JP2018204356A - Steel girder reinforcement method - Google Patents

Abstract

To provide a steel girder reinforcement method that generates neither residual stress due to thermal shrinkage caused by welding of a shear connector during replacement of a floor slab of a bridge, or unintended bending of a steel girder; while at the same time being capable of reinforcing the steel girder.SOLUTION: A method of reinforcing a steel girder 2 when replacing an existing floor slab of a bridge 1 with a new floor slab involves: placing a reinforcing steel plate 6, for reinforcing an upper surface of the steel girder 2, on a flat surface and welding with a shear connector, such as a stud dowel JB or a horseshoe-shaped dowel, in a state where no stress acts; then joining the reinforcing steel plate 6 welded with a shear connector in a state where no stress acts, to the upper surface of the steel girder 2 from which the existing floor slab has been removed.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a method for reinforcing an existing steel girder, and more specifically, reinforcement of a steel girder that reinforces an existing steel girder that needs to be reinforced when replacing an existing floor slab that has deteriorated over time with a new floor slab. It is about the method.

  In bridges such as road bridges, existing floor slabs that have deteriorated over time (aged) are replaced with new floor slabs. However, the standard of design load (live load such as wheel load in design) has changed between the time of building the bridge and the present, and the steel girders that support the bridge may have to be reinforced when the slab is replaced. For this reason, conventionally, in addition to replacing the floor slab when replacing the floor slab, a large bracket or beam has been attached to the existing steel girder for reinforcement.

  Also, as a combination of floor slabs and girders and to prevent displacement, it is necessary to weld stud gibbles (studs with heads), horseshoe-shaped gibels, etc. to the upper flanges of the steel girders that are the main girders by stud welding. It was. However, if welding is performed in a state where a load such as its own weight is applied to the steel girder and a stress such as bending stress is applied, compressive residual stress acts on the upper flange due to thermal contraction, which is the main girder. The result was an unexpected bending of the steel girder.

  In particular, since the composite girder is integrated with the floor slab to counter external force, the cross-sectional area of the steel girder (particularly the thickness of the upper flange) is reduced. In addition, in composite girders, in order to expect the composite effect of the floor slab and steel girders, a large number of detents such as stud gibbles must be welded in the field, and the bending that is not assumed in the steel girders during welding The problem of the occurrence of this was remarkable. For this reason, the steel girder reinforcement method which suppresses bending of a steel girder by the influence of the heat shrink by field welding has been desired.

  For example, in Patent Document 1, a compression brazing material is attached in the longitudinal direction of the steel girder on the side of the belly plate near the upper flange of the I-section steel girder, and the reaction force is supported by a bracket fixed to the steel girder plate. A method of reinforcing an existing steel girder is disclosed in which a compressive force is applied to the compression girdle and tensile stress is introduced above the centroid position of the steel girder (Claim 1, Claim of Patent Document 1) (See paragraphs [0009] to [0013] of the book, FIGS. 1 and 2 of the drawings, etc.).

  The method for reinforcing an existing steel girder described in Patent Document 1 reduces the compressive stress generated in the upper flange of a steel girder without providing a temporary support when replacing the floor slab of a steel-concrete composite girder. It is supposed to prevent.

  Further, in Patent Document 2, a reaction force stand is installed below the existing main girder, a support girder is arranged below the reaction force stand, and the support girder is joined to the existing main girder by a joining means. Furthermore, a main girder provisional method in a floor slab replacement method for a composite girder in which a jack is arranged between the support girder and the existing main girder and the existing main girder is provisionally received by jacking up the jack is disclosed. (See claim 1 of patent document 1, paragraphs [0020] to [0030] of the specification, FIGS. 1 to 8 of the drawings, etc.).

  The main girder provisional method in the floor slab replacement method described in Patent Document 2 can be safely and reliably constructed without using a vent, can shorten the construction period, can also handle curved girder, and easy camber adjustment Therefore, it is said that it is economical.

  However, the reinforcing method of the existing steel girder described in Patent Document 1 and the main girder provisional receiving method in the floor slab replacement method described in Patent Document 2 need to attach a large bracket or beam to the existing steel girder. There was a problem that the facility was large and expensive. Moreover, in the reinforcement method of the existing steel girder described in Patent Document 1 and the main girder provisional receiving method described in Patent Document 2, it is necessary to weld the stud to the upper flange of the steel girder in the field for synthesis with the floor slab. However, it has not been possible to solve the problem that a compressive residual stress acts on the upper flange due to heat shrinkage and an unexpected bending occurs in the steel beam.

