Steel plate deck

Abstract

An object of the present invention is to solve the problems of the prior art, that is, to provide a steel plate deck in which a shape steel having a flange is used as a vertical rib and a sectional force of the vertical rib does not extremely change.SOLUTION: A steel floor slab of the present invention is a steel floor slab of a bridge, and includes a steel deck plate, a vertical rib, and a horizontal rib. The vertical rib is a shaped steel having a web plate and a flange provided at a lower end of the web plate. A flange notch is formed in the flange of the longitudinal rib. The flange notch portion is formed such that the outer edge in a plan view has a curved shape and the length of the flange is the shortest at the rib intersection portion. Then, after the flange at the rib intersection portion is accommodated in the web slit, the one side surface of the web and the lateral rib are welded and joined to each other.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to technology relating to steel decks for road bridges, and more specifically to steel decks that use flanged steel beams such as angle irons and CT steel beams as vertical ribs for open cross sections. [Background technology]

[0002] Steel decks are lighter than concrete decks and have shorter construction times, so they are widely used, especially for viaducts on urban expressways, bridges in coastal areas with soft ground, and long-span bridges. These steel decks are made of a steel deck plate and longitudinal and transverse ribs, and are welded together to form a thin plate assembly structure. The longitudinal and transverse ribs are components that stiffen the steel deck plate, with the longitudinal ribs being positioned so that their longitudinal direction is primarily in the bridge axis direction, and the transverse ribs being positioned so that their longitudinal direction is primarily perpendicular to the bridge axis.

[0003] Urban expressways, which are primarily comprised of viaducts, support large volumes of traffic every day. For example, the Hanshin Expressway has a cross-sectional traffic volume of nearly 100,000 vehicles per day, with a very high proportion of large vehicles. This means that road bridges on urban expressways are subjected to numerous wheel loads over many years, and it is easy to imagine that fatigue damage can occur in the steel decks that make up the road bridges.

[0004] There are two types of longitudinal ribs: closed cross-section ribs (U-ribs) and open cross-section ribs (flat plate ribs, valve plate ribs, etc.), and it is known that steel decks that use closed cross-section ribs are prone to fatigue cracks. In contrast, with open cross-section ribs, many cases of fatigue cracks were previously reported at rib intersections (where the longitudinal and horizontal ribs intersect), but as a result of revisions to the shape of the slits through which the longitudinal ribs pass (particularly the size of the scallop diameter), fatigue cracks at rib intersections are now almost unheard of.

[0005] Because open-section ribs, such as flat plate ribs and bulb plate ribs, are generally plate-shaped components, their individual moment of inertia is significantly smaller than that of closed-section ribs. Therefore, steel decks using open-section ribs require the installation of numerous vertical ribs, which tends to result in a greater total steel weight than steel decks using closed-section ribs. In addition, the number of weld lines is approximately twice that of closed-section ribs, and the painted area increases, making this undesirable from an economic standpoint.

[0006] Therefore, in order to reduce the impact of increasing the number of vertical ribs, the number of weld lines, and the painted area, one possible measure would be to reduce the overall steel weight by using open cross-section ribs that have higher rigidity (i.e., have a large moment of inertia) than flat plate ribs or bulb plate ribs and thereby reduce the number of horizontal ribs. For example, Patent Document 1 proposes a steel deck and a manufacturing method for a steel deck that uses open cross-section ribs with flanges as vertical ribs. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-280753 Summary of the Invention [Problem to be solved by the invention]

[0008] The technology disclosed in Patent Document 1 uses open section ribs with flanges as vertical ribs, which provides higher rigidity than conventional open section ribs, and therefore it is expected that the number of horizontal ribs installed on the steel deck can be reduced, which in turn will reduce costs. However, the following structural problems can be pointed out with this technology.

[0009] Typically, slits are formed in the horizontal ribs of steel decks, and vertical ribs are inserted into these slits at the rib intersections. In Patent Document 1, the vertical ribs have flanges, so to prevent these flanges from being inserted into the slits, the flanges are cut out (not provided) at the rib intersections. In other words, the vertical ribs of Patent Document 1 have portions with flanges and portions without, which results in discontinuities where the cross-sectional force changes drastically when viewed in the bridge axis direction. These discontinuities may cause stress concentrations, and are, of course, not structurally desirable.

