JP2018028229A - Composite girder a bridge constructed using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite girder capable of facilitating construction work to construct a bridge by reducing the girder height and weight of the bridge while requiring no rust prevention measures of steel material, and a bridge constructed by using the same.SOLUTION: A composite girder 1 is constituted of: a T-shaped steel material 2 which has a flange 22 on at least lower edge of a web 21; and a concrete bottom slab 3 which encloses the flange 22 of the T-shaped steel material 2 and allows the web 21 to protrude therefrom. The bridge 5 is constructed, on the composite girder 1 bridged between bridge abutments 53, 53 arranged parallel to each other perpendicular to an extension direction thereof, a cast-in-place concrete 52 is carried out over a buried formwork 56, which is bridged over the concrete bottom slabs 3, and the concrete bottom slab 3 to bury the web 21 of the T-shaped steel material 2 in the cast-in-place concrete 52.SELECTED DRAWING: Figure 16

Description

  The present invention relates to a composite girder in which a steel mold and concrete are integrated, and a bridge constructed using the composite girder.

  The bridge is constructed by constructing a concrete floor slab for the girders spanned between abutments, between piers, and between abutments and piers. The girders are usually made of steel molds (I-type, H-type, etc.). For example, the girders of H-shaped steel materials are arranged and arranged at appropriate intervals between abutments, between abutments, or between abutments and abutments in a posture in which the flange is horizontal and the web is vertical. The opening between the girders is closed by bridging the formwork between the lower flanges of the H-shaped steel material. And a floor slab is constructed by placing in-situ concrete in a space surrounded by the adjacent H-shaped steel material and the formwork after assembling structural reinforcing bars on the formwork. The bridge is constructed by providing roads and railings on the floor slab. Most of the mold steel is buried in the cast-in-place concrete, but the lower flange is exposed to the outside.

  Patent Document 1 discloses a composite girder having a steel lower flange at the lower end of a steel web and an upper flange made of reinforced concrete at the upper end of the steel web (Patent Document 1 [Claim 1]). The upper flange made of reinforced concrete constitutes a floor slab (Patent Document 1 [Claim 2]), or supports the floor slab by providing a receiving flange portion along the bridge axis direction (Patent Document 1 [Claim 2]. 3]) In addition, a reinforcing steel material can be embedded in advance (Patent Document 1, [Claim 4]). Further, Patent Document 1 welds a steel lower flange to the lower end of a steel web, spans a girder in which an upper flange made of reinforced concrete is placed on the upper end of the steel web, and is arranged in a direction perpendicular to the bridge axis. A bridge constructed by penetrating a laterally tightened PC steel wire in the direction perpendicular to the bridge axis through the installed upper flange and fastening the upper flange in the direction perpendicular to the bridge axis is disclosed (Patent Documents 1 and 5).

  The composite girder disclosed in Patent Document 1 does not need to weld the upper flange to the steel web, and can reduce the manufacturing cost. In addition, the composite girder disclosed in Patent Document 1 can be configured as a floor slab with an upper flange made of reinforced concrete, so that the workability of bridge construction can be improved, the work period can be shortened, and the structural height of the bridge can be reduced (patent) Literature 1 [0022]). Furthermore, the composite girder disclosed in Patent Document 1 can lay a separate floor slab on the upper flange, but it can still reduce the construction height of the bridge by reducing the structural height of the bridge or shortening the latter period. (Patent Literature 1, [0023]). And the composite girder which patent document 1 discloses can comprise the girder which can embed a reinforcing steel material and can oppose a compressive load when placing cast-in-place concrete in an upper flange (patent documents 1 and [0025]).

JP 2007-126813

  The synthetic girder disclosed in Patent Document 1 remains the same in that the steel material is exposed to the outside as in the case where the conventional steel mold material is used as the girder. This means that rust prevention measures are required for the steel material exposed to the outside. Moreover, even if a rust prevention measure (for example, applying a rust preventive paint) is applied to the steel material, there is a problem that the coating film is peeled off due to aging deterioration or collision with driftwood or the like and rust is generated. The combination of the steel material and the concrete upper flange can be evaluated in terms of increasing the rigidity as a composite girder, but the point that requires rust prevention measures for the steel material as in the conventional case needs to be improved.

  In addition, the composite girder disclosed in Patent Document 1 is provided with a perforated steel plate gibber (11c) on the upper edge of a steel web wrapped in, for example, a concrete upper flange to enhance the integrity between the steel material and the concrete upper flange. (Patent Document 1 [0028]). However, since the steel material is suspended from the upper flange and has a steel lower flange at the lower end, the possibility of the steel material coming out of the concrete upper flange cannot be denied. Moreover, the improvement of the rigidity as a composite girder by combining a steel material and a concrete upper flange is insufficient.

