JP2016194236A - Method of preventing generation of fatigue crack in steel deck slab and inner face pressing tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a tool capable of preventing deformation of a deck plate in a steel deck slab while preventing generation and development of a fatigue crack in a route part of a weld bead joining a trough rib and the deck plate.SOLUTION: In a loading step, a pressure is applied to a pair of side wall parts 6b and 6c from inside of a trough rib 6 so that the pair of side wall parts 6b and 6c of the trough rib 6 are deformed outward. In a pressure removal step, the pressure, which is applied in the loading step, is removed from the pair of side wall parts 6b and 6c.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a method for preventing the occurrence of fatigue cracks in a steel deck and an inner surface pressing device.

  Conventionally, steel decks are used in civil engineering structures such as bridges. Drawing 1 is a figure showing an example of a bridge provided with a steel deck. In FIG. 1, an X direction, a Y direction, and a Z direction orthogonal to each other are shown. The X direction indicates the length direction of the bridge 1, the Y direction indicates the width direction of the bridge 1, and the Z direction indicates the vertical direction. In the following description, the width direction of the bridge 1 is also referred to as the left-right direction.

  A bridge 1 shown in FIG. 1 has a steel deck 2. The steel deck 2 includes a deck plate 3, a plurality of main girders 4, a plurality of horizontal ribs 5, and a plurality of vertical ribs 6. The deck plate 3, the main girder 4, the lateral rib 5 and the longitudinal rib 6 are each made of steel.

  The deck plate 3 has a flat plate shape. The surface 3 a of the deck plate 3 is paved with a paving material 7. As the pavement material 7, for example, various materials such as asphalt or concrete can be used.

  The main girder 4 has an I shape in a cross section parallel to the YZ plane and is provided so as to extend in the length direction of the bridge 1. The upper end of the main beam 4 is welded to the back surface 3b of the deck plate 3, for example.

  The lateral rib 5 has an inverted T shape in a cross section parallel to the XZ plane, and is provided so as to extend in the width direction of the bridge 1. The left and right ends of the lateral rib 5 are welded to the main girder 4, for example.

  The vertical rib 6 has an open cross-sectional shape (in the example of FIG. 1, a substantially U shape) so as to open upward. The vertical ribs 6 are so-called truffles (U ribs). Hereinafter, the vertical rib 6 is referred to as a trough rib 6. Specifically, the trough rib 6 has a bottom wall portion 6a extending in the left-right direction and a pair of side wall portions 6b, 6c extending upward from both ends in the left-right direction of the bottom wall portion 6a. The side wall portions 6b and 6c are inclined with respect to the bottom wall portion 6a so that the distance between the side wall portions 6b and 6c increases toward the distal end side (upper side in FIG. 1). The trough rib 6 is provided so as to extend in the length direction of the bridge 1 and to penetrate the lateral rib 5. The upper end portions of the side wall portions 6 b and 6 c are welded to the back surface 3 b of the deck plate 3.

  In the bridge 1 having the above configuration, for example, a fatigue crack may occur in the steel slab 2 when the automobile 8 passes over the bridge 1. This fatigue crack occurs, for example, at the joint 9 between the deck plate 3 and the trough rib 6. Hereinafter, a mode of occurrence of fatigue cracks in the joint 9 will be described.

  FIG. 2 is an enlarged view showing a joint portion 9 between the trough rib 6 and the side wall portion 6b. As shown in FIG. 2, when the side wall portion 6 b is welded to the deck plate 3, for example, the outer portion 6 d of the front end portion of the side wall portion 6 b is joined to the deck plate 3 by the weld bead 10. Normally, the penetration amount of the weld bead 10 is based on 75% of the thickness of the trough rib, and the inner portion 6e of the front end portion of the side wall portion 6b is not joined. For this reason, a notch-shaped space 11 (hereinafter referred to as an unwelded portion 11) is formed between the deck plate 3, the weld bead 10, and the portion 6e. In such a joint 9, tensile residual stress is generated in the vicinity of the weld bead 10 due to expansion during welding and contraction after welding.

  Here, when the automobile 8 passes over the bridge 1, a load is applied to the deck plate 3, and the deck plate 3 bends. Thereby, bending stress and tensile stress are generated at the boundary between the deck plate 3 and the weld bead 10 and at the boundary between the side wall 6b and the weld bead 10. Of these stresses, the tensile stress generated in the width direction of the steel slab is superimposed on the above-described residual stress, so that a large tensile stress is likely to occur at the joint 9. When the load is repeatedly applied to the deck plate 3 by passing a plurality of automobiles 8, fatigue occurs in the vicinity of the boundary portion between the deck plate 3 and the weld bead 10 and in the vicinity of the boundary portion between the side wall portion 6 b and the weld bead 10. Cracks may occur. For example, fatigue cracks occur in the toe 12 on the deck plate 3 side or the toe 13 on the side wall 6b side of the weld bead 10, or fatigue cracks occur in the root portion 14 on the deck plate 3 side. Thereby, there exists a possibility that the intensity | strength of the steel deck 2 may fall.

  By the way, in the steel deck 2, the toe 12 and the toe 13 are located outside the trough rib 6. For this reason, the fatigue crack which generate | occur | produced in the toe 12 and the toe 13 is easy to be discovered by the operator at the time of the inspection of the bridge 1, etc. In this case, since the portion where the fatigue crack has occurred can be repaired at an early stage, it is easy to prevent the strength reduction of the steel deck 2.

