JP2010101072A - Structure of composite beam, and construction method for composite beam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide structure of a composite beam capable of integrating a steel beam with a concrete floor slab. <P>SOLUTION: This structure of the composite beam 1 is formed of the steel beam 2 provided with a shift stopper 22 on an upper face, and the concrete floor slab 50. The concrete floor slab 50 is formed of precast concrete HPCa parts 3, 3 with an end mounted on the steel beam on the outside of the shift stopper 22, in both side edges of an upper flange 21 of the steel beam, and overhung from both the side edges, a truss reinforcement 4 of a member for connecting the HPCa parts each other, having lower parts of both the end parts 41, 41 embedded into the HPCa parts, and having an upper part projected upwards, and a field driving concrete part 5 driven on the steel beam and the HPCa part to embed the truss reinforcement. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a structure of a composite girder having a composite cross section of steel and concrete used for erection of viaducts and bridges such as roads and railways, and a method for constructing a composite girder.

  Conventionally, viaduct construction using precast concrete members has been carried out for the purpose of shortening the construction period, improving quality, and eliminating restrictions on construction sites (see Patent Documents 1 and 2, etc.).

  For example, in Patent Documents 1 and 2, a half precast floor slab in which the lower half of the floor slab is formed of concrete is used, and the half precast floor slab and Further, a method for constructing a viaduct is disclosed in which the concrete placed on site is integrated therewith.

  Patent Document 3 discloses a composite floor slab in which concrete is placed on a steel plate in the field, and a plurality of U-shaped bolts are provided on the steel plate in order to integrate the steel plate and the concrete. Is disclosed.

Furthermore, Patent Document 4 discloses that a loop joint bar is used for joining adjacent half precast slabs.
Japanese Patent No. 3323463 Japanese Patent No. 3176309 Japanese Patent No. 3950757 Japanese Patent No. 3590302

  However, the above-described conventional viaduct construction method is an invention about the integration of the half precast member and the concrete cast thereon, or the integration of the steel plate and the concrete cast thereon, There is no disclosure of an invention that integrates a steel girder and a concrete slab formed thereon.

  On the other hand, even when a concrete slab is constructed on a steel girder, it is desired to use a precast concrete member for the purpose of eliminating construction restrictions, shortening the construction period, and improving quality.

  Therefore, an object of the present invention is to provide a composite girder structure in which a steel girder part and a concrete floor slab can be integrated, and a synthetic girder construction method.

  In order to achieve the above object, the structure of a composite girder according to the present invention is a structure of a composite girder formed by a steel girder portion having a top surface provided with a stopper and a concrete floor slab. A precast overhang portion made of precast concrete that is placed on the steel girder portion outside the slip stopper at both side edges of the upper surface of the girder portion and projects from the both side edges, and the precast A member that connects between the overhanging portions, the lower part of both ends being embedded in the precast overhanging part and the upper part protruding upward, and the steel girder part and the precast overhanging part The floor slab is formed by a cast-in-place concrete portion that is provided and embeds the connection reinforcing material.

  Here, it is preferable that a distance from the end faces of the both side edges of the steel girder to the stopper disposed closest is set to a predetermined distance or more.

  Moreover, it can also be set as the structure where the attachment piece protruded toward the said steel beam part from the said precast overhang | projection part and the upper surface of the said steel beam part are fastened with a volt | bolt.

  Furthermore, the method for constructing a composite girder according to the present invention is a method for constructing a composite girder formed by a steel girder having a stopper on its upper surface and a concrete floor slab, Forming a floor slab unit by molding a precast overhang comprising a floor and a wall extending above the both ends of the connecting reinforcement longer than the width with concrete; and the wall A step of connecting with a detachable temporary connecting material, a step of lifting the floor slab unit, and placing the precast projecting portions on both side edges of the upper surface of the steel girder, and the temporary connecting material, It is characterized by comprising a step of removing and removing from the wall portion, and a step of placing concrete on the steel girder portion and the precast overhang portion and placing concrete.

