JP2005133535A - Snow-fall protection fence and bridge equipped with it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent an accident due to snow fall by avoiding high dense and heavy snow/ice lumps from falling from an upper chord member of a bridge without requiring such maintenance work as snow removal. <P>SOLUTION: A snow-fall protection fence 11 having a lattice with 120 mm grid intervals is set up at an end part of the long side direction of an upper lateral bracing 10b of the bridge, and a water treatment plate 12 is mounted in a space between the snow-fall protection fence 11 and the upper lateral bracing 10b. Although snow above the water treatment plate 12 passes through the lattice and falls down, its density is low because of the fact that the size of the falling snow lump is smaller than the interval of the lattice and exists in the higher clouds. The compressed snow staying lower than the water treatment plate 12 and an ice plate at the very bottom where water melted from a snowcap is frozen and attached do not fall from the upper lateral bracing 10 owing to the water treatment plate 12. Since the water melted from the snow cap does not hang down from the upper lateral bracing 10b owing to the water treatment plate 12, an icicle is not formed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a technique for avoiding the occurrence of an accident due to falling snow from the upper chord material of a bridge without requiring maintenance work.

  In snowy areas, there have been incidents of damage to vehicles and the like due to snowfall and snow accretion on the upper chord material of bridges, which fell as snow ice blocks. A conventional measure is to prevent snow from falling on the upper chord material in a low density state before it becomes a snow and ice lump so as to prevent damage to traffic vehicles and the like even if snow falls. Any of the methods for that purpose cannot eliminate work such as snow removal completely, and there is a problem that costs for maintenance are required.

  On the other hand, although it is assumed to be applied particularly to the opening of a building or a tunnel, a technique for preventing snowfall itself is proposed instead of aiming for early snowfall (for example, patents). References 1 to 3). In the techniques of these Patent Documents 1 to 3, an attempt is made to prevent the occurrence of snowfall by preventing the formation of snowfall at the opening of a building or tunnel by a lattice-shaped snowfall prevention body (net plate).

Japanese Utility Model Publication No. 1-26822 JP 2002-147061 A JP 2002-129777 A

  However, in the techniques of Patent Literatures 1 to 3, the lattice spacing of the snow scum prevention body (net plate) is very narrow (for example, 2 mm to 8 mm: Patent Literature 1, see page 23, left line on page 1). The snow accumulated outside falls early, but due to the viscoelastic nature of the snow, the snow accumulated inside the snow ridge forming end stays inside without falling. That is, the inside of the snow jar forming end is filled with snow almost without any gap up to the position of the snow candy prevention body.

  Here, if the snowfall prevention body is not high enough, if the amount of snowfall becomes very large due to a large amount of snowfall over a long period of time, it will easily exceed the height of the snowfall prevention body. It becomes. In this case, since the snow scum prevention body is filled with snow almost without any gap, there is a great risk that a snow squirt will be formed beyond the upper end of the snow sack prevention body. In addition, when a very large amount of snow falls, there is a risk that a snowpack with a relatively high density that has been compressed is formed. For this reason, there has been a problem that, when there is a large amount of snowfall in a short period of time, a snow mass with a relatively high density will fall unless the snow removal operation is performed manually.

  Moreover, in the techniques of Patent Documents 1 to 3, it is intended to completely prevent snow from falling outside the snow scum prevention body. On the other hand, if the inside of the snow scum prevention body is inclined or the snow accumulated inside the snow sack prevention body receives an external force such as wind, the entire snow piled there slides toward the outside of the snow sack prevention body. Sometimes. In particular, when there is a large amount of snowfall and the like, if it is intended to completely prevent the slidable snow from falling to the outside, a considerable strength is required for the material and attachment of the snow bag preventer. If sufficient strength is obtained, the selection range of materials and attachment methods is limited. On the other hand, if sufficient strength is not obtained, there is a problem in that the installation location of the snow bag prevention body is limited. .

  By the way, unlike buildings and tunnel openings that are supposed to apply the techniques of Patent Documents 1 to 3, the entire bridge is designed aesthetically so as to harmonize with the surrounding landscape. ing. For this reason, if an excessively large device is laid as a device for preventing snowfall, the landscape may be damaged. In addition, some bridges are quite large, and it is difficult for people to enter the upper chords such as buildings and tunnel openings that are supposed to apply the techniques of Patent Documents 1 to 3. It ’s not easy. For this reason, it has been desired to realize almost complete maintenance-free operation.

  The present invention provides a snowfall prevention fence for avoiding the occurrence of an accident due to snowfall by preventing a snow mass with high density and weight from falling from the upper chord material without requiring maintenance work such as snow removal, and the like. The purpose is to provide a bridge.

  In order to achieve the above object, a snowfall prevention fence according to a first aspect of the present invention is attached to an open end of an upper chord member of a bridge having an inclination of 0 ° to 45 ° with respect to a horizontal plane, and at least the upper chord member A grid having a thickness of 5 mm to 20 mm is formed at an interval of 30 mm to 120 mm so as to form an angle of 45 ° to 90 ° with the upper surface of the upper chord and the length from the upper surface to the upper portion of the upper chord material is in the range of 100 mm to 400 mm It has the grating | lattice part set to (5).

  When snow falls on the upper chord material of the bridge to which the above snowfall prevention fence is attached, the snow can be elastically destroyed when a large force is applied in a short time. Here, since the lattice spacing is at least 30 mm, small snowflakes caused by elastic fracture can be snowed early before being compressed to increase density. If it is made to snow with small snowflakes with such a low density, there is no risk of damage even if it collides with a vehicle or the like passing through a bridge.

  On the other hand, the snow remaining on the upper surface of the upper chord material without falling snow early increases the bonding force between the snow particles, and attempts to plastically deform by a long-term small force such as gravity or wind force. At this time, the force acting on the snow canopy is blocked by the lattice, so that the snow can be prevented from falling after being compressed and becoming dense. Even if snow canopy passes through the gaps in the lattice, the size of the falling snow mass is reduced to a range of 30 mm to 120 mm, so there is no danger to vehicles traveling through the bridge. In addition, it is possible to prevent the ice plate falling at the lowest part of the snow-covered snow and having the highest density by the lattice.

