Bridge structure

Abstract

The present invention improves wind resistant performance of a bridge using 2-edge I-shaped main girders. A bridge structure according to the present invention comprises a bridge girder having a floor slab and a main girder including I-girders supporting the floor slab from below at both widthwise ends of the floor slab. The bridge girder is characterized by having, at both widthwise ends of the bridge girder, truncated wedge-shaped flow straightening members that extend outward of the floor slab, and is characterized in that: in the vertical direction, the ratio of the height of the truncated surface of the flow straightening members to the height of the flow straightening members is 0.25 or more; and the angle formed by a lower inclined surface provided on the under surface of each of the flow straightening members and the horizontal plane is 10-30 deg.

Description

Bridge structure

[0001] The present invention relates to a bridge structure provided with a bridge girder composed of, for example, two main I-girders at the ends.

[0002] Bridges are used as important structures in constructing social infrastructure. As a bridge girder used for such bridges, there is a two-main I-girder at the ends with a cross-section that reduces the weight of steel materials. In recent years, the development of bridges with a long span using two-main I-girders at the ends (hereinafter sometimes referred to as long-span bridges) has been promoted (see Non-Patent Documents 1 and 2).

[0003] Steel Structure Series 20 Steel Cable-Stayed Bridge - Technology and Transition - [2010 Edition], Japan Society of Civil Engineers, (2010) H. Yamada: Journal of Wind Engineering. JAWE 30 (1986) 41 - 55

[0004] By the way, although the bridge girder of two-main I-girders at the ends has the advantage that the manufacturing cost can be kept lower than that of a box girder bridge girder, there is a problem that the torsional rigidity and wind resistance performance of the girder cross-section are low. Therefore, long-span bridges using the bridge girder of two-main I-girders at the ends are difficult to be adopted in a meteorological environment where strong winds such as typhoons occur, and there is a problem that the meteorological environment for installation is limited.

[0005] The present invention has been made in view of the above problems, and an object thereof is to improve the wind resistance performance of a long-span bridge using a bridge girder composed of two-main I-girders at the ends.

[0006] A bridge structure according to an aspect of the present invention is a bridge structure provided with a bridge girder having a floor slab and a main girder including I-girders that support the floor slab from below at both ends in the width direction of the floor slab, wherein the bridge girder has, at both ends in the width direction of the bridge girder, frustum-shaped fairing members extending outward of the floor slab, and in the vertical direction, the ratio of the height of the frustum surface of the fairing member to the height of the fairing member is 0.25 or more, and the angle formed by a lower inclined surface provided on the lower surface of the fairing member and a horizontal plane is 10 deg. or more and 30 deg. or less.

[0007] Also, it is preferable that the length of the bridge girder in the width direction of the bridge girder is 15 m or less.

[0008] Furthermore, it is preferable that the ratio of the width excluding the flow straightening members to the height of the main girder is less than 5, and the ratio of the width including the flow straightening members to the height of the main girder is 6 or more.

[0009] Furthermore, it is preferable to provide a baffle plate on the underside of the bridge girder that extends along the direction of the deck slab, and that the ratio of the amount of protrusion of the baffle plate from the lowest part of the bridge girder to the length of the bridge girder in the width direction of the bridge girder be 1 / 11 or more.

[0010] According to the present invention, the wind resistance performance of a bridge girder consisting of two end main I-girders can be improved.

[0011] Figure 1(a) is a schematic side view showing one configuration of the cable-stayed bridge shown in this embodiment, and Figure 1(b) is a front view of the cable-stayed bridge shown in Figure 1(a). Figure 2 is a cross-sectional view of the bridge girder at position P0 of the cable-stayed bridge. Figure 3 is a cross-sectional view of the bridge girder with a baffle plate provided at the bottom. Figure 4 is a cross-sectional view showing the shape of the fairing. Figure 5 is a graph summarizing the angle of attack and the wind speed at which flutter occurs when using fairing 26A. Figure 6 is a graph summarizing the angle of attack and the wind speed at which flutter occurs when using fairing 26B. Figure 7 is a graph summarizing the angle of attack and the wind speed at which flutter occurs when using fairing 26C. Figure 8 is a graph summarizing the angle of attack and the wind speed at which flutter occurs when using fairing 26D. Figure 9 is a graph summarizing the angle of attack and the wind speed at which flutter occurs when using fairing 26E. Figure 10(a) shows the case where the wind blowing on the bridge girder is an updraft, Figure 10(b) shows the case where the wind blowing on the bridge girder is a downdraft, and Figure 10(c) shows the case where the wind blowing on the bridge girder is horizontal.