  On the other hand, since the root portion 14 is in a position that cannot be seen from the outside of the trough rib 6, it is difficult to find a fatigue crack that has occurred in the root portion 14. Even if it is found that a fatigue crack has occurred in the root portion 14, it is difficult to repair the root portion 14 from the outside of the trough rib 6. For this reason, when a fatigue crack occurs in the root portion 14, it is necessary to repair the root portion 14 from the inside of the truffle 6, and it takes time and labor to repair the fatigue crack.

  Therefore, conventionally, techniques for preventing the occurrence of fatigue cracks in the root portion 14 have been proposed.

  For example, Patent Document 1 describes a peening method. In the method described in Patent Document 1, the surface of the deck plate is hit by a peening tool in a steel deck using a U-rib. Patent Document 1 describes that compressive residual strain can be applied to an inner portion of a U-rib by applying a hit as described above. In the method described in Patent Document 1, it is considered that by applying compressive residual stress as described above, the progress of fatigue cracks generated in the inner portion of the U rib is suppressed.

JP 2014-172043 A

  However, in the above method, since the front surface side of the deck plate is hit with a peening tool, it is difficult to give a sufficiently large compressive residual stress to the rear surface side of the deck plate. In this case, the progress of fatigue cracks or the occurrence of fatigue cracks cannot be sufficiently suppressed. Further, if a sufficiently large compressive residual stress is to be generated on the back side of the deck plate, the deck plate must be hit with a large force, which may cause deformation of the deck plate.

  The present invention has been made to solve such problems, and in a steel slab, fatigue cracks are generated in a root portion of a weld bead that joins a trough rib and a deck plate while preventing deformation of the deck plate. Another object of the present invention is to provide a method and an apparatus capable of preventing fatigue crack growth.

  The gist of the present invention is the following method for preventing the occurrence of fatigue cracks and an inner surface pressing device of a steel deck. In the present invention, “preventing fatigue cracks” not only prevents the occurrence of new fatigue cracks but also means that the existing fatigue cracks are further prevented from further expanding and expanding.

(1) A method for preventing the occurrence of fatigue cracks in a steel deck having a configuration in which the tip ends of a pair of side wall portions of a truffle are welded to the back surface of a deck plate,
A loading step of applying pressure from the inside of the trough rib to the pair of side wall portions so that the pair of side wall portions deform toward the outside of the truffle rib;
A method for preventing the occurrence of fatigue cracks in a steel slab, comprising: an unloading step for removing pressure applied to the pair of side wall portions in the loading step.

(2) In the loading step, the method for preventing the occurrence of fatigue cracks in the steel slab according to (1), wherein the pair of side wall portions is pressed toward the outside by the curved surface portions of the pair of pressing members each having a curved surface portion. .

(3) In a cross section perpendicular to the longitudinal direction of the truffle, the distance between the center of curvature of the curved surface portion and the back surface in the thickness direction of the deck plate is d1, and the position of the side wall portion before the loading step In the case where the distance in the direction parallel to the back surface with the position of the side wall portion after the unloading step is the residual displacement amount,
(1) The residual displacement at a position d1 away from the back surface in the thickness direction of the deck plate is set to a value in a range of 0.01 to 3 mm by executing the loading step and the unloading step. Or the fatigue crack generation | occurrence | production prevention method of the steel slab of (2).

(4) The method for preventing occurrence of fatigue cracks in a steel deck according to (3) above, wherein the loading step and the unloading step are repeated until the residual displacement reaches a value in the range of 0.01 to 3 mm.

(5) The method according to (3) or (4) above, wherein the distance d1 is 1.5 times or more the thickness of the side wall portion.

(6) The method according to (3) or (4) above, wherein the distance d1 is not more than 7 times the thickness of the side wall portion.

(7) An inner surface pressing device that is disposed and used inside the trough rib to perform the fatigue crack generation preventing method according to any one of (1) to (6) above,
The main body,
A support part for supporting the main body part so that the main body part can move in the longitudinal direction of the trough rub,
A pair of pressing members supported by the main body so as to be movable with respect to the main body;
An inner surface pressing device comprising: a drive mechanism that moves the pair of pressing members such that the pair of pressing members presses the pair of side wall portions of the trough rib toward the outside of the trough rib.

(8) a movement amount detection unit that detects a movement amount of the pressing member;
A load detector for detecting a load applied to the pressing member;
Based on the movement amount detected by the movement amount detection unit and the load detected by the load detection unit, the distance between the position of the side wall portion before the loading step and the position of the side wall portion after the unloading step. The inner surface pressing device according to (7), further comprising: a distance detection unit that detects.

  According to the present invention, in a steel deck having a truffle, it is possible to suppress the occurrence of fatigue cracks and the development of fatigue cracks in the root portion of the weld bead while preventing deformation of the deck plate.

Drawing 1 is a figure showing an example of a bridge provided with a steel deck. FIG. 2 is an enlarged view showing a joint portion between the vertical rib and the side wall portion. FIG. 3 is a view for explaining a fatigue crack generation preventing method according to an embodiment of the present invention. FIG. 4 is a view for explaining a fatigue crack generation preventing method according to an embodiment of the present invention. FIG. 5 is a diagram for explaining the operational effects of the fatigue crack generation preventing method according to the present embodiment. FIG. 6 is a view for explaining the configuration of another pressing member that can be used in carrying out the present invention. FIG. 7 is a diagram for explaining the analysis model of the truffle used in the simulation. FIG. 8 is a graph showing the FEM analysis results. FIG. 9 is a graph showing the FEM analysis results. FIG. 10 is a graph showing the FEM analysis results. FIG. 11 is a graph showing the FEM analysis results. FIG. 12 is a graph showing the FEM analysis results. FIG. 13 is a plan view showing a schematic configuration of the inner surface pressing device according to the embodiment of the present invention. FIG. 14 is a diagram for explaining an example of use of the inner surface pressing device. FIG. 15 is a plan view showing a schematic configuration of an inner surface pressing device according to another embodiment of the present invention.

