KR102173516B1 - Flange open type box girder and continuous bridge using the same - Google Patents

Abstract

According to an embodiment of the present invention, an upper and lower flange opening type box girder includes: a steel box girder main body in which a bridge slab is provided on an upper surface portion and of which a lower surface portion is arranged to be mounted on a point portion such as a pier; an upper flange forming the upper surface portion of the steel box girder main body and having an upper opening in a position corresponding to a positive moment section of the steel box girder main body; a lower flange forming the lower surface portion of the steel box girder main body and having a lower opening in a position corresponding to a negative moment section of the steel box girder main body; and a point support part placed into the lower opening with a concrete material and provided on the lower flange to be mounted on the point portion. Therefore, the upper and lower flange opening type box girder can reduce a construction cost of a bridge.

Description

Upper and lower flange open type box girder and continuous bridge using it {FLANGE OPEN TYPE BOX GIRDER AND CONTINUOUS BRIDGE USING THE SAME}

The present invention relates to an upper and lower flanged open box girder and a continuous bridge using the same, and more particularly, it is possible to significantly reduce the amount of steel used in the box girder used in the construction of the continuous bridge, and effectively reinforce the negative moment section of the box girder. It relates to an upper and lower flange open type box girder and a continuous bridge using the same.

In general, a continuous bridge is a bridge whose main structure is a continuous beam or a continuous truss having three or more points. In particular, the structure of a girder is continuous over two spans or more. It is an old bridge.

The girder as described above supports the load of traffic such as automobiles and trains and the weight of the upper structure of the bridge, but corresponds to the upper structure of the bridge for transmitting to the lower structure of the bridge such as a bridge pier or a shift.

In particular, in recent years, the use of steel box girders utilizing steel-concrete dual synthesis is increasing.

In the steel box girder of the steel-concrete dual composite as described above, the flexural compressive force in the positive moment section is received by the bridge slab made of concrete material, and the flexural tensile force in the positive moment section is received by the steel box girder. That is, steel box girders of a steel-concrete dual composite have been widely used because they utilize the advantages of different materials and are structurally advantageous and economically advantageous compared to non-synthetic steel box girders.

However, the existing steel-concrete dual-composite steel box girder has a problem in that an excessive positive moment occurs at a point connected to the pier when designing and constructing a continuous bridge. Accordingly, a cross-sectional loss of the bridge slab may occur at the point portion, and the flexural stiffness may be lowered.

In recent years, due to the trend of low-height-long spanning, the above problems have become more prominent, and appropriate reinforcement is required for the negative moment section of the continuous bridge.

Various methods have been attempted to solve the above problems. For example, a concrete double-composite method is being attempted to place concrete in the negative moment section.

Specifically, in Korean Patent Registration No. 10-0906400 (name of the invention: steel-composite steel box girder bridge and its construction method, registration date: 2009.06.30), a U-shaped flange is formed on the upper part of the abdomen in a closed and open cross-section shape. , A steel-composite steel box girder bridge in which high-strength concrete is poured and synthesized on a U-shaped flange and its construction method are disclosed. Therefore, in Korean Patent Registration No. 10-0906400, it is possible to reduce the amount of expensive steel required by appropriately using concrete and steel according to compressive stress and tensile stress in the positive moment section and the negative moment section.

However, the existing concrete double-composite method needs to further secure economic feasibility by further increasing the efficiency of reducing the amount of steel used according to the additional use of concrete materials.

In particular, the average span length of continuous bridges using steel box girders is 50-55m, but in recent years, due to the trend of long spanning and the increase in the cost of steel, there is a new demand for steel reduction between 50-70m span lengths.

To this end, a steel-concrete dual composition is applied to the negative moment section of the steel box girder, but studies on reducing the amount of steel required by reducing the cross section of the upper and lower flanges are actively being conducted.

