Method for replacing vertical members of steel truss bridges

Abstract

To provide a safe and reliable vertical member replacement method for a steel truss bridge which does not cause a change in the structural system of an entire steel truss bridge before and after replacing vertical members.SOLUTION: In a vertical member replacement method for a steel truss bridge for replacing an existing vertical member 1 of a steel truss bridge B1, an axial force removal step is performed in which an upper chord 2 is jacked up and the compressive axial force acting on the existing vertical member 1 is removed by using an axial force removal device 10 that comprises a hydraulic jack 11 for lifting and jacking up the upper chord 2 connected to the existing vertical member 1 of the steel truss bridge B1, a temporary beam 12 for obtaining the reaction force of the hydraulic jack 11, and an upper chord lifting mechanism 13 combined with a steel material having an upper frame 15 and a lower frame 16 connected by a connecting steel member 17 inserted through a through hole h1 vertically penetrating a floor slab D1 of the steel truss bridge B1. Then, afterwards, the existing vertical member 1 is replaced with a newly installed vertical member 1'.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method for replacing vertical members of a steel truss bridge. [Background technology]

[0002] In recent years, bridges such as steel truss bridges built during periods of rapid economic growth have been partially corroded, forcing repairs due to aging and the need to replace some components. In particular, there has been an increase in cases of major component replacement, such as the replacement of vertical members in steel truss bridges. However, vertical members in steel truss bridges are not only the main components that bear dead and live loads at all times, but also play an important role in transmitting stresses due to earthquake loads and wind loads to the support points. For this reason, when replacing vertical members in a steel truss bridge, it is necessary to ensure that the entire steel truss bridge remains structurally stable and safe even after the vertical members are removed. Therefore, a construction method is required that does not change the overall structural system of the steel truss bridge before and after vertical member replacement.

[0003] For example, Patent Document 1 discloses a method of replacing components of a truss structure, in which a temporary chord 7 is attached between an upper chord 1 and a lower chord 2, and the temporary chord 7 and the upper chord 1 are connected with a plurality of temporary diagonal members 8 to form a temporary truss, and the lower ends of the lower chord 2 and the diagonal members 4 connected thereto are removed and a new lower chord and the lower ends of the new diagonal members are attached (see claim 1 in the scope of claims of Patent Document 1, paragraphs

[0022] to

[0033] of the specification, Figures 2 to 10 of the drawings, etc.).

[0004] Similarly, Patent Document 2 discloses a method of replacing components of a truss bridge, in which a temporary chord 7 is attached between an upper chord 1 and a lower chord 2, and the temporary chord 7 and the upper chord 1 are connected with a plurality of temporary diagonal members 8 to form a temporary truss, and the lower ends of the lower chord 2 and the diagonal members 4 connected to it are removed and a new lower chord and the lower ends of the new diagonal members are attached (see claim 1 in the scope of claims of Patent Document 1, paragraphs

[0023] to

[0034] of the specification, Figures 2 to 10 of the drawings, etc.).

[0005] However, the method of replacing components of a truss bridge (truss structure) described in Patent Documents 1 and 2 is an invention that allows the upper chord 1 to be replaced by attaching a straight "temporary chord 7" that extends from one end of the bridge axis to the other to form a temporary truss, thereby reducing the labor required to attach and detach the temporary chord 7.However, it cannot be directly applied to the replacement of vertical members, as it is necessary to form a temporary truss, which is time-consuming and requires further labor reduction. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2019-56230 A [Patent Document 2] Japanese Patent Application Publication No. 2019-178607 Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, the present invention was devised in consideration of the above-mentioned problems, and its purpose is to provide a safe and reliable method for replacing vertical members of a steel truss bridge that does not cause any changes to the structural system of the entire steel truss bridge before and after the replacement of the vertical members. [Means for solving the problem]

