JP7115324B2 - Steel member reinforcement structure and reinforcement method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a reinforcing structure and reinforcing method for a steel member that supports a moving body.

Overhead cranes for transporting heavy objects are installed in buildings such as factories and warehouses. An overhead crane travels on rails laid on the upper surface of a steel beam (for example, H-beam) called a crane girder. Crane girders are subject to repeated stress as overhead cranes travel, and fatigue cracks may occur due to long-term use. If a crack occurs in the crane girder, the overhead crane cannot run, and the operation of the factory or the like is interrupted. Therefore, it is necessary to suppress the occurrence of the crack.

As described above, when the crane girder is made of H-beam steel, the cracks are mainly in the lower flange that receives tensile stress due to the running of the overhead crane, especially the welded part where the gusset plate and attached hardware are welded. tend to occur in the vicinity of In order to suppress the occurrence of cracks in the lower flange, conventionally, the stress generated in the H-section steel is reduced by providing a reinforcing member on the lower surface of the H-section steel. As a reinforcing member, it is known to use, for example, H-section steel or CT-section steel.

Further, Patent Document 1 discloses a structure using a PC cable as a reinforcing member. According to the structure disclosed in Patent Document 1, a prestress is introduced by arranging a PC steel strand inside an anchor plate welded to the lower surface of a crane girder and applying a tensile force to the PC steel strand. .

Further, Patent Document 2 discloses a configuration in which a carbon fiber sheet is adhered to the lower surface of the H-section steel as a reinforcing member. According to the structure disclosed in Patent Literature 2, a plurality of layers of carbon fiber material are superimposed in a stepped manner and attached to the portion of the member to be reinforced where the tensile force acts.

JP-A-1-268946 JP 2013-47446 A

According to the above-mentioned known technology and the technology disclosed in Patent Documents 1 and 2, by providing a reinforcing member on the lower surface of the H-section steel, tensile stress is generated in the lower flange of the H-section steel. It is possible to suppress the occurrence of bending deformation and suppress the occurrence of fatigue cracks.

However, according to these conventional reinforcing structures, although it is possible to suppress the occurrence of fatigue cracks in the H-section steel and extend the service life, it is not possible to eliminate the concern of the potential occurrence of fatigue cracks. That is, there is room for improvement in the reinforcing structure of the H-section steel.

The present invention has been made in view of the above circumstances, and more appropriately reduces the stress generated in the H-section steel as a crane girder compared to the conventional technology, and suppresses the occurrence of fatigue cracks in the H-section steel. intended to

The present invention for solving the above problems is a reinforcing structure for H-section steel that supports a moving body on the upper surface, wherein a reinforcing member is provided on the lower surface of the H-section steel, and the lower flange of the H-section steel includes: A slit is formed from the lateral end of the lower flange toward the web of the H-section steel.

According to the present invention, in addition to the conventional H-section steel reinforcement structure, that is, the construction of reinforcing members, by forming slits in the lower flange where tensile stress is generated, transmission of the generated tensile stress can be suppressed. . Thereby, it is possible to appropriately suppress the occurrence of fatigue cracks in the lower flange.

In addition, according to the present invention, since it is possible to appropriately reduce the concern that fatigue cracks will occur in the lower flange, it is possible to appropriately reduce maintenance costs such as inspection and repair of the crane girder.

A plurality of slits may be formed along the longitudinal direction of the lower flange.

The slits may be formed from both ends or one side end of the lower flange in the lateral direction across the web.

The reinforcing member may be composed of at least one member selected from H-section steel, CT-section steel, PC cables, and carbon fiber sheets.

The steel member may be a crane girder.

According to another aspect of the present invention, there is provided a method for reinforcing an H-section steel for supporting a moving body, wherein a reinforcing member is provided on the lower surface of the H-section steel, and a lower flange of the H-section steel is provided with a It is characterized by forming a slit toward the web of the H-section steel from the direction end.

A plurality of slits may be formed along the longitudinal direction of the lower flange.

The slits may be formed from both lateral ends of the lower flange with the web interposed therebetween.

The reinforcing member may be composed of at least one member selected from H-section steel, CT-section steel, PC cables, and carbon fiber sheets.

The steel member may be a crane girder.

