the anisotropic steel plate, the vertical ribs have a higher Young's modulus in a first direction than ordinary steel, and the horizontal ribs have a lower modulus. When formed by an anisotropic steel plate, the transverse direction Young's modulus of the transverse rib is preferably lower than that of ordinary steel.
According to such a configuration, the stress generated at the intersection can be more effectively and stably reduced as compared with the case where the vertical ribs and the horizontal ribs are formed of ordinary steel.

  Further, in the configuration of the present invention, the vertical ribs are formed in a flat plate shape having a plate surface along the vertical direction, the horizontal ribs have a web surface along the vertical direction, and the vertical ribs are inserted. A flat web provided with a notch, and a lower flange attached to a lower end of the web, and an intersection between the vertical rib and the horizontal rib is formed by the notch in the horizontal rib. Are welded all around so as to close the gap between the edge of the vertical rib and the vertical rib.

  According to such a configuration, the intersection between the vertical rib and the horizontal rib web is formed by full circumference welding (turn welding) so as to close the gap between the edge of the notch in the horizontal rib and the vertical rib. At the intersection (weld), the local stress at the point where a fatigue crack occurs from the web-side toe can be efficiently reduced at the intersection.

  Further, in the configuration of the present invention, the horizontal ribs and the vertical ribs are formed of the anisotropic steel plate, the horizontal ribs are oriented in the second direction in the vertical direction, and the vertical ribs are aligned with the first ribs. The direction may be directed to the bridge axis direction.

  According to such a configuration, the Young's modulus in the vertical direction of the horizontal ribs is low, and the Young's modulus in the bridge axis direction of the vertical ribs is high. The fatigue durability of the intersection (weld) can be effectively secured. Thus, the stress generated at the intersection between the web of the horizontal rib and the vertical rib can be reduced, so that the space for the steel slab can be saved while suppressing the occurrence of fatigue cracks.

  ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of the fatigue crack in the intersection of a vertical rib and a horizontal rib can be suppressed stably, and since the web height of a horizontal rib can be suppressed, saving of a steel deck is possible. Space can be achieved.

It is a perspective view showing an important section of a bridge provided with a steel deck concerning an embodiment of the invention. FIG. 3 shows an intersection of a vertical rib and a horizontal rib of a steel slab according to an embodiment of the present invention, wherein (a) is a perspective view of the intersection, (b) is an enlarged view of an A circle portion in (a), (C) is a front view of the intersection, and (d) is a side view of the intersection. FIG. 4A is a view for explaining a case where the fatigue durability evaluation of the steel slab according to the present invention is performed by finite element analysis. FIG. 4A is a side view of the analysis model, and FIG. 4B is a front view of the analysis model. FIG. 3A is a diagram illustrating a double tire load model, and FIG. 3B is a diagram illustrating a loading position. (A) is an overall view of the finite element model, (b) is a front view of the finite element model, and (c) is an enlarged view of an intersection of the finite element model. It is a figure for explaining the plate thickness of the welding part of the same shell model. This is for explaining the change in the stress at the intersection due to the application of the anisotropic steel plate, and the change in the Young's modulus of each member is HS-21 (the horizontal rib web side weld toe at the intersection of the vertical rib P2 and the horizontal rib). 4 is a graph showing the effect on the stress generated in the step (). FIG. 3 shows the relationship between the horizontal rib web height and the reduction rate of the corrected hot spot stress range of HS-21, and FIG. 4A is a graph showing the relationship between the horizontal rib web height and the reduction amount of the HS-21 stress range. (B) is a diagram showing the direction of the Young's modulus of each member. FIG. 3 is a diagram for explaining changes in each stress component due to changes in the Young's modulus of each member. It is a figure which shows the change of the deformation behavior of the steel slab when the Young's modulus of each member is changed (deformation display magnification: 500).

Hereinafter, an embodiment of a steel deck according to the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view showing a main part of a road bridge 1 provided with a steel slab 10 of the present embodiment. The bridge 1 includes a steel slab 10, three main girders 20 arranged below the steel slab 10 to support the steel slab 10, and a substructure (not shown) for supporting the main girder 20. ing. The substructure is composed of foundations and columns. The main girder 20 connects the upper flange 20b on which the steel slab is placed and the lower flange disposed on the lower part, and the upper flange 20b and the lower flange having a web surface along the bridge axis direction and the vertical direction. Web 20a. The three main girders 20 extend in the bridge axis direction, respectively, and are arranged at predetermined intervals in a horizontal direction orthogonal to the bridge axis direction (bridge axis orthogonal direction).
The steel slab 10 and the main girder 20, and the main girder 20 and the substructure are joined by a fastening structure such as welding or a bolt.