[0010] The object of the present invention is to solve the problems associated with the prior art, namely, to provide a steel deck that utilizes flanged structural steel as vertical ribs and does not cause the cross-sectional forces of the vertical ribs to change drastically. [Means for solving the problem]

[0011] The present invention was made by focusing on the use of angle irons or CT steel beams as vertical ribs, forming flange notches at the rib intersections of the flanges of the vertical ribs, and forming the flange notches so that the outer edges have a curved shape when viewed in a plane, and is an invention based on an unprecedented idea.

[0012] The steel deck of the present invention is a steel deck for a bridge, and comprises a steel deck plate, longitudinal ribs, and transverse ribs. The longitudinal ribs are shaped steel beams having vertically arranged web plates and flanges attached to the lower ends of the web plates. At the rib intersections (where the vertical and transverse ribs intersect), "web plate slits" are formed for inserting the longitudinal ribs, and "flange notches" are formed in the flanges of the vertical ribs. These flange notches are formed so that the outer edges are curved in a plan view and so that the flange length at the rib intersection is minimized. The flange at the rib intersection is then accommodated in the web plate slit, and the transverse rib is welded to one surface of the web plate.

[0013] The steel deck of the present invention can also have a first groove-shaped space, a second groove-shaped space, and a lower space formed in the web plate slit. When a web plate with a longitudinal rib is placed in the web plate slit, the first groove-shaped space is formed on one side of the web plate, and the second groove-shaped space is formed on the other side of the web plate. The lower space is formed so that its outer edge is curved below the web plate. The web plate slit is a continuous space in which the first groove-shaped space, the lower space, and the second groove-shaped space are connected. The second groove-shaped space is formed so that the upper part of the transverse rib is open, and the first groove-shaped space is formed so that the upper part of the transverse rib is not open and has a curved outer edge at its upper end. Furthermore, a thin plate is formed between the first inner wall on the web plate side of the inner walls constituting the first groove-shaped space and the second inner wall on the web plate side of the inner walls constituting the second groove-shaped space. The web plate is then welded in contact with the second inner wall.

[0014] The steel deck of the present invention can also be configured so that the second channel space is wider toward the top. In this case, the second outer wall, which is different from the second inner wall among the inner walls that form the second channel space, is formed so as to be inclined relative to the web plate.

[0015] The steel deck of the present invention may also have a curved outer edge at the upper end of the second outer wall. [Effects of the Invention]

[0016] The steel deck of the present invention has the following advantages: (1) By using flanged steel beams such as angle steel and CT steel beams as vertical ribs, they have higher rigidity than open-section ribs such as flat plate ribs and valve plate ribs. Therefore, the number of horizontal ribs to be installed on the steel deck can be reduced compared to conventional technology, and as a result, the cost of the steel deck can be reduced. (2) Unlike Patent Document 1, the cross-sectional force of the vertical ribs does not change drastically, so the steel deck can be structurally relatively stable. (3) By devising the shape of the web plate slits, fatigue cracks occurring at the rib intersections can be further suppressed, and as a result, fatigue durability can be further improved. [Brief explanation of the drawings]

[0017] [Figure 1] (a) is a cross-sectional view showing a steel deck plate of the present invention in which the steel deck plate is stiffened by vertical ribs using angle irons, and (b) is a cross-sectional view showing a steel deck plate of the present invention in which the steel deck plate is stiffened by vertical ribs using CT steel beams. [Figure 2] (a) is a vertical cross-section showing the "rib intersection" of the steel deck, and (b) is a horizontal cross-section showing the "rib intersection" of the steel deck. [Figure 3] FIG. 10 is a horizontal cross-sectional view showing a flange cutout portion whose outer edge is formed as a semicircle with a relatively large diameter. [Figure 4] FIG. 10 is a cross-sectional view showing a web plate slit in which a "first groove-shaped space" and a "second groove-shaped space" are formed. [Figure 5] 10 is a cross-sectional view showing a web plate slit formed so that the second outer wall of the "second groove-shaped space" is inclined relative to the web plate. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0018] An example of an embodiment of the steel deck of the present invention will be described with reference to the drawings.

