JP6536365B2 - Method for preventing fatigue cracking of steel floor slab and inner surface pressing device - Google Patents

Description

  The present invention relates to a method for preventing fatigue cracking of a steel floor slab and an inner surface pressing device.

  Conventionally, steel floor slabs are used in civil engineering structures such as bridges. FIG. 1 is a view showing an example of a bridge provided with a steel floor slab. In addition, in FIG. 1, the X direction, Y direction, and Z direction which mutually orthogonally cross 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.

  The bridge 1 shown in FIG. 1 has a steel floor slab 2. The steel floor slab 2 has a deck plate 3, a plurality of main girders 4, a plurality of transverse ribs 5, and a plurality of longitudinal ribs 6. The deck plate 3, the main girder 4, the transverse 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 by the paving material 7. As the pavement material 7, various materials, such as asphalt or concrete, can be used, for example.

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

  The transverse rib 5 has an inverted T shape in a cross section parallel to the XZ plane, and is provided 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 longitudinal rib 6 has an open cross-sectional shape (substantially U-shaped in the example of FIG. 1) so as to open upward. The longitudinal rib 6 is a so-called trough rib (U rib). The longitudinal ribs 6 are hereinafter referred to as trough ribs 6. Specifically, the trough rib 6 has a bottom wall 6a extending in the left-right direction, and a pair of side walls 6b and 6c extending upward from both ends in the left-right direction of the bottom wall 6a. The side wall portions 6b and 6c are inclined with respect to the bottom wall portion 6a such that the distance between the side wall portions 6b and 6c increases toward the tip end side (upper side in FIG. 1). The trough rib 6 is provided to extend in the longitudinal direction of the bridge 1 and to penetrate the transverse 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, when the car 8 passes over the bridge 1, fatigue cracks may occur in the steel floor slab 2. This fatigue crack occurs, for example, at the joint portion 9 between the deck plate 3 and the trough rib 6. Hereinafter, the generation mode of the fatigue crack in the joint portion 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 welding the side wall 6 b to the deck plate 3, for example, an outer portion 6 d of the tip of the side wall 6 b is joined to the deck plate 3 by the weld bead 10. Usually, 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 tip of the side wall portion 6b is not joined. Therefore, a notch-shaped space 11 (hereinafter referred to as a non-welded 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 car 8 passes over the bridge 1, a load is applied to the deck plate 3 and the deck plate 3 is bent. Thereby, bending stress or tensile stress is generated at the boundary between the deck plate 3 and the weld bead 10 and at the boundary between the side wall 6 b and the weld bead 10. Among these stresses, the tensile stress generated in the width direction of the steel floor slab is superimposed on the above-described residual stress, so that a large tensile stress tends to be generated in the joint 9. When the load is repeatedly applied to the deck plate 3 by passing a plurality of vehicles 8, fatigue near the boundary between the deck plate 3 and the weld bead 10 and near the boundary between the side wall 6b and the weld bead 10 Cracks may occur. For example, a fatigue crack may occur in the toe 12 on the deck plate 3 side of the weld bead 10 or the toe 13 on the side wall portion 6b side, or a fatigue crack may occur in the root portion 14 on the deck plate 3 side. Thereby, the strength of the steel floor slab 2 may be reduced.

  By the way, in the steel floor slab 2, the toe 12 and the toe 13 are located outside the trough rib 6. For this reason, fatigue cracks generated at the toe 12 and the toe 13 are likely to be detected by the worker when the bridge 1 is inspected or the like. In this case, it is possible to quickly repair the portion where the fatigue crack has occurred, so it is easy to prevent the strength reduction of the steel floor slab 2.

  On the other hand, since the root portion 14 is at a position not visible from the outside of the trough rib 6, it is difficult to find a fatigue crack that has occurred in the root portion 14. Moreover, even if it is discovered that fatigue cracks have 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 trough rib 6, and it takes time and labor to repair the fatigue crack.

  Then, the technique for preventing that a fatigue crack generate | occur | produces in the root part 14 conventionally is proposed.