  In addition, the composite girder disclosed in Patent Document 1 is produced by placing an upper flange made of concrete (Patent Document 1 [0029]). Therefore, in a composite girder that combines steel and concrete, while reducing the weight of the bridge while minimizing the girder height, it aims to increase the integrity of the two and eliminate the need for rust prevention measures for the steel. Considering the ease of construction when building a bridge, we examined how to combine it with steel and concrete to be used.

  What has been developed as a result of the study is a composite girder composed of a steel mold having a flange at least at the lower edge of the web, and a concrete bottom plate that wraps the flange of the steel mold and projects the web. In addition to the existing T-type steel material, H-type steel material, or I-type steel material, the type steel material may have a configuration in which, for example, one steel plate is used as a web and a steel plate serving as a flange is attached to the edge of the web. There may be a plurality of webs. If the web or the flange is made thick or a separate reinforcing member (steel bar or steel plate) is attached, the rigidity and structural strength of the steel mold will increase. When a concrete bottom slab is used as a scaffold, the mold steel is preferably a T-type steel and the concrete bottom slab wraps the flange. Moreover, when it is desired to increase the rigidity of the composite girder, the shape steel material is preferably an H-type steel material or an I-type steel material, and the concrete bottom plate wraps one flange.

  By providing a vertical through hole in a flange wrapped in a concrete bottom slab, the mold steel is connected to the concrete bottom slab divided above and below the flange via the vertical through hole, thereby improving the integrity with the concrete bottom slab. A plurality of vertical through holes are provided at equal intervals or at unequal intervals in the extending direction of the composite beam. Each of the plurality of vertical through-holes provided may be formed by connecting a concrete bottom slab separated at the top and bottom of the flange, and may be an elongated slit in addition to a circular opening.

  Moreover, a shape steel material provides a horizontal through-hole which is not buried in a concrete bottom slab, or a part is buried in a web. The horizontal through-hole improves the integrity of the cast-in-place concrete and the cast steel material in a positional relationship where the main bars embedded in the cast-in-place concrete cast between the composite girders are engaged with the web of the cast steel material. The horizontal through-hole connects the concrete bottom slab divided into the left and right sides of the web through a part buried in the concrete bottom slab, and improves the integrity of the steel mold and the concrete bottom slab. A plurality of lateral through holes are provided at equal intervals or at irregular intervals in the extending direction of the composite beam. Each of the plurality of lateral through-holes provided only needs to be able to connect a concrete bottom slab divided into the left and right sides of the web, and may be an elongated slit in addition to a circular opening.

  When compressive force is introduced into the concrete bottom slab of a composite girder, the concrete bottom slab incorporates a PC steel material (PC steel wire, PC steel bar, etc.) that extends parallel to the mold steel material in tension. Examples of the PC steel material include string-like steel wires, stranded wires, and thin strips. PC steel can be built into a concrete bottom slab in a tensioned state by pulling it from both directions of extension and making it into a tensioned state, cutting both ends protruding from the end face of the concrete bottom slab and fixing both ends with fixing tools. In this way, the concrete bottom plate in which the PC steel material is housed in a tensioned state is compressed in the extending direction of the mold steel material in the process in which the tensioned PC steel material shrinks. The concrete bottom slab is wide because it wraps the flange of the mold steel. For this reason, a plurality of PC steel materials incorporated in the concrete bottom slab may be arranged at equal intervals or unequal intervals in the width direction of the concrete bottom slab.

  In order to enhance the unity between the cast-in-place concrete placed between the composite girders and the composite girders, the concrete bottom slab is provided with fixing bars embedded in the cast-in-place concrete cast. The fixing bars only need to protrude from the concrete bottom slab, but U-shaped bars in which both ends of the web are embedded in the concrete bottom slab while penetrating or straddling the web of the steel mold are preferable. When the fixing bar penetrates the web of the mold steel material, the above-described lateral through hole is used.

  If the top surface of the concrete bottom plate is inclined with respect to the flange of the steel plate, when the composite girder is bridged between the bridges with the flange leveled, the bottom surface of the cast-in-place cast concrete is the top surface of the concrete bottom plate. The transfer shape is inclined, and the lower surface of the cast-in-place concrete and the upper surface of the concrete bottom slab are horizontally engaged. The upper surface may be inclined in any direction, and the entire upper surface may be inclined in one direction, may be configured with a plurality of inclined surfaces having different angles, or may be configured with regular or irregular unevenness as a whole. In addition, when the concrete bottom slab is provided with a reinforcing bar that penetrates or surrounds the flange of the wrapped mold steel material, the concrete bottom slab improves the integrity of the mold steel material while enhancing its structural strength.