  Also, a method for constructing a composite girder formed by a steel girder part provided with a stopper on the upper surface and a concrete floor slab, which is provided at both ends of a connecting reinforcing material longer than the width of the steel girder part A step of forming a floor slab unit by molding a precast overhanging portion with concrete, a step of lifting the floor slab unit and placing the precast overhanging portions on both side edges of the upper surface of the steel girder portion, and , A step of fastening a mounting piece projecting from the precast overhanging portion onto the steel girder portion and an upper surface of the steel girder portion with a bolt, and the steel girder portion and the precast overhanging portion. And a step of placing a reinforcing bar on the part and placing concrete.

  The structure of the composite girder according to the present invention constructed as described above is an upper portion in which the end portion is placed on the steel girder portion and the precast overhang portion projecting therefrom is connected to the precast overhang portion. And a connecting reinforcing material from which the protrusion protrudes. And the slip stopper is provided on the steel girder part.

  For this reason, concrete is continuously filled between the upper surface of the steel girder part, the precast overhanging part, and the connecting reinforcing material, and the composite girder in which the steel girder part and the concrete floor slab are integrated is provided. Can be formed.

  In addition, by setting the distance from the end face of the both side edges of the steel girder to the closest stopper is set to a predetermined distance or more, there is no deviation between the precast overhang and the stopper. It is possible to secure the width of the concrete and to distribute the stress from slippage prevention.

  Furthermore, the joining strength of a precast overhang | projection part and a steel girder part can be raised by setting it as the structure which fastens the attachment piece protruded from the precast overhang | projection part and the upper surface of a steel girder part with a volt | bolt.

  Moreover, in the construction method of the composite girder of the present invention, the precast overhanging portion that overhangs from the steel girder portion is formed of precast concrete, so that support work under the precast overhanging portion at the site can be omitted.

  Furthermore, in the field, since it is possible to place concrete using the steel girder part and the precast overhang part as the lower surface formwork, it is not necessary to install and dismantle the formwork and supporting work on the lower surface side.

  For this reason, even in a site where there is a road or railroad below the precast overhang, there is no restriction on construction due to the possibility of flying and falling, and a composite girder can be easily constructed.

  Moreover, by connecting between the wall portions of the precast overhanging portion with a detachable temporary connecting material, it is possible to resist the force that temporarily acts on the floor slab unit during lifting.

  Furthermore, after the floor slab unit is stabilized by installation or the like, the temporary connecting material can be removed, so that the temporary connecting material does not hinder the work of bar arrangement.

  Moreover, if a precast overhang part is provided with an attachment piece and the steel girder part and the attachment piece are fastened with bolts, the precast overhang part is quickly fixed after being placed on the steel girder part. be able to.

  Furthermore, if the precast overhang | projection part is being fixed to the steel girder part, since the support work at the time of placing concrete can be abbreviate | omitted or reduced, it becomes possible to reduce a construction period and a construction cost. In addition, by this bolt fastening, it is possible to secure the support until the in-situ concrete portion is cured and a predetermined strength is developed.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a cross-sectional view showing the configuration of the structure of the composite beam 1 of the present embodiment. FIG. 2 is a cross-sectional view showing the structure of the viaduct 60 over which the composite girder 1 is bridged.

  First, the structure of the viaduct 60 will be described with reference to FIG. This viaduct 60 is a structure capable of running a train 64 on a railroad at a plurality of levels. The viaduct 60 is supported by a foundation constructed by piles 63,... Constructed in the ground and underground beams 62 connecting the pile heads.

  A portal steel ramen 61 is constructed on the underground beam 62. Here, the case where the upper ramen 66 is further provided on the steel ramen 61 is illustrated.

  This steel ramen 61 includes steel pipe columns 61a,... Standing on an underground beam 62 across a track 67 on which the trains 64,. And the beam 61b.

  And such a steel ramen 61 is provided at intervals in the extending direction of the track 67, and the composite girder 1 is bridged between the steel beams 61b and 61b of the steel ramens 61 and 61.

  In FIG. 2, a platform 65 is installed adjacent to the composite girder 1, and a composite girder 1 </ b> A having a similar structure is bridged on the opposite side across the platform 65. In addition, the composite girder 1B, 1C having the same structure as that of the composite girder 1 and the platform 65 are also bridged on the upper ramen 66.