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

JP, 2014-172043, A

  However, in the above method, since the surface side of the deck plate is hit by the peening tool, it is difficult to apply a sufficiently large compressive residual stress to the back side of the deck plate. In this case, the development of fatigue cracks or the occurrence of fatigue cracks can not be sufficiently suppressed. In addition, if an attempt is made to generate a compressive residual stress of a sufficient magnitude on the back surface side of the deck plate, the deck plate must be struck with a large force, so the deck plate may be deformed.

  The present invention has been made to solve such a problem, and in a steel floor plate, fatigue cracking is caused at the root portion of a weld bead for joining a trough rib and a deck plate while preventing deformation of the deck plate. And providing a method and apparatus capable of preventing fatigue crack growth.

  The present invention is summarized as a method of preventing fatigue cracking of a steel floor slab described below and an inner surface pressing device. In the present invention, the prevention of the occurrence of fatigue cracks means not only the prevention of the generation of new fatigue cracks but also the prevention of the further development and expansion of the already existing fatigue cracks.

(1) A method of preventing fatigue cracking of a steel floor slab having a configuration in which the front ends of a pair of side walls of a trough rib are welded to the back surface of a deck plate
Applying a pressure from the inside of the trough rib to the pair of side walls so that the pair of side walls deform toward the outside of the trough rib;
And C. removing the pressure applied to the pair of side walls in the loading step.

(2) In the load step, the method for preventing fatigue cracking of a steel floor slab according to (1) above, wherein the pair of side wall portions are pressed outward by the curved surface portions of the pair of pressing members having curved surface portions respectively. .

(3) In a cross section perpendicular to the length direction of the trough rib, 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 a case where a distance in a direction parallel to the back surface with the position of the side wall portion after the unloading step is a residual displacement amount,
The residual displacement at a position d1 away from the back surface in the thickness direction of the deck plate is made a value in the range of 0.01 to 3 mm by performing the loading step and the unloading step. Or (2) a method for preventing fatigue cracking of a steel floor slab.

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

(5) The method for preventing fatigue cracking of a steel floor slab according to the above (3) or (4), wherein the distance d1 is 1.5 times or more the thickness of the side wall portion.

(6) The method for preventing fatigue cracking of a steel floor slab according to (3) or (4) above, wherein the distance d1 is 7 times or less the thickness of the side wall portion.

(7) An inner surface pressing device which is disposed and used inside the trough rib in order to carry out the method for preventing fatigue cracking according to any one of (1) to (6) above,
Body part,
A support portion for supporting the main body portion so that the main body portion can move in the longitudinal direction of the trough rib;
A pair of pressing members movably supported by the main body with respect to the main body;
And a drive mechanism for moving 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 the movement amount of the pressing member;
A load detection unit that detects a load applied to the pressing member;
The distance between the position of the side wall before the loading step and the position of the side wall after the unloading step based on the moving amount detected by the moving amount detector and the load detected by the load detector The inner surface pressing device according to (7), further including: a distance detection unit that detects

  According to the present invention, in a steel floor slab having a trough rib, it is possible to suppress fatigue crack initiation and fatigue crack growth in the root portion of a weld bead while preventing deformation of the deck plate.

FIG. 1 is a view showing an example of a bridge provided with a steel floor slab. FIG. 2 is an enlarged view showing a joint between the longitudinal rib and the side wall. 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 figure for demonstrating the effect of the fatigue crack generation | occurrence | production prevention method which concerns on this embodiment. FIG. 6 is a view for explaining the configuration of another pressing member that can be used when practicing the present invention. FIG. 7 is a diagram for explaining an analysis model of trough ribs used in the simulation. FIG. 8 is a graph showing the results of FEM analysis. FIG. 9 is a graph showing the results of FEM analysis. FIG. 10 is a graph showing the results of FEM analysis. FIG. 11 is a graph showing the results of FEM analysis. FIG. 12 is a graph showing the results of FEM analysis. FIG. 13 is a plan view showing a schematic configuration of an inner surface pressing device according to an embodiment of the present invention. FIG. 14 is a view 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.