[0012] The embodiment will be described below with reference to the drawings. In the following description, a cable-stayed bridge having a bridge girder consisting of two main I-girders at each end will be given as an example of a bridge having a wind-resistant bridge structure, but the embodiment is not limited to a cable-stayed bridge as long as it has a bridge girder consisting of two main I-girders at each end.

[0013] As shown in Figure 1, the cable-stayed bridge 10 comprises main towers 11 and 12, a bridge girder 13, and a number of bridge piers 14. Although not shown in the figure, the bridge girder 13 is supported by bearings provided on the main towers 11 and 12 and on the bridge piers 14, and is also supported by a number of cables 15 that radiate outwards from the upper ends of the main towers 11 and 12.

[0014] For example, to increase the torsional rigidity of the cable-stayed bridge 10, the main towers 11 and 12 are of type A. Although type A towers are used for the main towers 11 and 12, it is also possible to use single-column towers, independent two-column towers, inverted Y-shaped towers, H-shaped towers, etc.

[0015] Figure 2 is a cross-sectional view of the bridge girder 13 at position P0 of the cable-stayed bridge 10 shown in Figure 1. As shown in Figure 2, for example, a bridge girder with two end main I girders is used as the bridge girder 13. The bridge girder 13 is, for example, a composite girder and is composed of a deck slab 21 and main girders 22. Examples of deck slabs 21 include reinforced concrete deck slabs, steel deck slabs, and PC deck slabs. The main girders 22 include I-shaped girders 23 and 24 and transverse girders 25. Here, the width W1 of the deck slab 21 is, for example, 15 m or less. Here, it is preferable that the ratio W1 / H1 of the width W1 of the deck slab 21 to the height H1 of the main girders 22 is less than 5.

[0016] The I-beams 23 and 24 are positioned at both ends of the deck slab 21 in the width direction (transverse direction) and along the extension direction (longitudinal direction) perpendicular to the width direction of the deck slab 21. The I-beam 23 has a web 23a and a lower flange 23b. Since the I-beam 24 has the same configuration as the I-beam 23, the configuration of the I-beam 24 is omitted here.

[0017] The transverse beams 25 are members arranged along the width direction of the deck slab 21. Multiple transverse beams 25 are arranged at predetermined intervals in the extending direction of the deck slab 21. Both ends 25a and 25b of the transverse beams 25 in the extending direction (width direction of the deck slab 21) protrude outward from the deck slab 21.

[0018] Fairings 26 and 27 are provided at both ends of the bridge girder 13 in the width direction, covering both ends 25a and 25b of the transverse girder 25, respectively. Although the example shows the fairings 26 and 27 covering both ends 25a and 25b of the transverse girder 25, the fairings 26 and 27 only need to be positioned to straddle the deck slab 21 and the I-beam 23 or I-beam 24 and cover the sides of the deck slab 21 and the I-beam 23 or I-beam 24, and it is not necessary for the fairings 26 and 27 to cover both ends 25a and 25b of the transverse girder 25.

[0019] The wind force acting on the bridge girder due to airflow can change due to the vibration of the girder itself, sometimes causing divergent vibrations. Vibrations in the deflection direction are called galloping, and divergent vibrations in the torsion direction are called flutter. It is known that such divergent vibrations can significantly increase the amplitude and torsion of the bridge girder, leading to bridge failure, partial damage, or fatigue failure. Therefore, in order to suppress vibrations acting on the bridge girder due to airflow, the bridge girder 13 shown in this embodiment is provided with fairings 26 and 27 at both ends in the width direction of the bridge girder 13.

[0020] Fairings 26 and 27 are components installed to streamline the airflow around the bridge girders and are also called wind-resistant stabilizing components. Fairings 26 and 27 are only installed if the wind resistance is poor and do not affect the structural design.

[0021] Since the fairings 26 and 27 are members that are symmetrical with respect to a straight line L1 passing through the midpoint in the width direction of the bridge girder 13, only the fairing 26 will be described below, and the description of the fairing 27 will be omitted.