(Explanation of fatigue crack prevention method)
The present invention will be described in detail below. 3 and 4 are diagrams for explaining a fatigue crack generation preventing method according to an embodiment of the present invention. In the following description, a case where a fatigue crack generation preventing method (hereinafter also simply referred to as a preventing method) according to the present invention is applied to the steel deck 2 shown in FIGS. 1 and 2 will be described. In the steel deck 2 to which the present invention is applied, the thickness of the deck plate 3 is, for example, 6 to 35 mm, and the thickness of the trough rib 6 is, for example, 3 to 12 mm.

  The prevention method according to the present invention may be performed on the steel deck 2 before being used as a component of the bridge 1, and the steel deck 2 in a state of being used as a component of the bridge 1. You may implement it. In addition, the prevention method according to the present invention may be performed on the steel deck 2 in which the main girder 4 and the lateral rib 5 are not provided, and in the state in which the main girder 4 and the lateral rib 5 are provided. You may implement with respect to the steel deck 2. Below, the case where the prevention method which concerns on this invention is implemented with respect to the steel deck 2 of the state before using as the component of the bridge 1 and the main girder 4 and the horizontal rib 5 is not provided is demonstrated. . In the following description, the vertical direction and the direction perpendicular to the longitudinal direction of the truffle 6 are defined as the width direction of the truffle 6. In FIG. 3, the horizontal direction is the width direction of the truffle 6.

  With reference to FIG. 3, in the present embodiment, for example, a steel floor is placed on the work table 15 so that the deck plate 3 is at the bottom and the trough rib 6 (more specifically, the bottom wall portion 6 a) is at the top. Place version 2.

  Next, a pair of pressing members 16 are arranged in the trough rib 6. The pressing member 16 has a curved surface portion 16a having a circular arc cross section. In the cross section perpendicular to the length direction of the trough rib 6, the curvature radius of the curved surface portion 16a is set to, for example, 5 to 80 mm.

  In the present embodiment, the pressing member 16 is provided so as to extend in the length direction of the trough rib 6. More specifically, the length of the curved surface portion 16a in the longitudinal direction of the trough rib 6 is set to 4 to 50 times the thickness t of the side wall portions 6b and 6c, for example. The curved surface portion 16a of one pressing member 16 is provided to face the inner surface of the side wall portion 6b, and the curved surface portion 16a of the other pressing member 16 is provided to face the inner surface of the side wall portion 6c. The pressing member 16 is provided so as to be movable in the left-right direction, and moves in the left-right direction when driven by a drive mechanism (not shown).

  In the present embodiment, the distance d1 between the curvature center 16b of the curved surface portion 16a and the back surface 3b of the deck plate 3 is set to, for example, 1.5 times or more, preferably 2 times or more the thickness t of the side wall portions 6b and 6c. More preferably, it is set to 3 times or more. Further, the distance d1 is set to be, for example, 7 times or less of the thickness t of the side wall portions 6b and 6c, preferably 5 times or less, and more preferably 4 times or less. The distance d1 is the length in the thickness direction (vertical direction in FIG. 3) of the deck plate 3. The thickness t is calculated as, for example, the average thickness of the side wall portions 6b and 6c.

  Next, with reference to FIG. 3 and FIG. 4A, the pair of pressing members 16 are moved toward the outside of the trough rib 6 to contact the inner surfaces of the side wall portions 6b and 6c. With reference to FIG. 3, in the present embodiment, the side walls 6 b and 6 c are inclined with respect to the deck plate 3 so that the distance between the side walls 6 b and 6 c decreases as the distance from the deck plate 3 increases. For this reason, with reference to Fig.4 (a), the contact part 17 of the curved surface part 16a of one press member 16 and the side wall part 6b is located above the curvature center 16b. Although explanation is omitted, the other pressing member 16 also contacts the side wall portion 6c in the same manner. In the following, the relationship between the side wall 6b and the one pressing member 16 will be described, but the relationship between the side wall 6c and the other pressing member 16 is the same.

  Next, as shown in FIG. 4 (b), the pressing member 16 is moved toward the outside of the truffle 6 (loading step). As a result, pressure is applied to the side wall portion 6b from the inside of the trough rib 6. As a result, the side wall portion 6 b is deformed so as to swell toward the outside of the trough fibril 6. In addition, the moving distance d2 of the pressing member 16 in the loading process is set to 0.05 to 10 mm, for example. In the present embodiment, in the loading process, for example, pressure is applied to the side wall portion 6b so that the vicinity of the root portion 14 is plastically deformed.

  Next, with reference to FIG.4 (c), the press member 16 is moved so that it may leave | separate from the side wall part 6b (unloading process). Thereby, the pressure applied to the side wall part 6b in the loading process is removed. As a result, the side wall 6b is deformed so as to return to the shape of the side wall 6b before the loading process. In the present embodiment, as described above, the vicinity of the root portion 14 is plastically deformed in the loading process. Therefore, the side wall part 6b after the unloading process does not completely return to the shape of the side wall part 6b before the loading process.