(Description of fatigue crack occurrence prevention method)
Hereinafter, the present invention will be described in detail. FIG. 3 and FIG. 4 are views for explaining a fatigue crack generation preventing method according to an embodiment of the present invention. In addition, in the following, the case where the fatigue crack generation prevention method (it is also only called the prevention method hereafter) which concerns on this invention in the steel floor slab 2 shown to FIG. 1 and FIG. 2 is demonstrated. In the steel floor slab 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.

  In addition, the prevention method according to the present invention may be performed on the steel floor slab 2 before being used as a component of the bridge 1, and the steel floor slab 2 in a state of being used as a component of the bridge 1 It may be implemented for Moreover, the prevention method according to the present invention may be performed on the steel floor plate 2 in a state 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 floor plate 2. In the following, there will be described a case where the prevention method according to the present invention is applied to the steel floor slab 2 in a state in which the main girder 4 and the lateral rib 5 are not provided before being used as a component of the bridge 1 . In the following description, a direction perpendicular to the vertical direction and the length direction of the trough rib 6 is taken as the width direction of the trough rib 6. In FIG. 3, the left and right direction is the width direction of the trough rib 6.

  Referring to FIG. 3, in the present embodiment, for example, a steel floor on work bench 15 such that deck plate 3 is down and trough rib 6 (more specifically, bottom wall 6 a) is up. Put the edition 2.

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

  In the present embodiment, the pressing member 16 is provided to extend in the longitudinal 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, for example, 4 to 50 times the thickness t of the side wall portions 6b and 6c. 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 movably in the left-right direction, and moves in the left-right direction by being 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 or more times the thickness t of the side wall portions 6b and 6c, preferably 2 or more times Is more preferably set to 3 times or more. Further, the distance d1 is set to, for example, 7 times or less, preferably 5 times or less, more preferably 4 times or less of the thickness t of the side wall portions 6b and 6c. The distance d1 is a length in the thickness direction of the deck plate 3 (vertical direction in FIG. 3). The thickness t is calculated, for example, as the average thickness of the side wall portions 6b and 6c.

  Next, referring to FIGS. 3 and 4A, the pair of pressing members 16 is moved toward the outside of the trough rib 6 to contact the inner surfaces of the side wall portions 6b and 6c. Referring to FIG. 3, in the present embodiment, the side wall portions 6 b and 6 c are inclined with respect to the deck plate 3 so that the distance between the side wall portions 6 b and 6 c becomes narrower as the distance from the deck plate 3 increases. Therefore, referring to FIG. 4A, the contact portion 17 between the curved surface portion 16a of the one pressing member 16 and the side wall portion 6b is located above the center of curvature 16b. Although the description is omitted, the other pressing member 16 also contacts the side wall 6c. In addition, although the relationship between the side wall part 6b and one press member 16 is demonstrated below, the relationship between the side wall part 6c and the other press member 16 is also the same.

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

  Next, referring to FIG. 4 (c), the pressing member 16 is moved away from the side wall 6b (unloading process). Thereby, the pressure applied to the side wall 6b in the loading step is removed. As a result, the side wall 6b deforms so as to return to the shape of the side wall 6b before the loading step. In the present embodiment, as described above, the vicinity of the root portion 14 is plastically deformed in the loading step. Therefore, the side wall 6b after the unloading process does not completely return to the shape of the side wall 6b before the loading process.

  Here, in the cross section perpendicular to the length direction of the trough rib 6, the distance in the left-right direction between the position of the side wall 6b before the loading step and the position of the side wall 6b after the unloading step is taken as the residual displacement amount. In this embodiment, in a cross section perpendicular to the longitudinal direction of the trough rib 6, between an arbitrary position of the outer surface (or inner surface) of the sidewall 6b before the loading step and the outer surface (or inner surface) of the sidewall 6b after the unloading step. Let distance in the left-right direction with arbitrary positions be residual displacement amount. In FIG. 4C, the residual displacement at a position separated by a distance d1 from the back surface 3b in the thickness direction of the deck plate 3 is shown as a distance d3 (hereinafter referred to as a residual displacement d3). In the present embodiment, the loading step and the unloading step are performed such that the residual displacement amount d3 is 0.01 to 3 mm. The number of executions of the loading step and the unloading step may be one or two or more. That is, the loading step and the unloading step may be repeatedly performed until the residual displacement amount d3 becomes a value in the range of 0.01 to 3 mm. From the viewpoint of maintaining the shape and cross section coefficient of the trough rib 6, it is preferable that the residual displacement amount d3 is 1 mm or less. Further, also from the viewpoint of preventing the out-of-plane buckling of the lateral ribs 5, it is preferable that the residual displacement amount d3 is 1 mm or less. Moreover, in order to measure residual displacement amount d3 accurately, it is preferable that residual displacement amount d3 is 0.1 mm or more. The residual displacement amount d3 can be measured, for example, using a micrometer.