  For concrete bottom slabs, if the step surfaces for the formwork lowered from the upper surface are provided on both left and right edges, the embedded formwork can be located and positioned just by placing both edges on the opposite step surfaces for the formwork. Is also prevented. The embedded formwork can easily fill the gap of the concrete bottom slab that increases or decreases according to the total width of the bridge by adjusting the individual widths. A concrete bottom slab has a lower step surface and an upper step surface that protrude alternately in the vertical direction when the lower step surface and the upper step surface from the lower surface are allocated to the left and right edges. It is possible to place the cast-in-place concrete without using the embedded formwork, and to construct the bottom plate of the bridge only with the concrete bottom plate of the adjacent composite girder.

  The bridge constructed using the composite girder of the present invention is as follows. That is, in a bridge constructed by placing cast-in-place concrete on the arranged composite girders, the composite girders wrap the mold steel having a flange on at least the lower edge of the web, and the lower flange of the mold steel, It is composed of a concrete slab that protrudes from the web, each of which is oriented in the direction of extension of the steel plate, and arranged in a direction perpendicular to the direction of extension, spanning between abutments, between piers, and between abutments and piers. For the girders, by constructing the cast-in-place concrete over the buried formwork spanned between the concrete bottom slab and the concrete bottom slab, the web of the mold steel material was buried in the in-situ cast concrete and constructed. It is a bridge.

  In the bridge of the present invention, the composite girder is provided with a horizontal through hole that is not buried in the concrete bottom slab or partly buried in the web of the mold steel material. Buried in The cast-in-place concrete that has been placed becomes reinforced concrete by the main reinforcement. The main reinforcement can be fixed to the web of the steel mold by welding. The main bar passing through the horizontal through hole can be in contact with the inner peripheral edge of the horizontal through hole to physically support the web, and can also be fixed by welding to the web. Moreover, a horizontal through-hole connects the cast-in-place concrete divided into the right and left of the web. Thus, the shape steel material and the on-site cast concrete improve the unity. A plurality of lateral through holes are provided at equal intervals or at irregular intervals in the extending direction of the composite beam. Each of the plurality of lateral through holes provided only needs to be able to pass the main muscle, and may be a long slit as well as a circular opening.

  In the bridge according to the present invention, the composite girder inclines the upper surface of the concrete bottom slab with respect to the flange of the steel plate material, and the lower surface of the cast-in-place concrete and the upper surface of the concrete bottom slab, which have a transfer shape of the upper surface of the concrete bottom slab, are horizontally aligned. Engage. The composite girder is inclined with the bottom surface of the cast-in-place concrete cast as a transfer shape of the top surface of the concrete bottom slab by placing the flange horizontally between the bridges. And engage horizontally. The composite girder may have a configuration in which the upper surface is inclined freely and the entire upper surface is inclined in one direction, a configuration having a plurality of inclined surfaces having different angles, or a configuration composed of regular or irregular asperities.

  In the bridge of the present invention, the composite girder embeds the fixing bars provided by protruding from the concrete bottom slab together with the main bars in the in-situ concrete. As described above, the main bar can be fixed by welding to the web of the shape steel material, and can also be fixed to the fixing bar by welding or bundling. Moreover, the intensity | strength of the in-situ concrete in which the fixing reinforcement and the main reinforcement were embedded can be improved. Furthermore, the steel plate material, the concrete bottom slab, and the cast-in-place concrete are integrated through the fixing bar and the main bar.

  In the bridge of the present invention, the composite girder is provided with a stepped surface for formwork that is lowered from the upper surface of the concrete bottom slab on the left and right edges of the concrete bottom slab, and spans between the stepped surfaces for formwork facing each other of the adjacent composite girder. The cast-in-place concrete was cast across the buried formwork and the concrete bottom slab. As a result, the position of the embedded formwork is specified, and misalignment is also prevented. The bridge of the present invention assumes that a composite girder concrete bottom plate is used as a scaffold, for example, when placing main bars, etc., so that the worker does not use the embedded formwork as a foot kick so that It is better to make the step surface for the frame deeper.

  In the bridge according to the present invention, the composite girder is provided by allocating a receiving step surface lowered from the upper surface of the concrete bottom slab and an upper step surface rising from the lower surface of the concrete bottom slab to the left and right edges of the concrete bottom slab. The cast-in-place concrete was laid over the concrete bottom slabs connected by crossing the facing lower step surface and the upper step surface of the adjacent composite girders. As a result, it is possible to construct a bridge by placing cast-in-place concrete without using an embedded formwork, while responding to changes in the overall width of the bridge. The bridge of the present invention has no difference in girder height, regardless of whether the buried formwork is used or not, and the cast-in-place concrete is cast on the concrete bottom slab.

  Since the composite girder according to the present invention has a configuration in which a mold steel material and a concrete bottom slab are combined, the rigidity is higher than that of a girder made only of a mold steel material. For example, a gap between an abutment and a pier or between piers can be increased. In particular, when the mold steel material is an H-type steel material or an I-type steel material, the rigidity of the mold steel material alone is increased, and the rigidity as a composite girder is also improved. The synthetic girder with high rigidity can eliminate or reduce the warpage (camber) of the die steel material, and therefore, the labor and labor of processing to give the warp can be reduced. This has the effect of reducing the manufacturing cost of the composite girder. Further, the composite girder of the present invention can introduce a compressive force into the concrete bottom slab by incorporating a tensioned PC steel material in the concrete bottom slab. This is simpler than the case where the mold steel is forcibly warped and the compressive force is introduced into the concrete bottom slab, and brings about the effect of reducing the cost for introducing the compressive force.

