Residual stress reduction method of steel plate deck

Abstract

To provide a residual stress reduction method of steel plate deck capable of reducing a construction time.SOLUTION: The present invention relates to a method of reducing a residual stress of steel plate deck that comprises a deck plate, horizontal plates extending to a first direction, vertical plates extending to a second direction crossing to the first direction, and welding parts having straight welding parts and boxing welding parts and welding the horizontal plates and the vertical plates. The method includes a first heating step of conducting high frequency induction heating to a first heating target area corresponding to toe parts of the boxing welding part of the welding part, a second heating step of conducting high frequency induction heating to a second heating target area along one straight welding part of the welding part after the first heating step, and a third heating step of conducting high frequency induction heating to a third heating target area along the other straight welding part of the welding part after the second heating step. These heating steps are conducted to one heating target surface of the horizontal plate such that a stress distribution is formed so as to act a compression stress on the first heating target area and make a tensile stress be strong while leaved to the direction along a toe part of an end part of the welding part from the first heating target area.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a method for reducing residual stress in a steel deck. [Background technology]

[0002] Known examples of steel decks used in bridges such as road bridges include a steel deck that includes a deck plate supported by main girders, horizontal plates (horizontal ribs, diaphragms, etc.) joined to the underside of the deck plate, and vertical plates (vertical ribs, etc.) welded to the underside of the deck plate so as to cross the horizontal plates (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6072946 Summary of the Invention [Problem to be solved by the invention]

[0004] In bridges constructed by welding, residual stress occurs in the welds. When the bridge is used, stress may concentrate in a part of the horizontal plate, which, combined with the residual stress, may cause damage such as fatigue cracks. To reduce the residual stress, conventionally, processes such as finishing the weld toes of the horizontal plate and peening have been performed. However, these processes require work to be carried out along the toes of the welds from both sides of the horizontal plate, which takes a lot of time.

[0005] The present invention has been made in view of the above, and aims to provide a method for reducing residual stress in a steel deck that can shorten construction time. [Means for solving the problem]

[0006] The present invention provides a method for reducing residual stress in a steel deck, the method comprising: a deck plate; a horizontal plate joined to the underside of the deck plate, extending in a first direction, and having a band-shaped cutout portion formed from an upper end downward so as to penetrate a first surface and a second surface on a front and back sides in a second direction perpendicular to the first direction; a vertical plate extending in the second direction and joined to the underside of the deck plate so as to penetrate the cutout portion of the horizontal plate in the second direction; and welds arranged on both the first and second surfaces of the horizontal plate so as to surround the vertical plate, joining the horizontal plate and the vertical plate, the welds having linear welds along each of the front and back surfaces in the first direction of the vertical plate and a boxing weld surrounding a lower end of the vertical plate, the method comprising the steps of: a first heating step of high-frequency induction heating a first heating target area corresponding to the end of the vertical plate; a second heating step of high-frequency induction heating a second heating target area along the linear weld that extends to one of the front and back surfaces of the vertical plate in the welded portion on the heating target surface of the horizontal plate after the first heating step; and a third heating step of high-frequency induction heating a third heating target area along the linear weld that extends to the other of the front and back surfaces of the vertical plate in the welded portion on the heating target surface of the horizontal plate after the second heating step, wherein the high-frequency induction heating is performed in the first heating step, the second heating step, and the third heating step to form a stress distribution in which compressive stress acts on the first heating target area and tensile stress increases with increasing distance from the first heating target area in a direction along the toe of the end of the weld. [Effects of the Invention]

[0007] According to the present invention, a method for reducing residual stress in a steel deck that can shorten construction time can be provided. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view schematically showing an example of a bridge according to this embodiment. [Figure 2]FIG. 2 is a cross-sectional view showing an example of a bridge. [Figure 3] FIG. 3 is a diagram showing an example of an intersection between a horizontal rib and a vertical rib of a steel deck. [Figure 4] FIG. 4 is a diagram showing an example of an intersection between a horizontal rib and a vertical rib of a steel deck. [Figure 5] FIG. 5 is a flowchart showing an example of a method for reducing residual stress in a steel deck according to this embodiment. [Figure 6] FIG. 6 is a diagram showing an example of an intersection between a horizontal rib and a vertical rib of a steel deck. [Figure 7] FIG. 7 is a diagram showing an example of temperature change in a target region when high-frequency induction heating is performed. [Figure 8] FIG. 8 is a diagram showing an example of a change in stress when high-frequency induction heating is performed on the welded structure according to this embodiment. [Figure 9] FIG. 9 is a diagram showing an example of stress distribution on the heating target surface of the horizontal rib. [Figure 10] FIG. 10 is a diagram showing an example of stress distribution on the non-heated surface of the transverse rib. [Figure 11] FIG. 11 is a diagram showing an example of stress distribution on the heating surface of the transverse rib. [Figure 12] FIG. 12 is a diagram showing an example of stress distribution on the non-heated surface of the transverse rib. [Figure 13] FIG. 13 is a diagram showing an example of a process for replacing a steel deck. [Figure 14] FIG. 14 is a diagram showing an example of a process for replacing a steel deck. [Figure 15] FIG. 15 is a diagram showing another example of an intersection between a horizontal rib and a vertical rib of a steel deck. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of a method for reducing residual stress in a steel deck according to the present invention will be described with reference to the drawings. Note that the present invention is not limited to this embodiment. Furthermore, the components in the following embodiments include those that are easily replaceable by a person skilled in the art, or those that are substantially identical.