The bridge 1 extends in the bridge axis direction X, and the width direction of the bridge 1 is the bridge axis orthogonal direction Z. The bridge axis orthogonal direction Z is a horizontal direction orthogonal (intersecting) to the bridge axis direction X.
The directions orthogonal to the bridge axis direction X and the bridge axis orthogonal direction Z are the vertical direction Y.

The steel slab 10 includes a deck plate 11, a plurality of vertical ribs 12 arranged below the deck plate 11 so as to extend in the bridge axis direction X, and joined to a lower surface of the deck plate 11. It has a plurality of horizontal ribs 13 extending in the axis orthogonal direction Z and intersecting with the vertical ribs 12.
The deck plate 11 is a flat plate formed of a steel plate or the like, and is arranged so that the plate surface is along the bridge axis direction X and the bridge axis orthogonal direction Z. That is, the deck plate 11 is arranged so that the plate surface extends in the horizontal direction.
The vertical ribs 12 are plate ribs formed of a band-shaped flat plate formed of a steel plate or the like, and are arranged so that the plate surface is along the bridge axis direction X and the vertical direction Y. Further, the plurality of vertical ribs 12 are arranged at predetermined intervals in the bridge axis orthogonal direction Z, and the upper end of each vertical rib 12 is joined to the lower surface of the deck plate 11 by welding or the like.

A plurality of transverse ribs 13 are arranged at predetermined intervals in the bridge axis direction X. Each transverse rib 13 has a web surface (plate surface) formed with a web 13a formed so as to be along the vertical direction Y and the bridge axis perpendicular direction Z. , And a web-shaped lower flange 13b provided at the lower end of the web 13a. The web 13a extends in the bridge axis orthogonal direction Z. The lower flange 13b extends in the bridge axis orthogonal direction Z along the extending direction of the web 13a, and a central portion of the lower flange 13b in the bridge axis perpendicular direction Z is a plate surface (upper end surface) of the lower flange 13b. And the lower end face) are substantially parallel to the bridge axis orthogonal direction Z and the bridge axis direction X.
The horizontal ribs 13 have both ends in the bridge axis orthogonal direction Z on the horizontal plane such that the lower end of the web 13a approaches the deck plate 11 as the lower end of the web 13a moves toward the outside of the steel slab 10 (both ends in the bridge axis perpendicular direction Z). The lower flange 13b is also inclined along the inclination of the lower end of the web 13a.

Further, a rectangular notch portion 14 in a front view into which the upper end including the upper flange 20b of the main girder 20 is inserted is formed at the center portion and the left and right end portions of the horizontal rib 13 in the bridge axis orthogonal direction Z. The notch 14 is formed so as to open downward by notching the lower flange 13b of the lateral rib 13 and a substantially lower half of the web 13a in the vertical direction, and the width of the notch 14 (the width in the bridge axis orthogonal direction Z). ) Is set substantially equal to or slightly larger than the width of the upper flange 20 b of the main girder 20.
The cutouts 14 formed in the center of each transverse rib 13 in the bridge axis orthogonal direction Z and near both ends are respectively arranged in a straight line in the bridge axis direction X. Is inserted from below, and the upper end surface of the upper flange 20 b of the main girder 20 is in contact with the upper edge of the notch 14.

At the upper end of the web 13a of the horizontal rib 13, as shown in FIGS. 1 and 2, the vertical rib 12 is formed so as to extend in the vertical direction Y, penetrate the web surface of the web 13a, and open upward. A plurality of notches 13d through which are inserted are formed. The width of the notch 13d (width in the direction Z perpendicular to the bridge axis) is set to be substantially equal to or slightly wider than the thickness of the vertical rib 12, and the vertical length of the notch 13d is approximately equal to the vertical length of the vertical rib 12. Or slightly wider.
One vertical rib 12 is inserted into each notch 13d formed in the web 13a of each horizontal rib 13. As a result, the web 13a of the horizontal rib 13 and the vertical rib 12 intersect so as to be substantially orthogonal to each other, and this intersecting portion forms a gap between the edge of the horizontal rib 13 and the notch 13d and the vertical rib 12. The entire circumference is welded (turn welding) so as to close the gap. The welded portion 15 formed by full circumference welding is formed in a substantially U shape, and the gap between the edge of the notch 13 d and the vertical rib 12 is closed by the welded portion 15. Here, continuous full circumference welding means that the welded portion is not spatially interrupted.
The portion of the horizontal rib 13 other than the notch 13d at the upper end of the web 13a is joined to the lower surface of the deck plate 11 by welding or the like.