[0019] The steel deck of the present invention is a deck structure that includes a steel deck plate, vertical ribs, and horizontal ribs, and is supported by main girders and vertical beams. The vertical ribs that make up the steel deck are arranged in multiple rows with their longitudinal direction (axial direction) aligned with the bridge axis and spaced apart in a direction roughly perpendicular to the bridge axis. On the other hand, the horizontal ribs are arranged in multiple rows with their longitudinal direction (axial direction) aligned with the bridge axis and spaced apart in a direction roughly perpendicular to the bridge axis.

[0020] The longitudinal ribs and transverse ribs, which act as stiffeners, are welded to the underside of the steel deck plate. Therefore, when viewed in the bridge axis direction, the longitudinal ribs can be classified into "general sections" that do not intersect with the transverse ribs, and "rib intersection sections" that intersect with the transverse ribs. While longitudinal ribs are broadly classified into closed and open sections, the longitudinal ribs that make up the steel deck of this invention are open sections.

[0021] 1A and 1B are vertical cross-sectional views of the "general portion" of the steel deck 100 of the present invention, in which (a) shows the steel deck 100 in which the steel deck plate 400 is stiffened by longitudinal ribs 200 made of angle irons, and (b) shows the steel deck 100 in which the steel deck plate 400 is stiffened by longitudinal ribs 200 made of CT steel. As shown in this figure, the longitudinal ribs 200 that make up the steel deck 100 of the present invention are shaped steel having web plates 210 arranged in the vertical direction and flanges 220 provided at the lower ends of the web plates 210, and can be, for example, angle irons (particularly unequal leg angle irons) shown in FIG. 1A or CT (cut tee) steels shown in FIG. 1B.

[0022] The steel deck 100 of the present invention uses shaped steel with flanges 220, such as angle irons and CT steel beams, as the vertical ribs 200, and therefore has higher rigidity (particularly, moment of inertia) than open-section ribs such as flat plate ribs and bulb plate ribs. Therefore, the span between the vertical ribs can be made larger than in conventional technology, which reduces the number of transverse ribs 300 installed on the steel deck 100 and, as a result, reduces the cost of the steel deck 100. The height of the web plates 210 and the overhang length of the flanges 220 that make up the vertical ribs 200, as well as the height of the transverse rib web plates 330 and the length of the transverse rib flanges 340 that make up the transverse ribs 300 (described later), can be determined by analysis under various design conditions.

[0023] FIG. 2 shows the "rib intersection" of the steel deck 100, where (a) is a vertical cross-sectional view, and (b) is a horizontal cross-sectional view indicated by the arrow AA in FIG. 2(a). At the rib intersection, the longitudinal ribs 200 and the transverse ribs 300 intersect on the same plane, so a slit (hereinafter referred to as a "web slit 310" for convenience) is provided in the transverse rib 300 for inserting the longitudinal rib 200. The web slit 310 is an opening cut out to match the outer shape of the longitudinal rib 200, and inserting the longitudinal rib 200 into the web slit 310 eliminates overlap between the two. It is preferable to form a slightly enlarged space (a so-called scallop) below the web slit 310, the outer edge of which is curved (arc-shaped in the figure).

[0024] As explained above, the longitudinal ribs 200 and the transverse ribs 300 are each welded to the underside of the steel deck plate 400, but the longitudinal ribs 200 and the transverse ribs 300 are also welded to each other at rib intersections. The web plate slit 310 is, so to speak, a space surrounded by a wall surface (hereinafter referred to as the "inner wall") equal to the plate thickness of the transverse rib 300, and the longitudinal rib 200 accommodated in the web plate slit 310 is welded to the transverse rib 300 while abutting against this inner wall. However, one surface (hereinafter referred to as the "welding surface") of the web plate 210 of the longitudinal rib 200 is welded to the inner wall of the transverse rib 300; for example, in Figure 2(a), the left side of the web plate 210 is the welding surface, and a weld line WL is formed.

