JP2011032651A - Bridge reinforcing structure and bridge reinforcing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bridge reinforcing structure and a bridge reinforcing method in an outside cable method preventing excessive axial force from being introduced to a bridge girder and effectively reducing stress applied to the bridge girder by a live load. <P>SOLUTION: The bridge reinforcing structure includes a cable 13 stretched in the bridge length direction of a bridge 1, and a fulcrum forming member 12 turning the cable. An upward force is applied to the fulcrum forming member by a vertical component F2 of tension F applied to the cable to reduce bending stress of the bridge girder 3. The bridge reinforcing structure includes towers 11 erected on structures 2, 6 outside the bridge girder or on the ground to transmit the tension of the cable to the structures or the ground, and a cable anchoring means 14 anchoring the cable having passed the towers, to the structures or the ground or anchoring the cable to the towers. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a bridge reinforcement structure and a reinforcement method, and more particularly, to an external cable structure along a bridge girder in order to improve load resistance and durability of an existing bridge such as an existing steel road bridge. The present invention relates to a bridge reinforcement structure and a bridge reinforcement method of a cable method.

  Due to the rapid increase in the aging of existing bridges, the increase in vehicle size and the increase in traffic volume due to the revision of the design of automobile roads and the increase in traffic volume, problems such as insufficient load bearing capacity and reduced durability have been pointed out in recent years. . As a general solution to this problem, replacement of existing bridges can be considered, but replacement of existing bridges is often difficult economically and socially. Therefore, it is considered necessary to take appropriate preventive maintenance measures that contribute to extending the life of structures for the purpose of reducing life cycle costs.

  Various methods such as a steel plate reinforcement method, a connecting plate high-strength bolt fastening method, and an external cable method have been proposed as reinforcement measures for existing bridges having such problems. For example, the steel plate reinforcing method is a method for improving the rigidity of an existing member by attaching a reinforcing member to the existing member, and a relatively large number of construction results are known. However, although it is relatively simple to attach the reinforcing member by welding, there are disadvantages such as a relatively large cost associated with welding and a decrease in fatigue strength. In addition, the attachment plate high-strength bolt tightening method using a high-strength bolt needs to drill a large number of holes in the existing member when attaching the reinforcing member, and the load resistance of the existing member temporarily decreases. The steel plate reinforcement method can also only be adapted to local reinforcement of bridges.

  On the other hand, the outer cable construction method is a method that has been attracting attention in recent years, and is equipped with fixing brackets, deflecting brackets, etc., on existing bridge components and installing cables. It is known as a construction method that generates a bending moment in a direction that cancels the bending moment acting on the surface.

  As described in Japanese Patent Laid-Open No. 2003-221809, Japanese Patent Laid-Open No. 2001-64912, and Japanese Patent Laid-Open No. 2003-293323, the outer cable construction method connects the end of the cable to the end of the bridge girder by a fixing bracket or the like. The cable is stretched between the piers by deflection / tensioning means such as saddle, pillow, hydraulic jack, intermediate bracket, etc., and the axial load force in the bridge length direction is applied to the bridge girder to increase the load bearing capacity of the bridge It is a construction method configured to do.

Japanese Patent Laid-Open No. 2003-221809 JP 2001-64912 A Japanese Patent Laid-Open No. 2003-293323

  In the outer cable construction method, the bending moment that cancels the bending moment acting on the bridge girder due to dead load or the like is generated by the prestress of the cable, so the axial force in the bridge length direction acts on the bridge girder as a compressive force continuously. When the construction method in which an additional axial force is always applied to the bridge girder is employed in this way, there is a concern that an undesired constant load is imposed on the bridge girder for an aged bridge.

  The outer cable method is an effective method for reinforcing existing bridges in order to reduce the stress acting on the bridge girder due to dead load, but depending on the conventional outer cable method, the stress acting on the bridge girder due to live load can be reduced. It is considered difficult to reduce effectively. However, in view of recent trends such as an increase in the size of vehicles and an increase in traffic volume, it is desired to develop an existing bridge reinforcement method that can effectively reduce the live load stress by providing such a cable reinforcement structure.