[0022] The fairing 26 is a wedge-shaped member with a truncated section perpendicular to the extension direction of the bridge girder 13. The truncated wedge shape is, for example, the shape cut off by a vertical plane PL1 at a predetermined distance W3 from the intersection P1 of the upper inclined surface 26a and the lower inclined surface 26b of the fairing 26 toward the center of the bridge girder 13.

[0023] The distance from the base of the fairing 26 (side surface 21a of the floor slab 21) to the truncated surface 26c of the fairing 26, i.e., the overhang W2 of the fairing 26, is preferably, for example, W2 ≥ 1000 mm. Also, in the vertical direction, if the height of the fairing 26 is H2 and the height of the truncated surface 26c is H3, then H3 / H2 is preferably H3 / H2 ≥ 0.25. Furthermore, when the angle between the lower inclined surface 26b of the fairing 26 and the horizontal plane PL2 is θ1, then θ1 ≤ 30 deg. Preferably, θ1 is between 10 deg. and 30 deg.

[0024] The overhangs such as the fairings 26 and 27 are provided because, when streamlining the airflow, it is desirable for the width of the bridge girder to be larger than the height of the bridge girder. For example, the ratio of the width (W1 + 2 * W2) including the fairings 26 and 27 to the height H1 of the main girder 22 (W1 + 2 * W2) / H1 is preferably 6 or more, so that the flow that hits the upwind side of the bridge girder and separates reattaches to the downwind side of the bridge girder on a steady basis. In this case, the effect is greater for designs where the ratio W1 / H1 of the width W1 of the main girder 22 excluding the fairings 26 and 27 (in this case, the width of the deck slab 21) to the height H1 of the main girder 22 is less than 5. For example, if the ratio W1 / H1 is less than 5, the reattachment on the downwind side is non-steady (intermittent), and aerodynamic instability is likely to occur.

[0025] Furthermore, the angles of the fairings 26 and 27 are determined by the height H3 of the truncated surface and the overhang W2. The overhang W2 is also related to the overall width of the bridge girder, and as the angle decreases, the overhang W2 increases. The minimum angle of 10 degrees is determined because if the width of the bridge girder 13 is more than doubled by the installation of the fairings 26 and 27, the design itself becomes unreasonable.

[0026] Figure 2 illustrates the case where fairings 26 and 27 are provided at both ends of the bridge girder 13 in the width direction. In addition to providing fairings 26 and 27 at both ends of the bridge girder 13 in the width direction, it is also possible to provide a baffle plate 31 that protrudes downward from the lowest surface of the bridge girder 13 (the dashed line L2 in Figure 3) on the transverse girder 25. When the ratio of the amount of protrusion Hb of the baffle plate 31 protruding from the lowest surface of the bridge girder 13 to the width W1 of the deck slab 21 is defined as Hb / W1, it is preferable that the ratio Hb / W1 ≥ 1 / 11. Considering the manufacturing of the bridge girder 13 and the workability of the baffle plate 31, it is preferable that the amount of protrusion Hb of the baffle plate 31 be 2m or less.

[0027] Next, we present the results of a simulation that determined the wind speed at which flutter occurs. In the simulation, not only was the shape of the fairing changed, but the wind speed at which flutter occurs was also calculated for both cases: with and without a baffle plate.

[0028] The following shows the case where the angle between the upper inclined surface 26a and the horizontal plane PL2 and the angle between the lower inclined surface 26b and the horizontal plane are the same in the fairing 26.

[0029] First, let me explain the fairing 26 used in the above simulation. Five different types of fairings 26 with varying shapes were used. Hereinafter, these five types of fairings 26 will be referred to as fairing 26A, fairing 26B, fairing 26C, fairing 26D, and fairing 26E.

[0030] As shown in Figure 4(a), the fairing 26A has a wedge shape, where the cross-sectional shape perpendicular to the extension direction of the bridge girder 13 narrows as it moves away from the bridge girder 13. For example, the overhang W2A from the side surface 21a of the deck slab 21 to the tip of the fairing 26A is W2A = 102.9 cm. Also, the angle θ1A between the lower inclined surface 26bA and the horizontal plane PL2 is set to θ1A = 30 deg.

[0031] As shown in Figure 4(b), the fairing 26B, like the fairing 26A, has a wedge-shaped cross-section perpendicular to the extension direction of the bridge girder 13. For example, the overhang W2B from the side surface 21a of the deck slab 21 to the tip of the fairing 26B is W2B = 69.9 cm. Also, the angle θ1B between the lower inclined surface 26bB and the horizontal plane PL2 is set to θ1B = 49 degrees.

