JP2008111309A - Method of manufacturing composite girder of steel and concrete for bridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a composite girder of steel and concrete for a bridge, capable of easily adjusting stress in a factory, without requiring a device and an PC steel material for introducing prestress, by reducing the structural height. <P>SOLUTION: This composite girder 24 is manufactured by driving and hardening concrete 23 in an upper end part, in a state of being supported by a support 11 in four places in total of both end parts of a manufactured steel girder 20 and two places of an intermediate part. The dead load bending moment of a steel member and the concrete opposing by the steel girder 20, is reduced more than a two-point support state in a four-point support state of the composite girder 24 in manufacture. When installing this composite girder 24, since a concrete member opposes in the steel girder 20 and the concrete 23 by contributing to opposition to the bending moment by being supported at two points of both end parts, the dead load bending moment of the steel member opposed to the concrete member and the concrete member is reduced, and a cross section of the concrete 23 can be reduced. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a composite girder having a composite structure of steel and concrete used for a bridge girder suitable for being spanned between small and medium span lengths.

River bridges that cross rivers and canyons, and various bridges such as viaducts that are installed to avoid planar crossings with roads and railways are subject to constraints such as topography, river obstruction rate, crossing structures, and routes. May have to be lowered. For example, Figure 8 shows one example of a river bridge to be laid across the river R, the river bridge 1, the short span of the portion straddling the long span portion D _L and the banks S portion across the river R It is passed over to the D _S. The river bridge shown in FIG. 8, the structure of the truss bridge 2 is employed in the long span part D _L, simple Ketakyo 3 are the adopted structure in the short span portion D _S.

The short span portion Ds becomes a part to be connected to the mounting road 4 to connect this river bridge 1, this short span portion D _S is one span length than the long span part D _L is small. The bridge passed over this short span portion D _S, the restriction of the road surface and Hashimoto space mounting road 4, if there is no structural height restrictions, simple synthesis girder bridge or simple non-synthetic girder bridge, structure height In general, simple steel floor slab bridges or composite floor slab bridges are used. That is, the simple girder bridge 3 that is an upper structure that becomes a bridge girder via a support 6 is constructed in a lower structure 5 that includes a foundation 5a and a housing 5b.

Figure 7 shows a steel I girder schematic structure employed in the short span portion D _S of this type, the main spar 7, is a reinforced by such pair傾構8 and load distribution crossbeam 9 structure ing. The main girder 7 includes a steel web 7a responsible for the force against the shearing force, an upper flange 7b disposed on the upper end portion of the steel web 7a and responsible for a force resisting the bending moment, and a lower portion disposed on the lower end portion. The flange 7c is combined to form an I-shaped cross-sectional structure. In addition, it connects with the floor slab not shown installed on this steel I girder with a slab anchor, and it combines with the non-synthetic girder which is not considered in the cross section of the design by the stud gibber etc. There are composite digits to do.

  By the way, the applicant of the present application has proposed a composite girder structure of steel and concrete capable of reducing the construction cost by reducing the structural height and shortening the construction period (see Patent Document 1). This composite girder is provided with a structure having a steel lower flange at the lower end of the steel web constituting the main girder of the bridge girder and a reinforced concrete upper flange at the upper end of the steel web.

  FIG. 3 is a diagram for explaining an example of a process of manufacturing the composite girder, and FIG. 4 is a diagram showing a bending moment distribution and stress in each process state in which the manufactured composite girder is applied to the bridge girder. That is, FIG. 3 shows a manufacturing method for completing the composite girder 13 by driving concrete 12 into the upper part of the manufactured steel girder 11. The steel girder 11 is placed on the flat surface 14 when the concrete 12 is driven. . Fig. 4 (a) shows the state where this composite girder 13 is installed on the support 15 as a bridge girder. The lower part of the figure shows the bending moment shown by the curve 13a, and the right side shows the stress level at the part where the bending moment is maximum. It is. A compressive stress Sp is generated on the upper side of the composite girder 13, and a tensile stress St is generated on the lower side. When a bridge work such as pavement is constructed on the surface of this bridge girder, as shown in FIG. 4 (b), a bending moment 13b is generated, and cumulative stresses Sp and St are generated. Further, a state in which a live load is loaded by the passage of a vehicle or the like is shown in FIG. 4C, a bending moment 13c is generated, the cumulative stresses Sp and St are increased, and the cross-sectional force that is opposed by the concrete 12 is increased. . For this reason, it becomes necessary to enlarge the cross section, which is an obstacle to reducing the height of the beam.