  The present invention has been made in view of such problems, and the object of the present invention is to prevent an excessive axial force from being introduced into the bridge girder and to effect the stress acting on the bridge girder by a live load. It is an object of the present invention to provide a bridge reinforcement structure and a bridge reinforcement method for an outer cable method that can be reduced in an economical manner.

In order to achieve the above object, the present invention includes a cable stretched in a bridge length direction of a bridge, and a fulcrum forming member that is integrated with a bridge girder and that contacts the cable and turns the cable. In the bridge reinforcement structure that reduces the bending stress of the bridge girder by applying an upward force to the fulcrum forming member by the vertical component of the acting tension,
A tower erected on the structure or ground to transmit the tension of the cable to the structure or ground outside the bridge girder;
In order to transmit the horizontal component of the tension acting on the cable to the structure or ground outside the bridge girder, the cable turned in the upper part of the tower and the fulcrum forming member is moored to the structure or ground, or the fulcrum There is provided a bridge reinforcing structure comprising cable anchoring means for anchoring the cable turned in the forming member to the tower.

The present invention also provides a cable extending in the bridge length direction of the bridge, bringing the cable into contact with a fulcrum forming member integrated with the bridge girder and turning the cable, and the fulcrum by the vertical component of the tension acting on the cable. In the bridge reinforcement method for reducing the bending stress of the bridge girder by applying an upward force to the forming member,
The cable turned by the upper part of the tower standing on the structure or ground outside the bridge girder and the fulcrum forming member is moored to the structure or ground outside the bridge girder, or the cable turned by the fulcrum forming member is There is provided a method for reinforcing a bridge which is moored to the tower and thereby supports a horizontal component of tension acting on the cable by a reaction force of the structure or the ground.

  According to the above configuration of the present invention, the tension of the cable is transmitted to the structure or the ground outside the bridge girder via the tower, or directly transmitted to the structure or the ground outside the bridge girder, and the structure outside the bridge girder or Supported by the ground reaction force. The vertical component of the tension acting on the cable acts to reduce the bending stress of the bridge girder by applying an upward force to the fulcrum forming member. The horizontal component of the pretension applied to the cable in advance or the live load causes the cable to The horizontal component of the acting tension is supported by the reaction force of the structure or ground outside the bridge girder. That is, according to the present invention, the horizontal component of the tension acting on the cable is not substantially transmitted to the bridge girder, and therefore it is possible to reliably prevent excessive axial force from being introduced into the bridge girder. Further, according to the present invention, the live load acting on the bridge girder acts as cable tension and is supported by the reaction force of the structure outside the bridge girder or the ground, so that the bending stress acting on the bridge girder by the live load is effective. Can be reduced.

  According to the bridge reinforcing structure and the bridge reinforcing method of the present invention, it is possible to prevent an excessive axial force from being introduced into the bridge girder without impairing the advantages of the outer cable construction method, and to effect the stress acting on the bridge girder by a live load. Can be reduced.

FIG. 1A is a schematic side view of a bridge showing a bridge reinforcement structure according to a first embodiment of the present invention, and FIG. 1B is a modification of the bridge reinforcement structure shown in FIG. It is a schematic side view shown. FIG. 2 is a schematic side view of a bridge showing a bridge reinforcing structure according to a second embodiment of the present invention. FIG. 3 is a schematic side view of a bridge showing a bridge reinforcing structure according to a third embodiment of the present invention. FIG. 4 is a schematic side view of a bridge showing a bridge reinforcing structure according to a fourth embodiment of the present invention. FIG. 5 is a partial perspective view schematically showing the structure of the bridge shown in FIG. FIG. 6 is a diagram showing changes in the dead load stress (maximum principal stress) of the existing bridge before and after the installation of the bridge reinforcing device. FIG. 7 is a diagram showing a change in the dead load stress before and after reinforcing the cable structure with respect to the steel deck slab truffle of the central span. FIG. 8 is a diagram showing changes in the live load stress (maximum principal stress) before and after reinforcing the cable structure with respect to the lower flange of the box girder. FIG. 9 is a diagram showing the change in the live load stress acting on the steel deck slab truffles between the center spans in relation to the position in the bridge axis direction. FIG. 10 is a diagram showing the difference in the live load stress properties associated with the difference in tower height. FIG. 11 is a side view schematically showing configurations of the first model and the second model shown in FIG.