  As shown in FIG. 1, the composite girder 1 is formed by a steel girder portion 2 having a stopper 22 on its upper surface and a concrete floor slab 50. Further, the floor slab 50 includes an HPCa (half precast concrete) portion 3 and 3 as a precast overhanging portion made of precast concrete that protrudes from both side edges of the upper surface of the steel beam portion 2, and the HPCa portions 3 and 3. Is mainly composed of a truss bar 4 as a connecting reinforcing material that is horizontally mounted on the steel frame, and a cast-in-place concrete part 5 that is placed on the steel girder 2 and the HPCa parts 3 and 3 to embed the truss bar 4. The

  The steel girder 2 includes an upper surface flange 21 and a lower surface flange 25 as upper surfaces arranged in parallel with a space in the vertical direction, webs 24 and 24 connecting between them, and reinforcement disposed in the inside thereof. The unit 26 is mainly configured.

  The upper surface flange 21 is a surface that also serves as a lower frame of the cast-in-place concrete portion 5. In order to integrate the cast-in-place concrete portion 5 and the upper surface flange 21, a plurality of stoppers 22,. 23,... Project upward.

  The slip stopper 22 is a slip stopper member disposed on the most side edge side of the upper surface flange 21, and is attached so that one U-shaped leg portion is placed on the wide flange portion 21a. Moreover, as shown in FIG. 3, the several slip stoppers 22 ... are attached at intervals in the extending | stretching direction of the steel beam part 2. As shown in FIG.

  Further, the studs 23,... Are attached to the center of the upper surface flange 21 and both sides thereof as shown in FIG. 1, and a plurality of studs 23 are spaced in the extending direction of the steel girder 2 as shown in FIG. Studs 23 are attached.

  Further, the widened flange portion 21a projecting outward from the web 24 is formed on the steel girder portion 2 so as to ensure a predetermined distance between the stopper 22 and the end face of the HPCa portion 3. Compared to the case where a floor slab is constructed with only concrete, it is formed to be widened and have a large overhang.

  Further, the HPCa parts 3 and 3 and the truss bars 4 placed between them are manufactured as a floor slab unit 30 in a factory or the like. The HPCa part 3 is formed in a substantially L shape in sectional view by a floor part 31 and a wall part 32 extending upward at a substantially right angle from the side edge.

  The HPCa part 3 is a precast concrete member formed of reinforced concrete, and the main reinforcing bar 34 arranged at the lower part extends to the inside of the other HPCa part 3, and the two HPCa parts 3, 3 are the main reinforcing bar 34. Will be linked.

  Further, similarly to the main reinforcing bar 34 arranged on the floor 31, a reinforcing bar 33 is also arranged on the wall 32, and an end of the reinforcing bar 33 protrudes from the upper part of the wall 32 and is bent into a hook shape. It will be buried inside the wall of the cast concrete part 5.

  Further, the truss bar 4 is disposed above the main reinforcing bar 34. As shown in FIGS. 1 and 7, the truss muscle 4 is a triangle in which an upper chord member 42 and a lower chord member 43, 43 arranged in parallel to the vertices of an isosceles triangle are connected by wave-like lattice stripes 44, 44. It is a truss-shaped rebar member.

  As shown in FIGS. 1 and 3, the lower chord members 43, 43 of the lower portion of the truss bar 4 are embedded in the floor 31 of the HPCa unit 3. A part of 44 protrudes on the floor 31 and is exposed.

  Moreover, since the lower part of the both ends 41 and 41 is each embed | buried under the HPCa parts 3 and 3, the truss reinforcement 4 will connect between the HPa parts 3 and 3 which were separated. That is, as shown in the plan view of FIG. 3, the HPCa parts 3, 3 arranged on both side edges of the steel girder part 2 are a plurality of trusses arranged at intervals in the extending direction of the steel girder part 2. It will be connected by the lines 4,.

  Furthermore, these truss bars 4,... Are almost entirely exposed above the upper surface flange 21, and the upper part is exposed at the HPCa part 3. It will be buried and will function as a reinforcing material.

  Further, a plate-like mounting piece 35 is projected horizontally from the end face of the HPCa part 3 on the steel beam part 2 side (inner side). As shown in FIG. 3, the attachment piece 35 is a plate member having a square shape in plan view, and is provided with a bolt hole 35 a into which a bolt (not shown) is inserted at a substantially center.

  Next, a method for constructing the composite digit 1 of the present embodiment will be described.