[0010] FIG. 1 is a perspective view schematically showing an example of a bridge 100 according to this embodiment. FIG. 2 is a cross-sectional view showing an example of the bridge 100. The bridge 100 shown in FIGS. 1 and 2 is, for example, a road bridge on which automobiles and the like travel. As shown in FIGS. 1 and 2, the bridge 100 includes a steel deck 10 and a main girder 20.

[0011] 1 and 2, the width direction of the bridge 100 is defined as the first direction (width direction D1), the bridge axis direction of the bridge 100 is defined as the second direction (bridge axis direction D2), and the up-down direction of the bridge 100, i.e., the direction perpendicular to the width direction D1 and the bridge axis direction D2, is defined as the third direction (up-down direction D3). The width direction D1 and the bridge axis direction D2 are directions along the main surface 30a of the deck plate 30, which will be described later. The up-down direction D3 is a direction perpendicular or nearly perpendicular to the main surface 30a.

[0012] The steel deck 10 is arranged in multiple rows, for example, in the width direction D1 and the bridge axis direction D2. The main girders 20 support the steel deck 10. The main girders 20 are, for example, plate girders, but are not limited to this and may be box girders. The main girders 20 are supported by substructures (not shown). In this embodiment, the bridge 100 to which the steel deck 10 is applied is, for example, a new steel road bridge, but is not limited to this and may be a new steel railway bridge, etc.

[0013] The steel deck 10 comprises a deck plate 30, horizontal ribs (horizontal plates) 40, vertical ribs (vertical plates) 50, and welds 60. Figures 3 and 4 are diagrams showing an example of an intersection between the horizontal ribs 40 and the vertical ribs 50 of the steel deck 10. Figure 3 is a diagram showing the state as seen in the bridge axis direction D2, and Figure 4 is a diagram showing the state as seen in the width direction D1.

[0014] The deck plate 30 is formed of, for example, a steel plate, etc. The deck plate 30 is supported by the main girders 20 at a plurality of positions in the width direction D1.

[0015] The transverse ribs 40 are joined to the underside 30b of the deck plate 30. The transverse ribs 40 are arranged extending in the width direction D1. Multiple transverse ribs 40 are arranged in the bridge axis direction D2. The transverse ribs 40 have a web 41 and a flange 42. The web 41 is flat and arranged on the underside 30b of the deck plate 30. A cutout portion 43 is provided in the web 41. The cutout portion 43 is formed in a strip shape extending downward from the upper end 41c of the web 41. The cutout portion 43 is formed so as to penetrate the first surface 41a and the second surface 41b on the front and back of the web 41 in the bridge axis direction D2. The cutout portion 43 allows the longitudinal rib 50 to penetrate through it. The flange 42 is joined to the lower end of the web 41.

[0016] The vertical ribs 50 are flat and arranged extending in the bridge axis direction D2. The vertical ribs 50 intersect with the horizontal ribs 40 while passing through the cutout portions 43 of the horizontal ribs 40. The vertical ribs 50 are joined to the underside 30b of the deck plate 30 and the horizontal ribs 40. The vertical ribs 50 are welded to the horizontal ribs 40 around the entire periphery of the cutout portions 43. A plurality of vertical ribs 50 are provided in the width direction D1. The intervals between adjacent vertical ribs 50 in the width direction D1 are, for example, equal.

[0017] The welded portion 60 joins the transverse rib 40 and the longitudinal rib 50. The welded portion 60 is provided on both the first surface 41a and the second surface 41b of the transverse rib 40. The welded portion 60 is provided so as to surround the longitudinal rib 50 when viewed in the bridge axis direction D2. In this embodiment, the welded portion 60 is arranged so as to weld the entire circumference of the longitudinal rib 50 when viewed in the bridge axis direction D2.