  According to a preferred embodiment of the invention, the tower is erected on a bridge abutment or pier. Preferably, the fulcrum forming member has a bridge saddle or a supporting member that slides or rolls on the cable, and projects from a lower portion of the bridge girder.

  In a preferred embodiment of the present invention, the cable mooring means includes a mooring device for mooring the end of the cable to the upper portion of the tower, and the mooring device moors the cable turned upward by the fulcrum forming member to the tower. To do. Preferably, the tower is erected on the abutment or pier of the bridge, and the cable is moored at the top of the tower. The cable turned upward by the fulcrum forming member is moored at the top of the tower, and the horizontal component of the tension acting on the cable is transmitted to the abutment or pier via the tower and supported by the reaction force of the abutment or pier. .

  In another preferred embodiment of the present invention, the tower has a bridge saddle or bearing member that slides or rolls on the cable, and the bridge saddle or bearing member is turned upward by a fulcrum forming member. Turn down. The cable mooring means includes a mooring tool for mooring the end of the cable turned in the vertical direction by the saddle or supporting member for the bridge of the tower and the fulcrum forming member to the structure or the ground outside the bridge girder. Preferably, the tower is erected on the abutment or pier of the bridge, and the bridge saddle or the supporting member is disposed at the top of the tower. The cable turned upward by the fulcrum forming member turns downward at the top of the tower and is anchored to the abutment or pier. The horizontal component of the tension acting on the cable is transmitted to the abutment or pier and supported by the reaction force of the abutment or pier.

  The tower may be erected on the ground or an appropriate structure other than the abutment or pier (excluding the bridge girder), and the cable may be installed on the ground or an appropriate structure other than the abutment or pier (excluding the bridge girder). May be moored at.

  In carrying out the bridge reinforcing structure and the bridge reinforcing method of the present invention, the height of the tower is considered to greatly affect the economic efficiency and workability. According to the knowledge of the present inventor, if the pretension applied to the cable is doubled, substantially the same bridge reinforcing effect can be obtained even if the tower height is halved. That is, the pre-tension of the cable and the tower height are substantially inversely proportional. Thus, in a preferred embodiment of the present invention, the initial tension of the cable is added or increased to reduce the tower height.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 (A) is a schematic side view of a 1 span steel floor slab box girder bridge 1 showing a bridge reinforcing structure according to an embodiment of the present invention, and FIG. 1 (B) is shown in FIG. 1 (A). It is a schematic side view which shows the modification of a bridge reinforcement structure.

  A 1-span steel floor box girder bridge 1 shown in FIG. 1 (A) has a bridge girder 3 installed between a pair of abutments 2. Both ends of the bridge girder 3 are supported by both abutments 2 by roller bearings 4 and pin bearings 5. A vertical tower 11 constituting the bridge reinforcing device 10 is erected vertically on one abutment 2. A saddle portion 15 is provided at the top of the tower 11. A cable mooring device 14 capable of mooring both ends of the cable 13 is attached to each of the abutments 2 on both sides, and a support beam 19 having a saddle portion 12 is disposed at the center of the span of the bridge girder 3. The saddle portion 12 protrudes from the lower end portion (lower flange) of the bridge girder 3 in a direction perpendicular to the bridge axis and horizontally. The saddle portion 12 disposed at the distal end portion of the support beam 19 has a lower slidable contact surface with which the cable 13 is slidably contacted. As the saddle portions 12 and 15, a bridge saddle having a known structure configured to slidably support or insert the cable 13 to form a cable inflection point may be used.

  The cable 13 moored by the cable mooring device 14 on the left and right abutments 2 extends substantially horizontally along the side of the bridge girder 3 from the cable mooring device 14 of the abutment 2 shown on the left side in FIG. Slidably contact the lower slidable contact surface and turn upward to extend to the top of the tower 11. The cable 13 is further slidably contacted with the upper slidable contact surface of the saddle portion 15 disposed at the top of the tower 11 and turned downward, and extends to the cable anchoring device 14 of the abutment 2 shown on the right side in FIG. The mooring device 14 moores the end of the cable 13 to the abutment 2.

