JP2016205024A - Steel floor slab - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steel floor slab, for facilitating manufacture by using a raw material in the same as usual, and improving fatigue strength in a welding route part formed in a welding place between a deck plate and a closed cross-sectional rib.SOLUTION: A steel floor slab 1 of applying the present invention comprises a deck plate 2 for applying a live load by extending in the bridge axial direction and formed in a substantially plate shape, a closed cross-sectional rib 3 welded to the reverse surface side B of the deck plate 2 and extending in the bridge axial direction and a groove part 5 formed on the reverse surface side B of the deck plate 2. The closed cross-sectional rib 3 comprises a closed space 30 formed in a closed cross-sectional shape in the bridge axial orthogonal direction X, an edge part 31 installed on the reverse surface side B of the deck plate 2 by melting welding metal 6 and a welding route part 61 formed on the closed space 30 side in a boundary between a reverse surface 2a of the deck plate 2 and the welding metal 6.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a steel floor slab that extends in the direction of the bridge axis and is loaded with a loading load.

  2. Description of the Related Art Conventionally, a steel deck for bridges in which a deck plate is reinforced with a closed cross-section rib generally has a structure in which the end of the closed cross-section rib is joined to a deck plate having a flat surface by welding. Steel decks for bridges are composed of deck plates with paving on the upper surface and vertical and horizontal ribs that stiffen the lower surface. Manufacturing at a low cost is possible.

  Here, the steel slab for bridges has a large ratio of traffic load to the total load capacity required, and fatigue damage due to repeated traffic load is likely to occur. Fatigue cracks that occur at the weld route formed at the joints are not only large in number, but can cause a sinking of the deck plate and immediately have a significant impact on traffic. It is necessary to establish countermeasure technology.

  For this reason, the steel slab disclosed in Patent Document 1 attempts to extend the fatigue life by bending the end of the closed cross-section rib to reduce the stress amplitude generated in the weld root. It is. In addition, the steel slab disclosed in Patent Document 2 is welded to the deck plate because the stress amplitude generated in the welding root portion is increased particularly at the member intersection where the closed cross-section rib is inserted into the lateral rib. By adding a rib in the closed cross-section rib in a direction parallel to the closed cross-section rib, it is intended to reduce the stress amplitude at the member intersection and suppress the occurrence of fatigue cracks from the weld root. .

JP 2013-87432 A JP 2014-92000 A

  However, the steel floor slab disclosed in Patent Document 1 is welded to the bent portion when bending is performed so that the end of the closed cross-section rib faces the inside of the closed cross-section rib. On the other hand, when bending is performed so that the end of the closed cross-section rib faces the outside of the closed cross-section rib, the structure of the member intersection where the closed cross-section rib is inserted into the lateral rib is complicated Therefore, the manufacturability may be reduced.

  Moreover, the steel floor slab disclosed in Patent Document 2 is not only an existing deck plate, vertical ribs and horizontal ribs, but is further attached with additional ribs, thereby increasing the overall weight. Not only is the lightness, which is one of the advantages of steel decks, lost, but the end of the welded part between the adjunct and the deck plate has become a detail that tends to cause fatigue damage. The starting point is also a concern.

  Therefore, the present invention has been devised in view of the above-described problems, and the object of the present invention is to facilitate manufacture by using the same material as the conventional one and to add a new welded portion. Another object of the present invention is to provide a steel slab with improved fatigue strength at the weld root formed at the welded portion between the deck plate and the closed cross-section rib without increasing the weight.

  The steel slab according to the first invention is a steel slab that extends in the direction of the bridge axis and is loaded with a loading load, and is welded to the deck plate formed in a substantially plate shape and the back side of the deck plate. A closed cross-section rib extending in the bridge axis direction, and a groove formed on the back side of the deck plate, the closed cross-section rib is formed in a closed space formed in a closed cross-sectional shape in the direction orthogonal to the bridge axis, and weld metal An edge portion attached to the back surface side of the deck plate by melting, and a welding root portion formed on the closed space side at the boundary between the back surface of the deck plate and the weld metal, and the groove portion, The deck plate has a predetermined remaining thickness at the groove bottom on the surface side of the deck plate, and is formed along the bridge axis direction at a predetermined separation distance from the welding root portion to the closed space side. And

  A steel deck according to a second invention is the steel plate according to the first invention, wherein the deck plate has a transverse rib that intersects the closed cross-section rib and extends in a direction perpendicular to the bridge axis, and is fixed to the back side of the deck plate by welding. A fixed surface with a predetermined fixed width in the bridge axis direction is formed by a leg length of the weld metal provided on both sides of the horizontal rib in the bridge axis direction and an end surface of the horizontal rib facing the back surface of the deck plate. The groove portion is formed in the bridge axis direction at a position spaced apart on both sides in the bridge axis direction from a virtual reference line that extends to the closed space in a direction orthogonal to the bridge axis in the bridge axis direction. Each of the extending both ends is arranged.

  A steel deck according to a third invention is characterized in that, in the second invention, each of the both end portions is arranged in a range of 10 mm or more and 250 mm or less in the bridge axis direction from the virtual reference line. To do.