In the steel slab 10 of the present embodiment, both the vertical ribs 12 and the horizontal ribs 13 are formed of an anisotropic steel plate. Here, the anisotropic steel sheet is also called a high Young's modulus steel sheet, and the Young's modulus in a first direction on the sheet surface of the steel sheet is different from the Young's modulus in a second direction orthogonal to the first direction, and A steel sheet in which the Young's modulus in the first direction is set higher than the Young's modulus in the second direction.
Further, the anisotropic steel sheet used in the steel slab 10 of the present embodiment has a Young's modulus in a first direction in which the Young's modulus is high, which is higher than the Young's modulus of ordinary steel, and in a direction in which the Young's modulus is low. The one having a Young's modulus in the second direction lower than that of ordinary steel is used. Here, ordinary steel refers to a steel sheet having no anisotropy and having a Young's modulus of about 205 GPa regardless of the direction.

  The first direction of the vertical rib 12 is oriented in the bridge axis direction X, and the second direction is oriented in the vertical direction Y. Here, the Young's modulus of the longitudinal rib 12 of the present embodiment in the first direction (bridge axis direction X) may be higher than the Young's modulus of ordinary steel, but is preferably set to be, for example, about 15% higher. . On the other hand, the Young's modulus of the vertical rib 12 in the second direction (vertical direction Y) may be lower than the Young's modulus of ordinary steel, but is preferably set to be, for example, about 15% lower.

In the horizontal rib 13, the web 13a is formed of an anisotropic steel plate, and the web 13a has a first direction oriented in the bridge axis orthogonal direction Z and a second direction oriented in the vertical direction Y. I have. Here, the Young's modulus of the web 13a of the lateral rib 13 in the second direction (vertical direction Y) in the present embodiment may be lower than the Young's modulus of ordinary steel, but may be set to be, for example, about 15% lower. preferable. On the other hand, the Young's modulus of the web 13a of the lateral rib 13 in the first direction (the direction Z orthogonal to the bridge axis) may be lower than that of ordinary steel, but is preferably set to be, for example, about 15% higher.
Note that, regarding the web 13a of the horizontal rib 13, the Young's modulus in the first direction does not need to be the same as the Young's modulus in the first direction of the vertical rib, and the Young's modulus in the second direction is the Young's modulus of the vertical rib in the second direction. The modulus does not need to be the same, and the Young's modulus may be different in both the first direction and the second direction from the first direction and the second direction of the longitudinal rib.
In FIGS. 2A to 2D, the X direction is the bridge axis direction, the Z direction is the bridge axis orthogonal direction, and the Y direction is the bridge axis direction and the vertical direction orthogonal to the bridge axis orthogonal direction.

  In the steel slab 10 having the above configuration, the webs 13a of the horizontal ribs 13 are disposed with the second direction thereof oriented in the vertical direction Y, and the Young's modulus in the vertical direction is the first direction. It is set lower than the Young's modulus. At this time, the out-of-plane deformation amount of the web 13a of the horizontal rib 13 is determined by the deformation amount of the vertical rib 12, that is, the flexural rigidity of the vertical rib 12, so that the Young's modulus of the web 13a of the horizontal rib 13 is determined. Less susceptible. Therefore, as in the present embodiment, the transverse ribs 13 are arranged such that the second direction having a smaller Young's modulus than the first direction is directed toward the vertical direction Y, so that the horizontal ribs 13 are subjected to the condition that the strain is constant in the vertical direction Y. , The stress generated in the transverse ribs, which is mainly determined by the product of the strain and the Young's modulus, can be suppressed to a small value. Therefore, the intersection between the web 13a of the transverse rib 13 and the longitudinal rib 12 ( The stress generated in the welded portion 15) can be reduced.

  In addition, since the first direction of the vertical ribs 12 having a high Young's modulus is oriented in the bridge axis direction X, the amount of the vertical ribs 12 dragging the web 13a of the horizontal ribs 13 in the out-of-plane direction is reduced. As a result, the amount of out-of-plane bending strain of the web 13a of the horizontal rib 13 can be reduced, so that the stress generated at the intersection between the web 13a of the horizontal rib 13 and the vertical rib 12, that is, the vertical rib 12 and the horizontal rib In the weld portion 15 of the web 13 with the web 13a, the local stress at the location where the fatigue crack occurs from the web-side toe can be efficiently reduced.