  The composite girder of the present invention wraps the lower flange of the steel plate with a concrete bottom plate, isolates the steel plate material from the outside by the main body concrete and the concrete bottom plate to be cast in the field, and eliminates the need for rust prevention measures for the steel plate material. . The concrete bottom slab has a built-in reinforcing bar, and the cast-in-place concrete has a built-in main bar to increase the structural strength. In addition, since the steel plate material is built in between the concrete bottom slab and the cast-in-place concrete, the rigidity and structural strength of the composite girder supporting the bridge is also improved. Thus, the composite girder of the present invention provides a bridge having excellent rigidity and structural strength.

  In addition, the concrete bottom slab functions as a scaffold spanned between abutments, between piers, and between abutments and piers. This facilitates on-site work such as placement of main bars and placement of on-site cast concrete. In particular, when the type steel material is a T-type steel material, since there is no flange at the upper end of the web, the field work using the concrete bottom plate as a scaffold is easy. In addition, the concrete bottom slab is washed out and coated with an adhesive to improve the integrity with the on-site cast concrete, prevent water from entering the interface with the on-site cast concrete, The durability of can be improved.

  The vertical through hole provided in the flange of the mold steel material improves the integrity of the mold steel material and the concrete bottom slab, and facilitates the introduction of compressive force to the concrete bottom slab by the pre-tension method or the post-tension method. The horizontal through-hole provided in the web of the shape steel material increases the degree of freedom of the arrangement of the main bars by penetrating the main bars. The horizontal through-hole partially buried in the concrete bottom slab improves the integrity of the mold steel and the concrete bottom slab, and also improves the integrity of the mold steel and the on-site cast concrete. Increase the unity with concrete.

  The lateral through-hole provided in the web of the mold steel material has an effect of improving the structural strength and rigidity of the bridge including the composite girder by improving the integrity of the mold steel material and the cast-in-place concrete to be cast. The fixing bar provided on the concrete bottom slab serves to fix the position by connecting the main bar by welding or the like, and improves the structural strength of the cast-in-place concrete to be placed as a reinforcing bar in the same manner as the main bar. In addition, the anchor bars provided on the concrete bottom slab are integrated with the concrete bottom slab, and have the effect of increasing the structural strength and rigidity of the bridge including the composite girder.

  The inclined upper surface of the concrete bottom slab is engaged horizontally with the lower surface of the cast-in-place cast concrete and the upper surface of the concrete bottom slab. This prevents shear displacement between the composite girders and the cast-in-place cast concrete and eliminates the need to increase the thickness of the cast-in-place concrete to prevent the shear displacement. The weight can be reduced and the lower structure can be simplified. The reinforcing bars of the concrete bottom slab have the effect of improving the structural strength and rigidity of the composite girder by improving the integrity of the steel plate while strengthening its structural strength.

  The step surface for the formwork provided on the concrete bottom slab prevents the embedded formwork from being displaced, eliminates the risk of a worker working with the concrete bottom slab as a footstep and shifting the embedded formwork, Make sure there are no gaps between the concrete slabs. This ensures safety so that an operator can not step into the shifted embedded form or the gap formed by shifting the embedded form. If the level difference surface for the mold is deeper than the thickness of the embedded mold, the embedded mold does not protrude from the upper surface of the concrete bottom plate, and there is no possibility that the operator will kick the embedded mold.

  Since the concrete bottom slab is made in advance at the factory, it is easier to improve the quality and structural strength compared to the cast-in-place concrete. Since the bridge of the present invention is composed of a concrete girder slab of composite girder as a bottom slab, the structural strength can be made higher than the bottom slab of a bridge made of in-situ concrete and the effect of reducing cracks can be obtained. In particular, the concrete bottom plate provided with the lower step surface and the upper step surface can connect the concrete bottom plates of adjacent composite girders to form the bottom plate of the bridge, so that the above effect can be enjoyed better. Moreover, the bridge which connects a concrete bottom slab and comprises a bottom slab has the advantage that a cast-in-place concrete can be cast without using an embedded formwork, and the effect of reducing construction cost is also acquired.

  Since the bridge constructed using the composite girder of the present invention lays the cast-in-place concrete by embedding the web of the steel beam of the composite girder, an increase in the girder height due to the placement of the cast-in-place concrete is suppressed. Further, since the mold steel material is buried in the cast-in-place concrete, the mold steel material is not exposed to the outside, and the conventionally required rust prevention measures and maintenance of the mold steel material become unnecessary. Furthermore, since the embedded formwork does not need to be collected, a scaffolding or a supporting work for collecting it is not necessary. Thus, the bridge of the present invention has an effect of reducing the construction cost.