  First, in a factory or a production yard, a floor slab unit 30 in which the HPCa portions 3 and 3 are connected by truss bars 4 as shown in FIG. Further, the wall portions 32, 32 of the HPCa portions 3, 3 are connected by a tie rod 7 as a detachable temporary connecting material.

  On the other hand, the steel girder 2 is bridged between the steel ramens 61 and 61 at the site. Then, the HPCa parts 3 and 3 are transported from the factory to the site, lifted by the suspension wire 71, and placed on the upper surface flange 21 of the steel girder part 2.

  Here, since the HPCa portions 3 and 3 are provided at positions outside the displacement stoppers 22 and 22 attached on the most side edge side of the upper surface flange 21, the HPCa portions 3 and 3 are prevented from being displaced with respect to the installation. 22 and 22 do not interfere with each other.

  Further, since the widened flange portions 21 a and 21 a of the upper surface flange 21 are widened up to just below the HPCa portions 3 and 3, the floor slab unit 30 can be placed on the upper surface flange 21.

  Furthermore, since the floor slab unit 30 has a configuration in which the HPCa portions 3 and 3 are connected by truss bars 4,..., The crane used is very light compared with a floor slab whose entire cross section is formed of precast concrete. Can be reduced. Further, if the weight is reduced, handling during transportation and lifting work becomes easy.

  And after mounting the floor slab unit 30 on the steel beam part 2, the attachment pieces 35 and 35 and the upper surface flange 21 are fastened with a volt | bolt (illustration omitted).

  Further, the tie rod 7 connecting the HPCa parts 3 and 3 is removed, and the reinforcing bars 51 for the in-situ concrete part 5 are arranged as shown in FIG.

  Here, as shown to Fig.7 (a), from the both ends of the extending | stretching direction (paper surface orthogonal | vertical direction of FIG. 5) of the steel beam part 2 of the HPCa part 3, another HPCa part 3 arrange | positioned adjacently. A large hook portion 36a and a small hook portion 36b of the joining rebar 36 that are used for joining are projected.

  That is, as shown in FIG. 7B, a large hook portion 36a protruding from one adjacent HPCa portion 3 and a small hook portion 36b protruding from the other HPCa portion 3 are overlapped in a loop shape. The joints are arranged by inserting a plurality of reinforcing bars 36c through the inner space. A joint rubber 37 is interposed between the end faces of the HPCa parts 3 and 3.

  On the other hand, when arranging bars on the HPCa portions 3 and 3 and the upper surface flange 21, as shown in FIGS. 5 and 7B, the reinforcing bars 51 can be easily used by using the truss bars 4,. Can be arranged.

  Furthermore, as shown in FIG. 8, lattice-like mesh streaks 38, 38 are respectively provided on the lower surface side of the HPCa portions 3, 3 installed near the end portion 2a of the steel girder portion 2 at the factory manufacturing stage. The grid mesh streaks 52 are arranged on the upper surface flange 21 before the floor slab unit 30A is suspended.

  By arranging the mesh bars 38 and 52 in this manner, it is possible to suppress the occurrence of cracks due to temperature stress and drying shrinkage in the vicinity of the beam end portion 2a of the steel beam portion 2.

  Then, as shown in FIG. 6, the on-site concrete part 5 is formed by placing concrete with the upper surface flange 21 of the steel girder part 2 and the floor parts 31 and 31 of the HPCa parts 3 and 3 as the lower surface formwork. Build up.

  Further, after the cast-in-place concrete part 5 has a predetermined strength, pedestal concrete, a track, or the like may be provided to finish the floor slab 50 so that the train 64 can travel.

  Next, the structure of the composite beam 1 of this embodiment and the operation of the construction method will be described.

  The structure of the composite girder 1 of the present embodiment configured as described above includes the HPCa parts 3 and 3 made of precast concrete on which the end part is placed on the steel girder part 2 and protrudes therefrom, and the HPCa part thereof. It has truss bars 4,... That connect the parts 3 and 3 and project from the upper part.

  Further, the top flange 21 of the steel girder 2 is provided with slip stoppers 22. And the in-situ concrete part 5 is formed by using the upper surface flange 21 and the HPCa parts 3 and 3 of the steel girder part 2 as the lower surface formwork.

  For this reason, the concrete cast in the field is continuously filled between the upper surface of the steel girder 2, the HPCa parts 3, 3 and the truss bars 4,. The composite girder 1 in which the parts 3 and 3 are integrated can be formed.