Korean Patent Registration No. 10-0906400 (Registration 2009.06.30)

An embodiment of the present invention provides an upper and lower flanged open box girder and a continuous bridge using the same, which can effectively reinforce the negative moment section of the steel box girder and significantly reduce the amount of steel used to reduce the construction cost of the bridge. .

In addition, an embodiment of the present invention provides an upper and lower flange open box girder and a continuous bridge using the same, which can significantly reduce the amount of steel used in the steel box girder by forming openings in the upper and lower flanges of the steel box girder.

In addition, an embodiment of the present invention is an open-type box girder with upper and lower flanges that can sufficiently secure reinforcement performance at a lower price compared to a structure using only steel by applying a dual composite of steel-concrete material in the negative moment section of the steel box girder. And it provides a continuous bridge using the same.

According to an embodiment of the present invention, a steel box girder body in which a bridge slab is provided on an upper surface and a lower surface is disposed at a point such as a pier, and an upper surface of the steel box girder body is formed, and the steel box An upper flange having an upper opening at a position corresponding to a positive moment section of the girder body, a lower flange forming a lower surface of the steel box girder body and having a lower opening at a position corresponding to the negative moment section of the steel box girder body, and It provides an upper and lower flange open-type box girder including a support part provided on the lower flange so that the concrete material is poured into the lower opening and seated at the point.

Preferably, the upper flange may support tensile stress applied to the positive moment section of the steel box girder body, and the lower flange may support tensile stress applied to the positive moment section of the steel box girder body. . In addition, the bridge slab may support compressive stress applied to the positive moment section of the steel box girder body, and the point support part may support compressive stress applied to the negative moment section of the steel box girder body.

Preferably, in the upper flange and the lower flange, a non-opening region in which neither the upper opening nor the lower opening is formed may be formed at a boundary between the positive moment section and the negative moment section. To this end, the upper opening and the lower opening may be disposed at a position spaced apart from the boundary between the positive moment section and the negative moment section.

Preferably, the upper opening and the lower opening may be formed to be elongated along the length direction of the steel box girder body. Round portions may be provided at both ends of the upper opening and the lower opening in a semicircular shape or an arc shape having a constant curvature.

The diameter of the round portion may be provided to have a length ratio of 0.60 to 0.80 with respect to the widths of the upper flange and the lower flange.

Preferably, the point support may be formed on the upper surface of the lower flange to be accommodated in the inside of the steel box girder body.

Here, the branch support and the bridge slab may be provided with a concrete structure. At this time, it is preferable that the support portion is formed thicker than the bridge slab.

In addition, a plurality of negative moment sections may be formed in the steel box girder body. In this case, the point support may be provided at positions corresponding to the negative moment sections, respectively.

In the inside of the steel box girder body as described above, a concrete pouring portion for pouring the point support portion may be provided below a portion corresponding to the negative moment section.

On the other hand, according to another aspect of the present invention, it provides a continuous bridge, characterized in that constructed using the upper and lower flange open-type box girder as described above.

The upper and lower flange open box girder and the continuous bridge using the same according to the embodiment of the present invention have an upper opening in the positive moment section of the upper flange and a lower opening in the negative moment section of the lower flange, so the upper opening and the lower Due to the formation of the opening, the amount of steel used for the upper and lower flanges can be reduced, and construction costs can be reduced according to the reduction of the amount of steel.

In addition, in the upper and lower flange open box girder and the continuous bridge using the same according to the embodiment of the present invention, the bridge slab is provided on the upper surface of the steel box girder body, and the branch support is poured into the lower opening of the lower slab corresponding to the branch. Since it is a structure, it is possible to effectively support the compressive stress applied to the upper flange of the positive moment section by using the bridge slab made of concrete, and the compressive stress applied to the lower flange of the negative moment section by using the point support part of the concrete material. I can support it.