  In this way, the above snowfall prevention fence allows the snow covered snow to fall in a state that does not pose a danger, and prevents the fall of snow and ice blocks that have grown so as to cause danger due to the fall, and maintenance work such as snow removal. It can be done without doing it. Moreover, the growth of snow ice blocks can be suppressed by dropping the snow cover as much as possible without causing danger.

  In addition, the height of the upper chord material of the bridge is generally stronger than the ground surface, and the snow can be dropped as early as possible with as little snow as possible. A fence with a height of about enough can cope with it. Many bridges are designed to be in harmony with the surrounding landscape, but if the height of the snowfall prevention fence is this level, it will be sufficiently small compared to the size of the bridge. Therefore, the appearance of the bridge is not impaired. Even if a snowfall caused by snow accumulation exceeding the height of the fence falls, the density is small, and considering the height of the bridge, it collapses to a certain size during the fall, so there is no danger.

  In the snowfall prevention fence according to the first aspect, it is preferable that the vertical grids are formed at intervals of 30 to 60 mm.

  By making the vertical lattice spacing as fine as this, the flow path of water generated by melting from the snow can be dispersed, and the growth of ice pillars can be suppressed.

  In the snowfall prevention fence according to the first aspect, the upper chord member has an upper surface between the open end portion of the upper chord member and the lattice portion of the upper chord member in a range of 30 mm to 100 mm. It is preferable that a plate having an angle of 45 ° to 90 ° is formed.

  By forming such a plate, it is possible to prevent the water generated by melting from the snow from dripping from the upper chord material, so that the growth of icicles can be suppressed almost completely. In addition, this plate can completely suppress the fall of the ice plate that occurs at the bottom of the snow cover.

  In the snowfall prevention fence according to the first aspect, the lattice portion is further formed with a lattice having a thickness of 20 mm or less at an interval of 30 mm to 120 mm in a substantially parallel direction to the open end portion of the upper chord material. Preferably it is.

  The snow piled on the upper chord has a layered structure because the snow falling at the same time has the same quality. By providing a grid in a direction substantially parallel to the open end of the upper chord material, different layers of snow can be easily separated, and the size of snow falling through the gaps in the grid can be reduced. . Thereby, even if the snow lump that has fallen through the gap of the lattice collides with a vehicle or the like passing through the bridge, it can be prevented from causing great damage.

  The bridge according to the second aspect of the present invention is characterized in that the snowfall prevention fence according to the first aspect is attached to the end portion of the upper chord material.

  In order to achieve the above object, a snowfall prevention fence according to the third aspect of the present invention is provided at an attachment end of the main tower with a thick cable connecting the main tower and the girder of the cable-stayed bridge. It is attached, and has a grating | lattice part by which the grating | lattice was formed at the space | interval of 50 mm-150 mm at least in the substantially perpendicular direction with the extending direction of the said cable.

  The snow canopy on the cable of the cable stayed bridge can be almost removed with a scraper, but the snow can not be removed because the scraper does not reach the thickened end of the main tower. Can not. By attaching the above snowfall prevention fence to this part, it was possible to make the snow on the cable attachment end snow as early as a small piece of snow with low density, and the density increased without falling early. There is no formation of snow leopards from snow covered snow, and no snow falls. In addition, the lattice formed in a direction substantially perpendicular to the extending direction of the cable acts on snow of different snow quality, and the effect of preventing snow fall can be sufficiently exhibited.

  In the snowfall prevention fence according to the second aspect, it is preferable that a lattice in a direction substantially parallel to the extending direction is further formed in the lattice portion at an interval greater than or equal to the interval between the lattices in the vertical direction.

  In this case, since the force acting on the snow can also be blocked by the grid formed in a direction substantially parallel to the cable extension direction, the snow can overhang more effectively from the gap of the grid. Will be able to.

  A bridge according to the fourth aspect of the present invention is characterized in that the snowfall prevention fence according to the second aspect is attached to an end of the cable stayed cable bridge attached to the main tower. .

  According to the present invention, the snow canopy on the upper chord material of the bridge can be dropped early as a low-density snow piece, and can be prevented from falling when the density is increased without falling early. Can be avoided. To obtain this effect, maintenance work such as snow removal is not necessary.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a partial perspective view of a Nielsen Rose bridge to which a snowfall prevention fence according to an embodiment of the present invention is applied. As shown in the drawing, the long side direction end portion of the upper horizontal structure 10b in the upper chord member 10 of the Nielsen Rose bridge 1 is not connected to the main structure 10a or the like and is in an open state. A snowfall prevention fence 11 is attached to the end in the side direction. For example, when the Nielsen Rose bridge 1 is used as an expressway, a vehicle or the like passes through the lower part of the upper horizontal structure 10b.

  The angle formed by the upper surface of the upper horizontal structure 10b with respect to the horizontal plane is in the range of 0 ° to 45 ° (depending on the location). When the angle formed by the upper surface of the upper horizontal structure 10b with respect to the horizontal plane is greater than 0 °, the attachment side of the snowfall prevention fence 11 has a lower inclination.

  Here, it is assumed that no road is formed in the lower part of the main structure 10a of the Nielsen Rose Bridge 1 and no vehicle or the like is passed, so the snowfall prevention fence 11 is not attached, but the lower part of the main structure 10a. In addition, when there is traffic of a vehicle or the like, a snowfall prevention fence 11 is also attached here. Although the entire structure is not shown in the figure, the Nielsen Rose Bridge 1 is installed in a snowy area, and the length is about 200 m, the width is about 16 m, and the height to the top is 21 m. It is about.

  FIG. 2 is a diagram showing in detail the configuration of the snowfall prevention fence 11 of FIG. The snowfall prevention fence 11 is made of metal, wood, or the like. A lattice portion 11 a is formed on the upper part of the snowfall prevention fence 11. The thickness of the member which comprises the grating | lattice part 11a is about 5 mm-20 mm. The lattice portion 11a is formed by forming three lattices in the vertical direction and 10 in the horizontal direction at an interval of 120 mm vertically and horizontally for each snowfall prevention fence 11, and the overall lateral width is 1200 mm (length). Is measured with reference to the center of the member constituting the lattice portion 11a (the same applies hereinafter). In the fence attached to the end portion of the upper horizontal structure 10b, the horizontal direction may be as small as 1200 mm.