  In the steel deck according to the fourth invention, in the second invention or the third invention, the groove portion extends over the virtual reference line in the bridge axis direction and extends in the bridge axis direction with a predetermined extension length. It is characterized by being formed.

  A steel deck according to a fifth aspect of the present invention is the steel plate according to any one of the first to fourth aspects, wherein the groove is a cross-section in a direction perpendicular to the bridge axis at a welding point where the edge is attached to the back side of the deck plate. Then, the tangent line from the welding root portion toward the inner surface of the groove bottom inside the groove portion has an inclination angle θ with respect to the back surface of the deck plate of 30 ° or more, and the remaining thickness of the groove bottom is 8 mm. It is formed so that it may become the above.

  A steel deck according to a sixth aspect of the present invention is the cross-section in the direction orthogonal to the bridge axis at the welding location where the end edge is attached to the back side of the deck plate. The inner surface of the groove bottom inside the groove is formed in a substantially semicircular arc shape, and the radius of curvature r of the inner surface of the groove bottom satisfies the relationship defined by the following equation (1). Features. Here, r is the radius of curvature of the inner surface of the groove bottom, and td is the thickness of the deck plate.

  According to the first to sixth inventions, the groove portion is formed by easy processing on the back surface side of the deck plate away from the welding root portion, and when a bending external force acts on the deck plate. Although tensile stress is generated on the surface side of the deck plate, the flow of compressive stress on the back side of the deck plate is blocked by the groove, and a low stress region is formed on the side of the groove, By avoiding stress concentration in the vicinity of the welding root portion on the back surface, it is possible to prevent a fatigue crack starting from the welding root portion from occurring on the back surface side of the deck plate.

  According to the second aspect of the present invention, in the place where the closed cross-section rib and the transverse rib intersect each other, a significantly large bending external force acts on the deck plate, but the compressive stress is generated in the groove formed on the back surface side of the deck plate. By interrupting the flow, it is possible to improve the fatigue strength of the weld root without adding new welds or increase the weight, and to reliably prevent the occurrence of fatigue cracks on the back side of the deck plate. It becomes possible.

  According to the third aspect of the invention, by arranging both ends of the groove in the range of 10 mm or more and 250 mm or less in the bridge axis direction from the virtual reference line, the extending length of the groove becomes 20 mm or more and 500 mm or less, and the cross section of the deck plate It is possible to sufficiently reduce the stress generated at the welding root without worrying about a decrease in rigidity.

  According to the fourth aspect of the present invention, the groove is continuously formed across the virtual reference line in the bridge axis direction, so that the back surface of the deck plate and the end surface of the lateral rib are in a range constrained by the fixed surface. Thus, the compressive stress blocked by the groove does not flow, and it is possible to reliably prevent the occurrence of fatigue cracks on the back surface side of the deck plate.

  According to the fifth invention, the tangent line from the welding root portion toward the inner surface of the groove bottom is formed so that the inclination angle with respect to the back surface of the deck plate is 30 ° or more and the remaining thickness of the groove bottom is 8 mm or more. By doing so, it is possible to ensure the necessary remaining plate thickness while sufficiently reducing the generated stress at the welding root portion.

  According to the sixth aspect of the invention, the radius of curvature of the inner surface of the groove bottom satisfies the relationship defined by the above equation (1), so that the tangential inclination angle is whatever the size of the inner surface of the groove bottom. It is possible to stabilize the effect of suppressing stress concentration.

It is a perspective view which shows the bridge in which the steel deck slab to which this invention is applied is introduced. (A) is a front view which shows the steel deck to which this invention is applied, (b) is the side view. (A) is a front view which shows the closed cross-sectional rib of a substantially semicircular cross section with the steel deck which applied this invention, (b) is a front view which shows the closed cross-section rib of a substantially V-shaped cross section. It is an enlarged front view which shows the welding route part of the steel deck to which this invention is applied. It is an enlarged front view which shows the modification of the welding route part of the steel deck to which this invention is applied. It is an enlarged front view which shows the aspect of the groove part of the steel deck which applied this invention. It is an enlarged plan view which shows the aspect of the groove part of the steel deck which applied this invention. (A) is an enlarged front view which shows the fatigue crack which generate | occur | produces in the conventional deck plate, (b) is an enlarged front view which shows the low stress area | region or no-stress area | region of the steel deck which applied this invention. . (A) is an enlarged front view which shows the location where a closed cross-section rib and a horizontal rib do not cross | intersect with the steel deck which applied this invention, (b) is a location where a closed cross-section rib and a horizontal rib cross. It is an enlarged front view shown. (A) is a top view which shows the finite element analysis model of the steel deck to which this invention is applied, (b) is the front view. It is a graph which shows the relationship between the generating stress in the welding root part of the steel deck to which this invention is applied, the residual plate | board thickness of a groove bottom, and the inclination angle of a tangent. It is a graph which shows the relationship between the generated stress of the steel deck to which this invention is applied, and the extending | stretching length of a groove part. (A) is a graph which shows the relationship between a stress concentration factor and r / td in the steel slab to which this invention is applied, (b) shows the relationship between the rate of change of a stress concentration factor and r / td. It is a graph. It is a front view which shows the horizontal rib in which the scallop was formed with the steel deck which applied this invention. It is an enlarged plan view which shows the horizontal rib in which the scallop was formed with the steel deck which applied this invention. (A) is a front view which shows the diaphragm extended in a bridge axis orthogonal direction by the steel deck to which this invention is applied, (b) is a front view which shows the bracket extended in a bridge axis orthogonal direction.