In addition, the upper and lower flanged open box girders and continuous bridges using the same according to an embodiment of the present invention support the tensile stress applied to the upper and lower flanged open-type box girders with a steel structure as well as compressive stress applied to the upper and lower flanged open-type box girders. Since the structure is supported by a concrete structure, it is possible to effectively reinforce the supporting structure of the steel box girder body because it is supported by a structure having excellent support efficiency of compressive stress and tensile stress, respectively. Therefore, in this embodiment, even when the upper opening is formed in the positive moment section of the upper flange and the lower opening is formed in the negative moment section of the lower flange, the deterioration of the reinforcing performance is stably reduced by the bridge slab and the branch support. Not only can it be compensated, but the reinforcement performance can be significantly increased.

In addition, the upper and lower flange open box girders and the continuous bridge using the same according to the embodiment of the present invention have an upper opening and a lower opening at a position spaced apart from the boundary between the positive moment section and the negative moment section, so the upper opening A non-opening area in which both the and lower openings are not formed can be provided in a predetermined size at the boundary between the positive moment section and the negative moment section, thereby stably reinforcing the area where the positive moment and the negative moment alternate with each other, resulting in tensile stress. It can efficiently support over compressive stress.

1 is a view schematically illustrating a top and bottom flange open box girder, a BMD graph, and a plan view of an upper flange and a lower flange according to an embodiment of the present invention.
FIG. 2 is a perspective view showing a view of the upper and lower flange open-type box girders shown in FIG. 1 from an upper side.
FIG. 3 is a perspective view showing a view of the upper and lower flange open-type box girders shown in FIG. 1 from a lower side.
4 to 6 are views showing cross-sections taken along lines AA, BB and CC shown in FIG. 1, respectively.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited or limited by the embodiments. The same reference numerals in each drawing indicate the same members.

1 is a view schematically showing a top and bottom flange open box girder 100, a B.M.D graph, and a plan view of an upper flange 120 and a lower flange 130 according to an embodiment of the present invention. FIG. 2 is a perspective view showing the upper and lower flange open type box girder 100 shown in FIG. 1 as viewed from the upper side, and FIG. 3 is a perspective view showing the upper and lower flange open type box girder 100 shown in FIG. 1 as viewed from the lower side to be. 4 to 6 are views showing cross-sections along lines A-A, B-B, and C-C shown in FIG. 1, respectively.

Referring to Figure 1, the continuous bridge 10 according to an embodiment of the present invention can be constructed using the upper and lower flange open type box girder (100).

As shown in (a) of Figure 1, the upper and lower flange open type box girder 100, as an upper structure of the continuous bridge 10 supported by the point 20 such as a pier, the bridge slab 30 It may be provided on the upper surface, the lower surface may be seated on the point portion (20). The bridge slab 30 may be provided with a concrete structure, and the upper and lower flange open box girder 100 may be provided with a steel-concrete dual composite structure.

Hereinafter, in the present embodiment, it will be described that the continuous bridge 10 is a two span continuous bridge for convenience of explanation. That is, the upper and lower flange open type box girder 100 is supported by the three point portions 20. At this time, the point portion 20 may be positioned at both ends and the middle portion of the upper and lower flange open box girder 100, respectively.

As shown in (b) of FIG. 1, a bending moment may be applied to the continuous bridge 10. That is, in (b) of FIG. 1 is a B.M.D (bending moment diagram) showing the bending moment acting on the continuous bridge 10 is shown.

The bending moment may be formed in a parabolic shape that is convex downwards between the point portions 20. The bending moment acting as described above is a positive moment, and is shown as "+".

At the point portion 20 disposed in the middle portion of the upper and lower flange open box girder 100, the bending moment may be formed in a triangular shape sharp upward. The bending moment acting as described above is a negative moment, and is indicated by "-".