[0025] The vertical ribs 200 of the steel deck 100 of the present invention are structural steels equipped with flanges 220, and naturally, these flanges 220 are also housed in the web plate slits 310. Essentially, the flanges 220 are components that increase the rigidity of the vertical ribs 200, and therefore require a considerable overhang length. On the other hand, if the flanges 220 are long, the web plate slits 310 must be formed correspondingly wide, which means that the cross-sectional loss becomes large, which is detrimental to the structure of the transverse ribs 300.

[0026] In this case, it is possible to make the flange 220 have a considerable overhang length in the general section, but shorten the flange 220 at the rib intersection. However, if the overhang length of the flange 220 is changed drastically (discontinuously) when viewed in the bridge axis direction, the cross-sectional force will also change drastically, and there is a risk of unexpected stress concentration occurring at this discontinuous section.

[0027] Therefore, the steel deck 100 of the present invention is designed to form a "flange cutout 221" in the flange 220 of the vertical rib 200, as shown in Figure 2(b). This flange cutout 221 is formed so that the outer edge in a plan view is curved (semicircular in the figure) and so that the overhang length of the flange 220 is minimized at the rib intersection. The formation of this flange cutout 221 allows the flange 220 to have a considerable overhang length in the general area, while shortening the flange 220 at the rib intersection, and the overhang length of the flange 220 changes smoothly when viewed in the bridge axis direction. Furthermore, even at the flange cutout 221, the vertical rib 200 is provided with a short flange 220, providing rigidity equivalent to or greater than that of open-section ribs such as flat plate ribs and bulb plate ribs.

[0028] In the example shown in Figure 2(b), the outer edge of the flange cutout 221 is a semicircle with a relatively small diameter, but as shown in Figure 3, the outer edge of the flange cutout 221 can also be formed as a semicircle with a relatively large diameter. In this case, the cross-sectional force of the flange 220 changes gradually in the bridge axis direction, making it possible to further suppress unexpected stress concentration. Furthermore, the outer edge of the flange cutout 221 is not limited to a circle, and any curved shape can be selected, such as a parabola or a higher-order curve.

[0029] As mentioned above, although fatigue cracks at rib intersections have been reduced in steel decks 100 that use open cross-section vertical ribs 200, many fatigue cracks have been reported at rib intersections in the past. Therefore, a structure that can suppress fatigue cracks at rib intersections is also desirable for the steel deck 100 of the present invention.

[0030] In order to suppress fatigue cracks at rib intersections, it is effective to give the web plate slits 310 a distinctive shape. The inventors of the present invention analyzed the rib intersections, taking into consideration the flanges 220 of the longitudinal ribs 200, and discovered a shape for the web plate slits 310 that is effective in suppressing fatigue cracks.

[0031] The web plate slit 310 shown in Figure 4 is one of the shapes effective in suppressing fatigue cracks. A groove-shaped space (hereinafter referred to as the "first groove space 311") is formed on the welding surface side (left side in the figure) of the web plate 210 of the longitudinal rib 200, and a groove-shaped space (hereinafter referred to as the "second groove space 312") is also formed on the other side (right side in the figure) of the web plate 210. In addition, a scallop (hereinafter referred to as the "lower space 313") with a curved outer edge (approximately semicircular in the figure) is formed below the web plate 210, and the first groove space 311, the lower space 313, and the second groove space 312 are connected in this order from the left side to form the web plate slit 310. Note that Figures 4 and 5 are cross-sectional views used in the analysis, and therefore show the mesh used for the analysis.

[0032] The first groove-shaped space 311 is a strip-shaped space sandwiched between an inner wall on the right side (hereinafter referred to as the "first inner wall 311A") and an inner wall on the left side (hereinafter referred to as the "first outer wall 311B"), and is not open at the top, i.e., the web of the horizontal rib 300 remains at the top, and an inner wall is formed at the upper end of the first groove-shaped space 311. The outer edge of this inner wall at the upper end is curved (semicircular in the drawing) as shown in Figure 4.