  Hereinafter, the form for implementing the steel deck 1 to which this invention is applied is demonstrated in detail, referring drawings.

  As shown in FIG. 1, a steel deck 1 to which the present invention is applied is used as a deck of a bridge 8 or the like and is loaded with a traffic load such as a railway wheel or a vehicle tire 80 as a load. is there.

  A steel floor slab 1 to which the present invention is applied includes a deck plate 2 in which a steel plate or the like formed in a substantially plate shape is used, a closed cross-section rib 3 such as a U rib attached to the back surface B of the deck plate 2, and a deck plate 2 and a groove portion 5 formed on the back surface side B of the back surface.

  The deck plate 2 is attached along the back surface 2a of the deck plate 2 with, for example, a plurality of closed cross-section ribs 3 arranged in the bridge axis orthogonal direction X. The deck plate 2 is provided with a pavement 81 or the like above the height direction Y along the surface 2b of the deck plate 2 as necessary.

  The deck plate 2 has a back surface 2a and a front surface 2b formed in a substantially flat shape, one or a plurality of closed cross-section ribs 3 extending in the bridge axis direction Z, and extending in the bridge axis orthogonal direction X crossing the closed cross-section ribs 3. One or a plurality of lateral ribs 4 are fixed to the back surface side B of the deck plate 2 by welding.

  As shown in FIG. 2, the deck plate 2 has a plate thickness td of about 10 mm to 20 mm in the height direction Y, and the closed cross-section rib 3 has a plate thickness tl of about 6 mm to 15 mm and the lateral rib 4 Is a plate thickness tb of about 9 mm to 19 mm in the bridge axis direction Z.

  As shown in FIG. 2A, the closed cross-section rib 3 is formed in a substantially U-shaped cross section by bending a steel plate or the like. The closed cross-section rib 3 may be formed in a substantially arc shape such as a substantially semicircular cross section as shown in FIG. 3A, and the cross section substantially V as shown in FIG. It may be formed in a shape or the like, and may be a combination of another cross-sectional shape with a substantially U-shaped cross-section, a substantially arc-shaped shape, a substantially V-shaped shape, or the like.

  The closed cross-section rib 3 is provided to reinforce the deck plate 2 and, as shown in FIG. 2A, extends substantially parallel to the back surface 2a of the deck plate 2 and is formed in a substantially flat shape. 35 and a pair of U-rib webs 36 extending upward from both side ends of the U-rib flange 35 in the bridge axis orthogonal direction X.

  The closed cross-section rib 3 has a closed space 30 formed in a closed cross-sectional shape in the bridge axis orthogonal direction X, and an end edge portion 31 attached to the back surface side B of the deck plate 2. The closed cross-section rib 3 is surrounded by a U rib flange 35 and a pair of U rib webs 36 to form a closed space 30, and the upper end in the height direction Y of the U rib web 36 is welded to the back surface 2 a of the deck plate 2. It becomes the edge part 31 to be done.

  As shown in FIG. 4, the closed cross-section rib 3 is one in which the edge 31 is attached to the back surface side B of the deck plate 2 by melting the weld metal 6, and the back surface 2 a of the deck plate 2 and the weld metal 6. And a welding route portion 61 formed on the closed space 30 side.

  The closed cross-section rib 3 is a cross-section in the bridge axis orthogonal direction X at the welding location where the edge 31 is attached to the back surface side B of the deck plate 2, and there are two intersections between the back surface 2 a of the deck plate 2 and the weld metal 6. Of the two intersections, the intersection on the closed space 30 side becomes the welding root portion 61, and the intersection on the horizontal rib 4 side among the two intersections becomes the welding toe portion 62.

  The welding route portion 61 is such that the weld metal 6 is sufficiently integrated with the back surface 2 a of the deck plate 2 and the end edge portion 31 of the closed cross-section rib 3 so that the weld metal 6 is not provided to the inside of the closed space 30. Thus, it is formed at the boundary between the inner side and the outer side of the closed space 30 above the edge 31 of the closed cross-section rib 3.

  As shown in FIG. 5A, the welding route portion 61 is a closed space 30 when the weld metal 6 is not sufficiently integrated with the back surface 2 a of the deck plate 2 or the end edge portion 31 of the closed cross-section rib 3. Formed on the outside. As shown in FIG. 5B, the welding route portion 61 is formed inside the closed space 30 when the weld metal 6 is provided from the outside to the inside of the closed space 30.