Hereinafter, in the present embodiment, a section in which a positive moment is applied is referred to as a'positive moment section (PM)', and a section in which a parent moment is applied is referred to as a'negative moment section (NM)'. Here, the point where the positive moment and the positive moment are "0" is the boundary part E-E that divides the positive moment section PM and the positive moment section NM. In the boundary portion E-E between the positive moment section PM and the negative moment section NM as described above, the positive moment and the positive moment may be alternated.

On the other hand, in the positive moment section (PM) of the continuous bridge 10, a tensile stress may be applied to the lower part of the upper and lower flange open box girder 100 based on the neutral axis of the upper and lower flange open box girder 100, and the upper and lower flange A compressive stress may be applied to the upper and lower flanges of the open box girder 100 based on the neutral axis of the open box girder 100.

The compressive stress applied to the upper portion of the upper and lower flange open type box girder 100 as described above may be supported by the bridge slab 30 disposed on the upper surface of the upper and lower flange open type box girder 100. This is because the upper part of the upper and lower flange open type box girder 100 is formed of steel, but the bridge slab 30 is formed of a concrete structure that withstands a greater compressive stress than the upper part of the upper and lower flange open type box girder 100.

In addition, in the negative moment section (NM) of the continuous bridge 10, a compressive stress may be applied to the lower portion of the upper and lower flange open type box girder 100 based on the neutral axis of the upper and lower flange open type box girder 100, and the upper and lower flange Tensile stress may be applied to the upper and lower flanges of the open box girder 100 based on the neutral axis of the open box girder 100.

As described above, the compressive stress applied to the lower portion of the upper and lower flange open type box girder 100 is a point support 140, which will be described later, provided at a position to be seated on the point portion 20 among the lower surfaces of the upper and lower flange open type box girder 100. Can be supported by This is because the lower part of the upper and lower flange open type box girder 100 is formed of steel, but the branch support 140 is a concrete structure that withstands a greater compressive stress than the lower part of the upper and lower flange open type box girder 100.

On the other hand, recent bridges are required to rationalize structures and improve construction efficiency in order to reduce construction costs. In particular, in recent years, as bridges have become low-profile and long-span, there is a trend of using high-strength steel for steel box girders. Therefore, even a slight increase in the amount of steel used in the steel box girder can greatly increase the construction cost, and even a small decrease in the amount of steel used in the steel box girder can significantly reduce the construction cost.

In order to cope with this, in the continuous bridge 10 of the present embodiment, the upper and lower flange open type box girder 100 is provided in a structure to reduce the amount of steel used for the part by receiving the part where the compressive stress acts on the concrete structure. .

For example, the upper and lower flange open box girder 100 is reinforced by applying a steel-concrete dual composition to the central point portion 20 where the lower parental moment is concentrated, but the point portion ( 20) can reduce the amount of steel used.

Hereinafter, the configuration of the upper and lower flange open type box girder 100 of the present embodiment will be described in more detail.

1 to 3, the upper and lower flange open-type box girder 100 according to an embodiment of the present invention, a steel box girder body 110, an upper flange 120, a lower flange 130, and a branch support Includes 140.

Here, the upper and lower flange open-type box girders 100 may be connected while being continuously seated on the point portions 20 after a plurality of units are manufactured at the site when the continuous bridge 10 is constructed.

In addition, the steel box girder body 110 and the upper flange 120 and the lower flange 130 may be formed of a steel material, and the branch support 140 may be formed of a concrete material. In particular, the steel box girder body 110 and the upper flange 120 and the lower flange 130 are high-strength steel materials with high unit cost and high cost to sufficiently cope with the positive moment and the positive moment acting on the long-span continuous bridge 10 Can be provided with.

1 to 3, the steel box girder body 110 of this embodiment may include all other portions of the upper and lower flange open box girders 100 except for the upper and lower surfaces. A bridge slab 30 may be provided on the upper surface of the steel box girder body 110. The lower surface of the steel box girder body 110 may be disposed so as to be seated on the points 20 such as piers.