  Further, in the present embodiment, the web 13a of the horizontal rib 13 and the vertical rib 12 are both formed of an anisotropic steel plate, and the web 13a of the horizontal rib 13 is such that the second direction having a low Young's modulus is in the vertical direction Y. The vertical ribs 12 are oriented such that the first direction having a high Young's modulus is in the bridge axis direction X. Therefore, due to these interactions, the local stress at the point where the fatigue crack occurs from the toe on the web side is reduced more efficiently, and the occurrence of the fatigue crack at the intersection of the vertical rib and the horizontal rib is reduced. More stable deterrence can be achieved. In particular, when both the vertical ribs 12 and the horizontal ribs 13 are anisotropic steel plates as in the present embodiment, the stress at the intersection is smaller than when only the vertical ribs or only the horizontal ribs are anisotropic steel plates. Since the amount of reduction is large, it is very effective. Thereby, the fatigue durability of the intersection can be more effectively secured while suppressing the height of the horizontal rib (web). This makes it possible to more effectively secure the fatigue durability of the welded portion 15 while suppressing the height of the web 13a of the lateral rib 13, so that the space required for the steel floor slab 10 can be reduced.

  In this embodiment, the longitudinal rib 12 has a Young's modulus in the first direction higher than that of ordinary steel, while the web 13a of the lateral rib 13 has a Young's modulus in the second direction. The modulus is set lower than the Young's modulus of ordinary steel. As a result, in the case of the vertical ribs, the amount of the web 13a of the horizontal ribs 13 to be dragged in the out-of-plane direction can be reduced as compared with the webs of the vertical ribs and the horizontal ribs which are conventionally formed only of ordinary steel. The amount of out-of-plane bending strain of the web 13a of the horizontal rib 13 can be reliably reduced, and in the case of the horizontal rib, the generated stress can be reliably suppressed to a small value. As a result, the stress generated at the intersection between the web 13a of the horizontal rib 13 and the vertical rib 12 can be stably reduced, and the height of the web 13a of the horizontal rib 13 can be reliably reduced. .

In the above embodiment, both the vertical ribs 12 and the horizontal ribs 13 (the webs 13a thereof) are formed of an anisotropic steel plate, but only the vertical ribs 12 or only the horizontal ribs 13 are formed of an anisotropic steel plate. It may be. At this time, when the vertical ribs 12 are formed of an anisotropic steel plate, the first direction of the vertical ribs 12 having a high Young's modulus needs to be directed to the bridge axis direction. When the transverse rib 13 is formed of an anisotropic steel plate, the second direction in which the Young's modulus is low needs to be directed in the vertical direction.
Even when only the vertical ribs 12 are formed of an anisotropic steel plate, the amount of the vertical ribs 12 dragging the horizontal ribs 13 in the out-of-plane direction can be reduced. Thus, the stress generated at the intersection 15 between the horizontal rib 13 and the vertical rib 12 can be reduced, and the occurrence of fatigue cracks can be suppressed. Further, even when only the horizontal ribs 13 are formed of an anisotropic steel plate, as described above, the stress generated in the horizontal ribs 13 can be suppressed to a small value. The stress generated at the intersection 15 can be reduced. Thus, even when only the vertical ribs 12 or only the horizontal ribs 13 are formed of an anisotropic steel plate, the generation of fatigue cracks at the intersections 15 between the vertical ribs 12 and the horizontal ribs 13 can be stably performed. Since the web height of the horizontal ribs 12 can be suppressed, the space of the steel slab can be reduced.

Further, in the above-described embodiment, for the longitudinal ribs 12 formed of an anisotropic steel plate, the Young's modulus of the longitudinal ribs 12 in the first direction is set higher than the Young's modulus of ordinary steel. The transverse rib 13 (the web 13a) formed by the above is set such that the Young's modulus of the transverse rib 13 (the web 13a) in the second direction is lower than the Young's modulus of ordinary steel.
However, when the longitudinal ribs 12 are formed of an anisotropic steel plate, if the Young's modulus in the first direction of the longitudinal ribs 12 is higher than the Young's modulus in the second direction, the Young's modulus in the first direction is not necessarily. It does not need to be higher than the Young's modulus of ordinary steel. The Young's modulus of ordinary steel is just one of the reference Young's moduli, and the Young's modulus of the longitudinal rib 12 in the first direction is smaller than that of a non-anisotropic material having another reference Young's modulus. If the height is higher, the amount of the vertical ribs 12 dragging the horizontal ribs 13 in the out-of-plane direction can be reduced in comparison with the material, and the stress generated at the intersection 15 between the horizontal ribs 13 and the vertical ribs 12 can be reduced. Becomes possible.
In the case where the transverse ribs 13 are formed of an anisotropic steel plate, if the Young's modulus in the first direction of the transverse ribs 13 is higher than the Young's modulus in the second direction, the Young's modulus in the second direction is not necessarily required. It does not need to be lower than the Young's modulus of ordinary steel. As described above, the Young's modulus of ordinary steel is just one of the standard Young's moduli, and the Young's modulus of the transverse rib 13 in the second direction is the same as that of the other non-anisotropic materials having the Young's modulus as the standard. When the Young's modulus is lower than the Young's modulus, the stress generated at the intersection 15 between the horizontal rib 13 and the vertical rib 12 can be reduced because the generated stress of the horizontal rib 13 can be reduced in comparison with the material. Becomes possible.

