Steel floor slab with closed-section rib and fabrication method of steel floor slab with closed-section rib

Abstract

To restrain occurrence of deck-penetrating cracks originated at a weld root part.SOLUTION: A steel floor slab 1 with a closed-section rib in this invention comprises a closed sectional space A surrounded with a deck plate 11 and a closed-section rib 12, and a weld part 41 where the edge face of the closed-section rib 12 and the reverse face of the deck plate 11 are welded. There is a treatment region 11a arranged on the front face of the deck plate 11 where peening treatment is applied to reduce the residual welding stress. The peening treatment is a treatment that strikes the treatment region 11a at least twice. The strike center position along the bridge-axis-orthogonal direction, the direction which perpendicularly crosses the bridge axis direction of the deck plate 11, is located in the closed-section space side of a straight line L drawn on the weld route part P. The distance d along the bridge-axis-orthogonal direction from the weld route part P to the strike center position C is double the thickness TH of the deck plate 11 or less while the strike zone width w being one eighth the thickness TH of the deck plate 11 or more.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a closed section rib steel deck in which a closed section rib is welded to the back surface of a deck plate, and a manufacturing method for a closed section rib steel deck. [Background technology]

[0002] Conventionally, steel decks have been used as decks for bridges. Steel decks are composed of flat deck plates made of steel plates, and stiffening members such as closed section ribs (also called vertical ribs) and horizontal ribs with cross-sectional shapes such as approximately U-shaped, V-shaped, circular arc-shaped, and elliptical arc-shaped. Closed section rib steel decks, in which closed section ribs and horizontal ribs are welded to the underside of the deck plate, are generally used. Such steel decks are lighter than RC decks and composite decks, and have the advantage that they can be manufactured to a certain size in a factory and then transported to the site for installation.

[0003] In such closed section rib steel decks, cracks that penetrate the deck plate (deck penetration cracks) have been found. It has become clear that deck penetration cracks occur when fatigue cracks progress from an intersection (hereinafter sometimes referred to as the weld root) located near the closed section space formed by the deck plate and closed section rib, out of two intersections between the welded part of the deck plate and the closed section rib and the underside of the deck plate. Deck penetration cracks are dangerous as they can cause the deck plate to collapse, immediately affecting traffic seriously. Therefore, there is a need to establish countermeasure technology for deck penetration cracks.

[0004] For example, the steel deck disclosed in Patent Document 1 has a plate-shaped inner reinforcement material that connects the deck plate and the closed section rib inside the closed area formed by the deck plate and the closed section rib, and suppresses fatigue cracks such as deck-penetrating cracks that propagate from the welds between the deck plate and the closed section rib.

[0005] Furthermore, the steel deck disclosed in Patent Document 2 has a groove formed on the back surface of the deck plate extending along the bridge axis direction at a position separated by a predetermined distance on the closed space side from a weld root portion formed on the closed space side at the boundary between the back surface of the deck plate and the weld metal. The steel deck disclosed in Patent Document 2 has a groove formed on the back surface of the deck plate extending along the bridge axis direction at a position separated by a predetermined distance on the closed space side from the weld root portion, thereby avoiding stress concentration near the weld root portion and preventing the occurrence of fatigue cracks such as deck-penetrating cracks that start from the weld root portion.

[0006] Furthermore, Patent Document 3 discloses a steel deck in which a treatment such as hammer peening has been applied to the back surface corresponding to a target location. In the steel deck disclosed in Patent Document 3, a treatment such as hammer peening is applied to introduce compressive residual stress into the welded portion between the deck plate and the closed cross section rib, thereby improving the fatigue performance. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2017-133320 A [Patent Document 2] JP 2016-205024 A [Patent Document 3] JP 2014-172043 A Summary of the Invention [Problem to be solved by the invention]

[0008] The steel deck disclosed in Patent Document 1 is configured to newly attach plate-shaped inner reinforcement members to multiple positions in the closed area formed by the deck plate and the closed cross-section rib. As a result, the overall weight of the steel deck increases, and the lightweight nature of the steel deck, which is an advantage of the steel deck, is lost. In addition, when attaching inner reinforcement members to an existing steel deck, a hole is required in the closed cross-section rib to pass the inner reinforcement members through inside the closed area formed by the deck plate and the closed cross-section rib, so that the work of attaching inner reinforcement members to an existing steel deck is difficult.