The bridge slab 30 may be provided to support a compressive stress applied to the positive moment section PM of the steel box girder body 110. To this end, the bridge slab 30 may be formed of a concrete structure having excellent strength against compressive stress.

2 and 3, the steel box girder body 110 may include a diaphragm 112, a web 114, and a flange reinforcement 116.

A plurality of diaphragms 112 may be provided inside the steel box girder body 110 to be spaced apart along the longitudinal direction. The diaphragm 112 as described above may be formed as a plate-shaped partition wall partitioning the inside of the steel box girder body 110. Accordingly, the diaphragm 112 may prevent buckling of the steel box girder body 110 receiving a positive moment or a positive moment, or increase the rigidity of the steel box girder body 110 against torsion.

Here, as shown in Figure 2, the upper end portion of the diaphragm 112 may be provided with an upper shear connector fastening portion 112a for fastening a shear connector (not shown) connected to the bridge slab 30, respectively. .

In addition, as shown in FIG. 3, a lower front end connector (112b) for fastening a front end connector (not shown) connected to the branch support unit 140 may be provided at the lower end of the diaphragms 112. . However, at the lower end of the diaphragm 112 disposed at the point portion 20 of the diaphragms 112, a lower shear connector formed with a wider width than the lower shear connector fastening part 112b of the other diaphragm 112 A fastening part 112c may be provided.

The web 114 is a member forming the left side and the right side of the steel box girder body 110, and is also referred to as a'abdominal member'. The web 114 as described above may constitute an abdominal cross section that resists shearing force acting on the upper and lower flange open box girders 100.

The flange reinforcement 116 may be provided for strength reinforcement on at least one of the side of the diaphragm 112, the inner side of the web 114, the inner side of the upper flange 120, or the inner side of the lower flange 130. have. The flange reinforcement 116 as described above is formed to be elongated in a thin bar shape, and may protrude in the shape of a vertical grid and a horizontal grid.

1 to 3, the upper flange 120 of this embodiment is a member forming the upper surface of the steel box girder body 110. The upper flange 120 may be formed in a flat plate structure disposed horizontally on the upper surface of the steel box girder body 110. The upper flange 120 as described above may support a tensile stress applied to the negative moment section NM.

Here, the upper flange 120 may be provided with an upper opening 122 at a position corresponding to the positive moment section (PM) of the steel box girder body 110. The upper opening 122 may be formed long along the length direction of the steel box girder body 110. Therefore, the upper flange 120 is a structure that is almost impossible to respond to compressive stress in the positive moment section (PM), but the bridge slab 30 provided with concrete sufficiently supports the compressive stress in the positive moment section (PM) Therefore, a problem due to compressive stress does not occur in the positive moment section PM.

The upper opening 122 as described above is disposed or formed at a position separated by a set distance along the length direction of the steel box girder body 110 at the boundary EE between the positive moment section PM and the negative moment section NM. Can be.

In addition, upper round portions 124 may be provided at both ends of the upper opening 122 in a semicircular shape or an arc shape having a constant curvature for smooth stress transfer. The diameter D of the upper round portion 124 as described above may be provided to have a length ratio of 0.60 to 0.80 with respect to the width W of the upper flange 120.

1 to 3, the lower flange 130 of the present embodiment is a member forming the lower surface of the steel box girder body 110. For reference, FIG. 3 is a perspective view showing a state in which the lower flange 130 is positioned above the upper and lower portions of the steel box girder body 110 shown in FIG. 2.

The lower flange 130 may be formed in a flat plate structure disposed horizontally on the lower surface of the steel box girder body 110. The lower flange 130 as described above may support tensile stress applied to the positive moment section PM.

Here, the lower flange 130 may be provided with a lower opening 132 at a position corresponding to the negative moment section NM of the steel box girder body 110. The lower opening 132 may be formed long along the length direction of the steel box girder body 110. Therefore, the lower flange 130 is a structure that is almost impossible to respond to the compressive stress in the negative moment section (NM), but because the point support 140 provided with concrete sufficiently supports the compressive stress in the negative moment section (NM) No problem due to compressive stress occurs in the negative moment section (NM).