[0008] The method for replacing vertical members of a steel truss bridge according to claim 1 is a method for replacing existing vertical members of a steel truss bridge, A vertical member stress determination process is carried out to calculate the compressive axial force occurring in the existing vertical member by three-dimensional frame analysis and determine the stress occurring, and then An axial force removal device is used to jack up the upper chord member, which is connected to the existing vertical member of the steel truss bridge, by using an axial force removal device comprising: a hydraulic jack for lifting up and jacking up the upper chord member connected to the existing vertical member of the steel truss bridge; a temporary beam for obtaining the reaction force of the hydraulic jack; and an upper chord member lifting mechanism which is a combination of steel members having an upper frame and a lower frame connected by connecting steel members inserted into through holes which penetrate the deck of the steel truss bridge in the vertical direction. The axial force removal process removes the compressive axial force acting on the existing vertical member, and the existing vertical member is replaced with a new vertical member. In the axial force removing step, the axial stress acting on the existing vertical members is measured using a strain gauge, and jacking is performed while comparing it with the compressive axial force calculated by three-dimensional frame analysis. In the axial force removing step, the axial stress acting on the existing vertical members is removed, and a new vertical member installation step is performed to install new vertical members. After that, the existing vertical members are removed, and then the upper chord members are jacked down using the axial force removing device. In the axial force introducing step, a compressive axial force is introduced into the new vertical members while measuring the axial stress acting on the new vertical members using a strain gauge.It is characterized by:

[0010] Claim 2 The method for replacing vertical members of a steel truss bridge according to claim 1 is characterized in that in the axial force removal process, the bridge surface height directly above the existing vertical member is constantly measured with a laser level, and an alarm is issued when the displacement of the bridge surface height exceeds a predetermined control value.

[0011] Claim 3 The method for replacing vertical members of a steel truss bridge according to claim 1 or 2 In the method for replacing vertical members of a steel truss bridge, the axial force removal process is characterized in that a displacement limiting stopper is installed to limit horizontal displacement perpendicular to the bridge axis during an earthquake, thereby removing the compressive axial force acting on the existing vertical members.

[0014] Claim 4 The method for replacing vertical members of a steel truss bridge according to claim 1 In the method for replacing vertical members of a steel truss bridge according to the above, the existing vertical member removal process is characterized in that the existing vertical member is pulled outward in a direction perpendicular to the bridge axis using a trolley rail for a chain block, and then the existing vertical member is lifted and removed using a crane. [Effects of the Invention]

[0015] Claim 1~ 4 According to the present invention, the vertical members of a steel truss bridge can be replaced while ensuring structural stability, with no changes occurring to the structural system of the entire steel truss bridge before and after the replacement of the vertical members. Furthermore, according to the inventions of claims 1 to 4, jacking up using the axial force removal device for the actual construction work can be performed while comparing it with the compressive axial force calculated by three-dimensional frame analysis, and axial force removal can be performed while confirming the validity of the actual construction work, thereby reliably preventing unforeseen circumstances. Furthermore, according to the inventions of claims 1 to 4, it is possible to minimize the period in which the vertical members are unable to support dead loads and the like, thereby further improving the structural stability. Furthermore, according to the inventions of claims 1 to 4, a strain gauge is used to measure the axial stress acting on the newly installed vertical member while a compressive axial force is introduced into the newly installed vertical member, so that it is possible to confirm that the same load is re-transferred during jacking down as during jacking up, and it is possible to prevent any changes to the structural system after replacing the vertical member.

[0017] In particular, claims 2 According to the invention, the bridge surface height directly above the existing vertical members is constantly measured using a laser level, and an alarm is sounded if the displacement of the bridge surface height exceeds a predetermined control value, so that if an unexpected contingency occurs, immediate action can be taken to deal with and improve the situation.

[0018] In particular, claims 3 According to the invention, displacement limiting stoppers are installed to remove the compressive axial force of the existing vertical members, so that horizontal forces perpendicular to the bridge axis can be transmitted to the support parts via the displacement limiting stoppers, and structural stability can be ensured even if an earthquake occurs with the compressive axial force of the vertical members removed.

[0021] In particular, claims 4 According to the invention, the existing vertical members are pulled outward in a direction perpendicular to the bridge axis using a trolley rail for a chain block, and then lifted and removed using a crane, so that the existing vertical members can be removed safely in a short time. [Brief explanation of the drawings]