ADVANTAGE OF THE INVENTION According to this invention, the stress which generate|occur|produces in H section steel as a crane girder can be reduced appropriately, and generation|occurrence|production of the fatigue crack to the said H section steel can be suppressed.

Fig. 2 is a plan view schematically showing the structure of a building provided with a pair of crane girders on which an overhead crane travels; It is a perspective view which shows the structure of a crane girder typically. It is an explanatory view explaining the principle of generation of cracks in the lower flange. FIG. 4 is a perspective view schematically showing cracks generated in a lower flange; It is a perspective view which shows the reinforcement structure of the conventional crane girder. It is explanatory drawing of the stress which generate|occur|produces in the conventional crane girder. It is a fatigue design curve diagram explaining the reinforcement structure of the conventional crane girder. It is a perspective view which shows typically the structure of the crane girder concerning embodiment of this invention. It is a top view which shows typically the structure of the crane girder concerning embodiment of this invention. It is explanatory drawing of the stress which generate|occur|produces in the crane girder concerning embodiment of this invention. It is a fatigue design curve diagram explaining the reinforcing structure of the crane girder according to the embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present specification and drawings, elements having substantially the same functional configuration are denoted by the same reference numerals, thereby omitting redundant description.

(Structure of Crane Girder)
FIG. 1 is a plan view schematically showing the structure of a building internally provided with a pair of girders on which an overhead crane travels. Moreover, FIG. 2 is a perspective view which shows the structure of a girder typically.

As shown in FIG. 1, the building 1 has a structure in which a plurality of frames 10, which are column-beam structures with frame surfaces, are arranged side by side in the longitudinal direction of the building. The frame 10 also has a Rahmen structure comprising a pair of pillars 11 and beams (not shown).

The building 1 is provided with a pair of girders 13 extending in the longitudinal direction of the building. A girder 13 is provided on the column 11 .

As shown in FIG. 2, the girder 13 has an H-shaped steel 20 as a main girder, a lower surface structure 30, an upper surface structure 31 and a back girder 32. As shown in FIG. The H-section steel 20 has a lower flange 21 , a web 22 and an upper flange 23 . The lower flange 21 and the lower surface structure 30 of the H-section steel, and the upper flange 23 and the upper structure 31 of the H-section steel are connected by welding via gusset plates 24 and 25, respectively.

The H-shaped steel 20 may be made of a steel material in which a flat plate is assembled into an H-shaped cross section by welding, for example.

(Occurrence of cracks in the crane girder)
As shown in FIG. 3, the girder 13 configured as described above receives a repeated load L as the overhead crane 12 travels, and when receiving the load L, the girder 13 is deformed into a downward convex shape. Due to such deformation, a tensile stress T and a compressive stress C are generated in the lower flange 21 and the upper flange 23 of the H-section steel 20 constituting the girder 13, respectively.

Here, if a repeated tensile stress T is generated in the lower flange 21 , fatigue cracks may occur due to long-term use of the overhead crane 12 . In particular, the welded portion of the gusset plate 24 connecting the lower flange 21 and the lower surface structure 30 is a site where fatigue cracks are likely to occur. That is, as shown in FIG. 4 , cracks X are likely to occur in the lower flange 21 starting from the point of contact 26 with the gusset plate 24 , and extend across the lateral direction (width direction) of the lower flange 21 toward the web 22 . Crack X progresses.

(Reinforcing structure of crane girder)
Therefore, in order to suppress the occurrence of such cracks X, a reinforcing member 40 is conventionally provided on the lower surface of the H-section steel 20 as shown in FIG. As the reinforcing member 40, for example, H-shaped steel, CT-shaped steel, PC cable, carbon fiber sheet, or the like is used.

FIG. 6 is a stress diagram showing the stress σ generated in the H-shaped steel 20 before and after the reinforcing member 40 is provided. FIG. 7 is a diagram of a fatigue design curve determined by the range of stress generated in the H-section steel 20 and the number of repetitions. In the fatigue design curve diagram shown in FIG. 7, the vertical axis indicates the stress range, and the horizontal axis indicates the number of repetitions. In addition, the solid line in the figure indicates the stress range in which the degree of cumulative fatigue damage D = 1.0. Cracks form. That is, the area on the left side (lower side) of cumulative fatigue damage D = 1.0 in the figure can be said to be the durable area of the H-section steel 20, and the area on the right side (upper side) can be said to be the damage area of the H-section steel 20. .