  Here, in the cross section perpendicular to the longitudinal direction of the trough rib 6, the distance in the left-right direction between the position of the side wall 6b before the loading process and the position of the side wall 6b after the unloading process is defined as a residual displacement. In the present embodiment, in a cross section perpendicular to the longitudinal direction of the truffle 6, the arbitrary position of the outer surface (or inner surface) of the side wall portion 6b before the loading process and the outer surface (or inner surface) of the side wall portion 6b after the unloading process. The distance in the left-right direction from an arbitrary position is defined as a residual displacement amount. In FIG. 4C, a residual displacement amount at a position away from the back surface 3b in the thickness direction of the deck plate 3 by a distance d1 is shown as a distance d3 (hereinafter referred to as a residual displacement amount d3). In the present embodiment, the loading process and the unloading process are performed so that the residual displacement d3 is 0.01 to 3 mm. The number of executions of the loading process and the unloading process may each be one, or may be two or more. That is, the loading process and the unloading process may be repeatedly executed until the residual displacement d3 reaches a value in the range of 0.01 to 3 mm. From the viewpoint of maintaining the shape and section modulus of the trough rib 6, the residual displacement d3 is preferably 1 mm or less. Further, from the viewpoint of preventing the lateral rib 5 from being buckled out of the plane, the residual displacement d3 is preferably 1 mm or less. In order to accurately measure the residual displacement d3, the residual displacement d3 is preferably 0.1 mm or more. The residual displacement amount d3 can be measured using, for example, a micrometer.

  Hereinafter, the effect of the fatigue crack generation preventing method according to the present embodiment will be described. FIG. 5 is a diagram for explaining the operational effects of the fatigue crack generation preventing method according to the present embodiment.

  With reference to FIG. 5, as described above, in the vicinity of the root portion 14 of the weld bead 10, tensile residual stress is generated due to expansion during welding and contraction after welding. In this state, by performing the above-described loading process, the side wall portion 6b tends to move toward the outside of the trough rib 6. As a result, the weld bead 10 is pulled toward the outer side of the trough rib 6, and the tensile stress near the root portion 14 temporarily increases.

  After that, by executing the unloading process, the side wall 6 b tends to move toward the inside of the trough rib 6. As a result, the weld bead 10 is pressed toward the inside of the truffle 6. That is, a force in the compression direction is applied near the root portion 14. Thereby, the compressive residual stress can be generated on the contrary in the place where the tensile residual stress portion is in the vicinity of the root portion 14.

  As described above, in the present embodiment, by executing the loading process and the unloading process, the compressive residual stress can be generated in the vicinity of the root portion 14 where the tensile residual stress was generated during welding. it can. Thereby, for example, even when a load is repeatedly applied to the steel deck 2, it is possible to prevent a large tensile stress from being generated in the vicinity of the root portion 14. As a result, fatigue cracks can be prevented from occurring near the root portion 14. Moreover, when the fatigue crack has already generate | occur | produced in the vicinity of the root part 14, it will generate a compressive residual stress in the crack tip, and it can prevent that a fatigue crack progresses.

  In the embodiment, it is not necessary to apply a force directly to the deck plate 3. Thereby, the deformation | transformation and damage of the deck plate 3 can be prevented.

  In the present embodiment, pressure is applied to the side wall portions 6b and 6c by the pressing member 16 having the curved surface portion 16a. In this case, it is possible to prevent the inner surface of the truffle 6 from being damaged.

  In the present embodiment, the residual displacement d3 is set to a value in the range of 0.01 to 3 mm. In this case, it is possible to prevent the truffle 6 from being deformed excessively. Thereby, it is possible to prevent the strength of the truffle 6 itself from being lowered.

  In the present embodiment, the distance d1 between the curvature center 16b of the curved surface portion 16a and the back surface 3b of the deck plate 3 is set to, for example, 1.5 times or more the thickness t of the side wall portions 6b and 6c. In this case, even if the weld bead 10 has entered the inside of the trough rib 6, it can be prevented that the weld bead 10 itself is pushed by the pressing member 16. Thereby, damage to the weld bead 10 can be prevented.

  In the present embodiment, the distance d1 is set to be seven times or less of the thickness t of the side wall portions 6b and 6c, for example. In this case, a force in the compression direction can be sufficiently applied in the vicinity of the root portion 14 in the unloading process while suppressing the movement amount of the pressing member 16 in the loading process. Thereby, it is possible to sufficiently prevent the occurrence of fatigue cracks in the vicinity of the root portion 14 while preventing the truffle 6 from being deformed excessively.

  In the above-described embodiment, the case where the fatigue crack generation preventing method according to the present invention is implemented using the pressing member 16 having the curved surface portion 16a has been described, but the pressing member that can be used in the present invention is not limited to the above-described example.

  FIG. 6 is a view for explaining the configuration of another pressing member that can be used in carrying out the present invention.

  Each of the pair of pressing members 18 shown in FIG. 6 includes a flat surface portion 18a facing the inner surface of the side wall portion 6b, a curved surface portion 18b extending from the upper end of the flat surface portion 18a toward the center side of the trough rib 6, and a lower end of the flat surface portion 18a. And a curved surface portion 18c extending toward the center of the truffle 6. The curved surface portions 18b and 18c are formed by chamfering, for example. The pair of pressing members 18 are provided so as to be movable in the left-right direction, like the pressing member 16.

  When the present invention is carried out using the pressing member 18, for example, the distance d4 between the center 18d and the back surface 3b in the vertical direction of the flat portion 18a is considered in the same manner as the above-mentioned distance d1, and the loading process and unloading are performed. Execute the process. Thereby, the same operation effect as the above-mentioned embodiment is obtained.

  In the above-described embodiment, the case where the present invention is applied to the steel deck 2 having the truffle rib 6 having a U-shaped cross section has been described. However, the present invention can also be applied to a steel deck having a truffle rib having a V-shaped cross section. .