The lower opening 132 as described above may be disposed at a position separated by a set distance along the length direction of the steel box girder body 110 at the boundary EE between the positive moment section PM and the negative moment section NM. have. At this time, the distance between the upper opening 122 and the lower opening 132 may be set to be the same, but the separation distance is set differently depending on the design conditions and circumstances of the upper and lower flange open box girder 100 It could be.

Therefore, in the upper and lower flange open box girder 100, the upper opening 122 and the lower opening 132 are not formed around the boundary EE between the positive moment section PM and the negative moment section NM. An opening area F may be formed. The non-opening region F as described above is an alternating region of the positive moment and the parent moment, and can appropriately respond to the alternating situation of the positive moment and the parent moment. The length of the non-opening region F may be formed to have a length corresponding to a total distance between the upper opening 122 and the lower opening 132.

In addition, lower round portions 134 may be provided at both ends of the lower opening 132 in a semicircular shape or an arc shape having a constant curvature for smooth stress transfer. The diameter D of the lower round portion 134 as described above may be provided to have a length ratio of 0.60 to 0.80 with respect to the width W of the lower flange 130.

Hereinafter, in this embodiment, as shown in (c) and (d) of FIG. 1, the widths (W) of the upper flange 120 and the lower flange 130 are formed equal to each other, and the upper round portion 124 It will be described that the diameters (D) of the and the lower round portions 134 are also formed equal to each other. In addition, in the present embodiment, it is described that the upper opening 122 and the lower opening 132 are formed to have the same width as the diameter D of the upper round portion 124 and the lower round portion 134, but are limited thereto. The width of the upper opening 122 and the lower opening 132 may be appropriately changed according to the design conditions and circumstances of the upper and lower flange open box girder 100.

1 to 3, the point support part 140 of the present embodiment may be provided on the lower flange 130 to be seated on the point portion 20. That is, the branch support 140 may be formed in a structure in which a concrete material is poured into the lower opening 132 of the lower flange 130.

Here, the branch support 140 may support compressive stress applied to the negative moment section NM of the steel box girder body 110. Therefore, when a plurality of negative moment sections NM are formed on the steel box girder body 110, respectively, the point support 140 may be provided at positions corresponding to the negative moment sections NM, respectively.

In addition, the branch support 140 may be provided with a concrete structure identical to and similar to the bridge slab 30. At this time, the branch support 140 is preferably formed thicker than the bridge slab 30. Because the overall cross-sectional area of the branch support 140 is smaller than that of the bridge slab 30, the thickness of the branch support 140 is designed to be larger than the bridge slab 30 in order to sufficiently respond to the compressive stress of the negative moment section (NM). Can be.

In addition, the branch support 140 may be formed on the upper surface of the lower flange 130, and accordingly may be provided in a shape accommodated in the inside of the steel box girder body 110. To this end, as shown in FIG. 6, a concrete pouring portion 142 for pouring concrete to the point support 140 may be provided inside the steel box girder body 110. The concrete pouring portion 142 may be formed at the lower side of the portion corresponding to the negative moment section NM in the inside of the steel box girder body 110, and may be provided to communicate with the lower opening 132.

As described above, in the inner part of the steel box girder body 110 corresponding to the negative moment sections (NM), the concrete pouring part 142 is formed, so the lower part of the diaphragms 112 disposed therein is also concrete It has been removed to a size corresponding to the pouring part 142. That is, in the portion where the concrete pouring portion 142 is formed, the lower portions of the diaphragms 112 may be disposed to be spaced apart from the lower surface of the steel box girder body 110 toward the upper side.

Meanwhile, in FIGS. 4 to 6, cross-sections of the upper and lower flange open type box girders 100 in the positive moment section PM, the non-opening area F, and the positive moment section NM are shown, respectively.

