JP2013023975A - Bridge girder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bridge girder enabling the inclination angle of a cable to be increased and capable of suppressing enlargement of a girder cross section in the vicinity of a fulcrum part.SOLUTION: A bridge girder 1 includes an upper floor slab 11 and a lower floor slab 12 formed of reinforced concrete and a pair of webs 13 connecting the upper floor slab 11 and the lower floor slab 12 to each other, exhibits a box-shaped cross-sectional shape, and has a column head construction part supported by a bridge footing in the vicinity of both ends in a bridge axial direction, with the lower floor slab 12 being supported by cables 21 to 24 diagonally stretched from the column head construction part to its inner space 1i. In the bridge girder 1, the lower floor slab 12 is configured so as to comprise a floor slab part 12a, a pair of thickness increased parts 12b extending downward along both side parts of the floor slab part 12a, and cable anchor parts 12d, the cables 21 to 24 passing through the floor slab part 12a, lower ends thereof being anchored in the cable anchor parts 12d.

Description

  The present invention relates to a bridge girder such as a road bridge and a railway bridge, and in particular, an upper floor slab and a lower floor slab made of reinforced concrete, and a pair of webs that form a box-shaped cross-section by connecting the upper floor slab and the lower floor slab. It relates to the provided bridge girder.

  As a bridge girder having the above-described configuration, a concrete / steel composite truss bridge (see Patent Document 1) in which the web is composed of diagonal members made of steel pipes, and the bridge shaft with the web facing from the middle in the height direction toward the upper side and the lower side. There are known a plate member made of a steel plate or concrete plate whose direction length gradually increases (see Patent Document 2), a web member made of a corrugated steel plate (see Patent Document 3), and the like.

  In these bridge girders, as shown in FIG. 7, the upper floor slab 111 and the lower floor slab 112 are provided with a thickened portion projecting inward of the cross section of the bridge girder, that is, the upper floor slab 111 is provided with a thickened portion 111b projecting downward. Is formed with a thickened portion 112b protruding upward, thereby increasing the bonding strength between the upper floor slab 111 and the lower floor slab 112 and the web 113.

  Recently, in the bridge girder 101 having such a box-shaped cross-sectional shape, as shown in FIG. 8, cables 121 to 124 are provided obliquely in the internal space 101 i of the bridge girder 101 to reduce the shearing force. There are also those that support the lower floor slab 112 by fixing the lower ends of .about.124 to the lower floor slab 12 and applying tension.

Japanese Patent No. 4154099 Japanese Patent No. 4005774 Japanese Patent No. 4073746

  Here, in the bridge girder shown in Patent Documents 1 to 3, when the cables 121 to 124 are provided in the internal space of the bridge girder, the thickened portion 112b on the upper surface of the lower floor slab 112 is formed as shown in FIGS. On the inner side, a deflection part 112c for changing the installation direction of the cables 121 to 124 in parallel with the lower floor slab 112, and a cable for fixing the ends of the cables 121 to 124 extending in parallel with the lower floor slab 112 A fixing unit 112d. However, it is difficult to increase the inclination angle of the cable because a force in the direction of separating from the lower floor slab 112 is applied to the deflecting portion 112c according to the installation angle of the cables 121 to 124. Moreover, since the length of the lower floor slab part required to fix one cable becomes long, it is difficult to increase the number of cables installed. For this reason, it is not possible to effectively load the cables 121 to 124 with a shearing force, and it is necessary to increase the height of the bridge girder 101 in the vicinity of the fulcrum portion of the bridge girder 101 to which a large shearing force is applied.

  The present invention has been made in view of such a background, and its main object is to provide a bridge girder that can suppress the enlargement of the cross section of the bridge girder near the fulcrum by increasing the inclination angle of the cable. To do.