  Hereinafter, the effect of the fatigue crack generation | occurrence | production prevention method which concerns on this embodiment is demonstrated. FIG. 5 is a figure for demonstrating the effect of the fatigue crack generation | occurrence | production prevention method which concerns on this embodiment.

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

  Thereafter, the sidewall 6 b tries to move toward the inside of the trough rib 6 by performing the unloading process. Thereby, the weld bead 10 is pressed toward the inside of the trough rib 6. That is, a force in the compression direction is applied in the vicinity of the root portion 14. As a result, compressive residual stress can be generated in the vicinity of the residual stress portion of tension near the root portion 14.

  As described above, in the present embodiment, by performing the loading step and the unloading step, the compressive residual stress is generated in the vicinity of the root portion 14 where the tensile residual stress has been generated at the time of welding. it can. As a result, for example, even when a load is repeatedly applied to the steel floor slab 2, generation of a large tensile stress in the vicinity of the root portion 14 can be prevented. As a result, fatigue cracks can be prevented from occurring in the vicinity of the root portion 14. In addition, when a fatigue crack has already occurred in the vicinity of the root portion 14, compressive residual stress is generated at the tip of the crack, which can prevent the fatigue crack from developing.

  Moreover, in the form of this embodiment, it is not necessary to apply force to the deck plate 3 directly. Thereby, deformation and damage of the deck plate 3 can be prevented.

  In the present embodiment, pressure is applied to the side wall portions 6 b and 6 c by the pressing member 16 having the curved surface portion 16 a. In this case, the inner surface of the trough rib 6 can be prevented from being damaged.

  In the present embodiment, the residual displacement amount d3 is set to a value in the range of 0.01 to 3 mm. In this case, it is possible to prevent the trough rib 6 from being deformed excessively. This can prevent the strength of the trough rib 6 itself from being reduced.

  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 or more times the thickness t of the side wall portions 6b and 6c. In this case, even if the weld bead 10 has penetrated to the inside of the trough rib 6, it is possible to prevent the weld bead 10 itself from being 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, for example, seven times or less the thickness t of the side wall portions 6b and 6c. In this case, it is possible to sufficiently apply a force in the compression direction to the vicinity of the root portion 14 in the unloading step while suppressing the amount of movement of the pressing member 16 in the loading step. Thereby, it is possible to sufficiently prevent the occurrence of fatigue cracks in the vicinity of the root portion 14 while preventing the trough rib 6 from being excessively deformed.

  Although the above-mentioned embodiment explained the case where the fatigue crack generating prevention method concerning the present invention was carried out using pressing member 16 which has curved surface part 16a, the pressing member which can be used by the present invention is not limited to the above-mentioned example.

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

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

  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 distance d1 described above. Perform the process Thereby, the same effect as the above-mentioned embodiment is obtained.

  Although the above-mentioned embodiment explained the case where the present invention was applied to the steel floor plate 2 which has the trough rib 6 of U-shaped cross section, the present invention is applicable also to the steel floor plate which has the trough rib of V-shaped cross section. .

  In the example shown in FIG. 4, in the cross section perpendicular to the longitudinal direction of the trough rib 6, the residual displacement amount d3 is defined with reference to the outer surface of the side wall 6b. However, as described above, the residual displacement amount d3 may be defined with reference to the inner surface of the side wall 6b.