  The weld toe portion 62 can be subjected to a welding point improvement process such as a grinder process or an ultrasonic impact process (UIT). Here, the ultrasonic impact treatment (UIT) applies a pin attached to the tip of the ultrasonic impact treatment device to the weld toe 62 and applies an impact caused by ultrasonic vibration to the weld toe 62 from the pin. Thereby, the welding residual stress of the weld toe portion 62 is changed from tension to compression, and the metal structure of the weld metal 6 at the welded portion is improved.

  As shown in FIG. 2B, the lateral rib 4 is made of, for example, a steel plate having a predetermined thickness tb. The lateral rib 4 is notched along the U rib flange 35 and the U rib web 36 of the closed cross-section rib 3 to form a notch 40, and the closed cross-section rib 3 is fitted into the notch 40 so that the closed cross-section rib 3 will be crossed.

  When the horizontal rib 4 is fixed to the back surface side B of the deck plate 2 by welding, an end surface 41 facing the back surface 2a of the deck plate 2 is arranged upward in the height direction Y. The lateral rib 4 has a fixed surface with a predetermined fixed width E in the bridge axis direction Z by bringing the end surface 41 into contact with or away from the back surface 2a of the deck plate 2 and fixing the end surface 41 to the back surface 2a of the deck plate 2. 7 is formed.

  Since the lateral rib 4 is fixed to the back surface side B of the deck plate 2 by welding, the leg length J of the weld metal 6 provided on both sides in the bridge axis direction Z and the plate thickness tb of the end surface 41 of the lateral rib 4 are: It becomes the fixed width E (E = tb + 2 × J) of the fixed surface 7. When the lateral rib 4 is mechanically joined to the back surface 2 a of the deck plate 2, the length in which the deck plate 2 is restrained in the bridge axis direction Z by mechanical joining is the fixed width E of the fixed surface 7. .

  As shown in FIG. 6, the groove portion 5 is formed in a concave shape from the back surface 2 a of the deck plate 2 upward in the height direction Y by cutting out the back surface side B of the deck plate 2. The groove portion 5 has a predetermined remaining plate thickness ta at the groove bottom 50 on the surface side A of the deck plate 2 and is formed without penetrating from the back surface side B to the surface side A of the deck plate 2.

  The groove part 5 is separated from the welding root part 61 on the closed space 30 side of the closed cross-section rib 3 by a predetermined separation distance d in the bridge axis orthogonal direction X, and a groove side surface 51 is formed inside the groove part 5. The groove part 5 has a predetermined height dimension h in the height direction Y from the deepest part 50a of the groove bottom 50 having the remaining plate thickness ta to the back surface 2a of the deck plate 2.

  The groove portion 5 is a cross section in the bridge axis orthogonal direction X at the welding point where the end edge portion 31 of the closed cross-section rib 3 is attached to the back surface side B of the deck plate 2, and the inner surface of the groove bottom 50 on the surface side A of the deck plate 2. However, it has a predetermined radius of curvature r inside the groove portion 5 and is formed in a substantially semicircular inner surface shape. The groove part 5 is not limited to this, and the groove bottom 50 may be formed in any inner shape inside the groove part 5.

  For example, the tangent line C from the welding root portion 61 to the inner surface of the groove bottom 50 on the inner side of the groove portion 5 has an inclination angle θ with respect to the back surface 2a of the deck plate 2 of 30 ° or more. The remaining plate thickness ta is 8 mm or more.

  The groove portion 5 has an inner surface of the groove bottom 50 formed inside the groove portion 5 in a substantially semicircular arc shape, and a curvature radius r of the inner surface of the groove bottom 50 satisfies a relationship defined by the following expression (1). It will be a thing. Here, r is the radius of curvature of the inner surface of the groove bottom 50, and td is the thickness of the deck plate 2.

  As shown in FIG. 7, the groove portion 5 is formed along the bridge axis direction Z at a predetermined distance d in the bridge axis orthogonal direction X from the welding root portion 61, and has both end portions in the bridge axis direction Z. It extends with a predetermined stretch length L up to 52. The groove 5 is formed in a substantially oval shape in the planar direction, but may be formed in a substantially rectangular shape, a substantially elliptical shape, or the like.

  When the groove portion 5 is a virtual reference line H obtained by extending the central axis G in the bridge axis direction Z of the fixed surface 7 of the lateral rib 4 to the closed space 30 of the closed cross-section rib 3 in the bridge axis orthogonal direction X, Each of the both end portions 52 extending in the bridge axis direction Z is disposed at positions spaced from the virtual reference line H on both sides in the bridge axis direction Z.

  For example, when the leg length J of the weld metal 6 provided on both sides of the lateral rib 4 in the bridge axis direction Z is 6 mm and the plate thickness tb of the end surface 41 of the lateral rib 4 is 9 mm, the groove 5 has a fixed width of the fixed surface 7. E is 21 mm, and each of the end portions 52 is arranged in the range of 10 mm or more and 250 mm or less in the bridge axis direction Z from the virtual reference line H.