[0022] [Figure 1] Figure 1 is a photograph of the X-ray residual stress measurement situation showing the measurement being performed using the X-ray residual stress measurement device. [Figure 2] Figure 2 shows an FEM analysis model of axial force removal for calculating the jacking force. [Figure 3] FIG. 3 is a perspective view showing the axial force removing step of the vertical member replacement method for a steel truss bridge according to this embodiment. [Figure 4] FIG. 4 is a plan view showing the axial force removing step of the same. [Figure 5] FIG. 5 is a side view of the steel truss bridge showing the axial force removal process as viewed perpendicular to the bridge axis. [Figure 6] FIG. 6 is a perspective view mainly showing the configuration of each part of the axial force eliminating device used in the axial force eliminating step, which is installed above the deck slab. [Figure 7] FIG. 7 is an enlarged side view of part A in FIG. 5, mainly showing the configuration of each part installed above the deck of the axial force eliminating device. [Figure 8] FIG. 8 is a perspective view mainly showing the configuration of each part of the axial force eliminator installed below the deck slab. [Figure 9] FIG. 9 is a vertical cross-sectional view of a steel truss bridge cut along a direction perpendicular to the bridge axis, showing the configuration of each part of an axial force eliminating device. [Figure 10] Figure 10 is a process explanatory diagram showing the process of removing existing vertical members in the vertical member replacement method for a steel truss bridge in this embodiment, where (a) shows the vertical member being pulled out, and (b) shows the vertical member 1 being sling-loaded onto the crane hook. [Figure 11] FIG. 11 is a process explanatory diagram showing the removal process of the existing vertical members in the same manner, showing the state in which the vertical members are sling-hooked and lifted up onto the crane hook. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, one embodiment of a method for replacing vertical members of a steel truss bridge according to the present invention will be described in detail with reference to the drawings.

[0024] A method for replacing vertical members of a steel truss bridge according to an embodiment of the present invention will be described using Figures 1 to 11. The method will be described by taking as an example a case where vertical member 1 on the abutment side of a Warren truss steel truss bridge B1 with vertical members has corroded and deteriorated, and the existing vertical member 1 is replaced with a new vertical member 1' (see Figures 3, 8, etc.).

[0025] In order to replace vertical member 1 in a safe and reliable manner that does not cause any changes to the overall structural system of steel truss bridge B1, it is necessary to remove the compressive axial force due to the dead load acting on vertical member 1 and remove the existing vertical member 1 in a state where the structure is stabilized.

[0026] However, actual bridges have a plan curvature R (R = 600m for the bridge that was constructed) that curves to either the left or right depending on the road, and the truss chords are arranged so that they are bent at each point, which means that the deck overhang lengths on the left and right in the direction perpendicular to the bridge axis (towards the bridge width) change. As this causes different forces to be generated in the vertical members, when considering how to remove the forces acting on the existing vertical member 1 that will be replaced, it is necessary to understand in detail the compressive axial force currently acting on vertical member 1.

[0027] (1. Vertical material stress determination process) Therefore, in the method for replacing vertical members of a steel truss bridge according to this embodiment, first, a vertical member stress grasping step is carried out to grasp the stress occurring in the existing vertical member 1 to be replaced.

[0028] Specifically, the compressive axial force due to dead load occurring in vertical member 1 is calculated using three-dimensional frame analysis, and to verify the validity of the calculated compressive axial force, the axial stress acting on the actual vertical member 1 is measured using an X-ray residual stress measurement device, and the two are compared and verified.

[0029] Here, 3D frame analysis is a method of structural analysis that uses the finite element method (FEM), in which the element stiffness equation used in 2D stress analysis is expanded to the element stiffness matrix of a 3D 3D frame structure, and the element stiffness matrix is ​​solved by programming to calculate the stress of each member. 3D frame analysis reflects the results of on-site field surveys in addition to the 3D 3D frame structure based on the design calculations and drawings at the time of construction.

[0030] In addition, X-ray residual stress measurements are performed at the center of the steel plate width using an X-ray residual stress measurement device, as shown in the photograph of the X-ray residual stress measurement situation in Figure 1, and on four surfaces near the center of the vertical material 1.

[0031] The stress (compressive axial force) acting on the replacement vertical member 1 calculated by the spatial frame analysis of the spatial frame structural model according to this embodiment was 14 MPa. In contrast, the measurement result of the X-ray residual stress was 258 MPa.

[0032] The reason for this large discrepancy between the calculated stress from the three-dimensional frame analysis and the measured residual stress from X-rays is presumably because the measured residual stress included not only stress generated by load, but also residual stress generated during the steel plate manufacturing process, residual stress generated by welding during the component manufacturing process, and residual stress due to surface treatment.

[0033] Therefore, it was possible to infer that the residual stress measured by the X-ray residual stress measurement device was not stress generated due to unexpected loads or deformations, and the compressive axial force calculated by the three-dimensional frame analysis was adopted as the design value when removing the axial force, as described below.

