Bridge pier repair methods

Abstract

Repair the bridge piers using a simpler procedure. [Solution] The present invention relates to a method for repairing a bridge pier 1 including a reinforced concrete upper beam 4. The repair method comprises a compression force application step of applying a compressive force in the X direction to the upper beam 4 of the bridge pier 1, and a repair step of repairing the upper surface 41 of the upper beam 4 while the compressive force is applied. The repair step includes removing concrete from the upper surface 41 of the upper beam 4 and filling the portion of the upper beam 4 from which the concrete was removed with new concrete or mortar.

Description

Technical Field

[0001] The present invention relates to a method for repairing bridge piers.

Background Art

[0002] Since the bridge piers and floor slabs of bridges are generally made of reinforced concrete, there are cases where it is necessary to repair damaged parts caused by aging deterioration of the concrete. Patent Document 1 describes a method for repairing a floor slab in which the bottom surface of the floor slab is peeled off, the reinforcing bars are exposed, and then mortar is filled.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] For the bridge piers of bridges, repairs are also carried out by the same method as described in Patent Document 1. However, the floor slab support part of the bridge pier often has a beam structure. In the case of a bridge pier structure including a cantilever beam such as a T-shaped bridge pier, tensile stress is applied to the upper end reinforcing bars of the beam. Therefore, when the concrete on the upper surface of the beam is peeled off and the upper end reinforcing bars are exposed, the integrity between the upper end reinforcing bars and the concrete is lost, and there is a possibility that the strength of the beam cannot be ensured. For this reason, a temporary support called a vent support is also used to take over the weight of the beam, but it takes a lot of labor for the preliminary preparation and the removal of the vent support.

[0005] An object of the present invention is to provide a method for repairing a bridge pier that can be implemented with a simpler procedure.

Means for Solving the Problems

[0006] The present invention relates to a method for repairing a bridge pier including a reinforced concrete superbeam. The repair method comprises a compression application step of applying a compressive force in the longitudinal direction of the superbeam of the bridge pier, and a repair step of repairing the upper surface of the superbeam while the compressive force is applied. The repair step includes removing concrete from the upper surface of the superbeam and filling the portion of the superbeam from which the concrete was removed with new concrete or mortar. [Effects of the Invention]

[0007] According to the present invention, a method for repairing bridge piers that can be carried out with simpler procedures can be provided. [Brief explanation of the drawing]

[0008] [Figure 1] This is a front view of the bridge piers and the deck slabs installed on them. [Figure 2] This is a top view of the bridge pier as seen from line AA in Figure 1. [Figure 3] This is a schematic diagram of the repair process for bridge piers. [Figure 4] This is a conceptual diagram showing the main steps of the compression force application process. [Figure 5] This is a plan view showing the division of the repair section. [Figure 6] This is a conceptual diagram showing the main steps of the repair process. [Figure 7] This figure shows the results of the stress check of the upper reinforcement bars in the upper beam. [Figure 8] This is a schematic diagram showing a modified form of a bridge pier. [Modes for carrying out the invention]

[0009] An embodiment of the bridge pier repair method of the present invention will be described with reference to the drawings. The bridge pier targeted by this embodiment includes a reinforced concrete superbeam. In the following description and drawings, the X direction is the horizontal direction parallel to the longitudinal direction of the superbeam of the bridge pier, the Y direction is the horizontal direction parallel to the short direction (width direction) of the superbeam, and the Z direction is the vertical direction. The X, Y, and Z directions are orthogonal to each other. Figure 1 is a front view of the bridge pier 1 to be repaired, and the steel frame section 2 and deck slab 3 installed on the bridge pier 1, and Figure 2 is a top view of the bridge pier 1 as seen from line AA in Figure 1. For convenience, the upper reinforcement bars 11 are shown in Figure 2.

[0010] The bridge pier 1 has an upper beam 4, a leg 5 connected to the center of the upper beam 4, a base 6 connected to the lower end of the leg 5, and a plurality of steel bearings 7 supported by the upper beam 4. The parts other than the bearings 7 are made of reinforced concrete (hereinafter sometimes referred to as RC). The upper beam 4 and the leg 5 are generally T-shaped. The upper beam 4 has cantilevered projections 8 extending on both sides from the base 9, which is the connection point with the leg 5, and the cross-section of the projections 8 decreases from the base 9 towards the end 10. The upper surface 41 of the upper beam 4 is horizontal, and the bottom surface 42 extends diagonally upward in the Z direction from the base 9 towards the end 10. The side surfaces 43 at both ends of the upper beam 4 in the X direction are planes parallel to the Z direction. The upper surface 41 of the upper beam 4 may be inclined from the horizontal direction. The bearings 7 support the steel girder 2, and the steel girder 2 supports the deck slab 3. The support 7 is fixed to the upper surface 41 of the upper beam 4 by anchor bolts (not shown).