  The groove 5 extends continuously in the bridge axis direction Z across the virtual reference line H in the bridge axis direction Z, and is formed at both ends 52 at positions 10 mm from the virtual reference line H in the bridge axis direction Z. When the both ends 52 are arranged at a position 250 mm from the virtual reference line H in the bridge axis direction Z, the extension length L in the bridge axis direction Z is 500 mm. (20 mm ≦ L ≦ 500 mm).

  Note that the groove 5 is not limited to the continuous extension extending in the bridge axis direction Z across the virtual reference line H, and is not less than 10 mm and not more than 250 mm in the bridge axis direction Z from the virtual reference line H. Each of the end portions 52 may be disposed in the range, and may be formed intermittently in the bridge axis direction Z without straddling the virtual reference line H.

  As shown in FIG. 8, the bridge 8 is loaded with a traffic load due to the tires 80 of the vehicle. In particular, the loaded load of the tires 80 is loaded from above the closed space 30 of the closed cross-section rib 3. In this case, the deck plate 2 disposed above the closed space 30 of the closed cross-section rib 3 tends to bend and deform from the upper side in the height direction Y toward the lower side.

  At this time, as shown in FIG. 8 (a), the conventional deck plate 9 is directed from the upper side to the lower side when attempting to curve and deform from the upper side in the height direction Y to the lower side due to the load of the tire 80. When the bending external force M acts, a tensile stress T is generated on the front surface side A of the deck plate 9 and a compressive stress P is generated on the rear surface side B of the deck plate 9.

  In the conventional deck plate 9, the compressive stress P is concentrated on the back surface 9 a of the deck plate 9 on which the welding root portion 91 and the weld toe portion 92 are formed by generating the compressive stress P on the back surface side B of the deck plate 9. The fatigue crack F occurs on the back surface 9a of the deck plate 9 starting from the welding root portion 91 and the weld toe portion 92.

  The weld toe portion 92 is exposed on the back surface side B of the deck plate 9, and the weld toe portion 92 is set as a starting point by performing a welding point improvement process such as a grinder process or an ultrasonic impact process (UIT). The occurrence of fatigue cracks F can be suppressed. On the other hand, since the welding route portion 91 is formed on the closed space 90 side and is not exposed, it is impossible to perform a welding point improvement process such as an ultrasonic impact process (UIT).

  For this reason, the conventional deck plate 9 cannot be subjected to welding point improvement processing such as ultrasonic impact processing (UIT) on the welding route portion 91, and compressive stress P is generated on the back side B of the deck plate 9. In particular, the fatigue crack F may occur on the back surface 9 a of the deck plate 9 starting from the welding root portion 91.

  On the other hand, as shown in FIG. 8 (b), the steel slab 1 to which the present invention is applied is separated from the welding root portion 61 to the closed space 30 side on the back surface side B of the deck plate 2, and the groove portion 5 is provided. When a bending external force M acts on the deck plate 2 on the closed space 30 side, a tensile stress T is generated on the surface side A of the deck plate 2, but on the back surface side B of the deck plate 2. The flow of the compressive stress P is blocked by the groove 5.

  In the steel slab 1 to which the present invention is applied, the flow of the compressive stress P on the back surface side B of the deck plate 2 is blocked by the groove 5, so that the compressive stress P is separated upward from the back surface 2 a of the deck plate 2. Thus, a low-stress region or a no-stress region R is formed on the welding route part 61 side of the groove part 5 in the bridge axis orthogonal direction X.

  Thereby, since the low-stress area | region or the no-stress area | region R is formed in the welding root part 61 side of the groove part 5 in the steel deck 1 to which this invention is applied, it is the vicinity of the welding root part 61 by the back surface 2a of the deck plate 2. Thus, it is possible to prevent the stress cracking at the back surface side B of the deck plate 2 from occurring at the back surface side B of the deck plate 2.

  The steel floor slab 1 to which the present invention is applied is easy to manufacture by using the same material as the conventional one, and without adding a new weld or increasing the weight, the deck plate 2 and the closed cross-section rib 3 It is possible to improve the fatigue strength at the weld root portion 61 formed at the weld location.

  As shown in FIG. 9A, the steel deck 1 to which the present invention is applied has a bending external force M applied to the deck plate 2 on the closed space 30 side even at a location where the closed cross-section rib 3 and the lateral rib 4 do not intersect. Therefore, it is possible to prevent the occurrence of fatigue cracks F on the back surface side B of the deck plate 2 by blocking the flow of the compressive stress P on the back surface side B of the deck plate 2 by the groove portion 5. .

  The steel floor slab 1 to which the present invention is applied, particularly, as shown in FIG. 9 (b), the back surface 2a of the deck plate 2 and the lateral rib 4 are formed at a location where the closed cross-section rib 3 and the lateral rib 4 intersect each other. Since the end surface 41 is constrained by the fixed surface 7, the bending external force M acting on the deck plate 2 on the closed space 30 side is remarkably large as compared with the portion where the closed cross-section rib 3 and the lateral rib 4 do not intersect. Become.