  Thus, both ends of the cable 13 are anchored to the abutment 2 on both sides by the cable anchoring device 14, and the saddle portion 12 constitutes a fulcrum forming member that is supported on the cable 13 by the vertical component F2 of the tension F acting on the cable 13. To do.

  A bridge reinforcing device 10 including a tower 11, saddle portions 12 and 15, a cable 13, and a cable mooring device 14 shown in FIG. 1 (A) is arranged in pairs on both sides (both sides) of the bridge girder 3. . The cable 13 is disposed at a predetermined interval from the main girder side surface of the bridge girder 3. For example, the cable 13 extends near the edge of the side deck on the outside of the side deck (side floor slab), or extends in the bridge length direction through a sidewalk or road surface arranged in the side deck portion. To do. In this case, the support beam 19 protrudes from the main girder so as to protrude from the side surface of the main girder in the bridge width direction within a range of about the width of the bridge. It is also possible to dispose the support beam 19 inside the bridge. For example, when providing a median strip or the like at the center of the bridge girder 3 in the width direction of the bridge, the bridge reinforcing device 10 may be arranged so that the cable 13 extends along the center band of the bridge girder 3.

  An initial tension F (shown by a broken line arrow) is applied as a pretension to the cable 13 extending between the pair of cable mooring devices 14 by a hydraulic jack or the like (not shown), and the cable 13 is tensioned. . In FIG. 1A, a horizontal component F1 and a vertical component F2 of the initial tension F are shown. The initial tension F is transmitted to the abutments 2 on both sides via the cable mooring device 14 and is supported by the horizontal reaction forces R1 and R3 and the vertical reaction force R2 of the abutment 2. Since the left and right horizontal components F1 acting on the saddle portion 12 are balanced with each other, no axial force (compression force or tensile force) acts on the bridge girder 3. The vertical component F2 acting on the saddle portion 12 acts to cancel the vertical load acting on the center portion of the bridge girder 3 and reduce the bending moment at the center portion of the bridge girder. Assuming that the initial tension F is as close to zero as possible, it can be considered that the tension F (vertical component F2) acts on the cable 13 as a reaction force that supports the live load L (shown by the broken arrow) acting on the bridge girder 3. .

  As the cable 13, a known PC (Prestressed Concrete) steel stranded wire having a cross-sectional dimension adapted to the introduction tension or pre-tension can be preferably used. Further, as the saddle portion 12, a bridge saddle having a known structure configured to slidably support or insert the cable 13 to form a cable inflection point can be used.

  FIG. 1B shows a modification of the bridge reinforcing device 10 shown in FIG. In the embodiment shown in FIG. 1B, the tower 11 erected on the abutment 2 is inclined upward at a predetermined angle θ on the opposite side of the saddle portion 12 and extends upward. A cable mooring device 14 capable of mooring the other end of the cable 13 is disposed at the upper end of the tower 11. The cable 13 extends obliquely downward from the upper end of one tower 11, slidably contacts the lower sliding surface of the saddle portion 12, and extends substantially horizontally. The cable mooring device 14 of the abutment 2 shown on the left side in FIG. Extend to. The cable anchoring device 14 anchors the end of the cable 13 to the abutment 2. 1B, the initial tension F of the cable 13 is transmitted to the abutment 2 through the cable mooring device 14 and the tower 11, and the horizontal reaction forces R1, R3 and the vertical reaction force of the abutment 2 are transmitted. Supported by R2.

  FIG. 2 is a schematic side view of a bridge showing a bridge reinforcing structure according to another embodiment of the present invention.

  Similar to the above-described embodiment, the one-diameter steel floor slab box girder bridge 1 has a bridge girder 3 installed between a pair of abutments 2. Both ends of the bridge girder 3 are supported by both abutments 2 by roller bearings 4 and pin bearings 5. The bridge reinforcing device 10 includes a tower 11, a saddle portion 12, a cable 13, and a cable mooring device 14. The cable 13 is in sliding contact with the upper sliding contact surface of the saddle portion 15 provided at the top of the tower 11, turns downward, and extends to the cable mooring device 14. The cable anchoring device 14 anchors the end of the cable 13 to the abutment 2. As the saddle portion 15, a bridge saddle having a known structure configured to slidably support or insert the cable 13 to form a cable inflection point may be used.