[0018] The weld 60 has straight welds 61, 62 and a box weld 63. The straight weld 61 extends linearly in the up-down direction D3 along the front surface 50a of the vertical rib 50. The straight weld 62 extends linearly in the up-down direction D3 along the back surface 50b of the vertical rib 50. The box weld 63 is provided to surround the lower end 51 of the vertical rib 50. The box weld 63 connects the lower ends of the two straight welds 61, 62 together.

[0019] When a moving object such as an automobile travels on the above-described steel deck 10, the load of the moving object is transmitted from the steel deck 10 to the longitudinal rib 50. When the load is transmitted from the longitudinal rib 50, stress to support the load is generated, for example, at the toe W1 of the boxing weld 63 of the horizontal rib 40, and this stress may remain as residual stress even after the load is released. Below, a method for reducing such residual stress in the steel deck 10 will be described.

[0020] Fig. 5 is a flowchart showing an example of a method for reducing residual stress in a steel deck 10 according to this embodiment. As shown in Fig. 5, the method for reducing residual stress in a steel deck 10 according to this embodiment includes a first heating step S10, a second heating step S20, and a third heating step S30.

[0021] Fig. 6 is a diagram showing an example of an intersection between a horizontal rib 40 and a vertical rib 50 of the steel deck 10. Fig. 6 shows the state as seen in the bridge axis direction D2.

[0022] As shown in Fig. 6, in the first heating step S10, high-frequency induction heating is performed on a first heating target area AR1 corresponding to the toe W1 of the boxing weld 63 of the weld 60, on a heating target surface 41R, which is one of the first surface 41a and second surface 41b of the transverse rib 40. In this embodiment, the first surface 41a of the transverse rib 40 is described as the heating target surface 41R. In this case, the second surface 41b is a non-heating surface 41S that is not heated. Note that when the second surface 41b is the heating target surface, the first surface 41a is the non-heating surface 41S.

[0023] In the second heating step S20, after the first heating step S10, high-frequency induction heating is performed on the second heating target area AR2 on the heating target surface 41R (first surface 41a) of the horizontal rib 40, along the linear welding portion 61 of the welding portion 60 extending toward the surface 50a of the vertical rib 50.

[0024] In the third heating step S30, after the second heating step S20, high-frequency induction heating is performed on the third heating target area AR3 on the heating target surface 41R (first surface 41a) of the horizontal rib 40, along the linear welding portion 62 of the welding portion 60 extending toward the back surface 50b of the vertical rib 50.

[0025] 6, the distance d1 between the first heating target area AR1 and the toe W1 of the boxing weld 63 can be set, for example, in the range of 0 mm to 100 mm, more preferably 0 mm to 50 mm, and even more preferably 0 mm to 25 mm. The distance d2 between the second heating target area AR2 and the toe W2 of the linear weld 61, and the distance d3 between the third heating target area AR3 and the toe W3 of the linear weld 62 can be set, for example, in the range of 25 mm to 100 mm, more preferably 25 mm to 50 mm, and even more preferably 25 mm to 35 mm. Note that the distances d1, d2, and d3 are not limited to the above ranges.

[0026] When high-frequency induction heating is performed in the first heating step S10, the second heating step S20, and the third heating step S30, a coil CL of the high-frequency induction heating device is attached to each of the first heating target area AR1, the second heating target area AR2, and the third heating target area AR3. Regarding the coil CL, for example, a coil CL having a size corresponding to the size of each heating target area AR can be prepared as appropriate.

[0027] Furthermore, when high-frequency induction heating is performed in the first heating step S10, the second heating step S20, and the third heating step S30, a target heating temperature and a heating time required to reach that heating temperature are set.

[0028] The first heating temperature T1 in the first heating step S10 can be set to a temperature of 250°C or higher and 550°C or lower. The first heating temperature T1 can be set more preferably to a temperature of 250°C or higher and 450°C or lower, and even more preferably to a temperature of 250°C or higher and 350°C or lower. The first heating temperature T1 is lower than the second heating temperature T2 and the third heating temperature T3 described below. The lower limit of the range of the first heating temperature T1 may be, for example, 150°C or higher or 200°C or higher.