[0009] In addition, the steel deck disclosed in Patent Document 2 requires an additional process of forming a groove on the back surface of the deck plate. As a result, the manufacturing efficiency of the steel deck decreases. In addition, by forming a groove on the back surface of the deck plate, it is possible to avoid stress concentration near the weld root, but there is a concern that the area where the groove is formed will become a new stress concentration point, and fatigue cracks will occur around the groove.

[0010] In addition, in the steel deck disclosed in Patent Document 3, for example, the rate of fatigue crack growth is suppressed by compressive residual stress induced in the welded portion between the deck plate and the closed cross-section rib. However, although the rate of fatigue crack growth can be suppressed, there is a possibility that the occurrence of fatigue cracks themselves cannot be suppressed.

[0011] As such, there is no established technology to suppress fatigue cracks that can lead to deck-penetrating cracks in closed section rib steel decks, so there is a growing demand for countermeasures to suppress fatigue cracks.

[0012] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a closed section rib steel deck, which is formed by welding a closed section rib to the underside of a deck plate, and which is capable of suppressing the occurrence of deck-penetrating cracks originating from the weld root. [Means for solving the problem]

[0013] A closed section ribbed steel deck according to one aspect is a closed section ribbed steel deck having a plate-shaped deck plate and a closed section rib welded to the back side of the deck plate, the closed section ribbed steel deck having a closed section space surrounded by the deck plate and the closed section rib, and a welded portion where an end face of the closed section rib and the back side of the deck plate are welded with a weld metal, the surface of the deck plate is provided with a treatment area where a peening treatment is performed to relieve welding residual stress remaining in the deck plate, and the peening treatment is performed so that the center position of the impact in the peening treatment is the same position or the amount of impact deviation is within a predetermined range. This is a process in which the treatment area is struck at least twice, as described above, and the center position of the impact in the peening process is located on the same side of the closed cross-sectional space as a straight line that passes through the intersection between the welded part and the back surface of the deck plate and is perpendicular to both the bridge axis direction and the bridge axis orthogonal direction of the deck plate, in the bridge axis orthogonal direction that is perpendicular to the bridge axis direction of the deck plate, and the distance from the intersection to the center position of the impact in the peening process is not more than twice the thickness of the deck plate in the bridge axis orthogonal direction, and the width of the impact in the peening process is not less than 1 / 8 of the thickness of the deck plate in the bridge axis orthogonal direction.

[0014] In addition, it is preferable that the peening treatment is performed at multiple positions on the deck plate in the direction perpendicular to the bridge axis, and the total width of the peening treatment performed at the multiple positions is 1 / 8 or more of the plate thickness t of the deck plate.

[0015] In addition, it is preferable that the material of either the deck plate or the closed cross-section rib is fatigue resistant steel.

[0016] A manufacturing method for a closed section rib steel deck according to another aspect is a manufacturing method for a closed section rib steel deck having a plate-shaped deck plate and a closed section rib welded to the back side of the deck plate, the manufacturing method comprising the steps of: welding an end face of the closed section rib to the back side of the deck plate with a weld metal in a state in which a closed section space is formed by the deck plate and the closed section rib; and performing a peening treatment on a treatment area provided on the surface of the deck plate to which the closed section rib is welded. The peening treatment is performed by repeating a peening treatment at least twice on the treatment area so that the center positions of the impacts in the peening treatment are the same position or the amount of impact deviation is within a predetermined range. The center position of the impact in the peening process passes through the intersection of the welded part between the end face of the closed cross section rib and the underside of the deck plate and the underside of the deck plate in the bridge axis orthogonal direction perpendicular to the bridge axis direction of the deck plate, and is located on the same side of the line as the closed cross section space when the line is perpendicular to both the bridge axis direction and the bridge axis orthogonal direction, and the distance from the intersection to the center position of the impact in the peening process is less than twice the thickness of the deck plate in the bridge axis orthogonal direction, and the width of the impact in the peening process is more than 1 / 8 of the thickness of the deck plate in the bridge axis orthogonal direction. Effect of the Invention