  The cable 13 extending from the cable mooring device 14 to the saddle portion 12 via the saddle portion 15 is given an initial tension F (shown by a broken arrow) as a pretension by a hydraulic jack or the like (not shown), and the above-described implementation. As in the example, the cable 13 is tensioned. FIG. 2 shows a horizontal component F1 and a vertical component F2 of the initial tension F. The initial tension F is supported by the horizontal reaction force R1 and the vertical reaction force R2 of the abutment 2. As in the previous embodiment, since the left and right horizontal components F1 acting on the saddle portion 12 are balanced with each other, no axial force (compressive force or tensile force) acts on the bridge girder 3. The vertical component F2 acting on the saddle portion 12 acts to cancel the vertical load acting on the center portion of the bridge girder 3 and reduce the bending moment at the center portion of the bridge girder. Assuming that the initial tension F is as close to zero as possible, it can be considered that the tension F (vertical component F2) acts on the cable 13 as a reaction force that cancels the live load L acting on the bridge girder 3.

  3 and 4 are schematic side views of a bridge showing a bridge reinforcing structure according to still another embodiment of the present invention. FIG. 5 is a partial perspective view schematically showing the structure of the bridge shown in FIG. FIG. 3 shows a two-diameter continuous steel floor slab box girder bridge 1, and FIGS. 4 and 5 show a three-diameter continuous steel floor slab box girder bridge 1. FIG.

  As shown in FIGS. 3 and 4, in the steel deck slab bridge 1 constructed continuously in a plurality of spans, the bridge girder 3 is supported by the abutment 2 and the pier 6. The abutment 2 and the pier 6 are arranged at equal intervals. One end of the bridge girder 3 is supported on the abutment 2 by a pin support 5, and the other end and the middle part of the bridge girder 3 are supported on the abutment 2 and the pier 6 by roller supports 4 and 7.

  The bridge reinforcing device 10 shown in FIG. 3 includes saddle portions 12 and 17, a tower 11, a cable 13, and a cable mooring device 14. The tower 11 is erected vertically on the bridge pier 6 disposed in the middle part of the bridge girder 3. The saddle portion 17 is provided at the top of the tower 11 and includes an upper sliding contact surface that turns the cable 13 downward.

  As in the previous embodiment, the cable mooring device 14 is disposed on each of the left and right abutments 2 so as to fix each end of the cable 13 to each abutment 2, and the saddle portion 12 is disposed in the center portion of the span. The The cable 13 moored to the left and right abutments 2 by the cable mooring device 14 extends substantially horizontally along the side portion of the bridge girder 3, slidably contacts the lower slidable contact surface of the saddle portion 12, and is turned upward to be tower 11. Extending to the top of the saddle, and slidably contacts the upper sliding surface of the saddle portion 17 and turns downward.

  In the three-diameter continuous steel deck box girder bridge 1 shown in FIGS. 4 and 5, a saddle portion 18 is further disposed between the two towers 11. The saddle portion 18 is cable turning means having substantially the same structure as the saddle portion 12. The cable 13 turned downward by the saddle portion 17 of the one tower 11 is turned upward by the saddle portion 18 between the two towers 11 (between the central diameters), and extends to the saddle portion 17 of the other tower 11. The saddle portion 17 turns downward.

  The steel deck slab girder bridge 1 has a structure in which a number of truffles 9 extending in the bridge axis direction are disposed on the lower surface of the steel deck as shown in FIG. In a multi-span continuous steel floor slab box girder bridge constructed continuously over multiple spans of 4 spans or more, the tower 11 shown in FIGS. 4 and 5 corresponds to the number of piers 6. Although the saddle portions 17 and 18 are added, the bridge reinforcing device 10 has substantially the same basic configuration as the three-diameter continuous steel deck box girder bridge 1 shown in FIGS.