  In addition, after the above-mentioned loading process and unloading process, in order to remove the residual stress near the root part 14 further, you may strike on the surface 3a of the deck plate 3 using a peening apparatus etc. In this case, since the impact is applied to the surface 3a after removing the residual stress of the root portion 14 by the above-described loading step and unloading step, the residual stress of the root portion 14 is sufficiently sufficient without applying a large force to the surface 3a. It can be removed. This makes it 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 trough rib 6 used in the simulation. Specifically, FIG. 7 (a) is a view showing an analysis model of the trough rib 6, and FIG. 7 (b) is an enlarged view of a portion corresponding to the joint portion 9 in the analysis model. Fig. 7 is a diagram showing meshes and integration points of a portion corresponding to the periphery of the non-welded portion 11 (a portion shown by a dotted circle in Fig. 7 (b)) in the analysis model.

  As shown in FIG. 7A, a two-dimensional 1⁄2 model of the trough rib 6 was created in consideration of the symmetry as an FEM analysis model using a four-node two-dimensional plane strain element. In FIG. 7A, the constraint points of the analysis model are indicated by triangular symbols. Moreover, as shown to FIG.7 (b), (c), in the analysis model, the non-welding part 11 was formed in 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 16a (see FIG. 3) of the pressing member 16 (see FIG. 3) being 35 mm. The values of the distance d1 shown in FIG. 3 are set to 1.5 t (t is the thickness of the side wall 6 b: 6 mm), 2 t, 2.5 t, 3 t, 4 t, 5 t and 7 t.

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

  Referring to FIG. 7C, analysis is performed under the conditions as described above, and data of integration points on the deck plate 3 side in the vicinity of the end of the non-welded portion 11 is output, and the route portion 14 (see FIG. 5) Stress was determined. In this simulation, stress in a direction parallel to the width direction of the trough rib 6 (horizontal direction in FIG. 3) was determined. In FIGS. 8 to 10 described later, positive values of stress indicate tensile stress, and negative values of stress indicate compressive stress.

  FIG. 8 and FIG. 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 of the side wall refers to the displacement of the outer surface of the side wall 6b at a position separated by a distance d1 from the back surface 3b of the deck plate 3 with reference to FIG.

  As can be seen from FIGS. 8 and 9, by performing the loading step, the amount of displacement of the side wall portion 6b is increased, and a tensile stress is generated in the root portion 14. Then, when the amount of displacement of the side wall portion 6 b further increases and the vicinity of the root portion 14 starts to be plastically deformed, the tensile stress decreases. Thereafter, the amount of displacement of the side wall 6b is reduced by performing the unloading process, and the tensile stress of the root portion 14 is also reduced according to the reduction of the amount of displacement. As the amount of displacement of the side wall portion 6 b is further reduced, compressive stress is generated in the root portion 14.

  From the results shown in FIG. 8 and FIG. 9, even if residual stress of tension is generated in the root portion 14 when welding the side wall portion 6b and the deck plate 3, the load of the preventing method according to the embodiment of the present invention It can be seen that by performing the process and the unloading process, a force in the direction of compression can be applied to the root portion 14. Specifically, by performing the loading process, a tensile force is further applied to the root portion 14 in which a tensile residual stress is generated during welding. As a result, the root portion 14 partially surrenders. Thereafter, by performing the unloading process, compressive residual stress can be generated in the root portion 14 due to the deformation restraint from the elastic region around the root portion 14. As a result, the occurrence of fatigue cracks in the root portion 14 can be prevented.

  FIG. 10 is a view showing the relationship between the residual displacement amount d3 after the unloading process and the stress (residual compressive stress) occurring in the root portion 14. As shown in FIG. It can be seen from FIG. 10 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 amount d3 is 1 mm or less. Specifically, in this analysis, a compressive stress of 800 MPa or more could be generated. From this, it is understood 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 trough rib 6.

  It can be understood from FIG. 10 that a desired compressive stress can be obtained by adjusting the residual displacement amount d3 in accordance with the distance d1. In addition, when the distance d1 is 2t to 5t (especially, 3t or more), it can be seen that a compressive stress (e.g., a compressive stress of 800MPa or more) of sufficient magnitude can be obtained with a wide range of residual displacement d3. . In other words, when the distance d1 is 2t to 5t (particularly, 3t or more), it can be understood that management of the residual displacement amount d3 is facilitated.