[0034] (2. Jacking force calculation process) Next, in the method for replacing vertical members of a steel truss bridge according to this embodiment, a jacking-up force calculation step is carried out to calculate the planned jacking-up force.

[0035] Specifically, based on the compressive axial force calculated in the three-dimensional frame analysis described above, the jacking force required to remove the load on vertical member 1 in the subsequent process is calculated using an FEM analysis that recreates the axial force removal model shown in Figure 2. Figure 2 shows the FEM analysis model of axial force removal used to calculate the jacking force. In the FEM analysis of this axial force removal model, the required jacking force was calculated to be 307kN.

[0036] Additionally, because there were concerns that the jacking force would be large due to the rigidity of the deck D1 and wall parapet W1 when jacking up, a study was also conducted on a model in which the deck D1 and wall parapet W1 had been cut in advance. As a result, it was found that the jacking force could be reduced to about 70% by cutting the deck D1 and wall parapet W1.

[0037] (3. Axial force removal process) Next, as shown in Figures 3 to 5, in the method for replacing vertical members of a steel truss bridge according to this embodiment, an axial force removing step is performed in which the upper chord member 2 is jacked up using an axial force removing device 10 and the compressive axial force acting on the existing vertical member 1 to be replaced is removed. Figure 3 is a perspective view showing the axial force removing step in the method for replacing vertical members of a steel truss bridge according to this embodiment, and Figure 4 is a plan view showing the axial force removing step in the method for replacing vertical members of a steel truss bridge according to this embodiment. Also, Figure 5 is a side view of a steel truss bridge B1 viewed in a direction perpendicular to the bridge axis, illustrating the axial force removing step in the method for replacing vertical members of a steel truss bridge according to this embodiment.

[0038] <Axial force removal device> As shown in Figures 3 to 9, the axial force eliminator 10 is composed of a CH-type hydraulic jack 11 for lifting and jacking up the upper chord member, a temporary beam 12 that receives the reaction force of the hydraulic jack 11, and an upper chord member lifting mechanism 13 made up of steel members. Figure 6 is a perspective view mainly showing the components of the axial force eliminator 10 installed above the deck slab D1, and Figure 7 is an enlarged side view of part A in Figure 5 mainly showing the components of the axial force eliminator 10 installed above the deck slab D1. Figure 8 is a perspective view mainly showing the components of the axial force eliminator 10 installed below the deck slab D1, and Figure 9 is a vertical cross-sectional view of a steel truss bridge B1 cut along a direction perpendicular to the bridge axis to show the components of the axial force eliminator 10.

[0039] As shown in Figures 3 to 5, the temporary beam 12 is a beam material formed by joining a pair of left and right H-shaped steel beams 120, 121 (900 x 300 x 16 x 28) having a predetermined length that extends from above the truss top chord lattice point 3 of the steel truss to above the parapet 4 of the abutment P1 (see also Figure 9), and is placed on the deck D1 of the steel truss bridge B1. Of course, the temporary beam 12 is not limited to a pair of H-shaped steel beams, and may be other members such as channel steel or square steel pipes that have a predetermined length and bending rigidity sufficient to withstand jacking-up forces. As shown in Figure 9, a CH-type hydraulic jack 11 is fixed in the gap between the pair of H-shaped steel beams 120, 121 and the upper frame 15.

[0040] 3, 5 and 7, one longitudinal end of the temporary beam 12 is placed on a steel assembly frame 14 installed on the truss upper chord lattice point 3, and the other longitudinal end of the temporary beam 12 is placed on a steel assembly frame 14' installed on the parapet 4 of the abutment P1, so that the temporary beam 12 is spanned over the two steel assembly frames 14, 14'. The steel assembly frames 14, 14' are used for level adjustment to keep the temporary beam 12 horizontal according to the gradient of the deck D1.

[0041] As shown in Figures 3 to 9, the upper chord lifting mechanism 13 comprises an upper frame 15, which is made of steel members such as H-shaped steel members assembled in a planar H-shape, and a lower frame 16 that abuts against the underside of the upper chord member 2 or uses a frame or the like to lift the upper chord member 2 from below. These frames 15, 16 are connected by a plurality of connecting steel members 17 made of high-strength steel members such as Gebin bars, which are fully threaded PC steel bars. As shown in Figures 3, 5, 7, and 8, these connecting steel members 17 are inserted into through-holes h1 that are drilled to vertically penetrate the deck slab D1 of the steel truss bridge B1, connecting the upper frame 15 on the deck slab D1 to the lower frame 16 below the deck slab D1.