It is a perspective view showing an example of a synthetic girder to which the present invention is applied. It is a right view of the composite girder of this example. It is a top view of the composite girder of this example. It is a front view of the composite girder of this example. It is the partial right view which extracted only the front vicinity of the composite girder of this example. It is a perspective view of the T type steel material which comprises the synthetic girder of this example. 6 is a front view of a composite girder according to another example 1. FIG. It is the partial right view which extracted only the front vicinity of the composite girder of another example 1. 6 is a perspective view of an H-shaped steel material that constitutes a composite girder of another example 1. FIG. It is a right view showing the state where the composite girder of this example was bridged between abutments and arranged. It is a front view showing the state which spanned and arranged the synthetic girder of this example between the abutments. It is a front view showing the state where the composite girder of another example 2 was bridged between abutments and arranged. It is a right view showing the state which has arrange | positioned the main reinforcement in the synthetic girder of this example arranged across the abutment. It is a front view showing the state which has arrange | positioned the main streak to the composite girder of this example arranged across the abutment. It is a right view showing the state where the cast-in-place concrete was cast, the pavement surface was formed, and the bridge was constructed. It is a front view showing the state where the cast-in-place concrete was cast, the pavement surface was formed, and the bridge was constructed.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. As shown in FIGS. 1 to 6, the composite girder 1 of the present invention wraps a T-shaped steel member 2 having a flange 22 projecting left and right from the lower edge of the web 21, and a flange 22 of the T-shaped steel member 2. It is composed of a concrete bottom slab 3 that protrudes the web 21 from the left and right center of the upper surface 33. The concrete bottom slab 3 is naturally longer and wider than the T-type steel material 2 because it surrounds the flange 22 of the T-type steel material 2. From this, the composite girder 1 of this example follows the length and width of the concrete bottom slab 3 in length and width.

  The T-type steel material 2 of this example is provided with horizontal through holes 211 at equal intervals in the extending direction of the web 21 and vertical through holes 221 at equal intervals in the extending direction of the flanges 22 that project to the left and right (see FIG. 6). The lateral through hole 211 is a circular opening having a diameter exceeding half the height of the web 21 and is partially embedded in the concrete bottom slab 3. The vertical through hole 221 is a circular opening having a diameter through which the fixing bar 32 protruding from the concrete bottom slab 3 passes. Thus, the concrete bottom slab 3 is connected through the horizontal through hole 211 and the vertical through hole 221 so that the integrity of the T-shaped steel material 2 and the concrete bottom slab 3 is enhanced.

  The concrete bottom slab 3 of this example has a flat trapezoidal cross section as a whole except for the step surfaces 331 and 331 for formwork provided on both left and right edges. The embedded form 56 is bridged over the opposite formwork step surfaces 331 of the side-by-side composite girders 1 and 1 (see FIG. 11 described later). The concrete bottom slab 3 incorporates reinforcing bars 34 made of steel bars arranged at equal intervals in the vertical and horizontal directions. The reinforcing bar 34 of the present example provides a reference position of the PC steel material 31 that applies a compressive force to the concrete bottom slab 3 and provides a support base for the fixing bar 32.

  When forming the concrete bottom slab 3, the PC steel material 31 protrudes from the front and back sides of the concrete bottom slab 3 and is pulled to the front side and the back side. After the concrete bottom slab 3 is formed, By releasing the state, a compressive force is applied to the concrete bottom slab 3. PC steel material 31 of this example prepares three steel bars on the left and right and in the middle and pulls the three steel bars in the same way by pulling them at the position on the steel bar extending in the lateral direction among the reinforcing bars 34. The left and right compressive force is applied to the concrete bottom plate 3.

  The fixing bar 32 is a steel bar that protrudes from the concrete bottom slab 3 across the web 21 of the T-shaped steel material 2 and supports the main bar 51 embedded in the in-situ concrete 52 by welding. The fixing bar 32 of this example is substantially U-shaped with the upper ends tied, and the reinforcing bars built in the concrete bottom slab 3 have left and right ends penetrated through the vertical through holes 221 provided in the flange 22 of the T-shaped steel material 2. It is joined with 34 by welding. The fixing bar 32 of this example is not joined to the T-type steel material 2 just by passing through the vertical through hole 221, but the positional relationship with the T-type steel material 2 is fixed via the concrete bottom plate 3.

  The concrete bottom slab 3 of this example has only the upper surface 33 while the bottom surface and the step surfaces 331, 331 for the formwork are parallel to the flange 22 of the T-shaped steel material 2 (represented by the reference line L parallel to the flange 22 in FIG. 2). The slope is inclined upward from the front to the back. Thereby, the lower surface 521 of the cast-in-place concrete 52 is inclined in the range of the upper surface 33, and the lower surface 521 and the upper surface of the concrete bottom slab 3 are engaged in the horizontal direction.