[0011] Multiple upper reinforcement bars 11 are provided near the upper surface 41 of the upper beam 4, extending along the upper surface 41 with a predetermined concrete cover thickness. Multiple lower reinforcement bars 12 are provided near the bottom surface 42 of the upper beam 4, extending along the bottom surface 42 with a predetermined concrete cover thickness. Viewed from the Z direction, the multiple upper reinforcement bars 11 extend parallel to the X direction, and the multiple lower reinforcement bars 12 also extend parallel to the X direction. In addition, although not shown in the figures, shear reinforcement bars and the like extending in the Y and Z directions are provided.

[0012] Next, the repair method for pier 1 will be explained. The surface of the RC section of pier 1 may suffer damage such as cracks, corner collapse, delamination, and spalling due to various causes such as salt damage and carbonation of the concrete. In order to repair the damaged area of ​​the RC section, the concrete in that area is removed (chipped away), and new concrete or mortar (hereinafter referred to as new concrete, etc.) is filled into the area where the concrete was removed. Damage can occur in any part of the RC section of pier 1, but the upper surface 41 of the upper beam 4 requires particular attention. This is for the following reasons.

[0013] When repairing the RC section of pier 1, depending on the extent of the damage, concrete may be removed to a depth where the reinforcing bars are exposed. On the other hand, tensile forces act on the upper part of the upper beam 4, and these tensile forces are borne by the upper reinforcement bars 11. Repairs to pier 1 are often carried out while the bridge is in service, and the upper beam 4 is subjected not only to its own weight but also to the weight of vehicles, etc. Therefore, if the upper reinforcement bars 11 are exposed and the unity between the upper reinforcement bars 11 and the concrete is lost, the cross-sectional area that bears the tensile forces of the upper beam 4 will decrease, which could have a significant impact on the structural strength. In contrast, the bottom surface 42 of the upper beam 4 is subjected to compressive loads, so the impact of the exposure of the lower reinforcement bars 12 is relatively small. Also, shear reinforcement bars are placed near the four sides of the upper beam 4, but the impact of the exposure of the shear reinforcement bars is not so large. For the leg section 5 and the foundation section 6, compressive forces mainly act in the Z direction, so the impact of the exposure of the reinforcing bars is small. For the reasons above, this embodiment will mainly describe the repair method for the upper surface 41 of the upper beam 4.

[0014] Figure 3 shows an outline of the repair method. The repair method consists of a preparation step S1, a compressive force application step S2, a repair step S3, and a removal step S4. These steps will be explained in order below. First, as the preparation step S1, strain gauges 13 are attached to the upper reinforcement bars 11 (step S11). Specifically, a portion of the concrete on the upper surface 41 of the upper beam 4 is removed, a portion of the upper reinforcement bars 11 is exposed, and strain gauges 13 are attached to the exposed upper reinforcement bars 11. The strain gauges 13 measure the tensile stress of the upper reinforcement bars 11. As shown in Figure 2, three strain gauges 13 are attached to the upper reinforcement bars 11 near the center in the Y direction and on both ends, but the number and position of the strain gauges 13 to be attached are not limited to this. In the compressive force application step S2 and the repair step S3, the tensile stress of the upper reinforcement bars 11 may fluctuate, so the tensile stress of the upper reinforcement bars 11 is monitored to ensure that it does not become excessive during these steps. Therefore, it is preferable to monitor the tensile stress of the upper reinforcement 11 until the compression force application process S2 and the repair process S3 are completed. Note that the preparation process S1 is optional and can be omitted.

[0015] Figure 4 is a conceptual diagram showing the main steps of the compression force application process S2. Figures 4(a) and 4(b) are partial top and side views, respectively, showing the mounting method of the anchoring jig 14, and Figures 4(c) and 4(d) are partial top and side views, respectively, showing the mounting method and tensioning method of the tensioning member 19, respectively. All of these show only the vicinity of the left side surface 43 of the upper beam 4 in Figures 1 and 2. For convenience, Figures 4(a) and 4(b) are shown as exploded views. Although not illustrated or explained, the same work is performed on both ends of the upper beam 4's side surfaces 43 in the X direction. That is, the same work is performed on the right side surface 43 of the upper beam 4 in Figures 1 and 2 as on the left side surface 43.