[0032] As shown in Figure 4(c), the fairing 26C has a truncated wedge shape in the cross-section perpendicular to the extension direction of the bridge girder 13. For example, the overhang W2C from the side surface 21a of the deck slab 21 to the tip of the fairing 26C is W2C = 69.8 cm. The angle θ1C between the lower inclined surface 26bC and the horizontal plane PL2 is θ1C = 30 deg. The height H1C of the fairing 26C is H1C = 76.3 cm. The height H2C of the truncated surface 26cC of the fairing 26C is H2C = 38.2 cm.

[0033] As shown in Figure 4(d), the fairing 26D has a truncated wedge shape in the cross section perpendicular to the extension direction of the bridge girder 13. For example, the overhang W2D from the side surface 21a of the deck slab 21 to the tip of the fairing 26D is W2D = 102.9 cm. The angle θ1D between the lower inclined surface 26bD and the horizontal surface PL2 is θ1D = 16 deg. The height H1D of the fairing 26D is H1D = 76.3 cm. The height H2D of the truncated surface 26cD of the fairing 26D is H2D = 38.2 cm.

[0034] As shown in Figure 4(e), the fairing 26E has a truncated wedge shape in the cross-section perpendicular to the extension direction of the bridge girder. For example, the overhang W2E from the side surface 21a of the deck slab 21 to the tip of the fairing 26E is W2E = 102.9 cm. The angle θ1E between the lower inclined surface 26bE and the horizontal plane PL2 is θ1E = 23 deg. The height H1E of the fairing 26E is H1E = 76.3 cm. The height H2E of the truncated surface 26cE of the fairing 26E is H2E = 19.1 cm.

[0035] Furthermore, when the baffle plate 31 is present, the above-mentioned Hb / W1 was set to Hb / W1 = 1 / 10.7.

[0036] The wind speed at which flutter occurs was determined by blowing wind from the side of the bridge girder 13 having the fairing 26 described above. Figures 5 to 9 summarize the angle of attack and the change in wind speed at which flutter occurs for bridge girders using the five types of fairings 26 described above. The direction of the wind blowing onto the bridge girder 13 from the side (hereinafter referred to as the angle of attack α) was varied in the range of -3 to 3 degrees.

[0037] Here, as shown in Figure 10(a), when the angle of attack α is a positive value (α > 0), the bridge girder 13 is subjected to wind from below (upward wind). Also, as shown in Figure 10(b), when the angle of attack α is a negative value (α < 0), the bridge girder 13 is subjected to wind from above (downward wind). Furthermore, as shown in Figure 10(c), when the angle of attack α is 0 (α = 0), the bridge girder 13 is subjected to horizontal wind along the width direction of the bridge girder 13.

[0038] In the wind-resistant design of bridges in Japan, it is sufficient that the wind speed at which flutter occurs exceeds the verification wind speed S when the angle of attack α is 0 degrees, +3 degrees, and -3 degrees. For example, the verification wind speed S at which flutter due to torsion occurs varies depending on the construction environment and construction height. In this embodiment, we illustrate the case where the verification wind speed S is set to 53.9 m / s.

[0039] Figure 5 shows the case with fairing 26A. In Figure 5, the case without the fairing is illustrated with a black circle as a comparative example. Also in Figure 5, black triangles indicate the case with fairing 26A, and white triangles indicate the case with fairing 26A and baffle plate 31. When the fairing is not provided, flutter occurs at wind speeds of around 30 m / s, which is lower than the checked wind speed S, regardless of whether the angle of attack α = -3 deg., α = 0, or α = 3 deg.

[0040] On the other hand, when using fairing 26A, the wind speed was 21.4 m / s at an angle of attack α = -3 degrees, 41.9 m / s at an angle of attack α = 0, and 68.7 m / s at an angle of attack = 3 degrees. As mentioned above, if the verification wind speed S is 53.9 m / s, the wind speed when flutter occurs due to torsion is higher than the verification wind speed S during updrafts. It was found that when the angle of attack α = 0 and α = -3 degrees, the wind speed when flutter occurs due to torsion is lower than the verification wind speed S.