  In the example shown in FIG. 4, the residual displacement d <b> 3 is defined with respect to the outer surface of the side wall portion 6 b in the cross section perpendicular to the longitudinal direction of the trough fibril 6. However, as described above, the residual displacement d3 may be defined based on the inner surface of the side wall 6b.

  In addition, after the above-mentioned loading process and unloading process, in order to further remove the residual stress in the vicinity of the root portion 14, the surface 3a of the deck plate 3 may be hit using a peening apparatus or the like. In this case, since the surface 3a is hit after the residual stress of the root portion 14 is removed by the loading process and the unloading process described above, the residual stress of the root portion 14 can be sufficiently increased without applying a large force to the surface 3a. Can be removed. Thereby, it is possible to sufficiently prevent the occurrence of fatigue cracks in the root portion 14 while preventing deformation and damage of the deck plate 3.

(Study based on simulation)
Hereinafter, the effects of the present invention will be described together with simulation results by FEM analysis using a computer. FIG. 7 is a diagram for explaining an FEM analysis model of the truffle 6 used in the simulation. Specifically, FIG. 7A is a diagram showing an analysis model of the truffle 6, and FIG. 7B is an enlarged view of a portion corresponding to the joint 9 in the analysis model, and FIG. () Is a diagram showing a mesh and integration points of a portion corresponding to the periphery of the insulative portion 11 (portion indicated by a dotted circle in FIG. 7B) in the analysis model.

  As shown in FIG. 7A, a two-dimensional 1/2 model of the truffle 6 was created as an FEM analysis model using a four-node two-dimensional plane strain element in consideration of symmetry. In FIG. 7A, the constraint points of the analysis model are indicated by triangular symbols. In addition, as shown in FIGS. 7B and 7C, in the analysis model, the welded portion 11 was formed in a notch shape. Although not shown in FIG. 7, in this simulation, the loading step and the unloading step were performed with the curvature radius r of the curved surface portion 16 a (see FIG. 3) of the pressing member 16 (see FIG. 3) set to 35 mm. The value of the distance d1 shown in FIG. 3 was set to 1.5t (t is the thickness of the side wall portion 6b: 6 mm), 2t, 2.5t, 3t, 4t, 5t, and 7t.

  In the FEM analysis, it was assumed that SMB490B (JIS G3106 2008) was used as the material of the steel deck 2 and its stress-strain diagram was used. The Young's modulus was set to 206 GPa and the Poisson's ratio was set to 0.3, respectively, and FEM analysis was performed according to the isotropic hardening rule.

  Referring to FIG. 7C, the analysis is performed under the above-described conditions, and the data of the integration point on the deck plate 3 side in the vicinity of the tip of the welded portion 11 is output, and the route portion 14 (see FIG. 5). The stress of was determined. In this simulation, the stress in the direction parallel to the width direction of the trough rib 6 (left and right direction in FIG. 3) was obtained. 8 to 10 to be described later, a positive stress indicates a tensile stress, and a negative stress indicates a compressive stress.

  8 and 9 show the relationship between the amount of displacement of the side wall portion and the stress generated in the root portion 14. The displacement amount of the side wall portion refers to the displacement amount of the outer surface of the side wall portion 6b at a position away from the back surface 3b of the deck plate 3 by the distance d1 with reference to FIG.

  As can be seen from FIG. 8 and FIG. 9, by executing the loading process, the displacement amount of the side wall portion 6 b increases and tensile stress is generated in the root portion 14. And when the displacement amount of the side wall part 6b increases further and the root part 14 vicinity begins to deform plastically, a tensile stress will reduce. Thereafter, by executing the unloading step, the displacement amount of the side wall portion 6b is reduced, and the tensile stress of the root portion 14 is also reduced as the displacement amount is reduced. By further reducing the amount of displacement of the side wall portion 6b, a compressive stress is generated in the root portion.

  From the results shown in FIGS. 8 and 9, even if a tensile residual stress is generated in the root portion 14 when the side wall portion 6 b and the deck plate 3 are welded, the load of the prevention method according to the embodiment of the present invention is not limited. It can be seen that a force in the compression direction can be applied to the root portion 14 by executing the process and the unloading process. Specifically, by executing the loading step, a tensile force is further applied to the root portion 14 where a tensile residual stress is generated during welding. Thereby, the route part 14 partially surrenders. After that, by executing the unloading step, compressive residual stress can be generated in the root portion 14 by deformation restraint from the elastic region around the root portion 14. As a result, fatigue cracks can be prevented from occurring in the root portion 14.

  FIG. 10 is a diagram illustrating the relationship between the residual displacement d3 after the unloading process and the stress (residual compressive stress) generated in the root portion 14. In FIG. FIG. 10 shows that when the distance d1 is 5 t or less, sufficient compressive stress is generated in the root portion 14 even if the residual displacement d3 is 1 mm or less. Specifically, in this analysis, a compressive stress of 800 MPa or more could be generated. From this, it can be seen that by setting the distance d1 to 5 t or less, it is possible to sufficiently prevent the occurrence of fatigue cracks in the root portion 14 while suppressing the deformation of the truffle 6.

  FIG. 10 shows that a desired compressive stress can be obtained by adjusting the residual displacement d3 according to the distance d1. In addition, when the distance d1 is 2t to 5t (particularly 3t or more), it can be seen that a sufficiently large compressive stress (for example, a compressive stress of 800 MPa or more) can be obtained with a wide range of residual displacement d3. . In other words, it can be seen that when the distance d1 is 2t to 5t (particularly 3t or more), the residual displacement d3 can be easily managed.