  As in the above-described embodiment, in the bridge reinforcing device 10 shown in FIGS. 3 and 4, the cable 13 is given an initial tension F (indicated by a dashed arrow) as a pretension by a hydraulic jack or the like (not shown). The cable 13 is tensioned. 3 and 4 show the horizontal component F1 and the vertical component F2 of the initial tension F. FIG. The initial tension F is supported by the horizontal reaction force R3 of the abutment 2 and the vertical reaction force R4 of the abutment 6. As in the previous embodiment, the left and right horizontal components F1 acting on the saddle portions 12 and 18 balance each other, so that no axial force (compressive force or tensile force) acts on the bridge beam 3. The vertical component F2 acting on the saddle portions 12 and 18 acts to cancel the vertical load acting on the center portion of the bridge girder 3 and reduce the bending moment at the center portion of the bridge girder. Assuming that the initial tension F is as close to zero as possible, it can be considered that the tension F (vertical component F2) acts on the cable 13 as a reaction force that cancels the live load L acting on the bridge girder 3.

  6 to 10 are diagrams showing the action of the bridge reinforcement device 10 obtained by the three-dimensional FEM analysis, and show the bending stress (maximum principal stress) of the existing bridge before and after the bridge reinforcement device 10 is installed. Changes are shown. 6 and 7 show changes in dead load stress, and FIGS. 8 to 10 show changes in live load stress. The live load is an L load (B load) defined as a loaded load in the Japan Road Association / Road Bridge Specification.

  In each figure, the horizontal axis indicates the position in the bridge axis direction, and the vertical axis indicates the maximum principal stress. At the top of each figure, the schematic shape of the bridge corresponding to the horizontal axis is shown for reference. The analysis target of the FEM analysis is a three-diameter continuous steel floor slab box girder bridge 1 having a total length of about 180 m having seven panels between one diameter, and a predetermined initial tension (500 kN) is applied to each cable 13. Analysis was performed under the introduced conditions.

FIG. 6 shows the relationship between the dead load stress of the lower flange portion of the 3-span continuous steel slab box girder bridge 1 and the position in the bridge axis direction. As shown in FIG. 6, there is no significant change in the tendency of stress properties of the entire bridge. However, in the vicinity of the saddle portions 12 and 18, a significant reduction in the maximum principal stress is observed. The stress reduction rate of the entire bridge was 22% on average, and a stress reduction effect was observed in any span between the center span and the side span. Therefore, it was found that the load carrying capacity of the entire girder can be improved by installing the bridge reinforcing device 10. In addition, the tendency of the stress property to rise by about 10 N / mm ² at a specific interval in the bridge axis direction appears in the diagram of FIG. This is a phenomenon that occurs because the deformation of the lower flange of the bridge girder 3 is constrained by a lateral rib (not shown) provided between the panels.

  FIG. 7 shows a change in the dead load stress before and after reinforcing the cable structure with respect to the steel deck slab truffle 9 between the center spans (FIG. 5).

  As shown in FIG. 7, in the range of the three panels in the vicinity of the center portion between the center diameters, the maximum principal stress acting on the steel deck slab truffle 9 increases after the cable structure reinforcement. This is due to the lifting action of the bridge girder 3 by the initial tension F.

  FIG. 8 shows the live load stress of the box girder lower flange of the entire bridge before and after reinforcing the cable structure.

  There is no significant change in the stress properties of the entire bridge before and after the reinforcement of the cable structure, but there are no places where the degree of stress increases in the bridge after reinforcement than before reinforcement. When the stress reduction rate before and after reinforcement is examined for each range in the direction of the bridge axis, the active load stress is reduced by an average of 23% for the entire bridge, 34% for the center diameter, 13% for the side diameter, and 71% for the girder end. Has occurred. Therefore, it has been found that the bridge reinforcing device 10 of the present invention contributes to the reduction of the live load stress over the entire bridge girder.

  In addition, the central region between the central diameters, the region near the beam ends between the central diameters, and the region near the beam ends between the side diameters showed a particularly high degree of stress before reinforcing the cable structure. Is reduced by about 30% in the central region between the central spans, and by about 65% in the region near the beam ends between the central spans and the side spans, and the active load stress by the bridge reinforcing device 10 of the present invention is reduced. The effect of reducing this is noticeable in these regions.