[0016] In the compression force application step S2, first, as shown in Figs. 4(a) and 4(b), unevenness adjustment mortar 17 is applied to the side surface 43 of the upper beam 4 to perform unevenness adjustment (step S21). This is to flatten the mounting surface of the fixing jig 14 attached to the side surface 43. It is preferable to perform unevenness adjustment after repairing the damaged part of the side surface 43 if necessary. Next, a fixing jig 14 for attaching the tension member 19 is attached to the side surface 43 of the upper beam 4 (more precisely, the surface of the unevenness adjustment mortar 17) (step S22). The fixing jig 14 has a frame 15 and a plate-shaped supporting metal fitting 16, and the supporting metal fitting 16 is installed between the unevenness adjustment mortar 17 and the frame 15. The frame 15 and the supporting metal fitting 16 are fixed to the side surface 43 with anchor bolts (not shown). The frame 15 can be composed of H-shaped steel or channel steel, and its shape is not limited as long as the tension member 19 can be attached and fixed. In this embodiment, since two upper and lower stages of tension members 19 are installed, the frame 15 is also provided in two upper and lower stages, but these may be integrated. As shown in Fig. 4(a), the length D1 (dimension in the Y direction) of the frame 15 is longer than the width D2 (dimension in the Y direction) of the upper beam 4, and it protrudes outward in the Y direction from the side surface 43 of the upper beam 4.

[0017] Next, as shown in Figs. 4(c) and 4(d), the tension member 19 is attached to the upper beam 4 via the fixing jig 14 (step S23). Tension member attachment portions 18 to which the tension member 19 is to be attached are provided at portions of the frame 15 that protrude from the upper beam 4 to both sides in the Y direction. Through holes (not shown) for inserting the tension member 19 are provided in the tension member attachment portions 18. The tension member 19 is inserted into the through hole, and the tension member 19 is set so that both ends protrude outside the through hole. Next, the tension member 19 is tensioned by a jack (not shown) to apply a tensile force to the tension member 19, and the state is held by a fixing tool 20 (step S24). As a result, a compressive force is applied to the upper beam 4 of the pier 1 in the X direction. The tension member 19 is not limited as long as it is a rod-shaped member capable of applying a tensile force, and PC steel bars or PC steel wires can be used. In this embodiment, four Gevinde steel bars, which are often used in temporary construction, are used. The fixing tool 20 can be a general one such as a screw type or a wedge type.

[0018] As shown in Fig. 4(d), in order to efficiently apply a compressive force to the upper part of the upper beam 4, it is preferable to attach the tension member 19 at least at the same height position as the upper half 44 of the side surfaces 43 on both sides of the upper beam 4. Thereby, the tensile stress applied to the upper end bars 11 of the upper beam 4 can be efficiently reduced. In the present embodiment, the tension member 19 is also provided at the same height as the lower half parts 45 of the side surfaces 43 on both sides. When the upper surface 41 of the upper beam 4 is inclined in the horizontal direction, the Z-direction positions of the upper half part 44 and the lower half part 45 are different for the two side surfaces 43. Also in this case, at least one tension member 19 extending above the line 47 connecting the midpoints 46 of the side surfaces 43 on both sides may be provided on each of the two sides of the upper beam 4 in the Y direction.

[0019] Next, the repair process S3 is performed. Fig. 5 is a plan view showing the division of the repair section, and Fig. 6 is a cross-sectional view taken along the line B-B of Fig. 5 showing the main processes of the repair process S3. The repair of the upper surface 41 of the upper beam 4 is performed in a state where a compressive force is applied to the upper beam 4. The repair process S3 of the upper surface 41 of the upper beam 4 is preferably sequentially performed for each repair section partitioned in the Y direction of the upper beam 4. In the present embodiment, the repair target portion of the upper surface 41 of the upper beam 4 is divided into 5 parts in the Y direction and 2 parts in the X direction. Therefore, the repair target portion is divided into 10 repair sections (hereinafter referred to as the first to tenth repair sections A1 to A10). The repair is performed for each repair section. In the present embodiment, the repair is performed in the order of the repair sections A3, A2, A4, A1, A5, and then in the order of the repair sections A8, A7, A9, A6, A10. The repair process S3 for each repair section includes a process of removing the concrete from the upper surface 41 of the upper beam 4 (process S31) and a process of filling the portion of the upper beam 4 from which the concrete has been removed with new concrete or the like (process S32). Here, it is assumed that the upper end bars 11 are exposed when the concrete is removed, but depending on the degree of damage to the concrete on the upper surface 41 of the upper beam 4, the upper end bars 11 may not be exposed.