  FIG. 11 is a diagram illustrating the relationship between the residual displacement d3 and the maximum load in the loading process. FIG. 11 shows that the larger the distance d1, the larger the residual displacement d3 can be secured with a small load. In particular, it can be seen that when the distance d1 is 3t or more, the residual displacement d3 can be sufficiently increased with a small load.

  FIG. 12 is a diagram showing the relationship between the residual displacement d3 after the unloading process and the strain of the root portion 14. As shown in FIG. From FIG. 12, it can be seen that the strain generated in the root portion 14 can be reduced by increasing the value of the distance d1.

  Here, referring to FIG. 10 to FIG. 12, the compressive stress and the maximum load when the residual displacement d3 is 0.2 mm when the distance d1 is 2t and when the distance d1 is 1.5t. Compare the strain values. Then, it can be seen that when the distance d1 is 2t, the maximum load and strain are reduced, but the compressive stress is increased. That is, when the residual displacement amount d3 is set to 0.2 mm, setting the distance d1 to 2t suppresses the distortion of the root portion 14 than setting the distance d1 to 1.5t. 14, compressive stress can be generated efficiently. From this, by carrying out the present invention under appropriate conditions considering the performance of the device to be used and the dimensions of the longitudinal ribs 6 and the like, compressive stress is efficiently generated in the root part 14 while suppressing distortion of the root part 14. You can see that

  In addition, although detailed description is abbreviate | omitted, also when it analyzed according to the kinematic hardening rule, the effect of this invention has been confirmed similarly to the above-mentioned simulation.

(Description of inner surface pressing device)
Hereinafter, an inner surface pressing device according to an embodiment of the present invention will be described. FIG. 13 is a plan view showing a schematic configuration of an inner surface pressing device (hereinafter abbreviated as a pressing device) 20 according to an embodiment of the present invention.

  Referring to FIG. 13, the pressing device 20 includes a main body 22, wheels 24 a to 24 d, axles 26 a and 26 b, drive mechanisms 28 and 30, movement amount detection units 32 a and 32 b, load detection units 34 a and 34 b, and a distance detection unit. 36, a communication unit 38, and the pair of pressing members 16 described above.

  In the present embodiment, the main body 22 houses drive mechanisms 28 and 30, movement amount detection units 32 a and 32 b, load detection units 34 a and 34 b, a distance detection unit 36, and a communication unit 38. The wheels 24a and 24b are rotatably supported by the main body 22 through the axle 26a. The wheels 24c and 24d are rotatably supported by the main body 22 through the axle 26b. In the present embodiment, the wheels 24a to 24d include magnets. In the present embodiment, the wheels 24 a to 24 d and the axles 26 a and 26 b correspond to a support portion that supports the main body portion 22.

  The drive mechanism 28 includes, for example, an electric motor, and rotationally drives the wheels 24a and 24b via the axle 26a. Thereby, the pressing device 20 moves. As shown in FIG. 13, in the following, the direction in which the pressing device 20 moves is referred to as the front-rear direction. Further, the left-right direction is defined based on the front-rear direction.

  The pair of pressing members 16 are supported by the main body 22 so as to be movable in the left-right direction at the center in the front-rear direction of the main body 22. For example, the drive mechanism 30 moves the pair of pressing members 16 in the left-right direction by hydraulic pressure.

  The movement amount detection unit 32 a detects the movement amount of one pressing member 16, and the movement amount detection unit 32 b detects the movement amount of the other pressing member 16. The detection results of the movement amount detection units 32 a and 32 b are output to the distance detection unit 36. As the movement amount detection units 32a and 32b, for example, a known displacement sensor can be used. Therefore, detailed description of the movement amount detection units 32a and 32b is omitted.

  The load detection unit 34 a detects a load applied to one pressing member 16, and the load detection unit 34 b detects a load applied to the other pressing member 16. The detection results of the load detectors 34 a and 34 b are output to the distance detector 36. In addition, as load detection part 34a, 34b, a well-known load sensor can be used, for example. Therefore, detailed description of the load detection units 34a and 34b is omitted.

  As will be described later, the distance detection unit 36, based on the detection results of the movement amount detection units 32a and 32b and the load detection units 34a and 34b, the side wall portions 6b and 6c (see FIG. 3) of the truffle 6 (see FIG. 3). The residual displacement of is detected. The detection result of the distance detection unit 36 is output to the communication unit 38.

  The communication unit 38 transmits / receives data to / from a remote operation device (not shown). In the present embodiment, for example, the operator of the pressing device 20 can operate the pressing device 20 via the remote operation device. In the present embodiment, for example, a control signal for controlling the drive mechanisms 28 and 30 is output from the remote operation device based on the operation of the operator, and the control signal is received by the communication unit 38. The communication unit 38 outputs the received control signal to the drive mechanisms 28 and 30. Thereby, the drive mechanisms 28 and 30 are controlled. Further, the detection result of the distance detection unit 36 is transmitted to the remote operation device via the communication unit 38. Thereby, the operator of the pressing device 20 can control the pressing device 20 with reference to the detection result of the distance detection unit 36 transmitted to the remote control device.

  FIG. 14 is a diagram for explaining an example of use of the pressing device 20. Referring to FIG. 14, when using the pressing device 20, the pressing device 20 is disposed inside the truffle 6. As described above, in the present embodiment, the wheels 24a to 24d include magnets. Therefore, the wheels 24a to 24d can be attached to the back surface 3b of the deck plate 3 by magnetic force in a state where the deck plate 3 is on and the bottom wall portion 6a is on the bottom. For example, the wheels 24 a to 24 d can be attached to the back surface 3 b of the deck plate 3 in a state where the steel deck 2 (see FIG. 1) is used as a constituent member of the bridge 1 (see FIG. 1). As described above, the pressing device 20 can move in the front-rear direction. As a result, the pressing device 20 can move in the length direction of the trafry 6 inside the trafry 6.