In FIG. 9, the live load stress acting on the steel deck slab truffle 9 (FIG. 5) between the center spans is shown in relation to the bridge axial position. The stress reduction rate of the steel deck slab truffle 9 by reinforcing the cable structure was about 6% between the center diameters. Further, in the central region of the center span, before the cable structure reinforcement, the stress of about 25 N / mm ² had been applied, after the cable structure reinforcement it was greatly reduced to about 2N / mm ^2. Therefore, the cable structural reinforcement not only reduces the primary stress acting on the bridge, but also enables the reduction of the live load stress of the steel deck slab truffle 9 (that is, the reduction of the secondary stress that cannot be considered in the design). It has been found.

Therefore, according to the above embodiment of the present invention, it has been found that the following effects can be obtained specifically.
(1) By reinforcing the cable structure of the present invention, the dead load stress can be reduced by an average of 22% over the entire bridge, and the load bearing capacity of the entire bridge girder can be improved.

(2) By reinforcing the cable structure of the present invention, the active load stress can be reduced by an average of 23% over the entire bridge, and the effect of reducing the active load stress that cannot be obtained by the conventional reinforcement method can be achieved.

(3) In the vicinity immediately above the support beam 19, the live load stress of the steel deck slab truffle 9 can be greatly reduced, and the secondary stress acting on the bridge can be reduced.

  Thus, according to the bridge reinforcing device 10 of the present invention, the stress of the existing steel road bridge as a whole is drastically reduced, the effect of reinforcing the entire bridge that cannot be obtained by the conventional reinforcement method, and the dead load stress. It is possible to reduce the live load stress that could not be realized by the conventional reinforcement method as well as the reduction of the load, and therefore the load resistance and durability of the existing steel road bridge can be improved.

  FIG. 10 shows a change in the active load stress reduction effect of the bridge reinforcing device 10 due to the difference in the height h of the tower 11, and FIG. 11 shows the first model and the second model shown in FIG. The structure of the 3 span continuous steel deck box girder bridge 1 is shown schematically.

  11A shows a first model in which the tower height h is set to the span length L / 5, and FIG. 11B shows a second model in which the tower height h is set to the span length L / 10. It is shown. In the second model, since the tower height h is halved compared to the first model, the vertical component F2 (FIG. 4) of the initial tension F is halved. In the cable structure reinforcement, it is considered that one of the main factors for reducing the stress of the girder is the vertical component F2 of the initial tension F. For this reason, the present inventor performed the FEM analysis with the initial tension F set to about twice in the second model in order to ensure the vertical component F2 equivalent to the first model.

  FIG. 10 shows the FEM analysis results of the first model and the second model. As shown in FIG. 10, the generated stresses of the first model and the second model are substantially the same, and no substantial difference between them is recognized. That is, in the bridge reinforcing device 10 of the present invention, the tower height h can be reduced by increasing the initial tension F. This means that a design that achieves both the reinforcing effect of the bridge reinforcing device 10 and its economy and workability can be adopted according to the present invention.

  The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the above-described embodiments, and various modifications or changes can be made within the scope of the present invention described in the claims. Is possible.

  For example, in the bridge reinforcing structures of Examples 2 to 4 above, the cables are turned downward at the tower top saddle, but a cable mooring device is provided at the top of each tower to divide the cables at each tower top. The end of each cable may be moored at the top of each tower.

  Further, the cross section (transverse section) of the tower can be designed in any form such as a square, a circle, an ellipse, a rectangle, and a rhombus.

  Further, in each of the above embodiments, the saddle portion of the bridge girder is arranged at the center portion of the span, but the saddle portion is disposed at a position unevenly distributed on one side of the span, or a plurality of saddle portions are spanned between the spans. It is also possible to arrange.