[0020] More specifically, first, as shown in Figure 6(a), the concrete in repair section A3 is removed to expose the upper reinforcement bars 11. Concrete removal (chipping) can be done using common methods such as water jetting. Next, as shown in Figure 6(b), new concrete or similar material C is filled into repair section A3. Next, as shown in Figure 6(c), the concrete in repair section A2 is removed to expose the upper reinforcement bars 11. Next, as shown in Figure 6(d), new concrete or similar material C is filled into repair section A2. Although not shown, the same procedure of concrete removal and filling with new concrete or similar material C is followed for repair section A4 as with repair section A2. Next, as shown in Figure 6(e), the concrete in repair section A1 is removed to expose the upper reinforcement bars 11. Next, as shown in Figure 6(f), new concrete or similar material C is filled into repair section A1. Although not shown, the same procedure of concrete removal and filling with new concrete or similar material C is followed for repair section A5 as with repair section A1.

[0021] It is preferable that two repair sections to be repaired consecutively be as far apart as possible in the Y direction and be symmetrical with respect to the X-direction central axis of the upper surface 41 of the upper beam 4. If the repair work is carried out sequentially from one end to the other in the Y direction (for example, in the order of A1, A2, A3, A4, A5), the tensile stress generated in the upper reinforcement 11 may differ significantly on both sides in the Y direction. Repair sections A1-A5 and repair sections A6-A10 may be carried out in either order, and the repairs to repair sections A1-A10 may be carried out as a single unit (for example, in the order of A3, A8, A2, A7, A4, A9, A1, A6, A5, A10). Repairs may also be carried out together without dividing the repair sections in the X direction (for example, A3 and A8 may be treated as a single repair section). The number of divisions in the Y-direction repair section is not limited, but it is preferable to divide the upper beam 4 into at least three repair sections in the Y-direction, and it is preferable to carry out the repair process S3 from the inner repair section in the Y-direction toward the outer repair section in the Y-direction (for example, in the order of A3, A2, A4, A1, A5), or from the outer repair section in the Y-direction toward the inner repair section in the Y-direction (for example, in the order of A1, A5, A2, A4, A3).

[0022] Once all repair sections have been completed, the tensioning members 19 and anchoring jigs 14 are removed as part of the removal process S4 (process S41). Since the repair of each part of the RC section of the pier 1, excluding the upper surface 41 of the upper beam 4, can be carried out even when no compressive force is applied to the upper beam 4, the timing of the repair is not particularly limited.

[0023] Next, the effects of this embodiment will be described. When the upper surface 41 of the upper beam 4 is repaired, if the upper reinforcement bars 11 are exposed, the integrity between the upper reinforcement bars 11 and the concrete is lost in the exposed area. Therefore, in terms of design, it is appropriate to assume that all of the upper reinforcement bars 11 in the repair area will be exposed, and that the exposed upper reinforcement bars 11 cannot bear tensile stress. However, in this embodiment, since a compressive force is applied to the upper beam 4 by the tensioning member 19, the tensile stress that the upper reinforcement bars 11 should bear is reduced, and in some cases becomes zero. In addition, since the repair of the upper surface 41 of the upper beam 4 is carried out section by section, the upper reinforcement bars 11 that are not exposed (i.e., the upper reinforcement bars 11 outside the repair section) can share and bear the tensile stress that the exposed upper reinforcement bars 11 were bearing. In this case, the increase in tensile stress is offset or reduced by the tensioning member 19, so it is possible to suppress or prevent the increase in tensile stress on the upper reinforcement bars 11 that are not exposed, and in some cases the tensile stress can be reduced or made zero. If the tensioning member 19 can apply sufficient compressive force to the upper beam 4, the entire repair area of ​​the upper surface 41 of the upper beam 4 can be repaired at once without dividing the upper surface 41 into multiple repair sections.

[0024] Furthermore, this embodiment is simple in procedure and superior to conventional methods in many respects. Conventionally, for example, a method is used in which bent supports are installed to transfer the load of the upper beam 4. In this case, in addition to the construction and removal of the bent supports, it may be necessary to improve the ground supporting the bent supports. Alternatively, there may be obstacles on the surface or underground. It is conceivable to temporarily suspend the use of the bridge to eliminate live loads such as automobiles, but this has a significant social impact, especially for bridges with heavy traffic. Although this embodiment requires a temporary work area on the surface for the installation and removal of the anchoring jig 14, it does not occupy a ground area during repair work like bent supports do. Moreover, the repair work can be carried out without suspending the use of the bridge.