  The snowfall prevention fence 11 is attached by a bolt 11b so as to be substantially perpendicular to the upper surface of the upper horizontal structure 10b. When the length of the upper horizontal structure 10b is insufficient, a plurality of snowfall prevention fences 11 are connected by bolts 11c. The snowfall prevention fence 11 is fixed at a position where the height from the upper surface of the upper horizontal structure 10b to the upper end of the lattice portion 11a is 330 mm, and at a position where the gap at the end of the upper horizontal structure 10b is within 150 mm. The At this attachment position, the constituent surface of the lattice portion 11a is substantially perpendicular to the upper surface of the upper horizontal structure 10b.

  Although it is possible to attach only the snowfall prevention fence 11 to the end of the upper horizontal structure 10b, the inner side of the lattice part 11a of the snowfall prevention direction fence 11 and the end in the long side direction of the upper horizontal structure 10b A water treatment plate can be further attached to the. FIGS. 3A and 3B are views showing the configuration and attachment state of the water treatment plate. FIG. 3A is a view seen from the attachment side of the snowfall prevention fence 11, and FIG. 3B is a cross-sectional view in the front-rear direction of FIG. In Fig.3 (a), the water treatment plate 12 is shown by the net.

  As shown in the figure, the water treatment plate 12 is formed of a metal plate having a thickness of about 1 mm to 3 mm, and is provided with bolts 12b at positions on the inner side of the lattice portion 11a at the end in the long side direction of the upper horizontal structure 10b. It is attached. The length from the upper surface of the upper chord material 10b to the upper part of the water treatment plate 12 is about 90 mm. The water treatment plate 12 is also substantially perpendicular to the upper surface of the upper horizontal structure 10b.

Next, the operation of the snowfall prevention fence 11 will be described. If there is snowfall in the area where the Nielsenrose bridge 1 is installed, snowfall and snowfall on the upper chord material 10 (collectively these are simply called snowfall) occur. The snow immediately after falling is 90% or more occupied by air, and its density is very low at 0.05 to 0.1 g / cm ³ . In addition, the individual snow particles of the snow covered with each other are also bonded by a sintering phenomenon at a contact point with each other, and a three-dimensional network structure is formed. However, since the snow quality varies depending on the time of falling, different snow types of snow are deposited in a layered structure.

  As will be described below, when a strong force is applied to the snow covered with snow before it grows into a snowy ice block in a short time due to strong winds or the like, the snow is subject to elastic fracture. Of the snowflakes generated by the elastic fracture, the relatively small snowflakes are further subjected to wind force, and pass through the lattice gap of the lattice portion 11a and fall to the lower portion of the upper horizontal structure 10b. This snowflake is still in a low density, small size and light weight, so that even if it falls from the upper frame 10b or hits a vehicle passing through the lower part, it will damage the vehicle. It should not be a shock

  A small force is applied for a long time to the snow covered with snow, which has become a small snowflake and does not fall from the gap between the lattices, due to the weight of the snow itself or the relatively weak wind force. For such a force, the snow cap is plastically deformed. Here, the direction of the force acting on the snow covered, that is, if the upper surface of the upper horizontal structure 10b is inclined, the snow covered with the snow is projected downward in the direction of the slope, and if receiving the force of the wind, Try to transform.

  Here, when the snow is about to deform in the direction in which the snowfall prevention fence 11 is attached, the lattice formed in the lattice portion 11b, particularly the lattice formed in the vertical direction, has an appropriate interval of 120 mm. For this reason, the force acting on the snow particles is dispersed in the adjacent snow particles to prevent the snow from falling as a lump. However, although snow gradually protrudes from the gaps in the lattice, it prevents the falling snow mass from becoming larger than the lattice interval. Also, the horizontal grid acts to peel off snow layers of different quality and to reduce the size of the snow mass falling through the grid spacing.

  The snow at the bottom melts away by heat conduction when the temperature of the upper surface of the upper horizontal structure 10b is positive, but freezes again to form an ice plate when the temperature falls. This ice plate is also prevented from falling to the lower portion of the upper horizontal structure 10b by the vertical lattice of the lattice portion 11a. Furthermore, as the snow caps melt from the vicinity of the lattice, a flow path of the melted water is generated in the vicinity of each lattice. As a result, the water that has melted due to the heat conduction on the upper surface of the upper horizontal structure 10b also flows in a distributed manner in the flow paths in the vicinity of each lattice, so that the water dripping from the gap between the upper horizontal structure 10b and the lattice portion 11a. It is possible to suppress the growth of icicles formed by freezing again.

  Further, when the water treatment plate 12 is attached, the ice plate can be completely prevented from falling. Moreover, since it is possible to prevent the water generated by melting from the snow from dripping from the gap between the upper horizontal structure 10b and the lattice portion 11a, the growth of icicles can be suppressed almost completely. That is, the water treatment plate 12 completely suppresses the most dense ice plate or ice column from falling from the upper horizontal structure 10b.

  In addition, when the inclination of the upper horizontal structure 10b and the wind force are small and the force applied to the snow is weak, the snow near the lattice, especially the snow that touches the lattice, is easily melted by the heat radiation from the lattice. , Sublimation will evaporate. Since the snow is melted and sublimated and evaporated in this way, a gap is formed between the lattice and the snow, so that the weight of the snow is not easily applied to the snow fall prevention fence 11.

  In addition, when there is a large amount of snowfall in a short period of time, there is a case where the snow falls over the upper part of the lattice portion 11a of the snowfall prevention fence 11. In some cases, snow canopies may protrude from the upper part of the lattice part 11a due to snow covered at a position higher than the upper part of the lattice part 11a. The snow can fall as the internal snow settles. However, this snow plow is not subject to much pressure due to the weight of the snow itself, and since it has not passed much time since it snowed, its density is relatively low, and many of them are scattered during the fall. To be. Moreover, even if it falls while it is large, the impact at the time of dropping does not increase.

  As described above, in the Nielsen Rose bridge 1 according to this embodiment, the snowfall prevention fence 11 having the lattice portion 11 a is attached to the long side end portion of the upper horizontal structure 10 b of the upper chord member 10. The snow on the upper surface of the upper horizontal structure 10b is elastically destroyed when a large force is applied in a short period of time, but small snowflakes pass through the gaps of the lattice and fall to the lower part. Other than small snowflakes that can pass through the gaps of the lattice, they will remain on the upper surface of the upper horizontal structure 10b.