  After arrange | positioning the press apparatus 20 as mentioned above, a pair of press member 16 is moved to the left-right direction, and the above-mentioned load process and unloading process are performed. Thereafter, the pressing device 20 is advanced to execute the loading process and the unloading process. By repeating the above operation, the above loading process and unloading process can be performed over the entire length of the truffle 6.

  In the pressing device 20, the residual displacement amount of the side wall portion can be detected as follows. In the following, the method for detecting the residual displacement amount of the side wall portion 6b will be described, but the method for detecting the residual displacement amount of the side wall portion 6c is also the same.

  Referring to FIG. 14, first, in the loading step, the curved surface portion 16a contacts the side wall portion 6b by moving the pressing member 16 from the reference position (zero point) to the side wall portion 6b. When the curved surface portion 16a contacts the side wall portion 6b, the load applied to the pressing member 16 is greatly increased. For this reason, the distance detection part 36 can detect that the curved surface part 16a contacted the side wall part 6b based on the detection result of the load detection part 34a. Moreover, the distance detection part 36 detects the movement amount (movement amount from a reference position) of the pressing member 16 when the curved surface part 16a contacts the side wall part 6b based on the detection result of the movement amount detection part 32a. Can do. Hereinafter, the movement amount of the pressing member 16 when the curved surface portion 16a contacts the side wall portion 6b is referred to as a first movement amount.

  Next, in the unloading step, the curved surface portion 16a is separated from the side wall portion 6b by moving the pressing member 16 to the main body portion 22 side. When the curved surface portion 16a is separated from the side wall portion 6b, the load applied to the pressing member 16 is greatly reduced. For this reason, the distance detection part 36 can detect that the curved surface part 16a left | separated from the side wall part 6b based on the detection result of the load detection part 34a. Moreover, the distance detection part 36 can detect the movement amount of the pressing member 16 when the curved surface part 16a leaves | separates from the side wall part 6b based on the detection result of the movement amount detection part 32a. Hereinafter, the movement amount (movement amount from the reference position) of the pressing member 16 when the curved surface portion 16a is separated from the side wall portion 6b is referred to as a second movement amount.

  Finally, the distance detection unit 36 obtains the difference between the first movement amount and the second movement amount detected as described above. Thereby, the distance detection part 36 is a distance (in this embodiment, the direction parallel to the back surface 3b of the deck plate 3) of the position of the side wall part 6b before the said loading process, and the position of the side wall part 6b after the said unloading process. Can be detected. That is, in the present embodiment, the distance detection unit 36 can determine the residual displacement amount of the side wall portion 6b by calculating the difference between the first movement amount and the second movement amount detected as described above. . Specifically, the distance detection unit 36 can obtain the residual displacement amount of the side wall portion 6b by subtracting the first movement amount from the second movement amount.

  Although a detailed description is omitted, in the pressing device 20, the pair of pressing members 18 described above may be used instead of the pair of pressing members 16.

  For example, the shape of one pressing member and the other pressing member may be different. Specifically, for example, the length of one pressing member in the front-rear direction (length direction of the truffle 6) may be different from the length of the other pressing member in the front-rear direction. The pressing device having such a configuration is used, for example, when the amount of penetration of the weld bead 10 is greatly different between the side wall 6b side and the side wall 6c side. Moreover, although detailed description is abbreviate | omitted, it is not necessary to implement simultaneously the press of the side wall part by one press member, and the press of the side wall part by the other press member. For example, after performing the loading process and the unloading process with one pressing member, the loading process and the unloading process may be performed with the other pressing member. Such a processing method is used, for example, when performing the loading process and the unloading process while measuring the amount of blurring of the position of the side walls 6b, 6c in the left-right direction (the width direction of the truffle 6).

  Moreover, although detailed description is abbreviate | omitted, the press apparatus 20 may be provided with the suspension. For example, the axle 26a and the axle 26b may be supported by the main body 22 via suspensions. In this case, when the pair of pressing members 16 press the side wall portions 6b and 6c, the main body portion 22 can move in the vertical direction. Specifically, for example, the main body 22 sinks to the deck plate 3 side. Thereby, the force applied to the wheels 24a, 24b and the axles 26a, 26b can be reduced, and deterioration with time of the wheels 24a, 24b and the axles 26a, 26b can be suppressed.

  Moreover, although detailed description is abbreviate | omitted, the press apparatus 20 may be comprised so that the main-body part 22 can move to the left-right direction with respect to axle 26a, 26b. With this configuration, when the side wall portions 6b and 6b are pushed by the pair of pressing members 16, the main body portion 22 can be easily moved to the center between the side wall portion 6b and the side wall portion 6c. Thereby, for example, even when there is a difference between the displacement amount of the side wall portion 6b and the displacement amount of the side wall portion 6c, an appropriate force can be applied from the pair of pressing members 16 to the side wall portions 6b and 6c.

  FIG. 15 is a plan view showing a schematic configuration of a pressing device 20a according to another embodiment of the present invention. The pressing device 20a shown in FIG. 15 differs from the pressing device 20 described above in the following points. The pressing device 20 a according to the present embodiment includes a pair of pressing members 40 instead of the pair of pressing members 16. Each pressing member 40 includes a holding portion 40a that is moved by the drive mechanism 30 and a pressing portion 40b that is rotatably held at the tip of the holding 40a. The pressing part 40b has a circular shape in plan view. Although a detailed description is omitted, a curved surface portion similar to the curved surface portion 16a is formed on the outer peripheral surface of the pressing portion 40b.