  FIG. 11 is a diagram showing the relationship between the residual displacement amount d3 and the maximum load in the loading step. It can be seen from FIG. 11 that as the distance d1 is larger, a larger residual displacement amount d3 can be secured with a smaller load. In particular, when the distance d1 is 3 t or more, it is understood that the residual displacement amount d3 can be sufficiently increased with a small load.

  FIG. 12 is a view showing the relationship between the residual displacement amount d3 and the strain of the root portion 14 after the unloading process. It can be understood from FIG. 12 that the distortion generated in the root portion 14 can be reduced by increasing the value of the distance d1.

  Here, referring to FIGS. 10 to 12, the compressive stress and the maximum load when the residual displacement amount d3 is 0.2 mm when the distance d1 is 2 t and when the distance d1 is 1.5 t. Let's compare the value of and the strain. Then, it can be seen that the maximum load and strain become smaller as the distance d1 is 2t, but the compressive stress becomes larger. That is, when the residual displacement amount d3 is set to 0.2 mm, setting the distance d1 to 2 t suppresses distortion of the root portion 14 while setting the distance d1 to 1.5 t, while suppressing the root portion The compressive stress can be generated efficiently at 14. From this, by implementing the present invention under appropriate conditions in consideration of the performance of the device to be used and the dimensions of the longitudinal rib 6, etc., compressive stress is efficiently generated in the root portion 14 while suppressing distortion of the root portion 14. It turns out that you can

  In addition, although detailed description is abbreviate | omitted, also when it analyzed according to a movement hardening rule, the effect of this invention was able to be 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 detectors 32 a and 32 b, load detectors 34 a and 34 b, and a distance detector 36, the communication unit 38, and the pair of pressing members 16 described above.

  In the present embodiment, the main body 22 houses the drive mechanisms 28, 30, the movement amount detectors 32a, 32b, the load detectors 34a, 34b, the distance detector 36, and the communication unit 38. The wheels 24a and 24b are rotatably supported by the main body 22 via an axle 26a. The wheels 24c and 24d are rotatably supported by the main body 22 via the axle 26b. In the present embodiment, the wheels 24 a to 24 d 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 that supports the main body 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 and right direction is defined with reference to the front and rear direction.

  The pair of pressing members 16 is supported by the main body 22 so as to be movable in the left-right direction at a central portion in the front-rear direction of the main body 22. The drive mechanism 30 moves the pair of pressing members 16 in the left-right direction, for example, 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 detectors 32 a and 32 b are output to the distance detector 36. In addition, as displacement amount detection part 32a, 32b, a well-known displacement sensor can be used, for example. 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 detection units 34 a and 34 b are output to the distance detection unit 36. In addition, as load detection part 34a, 34b, a well-known load sensor can be used, for example. Therefore, detailed description of load detection parts 34a and 34b is omitted.

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

  The communication unit 38 transmits and receives data to and from a remote control device (not shown). In the present embodiment, for example, the operator of the pressing device 20 can steer the pressing device 20 via the remote control device. In the present embodiment, for example, based on the operation of the operator, a control signal for controlling the drive mechanisms 28 and 30 is output from the remote control device, 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. Thus, the drive mechanisms 28 and 30 are controlled. Further, the detection result of the distance detection unit 36 is transmitted to the remote control device via the communication unit 38. Thus, the operator of the pressing device 20 can steer 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 view for explaining an example of use of the pressing device 20. As shown in FIG. Referring to FIG. 14, when using the pressing device 20, the pressing device 20 is disposed inside the trough rib 6. As described above, in the present embodiment, the wheels 24 a to 24 d include magnets. Therefore, the wheels 24a to 24d can be attached to the back surface 3b of the deck plate 3 by the magnetic force, with the deck plate 3 at the top and the bottom wall 6a at the bottom. For example, the wheels 24a to 24d can be attached to the back surface 3b of the deck plate 3 in a state where the steel floor slab 2 (see FIG. 1) is used as a component of the bridge 1 (see FIG. 1). Further, as described above, the pressing device 20 can move in the front-rear direction. Thus, the pressing device 20 can move in the longitudinal direction of the trough rib 6 inside the trough rib 6.