Japanese Patent Laid-Open No. 9-256322 Japanese Patent Laid-Open No. 2006-8406

  Therefore, the present invention has been devised in view of the above-mentioned problems, and the object of the present invention is that a steel girder is assumed that no residual stress is generated due to thermal contraction when a bridge slab is replaced. It is an object of the present invention to provide a method for reinforcing a steel girder that does not cause any bending and at the same time can reinforce the steel girder.

  The method for reinforcing a steel girder according to claim 1 is a method for reinforcing a steel girder when an existing floor slab of a bridge is replaced with a new floor slab, and a reinforcing steel plate for reinforcing the upper surface of the steel girder is mounted on a plane. Welding stoppers such as stud gibbles or horseshoe-shaped gibels in a state where stress is not applied, and then reinforcing steel plate to which the stoppers are welded in a state where stress is not applied, the existing floor slab has been removed The steel girder is joined to the upper surface.

  The method for reinforcing a steel girder according to claim 2 is the method for reinforcing a steel girder according to claim 1, wherein the bridge is a composite girder, and the existing stopper is cut when the existing floor slab is removed. In addition, the reinforcing steel plate welded with a stopper in a state where no stress acts is bolted to the upper surface of the steel girder from which the existing floor slab has been removed.

  According to the method for reinforcing a steel girder according to claims 1 and 2, the reinforcing steel plate is placed on a flat surface, not on-site welding, and the slip stopper is welded in a state where no stress acts, and the reinforcing steel plate is attached to the steel girder. Since it is joined to the upper surface of the steel plate, residual stress due to thermal contraction does not occur at the time of displacement welding at the time of replacing the slab, and the steel girder is not assumed to be bent.

  According to the method for reinforcing a steel girder according to claims 1 and 2, the non-slip welding is not performed on-site, but is performed separately outside the site of a factory or the like, and only dry bonding is required at the site of replacing the floor slab. Therefore, the field work can be shortened and the period of road closure can be shortened. For this reason, the labor cost of floor slab replacement can also be reduced.

  Further, according to the method for reinforcing a steel girder according to claims 1 and 2, installation of a slip stopper for integrating the new floor slab and the existing steel girder at the time of replacing the floor slab, Reinforcement can be performed simultaneously. For this reason, it is possible to further shorten the construction period for replacing the floor slab and reduce the cost.

1 is a vertical sectional view showing a state in which an upper structure of a bridge 1 to which a steel girder reinforcement method according to an embodiment of the present invention is applied is cut along a vertical plane orthogonal to a bridge axis direction. It is process explanatory drawing which shows the existing floor slab removal process of the reinforcement method of the steel girder which concerns on embodiment of this invention. It is process explanatory drawing which expands the upper flange vicinity of a steel girder, and shows the bolt hole drilling process of the reinforcement method of a steel girder same as the above. It is process explanatory drawing which shows the reinforcement steel plate joining process of the reinforcement method of a steel girder same as the above, (a) shows before joining, (b) shows after joining, (c) is a top view of a reinforcing steel plate.

  Hereinafter, a method for reinforcing a steel girder according to an embodiment of the present invention will be described with reference to the drawings.

  First, an existing bridge to which a steel girder reinforcement method according to an embodiment of the present invention is applied will be briefly described with reference to FIG. A steel concrete composite girder in which a steel girder made of I-shaped steel and a reinforced concrete slab are integrated as a bridge will be described as an example.

  FIG. 1 is a vertical cross-sectional view showing a state in which an upper structure of a bridge 1 to which a steel girder reinforcement method according to an embodiment of the present invention is applied is cut along a vertical plane orthogonal to a bridge axis direction. As shown in FIG. 1, the superstructure of the bridge 1 according to the illustrated embodiment includes a plurality of steel girders 2 made of I-shaped steel and an existing floor slab made of reinforced concrete placed on these existing steel girders 2. 3 and so on. The superstructure of the bridge 1 is a composite girder in which the existing floor slab 3 and the steel girder 2 are integrated with a stopper (not shown) protruding from the upper flange 20 of the steel girder 2.

   Further, in the upper structure of the bridge 1, a rail 4 made of reinforced concrete is formed at the end of the existing floor slab 3 in the width direction, and an asphalt pavement 5 is laid on the existing floor slab 3. The steel girder reinforcement method according to the embodiment of the present invention is preferably applied to the case where the existing floor slab 3 of such a bridge 1 is replaced with a new floor slab and is reinforced with an increase in the live load in the structural design. Is done.