[0042] In this axial force removal process, the hydraulic jack 11 of the axial force removal device 10 is operated in the extension direction to lift the upper frame 15 placed on the hydraulic jack 11, thereby lifting the lower frame 16 connected to the upper frame 15 with connecting steel members 17. In this way, the axial force removal device 10 jacks up the upper chord member 2 on the lower frame 16, and as the upper chord member 2 lifts, the compressive axial force of the existing vertical member 1 connected to the upper chord member 2 is removed (see Figures 3 to 9). Note that the hydraulic jack 11 is not limited to the illustrated configuration interposed between the temporary beam 12 and the upper frame 15 to lift the upper frame 15, but may also be configured to be placed on the upper frame 15 and screw it up. In short, the hydraulic jack according to the present invention may be configured to hydraulically lift the upper chord member lifting mechanism 13, which is made up of steel members.

[0043] (3.1 Stress management by strain measurement) Furthermore, in the axial force removal process of the vertical member replacement method for a steel truss bridge according to this embodiment, when the compressive axial force of the vertical member 1 is removed in this axial force removal process, the condition of the member stress generated in the vertical member 1 during jacking up is monitored using a strain gauge previously installed in the vertical member 1. This is because construction errors are expected during actual construction, and unforeseen circumstances may occur.

[0044] Specifically, just like the X-ray residual stress measurement in the vertical member stress determination process, strain gauges are installed on four surfaces near the center of vertical member 1 at the center position of the plate width, and in addition to monitoring the compressive stress with the strain gauges, the tensile force generated in vertical member 1 by the reaction force of hydraulic jack 11 is also monitored. Also, by carrying out jacking up with hydraulic jack 11 in the actual axial force removal process while comparing with the design values ​​calculated in the three-dimensional frame analysis and FEM analysis mentioned above, the actual axial force removal process is carried out while comparing the transition of axial force between the plan and the actual construction to confirm its validity.

[0045] During the actual construction, the reaction force was gradually increased from 50% of the jacking force of 307kN, which was the design jacking force determined by FEM analysis. When 520kN, or 170% of the design jacking force, was applied, floating was confirmed visually and the strain measurement value reached the upper limit of 58με, so it was determined that the generated axial force had reached 0kN and the work was completed. The following table 1 shows the changes in strain measurements during jacking up in actual construction work.

[0046] [Table 1]

[0047] As shown in Table 1, the generated stress calculated from the strain measurement values ​​was 11.6 MPa, which was 81% of the 14.3 MPa generated stress calculated from the three-dimensional frame analysis. Note that faces A and C are faces facing in the direction of the bridge axis, and faces B and D are faces perpendicular to the bridge axis.

[0048] (3.2 Monitoring bridge surface height using a laser level) In addition, in the axial force removal process of the method for replacing vertical members of a steel truss bridge according to this embodiment, the bridge surface height is monitored using a laser level 19. This is to monitor whether or not a large vertical displacement has occurred in the actual bridge surface height during the jacking-up work.

[0049] Specifically, as shown in Figures 3 and 6, a laser sensor 20 is installed on the bridge surface directly above the vertical member 1 (top surface of deck D1), and a rotary laser level 19 is used to constantly measure the bridge surface height, monitoring the height displacement of the surface directly above the vertical member 1 caused by the jacking up mentioned above. This bridge surface height monitoring system constantly monitors the vertical displacement (level displacement) of the bridge surface, and if the displacement exceeds the control value of 3 mm, it sounds an alarm and turns on a red light to notify nearby workers, and an alert is sent to the mobile devices of those involved. This makes it possible to respond immediately to deal with and improve upon any unforeseen circumstances that may arise.

[0050] (3.3 Installation of displacement limiting stopper) Furthermore, in the method for replacing vertical members of a steel truss bridge according to this embodiment, assuming that an earthquake will occur with the vertical members 1 removed, displacement limiting stoppers 5 are installed to limit horizontal displacement perpendicular to the bridge axis during an earthquake (see Figure 6, etc.). This is to ensure structural stability even during an earthquake.