  After the pressing device 20 is disposed as described above, the pair of pressing members 16 is moved in the left-right direction, and the above-described loading step and unloading step are performed. Thereafter, the pressing device 20 is advanced to carry out the loading step and the unloading step. By repeating the above operation, the loading and unloading steps described above can be performed throughout the length of the trough rib 6.

  In the pressing device 20, the amount of residual displacement of the side wall can be detected as follows. In addition, although the detection method of the residual displacement amount of the side wall part 6b is demonstrated below, the detection method of the residual displacement amount of the side wall part 6c is also the same.

  Referring to FIG. 14, first, in the loading step, the curved surface portion 16 a contacts the side wall portion 6 b by moving the pressing member 16 from the reference position (zero point) to the side wall portion 6 b side. The load applied to the pressing member 16 is greatly increased by the curved surface portion 16a contacting the side wall portion 6b. Therefore, the distance detection unit 36 can detect that the curved surface portion 16a contacts the side wall portion 6b based on the detection result of the load detection unit 34a. In addition, based on the detection result of the movement amount detection unit 32a, the distance detection unit 36 detects the movement amount (movement amount from the reference position) of the pressing member 16 when the curved surface portion 16a contacts the side wall portion 6b. Can. 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 process, 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 largely reduced. For this reason, the distance detection unit 36 can detect that the curved surface portion 16a is separated from the side wall portion 6b based on the detection result of the load detection unit 34a. Further, the distance detection unit 36 can detect the movement amount of the pressing member 16 when the curved surface portion 16a is separated from the side wall portion 6b based on the detection result of the movement amount detection unit 32a. Hereinafter, the amount of movement of the pressing member 16 (the amount of movement from the reference position) 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. Thus, the distance detection unit 36 measures the distance between the position of the side wall 6b before the loading step and the position of the side wall 6b after the unloading step (in the embodiment, a direction parallel to the back surface 3b of the deck plate 3). Distance) can be detected. That is, in the present embodiment, the distance detection unit 36 can obtain the residual displacement of the side wall 6b by calculating the difference between the first movement and the second movement detected as described above. . Specifically, the distance detection unit 36 can obtain the residual displacement amount of the side wall 6 b by subtracting the first movement amount from the second movement amount.

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

  Also, for example, the shapes of one pressing member and the other pressing member may be different. Specifically, for example, the length in the front-rear direction (longitudinal direction of the trough rib 6) of one pressing member may be different from the length in the front-rear direction of the other pressing member. The pressing device having such a configuration is used, for example, when the amount of penetration of the weld bead 10 is largely different between the side wall portion 6 b and the side wall portion 6 c. Although detailed description is omitted, pressing of the side wall by one pressing member and pressing of the side wall by the other pressing member may not be simultaneously performed. For example, after the loading step and the unloading step are performed by one pressing member, the loading step and the unloading step may be performed by the other pressing member. Such a processing method is used, for example, when performing the loading step and the unloading step while measuring the amount of displacement of the position of the side wall portions 6b and 6c in the left-right direction (the width direction of the trough rib 6).

  Moreover, although detailed description is abbreviate | omitted, the press apparatus 20 may be equipped with a suspension. For example, the axle 26a and the axle 26b may be supported by the main body 22 via the suspension. In this case, when the pair of pressing members 16 presses 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 and 24b and the axles 26a and 26b can be reduced, and the deterioration with time of the wheels 24a and 24b and the axles 26a and 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 be moved to the left-right direction with respect to axle shaft 26a, 26b. With this configuration, when the side walls 6b and 6b are pressed by the pair of pressing members 16, the main body 22 can be easily moved to the center between the side wall 6b and the side wall 6c. Thereby, even when there is a difference between the displacement of the side wall 6b and the displacement of the side wall 6c, for example, an appropriate force can be applied from the pair of pressing members 16 to the side walls 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 above-described pressing device 20 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 has a holding portion 40a moved by the drive mechanism 30, and a pressing portion 40b rotatably held at the tip end of the holding 40a. The pressing portion 40 b has a circular shape in plan view. Although the detailed description is omitted, a curved surface portion similar to the curved surface portion 16 a is formed on the outer peripheral surface of the pressing portion 40 b.