[0033] The second groove-shaped space 312 is also a strip-shaped space sandwiched between a left inner wall (hereinafter referred to as the "second inner wall 312A") and a right inner wall (hereinafter referred to as the "second outer wall 312B"), and its upper part penetrates the transverse rib 300. The web of the transverse rib 300 remains between the first inner wall 311A ​​of the first groove-shaped space 311 and the second inner wall 312A of the second groove-shaped space 312; in other words, a thin plate material (hereinafter referred to as the "thin plate material 320") is formed. The longitudinal rib 200 inserted from the upper opening of the second groove-shaped space 312 is welded to the transverse rib 300 after the welding surface (left side in the drawing) of the web plate 210 abuts against the second inner wall 312A.

[0034] The web plate slit 310 shown in FIG. 5 is also one of the shapes that is effective in suppressing fatigue cracks, in which the second outer wall 312B is formed so as to be inclined relative to the web plate 210 (i.e., the second inner wall 312A). Therefore, the second groove-shaped space 312 of the web plate slit 310 shown in FIG. 5 is shaped so that its width increases upward. Analysis by the inventors has confirmed that inclining the second outer wall 312B in this manner is effective in suppressing fatigue cracks at intersections. Furthermore, as shown in FIG. 5, it has been confirmed that connecting the upper end of the second outer wall 312B and the opening of the second groove-shaped space 312 with a curved line (a circular arc CV in the figure) is even more effective in suppressing fatigue cracks. [Industrial Applicability]

[0035] The steel deck of the present invention can be used for a variety of bridges, including viaducts on urban expressways, bridges over rivers or oceans, overpasses over roads, and overpasses over railway tracks. It can be used not only for new bridges, but also when replacing existing decks. Given that the present invention provides safe transportation and enables high-quality, low-cost bridge construction, it can be said to be an invention that can be expected to not only be used industrially but also make a significant contribution to society. [Explanation of symbols]

[0036] 100 Steel deck of the present invention 200 (Steel deck) vertical rib 210 (longitudinal rib) web 220 (Vertical rib) flange 221 (Vertical rib) flange notch 300 (Steel deck) horizontal rib 310 (Horizontal rib) belly plate slit 311 (Belly plate slit) first groove-shaped space 311A (First groove space) first inner wall 311B First outer wall (of first channel space) 312 (Body slit) Second groove-shaped space 312A (Second groove space) second inner wall 312B Second outer wall (of second channel space) 313 (Belly plate slit) lower space 320 (Slit) Thin Plate 330 (horizontal rib) horizontal rib belly 340 (of horizontal rib) horizontal rib flange 400 (steel deck) steel deck plate CV curve section WL welding line

Claims

1. In the steel deck of bridges, Steel deck plate, Vertical ribs and a transverse rib; the longitudinal rib is a structural steel having a web plate arranged in the vertical direction and a flange provided at a lower end of the web plate, Among the horizontal ribs, a web slit for inserting the vertical rib is formed at a rib intersection where the vertical rib and the horizontal rib intersect, A flange notch is formed in the flange of the longitudinal rib, The flange cutout portion is formed so that the outer edge thereof has a curved shape in a plan view and the length of the flange is shortest at the rib intersection portion, The flange at the rib intersection is accommodated in the web plate slit, and the surface of one side of the web plate and the transverse rib are welded and joined. A steel deck characterized by:

2. The web plate slit has a first groove-shaped space formed on one side of the web plate, a second groove-shaped space formed on the other side of the web plate, and a lower space having a curved outer edge formed below the web plate, The web plate slit is a series of spaces in which the first groove-shaped space, the lower space, and the second groove-shaped space are connected to each other, The second groove-shaped space is formed so that an upper portion of the transverse rib is open, The first groove-shaped space is formed without an opening at the upper portion of the horizontal rib, and the outer edge of the upper end is curved, a thin plate material is formed between a first inner wall on the abdominal plate side among the inner walls constituting the first groove-shaped space and a second inner wall on the abdominal plate side among the inner walls constituting the second groove-shaped space, The web plate is welded to the second inner wall in abutting contact therewith.

2. The steel deck according to claim 1.

3. a second outer wall, which is different from the second inner wall among the inner walls constituting the second groove-shaped space, is formed so as to be inclined with respect to the web plate, The second groove-shaped space is formed so as to become wider upward.

3. The steel deck according to claim 2.

4. The outer edge of the upper end of the second outer wall is curved. The steel deck according to claim 3.

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