[0017] According to the present disclosure, in a closed section rib steel deck formed by welding a closed section rib to the underside of a deck plate, the occurrence of deck-penetrating cracks originating from the weld root portion between the deck plate and the rib can be effectively suppressed. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic cutaway perspective view showing an example of the configuration of a closed section rib steel deck in which the present invention is implemented. [Diagram 2] FIG. 2 is a schematic front view showing the manufacturing process of a closed section rib steel deck. [Diagram 3] FIG. 4 is a partially enlarged cross-sectional view showing the vicinity of the welded portion between the deck plate and the closed cross-section rib. [Figure 4]FIG. 2 is a schematic front view showing an area where peening treatment is applied to a closed section rib steel deck. [Diagram 5] FIG. 4 is a partially enlarged cross-sectional view showing the relationship between an impact tool and a deck plate in a peening process. [Figure 6] FIG. 1 shows fatigue cracks that occur in a deck board in a conventional closed section rib steel deck, where (a) is a schematic front view and (b) is a partially enlarged view of the vicinity of a welded portion. [Figure 7] FIG. 4 is a partially enlarged cross-sectional view showing a weld bead crack. [Figure 8] FIG. 11 is a partially enlarged cross-sectional view showing a case where peening is performed at a plurality of positions. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] An example of the configuration of a closed section rib steel deck embodying the present invention will be described with reference to the drawings. As shown in Fig. 1, the steel deck bridge 1 is composed of a closed section rib steel deck 10 and a main girder 20. Hereinafter, the closed section rib steel deck 10 may be simply referred to as a steel deck 10. The steel deck 10 is composed of a deck plate 11, closed section ribs (vertical ribs) 12 that stiffen the deck plate 11, and horizontal ribs 13. When the steel deck bridge 1 is used as a road bridge, a pavement 15 such as asphalt is laid on the surface of the deck plate 11. Although not shown, a ground guard is provided at both ends of the deck plate 11 in the direction perpendicular to the bridge width.

[0020] The deck plate 11 is a member that directly supports the wheel load via the pavement 15. As a floor slab, the deck plate 11 bears the bending moment and shear force between the main girders 20, and also functions as the upper flange of the main girders 20. For example, a steel material with a low fatigue crack propagation rate, that is, fatigue-resistant steel, is used as the material for the deck plate 11. In consideration of improving fatigue durability, the plate thickness of the deck plate 11 is preferably about 16 to 22 mm, for example. The deck plate 11 is placed in a plane on the main girders 20, and the joints of adjacent deck plates 11 are joined by welding or high-strength bolts.

[0021] A plurality of closed cross-section ribs 12 are arranged on the underside of the deck plate 11 along the direction perpendicular to the bridge width. The multiple closed cross-section ribs 12 are members that stiffen the deck plate 11. The multiple closed cross-section ribs 12 are fixed to the underside of the deck plate 11 by welding. The closed cross-section ribs 12 are arranged such that their longitudinal direction runs along the bridge axis direction.

[0022] The closed cross-section rib 12 may be a closed cross-section rib such as a Y-shaped cross-section rib, a V-shaped cross-section rib, a round cross-section rib, or a trough rib (hereinafter, sometimes referred to as a U-rib). For example, a U-rib is generally used as a closed cross-section rib used in road bridges. The following describes a case where a U-rib is used as the closed cross-section rib 12. The material of the closed cross-section rib 12 may be, for example, a fatigue-resistant steel, similar to the deck plate 11.

[0023] Taking into consideration corrosion, the plate thickness of the closed cross section rib 12 is preferably set to, for example, 6 to 8 mm as a minimum thickness. Also, the arrangement interval (interval in the direction perpendicular to the bridge axis) of the closed cross section ribs 12 is preferably set to, for example, about 30 cm. Furthermore, the height of the closed cross section rib 12 is preferably set to, for example, 240 mm.

[0024] The transverse ribs 13, like the closed cross-section ribs 12, are components that stiffen the deck plate 11 and also function as fulcrums for the closed cross-section ribs 12. The transverse ribs 13 are generally open cross-section ribs with an I-shaped cross section composed of a web and a lower flange. The transverse ribs 13 are arranged so that their longitudinal direction coincides with the direction perpendicular to the bridge axis. The transverse ribs 13 are also arranged at predetermined intervals in the bridge axis direction. Each of the transverse ribs 13 is fixed to the rear surface of the deck plate 11 by welding or the like.

[0025] Here, the arrangement interval of the transverse ribs 13 depends on the rigidity of the closed cross-section rib 12, but in fatigue design, a standard interval of 2.5 m or less is generally set. Although not shown in the figure, at the rib intersection where the closed cross-section rib 12 and the transverse rib 13 intersect, the web of the transverse rib 13 is cut out, so that the closed cross-section rib 12 penetrates the web of the transverse rib 13.