  When using the pressing device 20a, the loading process is executed in the same manner as the pressing device 20 described above. Thereafter, the pressing device 20a is advanced in a state where the outer peripheral surfaces of the pair of pressing portions 40b are in contact with the side wall portions 6b and 6c. Thereby, a pair of press part 40b also moves and the pressure added to the side wall parts 6b and 6c in the said load process can be removed. On the other hand, pressure is applied to a portion of the side wall portions 6b and 6c where the pair of pressing portions 40b are newly contacted. That is, by moving the pressing device 20a in the length direction of the truffle 6, the above loading process and unloading process can be continuously performed over the entire length direction of the truffle 6.

  In addition, although the above-mentioned embodiment demonstrated the case where a support part was comprised by wheel 24a-24d and axle 26a, 26b, the support part may be provided with the crawler. In the above-described embodiment, the case where the hydraulic drive mechanism 30 is used has been described. However, the drive mechanism 30 may have a configuration in which a pair of pressing members are moved using a motor or the like, and the air pressure is increased. You may have the structure which uses and moves a pair of press member.

  In the above-described embodiment, the case where the wheels 24a to 24d include magnets has been described, but the wheels 24a to 24d may not include magnets. In this case, for example, a guide rail extending in the length direction of the truffle 6 is fixed to the back surface 3b of the deck plate 3 by a magnet. Further, the main body portion 22 is coupled to the guide rail so that the main body portion 22 can move in the length direction of the trough rib 6 along the guide rail. Thereby, even if the wheels 24a to 24d do not include magnets, the pressing devices 20 and 20a can be moved on the back surface 3b of the deck plate 3. In addition, for example, a conveying device such as a belt conveyor may be fixed to the back surface of the back surface 3b by a magnet, and the pressing devices 20 and 20a may be suspended from the conveying device. Then, the pressing devices 20 and 20a may be moved in the length direction of the truffle 6 by the transport device.

  According to the present invention, in the steel deck, it is possible to prevent the occurrence of fatigue cracks and the development of fatigue cracks at the root portion of the weld bead that joins the truffle and the deck plate while preventing the deformation of the deck plate. Therefore, the present invention can be suitably used for preventing the occurrence of fatigue cracks in steel decks constituting bridges and the like.

1 Bridge 2 Steel slab 3 Deck plate 4 Main girder 5 Horizontal rib 6 Trough rib (vertical rib)
DESCRIPTION OF SYMBOLS 7 Pavement material 8 Automobile 9 Joint part 10 Weld bead 11 Non-welding part 12, 13 Toe 14 Root part 15 Work table 16, 18, 40 Press member 20, 20a Inner surface pressing device 22 Main-body part 24a-24d Wheel 26a, 26b Axle 28, 30 Drive mechanism 32a, 32b Movement amount detection unit 34a, 34b Load detection unit 36 Distance detection unit 38 Communication unit 40a Holding unit 40b Pressing unit

Claims (8)

A method for preventing the occurrence of fatigue cracks in a steel slab having a structure in which the front ends of a pair of side walls of trough ribs are welded to the back surface of a deck plate,
A loading step of applying pressure from the inside of the trough rib to the pair of side wall portions so that the pair of side wall portions deform toward the outside of the truffle rib;
A method for preventing the occurrence of fatigue cracks in a steel slab, comprising: an unloading step for removing pressure applied to the pair of side wall portions in the loading step.   2. The method for preventing the occurrence of fatigue cracks in a steel slab according to claim 1, wherein in the loading step, the pair of side wall portions are pressed toward the outside by the curved surface portions of the pair of pressing members each having a curved surface portion. In a cross section perpendicular to the length direction of the truffle, the distance between the center of curvature of the curved surface portion and the back surface in the thickness direction of the deck plate is d1, and the position of the side wall portion and the unloading before the loading step In the case where the distance in the direction parallel to the back surface with the position of the side wall portion after the process is a residual displacement amount,
The residual displacement amount at a position separated by d1 from the back surface in the thickness direction of the deck plate is set to a value in a range of 0.01 to 3 mm by executing the loading step and the unloading step. The method for preventing the occurrence of fatigue cracks in the steel slab as described.   The method according to claim 3, wherein the loading step and the unloading step are repeated until the residual displacement reaches a value in the range of 0.01 to 3 mm.   5. The method for preventing the occurrence of fatigue cracks in a steel deck according to claim 3, wherein the distance d <b> 1 is 1.5 times or more the thickness of the side wall portion.   5. The method for preventing the occurrence of fatigue cracks in a steel deck according to claim 3, wherein the distance d <b> 1 is not more than 7 times the thickness of the side wall portion. In order to carry out the fatigue crack occurrence prevention method according to any one of claims 1 to 6, an inner surface pressing device that is disposed and used inside the truffle,
The main body,
A support part for supporting the main body part so that the main body part can move in the longitudinal direction of the trough rub,
A pair of pressing members supported by the main body so as to be movable with respect to the main body;
An inner surface pressing device comprising: a drive mechanism that moves the pair of pressing members such that the pair of pressing members presses the pair of side wall portions of the trough rib toward the outside of the trough rib. A movement amount detection unit for detecting a movement amount of the pressing member;
A load detector for detecting a load applied to the pressing member;
Based on the movement amount detected by the movement amount detection unit and the load detected by the load detection unit, the distance between the position of the side wall portion before the loading step and the position of the side wall portion after the unloading step. The inner surface pressing device according to claim 7, further comprising: a distance detection unit that detects

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