  Further, by providing the slip stopper 22, the upper surface flange 21 and the cast-in-place concrete portion 5 can be integrated to function as a compression flange having a composite cross section, and a place where repeated loads are loaded like a railway. Even if applied to the above, the integrity of the composite beam 1 can be maintained.

  Furthermore, since the upper surface flange 21 and the HPCa parts 3 and 3 are the lower surface formwork, it is not necessary to perform the installation work and removal work of the lower formwork and support work, and the concrete placement work can be performed quickly and safely. be able to. Moreover, if it is the precast concrete member manufactured at a factory, high quality can be ensured.

  On the other hand, by setting the distance from the end face of the side edge of the steel girder 2 to the stopper 22 arranged closest to the stopper 22 is a predetermined distance or more, a shift occurs between the HPCa part 3 and the stopper 22. It is possible to ensure that there is not enough concrete width. That is, if the separation between the HPCa unit 3 and the stopper 22 is small, the amount of concrete cast in-between interposed therebetween decreases, and the shear strength necessary to prevent the shift cannot be ensured. Further, stress concentration may occur due to the stress from the slip stopper 22 acting on the concrete in a narrow range.

  On the other hand, by setting the separation between the HPCa unit 3 and the stopper 22 to be equal to or larger than a predetermined interval, the concrete is sufficiently filled to prevent the deviation and to distribute the stress. Further, in order to secure the necessary space in this way, it is preferable to increase the amount of overhang of the widened flange portion 21a of the upper surface flange 21.

  In addition, it is preferable that the end surface of the HPCa part 3 is made to be able to sufficiently resist the shearing force in the horizontal direction by performing a splicing process using a sieving or the like as necessary. Further, even if a predetermined interval cannot be ensured between the HPCa unit 3 and the stopper 22, the desired performance can be ensured by sighting or the like.

  Furthermore, the cast-in-place concrete part 5 is hardened by a structure in which the attachment piece 35 projecting from the HPCa part 3 and the upper surface flange 21 of the steel girder part 2 are fastened by bolts (not shown), and a predetermined strength is obtained. It is possible to secure support until the occurrence of

  Moreover, in the construction method of the composite girder 1 of the present embodiment, the HPCa portions 3 and 3 that are projected from the steel girder portion 2 are formed of precast concrete, so that the overhanging portion is highly self-supporting, and the HPCa on site. Support work under the part 3 can be omitted.

  For this reason, there are roads and railways below the HPCa unit 3 where the scaffolding and support work cannot be assembled from the ground, or where it is prohibited to install scaffolding in the sky due to the possibility of flying and falling. Even if it exists, the composite girder 1 can be easily constructed without being restricted in construction.

  Further, by connecting the wall portions 32, 32 of the HPCa portions 3, 3 with a detachable tie rod 7, it is possible to resist the force that temporarily acts on the floor slab unit 30 during lifting. . That is, when the floor slab unit 30 is lifted, a force such as bending in a direction that does not act at the time of installation is applied. However, it is not economical to reinforce the main installation structure for that purpose. Therefore, the tie rods 7 that are no longer necessary after the wall portions 32 and 32 are connected with the tie rods 7 so as to be less likely to bend when the floor slab unit 30 is lifted and placed on the steel girder unit 2. It is only necessary to remove and collect.

  Further, by removing the tie rod 7 after the structure is stabilized by installation or the like, the work is not hindered in the subsequent bar arrangement process and the concrete placing process.

  Moreover, if the mounting piece 35 is provided in the HPCa part 3 made from precast concrete, and the steel girder part 2 and the mounting piece 35 are fastened by a bolt (not shown), the floor slab unit 30 is made of the steel girder part 2. Fixing can be done quickly after being placed on top.

  Furthermore, if the HPCa parts 3 and 3 are fixed to the steel girder part 2, the displacement of the HPCa parts 3 and 3 can be suppressed even if the concrete is placed and its weight is applied. The work can be omitted or reduced, and the work period and work cost can be reduced.

  Although the best embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes that do not depart from the gist of the present invention are possible. Are included in the present invention.

  For example, in the above-described embodiment, the stopper 22 is illustrated, but the shape, number, and arrangement location are not limited thereto.