As shown in FIG. 6 , when the H-shaped steel 20 is not provided with the reinforcing member 40 , stress σ1 is generated in the lower flange 21 due to traveling of the overhead crane 12 . On the other hand, by providing the reinforcing member 40 on the lower surface of the H-section steel 20, the stress generated on the lowermost surface of the girder 13 is reduced to σ2. This is because the cross-sectional area of the main girder is increased by providing the reinforcing member 40 . In addition, the portion where the stress σ2 is generated can be moved downward, that is, the generated stress σ2 can be borne by the reinforcing member 40, thereby further reducing the stress generated in the lower flange 21 to σ3.

When the stress generated in the lower flange 21 decreases from σ1 to σ3 in this way, the number of repetitions increases until the cumulative fatigue damage degree D=1.0 is reached, as shown in FIG. That is, the life of the girder 13 is extended from Nr1 to Nr2 by reinforcing the H-section steel 20 as the main girder.

However, as shown in FIG. 7, although the service life of the girder 13 can be extended by providing the reinforcing member 40, further repeated use of the overhead crane 12 eventually reaches the service life Nr2 of the girder 13, and the lower flange 21 crack X occurs. That is, the fear of fatigue cracks occurring in the girder 13 cannot be eliminated.

(Embodiment according to the present invention)
Therefore, in this embodiment, the stress generated in the girder 13 is more appropriately reduced, and the occurrence of fatigue cracks is more appropriately suppressed. Desirably, the weld of the gusset plate 24 connecting the lower flange 21 and the lower surface 30 is stress-free.

8 and 9 are a perspective view and a plan view, respectively, schematically showing the reinforcing structure of the H-section steel 20 according to this embodiment.

As shown in FIG. 8 , the reinforcing structure for the H-section steel 20 according to this embodiment includes the reinforcing member 40 and slits 50 formed in the lower flange 21 . The slit 50 is formed from the lateral end of the lower flange 21 toward the web 22, that is, from the end of the gusset plate 24 on the same side as the welded portion toward the direction perpendicular to the extending direction of the web 22. ing.

Moreover, the slit 50 is formed, for example, in the vicinity of the welded portion of the gusset plate 24 where the crack X is likely to occur.

By forming the slits 50 in the lower flange 21 in this manner, transmission of the tensile stress T generated in the lower flange 21 can be suppressed. That is, conventionally, the stress generated in the lower flange 21 due to travel of the overhead crane 12 was transmitted along the longitudinal direction of the lower flange 21 . However, by forming the slits 50 in the lower flange 21 here, the transmission path of the stress is cut off, and the occurrence of the crack X can be suppressed.

FIG. 10 is a stress diagram showing the stress σ generated in the H-shaped steel 20 in the cross section (aa cross section in FIG. 9) where the slits 50 are formed. FIG. 11 is a fatigue design curve diagram of the H-section steel 20 according to this embodiment. In addition, σce shown in FIG. 11 indicates the critical termination stress, and when the stress acting on the girder 13 is lower than the critical termination stress σce, the girder 13 does not reach the fatigue limit.

As shown in FIG. 10, stress σ2 is generated on the lower surface of the girder 13 as the overhead crane 12 travels on the aa cross section. On the other hand, by forming the slits 50 in the lower flange 21 of the H-section steel 20, the transmission of stress is cut off, and no stress is generated in the slit 50 formation portion of the lower flange 21 (σ4=0). Alternatively, for example, by forming the slit 50 at least partially from the end of the lower flange 21 in the lateral direction, the generated stress can be reduced (σ4<σ3). That is, by forming the slits 50 in the lower flange 21 where the stress σ3 is conventionally generated, it is possible to at least reduce the transmission of the generated stress. When the generated stress is reduced in this way, the number of repetitions until the degree of cumulative fatigue damage D=1.0 is increased as described above, and the life of the girder 13 is extended.

At this time, when no stress is generated in the lower flange 21 (σ4=0) as described above, or when the generated stress σ4 is less than the discontinuation critical stress σce as shown in FIG. 11, the girder 13 never reaches the fatigue limit. That is, no crack X occurs in the lower flange 21 no matter how many times the overhead crane 12 travels. This is because the stress σ4 generated in the lower flange 21 is sufficiently smaller than the allowable durability of the girder 13, and the generated stress σ4 can be ignored.