  In order to solve the above problems, the present invention provides a box comprising an upper floor slab (11) and a lower floor slab (12) made of reinforced concrete, and a pair of webs (13) connecting the upper floor slab and the lower floor slab. Cable having a fulcrum (1a) supported by a pier or an abutment in the vicinity of both ends in the bridge axis direction, and obliquely stretched from the fulcrum to the internal space (1i) (21 to 21) 24) A bridge girder (1) on which the lower floor slab is supported, wherein the lower floor slab includes a floor slab portion (12a) and a pair of members extending downward along both sides of the floor slab portion. The cable includes a thickened part (12b) and a cable fixing part (12d) provided inside the thickened part, and the cable penetrates the floor slab part and the lower end thereof is fixed by the cable fixing part. Configure as follows.

  According to the present invention, the cable is directly fixed without providing a deflecting portion that changes the installation direction of the cable by passing the cable through the floor slab portion of the lower floor slab and fixing it at the cable fixing portion. it can. Therefore, the inclination angle can be increased and the shearing force that can be borne by the cable can be increased, the length of the floor slab portion required for fixing the cable can be shortened, and the shearing force can be effectively borne by the cable. Therefore, the enlargement of the bridge girder cross section in the vicinity of the fulcrum portion can be suppressed.

  In addition, according to one aspect of the present invention, the cable may be configured such that the lower portion exhibits a linear shape while being fixed by the cable fixing portion. By adopting such a configuration, the tensile stress can be directly and efficiently introduced into the cable. Further, since the structure of the lower floor slab is simplified, manufacture (construction) is facilitated.

  Further, according to one aspect of the present invention, the floor slab portion may be formed with a through hole (15) for inspecting the cable fixing portion. By adopting such a configuration, it becomes possible to inspect the fixing part by inserting an inspection tool such as a CCD camera into the through hole, and the inspection work of the fixing part located on the lower surface side of the lower floor slab is facilitated. can do.

  Further, according to one aspect of the present invention, the web includes a plurality of web members (14) arranged in the bridge axis direction so as to be spaced apart from each other on the upper surface (12u) of the floor slab portion. And a drainage gradient is provided on the upper surface of the floor slab portion toward the plate-like member. By setting it as such a structure, weight reduction of a web can be achieved. In addition, because there is a gap between the plate-like members, rainwater and the like enter the interior space of the bridge girder, but the water that has entered the interior is drained to the outside by providing a drainage gradient on the upper surface of the floor slab. Is possible.

  Further, according to one aspect of the present invention, the web member is a plate-like member formed such that the length in the bridge axis direction gradually increases from the middle in the height direction toward the upper side and the lower side ( 14). Examples of the plate-like member include those made of a steel plate, a combination of a steel plate and concrete, and a concrete plate into which prestress is introduced, as disclosed in Patent Document 2. By setting it as such a structure, the web member which can resist a compressive force and a tensile force effectively is realizable.

  According to another aspect of the present invention, the plurality of web members can have the same height dimension. By setting it as such a structure, manufacture and handling of a web member can be made easy.

  Moreover, according to one side of this invention, it can be set as the structure where the thickness of the said floor slab part is larger than the center part of a bridge axis direction in the vicinity of the said fulcrum part. By adopting such a configuration, even if the thickness of the web member (dimension in the direction perpendicular to the bridge axis in plan view) is made constant, the shear strength near the bridge girder fulcrum is increased so that the center part of the bridge girder It is possible to prevent the cross-sectional dimension of the web member from becoming unnecessarily large, thereby preventing the weight of the bridge girder from being increased.

  As described above, according to the present invention, it is possible to provide a bridge girder that can increase the inclination angle of the cable and increase the number of cables installed and can suppress an increase in the cross-section of the bridge girder near the fulcrum portion.

Side view of a bridge girder according to the present invention 1 is a cross-sectional view taken along line II-II in FIG. Main part longitudinal cross-sectional view along the III-III line in FIG. Cross-sectional view taken along line IV-IV in FIG. Cross-sectional view taken along line VV in FIG. Cross-sectional view taken along line VI-VI in FIG. Cross-sectional view of a bridge girder according to the prior art Longitudinal sectional view taken along line VIII-VIII of the bridge girder shown in FIG. Cross-sectional view taken along line IX-IX in FIG.