[0026] The main girder 20 is a member that is spanned between the abutments and piers and bears the bending moment and shear force between the spans. The main girder 20 is generally a member with an I-shaped cross section consisting of a web and upper and lower flanges. The deck plate 11 may also serve as the upper flange of the main girder 20. Furthermore, the main girder 20 may be an open cross-section main girder in which I-shaped cross-section members are arranged at predetermined intervals, or a closed cross-section main girder in the shape of a box girder. Although not shown in the figure, vertical stiffeners that stiffen the web of the main girder 20 are welded to the main girder 20 as necessary.

[0027] As shown in FIG. 3 and FIG. 4, a treatment area 11a is provided on the surface of the above-mentioned deck plate 11. The treatment area 11a is an area where a peening process is performed after the closed cross-section rib 12 is welded and fixed to the back side of the deck plate 11. The peening process may be, for example, a hammer peening process in which the base material (in this case, the deck plate 11) is struck at least twice by the striking tool 45. By performing the hammer peening process, the deck plate 11 is plastically deformed, the shrinkage distortion caused by welding the deck plate 11 and the closed cross-section rib 12 is reduced, and further, the stress remaining at the time of welding is alleviated. Here, the shape of the striking surface of the striking tool 45 is, for example, a 4 mm×5 mm rounded rectangle with chamfered corners. Note that the shape of the striking surface of the striking tool 45 does not need to be limited to a rounded rectangle, and may be any appropriate shape, such as a square, a circle, or an ellipse.

[0028] For example, the Highway Bridge Specifications state that the welding between the deck plate 11 and the closed section rib 12 must ensure a penetration of a thickness T (75% or more of the thickness of the closed section rib 12) with respect to the thickness t of the closed section rib 12. When the deck plate 11 and the closed section rib 12 are welded, a welded portion 41 is present between the deck plate 11 and the closed section rib 12, where the deck plate 11 and the closed section rib 12 are welded by the weld metal. In addition, an unwelded portion 42 of, for example, several mm to several tens of mm is present between the welded portion 41 and the closed section space A. Note that the position P is an intersection point between the welded portion 41 and the back surface of the deck plate 11, and this intersection point P is referred to as a weld root portion. Hereinafter, the intersection point P may be referred to as a weld root portion P.

[0029] The above-mentioned treatment area 11a is set as an area on the surface of the deck plate 11, for example, in the area inside the vertical line L passing through the weld root P in the direction perpendicular to the bridge axis of the deck plate 11 (i.e., an area located above the closed cross-section space A) and within a distance W from the weld root P. As described above, the closed cross-section rib 12 is formed by bending the width end portions 31b, 31c of the steel plate 31, so the closed cross-section rib 12 is welded to the deck plate 11 at two locations on the width end portions 31b, 31c of the steel plate 31. Therefore, the above-mentioned treatment area 11a is provided corresponding to each of the welding locations (symbols X1 and X2 in FIG. 4) of both ends of the closed cross-section rib 12 (width end portions 31b, 31c of the steel plate 31).

[0030] Next, a manufacturing method of the closed section rib steel deck 10 will be described. As shown in FIG. 2(a), the above-mentioned closed section rib 12 is formed, for example, by bending the width end portions 31b, 31c of the width center portion 31a of the steel plate 31 to just before a right angle by plate bending processing. Here, the end faces of the width end portions 31b, 31c of the steel plate 31 have a rectangular cross section. Therefore, as shown in FIG. 2(b), when the closed section space A is formed by the deck plate 11 and the closed section rib 12, a natural groove 35 that opens to the outside of the closed section space A is formed between the back surface of the deck plate 11 and both end portions (width end portions 31b, 31c) of the closed section rib 12. Using this natural groove 35, the deck plate 11 and the closed section rib 12 are welded from the outside of the closed section space A using a welding machine 36. After the deck plate 11 and the closed section rib 12 are welded using the welding machine 36, a peening process is performed on the treatment area 11a provided on the surface of the deck plate 11.

[0031] As shown in FIGS. 3 to 5, the peening process is carried out so as to satisfy the following conditions A to C.