Next, the fatigue durability of the steel slab according to the present invention was evaluated by finite element analysis, which will be described below.
1. Analytical Model As shown in FIG. 3, the analytical model has ten vertical ribs (indicated by reference numeral 12A) and three horizontal ribs (indicated by reference numeral 13A) having an inverted T-shaped cross section, that is, vertical ribs (indicated by reference numeral 12A). ) A partial model of a real structure including two spans, a web of horizontal ribs (indicated by reference numeral 13A) (hereinafter referred to as a horizontal rib web), a vertical rib (indicated by reference numeral 12A), and a deck plate (indicated by reference numeral 11A) The Young's modulus was varied (see Table 1). In FIG. 3, reference numeral 20A indicates a main girder, V direction indicates a vertical direction, L direction indicates a bridge axis direction, and T direction indicates a bridge axis orthogonal direction.
In FIG. 3, t = 9 indicates that the thickness of the horizontal rib web is 9 mm, and t = 12 indicates that the width dimension of the flange of the horizontal rib (indicated by reference numeral 13A) (the width dimension of the vertical rib in the longitudinal direction). 12 mm.
The rate of change of the Young's modulus in Table 1 indicates the Young's modulus (E ₁ ) in the direction perpendicular to the bridge axis (T direction) for a horizontal rib, and the bridge axis direction (L direction) for a vertical rib and a deck plate. The Young's modulus (E ₂ ) in the direction orthogonal to these, that is, in the direction of the bridge axis (L direction) in the case of a horizontal rib, and in the direction of the bridge axis (T direction) in the case of a vertical rib and a deck plate, The relation with the Young's modulus (E) of ordinary steel was set to (E ₁ + E ₂ ) / 2 = E. The Poisson's ratio in both directions was a value changed from the reference value 0.3 at the same rate of change as the Young's modulus, and the shear modulus was a constant value E / 2.6.

The Young's modulus of the vertical ribs and the horizontal rib webs were changed with the aim of reducing the stress generated when the two ribs restrained each other at the junction of the two. Since it is known that the height of the horizontal rib web affects the stress at the intersection of the vertical and horizontal ribs, the horizontal rib web height was also changed to 400, 500, and 600 mm. The change in the Young's modulus of the deck plate was aimed at increasing the load distribution from the vertical rib that bears the most load to the adjacent vertical rib, and reducing the stress at the intersection of the vertical and horizontal ribs.
The target weld to calculate the hot spot stress (the stress at the weld toe) is the intersection of the vertical rib and the horizontal rib indicated by P2 to P5 in the AA cross section in FIG. )), Paying attention to both welding toes on the horizontal rib web side and the vertical rib side at each intersection, and respectively setting them to toes 1 and 2 (see FIG. 2 (b)). It is represented by a vertical rib number and a toe number, and for example, if it is a horizontal rib web side weld toe at the intersection of the vertical rib P3 and the horizontal rib, it is called HS-31.

The first letters 4, 5, and 6 of the model name indicate the horizontal rib web heights h _T = 400, 500, and 600 mm, respectively, and the second letters indicate combinations of changes in the Young's modulus of each member.
Regarding the direction of each member, the horizontal rib indicates the direction perpendicular to the bridge axis (T direction), and the vertical rib and the deck plate indicate the bridge axis direction (L direction).
The change rate of the Young's modulus is, on the basis of 205 kN / mm ² (205 GPa), “0” when the Young's modulus is not changed, “+15” when the Young's modulus in the first direction is increased by 15%, and “−15”. "Shows a case where the Young's modulus in the first direction is reduced by 15%.

