JP5550955B2 - A method to prevent flying salt from adhering to the girder of the girder bridge, box girder bridge and girder bridge - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a method for preventing adhesion of flying salt to girder bridges, box girders and girder bridges having girders with low flying salt content, and particularly to the formation of iron rust by adhesion of flying salt. The present invention relates to a material suitable for use in a steel bridge that shortens the life.

  In recent years, aged deterioration of steel structures has become obvious, and an increase in maintenance and repair costs has become a problem. The aging of steel bridges is caused by corrosion and fatigue. Especially in steel girder bridges and box girder bridges, the biggest factor that hinders the life of the bridge is corrosion due to iron rust, which promotes the generation of iron rust. Iron rust is likely to occur on the bridge girder and box girder of the bridge constructed near the coast where there is a lot of salt.

  FIG. 7 schematically shows the flow of wind blowing on the two main girder bridges built near the coast. In a general girder bridge composed of a floor slab 1 and a plurality of girder 2 composed of a web 3 and a flange 4, the wind 6 flowing on the lower surface of the girder 2 is of the girder 2 located at the end of the bridge on the windward side. Since peeling occurs at the lower flange 4, the negative pressure on the wind surface of the girder 2 is increased, and a wind flow 7 is generated between the girder 2 and 2. For this reason, the girder 2, particularly the inner surface thereof, tends to generate iron rust due to the adhesion of salt carried with the wind. In addition, although salt content adheres also to the outer surface of the girder 2 located in the bridge side edge part of a windward side, since this part is washed by rain, it is hard to generate | occur | produce iron rust.

  As a rust prevention measure for such a girder bridge, generally, a method of applying a paint or a method of using a weather-resistant steel material for a bridge member is employed. In particular, in the method using weathering steel, protective rust enriched with its component elements such as copper, phosphorus and chromium is formed on the surface of the steel, so it is said that it can withstand use for several decades without painting. ing.

  However, in the method of applying paint, it is necessary to repaint every about 20 to 30 years, and there is a problem that it takes a lot of cost including temporary scaffolding for that, and the method of using weathering steel However, there is a problem that protective rust is not formed and sufficient weather resistance cannot be obtained for the girder bridge along the coast where there is a lot of incoming salt and the girder bridge where snow melting salt is sprayed to prevent road freezing. there were.

  In order to solve such a problem in Patent Document 1, the present inventors proposed changing the flow of wind blown to the steel bridge to suppress the amount of incoming salt attached to the girder. 8 (a) and 8 (b) are diagrams for explaining the steel bridge according to the invention described in Patent Document 1 and the effect thereof. A plurality of holes 5 are provided in the lower end portion of the web 3 (FIG. 8 (b)), A part of the separated flow 6 flowing on the lower surface of 2 is allowed to pass through the hole 5 to reduce the pressure difference between the wind surface of the eaves 2 and the wind surface, thereby making it difficult for the wind to be caught between the eaves 2 and circulating flow. 8 (airflow circulating between the girders) is formed (FIG. 8A). Thereby, it aims at suppressing the inflow of the salt to the inner surface side of the girder 2 and suppressing the generation of iron rust.

Japanese Patent Laid-Open No. 2000-240009

  However, when the present inventors reproduced the airflow around the girder and the state of salt adhesion in the girder by wind tunnel experiments in order to further improve the method for preventing the girder's flying salt adhesion prevention described in Patent Document 1, It has been found that formation may not necessarily contribute to a reduction in the amount of deposited salt.

9 and 10 are the results of a wind tunnel experiment in which the flow around the cross section of the girder is visualized by smoke using a model of a steel bridge with two main girders. In these figures, (a) is an air flow (separated flow 6 and circulating flow 8). The figure which showed typically the behavior of the sea salt particle | grains (salt content) 11 and (b) show the imaging | photography result which visualized the airflow in a girder with white smoke.

  FIG. 9 shows a case where the flow from the separation point a is relatively large and peels downward to form a separation flow 6, and the flow is strong in the girder. FIG. 10 shows a plate material (separation control plate) in the vicinity of the lower flange 4. 12) is installed, and the flow from the peeling point a is made to follow the vicinity of the lower surface of the beam 2.

  In FIG. 9, peeling from the peeling point a is strong (a), and a lot of smoke is observed in the beam (b). When the peeling control plate 12 was installed in the vicinity of the lower flange 4 as shown in FIG. 10 (a), no clear smoke was observed in the girder, and the result of a significant reduction in smoke penetration was observed (b).