[0029] The first heating time t1 in the first heating step S10 can be, for example, 9 seconds or more and 40 seconds or less. The first heating time t1 can be set more preferably to 9 seconds or more and 30 seconds or less, and even more preferably to 9 seconds or more and 20 seconds or less. The first heating time t1 is shorter than the second heating time t2 and the third heating time t3 described below. The lower limit of the range of the first heating time t1 can be set to, for example, 6 seconds or more, when the lower limit of the range of the first heating temperature T1 is set to 150°C or more as described above.

[0030] The second heating temperature T2 in the second heating step S20 and the third heating temperature T3 in the third heating step S30 can be set to a temperature of 250° C. or higher and 550° C. or lower. The second heating temperature T2 and the third heating temperature T3 can be set more preferably to a temperature of 350° C. or higher and 550° C. or lower, and even more preferably to a temperature of 450° C. or higher and 550° C. or lower. The upper limit of the range of the second heating temperature T2 and the third heating temperature T3 may be set to, for example, 700° C. or lower.

[0031] The second heating time t2 in the second heating step S20 and the third heating time t3 in the third heating step S30 can be, for example, 9 seconds or more and 40 seconds or less. The second heating time t2 and the third heating time t3 can be set more preferably to 9 seconds or more and 30 seconds or less, and even more preferably to 9 seconds or more and 20 seconds or less. The upper limit of the range of the second heating time t2 and the third heating time t3 can be set to, for example, 50 seconds or less, when the upper limit of the range of the second heating temperature T2 and the third heating temperature T3 is set to 700°C or less as described above.

[0032] FIG. 7 is a diagram showing an example of the temperature change in the target area when high-frequency induction heating is performed. The horizontal axis of FIG. 7 represents the elapsed time from the start of heating. The vertical axis of FIG. 7 represents the temperature of each heating target area AR. As shown in FIG. 7, in each heating process (S10, S20, S30), heating is performed so that the initial temperature T0 reaches the target heating temperature T (T1, T2, T3) within a preset heating time t (t1, t2, t3). In each heating process, heating is stopped when the heating temperature T is reached. By stopping the heating, the steel deck 10 (transverse rib 40) is allowed to cool naturally.

[0033] Figure 8 shows an example of stress changes near the lower side of the toe W1 when high-frequency induction heating is performed on the welded structure according to this embodiment. Figure 8 shows the residual stress distribution F0 occurring in the steel deck 10 (transverse rib 40) before the first heating step S10; the stress distribution F1 resulting from the expansion of the first heating target area AR1 during the first heating step S10; the stress distribution F2 resulting from the expansion of the second heating target area AR2 during the second heating step; the stress distribution F3 resulting from the expansion of the third heating target area AR3 during the third heating step; and the stress distribution F4, which is the sum of the residual stress distribution F0 and the stress distributions F1, F2, and F3. In the graphs showing each load, the horizontal axis corresponds to the lateral position of the steel deck 10 (transverse rib 40) in the figure. The upper side of the horizontal axis (the side indicated by arrow a1) represents the strength of the tensile stress, and the lower side of the horizontal axis (the side indicated by arrow a2) represents the strength of the compressive stress.

[0034] As described above, the steel deck 10 used in the bridge 100 has welding-induced residual tensile stress in the area listed above as the first heating target area AR1 due to use of the bridge 100, and fatigue cracks may occur due to repeated loads acting on this area. In the example shown in Figure 8, before the first heating step S10 is performed, the steel deck 10 has residual tensile stress at the joint between the horizontal rib 40 and the vertical rib 50.

[0035] From this state, by performing the first heating step S10, compressive stress acts on the first heating target area AR1 of the transverse rib 40 of the steel deck 10, and a stress distribution can be formed in which stronger tensile stress acts the further away from the first heating target area AR1 it is toward the second heating target area AR2 and the third heating target area AR3.

[0036] Furthermore, by performing the second heating step S20, a stress distribution can be formed in the transverse ribs 40 of the steel deck 10, such that tensile stress acts in the second heating target area AR2 and compressive stress acts in the first heating target area AR1. Furthermore, by performing the third heating step S30, a stress distribution can be formed in the transverse ribs 40 of the steel deck 10, such that tensile stress acts in the third heating target area AR3 and compressive stress acts in the first heating target area AR1.

[0037] By performing the first heating step S10, the second heating step S20, and the third heating step S30, a stress distribution F4 can be formed in which compressive stress acts on the central portion in the vertical direction in the figure, and tensile stress increases with increasing distance from the central portion in the vertical direction. This reduces the residual tensile stress in the transverse ribs 40 of the steel deck 10.

