Crushing method for composite girder deck slabs

Abstract

To provide a method for crushing a deck slab of a composite girder including block dowels, which can crush not only the concrete around the block dowels but also the concrete between the block dowels by using an impact generator even when the distance between the adjacent block dowels is long. [Solution] The first impact generating agent 15a is arranged inside the ring shape formed by the base 9 of the block dowel 4 and the dowel ring 10 in a plan view, and diagonally below the dowel ring 10 when viewed from the bridge width direction. The second impact generating agent 15b is arranged on the opposite side of the base 9 from the first impact generating agent 15a in a plan view. The third impact generating agent 15c is arranged between the first impact generating agent 15a and the second impact generating agent 15b, which are located between adjacent block dowels 4. A worker detonates multiple impact generating agents 15 at approximately the same time.

Description

[Technical Field]

[0001] The present invention relates to a method for crushing a deck in a composite girder including a steel main girder and a reinforced concrete deck integrated by block dowels. [Background technology]

[0002] The deck of a composite girder is a reinforced concrete deck that is integrated with the main steel girders by embedding shear connectors on the top surface of the main steel girders. Block dowels are sometimes used as shear connectors. Block dowels, also known as horseshoe dowels, include a base connected to the top surface of the main steel girders and U-shaped dowel rings (orbicular reinforcement) connected to the bases at both ends.

[0003] In a bridge equipped with composite girders, when the deck slab is removed and a new composite girder deck slab is constructed on the existing steel main girders, or when the bridge is demolished, the deck slab of the composite girder must be demolished.For example, Patent Document 1 discloses a method for breaking up concrete around a block dowel by substantially simultaneously detonating a first impactor placed within a ring shape formed in a plan view by the base of the block dowel and the dowel ring (dowel body), and a second impactor placed on the opposite side of the base from the first impactor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7467530 Summary of the Invention [Problem to be solved by the invention]

[0005] The method described in Patent Document 1 breaks up the concrete around the block dowels. However, when the distance between adjacent block dowels is long, unbroken concrete may remain in the middle between the two block dowels. In this case, workers must break up the remaining concrete using a hammer drill or similar. This places a heavy burden on workers to break up and remove the concrete (secondary breaking) after breaking up the concrete using an impact generator (primary breaking), and there has been a desire to alleviate this work.

[0006] In view of the above background, an object of the present invention is to provide a method for crushing the deck slab of a composite girder, which is capable of using an impact generator to crush not only the concrete around the block dowels but also the concrete between the block dowels, even when the distance between adjacent block dowels is long. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, one aspect of the present invention is a method for crushing a reinforced concrete deck slab (2) that is integrated with a steel main girder (3) by a plurality of block dowels (4) arranged in a row along the bridge axis direction, the method comprising the steps of: removing a non-girder portion (12) from the deck slab; drilling a plurality of charge holes (13) in the girder portion; and charging each of the plurality of charge holes with an impact generating agent (15); and, after the removing step, the drilling step, and the charging step, and a step of detonating the impact generating agents approximately simultaneously, wherein the block dowel includes a steel base (9) fixed to the upper surface of the steel main girder and a steel dowel ring (10) with both ends fixed to the base so as to combine with the base to form a ring shape in a plan view, and the impact generating agents include a first impact generating agent (15a) arranged inside the ring shape of the block dowel in a plan view and diagonally below the dowel ring when viewed from the bridge width direction, a second impact generating agent (15b) arranged on the opposite side of the first impact generating agent with respect to the base in a plan view, and a third impact generating agent (15c) arranged between the first impact generating agent and the second impact generating agent which are located between the bases of adjacent block dowels in the bridge axis direction.

[0008] According to this embodiment, the presence of the third impact generating agent also causes the concrete between the block dowels to be crushed, thereby reducing the work required after the detonation of the impact generating agent.

[0009] In the above embodiment, the steel main girder (3) includes a web (3a) extending in the bridge axis direction and a pair of flanges (3b, 3c) connected to the top and bottom of the web and extending in the bridge axis direction, and the impact generator (15) may be arranged directly above the web.

[0010] According to this aspect, the impact generator is disposed directly above the web, so that the upper flange of the steel main girder is prevented from being distorted by the impact from the impact generator.

[0011] In the above aspect, the plurality of impact generators may be arranged at approximately equal intervals in the bridge axis direction between the base portions of the adjacent block dowels.

[0012] According to this embodiment, it is easy to determine the position of the drilling location, and the shock wave generated by the detonation of the impact generator is efficiently transmitted to the concrete of the deck, thereby suppressing an increase in the amount of impact generator used.

[0013] In the above aspect, the plurality of impact generating agents may be arranged at substantially equal intervals from one another in the bridge axis direction.

[0014] According to this embodiment, it becomes easier to position the drilling location, and the shock waves generated by the detonation of the impact generator are efficiently transmitted to the concrete of the deck, thereby suppressing an increase in the amount of impact generator used.

[0015] In the above aspect, the distance between the adjacent impact generating agents in the bridge axis direction may be 150 mm or more and 200 mm or less.

[0016] According to this embodiment, excessive use of the impact generating agent and the remaining of uncrushed portions in the concrete 5 are prevented.

[0017] In the above embodiment, the distance from the upper surface of the steel main girder (3) to the lower end of the impact generator is 30 mm or more and 60 mm or less, the distance between the charging center of the first impact generator in a plan view and the inner edge of the midpoint of the dowel ring is 15 mm or more, and the distance between the charging center of the second impact generator in a plan view and the surface of the base facing the second impact generator may be 20 mm or more and 60 mm or less.