  In other words, the snow on the upper surface of the upper horizontal structure 10b is made to fall quickly from the gap of the lattice without forming a large snow ice block in a low density state. Snow falling in such a state does not damage the vehicle or the like that passes under the upper horizontal structure 10b. Here, it is possible to reduce the amount of snow covered with snow on the upper surface of the upper horizontal structure 10b by dropping a non-hazardous snowflake as early as possible, and to prevent the snow and ice block from becoming as large as possible.

  The snow covered with snow on the upper surface of the upper horizontal structure 10b without falling early is subjected to pressure especially in the lower part and becomes dense, and grows into a snowy ice block by repeated melting and freezing. In addition, this snow canopy tries to be plastically deformed in the direction of the force, but the force is blocked by a lattice (especially a lattice in the vertical direction), and a large snow ice block can be prevented from falling outside the lattice. . Especially when the upper horizontal structure 10b is horizontal or has a slight gradient, the force acting on the snow canopy can be almost completely prevented by the lattice, so that a snow sledge protrudes outside the lattice. It can prevent falling.

  Depending on the force acting on the snow cover, such as when the gradient of the upper horizontal structure 10b is large, a lump of snow may fall from the gap between the lattices, but only a size that can pass through the lattice can fall. In particular, the horizontal grid is less effective in preventing snow fall than the vertical grid, but it can reduce the falling snow mass by peeling off different layers of snow quality. . The mass of snow that has fallen through the gaps in the grid will not cause significant damage to vehicles or the like that pass through the lower part. Moreover, the growth of snow ice blocks can also be prevented by dropping the snow cover as much as possible in such a dangerous state.

  Furthermore, since many channels of water melted by the lattice are created, a large ice column does not grow. When the water treatment plate 12 is also installed in addition to the snowfall prevention fence 11, the water treatment plate can prevent water from dripping from the upper horizontal structure 10b. It will be possible to completely suppress the growth of. As described above, the snow fall prevention fence 11 and the water treatment plate 12 are high in density and may cause damage to a vehicle or the like passing through the lower part. Can prevent falling.

  Furthermore, although the height from the upper surface of the upper horizontal structure 10b to the upper part of the lattice part 11a of the snowfall prevention fence 11 is about 330 mm, it is very slightly compared with the whole size of the Nielsen-Rosen bridge 1. It ’s just something. For this reason, the shape of the Nielsen Rosen Bridge 1 whose appearance has been designed in consideration of harmony with the surrounding landscape is not greatly changed by the presence of the snowfall prevention fence 11, and the appearance is not impaired. Even if a snowfall caused by snow accumulation exceeding this height falls, its density is small, and it collapses during the fall due to the size of the head, so that it does not damage the vehicle or the like passing through the lower part.

  The present invention is not limited to the above-described embodiment, and various modifications and applications are possible. Hereinafter, modifications of the above-described embodiment applicable to the present invention will be described.

  In the above embodiment, the lattice portions 11a of the snowfall prevention fence 11 are formed with lattices at intervals of 120 mm vertically and horizontally, but the present invention is not limited to this. 4 (a), 4 (b), and 5 (a) to 5 (d) are views showing snowfall prevention fences 31 to 36 having other configurations, respectively. In addition, also when attaching these snowfall prevention fences 31-36 to the upper horizontal structure 10b, although it is more preferable to attach the water treatment plate together, the water treatment plate is abbreviate | omitted here.

  The snowfall prevention fence 31 shown to Fig.4 (a) has the grating | lattice formed in two steps | paragraphs vertically in the grating | lattice part 31a. In the snowfall prevention fence 32 shown in FIG. 4B, a lattice is formed vertically in the lattice portion 32a. The interval of the lattices in the lattice portions 31a and 32a is the same as that of the snow fall prevention fence 11 described above. Accordingly, the height from the upper surface of the upper chord member 10 to the upper end portions of the lattice portions 32a and 32b is about 220 mm and 100 mm, respectively. In addition, the height of the water treatment plate attached together with the snowfall prevention fences 31 and 32 may be smaller than the height of the water treatment plate 12 described above.

  Depending on the amount of snowfall and the quality of snow, there are some bridges where the amount of snow on the upper surface of the upper chord material 10 does not increase so much. Depending on the amount of snow covered on the upper surface of the upper chord member 10, even if the height is about 100 mm like the snowfall prevention fence 32 shown in FIG. There is no growth. When the amount of snow covered is slightly increased, if the height is about 220 mm as in the snowfall prevention fence 31 shown in FIG. 4 (a), the snow and ice mass will not grow beyond this. .

  At the height of the upper chord material 10, the wind is stronger than the ground surface and it will be able to fall early with the smallest possible snowflakes. It is calculated that it is almost possible to cope with a fence with a height of about 400 mm from the upper surface of. If the snow is not growing into a dense snow ice mass, even if the expected amount of snow is small, snow can sometimes be formed beyond the height of the snowfall prevention fences 31 and 32. Since it is dropped early in the state of a low-density snow mass, it does not damage the vehicle or the like passing through the lower part.

  In the snowfall prevention fence 33 shown in FIG. 5A, the lattice spacing of the lattice portion 33a of the snowfall prevention fence 11 described above is 60 mm, which is half. In the snowfall prevention fence 34 shown in FIG. 5 (b), the lattice spacing of the lattice portion 34a is 30 mm, which is a half. Even at such a lattice interval, low-density snowflakes that are elastically broken by a strong force in a short period can be dropped from the lattice gap. On the other hand, even when the snow that has not fallen from the gap between the grids at an early stage falls from the gap between the grids due to the force acting thereafter, the size of the snow can be further reduced. Further, when the lattice spacing is further reduced in this way, the flow path of the water melted from the snow can be further increased, so that a large ice column does not grow.

  The snowfall prevention fence 35 shown in FIG. 5 (d) has a lattice interval in the vertical direction (that is, a direction substantially perpendicular to the long side direction of the upper horizontal structure 10b) in the lattice portion 35a. Although the interval is 120 mm, which is the same as the interval of the lattice, the interval of the lattice in the horizontal direction (that is, the direction substantially parallel to the long side direction of the upper horizontal structure 10b) is 180 mm, which is 1.5 times this. In the snowfall prevention fence 36 shown in FIG. 5D, lattices are formed at intervals of 120 mm in the vertical direction in the lattice portion 36a, but no horizontal lattice is formed up to the upper portion of the lattice portion 36a.