[0051] When the existing vertical member 1 has been removed or when the upper chord member 2 has been jacked up and no axial force has been introduced into the newly installed vertical member 1', the function of transmitting horizontal forces perpendicular to the bridge axis to the support is lost. To compensate for this, the vertical member replacement method for a steel truss bridge according to this embodiment involves installing displacement limiting stoppers 5 that transmit horizontal forces perpendicular to the bridge axis via the wall parapet W1. The design horizontal seismic intensity applied to the member design of the displacement limiting stoppers 5 is set to 1 / 2 of a Level 2 earthquake motion.

[0052] As shown in Figures 4 and 6, the displacement limiter stopper 5 is a component primarily consisting of a pair of left and right H-shaped steel beams 50, 51 to which stiffener plates have been welded to increase bending rigidity. These H-shaped steel beams 50, 51 are connected with steel rods (bolts) and sandwich the wall parapet W1 of the steel truss bridge B1 via shock absorber rubber, which prevents damage to the wall parapet W1. This displacement limiter stopper 5 is installed on the boundary between abutment P1 and steel truss bridge B1, and by sandwiching the wall parapet W1 on the parapet 4 of abutment P1 and the wall parapet W1 of the steel truss bridge B1, it partially replaces the function of transmitting the horizontal force perpendicular to the bridge axis of the steel truss bridge B1 to the support (see also Figure 11).

[0053] (4. New vertical member installation process) Next, as shown in Figures 3 and 8, in the method for replacing vertical members of a steel truss bridge according to this embodiment, a new vertical member installation step is carried out in which a new vertical member 1' is installed in a state in which the axial force acting on the existing vertical member 1 has been removed in the axial force removal step. The position where the new vertical member 1' is installed is on the side of the truss upper chord member lattice point 3 near the existing vertical member 1 to be replaced (see also Figure 10).

[0054] In this process, the upper chord 2 is jacked up and lifted, and a new vertical member 1' is installed nearby without axial force acting on the existing vertical member 1. For this reason, the new vertical member 1' is hoisted with a lifting machine C1 such as a crane and carried to the outside of the steel truss bridge B1 near the installation location, and from there the new vertical member 1' is pulled laterally (inward in the direction perpendicular to the bridge axis) below the upper chord 2 and bolted together, allowing the new vertical member 1' to be installed in the specified location extremely easily and quickly.

[0055] (5. Removal of existing vertical materials) Next, as shown in Figures 10 and 11, the method for replacing vertical members of a steel truss bridge according to this embodiment involves an existing vertical member removal step in which the existing vertical member 1 is removed. Figure 10 is a process explanatory diagram showing the existing vertical member removal step of the method for replacing vertical members of a steel truss bridge according to this embodiment, where (a) shows the vertical member being pulled out and (b) shows the vertical member 1 being sling-hung onto the crane hook. Also, Figure 11 is a process explanatory diagram showing the existing vertical member removal step of the method for replacing vertical members of a steel truss bridge according to this embodiment, showing the vertical member 1 sling-hung onto the crane hook.

[0056] Specifically, as shown in Figure 10(a), the connecting bolts of the existing vertical member 1 are removed, and then the existing vertical member 1 is pulled outward in a direction perpendicular to the bridge axis using a trolley rail 6 for a chain block.Then, as shown in Figures 10(b) and 11, the existing vertical member 1 is slung onto the hook of a lifting machine C1 such as a crane and lifted up and removed.

[0057] (6. Axial force introduction process) Next, in the method for replacing vertical members of a steel truss bridge according to this embodiment, the upper chord member 2 is jacked down using the aforementioned axial force removal device, and an axial force introduction process is carried out to introduce compressive axial force into the newly installed replaced vertical member 1'.

[0058] Specifically, in the illustrated embodiment, the hydraulic jack 11 of the axial force eliminator 10 is operated in the contracting direction to lower the upper frame 15 placed on the hydraulic jack 11, and the lower frame 16 connected to this upper frame 15 by connecting steel members 17 is also lowered. In this way, the axial force eliminator 10 jacks down the upper chord member 2 on the lower frame 16, and as the upper chord member 2 lowers, a compressive axial force is introduced into the newly installed vertical member 1' connected to this upper chord member 2.

[0059] Here, in order to prevent any changes to the structural system after replacing the vertical members, it is necessary to confirm that the same load is transferred again during jacking down as during jacking up. Therefore, strain gauges are installed on the four central faces of the newly installed vertical member 1' to measure strain during jacking down as well.