  As a result, the steel slab 1 to which the present invention is applied is particularly suitable for the deck plate 2 in spite of the large bending external force M acting on the deck plate 2 where the closed cross-section rib 3 and the lateral rib 4 intersect each other. The flow of the compressive stress P is blocked by the groove portion 5 formed on the rear surface side B of the steel plate 2 so that the fatigue strength at the weld route portion 61 formed at the welded portion between the deck plate 2 and the closed cross-section rib 3 is ensured. Can be improved.

  In the steel slab 1 to which the present invention is applied, the separation distance d separated from the welding root portion 61 toward the closed space 30 is, for example, about 2 mm or more and 50 mm or less. The steel floor slab 1 to which the present invention is applied can absorb a construction error when the edge 31 of the closed cross-section rib 3 is attached to the back surface 2a of the deck plate 2 by securing a separation distance d of 2 mm or more. In addition, by setting the separation distance d to 50 mm or less, stress concentration in the vicinity of the welding root portion 61 can be surely avoided.

  A tangent line C from the welding root portion 61 toward the inner surface of the groove bottom 50 inside the groove portion 5 has a predetermined inclination angle θ with respect to the back surface 2a of the deck plate 2, as shown in FIG. In order to obtain the optimum inclination angle θ of the tangent line C, as shown in FIG.

  In FIG. 10, for a model in which a part of the steel slab 1 to which the present invention is applied is cut, the closed cross-section rib 3 and the lateral rib 4 are crossed from above the closed space 30 of the closed cross-section rib 3. The loading load to be applied is 50 kN, the inclination angle θ of the tangent line C is changed from 0 ° to 75 °, the separation distance d of the groove 5 is 3 mm, the thickness td of the deck plate 2 is 16 mm, the plate of the closed cross-section rib 3 The thickness tl is 6 mm, the plate thickness tb of the lateral rib 4 is 9 mm, the leg length J of the welded portion of the lateral rib 4 is 6 mm, the curvature radius r of the inner surface of the groove bottom 50 is 3.2 mm, and the extending length L of the groove portion 5 is 500 mm. did.

  In FIG. 11, the result of the analytical study by FEA shows that the left vertical axis is the stress generated in the welding root portion 61, the right vertical axis is the remaining thickness ta of the groove bottom 50, and the horizontal axis is the inclination angle θ. Indicated. In the steel deck 1 to which the present invention is applied, as shown in FIG. 11, when the inclination angle θ of the tangent line C is 30 ° or more, the generated stress in the weld root portion 61 is sufficiently reduced. I understand.

  Further, in the model shown in FIG. 10, when the inclination angle θ of the tangent line C exceeds 60 °, it can be seen that the remaining plate thickness ta of the groove bottom 50 is less than 8 mm, and the minimum member thickness specified in the road bridge specifications. It does not meet the conditions of. For this reason, in the steel slab 1 to which the present invention is applied, it is desirable to set the inclination angle θ of the tangent line C so that the remaining plate thickness ta of the groove bottom 50 is 8 mm or more.

  Thereby, the steel slab 1 to which the present invention is applied is such that the tangent C from the welding root portion 61 to the inner surface of the groove bottom 50 has an inclination angle θ with respect to the back surface 2a of the deck plate 2 of 30 ° or more and the groove By forming the remaining plate thickness ta of the bottom 50 to be 8 mm or more, it is possible to secure the necessary remaining plate thickness ta while sufficiently reducing the generated stress in the welding route portion 61.

  As shown in FIG. 7, the extension length L of the groove portion 5 extends across the virtual reference line H in the bridge axis direction Z, extends in the bridge axis direction Z, and is continuous with the groove portion 5. In order to obtain a proper stretching length L, an analytical study was performed by FEA using the model shown in FIG. 10 with the inclination angle θ of the tangent line C being 45 ° and the stretching length L of the groove 5 being changed from 0 mm to 500 mm. .

  Here, as shown in FIG. 8B, the compressive stress P blocked by the groove 5 acts on the groove bottom 50. At this time, the remaining thickness ta of the groove bottom 50 is the thickness of the deck plate 2. By being smaller than td and the groove bottom 50 being a shape suddenly changing portion, excessive stress is generated on the inner surface of the groove bottom 50, and the groove bottom 50 is prevented from being damaged from the inner surface of the groove bottom 50. Therefore, the stress generated on the inner surface of the groove bottom 50 having a predetermined remaining plate thickness ta is also subjected to analytical examination by FEA in addition to the stress generated in the welding root portion 61.

  In FIG. 12, the result of the analytical examination by FEA is shown as the generated stress on the inner surface of the groove bottom 50 and the generated stress in the welding root portion 61, and the horizontal axis as the extension length L of the groove portion 5. .

  As shown in FIG. 12, the steel deck 1 to which the present invention is applied has a tendency that the stress generated on the inner surface of the groove bottom 50 gradually increases as the extension length L of the groove 5 increases. It can be seen that when the stretching length L is 20 mm or more, the generated stress at the weld root portion 61 is sufficiently reduced as compared with the gradual increase tendency of the generated stress at the inner surface of the groove bottom 50.