[0038] Fig. 9 is a diagram showing an example of stress distribution on the heated surface 41R of the transverse rib 40. Fig. 10 is a diagram showing an example of stress distribution on the non-heated surface 41S of the transverse rib 40. In Figs. 9 and 10, the vertical axis indicates the magnitude of residual stress, and the horizontal axis indicates the distance from the toe W1 of the transverse rib 40 in the up-down direction D3 (see the downward dashed two-dot arrow in Fig. 6).

[0039] 9 and 10 show simulation results for the first heating step S10, where the first heating temperature T1 is set to 250°C, 350°C, 450°C, and 550°C and the first heating time t1 is set to 35 seconds. In Fig. 9 and 10, curve C shows the residual stress distribution before the first heating step S10, curve C1 shows the stress distribution when the first heating step S10 is performed at a first heating temperature T1 of 250°C, curve C2 shows the stress distribution when the first heating step S10 is performed at a first heating temperature T1 of 350°C, curve C3 shows the stress distribution when the first heating step S10 is performed at a first heating temperature T1 of 450°C, and curve C4 shows the stress distribution when the first heating step S10 is performed at a first heating temperature T1 of 550°C.

[0040] 9 and 10, when the first heating temperature T1 is set to 250°C in the first heating step S10, the residual stress at the toe W1 is reduced to the same extent as when the first heating temperature T1 is set to 350°C, 450°C, or 550°C. Therefore, by setting the first heating temperature T1 to 250°C in the first heating step S10, the residual stress at the toe W1 can be reduced sufficiently and efficiently. Furthermore, by heating the heating target surface 41R in the first heating step S10, the residual stress at the toe W1a of the non-heated surface 41S can also be reduced without heating the non-heated surface 41S.

[0041] Fig. 11 is a diagram showing an example of stress distribution on the heated surface 41R of the transverse rib 40. Fig. 12 is a diagram showing an example of stress distribution on the non-heated surface 41S of the transverse rib 40. In Fig. 11 and Fig. 12, the vertical axis indicates the magnitude of residual stress, and the horizontal axis indicates the distance from the toe W1 of the transverse rib 40 in the up-down direction D3 (see the downward dashed two-dot arrow in Fig. 6).

[0042] 11 and 12 show simulation results for the case where the first heating temperature T1 is set to 250°C, and then the second heating temperature T2 and the third heating temperature T3 are set to 250°C, 350°C, 450°C, and 550°C, and the second heating time t2 and the third heating time t3 are set to 35 seconds, and the second heating step S20 and the third heating step S30 are respectively performed. 11 and 12, curve C shows the stress distribution before the first heating step S10, the second heating step S20, and the third heating step S30 are performed, curve C1 shows the stress distribution when the second heating step S20 and the third heating step S30 are performed with the second heating temperature T2 and the third heating temperature T3 set to 250°C, curve C2 shows the stress distribution when the second heating step S20 and the third heating step S30 are performed with the second heating temperature T2 and the third heating temperature T3 set to 350°C, curve C3 shows the stress distribution when the second heating step S20 and the third heating step S30 are performed with the second heating temperature T2 and the third heating temperature T3 set to 450°C, and curve C5 shows the stress distribution when the second heating step S20 and the third heating step S30 are performed with the second heating temperature T2 and the third heating temperature T3 set to 550°C.

[0043] 11 and 12, in the second heating step S20 and the third heating step S30, the residual stress at the toe W1 is reduced to the greatest extent when the second heating temperature T2 and the third heating temperature T3 are set to 550°C. In this case, the residual stress at the toe W1 is approximately 0 MPa. In the second heating step S20 and the third heating step S30, as in the first heating step S10, by heating the heating target surface 41R, it is possible to reduce the residual stress at the toe W1a of the non-heated surface 41S as well, without heating the non-heated surface 41S.

[0044] Furthermore, the simulation results shown in Figures 9 to 12 above suggest that by performing the first heating step S10, the second heating step S20 and the third heating step S30, it is possible to reduce the residual stress at the toe W1 to almost 0.