  Hereinafter, an embodiment of a bridge girder 1 according to the present invention will be described in detail with reference to the drawings.

  As shown in FIG. 1, the bridge girder 1 can be used as a road bridge or a railway bridge, and is a continuous girder that is bridged between a plurality of piers 2 or abutments (not shown). In FIG. 1, only a central portion of two consecutive spans from the center C between the centers (spans) of the pier 2 to the center C between the centers of adjacent piers 2 is omitted. Here, the bridge girder 1 is erected by the overhanging construction method, and the column head construction part 1a (fulcrum part) supported by the pier 2 via the support 3, and the overhang extending from the column head construction part 1a in both directions of the bridge axis. It is comprised from the construction part 1b and the connection part 1c which connects the overhang | projection construction part 1b between the adjacent piers 2.

  As shown in FIG. 2, the bridge girder 1 is made of reinforced concrete and is arranged substantially horizontally to form a roadbed, a lower floor slab 12 arranged substantially parallel to the lower side, and an upper floor slab 11. And a pair of webs 13 connecting the lower floor slab 12 and a box-shaped cross-sectional shape having an internal space 1i. Here, the width dimension of the upper floor slab 11 is larger than the width dimension of the lower floor slab 12, and the upper floor has a slight inclination angle so that the pair of webs 13 opens upward from the side edges of the lower floor slab 12. The plate 11 is formed, and the upper floor plate 11 is formed with an overhanging portion 11 a that protrudes further laterally from the joint portion with the web 13.

  Here, the upper floor slab 11 is constructed of cast-in-place concrete, and at each joint portion of the upper floor slab 11 with the web 13, a thickened portion 11b that protrudes downward and extends in the bridge axis direction is formed. The lower floor slab 12 is also constructed here with cast-in-place concrete. The lower floor slab 12 includes a flat floor slab portion 12a disposed substantially horizontally and a pair of thickened portions 12b projecting downward along both side edges of the floor slab portion 12a. That is, the thickened portion 12b is provided in a manner of projecting downward along the bridge axis direction at each joint portion between the floor slab portion 12a and the web 13. In addition, the lower floor slab 12 has transverse beams 12c that connect the pair of thickened portions 12b at appropriate positions in the bridge axis direction. 3, 4, and 6, the cross beam 12 c and the floor slab portion 12 a are shown by different hatching. However, the cross beam 12 c is made of concrete placed at the same time by the bottom surface and the thickened portion of the floor slab portion 12 a. It is integrally formed on the side surface of 12b.

  Each web 13 is composed of a plurality of plate-like members 14 made of precast concrete arranged in a line in the bridge axis direction. The plate-like member 14 has a butterfly shape whose length in the bridge axis direction gradually increases from the middle in the height direction toward the upper side and the lower side, and all the plate-like members 14 have the same shape. The dimensions are the same. Since the plate-like member 14 is known as disclosed in Japanese Patent No. 4,005,774, a detailed description thereof will be omitted, but prestress is appropriately introduced in an oblique direction at a portion to which a tensile load is applied. The structure has a large proof strength against the compressive force and tensile force applied so as to cross the X shape. And since all the plate-shaped members 14 are made into the same shape and the same dimension, manufacture and handling of the plate-shaped member 14 become easy.

  These plate-like members 14 are arranged at a predetermined center interval so as to be spaced apart from each other on the joint surface (upper surface 12 u) of the lower floor slab 12, the lower end enters the lower floor slab 12, and the upper end is the upper floor slab 11. In this state, the lower floor slab 12 and the upper floor slab 11 are integrally joined with the concrete. Although not shown, the upper and lower ends of the plate-like member 14 are formed with a large number of reinforcing bars or stud gibbles at the time of precast production, and these are embedded in concrete so that the plate-like member 14 and the lower floor The bonding strength between the plate 12 and the upper floor plate 11 is improved.