  Even when the snowfall prevention fences 35 and 36 are used, the snow that has become a long lump in the lateral direction does not fall from the gaps in the lattice. However, in the snowfall prevention fences 35 and 36 having such a structure, it is not unlikely that snow that has become a long lump in the vertical direction may fall from the gap between the lattice portions 35a and 36a. Of course, since snow covered with snow is deposited in a layered structure, snowflakes that have shrunk naturally in the lateral direction often fall. In addition, even if a large amount of snow falls in the vertical direction, the snow layer and the snow layer easily peel off due to the force that acts during the fall, and in many cases, the snow layer is small before it falls to the ground. It will collapse into snowflakes.

  In the above embodiment, the water treatment prevention plate 12 is configured as a separate member from the snowfall prevention fence 11 and is attached to the upper chord material 10b of the bridge 1, and is integrated with the snowfall prevention fence 11 to prevent snowfall. It was supposed to work. In other words, the snowfall prevention fence that has the most effect as the present invention is constituted by two parts, that is, the main body (snowfall prevention fence 11) and the water treatment plate 12 different from the main body. On the other hand, if the water treatment plate can be attached so as not to cause a gap at the open end of the upper chord member 10b, a snowfall prevention fence in which the lattice portion and the water treatment plate are integrally formed may be applied. it can.

  In the above embodiment, the snowfall prevention fence 11 is attached so that the lattice surface of the lattice portion 11a is substantially perpendicular to the upper surface of the upper horizontal structure 10b. It is good also as what attaches so that it may incline with respect to. Particularly when the upper horizontal structure 10b has a water gradient, the lattice plane is perpendicular to the horizontal plane, that is, 45 ° to 90 ° with respect to the upper surface of the upper horizontal structure 10b depending on the magnitude of the water gradient. The snowfall prevention fence 11 can be attached so that it may incline.

  Including the above modifications, in the present invention, a snowfall prevention fence having the following lattice portion can be applied. The grid is provided at least in the vertical direction, and the interval is in the range of 30 mm to 120 mm. In order to keep the size of snow falling through the gap between the lattices within a certain range, the interval between the lattices is preferably in the range of 30 mm to 60 mm. When the grid spacing is set to 30 mm or more and 60 mm or less, even if no water treatment plate is installed, the flow path of the water generated by melting from the snow can be dispersed, and the growth of icicles Can be suppressed.

  However, regardless of the lattice spacing, when a water treatment plate is installed, the formation of icicles due to water that has melted out of the snow can be almost completely suppressed, and it occurs at the bottom of the snow. Since it is possible to completely prevent the ice plate from falling, it is preferable to attach the water treatment plate regardless of the lattice spacing. The water treatment plate can have a length to the upper end of 30 mm or more and 100 mm or less in order to suppress the growth of icicles and to suppress the falling of the ice plate, and to have a certain strength. The water treatment plate may be attached to the bridge as a member separate from the lattice portion, or may be attached integrally to the lattice portion.

  The lateral grid does not necessarily have to be, but in order to separate the different quality snow accumulated in a layered structure, and to keep the size of snow falling through the gap of the grid within a certain range, It is preferable that this is formed. The spacing should preferably have some spacing so as not to prevent the different quality snow from being peeled off, which is the same as that applied as the longitudinal grid spacing, 30 mm. It is preferable to be in the range of 120 mm or less.

  The length from the upper surface of the upper chord material of the bridge to the upper end of the lattice part should be in the range of 100 mm to 400 mm, taking into consideration the amount of snowfall and snow quality, and the surrounding landscape and the appearance of the bridge. Can do. The length to the upper end of the water treatment plate is in the range of 30 mm to 100 mm as described above, but this length can be determined according to the length to the upper end of the lattice portion.

  The attachment direction of the snowfall prevention fence can be such that the vertical lattice forms an angle of 45 ° or more and 90 ° or less with the upper surface of the upper chord material. In addition, the direction in which the water treatment plate is attached can also be at an angle of 45 ° to 90 ° with the upper surface of the upper chord material and the upper surface of the upper chord material. However, from the viewpoint of ease of attachment and attachment strength, the vertical grid and the water treatment plate can be attached in a direction substantially perpendicular to the upper surface of the upper chord material.

  In the above embodiment, the snowfall prevention fence 11 is not attached only to the long side direction end portion of the upper horizontal structure 10b, but a lattice is provided at a predetermined interval in the vertical direction to install the snowfall prevention fence in a box shape. (The water treatment plate 12 may be set only at the end portion in the long side direction, and need not be box-shaped). In this case, since the snow is divided by the vertical lattice, the snow does not grow into a snow ice block larger than the size of the box. For this reason, even when the snow ice mass is about to slide down from the upper horizontal structure 10b, it is not a huge snow ice mass, so the snow fall prevention fence 11 is added to the weight of the snow ice mass about to slide down. It will not be unbearable in strength.

  In the above embodiment, a case where a snowfall prevention fence is attached to the Nielsen Rose bridge has been described as an example, but the above-described configuration is provided on the upper piers of other types of arch bridges and truss bridges, and further on the piers of suspension bridges. It is also possible to attach a snowfall prevention fence having. As a bridge, not only a road bridge, but also any vehicle that can pass through a lower part of an upper chord material such as a railway bridge or a humanitarian bridge can be applied.

  Further, after the bridge is completed, a snowfall prevention fence configured separately from the upper chord material is not attached, but the snowfall prevention fence may be integrated with the upper chord material. In this case, it is possible to design the bridge in accordance with the surrounding landscape by integrating the lattice-shaped snowfall prevention fence. However, even when a snowfall prevention fence is separately attached to the upper chord material of the bridge, the bridge can be designed in consideration of the state in which the snowfall prevention fence is attached from the beginning.

  Furthermore, a snowfall prevention fence can be attached to the cable of the cable-stayed bridge. Conventionally, snow and snow accretion on cables of cable-stayed bridges have been removed using a dedicated scraper. However, since the thickness of the cable is thick at the attachment end to the main tower, it was difficult to remove snow with this scraper. Therefore, in cable-stayed bridges, the effect can be obtained particularly by attaching a snowfall prevention fence to the end of the cable that is difficult to remove snow with a scraper.