[0045] As described above, according to the first aspect of this embodiment, the present invention provides a deck plate 30, a horizontal rib 40 joined to the underside 30b of the deck plate 30, extending in the width direction D1 and having a strip-shaped cutout portion 43 extending downward from the upper end 41c so as to penetrate a first surface 41a and a second surface 41b on the front and rear sides in a bridge axis direction D2 perpendicular to the width direction D1, and a vertical rib 50 joined to the underside 30b of the deck plate 30 so as to extend in the bridge axis direction D2 and penetrate the cutout portion 43 of the horizontal rib 40 in the bridge axis direction D2. The method for reducing residual stress in a steel deck (10) includes a weld (60) that is arranged on both the first surface (41a) and the second surface (41b) of the transverse rib (40) so as to surround the longitudinal rib (50), joining the transverse rib (40) and the longitudinal rib (50), and that has linear welds (61, 62) along the front surface (50a) and the back surface (50b) of the longitudinal rib (50) in the width direction (D1) of the transverse rib (40), and a boxing weld (63) that surrounds the lower end (51) of the longitudinal rib (50), and the method for reducing residual stress in a steel deck (10) includes a weld (60) that is arranged on both the first surface (41a) and the second surface (41b) of the transverse rib (40) so as to surround the longitudinal rib (50), joining the transverse rib (40) and the longitudinal rib (50), and that has linear welds (61, 62) along the front surface (50a) and the back surface (50b) of the transverse rib (50), respectively, and a boxing weld (63) that surrounds the lower end (51) of the transverse rib (50), A first heating step S10 is performed to perform high-frequency induction heating on a first heating target area AR1 corresponding to the toe W1 of the boxing weld 63. After the first heating step S10, a second heating step S20 is performed to perform high-frequency induction heating on a second heating target area AR2 along the linear weld 61 extending on one side of the front and back surfaces of the vertical rib 50 of the weld 60 on the heating target surface 41R of the horizontal rib 40. After the second heating step S20, and a third heating step S30 in which high-frequency induction heating is performed on a third heating target area AR3 along the straight weld 62 extending to the other side of the back surface, and in the first heating step S10, the second heating step S20, and the third heating step S30, compressive stress acts on the first heating target area AR1, and high-frequency induction heating is performed to form a stress distribution in which tensile stress becomes stronger with increasing distance from the first heating target area AR1 in the direction along the toe W1 of the boxing weld 63.

[0046] According to this configuration, high-frequency induction heating is performed on the first heating target area AR1 corresponding to the toe W1 of the boxing weld 63 on the heating target surface 41R of the transverse rib 40, the second heating target area AR2 along one linear weld 61 of the weld 60, and the third heating target area AR3 along the other linear weld 62 of the weld 60. This results in a stress distribution in which compressive stress acts on the first heating target area AR1 and tensile stress increases with increasing distance from the first heating target area AR1 in the direction along the toe W1 of the boxing weld 63. This reduces residual stress in the transverse rib 40 of the steel deck 10. Furthermore, by heating the heating target surface 41R, residual stress can be reduced on both the heating target surface 41R and the non-heated surface 41S without heating the non-heated surface 41S. This allows for shorter construction times compared to construction along the toes W1 and W1a of the weld 60 from both sides of the transverse rib 40.

[0047] According to the second aspect of this embodiment, in the method for reducing residual stress in a steel deck relating to the first aspect, residual stress occurs near the welded portion due to welding during the manufacture of the bridge 100, and fatigue cracks occur due to the combination of the load of a moving object passing over the steel deck 10 supported by the main girder 20 of the bridge 100 and the residual stress.

[0048] With this configuration, when the steel deck 10 is used while being supported by the main girder 20 of the bridge 100, the residual stress in the weld can be efficiently reduced, and the occurrence of fatigue cracks due to the load of a moving object passing over the steel deck 10 can be suppressed.

[0049] According to the third aspect of this embodiment, in the method for reducing residual stress in a steel deck relating to the first or second aspect, the first heating temperature T1, which is the heating temperature of the first heating step S10, is lower than the second heating temperature T2, which is the heating temperature of the second heating step S20, and the third heating temperature T3, which is the heating temperature of the third heating step S30.

[0050] According to this configuration, the first heating step S10 can be carried out efficiently, while the residual stress on the transverse ribs 40 of the steel deck 10 can be appropriately reduced.

[0051] According to a fourth aspect of this embodiment, in the third method for reducing residual stress in a steel deck, the first heating temperature T1 is a temperature of 250°C or higher and 550°C or lower.

[0052] According to this configuration, by setting the first heating temperature T1 to a temperature of 250°C or higher and 550°C or lower, the first heating step S10 can be carried out efficiently while appropriately reducing residual stress in the transverse ribs 40 of the steel deck 10.

[0053] According to a fifth aspect of this embodiment, in the third method for reducing residual stress in a steel deck, the second heating temperature T2 and the third heating temperature T3 are temperatures of 250°C or higher and 550°C or lower.

[0054] According to this configuration, by setting the second heating temperature T2 and the third heating temperature T3 to a temperature of 250°C or higher and 550°C or lower, the residual stress on the transverse ribs 40 of the steel deck 10 can be appropriately reduced in the second heating step S20 and the third heating step S30.