  These results show that when the peeling control plate 12 is installed as in the case of FIG. 10, the adhesion of salt to the inner surface of the girder may be hindered, but a similar wind tunnel experiment with a diameter of about 10 μm is performed. The result of flying a large number of floating particles in the wind tunnel was different.

  FIG. 11 shows the result of capturing particles with the double-sided tape installed in the model beam, contrary to the expectation obtained from the observation situation of smoke in the visualization experiment, and the case of FIG. In the case of FIG. 10 (condition 2) in which no smoke is observed in the girders, the total number of particles adhering in the girders is larger than in (condition 1). The amount of particle scattering is the same.

  The reason for this is that even if smoke is floating in the beam, it does not necessarily adhere to the inner surface of the beam. As shown in FIG. It may be difficult to observe, and in that case, salt may be circulated in the girders by the circulating flow, and adhesion to the girders may be promoted by centrifugal force.

  Accordingly, the present invention has an object to provide a method for preventing adhesion of flying salt to a girder or box girder, and a girder bridge and box girder bridge having a girder with less adhesion of flying salt based on the above experimental results. .

The object of the present invention can be achieved by the following means.
1. A girder bridge having a plurality of girder and provided with means for decelerating the flow velocity of a circulating flow between adjacent girder.
2. 2. The girder bridge according to 1, wherein the means is a member provided between a girder or adjacent girder and having a structure for reducing the flow velocity while allowing the circulating flow to pass therethrough.
3. 2. The girder bridge according to claim 1, wherein the means is ancillary equipment of a girder bridge such as an inspection path or a transport pipe provided at a position where the shearing force of the lower surface separation flow that generates a circulating flow is weakened.
4. A box girder bridge characterized in that it is a box girder instead of the girder of the girder bridge described in any one of 4.1 to 3.
5. A method for preventing the deposition of flying salt on the girder bridge girder having a plurality of girder or box girder, and circulating in advance between the girder or girder so that the flow velocity of the circulating flow generated between the plurality of girder is reduced. A method for preventing adhesion of flying salt to a girder bridge girder characterized by providing a flow deceleration means.

  INDUSTRIAL APPLICABILITY According to the present invention, it is possible to obtain a steel bridge in which the amount of incoming salt on the girder and box girder is small and corrosion due to iron rust is small, which is extremely useful industrially.

The typical sectional view of the girder bridge (steel bridge) concerning one example of the present invention. Schematic sectional view of a girder bridge (steel bridge) according to another embodiment of the present invention Schematic sectional view of a girder bridge (steel bridge) according to another embodiment of the present invention The schematic diagram which shows the effect of the girder bridge (steel bridge) which concerns on one Example of this invention shown in FIG. The schematic diagram which shows the effect of the girder bridge (steel bridge) which concerns on the other Example of this invention shown in FIG. The schematic diagram explaining the airflow in the conventional girder bridge (steel bridge) and its periphery. The figure which shows typically the flow of the wind sprayed on the conventional 2 main bridge girder bridge erected near the coast. It is a figure explaining the 2 main bridge girder bridge concerning the invention of patent documents 1, (a) is a figure showing typically the flow of the wind which blows the 2 main bridge girder bridge concerning the invention of patent documents 1, and (b) is patent document 1. The structure of the 2 main bridge girder bridge according to the invention of FIG. The result of a wind tunnel experiment in which the flow around the cross section of a girder is visualized with smoke using a model of a steel bridge with two main girders, (a) schematically shows the behavior of air current (separated flow, circulating flow) and sea salt particles (salinity). The figure shown in figure, (b) is the figure which showed the imaging | photography result which visualized the air flow in a girder with white smoke. (A) shows the results of a wind tunnel experiment in which the flow around the girder section is visualized by smoke using a model of a steel bridge with two other main girders. (A) shows the behavior of airflow (separated flow, circulation flow) and sea salt particles (salt) The figure shown typically, (b) is the figure which showed the imaging | photography result which visualized the airflow in a girder with white smoke. The figure which shows the number of particles adhering to the girder web inner surface by the experiment shown in FIG. 9, FIG.

  The present invention is characterized by weakening the motion of the circulating flow between adjacent girder and box girder by wind blown on the girder bridge and box girder bridge, or suppressing the occurrence of the circulating flow itself.