  When the pressing device 20a is used, the loading process is performed in the same manner as the above-described pressing device 20. Thereafter, the pressing device 20a is advanced with the outer peripheral surfaces of the pair of pressing portions 40b in contact with the side wall portions 6b and 6c. As a result, the pair of pressing portions 40b also move, and the pressure applied to the side wall portions 6b and 6c in the loading step can be removed. On the other hand, pressure is applied to the portions of the side wall portions 6b and 6c where the pair of pressing portions 40b newly contact. That is, by moving the pressing device 20 a in the longitudinal direction of the trough rib 6, the above-described loading process and unloading process can be continuously performed over the entire longitudinal direction of the trough rib 6.

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

  Although the above-mentioned embodiment explained the case where wheels 24a-24d contained a magnet, wheels 24a-24d do not need to contain a magnet. In this case, for example, a guide rail extending in the longitudinal direction of the trough rib 6 is fixed to the back surface 3 b of the deck plate 3 by a magnet. Further, the main body portion 22 is connected to the guide rail so that the main body portion 22 can be moved in the longitudinal direction of the trough rib 6 along the guide rail. Thereby, even if wheels 24a-24d do not contain a magnet, pushing devices 20 and 20a can be moved on back 3b of deck plate 3. 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 conveyance device. Then, the pressing devices 20 and 20a may be moved in the longitudinal direction of the trough rib 6 by the carrying device.

  According to the present invention, in a steel floor slab, it is possible to prevent fatigue crack initiation and fatigue crack growth at the root portion of a weld bead that joins a trough rib and a deck plate while preventing deformation of the deck plate. Therefore, the present invention can be suitably used to prevent fatigue cracking of steel floor slabs that constitute bridges and the like.

1 Bridge 2 Steel floor version 3 Deck plate 4 Main girder 5 Horizontal rib 6 Trough rib (vertical rib)
Reference Signs List 7 pavement material 8 automobile 9 joint portion 10 weld bead 11 non-welding portion 12, 13 toe 14 root portion 15 work platform 16, 18, 40 pressing member 20, 20a inner surface pressing device 22 main body portion 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 fatigue cracking of a steel floor slab having a configuration in which tips of side walls of a pair of trough ribs are welded to the back surface of a deck plate,
Applying a pressure from the inside of the trough rib to the pair of side walls so that the pair of side walls deform toward the outside of the trough rib;
And C. removing the pressure applied to the pair of side walls in the loading step.   The method for preventing fatigue cracking of a steel floor slab according to claim 1, wherein in the loading step, the pair of side wall portions are pressed outward by the curved surface portions of the pair of pressing members each having a curved surface portion. In the cross section perpendicular to the length direction of the trough rib, 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 and the unloading In a case where a distance in a 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 in the thickness direction of the deck plate from the back surface is made a value in the range of 0.01 to 3 mm by performing the loading step and the unloading step. The fatigue crack generation | occurrence | production prevention method of the steel floor slab of description.   The method for preventing fatigue cracking of a steel floor slab according to claim 3, wherein the loading step and the unloading step are repeated until the residual displacement amount reaches a value in the range of 0.01 to 3 mm.   The method according to claim 3 or 4, wherein the distance d1 is 1.5 times or more the thickness of the side wall portion.   The method for preventing fatigue cracking of a steel floor slab according to claim 3 or 4, wherein the distance d1 is equal to or less than seven times the thickness of the side wall portion. An inner surface pressing device disposed and used inside the trough rib to carry out the method for preventing fatigue cracking according to any one of claims 1 to 6,
Body part,
A support portion for supporting the main body portion so that the main body portion can move in the longitudinal direction of the trough rib;
A pair of pressing members movably supported by the main body with respect to the main body;
And a drive mechanism for moving 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 that detects the movement amount of the pressing member;
A load detection unit that detects a load applied to the pressing member;
The distance between the position of the side wall before the loading step and the position of the side wall after the unloading step based on the moving amount detected by the moving amount detector and the load detected by the load detector The inner surface pressing device according to claim 7, further comprising: a distance detection unit that detects

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