[0032] Condition A: In a direction perpendicular to the bridge axis, the distance d from a straight line L passing through the weld root P to a straight line Lc passing through the center C of the impact tool 45 is, for example, less than twice the plate thickness TH of the deck plate 11 (more preferably, less than 1.5 times the plate thickness TH). Condition B: The width w of the impact by the impact tool 45 in the direction perpendicular to the bridge axis (synonymous with the width of the impact tool 45) is 1 / 8 or more (more preferably 1 / 4 or more) of the plate thickness TH of the deck plate 11. Condition C: Strikes are performed at least two times (more preferably four times or more) so that the center position of the strike in the peening process is the same position or the amount of deviation of the strike in the peening process is within a predetermined range.

[0033] Hereinafter, the mechanism of deck-penetrating cracks occurring in the conventional closed section rib steel deck 100 will be described. As shown in FIG. 6(a) and FIG. 6(b), when a vehicle passes over the closed section rib steel deck 100, the wheel load F of the vehicle generates compressive stress of about the yield stress in the weld root P' of the unwelded portion 115 in the direction of the joint surface between the closed section rib 112 and the deck plate 111. In addition, due to the tensile residual stress of about the yield stress generated by the thermal contraction effect around the unwelded portion 115 of the deck plate 111 and the stress concentration at the tip of the unwelded portion 115 due to the wheel load F, a tensile stress of about the yield stress is repeatedly applied in the direction perpendicular to the joint surface between the closed section rib 112 and the deck plate 111. As a result, a fatigue crack 120 is generated starting from the weld root P'. This fatigue crack 120 progresses toward the surface direction of the deck plate 111 through the welded portion 114, and is finally discovered as a deck-penetrating crack.

[0034] In order to suppress the occurrence of such fatigue cracks 120 originating from the weld root P', it is necessary to reduce the stress σ acting on the weld root P'. The stress σ acting on the weld root P' is determined by the nominal stress σn due to the vehicle weight, the stress concentration factor Kt due to the shape of the unwelded portion 115, and the tensile residual stress σr due to welding. Therefore, by reducing the stress concentration factor Kt and the tensile residual stress σr, the stress σ acting on the weld root P' is reduced. In addition, as a method for reducing the tensile residual stress σr, a method of imparting compressive residual stress not only to the weld root P' but also to the welded portion 41, for example, can be mentioned. Therefore, in this embodiment, a peening process is performed on the treatment area 11a provided on the surface of the deck plate 11 to impart compressive residual stress to the weld root P' and the welded portion 41, thereby reducing the stress σ acting on the weld root P' and suppressing the occurrence of fatigue cracks in the deck plate 111.

[0035] As described above, for example, when the closed cross-section rib 12 is welded to the deck plate 11, an unwelded portion 42 is formed at the welded portion between the deck plate 11 and the closed cross-section rib 12 in addition to the welded portion 41. The peening process in this embodiment is performed by setting the distance d from the weld root P to the center Lc of the impact by the impact tool 45 to no more than twice the thickness TH of the deck plate 11 (more preferably no more than 1.5 times).

[0036] (Regarding condition A) The peening process is performed so as to satisfy the condition A. As described above, in this embodiment, the peening process uses the impact tool 45 to impact the surface of the deck plate 11. At this time, it is preferable that the right end of the impact tool 45 is located closer to the closed cross-section space A than the vertical line L described above. For example, when the above-mentioned distance d is set to be equal to or less than twice the plate thickness TH of the deck plate 11 in the direction perpendicular to the bridge axis, the unwelded portion 42 formed between the tip surface of the closed cross-section rib 12 (the tip surface of the width end portion 31b of the steel plate 31) and the back surface of the deck plate 11 becomes smaller due to the plastic deformation of the deck plate 11. In other words, the stress σ concentrated in the weld root portion P is dispersed by the back surface of the deck plate 11, which is plastically deformed, being in close contact with the tip surface of the closed cross-section rib 12. In addition, the tensile residual stress σr remaining in the weld portion 41 becomes smaller. As a result, the stress σ acting on the weld root portion P becomes smaller, and the occurrence of fatigue cracks from the weld root portion P toward the surface of the deck plate 11 is suppressed.

[0037] When peening is performed by setting the distance d to a value exceeding twice the plate thickness TH of the deck plate 11, the deck plate 11 undergoes plastic deformation, but this plastic deformation does not reduce the size of the unwelded portion 42. Therefore, just as with a steel deck that has not been subjected to peening, stress σ remains concentrated at the weld root portion P. The same is true when peening is performed at a position outside the vertical line L (a position on the opposite side of the closed cross section space with respect to the vertical line L). In other words, in these cases, fatigue cracks are more likely to occur, just like with conventional closed cross section rib steel decks.