[0055] According to the sixth aspect of this embodiment, in the method for reducing residual stress in a steel deck relating to the first to fifth aspects, the first heating time t1, which is the heating time of the first heating step S10, is shorter than the second heating time t2, which is the heating time of the second heating step S20, and the third heating time t3, which is the heating time of the third heating step S30.

[0056] According to this configuration, the first heating step S10 can be carried out efficiently, while the residual stress on the transverse ribs 40 of the steel deck 10 can be appropriately reduced.

[0057] According to a seventh aspect of this embodiment, in the method for reducing residual stress in a steel deck according to the sixth aspect, the first heating time t1 is a time period of 9 seconds or more and 20 seconds or less.

[0058] According to this configuration, by setting the first heating time t1 to a time of 9 seconds or more and 20 seconds or less, the first heating step S10 can be carried out efficiently while appropriately reducing residual stress in the transverse ribs 40 of the steel deck 10.

[0059] According to an eighth aspect of this embodiment, in the method for reducing residual stress in a steel deck according to the sixth aspect, the second heating time t2 and the third heating time t3 are 30 seconds or more and 40 seconds or less.

[0060] According to this configuration, by setting the second heating time t2 and the third heating time t3 to a period of 30 seconds or more and 40 seconds or less, the residual stress on the transverse ribs 40 of the steel deck 10 can be appropriately reduced in the second heating step S20 and the third heating step S30.

[0061] The technical scope of the present invention is not limited to the above-described embodiment, and appropriate modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, a new steel bridge has been described as an example of the bridge 100 to which the steel deck 10 is applied, but the present invention is not limited to this. For example, the steel deck 10 may be applied to an existing steel bridge, such as an existing steel road bridge or an existing steel railway bridge.

[0062] 13 and 14 are diagrams showing an example of a process for replacing a steel deck. As shown in step ST1 of FIG. 13 , when a deck 110 supported by a main girder 120 in a bridge 200 deteriorates, the deck 110 is replaced. In this case, as shown in step ST2, the upper part of the main girder 120, including the upper flange 123, is cut, leaving the lower flange 121 and a portion of the web 122 of the main girder 120. After cutting, the upper part of the main girder 120 and the deck 110 are removed. Then, as shown in step ST3, a structure formed by integrating a new steel deck 110A and a portion of the web 124 is attached to the cut portion 122a using an attachment mechanism 125. The steel deck 110A can be, for example, the steel deck 10 in the above embodiment. This allows for reconstruction into a bridge 200A equipped with the steel deck 10 in the above embodiment.

[0063] Furthermore, as shown in step ST4 of Figure 14, if the deck 210 supported by the main girder 220 of the bridge 300 deteriorates, the deck 210 is replaced. In this case, as shown in step ST5, the deck 210 is removed from the upper flange 233 of the main girder 220. Then, as shown in step ST6, a structure in which a new steel deck 210A and a portion 224 of the web are integrated is attached to the upper flange 233. For example, the steel deck 10 in the above embodiment is used as the steel deck 210A. This allows the bridge 300A to be reconstructed with the steel deck 10 in the above embodiment.

[0064] Furthermore, the timing of the first heating step S10, the second heating step S20, and the third heating step S30 in the above embodiment is not limited to when the steel deck 10 is manufactured in a factory, but can also be performed as a measure to improve fatigue durability after the steel deck 10 is applied to a bridge and begins use. However, if the first heating step S10, the second heating step S20, and the third heating step S30 are performed after use begins, the paint around the treatment area should be stripped before the treatment, and the treatment area should be repair painted after the treatment. Note that when applied to unpainted weathering steel bridges, paint stripping and repair painting are not necessary.

[0065] Furthermore, the steel deck 10 in the above embodiment has been described with an example of a configuration in which the welds 60 between the transverse ribs 40 and the vertical ribs 50 are welded all around, but the configuration is not limited to this as long as the welds 60 between the transverse ribs 40 and the vertical ribs 50 have box welds 63. Figure 15 is a diagram showing another example of the intersection between the transverse ribs and the vertical ribs of a steel deck. As shown in Figure 15, for example, a scallop 35 may be formed on the deck plate 30 side of the vertical rib 50.

[0066] Furthermore, the steel deck 10 in the above embodiment has been described with reference to an example in which the welds 60 between the horizontal ribs 40 and the vertical ribs 50 are fillet welds, but this is not limiting. For example, the welds 60 may be full penetration welds, partial penetration welds, or a combination of these with fillet welds.