  FIG. 6 is a partial perspective view of a cable-stayed bridge to which the snowfall prevention fence according to the embodiment of the present invention is applied. As shown in the figure, the cable-stayed bridge 2 has a structure in which a plurality of cables 21 are attached to the main tower 20 and the other ends of these cables 21 are attached to the girder to support the girder. The attachment end 21a located about 1 to 2 m from the main tower 20 of the cable 21 is thicker than other portions. The thickness of the attachment end 21a is about 200 mm.

  In the cable-stayed bridge 2, snow covered with the cable 21 has been removed by a scraper that travels on the cable 21 conventionally. However, the scraper does not reach up to the thick attachment end 21a, and snow cannot be removed. A snowfall prevention fence 22 having the same action as the snowfall prevention fence 11 described above is attached to the attachment end portion 21a from which the snow can not be removed with this scraper.

  FIG. 7 is a diagram showing in detail the mounting state and configuration of the snowfall prevention fence 22 of FIG. As shown in FIG. 7A, a U-bolt 23 for attaching the snowfall prevention fence 22 is fixed to the attachment end portion 21 a of the cable 21 using a fastener 24. A pair of snowfall prevention fences 22 are fixed to the upper part of the U bolt 23 using bolts 22b (see FIG. 7B). That is, the pair of snowfall prevention fences 22 is attached so as to sandwich the upper part of the attachment end 21a. Further, a fence 25 in which a grid having a thickness of 10 mm is formed at intervals of 70 mm is attached in the vertical direction of the opposing snowfall prevention fence 22 (at least at the end of the attachment end portion 21a).

  As shown in FIG.7 (b), the snowfall prevention fence 22 is comprised with the metal, and the grating | lattice part 22a is provided in the upper part. In the lattice portion 22a, two lattices are formed vertically and ten lattices are formed horizontally. The vertical grid spacing is 82 mm, the horizontal grid spacing is 100 mm at both ends, 70 mm at both ends, and the horizontal width per snowfall fence 22 is 940 mm. Yes. The snowfall prevention fence 22 is attached at least up to a position of 43 mm of the attachment end 21a where the cable 21 becomes thick. If the width of one snowfall prevention fence 22 is not enough for the length of the attachment end 21a, a plurality of snowfall prevention fences 22 are connected as shown in the figure.

  If there is snowfall in the area where the cable stayed bridge 2 is installed, the cable 21 and the cable 21 including the attachment end 21a will also snow and snow (collectively referred to simply as snow). The snow covered with the cable 21 is removed by the scraper, but the snow covered with snow remains on the attachment end portion 21a that does not reach the scraper. As with the above-mentioned snow covered on the upper portion of the upper horizontal structure 10b, the snow covered with the attachment end 21a that cannot be removed by the scraper can be quickly dropped in the form of small snowflakes having a low density from the lattice gap of the lattice 22a. In addition to being possible, it is possible to prevent the snow covered from being snowed at an early stage from being blocked by the lattice so as not to fall down. Furthermore, the fence 25 attached in the vertical direction of the opposing snowfall prevention fence 22 can completely prevent the fall of the snow and ice mass from the attachment end portion 21a of the cable 21.

  In addition, the lattice part of the snowfall prevention fence attached to the attachment end part 21a of the cable 21 may also be any one as long as a lattice in the vertical direction (substantially perpendicular to the direction in which the cable 21 extends) is formed. Can be set in the range of 50 mm to 150 mm. Further, the grid interval in the lateral direction (substantially parallel to the direction in which the cable 21 extends) can be set to an arbitrary length of 50 mm or more, and the grid interval in the vertical direction is less than this. It is preferable.

  Moreover, although the fence 25 is attached to the perpendicular direction of a pair of snowfall prevention fence 22, this fence 25 is not necessarily required. When a pair of snowfall prevention fences 22 is attached to the attachment end portion 21a of the cable 21, snow and ice blocks grown from the snow covered with snow remaining on the attachment end portion 21a are suppressed to some extent by the lattice portion 22a due to the viscoelastic nature of the snow. Because it can fall and almost never fall.

(First experiment)
In order to verify the effectiveness of the snowfall prevention fence shown in the above embodiment, an experiment was conducted using an experimental device that assumed a case where there was no (too much) inclination of the upper chord material at the Nielsen Rose Bridge, Rose Bridge, or Truss Bridge. went. FIG. 8 is a diagram showing an experimental apparatus in the first experiment for verifying the effectiveness of the snowfall prevention fence. The snowfall prevention fences 41a and 41b applied here are made of wood, the grid thickness is set to 20 mm, and the grid intervals are set to 120 mm vertically and horizontally. Further, the grid is provided in three stages in the vertical direction, and has substantially the same function as the snowfall prevention fence 11 shown in the above embodiment.

  In FIG. 8, (a) is an experimental apparatus 4a without a water gradient assuming a snowfall prevention fence 41a and assuming a truss bridge, and (b) is 3 ° assuming a Nielsenrose bridge with a snowfall prevention fence 41b attached. The experimental apparatus 4b which provided the water gradient of this is shown. (C) is an experimental apparatus 4c without a water gradient assuming a truss bridge without a snowfall prevention fence as a comparison, and (d) is a 3 ° assuming a Nielsenrose bridge without a snowfall prevention fence as a comparison. The experimental apparatus 4d which provided the water gradient of this is shown.

  In addition, these experimental devices 4a to 4d are installed outdoors to obtain natural snowfall and outdoor temperature in order to obtain conditions close to the upper chord of the bridge, and at a certain height from the ground. It was assumed that it was installed in the natural wind. Here, by repeating the snowfall and the melting of the snow, the amount of the snow caps 43a to 43d increases on the flat plates 42a to 42d of the respective experimental devices. And the behavior of the snow caps 43a to 43d was continuously observed. During this period, no manual snow removal work was performed. The behavior of the snow caps 43a to 43d with the passage of time will be described with reference to FIG.

  As shown in FIG. 9 (a), in the experimental device 4a, even if a force is applied to the snow cap 43a due to the wind, the force is blocked by the lattice of the snow fall prevention fence 41a, and the lattice is formed outside the flat plate 42a. It was observed that no overhang of snow ridges occurred during the period. In addition, it was also observed that small snowflakes 44a formed by elastic breakage of the snow cap 43a due to a short-term strong force such as a strong wind fall through the gaps of the lattice at an early stage.