[0038] (Regarding condition B) The peening process is performed so as to satisfy condition B. As described above, in this embodiment, the peening process is performed by striking the surface of the deck plate 11 using the striking tool 45. In this case, too, it is preferable that the right end of the striking tool 45 is located closer to the closed cross-sectional space A than the vertical line L described above. Therefore, condition B is a condition for the plastic deformation of the deck plate 11 to reach the back side of the deck plate 11 when the surface of the deck plate 11 is struck. For example, when the width w of the strike by the striking tool 45 in the direction perpendicular to the bridge axis is set to 1 / 8 or more (more preferably 1 / 4 or more) of the plate thickness TH of the deck plate 11, the plastic deformation of the deck plate 11 caused by the peening process affects the back side of the deck plate 11. Therefore, the unwelded portion 42 formed between the tip surface of the closed cross-sectional rib 12 (the tip surface of the width end portion 31b of the steel plate 31) and the back side of the deck plate 11 becomes smaller. In other words, the back side of the deck plate 11 that is plastically deformed and the tip surface of the closed cross-sectional rib 12 are in close contact with each other, and thus the stress σ concentrated on the weld root portion P is dispersed. Also, the tensile residual stress σr remaining in the welded portion 41 decreases. As a result, the stress σ acting on the weld root P decreases, suppressing the occurrence of fatigue cracks from the weld root P toward the surface of the deck plate 11, and instead, for example, fatigue cracks occur from the weld root P toward the outside of the welded portion 41.

[0039] It should be noted that, if the width w of the impact by the impact tool 45 is set to less than 1 / 8 of the plate thickness t of the deck plate 11, the plastic deformation of the deck plate 11 caused by the peening process does not affect the back surface side of the deck plate 11. In other words, the unwelded portion 42 remains unchanged, so stress remains concentrated at the weld root portion P.

[0040] (Regarding condition C) The peening process is carried out so as to satisfy condition C. Like condition B, condition C is a condition for causing the plastic deformation of the deck plate 11 caused by the peening process to reach the back side of the deck plate 11. By satisfying this condition C, it is possible to cause the plastic deformation of the deck plate 11 to affect the back side of the deck plate 11. Note that an example of the "predetermined range" in condition C is that the amount of deviation of the striking surface when the striking tool 45 strikes the deck plate 11 is within 25%.

[0041] By striking approximately the same position on the surface of the deck plate 11 at least twice with the striking tool 45, the amount of plastic deformation of the deck plate 11 increases and the unwelded portion 42 can be reduced. As a result, the stress σ concentrated at the weld root portion P is dispersed. Also, the tensile residual stress σr remaining in the welded portion 41 is reduced. As a result, the stress σ acting on the weld root portion P is reduced, suppressing the occurrence of fatigue cracks from the weld root portion P toward the surface of the deck plate 11, and instead, for example, fatigue cracks occur from the weld root portion P toward the outside of the welded portion 41.

[0042] It should be noted that the peening process, in which the impact tool 45 strikes a predetermined position on the front surface of the deck plate 11 once, causes a small amount of plastic deformation in the deck plate 11. Therefore, even when the peening process is performed, the plastic deformation of the deck plate 11 does not affect the back surface side of the deck plate 11. In other words, the unwelded portion 42 remains unchanged, and stress remains concentrated at the weld root portion P.

[0043] In this embodiment, the peening process is performed so as to satisfy all of the above-mentioned conditions A to C. This reduces stress concentration at the weld root P. The reduction in stress concentration at the weld root P slows down the progression of fatigue cracks (reference numeral 120 in FIG. 6(b)). As a result, the occurrence of deck-penetrating cracks due to the progression of the fatigue cracks 120 is suppressed. On the other hand, as shown in FIG. 7, there is a possibility that weld bead cracks 61 are more likely to occur in the welded portion 41. Note that the weld bead cracks 61 occur in the welded portion 41. That is, the weld bead cracks 61 are easily confirmed below the steel deck 10. Therefore, it is possible to inspect the occurrence of cracks from below the steel deck 10 and repair the cracks (repair the welded portion 41). This suppresses the occurrence of deck-penetrating cracks, which require the steel deck 10 to be replaced and are therefore extremely expensive to replace, and makes it easier to perform not only inspection but also maintenance work by making it easier to generate weld bead cracks 61 that are easy to inspect and repair.