  Further, on the upper surface 12u of the lower floor slab 12, as shown by an arrow in the drawing, here, a drainage gradient of about 1% descending from the center in the direction perpendicular to the bridge axis of the lower floor slab 12 toward both sides. Is provided. Therefore, even if rainwater or the like enters the internal space 1 i from between the plate-like members 14, the entered water flows to the side edge of the lower floor slab 12 due to the drainage gradient and is drained to the outside through the gap between the plate-like members 14. The

  As shown in FIGS. 3 and 4, the internal space 1 i of the bridge girder 1 extends obliquely downward toward the connecting portion 1 c (center C between the piers 2) with the pillar head construction portion 1 a as the highest portion. A plurality of cables 21 to 24 extending through the floor slab portion 12a of the floor slab 12 to reach the cross beam 12c are stretched. These cables 21 to 24 are arranged symmetrically on the right and left sides of the cross section in such a manner that the lower ends thereof are different in the bridge axis direction, and both ends (only one end side is shown in FIG. 3) are transverse beams. 12c is fixed in the vicinity of the end of the bridge axis perpendicular direction. That is, both ends of the horizontal beam 12c are cable fixing portions 12d for the cables 21 to 24.

  When these cables 21 to 24 are fixed by the cable fixing portion 12d, the lower portion extending from the end face of the pillar head construction portion 1a, that is, the portion extending into the internal space 1i, the lower floor slab 12 The portions extending inside the floor slab portion 12a and the cross beam 12c are linear, and the lower end is fixed to the cable fixing portion 12d in this state. In the floor slab portion 12a, the inspection holes 15 for checking the fixing state of the cables 21 to 24 by the cable fixing portion 12d are located closer to the connecting portion 1c than the cable fixing portions 12d (see FIGS. 2 and 3). Is formed so as to penetrate the floor slab portion 12a, and an inspector in the internal space 1i can inspect by inserting a CCD camera or the like into the inspection hole 15.

  As shown in FIGS. 5 and 6, the three cables 21 to 23 whose lower ends are fixed toward the connecting portion 1c are stretched at the same position in the direction perpendicular to the bridge axis immediately above the cable fixing portion 12d. The column head construction portion 1a is also offset from each other in the vertical direction. On the other hand, the cable 24 whose lower end is fixed closest to the pillar head construction portion 1a is fixed at the same position as the other cables 21 to 23 in the direction perpendicular to the bridge axis, but the upper part is the other cables 21 to 23. It is arranged so as to be closer to the outside (side) than that, that is, to be slightly inclined with respect to the vertical direction in a sectional view. Therefore, this cable 24 can cross | intersect with the other cables 21-23 by a side view, and this cable 24 can be stretched by a big inclination angle by passing the highest possible position in the column head construction part 1a. Yes.

  When the overhang construction part 1b is extended by the overhang construction method and a predetermined concrete strength is developed, these cables 21 to 24 are strained with a jack or the like through a steel wire insertion hole (not shown) formed in the column head construction part 1a. By fixing both ends to the cable fixing unit 12d in the state, the lower floor slab 12 and the like are sequentially stretched according to the progress. Thus, the tensile prestress is introduced into the cables 21 to 24 installed obliquely, so that the proof strength of the bridge girder 1 against the shearing force and bending force is improved.

  In particular, since the inclination angle of the cable 24 fixed at the lower end closest to the column head construction portion 1a of the bridge girder 1 is large, the shear strength in the vicinity of the column head construction portion 1a of the bridge girder 1 to which a large shear force is applied is greatly increased. It has improved. Further, since the lower ends of the cables 21 to 24 can be fixed by the cable fixing portion 12d provided in the short range in the bridge axis direction of the floor slab portion 12a, more cables 21 to 24 can be installed. As a result, the shear strength of the bridge girder 1 is improved. Furthermore, since the cables 21 to 24 have a configuration in which the lower portion is linear in a state where the cables 21 to 24 are fixed by the cable fixing portion 12d, it is possible to directly and efficiently introduce the tensile stress to the cables 21 to 24. In addition, the structure of the lower floor slab 12 is simplified, and construction such as mold assembly is facilitated. In the construction of the lower floor slab 12, since the thickened portion 12 b and the cross beam 12 c are protruded downward, there is no need for a floating formwork that is required in the conventional upward protruding manner. The construction is also easy.