2. Load: Searching for the strictest load position due to moving load The load was a uniform pressure of 100 kN on the double tire contact surface modeled with reference to the road bridge specification (see FIG. 4 (a)).
The stress generated at the intersection of the vertical and horizontal ribs of the steel slab varies depending on the load position, while the actual traffic load may act at any position. The load position was searched, and the stress range was determined by the difference between the two stresses. The load position is the center of gravity of the model on the upper surface of the deck plate in the model plan view (the position of the intersection of diagonal lines on the upper surface of the deck plate shown in FIG. 4B; that is, as shown in FIG. 4B). L = -0, -100, -200, ..., -900, -1000 mm in the bridge axis direction, and T = -1280, -1120, ..., 1120 in the direction orthogonal to the bridge axis. , 1280 mm (see FIG. 4B). Here, the load position indicates the centroid position of the tire contact surface. Therefore, the number of load cases was 187 cases. Since the analysis model is symmetric about the intermediate horizontal rib, the analysis result when the load position is (L, T) = (a, b) is as follows: When the load position is (L, T) = (− a, b) ) Was considered to be inverted in the L-axis direction with the intermediate transverse rib as the axis.

3. Method for calculating stress The method for calculating stress is described below. First, in order to evaluate and compare the fatigue performance of the vertical and horizontal rib intersections of various shapes, a welded portion using a structural hot spot stress (hereinafter, referred to as a hot spot stress) that can take into account the stress concentration due to the joint shape. Was evaluated for stress. The hot spot stress was calculated by the following equation according to the fatigue design guidelines of the International Welding Society.

Here, σ _h on the left side indicates hot spot stress, σ on the right side indicates stress in the direction perpendicular to the weld toe on the surface of the steel sheet, the subscript indicates the distance from the toe to the stress reference point, and t indicates the thickness of the steel sheet. Equations (1a) and (1b) were used when the toe consisting of the intersection of the surface of the steel sheet and the end face of the steel sheet with the weld metal was the target.
Furthermore, considering that the fatigue strength increases when the steel sheet thickness is thin, and that when the out-of-plane bending stress acts, the fatigue strength increases compared to when the in-plane membrane stress acts. The hot spot stress was corrected by the formula. The fatigue design curve for the corrected hot spot stress (hereinafter referred to as “corrected hot spot stress”) is graded E with reference to JSSC (Japan Steel Structural Association: Fatigue Design Guidelines for Steel Structures, same commentary, Gihodo Publishing, 2012). And

ここで、左辺のσ´_ｈは補正ホットスポット応力、右辺のσ_ｈ,ｍ、σ_h,bはそれぞれホットスポット応力の膜応力、曲げ応力成分であり、σ_{h, obv}，σ_{h, rev}から算出した。σ_{h, obv}，σ_{h, rev}はそれぞれ応力を評価する対象の面を表面としたときの表面、裏面のホットスポット応力を表す。

Here, the left side of Shiguma' _h correction hot spot stress, the right side of _{σ h, m, σ h,} b is the film stress of each hot spot stress is the bending stress component, sigma _{h, obv,} from sigma _{h, rev} Calculated. σ _{h, obv} , σ _{h, and rev} represent the hot spot stress on the front surface and the back surface, respectively, when the surface for which stress is to be evaluated is the front surface.

4. Finite element analysis conditions The model was constructed with shell elements, and had a finer mesh size in the vicinity of the target weld for calculating the hot spot stress than in the surroundings (see FIG. 5). The element sizes on the vertical rib side and the horizontal rib side near the target weld were 1.8 mm and 2.0 mm, respectively. The element shape near the target weld was controlled to be as close to a square as possible. In order to reproduce the stiffness of the weld near the target weld, reports from Machida et al. (Susumu Machida, Masaaki Matoba, Hitoshi Yoshinari, Ryuichi Nishimura: Fatigue strength evaluation based on hot spot stress criteria (3rd report)-FEM Evaluation-The thickness was changed in accordance with the Shipbuilding Society of Japan, No. 171, pp. 477-484, 199) (see FIG. 6).
The boundary condition in the analysis was the support of the lower flange of the main girder so that it could be simply supported in the bridge axis and the direction perpendicular to the bridge axis. For analysis, general-purpose finite element analysis software, Abaqus 6.13 was used.

5. Results Change in intersection stress due to the use of anisotropic steel sheet Table 2 shows a list of analysis results. The results in Table 2 show the results of the weld toe having the largest corrected hot spot stress range in each model shown in Table 1. All models except the model-67 were HS-21. In the model-67, the result was HS-32. However, for comparison with effects of other models, the analysis result focusing on the HS-21 is also indicated by a model name of 67 '. POSmax and POSmin in Table 2 indicate the load position in the case where the corrected hot spot stress at the target portion is maximum and minimum, respectively.