[0044] In this embodiment, a case is described in which one impact tool 45 is used when performing the peening process in the processing area 11a provided on the surface of the deck plate 11. When one impact tool 45 is used, for example, it is possible to perform the peening process while shifting the impact tool 45 in the bridge axis direction at a first position in the direction perpendicular to the bridge axis, and then perform the peening process at a second position shifted a certain amount from the first position in the direction perpendicular to the bridge axis while shifting the impact tool 45 in the bridge axis direction. The shift amount from the first position to the second position may be such that the processing area by the impact tool 45 at the first position and the processing area by the impact tool at the second position overlap.

[0045] In addition, instead of shifting the impact tool 45 from the first position to the second position in the treatment area 11a of the deck plate 11, a hammer peening process may be performed in which two impact tools 45a, 45b are struck simultaneously, as shown in Figure 8.

[0046] In this embodiment, the tip faces of the width end portions 31b, 31c of the steel plate 31, which form the closed cross-section rib 12, have a rectangular cross section. However, for example, the tip faces of the width end portions 31b, 31c may be chamfered.

[0047] In this embodiment, the welding method between the deck plate 11 and the closed cross-section rib 12 is not particularly limited, but the occurrence of fatigue cracks can be suppressed by adopting a welding method with fewer bead defects, such as TIG (Tungsten Inert Gas) welding or MAG (Metal Active Gas) welding using flux cord wire.

[0048] In the present embodiment, a fatigue-resistant steel with a slow crack growth rate is used as the material for the deck plate 11 and the closed cross-section rib 12. An example of the fatigue-resistant steel is AFD (Anti-fatigue Damage) steel (registered trademark: manufactured by JFE Steel Corporation). By using such fatigue-resistant steel, it is possible to suppress the occurrence of deck-penetrating cracks.

[0049] The closed section ribbed steel deck shown in this embodiment is taken as an example of a closed section ribbed steel deck having an unwelded portion and a welded portion to which peening has been applied, but it may also be a closed section ribbed steel deck having no unwelded portions, i.e., only welded portions, to which peening has been applied. The closed section ribbed steel deck shown in this embodiment may be, for example, a closed section ribbed steel deck having a welded portion with a penetration amount of 75% or less during welding and an unwelded portion, or a closed section ribbed steel deck in which a closed section rib and a deck plate are welded so that a bead (reverse wave) is generated on the inside of the closed section rib (closed section space side) to which peening has been applied.

[0050] <Summary of the invention> According to the closed section ribbed steel deck of the present invention, there is provided a closed section ribbed steel deck 10 having a plate-shaped deck plate 11 and a closed section rib 12 welded and fixed to the back side of the deck plate 11, the closed section ribbed steel deck 10 having a closed section space A surrounded by the deck plate 11 and the closed section rib 12, and a welded portion 41 where an end face of the closed section rib 12 and the back side of the deck plate 11 are welded with a weld metal, and a treatment area 11a is provided on the surface of the deck plate 11 where a peening treatment is performed to relieve welding residual stress remaining in the deck plate 11, and the peening treatment is performed such that the center position of the impact in the peening treatment is the same position or the amount of impact deviation is within a predetermined range. This is a process in which the treatment area 11a is struck at least twice so as to strike the treatment area 11a at least twice so that the central position of the impact in the peening process is located on the same side as the closed cross-sectional space A with respect to a straight line L that passes through an intersection P between the welded portion 41 and the underside of the deck plate 11 and is perpendicular to both the bridge axis direction and the bridge axis orthogonal direction, in the bridge axis orthogonal direction of the deck plate 11, the distance d from the intersection P to the central position C of the impact in the peening process is not more than twice the thickness TH of the deck plate 11 in the bridge axis orthogonal direction, and the width w of the impact in the peening process is not less than 1 / 8 of the thickness TH of the deck plate 11 in the bridge axis orthogonal direction.

[0051] According to this, the unwelded portion 42 becomes smaller due to the deck plate being plastically deformed by the peening treatment, so it is possible to prevent stress concentration on the weld bead portion P and disperse the generated stress. By dispersing the generated stress, it is possible to suppress the occurrence of deck-penetrating cracks caused by stress concentration on the weld bead portion P.

[0052] In addition, it is preferable that the peening treatment is performed at multiple positions on the deck plate 11 in the direction perpendicular to the bridge axis, and the total width of the peening treatment performed at the multiple positions in the direction perpendicular to the bridge axis is 1 / 8 or more of the plate thickness t of the deck plate 11.