Referring to FIG. 4, in the positive moment section PM, the upper opening 122 is provided in the upper flange 120, but the lower opening 132 is not provided in the lower flange 130. At this time, in the positive moment section PM, a portion disposed below the neutral axis of the steel box girder body 110 is tensioned, and a portion disposed above the neutral axis of the steel box girder body 110 is compressed. Therefore, it is preferable that the lower flange 130 is not provided with the lower opening 132 to sufficiently respond to the tensile stress in the positive moment section PM. On the other hand, the upper flange 120 does not need to respond to the compressive stress because the bridge slab 30 supports the compressive stress in the positive moment section PM.

As described above, since the upper opening 122 is formed in the upper flange 120 in the positive moment section PM, the amount of steel used in the manufacture of the upper flange 120 is remarkably dependent on the size of the upper opening 122. It can be reduced, and accordingly, the steel cost of the upper and lower flanged open box girder 100 can be reduced, thereby improving economic efficiency.

Referring to FIG. 5, in the non-opening region F, the upper opening 122 is not provided in the upper flange 120 and the lower opening 132 is not provided in the lower flange 130. At this time, in the non-opening region F, both the tensile stress and the compressive stress may be provided to the upper flange 120 and the lower flange 130 because the positive moment section PM and the negative moment section NM are alternately. . Therefore, both the upper opening 122 and the lower opening 132 are provided so that the upper flange 120 and the lower flange 130 respond to both tensile stress and compressive stress in the positive moment section PM and the negative moment section NM. It is desirable not to be provided.

As described above, since the upper opening 122 and the lower opening 132 are not formed in both the upper flange 120 and the lower flange 130, the positive moment section (PM) and the negative moment section (NM) are alternating. It can respond smoothly to both the positive moment and the positive moment.

Referring to FIG. 6, in the negative moment section NM, the lower opening 132 is provided in the lower flange 130, but the upper opening 122 is not provided in the upper flange 120. At this time, in the negative moment section (NM), a portion disposed below the neutral axis of the steel box girder body 110 is compressed, and a portion disposed above the neutral axis of the steel box girder body 110 is tensioned. Accordingly, the upper flange 120 is preferably not provided with the upper opening 122 to sufficiently respond to the tensile stress in the negative moment section (NM). On the other hand, the lower flange 130 does not need to cope with the compressive stress since the point support 140 supports the compressive stress in the negative moment section NM.

As described above, since the lower opening 132 is formed in the lower flange 130 in the negative moment section NM, the amount of steel used in the manufacture of the lower flange 130 is significantly dependent on the size of the lower opening 132. It can be reduced, and accordingly, the steel cost of the upper and lower flanged open box girder 100 can be reduced, thereby improving economic efficiency.

The continuous bridge 10 using the upper and lower flanged open box girder 100 according to an embodiment of the present invention configured as described above is analyzed by a design method using nonlinear inelastic analysis as follows.

First of all, the design method using nonlinear inelastic analysis generally follows the load resistance coefficient design method. The load and resistance factor design (LRFD), derived based on nonlinear inelastic analysis, uses the resistance factor and load factor based on the theory of structural reliability, and the strength and various limit states of detailed elements such as structural members or ultimate strength. It is a design method that does not exceed the ultimate strength or limit state strength in consideration of Therefore, it is possible to perform performance-based design using nonlinear inelastic analysis for the entire structure.

As a result of performing the nonlinear inelastic analysis using the finite element model as described above, the continuous bridge 10 using the upper and lower flanged open box girders 100 used the nonlinear inelastic analysis design to reduce the amount of steel used in the optimal cross-section through a normal steel box. Compared with the bridge, it was analyzed that it could be reduced by 22.5% and the amount of deflection decreased by 7.8%.