  On the other hand, as shown in FIG. 9C, in the experimental device 4c without the snowfall prevention fence, when a force acts on the snow cover 43c due to the wind, the snow cover 43c slides in the direction of the force. It becomes. It was observed that due to this sliding, the snow cap 43c overhangs on the outside of the flat plate 42c, and a snow bag 44c having a relatively high density was formed. It was also observed that the snowfall 44c fell as a large lump when the overhang amount increased due to further sliding. It was also observed that water melted from the snow cap 43c was most frozen and a relatively large ice column 45c was formed at the end of the flat plate 42c.

  Further, as shown in FIG. 9B, in the experimental device 4b, a slightly large force acts on the snow cap 43b due to the gradient provided on the flat plate 42b in addition to the influence of the wind. Of course, even if a slightly large force is applied to the snow cap 43b due to the influence of the gradient, the force is still blocked by the lattice of the snow fall prevention fence 41b, and a snow ridge does not protrude from the lattice outside the flat plate 42b. I was able to observe. Further, as in the case of the experimental device 4a, it is also observed that small snowflakes 44b formed by elastic breakage of the snow cap 43b due to a strong force such as a strong wind for a short period of time fall through the gaps of the lattice at an early stage. It was.

  On the other hand, as shown in FIG. 9 (d), in the experimental device 4d without a snowfall prevention fence, when the snow cap 43d exceeds a certain amount, the crown works one after another by the force acting on the gradient provided on the flat plate 42d. It was observed that the snow 43d overhangs to form a snow hail 44d, which becomes a snowflake 45d and slides down from the flat plate 42d. It was observed that among the snowflakes 45d sliding down from the flat plate 42d, those having a relatively high density were included, or those having a relatively large size and a considerable weight as a whole were included.

  Further, in the experimental devices 4a and 4b, it was possible to observe that an ice plate having a thickness of about 10 mm was formed under the snow and ice block on which the snow covered on the flat plates 42a and 42b grew. . However, this ice plate is prevented from sliding directly by the snowfall prevention fences 41a and 42a, and the sliding is also prevented by preventing the snow from sliding on the snowfall fences 41a and 42a. I could observe that there was nothing to do.

  Furthermore, in the experimental device 4d, the formation of icicles was not observed because the snowfall amount of snow was large, but as described above, in the experimental device 4c, a relatively large icicle 45c was formed at the end of the flat plate 42c. It was observed that On the other hand, in the experimental devices 4a and 4b, it was only observed that a relatively small ice column was formed in the vicinity of the lattice of the snowfall prevention fences 41a and 41b.

  From the results of the first experiment described above, if the upper chord material of the bridge is horizontal or slightly inclined, if a snowfall prevention fence with a lattice is installed on the upper chord material of the bridge, go to the upper part of the upper chord material. It can be estimated that the snow can be quickly dropped by small snowflakes with low density. In addition, it can be estimated that the density increases without falling early from the upper chord material, and further, the fall of the snow covered with snow and ice can be prevented by the snow fall prevention fence. Furthermore, it can be estimated that a huge ice column can be prevented from being formed by the snowfall prevention fence.

(Second experiment)
In addition, the experiment was performed using an experimental apparatus that assumed a case where the upper chord material had a large inclination in the Nielsen Rose Bridge, the Rose Bridge, or the Truss Bridge. FIG. 10 is a diagram illustrating an experimental apparatus in a second experiment for verifying the effectiveness of the snowfall prevention fence. In the experimental apparatus applied here, the flat plate 50 assumed as the upper chord material is inclined by 30 ° with respect to the horizontal plane. Moreover, it partitions with the partition plates 50a-50e for every part which attached the fence of a different type.

  The portions partitioned by the partition plates 50a to 50e are the experimental devices 51 to 54, respectively. The vertical lattice spacing of the snowfall prevention fence 61 attached to the experimental device 51 is 240 mm, and the vertical lattice spacing of the snowfall prevention fence 62 attached to the experimental devices 52 and 53 is 120 mm, attached to the experimental device 54. The distance between the vertical grids of the snowfall prevention fence 64 is 60 mm. The snowfall prevention fence 61 has no horizontal grid other than the uppermost part and the lowermost part, but the snowfall prevention fences 62 and 64 are provided with a horizontal grid at the same interval as the vertical grid.

  Further, in addition to the snowfall prevention fence 62, a metal water treatment plate 63 having a height of 90 mm is attached to the experimental apparatus 53. The lattices of the snowfall prevention fences 61, 62, and 64 attached to the experimental devices 51 to 54 are all made of metal and have a thickness of 6 mm. Further, the snowfall prevention fences 61, 62, 64 and the water treatment plate 63 are all attached so as to be perpendicular to the flat plate 50.

  In order to obtain conditions close to the upper chord of the bridge, the experimental apparatus shown in FIG. 10 is also installed outdoors to obtain natural snowfall and outside air temperature, and is installed at a certain height from the ground. It was assumed that the natural wind hit. In this experimental apparatus, since the flat plate 50 has a large inclination of 30 °, a force that moves toward the snowfall prevention fences 61, 62, 64 acts on the snow covered on the flat plate 50. Then, the behavior of snow on the flat plate 50 was continuously observed. During this period, no manual snow removal work was performed.

  FIG. 11 is a table showing a list of experimental results in the second experiment. In the experimental apparatus 51 equipped with a snowfall prevention fence 61 with a grid interval of 240 mm, it was observed that the snow accumulated on the flat plate 50 dropped through the gaps of the grid and that the time until the snowfall was short. It was observed that the size of the falling snow mass was within the interval of the grid in the vertical and horizontal directions, but was relatively long in the front-rear direction as well. It was also observed that the snow mass contained a dense ice plate formed at the bottom. Furthermore, it was observed that large icicles were formed.

  In the experimental apparatus 52 equipped with only the snowfall prevention fence 62 having a grid interval of 120 mm, it was observed that the snow accumulated on the flat plate 50 fell through the gaps of the grid and that the time until the fall was relatively short. . As for the size of the falling snow mass, the length in the vertical direction is within the interval of the lattice, but the length in the front-rear direction is shorter than that in the case of the experimental apparatus 51 and may be sufficiently small as a whole. I was able to observe. However, it has been observed that the snow mass falling through the gap in the bottom lattice may contain dense ice plates. Furthermore, it was observed that relatively large icicles were formed.