  FIG. 5 shows a state in which the end of the steel girder 11 is supported by the support 16 and the composite girder 17 is completed by driving concrete 12 into the upper part of the steel girder 11. The steel girder 11 is supported. In this state, a bending moment 17a is generated by its own weight as shown in the lower part of FIG. 5B, and a compressive stress level Sp and a tensile stress level St are generated as shown on the right side. In this case, only the steel beam 11 opposes the bending moment 17a. In the state of FIG. 6A in which the composite girder 17 is installed as a bridge girder on the support 15, the steel girder 11 alone is in opposition to the bending moment 17a, and the concrete 12 hardly contributes. Further, in FIG. 6B, the bending moment 17b is generated in the state where the bridge work is performed, and the compressive stress Sp is generated in the concrete 12 in the cumulative stress level Sp and St generated in the steel beam 11, and the steel beam 11 is The tensile stress St is added. FIG. 5 (c) shows a state in which a live load is loaded. A bending moment 17 c is generated, and a larger tensile stress St is generated in the steel beam 11. In the composite girder 17, the concrete 12 does not sufficiently contribute as a member that resists the bending moment 17c, and does not sufficiently function as the structure of the composite girder 1.

  On the other hand, as a composite girder that generates stress sufficiently against the bending moment, a steel girder having an I cross section is subjected to a load that causes bending deformation, and concrete is driven around the tension side flange to be hardened. A pre-beam composite girder in which compressive pre-stress is introduced into the concrete by removing the load applied to the girder, a post-tension system in which PC steel is placed on the tension part of the concrete member, and a PC in the compression part of the concrete member A composite girder is manufactured by a so-called bi-pres- sion method in which steel materials are arranged and pre-stressed in combination with a post-compression method for compressing the steel materials. Further, for example, in Patent Document 2, as a method of manufacturing a prestressed composite girder, both ends of a steel girder having upper and lower flanges are supported, and fixing tools are attached to both ends of the upper flange of the steel girder. By applying a predetermined tensile force to the out cable stretched on the steel girder, a pre-deflection load is applied to the steel girder, and then, with this pre-deflection load applied, the concrete along the lower flange on the steel girder's tensile stress side And, after the concrete is hardened, the application of the pre-deflection load is released and prestress is introduced into the lower flange side concrete.

Japanese Patent Application No. 2005-302669 Japanese Patent Publication No. 4-26025

  However, as described above, the steel girder is placed on the tension side, and the concrete is placed on the compression side to counter the bending moment. When this is precast in a factory or the like, the dead load from the synthesis of the manufacturing process, The live load and the load in either case will be countered by the concrete, and it is necessary to increase the compressive force, increase the cross section, and increase the thickness of the concrete. For this reason, reducing the digit height is hindered.

  In addition, as described in Patent Document 2 described above, when pre-stress is introduced using PC steel or the like, the manufacturing cost of the composite girder is increased by requiring an apparatus or a jig for that purpose. .

  Therefore, in the case where the present invention is manufactured by precast, the thickness of the concrete member is adjusted by balancing the bending moment by the steel girder and the concrete member without using a device for introducing prestress. The purpose of the present invention is to provide a method for manufacturing bridge steel and concrete composite girders that can reduce the height of the girder as much as possible.

  As a technical means for achieving the above object, a method for manufacturing a composite girder of steel and concrete for a bridge according to the present invention is manufactured in a method for manufacturing a composite girder having a girder structure by a composite structure of steel and concrete. The steel girder is supported by a support member at both ends of the steel girder and at positions appropriately spaced from the respective end portions, and concrete is driven into the upper part of the steel girder to harden the concrete.

  That is, a composite girder is manufactured by driving concrete into the upper part with the steel girder supported at four points. By supporting at four points, the cross-sectional force due to the pre-dead load at the center of the beam span where the maximum cross-sectional force is generated can be reduced. Concrete is driven in this state. When the completed composite girder is installed as a bridge girder, it is supported at two points on both ends, and the positive bending moment at the center of the span is reduced, and a composite girder with an optimal cross section can be manufactured.

  According to a second aspect of the present invention, there is provided a method for manufacturing a composite girder of steel and concrete for a bridge, wherein the steel girder comprises a steel web and a steel lower flange.

  The steel girder can be a steel I girder or box girder made of I-type steel, but is composed of a steel web and a steel lower flange attached to the lower part of the steel web.

  According to the method of manufacturing a composite girder of steel and concrete for a bridge according to the present invention, a device for loading and removing a load for introducing prestress on the steel girder is not necessary, and reinforcement work such as PC steel is performed. The cross-sectional force can be controlled without the need, and the girder height can be made as small as possible to produce a composite girder with an optimal cross-section at a low cost.

  Moreover, according to the manufacturing method of the bridge steel and concrete composite girder according to the invention of claim 2, the manufacturing cost and the construction cost can be further reduced.

  In addition, when using a steel web for the steel girder and driving concrete into the top, there is a risk of buckling. In such a case, the steel web is reinforced and buckled during the manufacture of the composite girder. Reinforcing means can be applied to counteract. Furthermore, it is preferable that the reinforcing means can be removed when the composite girder is installed.

  Hereinafter, based on the preferred embodiment shown in the drawings, a method for manufacturing a composite girder of steel and concrete for a bridge according to the present invention will be specifically described.