  Here, in the concrete bottom slab 3 of this example, a plane other than the upper surface 33, for example, a step surface 331 for formwork is parallel to the flange 22. Since the lower surface 521 of the cast-in-place concrete 52 is formed in parallel with the flange 22 except for the range of the upper surface 33 of the concrete bottom slab 3, there is no possibility of sliding down along the inclined upper surface 33. Further, since a plurality of composite girders 1 are arranged, if the inclination of the upper surface 33 of the concrete bottom slab 3 is arranged alternately, the inclination of the lower surface 521 of the in-situ concrete 52 is also changed, and there is no possibility of sliding down along the inclined upper surface 33.

  Since the composite girder 1 of this example constituted by the T-shaped steel material 2 and the concrete bottom slab 3 is not obstructed above the concrete bottom slab 3, the concrete bottom slab 3 can be easily used as a scaffold. However, the web 21 whose upper edge is opened as a cut end of the steel plate cannot have a high rigidity. For this reason, for example, measures are taken to weld a steel bar or a steel plate to the upper edge, weld a steel bar or a steel plate to the web 21, and further increase the thickness of the web 21 itself.

  For example, as can be seen in FIGS. 7 to 9, the composite girder 1 of another example 1 constituted by the H-shaped steel material 4 and the concrete bottom slab 3 improves the rigidity of the web 51. The composite girder 1 of another example 1 is equivalent to the structure which welded the steel plate parallel to the flange 22 to the upper end of the web 21 of the composite girder 1 (refer FIGS. 1-6) of this example. Since the H-type steel material 4 has a higher section modulus than the T-type steel material 2, the composite girder 1 of Example 1 has higher rigidity than the synthetic keita 1 of this example.

  The H-shaped steel material 4 of another example 1 has horizontal through-holes 411 at equal intervals in the extending direction of the web 41, and vertical through-holes 421 and 421 at equal intervals in the extending directions of the upper and lower flanges 42 and 42 projecting left and right. Provided (see FIG. 9). The lateral through-hole 411 is a circular opening having a diameter of about 1/3 of the height of the web 21 and is partially embedded in the concrete bottom slab 3. Further, the vertical through hole 421 is a circular opening having a diameter through which the fixing bar 32 protruding from the concrete bottom slab 3 passes.

  The concrete bottom slab 3 has a substantially trapezoidal cross-sectional shape, an inclined upper surface 33, mold step surfaces 331 and 331 provided on the left and right edges, a built-in reinforcing bar 34, and a PC steel 31 as in the composite girder 1 of this example. The fixing streak 32 is substantially U-shaped with the upper ends tied, like the composite girder 1 of this example. However, the point which penetrates the vertical through-hole 421 provided in the upper flange 42, protrudes upwards, and straddles the upper flange 42 of the H-shaped steel material 4 differs (refer FIG.7 and FIG.8). Thereby, the fixing bar 32 of the different example 1 can be supported by welding the main bar 51 embedded in the in-situ concrete 52 above the H-shaped steel material 4.

  The bridge 5 is constructed by the following procedure using the composite girder 1 (see FIGS. 1 to 6) of this example. First, as seen in FIGS. 10 and 11 (the abutment 53 and the pavement 57 in the front of FIG. 11 are not shown), a plurality of side-by-side composite girders 1 are bridged between the supports 531 and 531 between the abutments 53 and 53. hand over. The composite girder 1 sets the length of the concrete bottom slab 3 in accordance with the distance between the abutments 53 and 53, as in the prior art. Moreover, the composite girder 1 sets the width of each concrete bottom slab 3 according to the division width which equally divided the road width. The width of the concrete bottom slab 3 is made smaller than the division width, and the remaining gap is closed with an embedded form 56 (see FIG. 11).

  Since the width of the embedded form 56 is adjustable, the gap formed by the concrete bottom slab 3 of the adjacent composite girder 1 may be slightly increased or decreased. Moreover, since the composite girder 1 of the present invention can widen the concrete bottom slab 3, the gap formed by the adjacent composite girders 1 and 1 is relatively small. As a result, the embedded form 56 that closes the gap may be a concrete plate having a narrower width than conventional ones, and can be stably supported by the form step surface 331, so that no support work is required. This brings about practical effects such as shortening the construction period and reducing the construction cost.

  Here, as shown in FIG. 12, like the composite girder 1 of another example 2, a pair of lower step surface 332 and upper step surface 333 are provided on the left and right edges of the concrete bottom slab 3, and the bottom of the adjacent composite girder 1 is provided. The receiving step surface 332 and the upper step surface 333 can be crossed to eliminate a gap. The undersurface stepped surface 332 of another example 3 is a bottom surface of a convex ridge having a square cross-section that is half the thickness of the concrete bottom slab 3 and projects to the left continuously from the top surface 33. Further, the upper stepped surface 333 of the third example is the upper surface of a convex strip having a square cross section that is half the thickness of the concrete bottom slab 3 and projects rightward continuously from the bottom surface. The lower stepped surface 332 and the upper stepped surface 333 are hung up and down with a sealant or the like interposed therebetween.