括弧内は表面応力に占める面内膜応力成分を示す。

The values in parentheses indicate the in-plane film stress component occupying the surface stress.

Based on the results in Table 2, FIG. 7 shows the relationship between the Young's modulus in the direction perpendicular to the bridge axis in the case of horizontal ribs and the bridge axis direction in the case of vertical ribs and deck plates, and the corrected hot spot stress range of HS-21, and The fatigue limit of the fatigue design curve E grade according to JSSC is also shown. It has been known from previous studies that the fatigue design using the corrected hot spot stress should be E class.
As shown in FIG. 7, only the longitudinal ribs (see FIG. 7 (a)), the horizontal rib webs only (see FIG. 7 (b)), and the young of both the vertical ribs and the horizontal rib web (see FIG. 7 (c)) If the rate _{E 1} was increased by 15%, the stress range of HS-21 was reduced, respectively 4.6,4.1,8.4%. Here, the stress reduction rate is the result when the horizontal rib web height is 500 mm.
Deck plate, when reduced _{E 1} 15%, that is, HS-21 is reduced when the Young's modulus _{E 2} of the bridge width direction is increased by 15%, reduced the amount of the 0.3% thereof, It was about 1/10 compared to the effect of the change in the Young's modulus of the vertical ribs and the horizontal rib webs.
Young's modulus _{E 1} of the lateral rib web is changed, as a result of reduced stress range of HS-21, in the case of transverse rib web height 500 mm, resulted in meeting the fatigue limit 62N / mm ² in E grade. The horizontal rib web height in the case of 600 mm, irrespective of the change of the vertical ribs and the horizontal rib web Young's modulus _{E 1} of met the fatigue limit 62N / mm ² in E grade.
As described above, even if the height of the horizontal rib web is not set to 600 mm, the height of the horizontal rib web can be set to 500 mm by appropriately changing the Young's modulus of the vertical rib or the horizontal rib in a predetermined direction using an anisotropic steel plate. However, it can be seen that the fatigue limit of class E is 62 N / mm ² or less. Therefore, according to the present invention, it has been clarified that the stress generated at the intersection of the vertical rib and the horizontal rib can be reduced to reduce the height of the horizontal rib web.

FIG. 8 shows the relationship between the horizontal rib web height and the reduction rate of the corrected hot spot stress range in HS-21. As shown in FIG. 8 (b), the reduction amounts are the Young's modulus E ₁ of the horizontal rib web (Young's modulus in the first direction), the Young's modulus E ₁ of the vertical ribs (Young's modulus in the first direction), and the Young of the deck plate. The results are obtained when the modulus E ₂ (Young's modulus in the second direction) and the Young's modulus E ₁ (Young's modulus in the first direction) of both the horizontal rib web and the longitudinal rib are increased by 15%. As shown in FIG. 8A, in all cases, the lower the height of the horizontal rib web, the greater the amount of reduction in the stress range. This factor may be due to the fact that the lower the height of the transverse rib web, the larger the original stress range, so that there is an allowance for reduction, and the above-mentioned stress reduction mechanism caused by the deformation of the transverse rib web in the vertical direction. Therefore, when the height of the horizontal rib web is further reduced, that is, when the generated stress becomes high, it can be said that the application of an anisotropic steel sheet to the horizontal rib web has a large effect of improving fatigue durability.

In the case of changing the Young's modulus E ₁ of the members in FIG. 9 shows the change of each component of the correction hot spot stress generated in HS-21. In FIG. 9, only the model-41 is described as “compression / membrane”, “compression / bent”, “tensile / membrane”, and “tensile / bent” in the four bar graphs, respectively.・ Film ”,“ Compression / Bending ”,“ Tension / Membrane ”, and“ Tension / Bending ”. For other models, there is no such description, but for other models as well, the four bar graphs indicate “compression / film”, “compression / bending”, “tensile / membrane”, and “tensile / bending”. I have. Further, “compression / film” means compression / film stress, “compression / bending” means compression / bending stress, “tensile / film” means tension / film stress, and “tensile / bending” means tension / bending stress.
When the Young's modulus E ₁ of the lateral rib web increased (i.e. reduce the Young's modulus E ₂₎ is the range of decrease of the compression and bending stress component is the largest, followed by the compression-film stress was reduced. In the former, the lower the horizontal rib web height was, the larger the reduction width was, and in the latter, the higher the horizontal rib web height, the larger the reduction width was. Although tendency case of increasing the longitudinal ribs Young's modulus E ₁ of were similar, the range of decrease of the stress was smaller than in the case of increasing the Young's modulus E ₁ of the lateral rib web. If the Young's modulus E ₁ of the deck plate to reduce by 15% (when E ₂ was increased by 15%) is the tensile although stress component was reduced, the stress reduction effect, the vertical ribs and the horizontal rib web of It was smaller than those obtained when the Young's modulus was changed. These results support the above-described mechanism of reducing the out-of-plane bending stress generated in the horizontal rib web by applying the anisotropic steel sheet to the horizontal rib web or the vertical rib. The application of anisotropic steel sheet to the horizontal rib web has a greater effect of reducing the stress of the horizontal rib web than the application of the anisotropic steel sheet to the vertical rib, and the application of the anisotropic steel sheet to the deck plate hardly contributes to the reduction of the stress of the horizontal rib web. It is shown that.