Specifically, in the case of the continuous bridge 10 using the upper and lower flange open box girder 100, there is a disadvantage in that the cross section of the main member increases and the amount of steel material increases, but due to the formation of the upper opening 122 and the lower opening 132 It is analyzed that the effect of reducing the amount of steel used is greater, and the amount of deflection of the continuous bridge 10 is also analyzed.

As described above, in the embodiments of the present invention, specific matters such as specific components, etc., and limited embodiments and drawings have been described, but this is only provided to help a more general understanding of the present invention, and the present invention is limited to the above embodiments. It is not, and a person of ordinary skill in the field to which the present invention belongs can make various modifications and variations from this description. Accordingly, the spirit of the present invention is limited to the described embodiments and should not be defined, and all things equivalent or equivalent to the claims as well as the claims to be described later belong to the scope of the inventive concept.

10: continuous bridge
20: point site
30: bridge slab
100: upper and lower flange open type box girder
110: steel box girder body
120: upper flange
122: upper opening
130: lower flange
132: lower opening
140: point support
PM: Positive moment section
NM: Moment section
F: non-open area

Claims (10)

A steel box girder body in which a bridge slab is provided on the upper surface and disposed so that the lower surface is seated at a point such as a pier; An upper flange forming an upper surface of the steel box girder body and having an upper opening at a position corresponding to a positive moment section of the steel box girder body; A lower flange forming a lower surface of the steel box girder body and having a lower opening at a position corresponding to the negative moment section of the steel box girder body; And a point support part provided on the lower flange so that the concrete material is poured into the lower opening and seated at the point portion,
The steel box girder body, the upper flange, and the lower flange are formed of steel, and the bridge slab and the branch support are formed of concrete,
The upper flange does not form the upper opening in the negative moment section to support the tensile stress applied to the negative moment section of the steel box girder body, and the upper opening has a positive moment to reduce the amount of steel used in the upper flange. It is formed long along the longitudinal direction of the steel box girder body in the section,
The lower flange does not form the lower opening in the positive moment section so as to support the tensile stress applied to the positive moment section of the steel box girder body, and the lower opening is negatively formed to reduce the amount of steel used in the lower flange. It is formed long along the longitudinal direction of the steel box girder body in the section,
The bridge slab is provided on the upper side of the upper flange to support a compressive stress applied to a positive moment section of the steel box girder body,
The branch support part is provided in the lower opening to support a compressive stress applied to the negative moment section of the steel box girder body, and is formed on the upper surface of the lower flange so as to be accommodated inside the steel box girder body,
An upper and lower flange open type box girder, characterized in that a concrete pouring portion for pouring the point support portion is provided in the interior of the steel box girder body below the portion corresponding to the negative moment section.
delete The method of claim 1,
In the upper flange and the lower flange, a non-opening region in which neither the upper opening and the lower opening are formed is formed at a boundary between the positive moment section and the negative moment section,
The upper and lower openings and the upper and lower openings, the upper and lower flange open type box girder, characterized in that arranged at a position spaced apart from the boundary between the positive moment section and the negative moment section.
The method of claim 1,
The upper and lower flanges open type box girder, characterized in that round portions are provided at both ends of the upper opening and the lower opening in a semicircular shape or an arc shape having a constant curvature.
The method of claim 4,
The diameter of the round portion is provided to have a length ratio of 0.60 to 0.80 with respect to the width of the upper flange and the lower flange, the upper and lower flange open type box girder.
delete The method of claim 1,
The branch support and the bridge slab are provided with a concrete structure,
The upper and lower flange open-type box girder, characterized in that the support portion is formed thicker than the bridge slab.
The method of claim 1,
A plurality of negative moment sections are formed in the steel box girder body,
The upper and lower flange open-type box girder, characterized in that the point support is provided at positions corresponding to the negative moment sections.
delete A continuous bridge constructed by using the upper and lower flange open type box girders according to any one of claims 1, 3, 4, 7 or 8.

Images