(Existing floor slab removal process)
First, in the method for reinforcing a steel girder according to an embodiment of the present invention, an existing floor slab 3 and a steel girder 2 are separated by cutting a stopper of a composite girder (not shown), and as shown in FIG. The existing floor slab removal process which cuts and removes 3 to the predetermined | prescribed magnitude | size which can be lifted is performed. Drawing 2 is a process explanatory view showing the existing floor slab removal process of the reinforcing method of the steel girder concerning the embodiment of the present invention.

  Specifically, in this step, the existing floor slab 3 is cut into a predetermined size that can be lifted by a lifting machine, using a diamond cutter or a wire saw. Next, the edge of the floor slab and the steel girder are cut with a jack or the like. Then, using a mobile crane such as a roughing crane that is a lifting machine installed on the bridge 1 or on the road under the bridge 1, the existing floor slab 3 cut to a predetermined size is lifted to transport a vehicle such as a truck. Remove it and remove it. Finally, the main girder upper surface is cut off by leaving about 10 mm of gas or the like, and the steel girder upper surface is smoothed with a grinder equipped with a grindstone.

(Bolt drilling process)
Next, in the method for reinforcing a steel girder according to the present embodiment, as shown in FIG. 3, the reinforcing steel plate 6 is bolted to the upper flange 20 of the steel girder 2 exposed by removing the existing floor slab 3 in the previous process. A bolt hole drilling process is performed in which the bolt hole 21 for drilling is drilled with a drilling machine. FIG. 3 is a process explanatory view showing, in an enlarged manner, the vicinity of the upper flange 20 of the steel girder 2 in the bolt hole drilling process of the steel girder reinforcing method according to the present embodiment.

  Specifically, in this step, a bolt hole 21 for a high tension bolt (high-strength bolt) is used at a predetermined position of the upper flange 20 that does not interfere with a later-described stud gibber SJ using a drilling machine such as an electric drill (not shown). Drill a hole.

(Reinforced steel plate joining process)
Next, in the steel girder reinforcement method according to the present embodiment, as shown in FIG. 4, the high tension bolt HB is inserted into the bolt hole 21 of the upper flange 20 that has been drilled in the previous process, and is displaced in advance at the factory or the like. A reinforcing steel plate joining process is performed in which the reinforcing steel plate 6 to which the stopper is welded is bolted to the upper flange 20. FIG. 4 is a process explanatory view showing a reinforcing steel plate joining process of the steel girder reinforcing method according to the present embodiment.

  The reinforcing steel plate 6 used in this step is a structural steel plate having a width corresponding to the upper flange 20 of the existing steel girder 2 and a predetermined thickness suitable for reinforcing the design load increase. A steel plate having a length of 8 mm or more is used. Of course, it goes without saying that the width and thickness of the reinforced steel sheet according to the present invention can be appropriately changed according to the structural design.

  4 (a) and 4 (c), the reinforcing steel plate 6 is pre-implanted with a stud gibber SJ which is a slip stopper in a state where a lateral stress such as a bending stress does not act on the reinforcing steel plate 6. . Specifically, in an indoor facility or the like that can avoid wind and rain such as in a factory, the stud steel plate 6 is placed on a flat surface and a stud gun is used with a stud gun in a state where bending stress or the like does not act due to its own weight. (For example, about φ19-22) is pressed against the upper surface of the reinforcing steel plate 6 and stud-welded.

  Of course, the place where the reinforcing steel plate 6 is welded is not limited to an indoor facility such as a factory. If the place where the reinforcing steel plate 6 can be welded in a state where stress is not applied to the reinforcing steel plate 6 is placed outdoors, It doesn't matter. However, it is preferable to perform welding in an indoor facility because it prevents wind and rain and stabilizes the welding quality.

  Needless to say, the detent according to the present invention, which is welded to the reinforcing steel plate 6 in advance, is not limited to the stud gibber SJ, but may be another form of detent such as a horseshoe-shaped diver.

  Thus, in the method for reinforcing a steel girder according to the present embodiment, stud welding is performed in a state in which bending stress or the like does not act on the reinforcing steel plate 6, so that the steel girder 2 that is the main girder is bent due to thermal contraction. Can be suppressed. On the other hand, in the conventional slab replacement work, the stud gibber and other slip stoppers were directly welded to the existing steel girder from which the slab was removed. In other words, at the site where the bridge slab replacement work is performed, new displacement prevention welding was performed with the steel girder's own weight and the weight of the floor slab other than the removed part acting on the steel girder. For this reason, the compressive residual stress acted on the upper flange due to heat shrinkage, resulting in unexpected bending of the steel girder.