[0067] Furthermore, in the above embodiment, the steel deck 10 has been described using the horizontal ribs 40 as the horizontal plates, but this is not limiting. The horizontal plates may be other structures such as cross beams, diaphragms, etc., as long as they are plate-like members extending in the width direction D1. [Explanation of symbols]

[0068] C,C1,C2,C3,C4 curve D1 Width direction D2 Bridge axis direction F0 Residual stress distribution D3 Up and down direction F1, F2, F3, F4 stress distribution S10 1st heating process T heating temperature S20 2nd heating process T1 1st heating temperature S30 3rd heating process T2 2nd heating temperature W1,W1a Toe T3 3rd heating temperature CL coil AR heating target area AR1 First heating target area AR2 Second heating target area AR3 Third heating target area d1,d2,d3 distance t Heating time t1 First heating time t2 Second heating time t3 Third heating time ST1,ST2,ST3,ST4,ST5,ST6 process 10,110A,210A Steel deck plate 20 Main digit 30 Deck Plate 30a Main surface 30b Bottom side 35 Scallop 40 Horizontal rib 41R Heating surface 41S Non-heated surface 41 Web 41a 1st page 41b 2nd side 41c top end 42 flange 43 Cutout 50 vertical ribs 50a surface 50b back side 51 Lower end 61,62 Straight weld 60 Welded Section 63 Box weld 100, 200, 200A, 300, 300A Bridges 110,110A,210,210A Floor slab 120,220 Main girder 121 Lower flange 122a Cutting point 122,232 Web 123,233 Upper flange 125 Mounting mechanism

Claims

1. Deck plate and a horizontal plate joined to the underside of the deck plate, extending in a first direction, and having a band-shaped cutout portion formed downward from an upper end so as to penetrate a first surface and a second surface on the front and back sides in a second direction perpendicular to the first direction; A vertical plate extending in the second direction and joined to the underside of the deck plate so as to penetrate the cutout portion of the horizontal plate in the second direction; a weld portion disposed on each of the first surface and the second surface of the horizontal plate so as to surround the vertical plate and join the horizontal plate and has linear weld portions along each of the front and back surfaces of the vertical plate in the first direction and a weld portion surrounding a lower end portion of the vertical plate; A method for reducing residual stress in a steel deck comprising: a first heating step of performing high-frequency induction heating on a first heating target area corresponding to a toe of a boxing weld of the weld, on a heating target surface which is one of the first surface and the second surface of the horizontal plate; After the first heating step, a second heating step is performed on the heating target surface of the horizontal plate, in which high-frequency induction heating is performed on a second heating target area along the linear weld portion of the weld portion extending to one side of the front surface and the back surface of the vertical plate; a third heating step of performing high-frequency induction heating on a third heating target area along the linear welded portion of the welded portion extending to the other side of the front surface and the back surface of the vertical plate on the heating target surface of the horizontal plate after the second heating step; Including, In the first heating step, the second heating step, and the third heating step, the high-frequency induction heating is performed so as to form a stress distribution in which a compressive stress acts on the first heating target area, and a tensile stress becomes stronger with increasing distance from the first heating target area in a direction along the toe of the end of the weld. A method for reducing residual stress in steel decks.

2. The residual stress is generated by welding during the construction of the bridge, and fatigue cracks occur when the residual stress is combined with the load of a moving object passing over the steel deck supported by the main girders of the bridge. A method for reducing residual stress in a steel deck according to claim 1.

3. A first heating temperature, which is a heating temperature in the first heating step, is lower than a second heating temperature, which is a heating temperature in the second heating step, and a third heating temperature, which is a heating temperature in the third heating step. A method for reducing residual stress in a steel deck according to claim 1.

4. The first heating temperature is equal to or higher than 250° C. and equal to or lower than 550° C. The method for reducing residual stress in a steel deck according to claim 3.

5. The second heating temperature and the third heating temperature are temperatures of 250° C. or more and 550° C. or less. The method for reducing residual stress in a steel deck according to claim 3.

6. A first heating time, which is a heating time of the first heating step, is shorter than a second heating time, which is a heating time of the second heating step, and a third heating time, which is a heating time of the third heating step. A method for reducing residual stress in a steel deck according to claim 1.

7. The first heating time is from 9 seconds to 40 seconds. A method for reducing residual stress in a steel deck according to claim 6.

8. The second heating time and the third heating time are 9 seconds or more and 40 seconds or less. A method for reducing residual stress in a steel deck according to claim 6.

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