  The plate-like members 14 formed with the same dimensions are embedded in the upper floor slab 11 and the lower floor slab 12 with the same embedding length, and the height of the internal space 1i of the bridge girder 1 is constant. . On the other hand, in the lower floor slab 12, the thickness of the floor slab portion 12 a is located at the other portion, specifically, the center C of the span in the bridge axis direction in the portion of the overhang construction portion 1 b close to the pillar head construction portion 1 a. It is larger than the connecting portion 1c. The shearing force of the bridge girder 1 increases as it approaches the column head construction part 1a. However, the shear strength in the vicinity of the column head construction part 1a of the bridge girder 1 is increased by the plurality of cables 21 to 24 and this configuration. As described above, by increasing the thickness of the floor slab portion 12a in the vicinity of the column head construction portion 1a of the bridge girder 1, it is possible to reduce the thickness of the plate-like member 14 formed in the same shape and the same size. Is lighter.

  The description of the specific embodiments is finished as described above, but the present invention is not limited to these embodiments, and can be changed as appropriate without departing from the spirit of the present invention. For example, in the above embodiment, the bridge girder 1 is a continuous girder that is continuous between a plurality of piers 2, but may be a bridge girder that is independent between adjacent piers 2. Moreover, although the bridge girder 1 of the said embodiment is supported by the pier 2 via the support 3, the form formed integrally with the pier 2 and exhibiting a ramen structure may be sufficient. Furthermore, in the said embodiment, although the several plate-shaped member 14 shape | molded by precast comprises the web 13, the web 13 is constructed | assembled into a pair of wall shape or several plate shape with a cast-in-place concrete, patent document The web 13 is composed of a plurality of diagonal members made of steel pipes used in a composite truss bridge as disclosed in FIG. 1, or the web 13 is composed of a corrugated steel plate as disclosed in Patent Document 3. Also good. Moreover, all the components of the bridge girder 1 according to the present invention shown in the above embodiment are not necessarily essential, and can be appropriately selected as long as they do not depart from the gist of the present invention.

1 Bridge girder 1a Column head construction part (fulcrum part)
1i Internal space 2 Pier 11 Upper floor slab 12 Lower floor slab 12a Floor slab 12b Thickening part 12c Cross beam 12d Cable fixing part 12u Upper surface 13 Web 14 Plate member (web member)
15 Inspection hole (through hole)
21, 22, 23, 24 Cable

Claims (7)

A fulcrum supported by a bridge pier or abutment in the vicinity of both ends in the bridge axis direction, having a box-shaped cross section comprising an upper floor slab and a lower floor slab made of reinforced concrete, and a pair of webs connecting the upper floor slab and the lower floor slab. A bridge girder that has a portion and is supported by the lower floor slab by a cable that is obliquely stretched from the fulcrum to the internal space,
The lower floor slab includes a floor slab part, a pair of thickened parts protruding downward along both side parts of the floor slab part, and a cable fixing part provided inside the thickened part,
A bridge girder characterized in that the cable penetrates the floor slab portion and the lower end thereof is fixed by the cable fixing portion.   2. The bridge girder according to claim 1, wherein the cable has a linear lower portion in a state where the cable is fixed by the cable fixing portion.   The bridge girder according to claim 1 or 2, wherein a through hole for checking the cable fixing portion is formed in the floor slab portion. The web is a plurality of web members arranged in the bridge axis direction so as to be spaced apart from each other on the upper surface of the floor slab part,
The bridge girder according to any one of claims 1 to 3, wherein a drainage gradient is provided on an upper surface of the floor slab portion toward the plate-like member.   5. The plate member according to claim 4, wherein the web member is a plate-like member formed such that the length in the bridge axis direction gradually increases from the middle in the height direction toward the upper side and the lower side. The listed bridge girder.   The bridge girder according to claim 4 or 5, wherein the plurality of web members have the same height dimension.   The bridge girder according to claim 6, wherein a thickness of the floor slab portion is larger than a central portion in a bridge axis direction at the fulcrum portion.

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