  In addition, in conventional floor slab replacement work, stud welding is directly performed on the top surface of the existing steel girder by on-site welding, so the top surface of the existing steel girder to which concrete fragments or the like have adhered is cleaned clean enough to allow stud welding. It had to be polished, and it took a lot of time and work.

  On the other hand, in the steel girder reinforcement method according to the present embodiment, the upper surface of the steel girder 2 can be cleaned to such an extent that the reinforcing steel plate 6 can be frictionally joined to the existing steel girder 2 with the high tension bolt HB. No need to polish up. For this reason, the working time required for cleaning can be shortened, and the labor cost required for stud welding or the like can also be reduced.

  In addition, in conventional floor slab replacement work, stud welding is performed directly on the upper surface of an existing steel girder, so an outer cable is fixed to the flange of the existing steel girder, and the girder is warped in the vicinity of the center. Or by reinforcing the steel girder with a plate. For this reason, it is difficult to reinforce the steel girders simultaneously with the replacement of the floor slabs, which takes time and increases labor costs.

  On the other hand, in the method for reinforcing a steel girder according to the present embodiment, the installation of a stud gibber SJ (non-displacement) for integrating a new floor slab and the steel girder 2 and the reinforcement of the steel girder 2 simultaneously. It can be carried out. For this reason, the work time for replacing the floor slab can be further shortened, and the labor cost can be reduced.

  Then, as shown in FIGS. 4B and 4C, in this step, the above-described stud dowel SJ is welded with the high tension bolt HB inserted into the bolt hole 21 using a tightening tool such as an impact wrench. The reinforced steel plate 6 is bolted to the upper flange 20. The steel girder reinforcement method according to this embodiment is finished by the end of this step.

  After that, a new floor slab such as a precast PC floor slab is placed, and the cotter around the stud gibber SJ as a composite portion is filled with a filler such as a non-shrink mortar to be integrated. Floor slab replacement work is completed. Of course, the new floor slab is not limited to the precast PC floor slab, it is a precast steel concrete composite floor slab, or a new RC floor slab in which concrete is placed by performing formwork, reinforcement, etc. as before. It goes without saying that it does not matter.

  According to the method for reinforcing a steel girder according to the present embodiment, the stud gibber SJ is welded to the reinforcing steel plate 6 in a state where no stress acts, and then bolted to the upper surface of the upper flange 20 of the steel girder 2 at the site. Residual stress due to heat shrinkage does not occur during plate replacement, and the steel girder is not assumed to bend.

  Further, according to the method for reinforcing a steel girder according to the present embodiment, the stud gibber SJ is welded in advance outside the site such as a factory in advance, and the reinforcing steel plate 6 is dry-bonded to the upper flange 20 instead of on-site welding. The work can be shortened and the period for closing the bridge 1 can be shortened. For this reason, the labor cost of floor slab replacement can also be reduced.

  Furthermore, according to the method for reinforcing a steel girder according to the present embodiment, the installation of the stud gibber SJ that integrates the newly installed floor slab and the steel girder 2 at the time of replacement of the floor slab and the necessary reinforcement of the steel girder 2 at the same time. It can be carried out. For this reason, it is possible to further shorten the construction period for replacing the floor slab and reduce the cost. Moreover, since the upper flange 20 of the steel girder 2 is thickened according to the structural design, the generated stress can be reduced.

  As mentioned above, although the reinforcement method of the steel girder concerning the embodiment of the present invention was explained in detail, all the embodiments mentioned above or illustrated showed only one embodiment actualized in carrying out the present invention. Absent. Therefore, the technical scope according to the present invention should not be limitedly interpreted by these.

1: Bridge 2: Steel girder 20: Upper flange 21: Bolt hole 3: Existing floor slab 4: Hand rail 5: Asphalt pavement (paving)
6: Reinforced steel sheet SJ: Stud gibber (stud with head)
HB: High tension bolt (high strength bolt)

Claims (2)

A method of reinforcing a steel girder when replacing an existing floor slab of a bridge with a new floor slab,
Place a reinforcing steel plate that reinforces the upper surface of the steel girder on a flat surface, and weld a stopper such as a stud gibber or horseshoe-shaped gibber in a state where stress does not act,
Thereafter, the reinforcing steel plate to which the slip stopper is welded in a state where no stress acts is joined to the upper surface of the steel girder from which the existing floor slab has been removed. The bridge is a composite girder,
When the existing floor slab is removed, the existing stopper is cut, and the reinforcing steel plate to which the stopper is welded in a state where no stress acts is applied to the upper surface of the steel girder from which the existing floor slab has been removed. The method for reinforcing a steel girder according to claim 1, wherein bolting is performed.

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