  The bridge reinforcing structure and the bridge reinforcing method of the present invention are applied to an external cable method for attaching a cable structure along a bridge girder in order to improve the load bearing capacity and durability of an existing bridge such as an existing steel road bridge. In particular, the present invention has a structure that can be advantageously used as a reinforcing structure and a reinforcing method for a steel floor slab box girder bridge. According to the bridge reinforcement structure and the bridge reinforcement method of the present invention, it is possible to prevent excessive axial force from being introduced into the bridge girder and to effectively reduce the stress acting on the bridge girder due to a live load. It is considered that the bridge reinforcement structure and the bridge reinforcement method of the present invention will exhibit a reinforcement effect close to the replacement of an existing bridge as a reinforcement method capable of achieving a reduction in the active load stress of the entire bridge, and its practical effect. Is remarkable.

DESCRIPTION OF SYMBOLS 1 Steel deck box girder bridge 2 Abutment 3 Bridge girder 4, 7 Roller bearing 5 Pin bearing 6 Bridge pier 9 Steel deck slab truffle 10 Bridge reinforcement device 11 Tower 12, 15, 17, 18 Saddle part 13 Cable 14 Cable mooring device 19 Support beam F Initial tension F1 Horizontal component F2 Vertical component R1 Horizontal reaction force R2 Vertical reaction force

Claims (10)

A cable stretched in the bridge length direction of the bridge; and a fulcrum forming member that is integrated with the bridge girder and that contacts the cable and turns the cable, and the fulcrum forming member is formed by a vertical component of tension acting on the cable. In the bridge reinforcement structure that reduces the bending stress of the bridge girder by applying upward force to
A tower erected on the structure or ground to transmit the tension of the cable to the structure or ground outside the bridge girder;
In order to transmit the horizontal component of the tension acting on the cable to the structure or the ground outside the bridge girder, the cable turned in the upper part of the tower and the fulcrum forming member is moored to the structure or the ground, or the fulcrum A bridge reinforcing structure comprising cable mooring means for mooring the cable turned in the forming member to the tower.   The bridge reinforcing structure according to claim 1, wherein the tower is erected on an abutment or a pier of the bridge.   3. The bridge reinforcing structure according to claim 1, wherein the fulcrum forming member includes a saddle for a bridge or a support member that protrudes from a lower portion of the bridge girder and is slidably contacted or rolled.   The cable mooring means has a mooring device for mooring an end portion of the cable to the upper portion of the tower, and the mooring device moors the cable turned upward by the fulcrum forming member to the tower. The bridge reinforcing structure according to any one of claims 1 to 3.   The tower includes a bridge saddle or a support member that slides or rolls on the cable, and the bridge saddle or support member turns the cable turned upward by the fulcrum forming member downward. The bridge reinforcing structure according to any one of claims 1 to 3.   The cable mooring means has a mooring tool for mooring a cable turned up and down by the bridge saddle or supporting member provided in the tower and the fulcrum forming member to the structure or the ground. The bridge reinforcing structure according to claim 5. A cable is stretched in the bridge length direction of the bridge, the cable is brought into contact with the fulcrum forming member integrated with the bridge girder, the cable is turned, and the vertical component of the tension acting on the cable is directed upward to the fulcrum forming member. In the bridge reinforcement method for reducing the bending stress of the bridge girder by applying force,
The cable turned by the upper part of the tower standing on the structure or ground outside the bridge girder and the fulcrum forming member is moored to the structure or ground outside the bridge girder, or the cable turned by the fulcrum forming member is A bridge reinforcing method, characterized in that the horizontal component of tension acting on the cable is supported by the reaction force of the structure or the ground.   The bridge reinforcing method according to claim 7, wherein an initial tension of the cable is applied in order to reduce the height of the tower.   The tower is erected on the abutment or pier of the bridge, or the ground, the cable turned upward by the fulcrum forming member is moored at the tower top of the tower, and the horizontal component of the tension acting on the cable is The bridge reinforcement method according to claim 7 or 8, wherein the bridge is transmitted to the abutment, pier or ground by a tower and supported by a reaction force of the abutment, pier or ground.   The tower is erected on the abutment or pier of the bridge, or on the ground, and the cable turned upward by the fulcrum forming member is turned downward at the tower top of the tower, and the cable is turned to the abutment, pier or The moored to the ground, the horizontal component of the tension acting on the cable is transmitted to the abutment, pier or ground, and supported by the reaction force of the abutment, pier or ground. Bridge reinforcement method.

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