According to the above embodiment, in addition to providing the reinforcing member 40 in the H-section steel 20, by forming the slit 50 in the lower flange 21, transmission of stress generated in the lower flange 21 is suppressed, thereby cracking. Generation of X can be suppressed. Moreover, when the stress generated by the slit 50 is reduced to the discontinuation limit stress or less, the crack X can be prevented from occurring.

Furthermore, by suppressing and preventing the occurrence of cracks X in the H-shaped steel 20 in this way, the cost required for maintenance such as inspection and repair of the girder 13 can be minimized.

In the above-described embodiment, the slit 50 is formed near the welded portion of the lower surface structure 30 where the crack X is likely to occur, but the slit 50 is not limited to this. If the slits 50 are formed at least in the lower flange 21 from the ends of the lower flange 21 in the lateral direction toward the web 22, the effect of inhibiting the transmission of the tensile stress T can be exhibited.

Further, as shown in FIG. 9, for example, it may be provided at a plurality of locations along the longitudinal direction of the lower flange 21, or may be provided at both ends or one side in the short direction of the lower flange 21 with the web 22 interposed therebetween. It may be configured to be formed from the ends. Further, at this time, by arranging the slits 50 symmetrically in the longitudinal direction of the lower flange 21 or sandwiching the web 22, it is possible to suppress bias in the generated stress.

In the above description, the slit 50 is formed in the lower flange 21 as a reinforcing structure for suppressing the occurrence of fatigue cracks. As a result, it can also be used as a repair method for the H-section steel 20 .

In this case, by forming at least the slit 50 in the vicinity of the site where the fatigue crack occurs, it is possible to suppress the transmission of stress and the propagation of the fatigue crack.

Although the embodiments of the present invention have been described above, the present invention is not limited to such examples. It is obvious that a person skilled in the art can conceive various modifications or modifications within the scope of the technical idea described in the claims, and these are also within the technical scope of the present invention. be understood to belong to

For example, in the above embodiments, as an example of H-section steel in which fatigue cracks occur, a crane girder that supports crane travel has been described. Not limited.

INDUSTRIAL APPLICABILITY The present invention is useful for reinforcing H-beams, and particularly for reinforcing crane girders.

1 Building 12 Overhead Crane 13 Girder 20 H-shaped Steel 21 Lower Flange 22 Web 23 Upper Flange 24 Gusset Plate 40 Reinforcing Member 50 Slit C Compressive Stress T Tensile Stress X Crack σ Stress

Claims (10)

A reinforcing structure of H-shaped steel that supports a moving body on the upper surface,
A reinforcing member is provided on the lower surface of the H-shaped steel,
A reinforcing structure for an H-section steel, wherein a slit is formed in a lower flange of the H-section steel from a lateral end of the lower flange toward a web of the H-section steel. The reinforcing structure for H-section steel according to claim 1, wherein a plurality of said slits are formed along the longitudinal direction of said lower flange. 3. The reinforcing structure for H-beam steel according to claim 1, wherein said slits are formed from both ends or one side end of said lower flange in the transverse direction across said web. The reinforcing member according to any one of claims 1 to 3, characterized in that it is composed of at least one member selected from H-section steel, CT-section steel, PC cables, and carbon fiber sheets. H-beam reinforcement structure. The H-section steel reinforcement structure according to any one of claims 1 to 4, characterized in that the H-section steel is a crane girder. A method for reinforcing an H-section steel that supports a moving body, comprising:
A reinforcing member is provided on the lower surface of the H-shaped steel,
A method for reinforcing an H-section steel, comprising forming a slit in a lower flange of the H-section steel from a lateral end of the lower flange toward a web of the H-section steel. The method for reinforcing H-section steel according to claim 6, wherein a plurality of said slits are formed along the longitudinal direction of said lower flange. 8. The method of reinforcing an H-section steel according to claim 6, wherein the slits are formed from both ends of the lower flange in the lateral direction across the web. The reinforcing member according to any one of claims 6 to 8, characterized in that it is composed of at least one member selected from H-shaped steel, CT-shaped steel, PC cables, and carbon fiber sheets. Reinforcement method of H-shaped steel. The method for reinforcing H-section steel according to any one of claims 6 to 9, wherein the H-section steel is a crane girder.

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