  In the steel slab 1 to which the present invention is applied, the stress generated in the weld root portion 61 is most reduced particularly in the range in which the extension length L of the groove portion 5 is 40 mm or more and 100 mm or less. In the steel deck 1 to which the present invention is applied, when the extending length L of the groove portion 5 exceeds 500 mm, the processing cost for cutting the groove portion 5 on the back surface 2a of the deck plate 2 increases, and the deck plate 2 Therefore, it is desirable that the extension length L of the groove 5 is 500 mm or less.

  Thereby, as shown in FIG. 7, as for the steel deck 1 to which this invention is applied, the both ends 52 of the groove part 5 are arrange | positioned in the range of 10 mm or more and 250 mm or less in the bridge axial direction Z from the virtual reference line H. Thus, the extending length L of the groove portion 5 is 20 mm or more and 500 mm or less, and it is possible to sufficiently reduce the generated stress in the welding root portion 61 without worrying about a decrease in the cross-sectional rigidity of the deck plate 2 or the like. .

  In the steel slab 1 to which the present invention is applied, the groove portion 5 is continuously formed across the virtual reference line H in the bridge axis direction Z, particularly at a location where the closed cross-section rib 3 and the lateral rib 4 intersect each other. As a result, the compressive stress P blocked by the groove portion 5 does not flow within a range in which the back surface 2a of the deck plate 2 and the end surface 41 of the lateral rib 4 are restrained by the fixed surface 7 and the bending external force M increases. In addition, the fatigue strength at the weld route portion 61 can be reliably improved at the welded portion between the deck plate 2 and the closed cross-section rib 3.

  The generated stress on the inner surface of the groove bottom 50 is because the compressive stress P blocked by the groove portion 5 on the back surface side B of the deck plate 2 concentrates on the inner surface of the groove bottom 50 as shown in FIG. In order to avoid damage to the groove bottom 50 from the inner surface of the groove bottom 50, the optimum radius of curvature r of the inner surface of the groove bottom 50 is obtained by the following equations (2) to (8).

  Here, the deck plate 2 is regarded as a two-dimensional fixed beam at both ends, a redistribution of moments resulting in an increase in stress due to a decrease in the remaining plate thickness ta of the groove bottom 50 and a decrease in rigidity due to a decrease in the remaining plate thickness ta. Considering the stress concentration on the inner surface of the groove bottom 50 formed in FIG. 13, the result of the study of calculating the ratio of the generated stress (stress concentration coefficient K) on the inner surface of the groove bottom 50 compared to the case where the groove portion 5 is not formed is shown in FIG. Shown in

  Here, K: a value obtained by dividing the stress generated on the inner surface of the groove bottom 50 when the groove portion 5 is formed by dividing the stress generated on the inner surface of the groove bottom 50 when the groove portion 5 is not formed (stress concentration) Coefficient), Kt: stress concentration factor considering the increase in stress due to a decrease in the remaining plate thickness ta, Km: stress concentration factor considering the redistribution of moments that cause local rigidity reduction of the groove 5, and α: a substantially semicircular arc shape. Stress concentration factor when bending a notched round bar, r: radius of curvature of inner surface of groove bottom 50, ta: remaining thickness of groove bottom 50, td: thickness of deck plate 2, W : The width of the closed cross-section rib 3 in the direction orthogonal to the bridge axis X, h: the height of the groove 5, and ν: the Poisson's ratio (≈0.3) of the steel material.

  In FIG. 13 (a), the vertical axis represents the stress concentration factor K and the horizontal axis represents r / td. In FIG. 13B, at each r / td shown in FIG. 13A, the rate of change of the stress concentration factor K obtained by differentiating the stress concentration factor K is the vertical axis, and r / td is horizontal. Shown as axis. As shown in FIG. 13 (a), the steel deck 1 to which the present invention is applied has an inner surface of the groove bottom 50 as a predetermined radius of curvature r, and r / td is set to a predetermined size so that the stress is reduced. The concentration factor K is sufficiently small, and the stress concentration on the inner surface of the groove bottom 50 can be suppressed.

  As shown in FIG. 13B, the steel deck 1 to which the present invention is applied has a large rate of change of the stress concentration coefficient K, particularly when r / td is less than 0.15, and the groove bottom 50 Although the effect of suppressing stress concentration on the inner surface becomes unstable, when r / td is 0.15 or more, the inclination angle θ of the tangent line C is set to 30 ° and 45 °, whereby the upper limit of r / td Regardless of this, the rate of change of the stress concentration coefficient K becomes stable, and the effect of suppressing the stress concentration on the inner surface of the groove bottom 50 becomes stable.

  The steel slab 1 to which the present invention is applied has a large change rate of the stress concentration factor K when the inclination angle θ of the tangent line C is 60 ° and r / td exceeds 0.60. Therefore, r / td is set to 0.15 or more and 0.60 or less, and the radius of curvature r of the inner surface of the groove bottom 50 satisfies the relationship defined by the above formula (1). This makes it possible to stabilize the effect of suppressing the stress concentration on the inner surface of the groove bottom 50 regardless of the inclination angle θ of the tangent line C.