[0025] Figure 7 shows the results of a stress check of the upper reinforcement bars 11 on an actual bridge pier. Figure 7(a) is a front view of the upper beam 4 of the bridge pier, and Figure 7(b) is a cross-sectional view thereof. The cross-sectional area for the stress check is the base P1 and P2 of the protruding portion 8 of the upper beam 4. Figure 7(c) shows the tensile stress of the upper reinforcement bars 11. The stress check was performed on the upper reinforcement bars 11 at the center and ends in the Y direction of two bridge piers A and B (see Figure 7(b)), and the stress before repair at the check cross-section P1 of bridge pier A was normalized to 100. The repair section is divided into 5 sections in the Y direction, but as shown in Figure 7(b), in the stress check, the upper reinforcement bars 11 near the actual repair section 51 were also considered unable to bear tensile force, and a section 52 wider than the actual repair section 51 was designated as the concrete defect section. When no compressive force was applied, the tensile stress of the upper reinforcement bars 11 increased in all cases compared to before repair. When a compressive force was applied, the tensile stress of the upper reinforcement bar 11 decreased in all cases compared to before the repair.

[0026] Although embodiments of the present invention have been described above, the present invention is not limited to these embodiments. For example, the shape of the target bridge pier 1 is not limited to a T-shape, but can take various shapes as shown in Figure 8. Figure 8(a) shows a structure in which the upper beam 4 extends in only one direction from the top of the leg portion 5, Figure 8(b) shows a structure in which the upper beam 4 is connected to the top of one of the two leg portions 5 of a portal structure, and Figure 8(c) shows a portal structure in which the upper beam 4 is provided between the two leg portions 5. However, the present invention is not limited to these and can be applied to any bridge pier having an upper beam 4 that supports the deck slab 3. Among the structures shown in Figure 8, the configurations in Figures 8(a) and 8(b), which include a cantilever beam, have greater effects of the present invention. The present invention can also be applied to the replacement of the bearing 7. The work to replace the bearing 7 includes removing concrete from the upper surface 41 of the upper beam 4 and filling the portion of the upper beam 4 from which the concrete was removed with new concrete, so a situation similar to that of repair work on the upper surface 41 of the upper beam 4 occurs. [Explanation of Symbols]

[0027] 1 Bridge pier 4 Upper beam 11 Upper end reinforcement 13 Strain Gauges 14 Fixing jig 15 Frame 18 Tensioner mounting section 19 Tensor material 41 Upper surface of the upper beam A1-A10 Repair Section

Claims

1. A method for repairing a bridge pier, including a reinforced concrete upper beam, A step of applying compressive force to the upper beam in the longitudinal direction, A repair process in which the upper surface of the upper beam is repaired while the aforementioned compressive force is applied, It has, A method for repairing a bridge pier, comprising the repair steps of removing concrete from the upper surface of the upper beam and filling the portion of the upper beam from which the concrete was removed with new concrete or mortar.

2. The method for repairing a bridge pier according to claim 1, wherein the repair process is carried out sequentially for each repair section divided in the width direction of the upper beam.

3. The upper beam is divided into at least three repair sections in the width direction, The method for repairing a bridge pier according to claim 2, wherein the repair step is performed from the repair section on the inside in the width direction toward the repair section on the outside in the width direction, or from the repair section on the outside in the width direction toward the repair section on the inside in the width direction.

4. The aforementioned compression force application step is, Tensioning fixtures are attached to both side surfaces of both ends of the upper beam in the longitudinal direction. A method for repairing a bridge pier according to any one of claims 1 to 3, comprising attaching the tensioning member to the upper beam via the anchoring jig and applying tensile force to the tensioning member.

5. The fixing jig has a frame attached to both sides of the upper beam, The frame has tension member attachment portions that extend from both sides of the upper beam in the width direction to both sides of the upper beam, The method for repairing a bridge pier according to claim 4, wherein the tensioning member is attached to the tensioning member attachment portion.

6. The method for repairing a bridge pier according to claim 5, wherein the tensioning member is attached at the same height as at least the upper half of both sides of the upper beam.

7. A method for repairing a bridge pier according to any one of claims 1 to 3, comprising exposing a portion of the upper reinforcement bars of the upper beam and attaching strain gauges to the upper reinforcement bars before the aforementioned repair process.

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