  The manufacturing process is shown in FIG. 1. A steel girder 20 made of I-shaped steel, box girder, steel web, etc. is produced, and the produced steel girder 20 is formed at both ends of the steel girder 20 as shown in FIG. And it is installed in a state where it is supported by the production supports 21a, 21b, 21c, 21d at a total of four places, two places in the middle part. In this state, the bending moment 22 shown in the lower part of FIG. That is, a positive bending moment is generated between the production supports 21b and 21c, between the production supports 21a and 21b, and between the production supports 21c and 21d, and a negative bending moment is generated in the vicinity supported by the production supports 21b and 21c. Further, a compressive stress Sp and a tensile stress St are generated. At this time, the maximum positive bending moment generated at the center of the steel beam 20 is smaller than that in the case of the two-point support shown in FIGS. In addition, it is preferable to set the positions of the production supports 21a to 21d so that the maximum value of the bending moment occurs between the production supports 21b and 21c, and the distance between the production supports 21a and 21b and the distance between the production supports 21b and 21c. It is preferable that the distance between the production supports 21c and 21d is 1: 2 to 2.5: 1. For example, when the steel girder 20 is 23 m, the distance between the production supports 21a and 21b and the distance between the production supports 21c and 21d are 5 m, respectively, and the distance between the production supports 21b and 21c is 13 m.

  Concrete 23 is driven into the upper part of the steel girder 20 supported at four points of the production supports 21a, 21b, 21c, and 21d, and the concrete 23 is hardened to complete the composite girder 24. The completed composite girder 24 is carried into the bridge construction site, and is constructed with two points supported by a construction support 25 installed on the pier as shown in FIG. 2 (a). A bending moment 26 generated in the composite girder 24 by two-point support is shown, and a bending moment 22 by the steel girder 20 is also shown. Comparing these, concrete 23 contributes to the bending moment 22 generated in the steel girder 20 as a member that counteracts the increase in the bending moment 26 generated in the composite girder 24. Fig. 2 (b) shows the work after the bridge work, and Fig. 2 (c) shows the condition when the live load is applied. The bending moment 27, the cumulative compressive stress Sp, St and the bending moment 28, respectively. Compressive stresses Sp and St are generated. In any case, since the cross-sectional force due to the pre-synthesis dead load borne by the concrete 23 is small, it can be countered without increasing the cross-section of the concrete 23. Therefore, the digit height can be kept small.

  The steel girder 20 can be a steel I girder, box girder, steel web or the like. When using a steel web and a steel lower flange, there is a risk of buckling when the concrete 23 is driven. For this reason, when the concrete 23 is driven into the steel girder 20 by the steel web and the steel lower flange, it is preferable to take a reinforcing means. For example, angle steel is fixed to the upper end of the steel web with bolts, nuts, adhesive, etc., and concrete 23 is driven in. After the concrete has hardened, this angle steel is removed, or buckled by the formwork when the concrete 23 is driven in. It is preferable to counteract the force.

  According to the manufacturing method of the steel and concrete composite girder of the bridge according to the present invention, the bending moment generated in the bridge girder is efficiently countered by the steel member and the concrete member, thereby reducing the cross section of the concrete member and increasing the girder height. It can be made smaller and is not subject to structural height restrictions, and when precasting this composite girder, it does not require prestressing equipment or PC steel, contributing to the reduction of bridge construction costs. To do.

It is a figure explaining the process of the manufacturing method of the composite girder of steel and concrete of a bridge concerning this invention. It is a figure explaining the bending moment and cross-sectional force at the time of constructing the composite girder manufactured by this method. It is a figure which shows an example of the manufacturing method of the conventional composite girder, and is a figure equivalent to FIG. It is a figure explaining the bending moment cross-sectional force at the time of constructing the composite girder by the manufacturing method shown in FIG. 3, and is a figure equivalent to FIG. It is a figure which shows the other example of the manufacturing method of the conventional composite girder, and is a figure equivalent to FIG. It is a figure explaining the bending moment cross-sectional force at the time of constructing the composite girder by the manufacturing method shown in FIG. 5, and is a figure equivalent to FIG. It is a perspective view explaining the outline of the structure of the conventional steel I girder. It is a figure explaining an example of the bridge structure of the length of a medium and small branch.

Explanation of symbols

20 steel girders
21a, 21b, 21c, 21d Production support
22 Bending moment
23 Concrete
24 composite digits
25 Construction support
26 Bending moment
27 Bending moment
28 Bending moment Sp Compressive stress St Tensile stress

Claims (2)

In a composite girder manufacturing method having a girder structure with a composite structure of steel and concrete,
It is supported by the support members at both ends of the manufactured steel beam and at positions appropriately spaced from the respective ends,
A method for producing a bridge steel-concrete composite girder, wherein concrete is driven into the upper portion of the steel girder to harden the concrete.   2. The method of manufacturing a composite steel girder of bridge steel and concrete according to claim 1, wherein the steel girder comprises a steel web and a steel lower flange.

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