[0041] On the other hand, when using the fairing 26A and baffle plate 31, the wind speed remained constant at 84.2 m / s even when the angle of attack α changed. In other words, it was found that when using the fairing 26A and baffle plate 31, the wind speed at which flutter occurs due to twisting is higher than the checked wind speed S. When using the fairing 26A, using the baffle plate 31 in combination increases the wind speed at which flutter occurs, but it was found that the wind speed is higher than the checked wind speed S only when the angle of attack α becomes a positive value, i.e., in the case of updraft.

[0042] Figure 6 shows the case using fairing 26B. In this figure, the black squares show the case using only fairing 26B. The white squares show the case using both fairing 26B and baffle plate 31.

[0043] When using fairing 26B, the wind speed was 59.4 m / s at an angle of attack α = -3 degrees, 55.7 m / s at an angle of attack α = 0, and 32.2 m / s at an angle of attack α = 3 degrees. As mentioned above, if the verification wind speed S is 53.9 m / s, the wind speed at which flutter occurs due to torsion is higher than the verification wind speed S when the angle of attack α = 0 and α = -3 degrees. On the other hand, it was found that when the angle of attack α = 3 degrees, the wind speed is lower than the verification wind speed S.

[0044] Also, when the fairing 26B and the baffle plate 31 are used, the angle of attack α = -3 deg., the wind speed is 61.2 m / s, the angle of attack α = 0, the wind speed is 65.4 m / s, and the angle of attack α = 3 deg., the wind speed is 33.8 m / s. When flutter occurs due to torsion, the wind speed when the angle of attack α = 0, α = -3 deg. is higher than the inspection wind speed S. On the other hand, when the angle of attack α = 3 deg., it was found that the wind speed when flutter occurs due to torsion is lower than the inspection wind speed S. That is, when the fairing 26B is used, the wind speed when flutter occurs becomes higher by using the baffle plate 31, but it was found that the wind speed itself when flutter occurs does not change much.

[0045] Figure 7 shows the case when the fairing 26C is used. In the figure, the black triangles indicate the case when only the fairing 26C is used. The white triangles indicate the case when the fairing 26C and the baffle plate 31 are used.

[0046] Also, when the fairing 26C is used, the angle of attack α = -3 deg., the wind speed is 73.5 m / s, the angle of attack α = 0, the wind speed is 89.0 m / s, and the angle of attack α = 3 deg., the wind speed is 52.3 m / s. When the angle of attack α = 0, α = -3 deg., the wind speed when flutter occurs due to torsion is higher than the inspection wind speed S. On the other hand, when the angle of attack α = 3 deg., it was found that the wind speed when flutter occurs due to torsion is lower than the inspection wind speed S.

[0047] Also, when the fairing 26C and the baffle plate 31 are used, the angle of attack α = -3 deg., the wind speed is 97.0 m / s, the angle of attack α = 0, the wind speed is 98.8 m / s, and the angle of attack α = 3 deg., the wind speed is 73.5 m / s. When the inspection wind speed S is 53.9 m / s, it was found that the wind speed when flutter occurs due to torsion is higher than when only the fairing 26C is used.

[0048] Figure 8 shows the case when the fairing 26D is used. In the figure, the black squares indicate the case when the fairing 26D is used. The white squares indicate the case when the fairing 26D and the baffle plate 31 are used.

[0049] When using fairing 26D, the wind speed was 66.2 m / s at an angle of attack α = -3 degrees, 82.9 m / s at an angle of attack α = 0, and 89.0 m / s at an angle of attack α = 3 degrees. Furthermore, when using both fairing 26D and baffle plate 31, the wind speed was 78.7 m / s at an angle of attack α = -3 degrees, 88.5 m / s at an angle of attack α = 0, and 79.4 m / s at an angle of attack = 3 degrees.

[0050] In this case, assuming a test wind speed of 53.9 m / s, it was found that the wind speed at which flutter occurs is higher than the test wind speed S, regardless of whether the baffle plate 31 is present or not, and regardless of whether the angle of attack α = 0, α = -3 degrees, or α = 3 degrees. Furthermore, it was found that when using the fairing 26D and the baffle plate 31, the wind speed at which flutter occurs is lower when the angle of attack α is α = 3 degrees than when using the fairing 26D.

[0051] Figure 9 shows the case using the fairing 26E. In this figure, the black triangle indicates the case using the fairing 26E. The white triangle indicates the case using both the fairing 26E and the baffle plate 31.