  In the above-described embodiment, the HPCa unit 3 including the floor 31 and the wall 32 has been described. However, the present invention is not limited to this. It may be the exit.

  Furthermore, in the above-described embodiment, the truss reinforcement 4 has been described as the connection reinforcing material. However, the present invention is not limited to this, and the shape retention is high enough to be able to be lifted in a state where the HPCa parts 3 and 3 are connected. For example, a ladder-like steel material or the like may be used as a connection reinforcing material as long as it is a member that has performance and can be integrated with the in-situ concrete portion 5 and the HPCa portion 3.

  Moreover, in the said embodiment, although the tie rod 7 was removed before placing concrete on-site, it is not limited to this, Until a desired intensity | strength is expressed in the on-site cast-in concrete part 5, as a support work It can also be installed.

It is sectional drawing explaining the structure of the structure of the synthetic | combination girder of the best embodiment of this invention. It is sectional drawing explaining the structure of the viaduct over which a synthetic girder is bridged. It is a top view explaining the structure of the structure of a composite girder. It is explanatory drawing which showed the process of hanging a floor slab unit on the steel beam part. It is explanatory drawing which showed the process of performing the reinforcement for the cast-in-place concrete part. It is explanatory drawing which showed the process of placing concrete. It is a figure explaining joining of the HPCa parts of the extending direction of a steel beam part, Comprising: (a) is sectional drawing of the HPCa part explaining the shape of a joining reinforcing bar, (b) is a structure of the junction part of HPCa parts FIG. It is a top view explaining the structure of the mesh line | wire arrange | positioned on the lower part and upper surface flange of the HPCa part installed near the girder edge part of steel girder parts.

Explanation of symbols

1 Composite Girder 1A, 1B, 1C Composite Girder 2 Steel Girder 21 Top Flange (Top)
22 Stopper 3 HPCa part (precast overhang part)
30 Floor slab unit 31 Floor 32 Wall 35 Mounting piece 35a Bolt hole 4 Truss (connecting reinforcement)
41 End 5 On-site concrete part 50 Floor slab 7 Tie rod (temporary connecting material)

Claims (5)

A structure of a composite girder formed by a steel girder part provided with a stopper on the upper surface and a concrete floor slab,
At both side edges of the upper surface of the steel girder part, an end is placed on the steel girder part outside the slip stopper, and a precast concrete precast projecting part projecting from the both side edges;
A connecting reinforcement between the precast overhangs, the lower part of both ends being embedded in the precast overhang and the upper part protruding upward,
A composite girder structure, wherein the floor slab is formed by a cast-in-place concrete part that is placed on the steel girder part and the precast overhang part to embed the connection reinforcing material.   2. The composite girder structure according to claim 1, wherein a distance from an end face of each side edge of the steel girder portion to the stopper disposed closest is set to a predetermined distance or more.   The synthetic | combination of Claim 1 or 2 with which the attachment piece protruded toward the said steel girder part from the said precast overhang | projection part and the upper surface of the said steel girder part are fastened with a volt | bolt. Digit structure. A method for constructing a composite girder formed by a steel girder having a stopper on the upper surface and a concrete slab,
A floor slab unit is manufactured by molding a precast overhanging portion having a floor portion and a wall portion extending upwardly at both ends of a connecting reinforcing material longer than the width of the steel girder portion by using concrete. Process,
Connecting the wall portions with a removable temporary connecting material;
Hoisting the floor slab unit and placing the precast overhangs on both side edges of the upper surface of the steel girder,
Removing and removing the temporary connecting material from the wall;
A method for constructing a composite girder, comprising the steps of placing reinforcing bars on the steel girder part and the precast overhanging part and placing concrete. A method for constructing a composite girder formed by a steel girder having a stopper on the upper surface and a concrete slab,
A step of producing a floor slab unit by molding a precast bulge portion with concrete at both ends of a connection reinforcing material longer than the width of the steel beam portion;
Hoisting the floor slab unit and placing the precast overhangs on both side edges of the upper surface of the steel girder,
Fastening the mounting piece projecting from the precast overhanging part onto the steel girder part and the upper surface of the steel girder part with bolts;
A method for constructing a composite girder, comprising the steps of placing reinforcing bars on the steel girder part and the precast overhanging part and placing concrete.

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