[0053] According to this, the plastic deformation of the deck plate 11 caused by the peening treatment affects the back side of the deck plate 11, reducing the size of the unwelded portion. By reducing the size of the unwelded portion, it is possible to suppress stress concentration at the weld root portion P. As a result, it is possible to suppress the occurrence of deck-penetrating cracks caused by stress concentration at the weld bead portion P.

[0054] Moreover, it is preferable that the material of either the deck plate 11 or the closed cross-section rib 12 is fatigue resistant steel.

[0055] According to this, by using fatigue-resistant steel for either the deck plate 11 or the closed cross-section rib 12, even if fatigue cracks occur due to wheel load, it is possible to delay the occurrence of cracks caused by the occurring fatigue cracks, such as deck-penetrating cracks and weld bead cracks. [Explanation of symbols]

[0056] 1 Steel slab bridge 10. Closed section rib steel deck 11 Deck plate 11a Processing area 12 Closed section rib 13 Horizontal ribs 15. Pavement 20 Main digit 31 Steel plate 31a Width center part 31b,31c Width end part 35 Natural groove 36 Welding Machine 41 Welded area 42 Unwelded area 45, 45a, 45b Impact tools 61 Weld bead crack 100 Conventional closed section rib steel deck 111 Deck plate 112 Closed Section Rib 114 Welded area 115 Unwelded area 120 Fatigue cracks A closed section space P Weld root

Claims

1. A closed section rib steel deck having a plate-shaped deck plate and a closed section rib welded to the back side of the deck plate, The closed section rib steel deck is A closed cross-sectional space surrounded by the deck plate and the closed cross-sectional rib; a welded portion in which an end face of the closed cross-section rib and a back surface of the deck plate are welded by a weld metal; having A treatment area is provided on a surface of the deck plate, where a peening treatment is performed to relieve welding residual stress remaining in the deck plate, the peening process is a process of striking the treatment region at least twice or more such that the center positions of the strikes in the peening process are the same position or the amount of deviation of the strikes is within a predetermined range, The center position of the impact in the peening process is located on the same side as the closed cross-sectional space with respect to a straight line that passes through an intersection between the welded portion and the back surface of the deck plate and is perpendicular to each of the bridge axis direction and the bridge axis orthogonal direction in a bridge axis orthogonal direction perpendicular to the bridge axis direction of the deck plate, The distance from the intersection to the center position of the impact in the peening process is equal to or less than twice the thickness of the deck plate in the direction perpendicular to the bridge axis, The width of the impact in the peening process is 1 / 8 or more of the thickness of the deck plate in the direction perpendicular to the bridge axis. A closed section rib steel deck characterized by the above.

2. The peening process is performed at a plurality of positions of the deck plate in a direction perpendicular to the bridge axis, The total width of the peening process performed at the multiple positions is equal to or greater than 1 / 8 of the plate thickness t of the deck plate.

2. The closed section rib steel deck according to claim 1 .

3. The material of either the deck plate or the closed cross-section rib is fatigue resistant steel. The closed section rib steel deck according to claim 1 or 2.

4. A manufacturing method for a closed section rib steel deck having a plate-shaped deck plate and a closed section rib welded to the back side of the deck plate, a step of welding an end surface of the closed cross-section rib and a back surface of the deck plate with a weld metal in a state in which a closed cross-section space is formed by the deck plate and the closed cross-section rib; a step of performing a peening treatment on a treatment area provided on a surface of the deck plate to which the closed cross-section rib is welded and fixed; having the peening process is a process of striking the treatment region at least twice or more such that the center positions of the strikes in the peening process are the same position or the amount of deviation of the strikes is within a predetermined range, The center position of the impact in the peening process passes through the intersection of the welded portion between the end face of the closed cross section rib and the back surface of the deck plate and the back surface of the deck plate in a bridge axis orthogonal direction perpendicular to the bridge axis direction of the deck plate, and is located on the same side as the closed cross section space with respect to a straight line perpendicular to each of the bridge axis direction and the bridge axis orthogonal direction, The distance from the intersection to the center position of the impact in the peening process is equal to or less than twice the thickness of the deck plate in the direction perpendicular to the bridge axis, The width of the impact in the peening process is 1 / 8 or more of the thickness of the deck plate in the direction perpendicular to the bridge axis. A manufacturing method for closed section rib steel deck plate characterized by the above.

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