  The protrusions forming the lower receiving step surface 332 and the upper step surface 333 have the same overhang length. For this reason, the clearance gap surface 332 and the upper stepped surface 333 can completely eliminate the gap by placing the sealing material with the entire surface facing each other. The lower stepped surface 332 and the upper stepped surface 333 can close the gap if they can be hooked so as to sandwich the sealing material. From this, the composite girder 1 can adjust the left-right distance within the range in which the lower step surface 332 and the upper step surface 333 are overlapped.

  In the composite girder 1 of this example, the upper surface 33 is inclined in one direction. For this reason, when a plurality of composite digits 1 are arranged, the inclination directions are staggered. In the case of this example, the upper surface 33 of the composite girder 1 at the left end, the center and the right end when viewed from the front side (front side in FIG. 11) is inclined from the back side (back side of the paper surface in FIG. 11) to the front side, and the composite The upper surface 33 of the composite beam 1 that is second from the left end and second from the right end sandwiched between the beams 1 is inclined from the front side to the back side. Thereby, the lower surface 521 of the cast-in-place concrete 52 which becomes the transfer shape of the upper surface 33 of each composite beam 1 is also inclined alternately and can be engaged with the upper surface 33 of the composite beam 1 without deviation.

  Next, as seen in FIGS. 13 and 14 (the abutment 53 and the pavement 57 in the front in FIG. 14 are not shown), the vertical direction (composite girder) with respect to the composite girder 1 bridged between the abutments 53, 53 Steel bars extending in the lateral direction (1 extending direction) and the transverse direction (the extending orthogonal direction of the composite beam 1) are arranged as the main bars 51. In the case of this example, the steel bar of the main reinforcing bar 51 extending in the horizontal direction is passed through the horizontal through hole 211 provided in the web 21 of the T-type steel material 1 and is fixed to the inner peripheral edge of the horizontal through hole 211 by welding. Further, the steel bars of the main bars 51 extending in the vertical direction or the horizontal direction are joined together by welding, or the steel bars are welded and fixed to the fixing bars 32 of the composite girder 1. The concrete bottom slab 3 of the composite girder 1 can be used as a scaffold for the work of arranging the main bars 41.

  In the construction of the conventional bridge, it was necessary to assemble a separate scaffold when arranging the main bars. Moreover, in the construction of the conventional bridge, the scaffold becomes an obstacle, and it is difficult to pass the steel bars in the vertical direction and the horizontal direction, or it is difficult to weld the steel bars together. In this example, except for the mold step surface 331, the upper surface 33 constituting substantially the same plane provides a scaffold, so that the work of placing the main bar 51 becomes easy. This brings about practical effects such as shortening the construction period and reducing the construction cost. Here, since the embedded formwork 56 is located at a position lower than the upper surface 33 serving as a scaffold, it does not interfere with the operation of placing the main reinforcement 51 and does not shift its position.

  In this way, after the arrangement of the main reinforcement 51 is finished, the cast-in-place concrete 52 is placed with the buried form 56 and the concrete bottom slab 3 as the bottom, and the fixing that protrudes from the web 21 of the T-type steel material 2 and the concrete bottom slab 3 together with the main reinforcement 51. The bars 32 are integrally buried in the in-situ cast concrete 42. In order to improve the adhesion between the concrete bottom slab 3 and the cast-in-place concrete 42, it is preferable to wash the upper surface 33 into a rough surface or apply an adhesive for concrete. Such washing out and application of the adhesive can be easily performed by using a scaffold other than the concrete bottom slab 3 as a work target.

  After curing the cast-in-place cast concrete 42, the pavement surface 55 is removed as shown in FIGS. 15 and 16 (the abutment 53, the pavement surface 57, and the expansion device 54 are not shown in FIG. 16). Form the bridge 5 to complete it. The pavement surface 55 is flush with the road surfaces 57 and 57 continuous with the bridge 5, and a conventionally known expansion / contraction device 54 is interposed between the road surface 57 and the pavement surface 55. Although the illustration of the bridge 5 of this example is omitted for convenience of explanation, if the paved surface 55 is a roadway, a sidewalk and a roadway cover (not shown) are provided.

  It can be seen that the bridge 5 of this example is slightly higher than the height of the composite girder 1 and is lower than the bridge constructed by the conventional composite girder. Further, in addition to the T-shaped steel material 2 constituting the composite girder 1, the fixing bar 32 protruding from the concrete bottom slab 3 and the main bar 51 arranged at the time of construction are all wrapped in the cast-in-place concrete 52 and are not exposed to the outside. This means that the bridge 5 constructed using the composite girder 1 of the present invention does not require a rust prevention measure for steel in principle, and has the effect of reducing the construction cost and management cost of the bridge 5.