[0060] The following Table 2 shows the changes in strain measurements during jacking down in actual construction work.

[0061] [Table 2] As shown in Table 2, the strain amount reached its upper limit at 67με, and the generated stress calculated from the strain value obtained by measurement was 13.4MPa, which was 94% of the generated stress of 14.3MPa calculated from the three-dimensional frame analysis. This made it possible to quantitatively confirm through numerical values ​​that the existing vertical member 1 before replacement and the new vertical member 1' after replacement were subjected to the same axial force, and it was confirmed that the load was able to be re-transferred without any problems.

[0062] According to the method for replacing vertical members of a steel truss bridge according to the embodiment of the present invention described above, the vertical member 1 of the steel truss bridge B1 can be replaced while ensuring structural stability so that there are no changes to the structural system of the entire steel truss bridge B1 before and after the vertical member replacement.

[0063] Although the method for replacing vertical members of a steel truss bridge according to an embodiment of the present invention has been described in detail above, the above-described and illustrated embodiments are merely examples of specific embodiments for carrying out the present invention, and therefore the technical scope of the present invention should not be interpreted as being limited by these embodiments.

[0064] In particular, the position of the replacement vertical member 1 has been exemplified as being the vertical member closest to the abutment P1, but it goes without saying that it can also be applied to other positions.In that case, the positions where the platform on which the temporary beam 12 is placed can be set at the truss upper chord member point 3 of the steel truss and another truss upper chord member point, and the temporary beam 12 can be spanned between them. [Explanation of symbols]

[0065] B1: Steel truss bridge P1: Abutment D1: Floor slab W1: Wall parapet h1: Through hole C1: Lifting machine 1: Existing vertical member (vertical member) 1': New vertical member (vertical member) 2:Top chord material 3: Truss top chord score 0 4: Parapet (bridge abutment) 5: Displacement limit stopper 50,51:H-beam steel 6: Chain block trolley rail 10: Axial force removal device 11: Hydraulic jack 12: Temporary beam 120,121:H-beam steel 13: Upper chord lifting mechanism 14,14': Steel assembly frame 15: Upper frame (frame: upper chord lifting mechanism) 16: Lower frame (frame: upper chord lifting mechanism) 17: Connecting steel (Kevin pole: PC steel) 18: Steel assembly stand 19: Rotating laser level (laser level) 20: Laser sensor

Claims

1. A method for replacing existing vertical members of a steel truss bridge, comprising: A vertical member stress assessment process is carried out to calculate the compressive axial force occurring in the existing vertical member by three-dimensional frame analysis and assess the stress occurring in the vertical member. Then, an axial force removal process is carried out in which the upper chord is jacked up using an axial force removal device equipped with an upper chord lifting mechanism that combines steel materials having an upper frame and a lower frame connected by connecting steel materials inserted into through holes that penetrate the deck of the steel truss bridge vertically, and the compressive axial force acting on the existing vertical member is removed. The existing vertical members will be replaced with new vertical members, In the axial force removal process, the axial stress acting on the existing vertical member is measured using a strain gauge, and the jacking is performed while comparing it with the compressive axial force calculated by the three-dimensional frame analysis. A new vertical member installation step is performed to install a new vertical member in a state where the axial force acting on the existing vertical member is removed in the axial force removal step; Thereafter, an existing vertical member removal step is performed to remove the existing vertical member, An axial force introduction step is performed in which the upper chord member is jacked down using the axial force removal device, and a compressive axial force is introduced into the newly installed vertical member while measuring the axial stress acting on the newly installed vertical member using a strain gauge. A method for replacing vertical members of a steel truss bridge, characterized by the above.

2. In the axial force removal process, the bridge surface height directly above the existing vertical members is constantly measured using a laser level, and an alarm is issued when the displacement of the bridge surface height exceeds a predetermined control value.

2. The method for replacing vertical members of a steel truss bridge according to claim 1 .

3. In the axial force removal process, displacement limiting stoppers are installed to limit horizontal displacement perpendicular to the bridge axis during an earthquake, thereby removing the compressive axial force acting on the existing vertical members.

3. A method for replacing vertical members of a steel truss bridge according to claim 1 or 2.

4. In the existing vertical member removal process, the existing vertical member is pulled outward in the direction perpendicular to the bridge axis using a chain block trolley rail, and then lifted and removed with a lifting machine.

2. The method for replacing vertical members of a steel truss bridge according to claim 1 .

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