  FIG. 1 is a schematic cross-sectional view of a girder bridge (steel bridge) according to an embodiment of the present invention. The figure shows a structure in which a circulating flow is passed between adjacent girder 2 and 2 while the flow rate is reduced in a girder bridge comprising a floor slab 1 and a plurality of girder 2 composed of a web 3 and a flange 4. The case where the member 9 which has is arrange | positioned on the lower surface of the floor slab 1 used as the center between the left and right side beams 2 and 2 is shown.

  The member 9 is preferably provided with a gap portion for allowing the circulation flow to pass through and an obstacle portion for weakening the flow velocity, and further having a rigidity that does not cause deformation due to the circulation flow, and a wire mesh or a perforated plate (thin steel plate) can be used. .

  FIG. 4 schematically shows the effect when the member 9 is provided in the flow (FIG. 6) of the circulating flow 8 of the conventional girder bridge. In the figure, reference numeral 7 indicates the flow of the circulating flow 8, and reference numeral 11 indicates the flying sea salt particles. Since the circulating flow 8 reduces the velocity of the flow 7 due to the fluid resistance of the member 9 and the flow field is disturbed and diffuses, the circulating flow 8 is separated from the inner wall of the spar 2 and the adhesion of salt is prevented.

  The attachment position of the member 9 is preferably determined by confirming the position that obstructs the circulation flow in the wind tunnel experiment using the model described above. In the case of an existing girder bridge, the installation position may be determined from the state of adhesion of flying salt on the inner wall of the girder and the occurrence of iron rust.

  FIG. 2 is a schematic cross-sectional view of a girder bridge (steel bridge) according to another embodiment of the present invention, and shows a case where the member 9 is attached to the inside of the web 3 which is ½ of the height of the girder 2.

  FIG. 6 shows a case where the flow from the peeling point (the lower left end of the flange 4 of the left spar 2 in the figure) tends to follow the lower surface of the spar 2. When the flow velocity of the separation flow 6 on the lower surface is close to the lower surface of the girders and the flow velocity is high, a strong circulation flow 8 is generated between the left and right girders 2 and 2 due to the shearing force of this flow. To attach to the inner wall surface of the girder 2.

  3 is a schematic cross-sectional view of a girder bridge (steel bridge) according to another embodiment of the present invention, and FIG. 5 shows the effect of the structure shown in FIG. The case where the inspection path 10 which is incidental equipment of a girder bridge is provided at a position where the shear force of the separated flow 6 is weakened (near the lower surface of the girder where the shear force is considered to be transmitted) is shown. Since the speed of the flow 7 of the circulating flow 8 becomes slow and the centrifugal force decreases, the adhesion of salt is prevented. Instead of the inspection path 10, a transport pipe as ancillary equipment for the girder bridge may be used. In addition, you may provide the member 9 so that the effect which provided the test | inspection path 10 may be improved more.

  In the above description, the girder bridge has been described as an example, but the present invention can also be applied to a box girder bridge and has the same effect.

DESCRIPTION OF SYMBOLS 1 Floor slab 2 Girder 3 Web 4 Flange 6 Separation flow 7 The flow of the wind wound between the girder or the flow of the circulation flow 8 Circulation flow 9 Member 10 Inspection path 11 Sea salt particle
12 Peeling control board

Claims (6)

A鈑桁bridge having a plurality of鈑桁, while passing through the circulation flow produced between adjacent 鈑桁,鈑桁bridge having means for decelerating the flow rate of it.   2. The saddle bridge according to claim 1, wherein the means is a member that is provided between the spars or adjacent spars, and has a structure for reducing the flow velocity while allowing the circulating flow to pass therethrough. The girder bridge according to claim 1 or 2, wherein the means is a wire mesh or a perforated plate.   The girder bridge according to claim 1, wherein the means is ancillary equipment of a girder bridge such as an inspection path or a transport pipe provided at a position where the shearing force of the lower surface separation flow that generates a circulating flow is weakened.   A box girder bridge, wherein a box girder is used instead of the girder of the girder bridge according to claim 1. A method of preventing flying salt from adhering to a girder bridge girder having a plurality of girder or box girder, wherein the flow velocity of the circulating flow generated between the plurality of girder is reduced in advance , between the girder or girder , A method for preventing the adhering salt from adhering to the girder of the girder bridge, characterized in that a circulating flow decelerating means for decelerating the flow velocity of the girder bridge is provided.