6. Changes in Deformation Behavior of Steel Slab due to Application of Anisotropic Steel Plate FIG. 10 shows a comparison of deformation diagrams of a steel slab before and after a change in Young's modulus of each member in a model with a horizontal rib web height of 500 mm. The load position was a case where the corrected hot spot stress of HS-21 was minimized (maximum compression). In FIG. 10, a broken line shows a deformation diagram when the ordinary steel is applied, and a solid line shows a deformation diagram when the anisotropic steel plate is applied.
FIG. 10 (a), the (d), the in the case of increasing the E ₁ lateral rib web 15 percent, almost no change in the deformation diagram was observed. Further, as shown in FIG. 10 (b), (e) , (g), the vertical ribs cases _{E 1} a is increased 15%, of the longitudinal ribs deflection is reduced by 6.4%, FIG. 10 (c ), (f), as shown in (h), the rotational deformation of the longitudinal ribs adjacent the load position directly below the longitudinal ribs is reduced by 5.3% in the case where the E ₂ of the deck plate is increased by 15%. Here, the deflection of the vertical rib was calculated as the amount of vertical displacement from a base line obtained by connecting the displacement of the vertical rib at the position supported by the horizontal rib with a straight line. These results are considered to support the mechanism of reducing the out-of-plane bending stress generated in the horizontal rib web by applying the anisotropic steel sheet to the horizontal rib web or the vertical rib.

DESCRIPTION OF SYMBOLS 10 Steel deck 11 Deck plate 12 Vertical rib 13 Horizontal rib 13a Web 13b Lower flange 15 Welded part

Claims (6)

A steel slab supporting a deck plate by a vertical rib extending in a bridge axis direction and a horizontal rib extending in a direction orthogonal to the bridge axis and intersecting with the vertical rib,
The transverse ribs have different Young's moduli in a first direction on a plate surface and a second direction orthogonal to the first direction, and have a different Young's modulus in the first direction than the Young's modulus in the second direction. Formed by anisotropic steel sheet,
The steel slab is characterized in that the horizontal ribs are oriented vertically in the second direction.   The steel deck according to claim 1, wherein the transverse ribs have a Young's modulus in a second direction lower than that of ordinary steel. A steel slab supporting a deck plate by a vertical rib extending in a bridge axis direction and a horizontal rib extending in a direction orthogonal to the bridge axis and intersecting with the vertical rib,
The vertical ribs have different Young's moduli in a first direction on a plate surface and a second direction orthogonal to the first direction, and have a different Young's modulus in the first direction than the Young's modulus in the second direction. Formed by anisotropic steel sheet,
The steel ribbed slab is characterized in that the first direction of the longitudinal rib is directed to a bridge axis direction.   The steel slab according to claim 3, wherein a Young's modulus of the longitudinal rib in the first direction is higher than a Young's modulus of ordinary steel. The vertical ribs are formed in a flat plate shape having a plate surface along the vertical direction, the horizontal ribs have a web surface along the vertical direction, and are provided with notches into which the vertical ribs are inserted. And a lower flange attached to the lower end of the web,
The intersection of the vertical rib and the horizontal rib is continuously welded all around so as to close a gap between the edge of the notch and the vertical rib in the horizontal rib. Item 5. The steel slab according to any one of Items 1 to 4.   The horizontal ribs and the vertical ribs are formed by the anisotropic steel plate, and the horizontal ribs are oriented in the second direction in the vertical direction, and the vertical ribs are oriented in the first direction in the bridge axis direction. The steel deck according to any one of claims 1 to 5, wherein:

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