  In the experimental device 53 in which the snowfall prevention fence 62 having a grid interval of 120 mm and the water treatment plate 63 are attached, a portion of the snow accumulated on the flat plate 50 that exceeds the height of the water treatment plate 63 passes through the gap of the lattice. I was able to observe falling. It was observed that the time until the drop was sufficiently long compared to the experimental device 52. Although the size of the falling snow mass is not much different from that of the experimental device 52, it was observed that it was an upper layer portion and the density was low. The bottom ice plate does not fall at all. Furthermore, it was observed that no icicles were formed.

  In the experimental device 54 to which the snowfall prevention fence 64 having a lattice interval of 60 mm was attached, the snow accumulated on the flat plate 50 sometimes dropped through the gap between the lattices. It was about the same. It was observed that the size of the falling snow mass was considerably small because the lattice spacing was small, and that the ice plate formed at the bottom could be prevented from falling. In addition, since there were many vertical grids, many channels were formed for the water melted from the snow, and even if icicles were formed, it was observed that they did not grow so much.

  In addition, although the same experiment was performed using the experimental apparatus to which the snowfall prevention fence with the vertical and horizontal grid intervals of 30 mm was attached, the experimental result was almost the same as the experimental apparatus 54 to which the snowfall prevention fence 64 with the grid interval of 60 mm was attached. Obtained. In addition, a similar experiment was performed using an experimental apparatus in which a water treatment plate 63 was attached in addition to the snow fall prevention fence 64 having a grid interval of 60 mm. The snow fall prevention fence 62 and the water treatment plate 63 having a grid interval of 120 mm were combined. An experimental result almost similar to that of the attached experimental device 53 was obtained.

  In any experimental apparatus, the height from the surface of the flat plate 50 to the top of the snowfall prevention fences 61, 62, 64 (the length in the direction perpendicular to the surface of the flat plate 50) was set to 330 mm. In some cases, snow covered with snow exceeding this height was observed, and in some cases, snow bags formed over the top of the fence fell. However, the fallen snowfall sometimes dropped in a relatively large size, but the density was very small and it was observed that it collapsed during the fall, so even if it dropped from the upper chord material of the bridge, It is considered that it will not cause great damage to vehicles traveling underneath.

  It can be seen that if the distance between the lattices of the snowfall prevention fence is up to 120 mm, the size of the snow mass falling from the upper chord material of the bridge can be made sufficiently small. However, if the lattice spacing is too small, even small snowflakes cannot be dropped, and the accumulated snow will put a considerable weight on the fence, but if the lattice spacing is 30 mm, it will fall as small snowflakes. You can see that

  It can be seen that if the lattice spacing is 30 mm to 60 mm, the ice plate can be prevented from falling and large icicles can be prevented from growing without a water treatment plate. It can be seen that by attaching a water treatment plate in addition to the snowfall prevention fence, the ice plate can be completely prevented from falling and icicles can be completely suppressed. From the above experimental results, a vehicle that passes under the bridge by attaching a water treatment plate to the upper chord material of the bridge together with a snowfall prevention fence with a grid spacing of 120 mm (up to 30 mm may be smaller) It can be presumed that the fall of snow and ice blocks that would cause loss to the snow etc. can be prevented.

It is a fragmentary perspective view of the Nielsen Rose bridge which applied the snowfall prevention fence concerning embodiment of this invention. It is a figure which shows the example of the snowfall prevention fence attached to the upper chord material of the Nielsenrose bridge of FIG. It is a figure which shows the example of the water treatment plate attached to an upper chord material with the snowfall prevention fence of FIG. It is a figure which shows the modification of a snowfall prevention fence. It is a figure which shows the modification of a snowfall prevention fence. It is a fragmentary perspective view of the cable-stayed bridge to which the snowfall prevention fence concerning other embodiment of this invention is applied. It is a figure which shows the snowfall prevention fence attached to the cable edge part of the cable-stayed bridge of FIG. It is a figure which shows the experimental apparatus in the 1st experiment for verifying the effectiveness of a snowfall prevention fence. It is a figure explaining the experimental result in the 1st experiment for verifying the effectiveness of a snowfall prevention fence. It is a figure which shows the experimental apparatus in the 2nd experiment for verifying the effectiveness of a snowfall prevention fence. It is a table which shows the experimental result in the 2nd experiment for verifying the effectiveness of a snowfall prevention fence.

Explanation of symbols

10 Upper chord material 11 Snowfall prevention fence 12 Water treatment plate 21 Cable 22 Snowfall prevention fences 31-36 Snowfall prevention fence

Claims (8)

  It is attached to the open end portion of the upper chord member of the bridge having an inclination of 0 ° to 45 ° with respect to the horizontal plane, and 5 mm at intervals of 30 mm to 120 mm so as to form an angle of 45 ° to 90 ° with at least the upper surface of the upper chord member. A snowfall prevention fence characterized by having a lattice portion in which a lattice having a thickness of ˜20 mm is formed and the length from the upper surface to the upper portion of the upper chord material is set in a range of 100 mm to 400 mm.   The snowfall prevention fence according to claim 1, wherein the vertical grids are formed at intervals of 30 to 60 mm.   A plate forming an angle of 45 ° to 90 ° with the upper surface of the upper chord material is formed between the upper chord material and the lattice portion of the upper chord material at an open end of the upper chord material within a range of 30 mm to 100 mm. The snowfall prevention fence according to claim 1 or 2, wherein the snowfall prevention fence is provided.   3. The grid according to claim 1, further comprising a grid having a thickness of 20 mm or less at an interval of 30 mm to 120 mm in a substantially parallel direction to the open end of the upper chord material. The snowfall prevention fence described.   A bridge comprising the snowfall prevention fence according to any one of claims 1 to 4 attached to an end portion of an upper chord material.   The cable connecting the main tower of the cable-stayed bridge and the girder is attached to the attachment end of the main tower having a large thickness, and at least a distance of 50 mm to 150 mm in a direction substantially perpendicular to the extending direction of the cable. A snowfall prevention fence, comprising a lattice portion formed with a lattice.   2. The snowfall prevention fence according to claim 1, wherein a lattice in a direction substantially parallel to the extending direction is further formed in the lattice portion at an interval equal to or greater than an interval between the lattices in the vertical direction.   A bridge characterized in that the snowfall prevention fence according to claim 6 or 7 is attached to an end of a cable stayed cable bridge attached to a main tower.

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