  As shown in FIG. 14, the steel deck 1 to which the present invention is applied has the horizontal ribs 4 at the joint portions of the end edge portion 31 of the closed cross-section rib 3, the deck plate 2, and the horizontal ribs 4. Even when the scallop 42 is formed by partially notching, the groove 5 can be formed on the back surface side B of the deck plate 2.

  At this time, in the steel slab 1 to which the present invention is applied, as shown in FIG. 15, the scallop 42 is formed on the lateral rib 4 so that the lateral rib 4 is separated from the edge 31 of the closed cross-section rib 3. The leg length J of the weld metal 6 provided on both sides of the bridge axis direction Z and the end face of the lateral rib 4 at a position separated from the end edge portion 31 of the closed cross-section rib 3 in the bridge axis orthogonal direction X The plate thickness tb of 41 is the fixed width E (E = tb + 2 × J) of the fixed surface 7.

  Note that the steel slab 1 to which the present invention is applied is not limited to the lateral rib 4 in which the notched portion 40 into which the closed cross-section rib 3 is fitted is formed, but the diaphragm 43 shown in FIG. 16A or FIG. Or the like may be provided so as to be fixed to the deck plate 2 by a fixing surface 7 that extends in the bridge axis orthogonal direction X on the side of the closed cross-section rib 3 and has a predetermined fixing width E.

  As mentioned above, although the example of embodiment of this invention was demonstrated in detail, all the embodiment mentioned above showed only the example of actualization in implementing this invention, and these are the technical aspects of this invention. The range should not be construed as limiting.

  For example, assuming that the steel deck 1 to which the present invention is applied is used as a steel deck 1 for a bridge that extends in the bridge axis direction Z and is loaded with a loading load, the depth direction of the deck plate 2 is bridged. As the axial direction Z, the width direction of the deck plate 2 is the orthogonal direction X of the bridge axis. However, the axial direction Z is not limited to that for the bridge, and may be applied to any application.

DESCRIPTION OF SYMBOLS 1: Steel deck 2: Deck plate 2a: Back surface 2b: Front surface 3: Closed cross-section rib 30: Closed space 31: End edge part 35: U rib flange 36: U rib web 4: Horizontal rib 40: Notch part 41: End surface 42 : Scallop 43: Diaphragm 44: Bracket 5: Groove 50: Groove bottom 50a: Deepest part 51: Groove side surface 52: Both ends 6: Weld metal 61: Weld root 62: Weld toe 7: Fixed surface 8: Bridge 80 : Vehicle 81: Pavement A: Front side B: Back side X: Bridge axis orthogonal direction Y: Height direction Z: Bridge axis direction

Claims (6)

A steel slab that extends in the direction of the bridge axis and is loaded with a load.
A deck plate formed in a substantially plate shape, a closed cross-section rib welded to the back surface side of the deck plate and extending in the bridge axis direction, and a groove formed on the back surface side of the deck plate,
The closed cross-section rib includes a closed space formed in a closed cross-sectional shape in a direction orthogonal to the bridge axis, an edge portion attached to the back side of the deck plate by melting a weld metal, and a weld to the back side of the deck plate. A welding route portion formed on the closed space side at the boundary with the metal,
The groove portion has a predetermined remaining plate thickness at the groove bottom on the surface side of the deck plate, and is formed along the bridge axis direction with a predetermined separation distance from the welding root portion to the closed space side. A steel floor slab characterized by In the deck plate, transverse ribs extending in a direction orthogonal to the bridge axis intersecting the closed cross-section ribs are fixed to the back side of the deck plate by welding, and provided on both sides of the transverse rib in the bridge axis direction. A fixed surface is formed with a predetermined fixed width in the bridge axis direction with the leg length of the weld metal to be formed and the end surface of the lateral rib facing the back surface of the deck plate,
The groove portion has a bridge axis direction center axis in the bridge axis direction extending from the virtual reference line extending to the closed space in a direction perpendicular to the bridge axis to positions spaced apart on both sides in the bridge axis direction. The steel slab according to claim 1, wherein each is arranged. 3. The steel deck according to claim 2, wherein each of the both end portions is arranged in a range of 10 mm or more and 250 mm or less in the bridge axis direction from the virtual reference line. 4. The steel slab according to claim 2, wherein the groove portion is formed continuously across the virtual reference line in the bridge axis direction and extending in the bridge axis direction with a predetermined extension length. . The groove is a cross-section in a direction perpendicular to the bridge axis at a welding point where the end edge is attached to the back side of the deck plate, and is tangent to the inner surface of the groove bottom from the welding root to the inside of the groove However, the inclination angle θ with respect to the back surface of the deck plate is set to 30 ° or more, and the remaining plate thickness of the groove bottom is set to 8 mm or more. Steel floor slab as described in the item. The groove is a cross-section in a direction perpendicular to the bridge axis at a welding point where the edge is attached to the back side of the deck plate, and the inner surface of the groove bottom inside the groove is formed in a substantially semicircular arc shape. The steel deck according to any one of claims 1 to 5, wherein a radius of curvature r of the inner surface of the groove bottom satisfies a relationship defined by the following equation (1).

Here, r is the radius of curvature of the inner surface of the groove bottom, and td is the thickness of the deck plate.

Images