[0052] Furthermore, when using the fairing 26E, the wind speed was 88.5 m / s at an angle of attack α = -3 degrees, 85.5 m / s at an angle of attack α = 0, and 78.7 m / s at an angle of attack α = 3 degrees. Additionally, when using both the fairing 26E and the baffle plate 31, the wind speed was 92.7 m / s at an angle of attack α = -3 degrees, 92.0 m / s at an angle of attack α = 0, and 79.2 m / s at an angle of attack = 3 degrees.

[0053] When using the fairing 26E, it was found that the wind speed at which flutter occurs is higher than the checked wind speed S, regardless of whether the baffle plate 31 is present or not, and in all cases of angle of attack α = 0, α = -3 degrees, and α = 3 degrees.

[0054] Thus, when any of the fairings 26C, 26D, or 26E are used, the wind speed at which flutter occurs is higher than the checked wind speed S. This indicates high wind resistance safety. Furthermore, when the baffle plate 31 is used in addition to any of the fairings 26C, 26D, or 26E, the wind speed at which flutter occurs is higher than when only the fairings 26C, 26D, or 26E are used. In other words, the baffle plate 31 contributes to wind resistance safety in bridges.

[0055] <Summary of Effects> The bridge structure of this embodiment is a bridge girder 13 having a deck slab 21 and a main girder 22 including I-shaped girders 23, 24 that support the deck slab 21 from below at both ends in the width direction of the deck slab 21, and is characterized in that the deck slab 21 has truncated wedge-shaped fairings 26, 27 extending outward from the deck slab 21 at both ends of the deck slab 21, the ratio of the height H3 of the truncated surfaces 26c, 27c of the fairings 26, 27 to the height H2 of the fairings 26, 27 in the vertical direction is 0.25 or more, and the angle θ1 between the lower inclined surfaces 26b, 27b provided on the lower surface of the fairings 26, 27 and the horizontal plane PL2 is 10 deg. to 30 deg.

[0056] According to this, when wind blows from the side of the bridge girder toward the girder, the reattachment of vortices generated by separation at the tips of the fairings 26 and 27 can be promoted, and as a result, wind resistance stability can be improved. The improvement in wind resistance stability is particularly noticeable when the length of the bridge girder 13 in the width direction is 15 m or less, and the ratio of the width (W1 + 2 * W2) excluding the fairings 26 and 27 to the height H1 of the main girder 22 (W1 + 2 * W2) / H1 is 6 or more.

[0057] Furthermore, a baffle plate 31 is provided on the underside of the bridge girder 13, extending along the direction of extension of the deck slab 21, and it is preferable that the ratio of the amount of protrusion of the baffle plate 31 from the lowest part of the bridge girder 13 to the length of the bridge girder 13 in the width direction of the bridge girder 13 is 1 / 11 or more.

[0058] According to this, the baffle plate 31 can suppress the occurrence of flutter caused by twisting in the bridge girder 13 by breaking up vortices that have separated at the tip of the fairing 26 or fairing 27, for example, when there is strong wind.

[0059] 10 Cable-stayed bridge 11, 12 Main tower 13 Bridge girder 14 Bridge pier 15 Cable 21 Deck (reinforced concrete deck, steel deck, PC deck, etc.) 22 Main girder 23, 24 I-beam 25 Cross girder 26, 27 Fairing 31 Baffle plate

Claims

1. A bridge structure comprising a bridge girder having a deck slab and a main girder including an I-shaped girder that supports the deck slab from below at both ends in the width direction of the deck slab, wherein the bridge girder has a truncated wedge-shaped flow straightening member extending outward from the deck slab at both ends in the width direction of the bridge girder, the ratio of the height of the truncated surface of the flow straightening member to the height of the flow straightening member in the vertical direction is 0.25 or more, and the angle between the lower inclined surface provided on the lower surface of the flow straightening member and the horizontal plane is 10 deg. to 30 deg.

2. A bridge structure according to claim 1, characterized in that the length of the bridge girder in the width direction is 15 m or less.

3. A bridge structure according to claim 2, characterized in that the ratio of the width excluding the flow straightening member to the height of the main girder is less than 5, and the ratio of the width including the flow straightening member to the height of the main girder is 6 or more.

4. The bridge structure according to any one of claims 1 to 3, characterized in that a baffle plate is provided on the lower surface of the bridge girder, extending in the direction of extension of the deck slab, and the ratio of the amount of protrusion of the baffle plate from the lowest part of the bridge girder to the length of the bridge girder in the width direction of the bridge girder is 1 / 11 or more.

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