  The bridge 5 of this example has a configuration in which the composite girder 1 is bridged between a pair of abutments 53 and 53 for convenience of explanation. However, if there is a pier between the pair of abutments 53, 53, a long bridge can be constructed as in the past by bridging the composite girder 1 between the abutment 53 and the pier. In this case, the effect obtained by the composite girder 1 bridged between the abutments, between the piers or between the abutment and the pier can be obtained as in this example. Rather, an increase in the number of composite digits 1 to be bridged increases the overall cost reduction, and the effect of the present invention can be further enjoyed.

1 Composite Girder 2 Type Steel
21 Web
22 Flange 3 Concrete bottom slab
31 PC steel
32 Anchorage
33 Top view
34 Reinforcing bars Type 4 steel
41 Web
42 Flange 5 Bridge
51 Main muscle
52 On-site concrete
53 Abutment
54 Telescopic device
55 Paved surface
56 Embedded formwork
57 Road surface L Reference line parallel to the flange

Claims (17)

A steel mold having a flange at least at the lower edge of the web;
A composite girder composed of a concrete bottom slab that wraps the flange of the steel mold and projects the web. The composite girder according to claim 1, wherein the mold steel material is a T-shaped steel material, and the concrete bottom slab wraps the flange. The composite girder according to claim 1, wherein the mold steel material is an H-type steel material or an I-type steel material, and the concrete bottom plate wraps one flange. The composite steel beam according to any one of claims 1 to 3, wherein the mold steel is provided with a vertical through hole in a flange wrapped in a concrete bottom slab. The composite girder according to any one of claims 1 to 4, wherein the mold steel material is provided with a horizontal through hole in the web which is not buried in a concrete bottom plate or partly buried therein. 6. The composite girder according to any one of claims 1 to 5, wherein the concrete bottom slab includes a built-in PC steel material extending in parallel with the mold steel material in a tension state. The composite girder according to any one of claims 1 to 6, wherein the concrete bottom slab has an upper surface inclined with respect to the flange of the die steel material. The composite girder according to any one of claims 1 to 7, wherein the concrete bottom slab is provided with anchor bars embedded in the cast-in-place concrete. The composite girder according to any one of claims 1 to 8, wherein the concrete bottom slab is provided with a reinforcing bar that penetrates or surrounds the flange of the wrapped type steel material. The composite girder according to any one of claims 1 to 9, wherein the concrete bottom slab is provided with step surfaces for formwork, which are lowered from the upper surface, on both left and right edges. The composite girder according to any one of claims 1 to 9, wherein the concrete bottom slab is provided with a receiving step surface that is lowered from the upper surface and an upper step surface that is raised from the lower surface, allocated to both left and right edges. In bridges constructed by placing cast-in-place concrete on the composite girders arranged,
The composite girder includes a steel plate having a flange at least at the lower edge of the web, and
A concrete bottom plate that wraps around the lower flange of the steel mold and projects the web;
Each of them is oriented in the direction of extension of the steel sheet, and is bridged between the concrete bottom slabs for a plurality of composite girders that are arranged perpendicularly to the direction of extension and bridged between the abutments, between the piers, and between the abutments and the piers. A bridge characterized in that a cast steel material web is buried in the cast-in-place concrete by casting a cast-in-place concrete over an embedded formwork and the concrete bottom plate. 13. The composite girder has a horizontal through hole that is not embedded in a concrete bottom slab or is partially embedded in a web of a mold steel material, and a main bar that passes a part or all of the horizontal through hole is embedded in a cast-in-place concrete. The listed bridge. The composite girder is formed by inclining the upper surface of the concrete bottom slab with respect to the flange of the steel plate, and horizontally engaging the lower surface of the cast-in-place concrete and the upper surface of the concrete bottom slab, which is a transfer shape of the upper surface of the concrete bottom slab. Or any one of 13 bridges. The bridge according to any one of claims 12 to 14, wherein the composite girder is embedded in the cast-in-place concrete with fixing bars provided so as to protrude from the concrete bottom plate. The composite girder is provided with stepped surfaces for the formwork descending from the upper surface of the concrete bottom slab on the left and right edges of the concrete bottom slab, The composite girder according to any one of claims 12 to 15, wherein a cast-in-place concrete is cast over the concrete bottom slab. The composite girder is formed by allocating a receiving step surface lowered from the upper surface of the concrete bottom plate and an upper step surface raised from the lower surface of the concrete bottom plate to the left and right edges of the concrete bottom plate. The composite girder according to any one of claims 12 to 15, wherein the cast-in-place concrete is laid over a concrete bottom slab connected by crossing the opposed lower step surface and the upper step surface.

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