[0018] According to this embodiment, excessive use of the impact generating agent and the remaining of uncrushed portions in the concrete 5 are prevented. [Effects of the Invention]

[0019] According to the above aspects, a method for crushing the deck slab of a composite girder can be provided that can use an impact generator to crush not only the concrete around the block dowels but also the concrete between the block dowels, even when the distance between adjacent block dowels is long. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a perspective view showing a bridge having a composite girder to which the method according to the embodiment is applied. [Figure 2] Plan view of a composite girder deck in the middle of applying the method according to the embodiment [Figure 3] A partial cross-sectional side view of a composite girder deck in the middle of applying the method according to the embodiment (viewed from the bridge width direction) [Figure 4] Cross-sectional view taken along line IV-IV in Figure 2 [Figure 5] 1 illustrates a shock wave propagating through concrete in a method according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0022] 1 is a perspective view of the upper part of a bridge 1 to which a method according to an embodiment can be applied, showing a state in which the deck slab 2 has been partially removed. The bridge 1 comprises a steel main girder 3 including an H-shaped steel supported at its lower part (not shown) so as to extend in the bridge axis direction, and a reinforced concrete deck slab 2 supported by the steel main girder 3. The steel main girder 3 comprises a web 3a extending in the bridge axis direction, an upper flange 3b connected to the upper end of the web 3a and extending in the bridge axis direction, and a lower flange 3c connected to the lower end of the web 3a and extending in the bridge axis direction.

[0023] As shown in Figures 2 and 3, block dowels 4 are fixed by welding or the like to the top surface of the upper flange 3b of the steel main girder 3 as a shear stop. By embedding the block dowels 4 in the concrete 5 of the deck slab 2, the deck slab 2 becomes a composite girder deck 2 integrated with the steel main girder 3. The deck slab 2 includes vertical reinforcement 6 extending in the bridge axis direction, horizontal reinforcement 7 extending in the bridge width direction, and concrete 5 in which the block dowels 4, vertical reinforcement 6, and horizontal reinforcement 7 are embedded.

[0024] The block dowel 4 includes a steel base 9 fixed to the upper surface of the upper flange 3b of the steel main girder 3 by welding or the like, and a U-shaped steel dowel ring 10 with both ends fixed to the base 9 by welding or the like. The base 9 extends in the bridge width direction and is shaped like a block or plate. Both ends of the base 9 may be curved so that they face the bridge axis direction. The dowel ring 10 includes a U-shaped steel rod with both ends spaced apart from each other in the bridge width direction, is inclined relative to the up-down direction when viewed from the bridge width direction, and forms a ring shape when combined with the base 9 in a plan view. Multiple block dowels 4 are arranged in a row along the bridge axis direction at the center of the bridge width direction on each steel main girder 3.

[0025] When dismantling the deck 2, first, as shown in Figure 1, the non-girder portions 12 are removed so that girder portions 11, which have a width slightly wider than both ends of the steel main girders 3 in the width direction, remain on the steel main girders 3. The non-girder portions 12 include the portion between two adjacent girder portions 11 and the portion on the steel main girders 3 located at the ends in the bridge width direction that is further outward in the bridge width direction than the girder portions 11.

[0026] In order to remove the non-girder portion 12 from the deck slab 2, while the non-girder portion 12 is supported by temporary members (not shown), workers use a cutting device (not shown) such as a concrete cutter to cut the boundary between the non-girder portion 12 and the girder portion 11 vertically along the bridge axis. Furthermore, if necessary, workers use the cutting device to cut the deck slab 2 vertically along the bridge width direction to divide it into pieces of a weight that can be lifted by a crane (not shown) and a weight and size that can be transported by a transport machine (not shown) such as a truck. Workers then lift the divided non-girder portion 12 with a crane and load it onto the transport machine for transport.

[0027] Next, as shown in Figures 2 to 4, workers drill charge holes 13 based on the positions of the block dowels 4 that they have previously investigated. Then, workers charge impulse generators 15 into the charge holes 13. Each impulse generator 15 is charged at the bottom of the corresponding charge hole 13. If the workers drill the charge holes 13 using a drilling machine (shown) that can drill concrete 5 together with the rebar, they do not need to investigate the positions of the vertical reinforcement 6 and the horizontal reinforcement 7 in advance. If the workers drill the charge holes 13 using a drilling machine (shown) that cannot drill concrete 5 together with the rebar, they will investigate the positions of the vertical reinforcement 6 and the horizontal reinforcement 7 in advance to avoid drilling the charge holes 13 while drilling the charge holes 13. The positions of the block dowels 4, the vertical reinforcement 6, and the horizontal reinforcement 7 can be determined based on the reinforcement diagram of the deck slab 2, etc. If necessary, the workers can determine these positions using a rebar detector (not shown) or the like.

[0028] The impact generators 15 include a first impact generator 15a arranged inside the ring-shaped structure formed by the base 9 and the dowel ring 10 in a plan view, a second impact generator 15b arranged on the opposite side of the first impact generator 15a with respect to the base 9 in a plan view, and a third impact generator 15c arranged between the first impact generator 15a and the second impact generator 15b located between the bases 9 of adjacent block dowels 4 in the bridge axis direction. The first impact generator 15a is arranged diagonally below the dowel ring 10 when viewed from the bridge width direction. In other words, when viewed from the bridge width direction, a line parallel to the vertical direction passing through the first impact generator 15a intersects with the dowel ring 10 above the first impact generator 15a. The charging holes 13 include a first charging hole 13a into which a first impact-generating charge 15a is loaded, a second charging hole 13b into which a second impact-generating charge 15b is loaded, and a third charging hole 13c into which a third impact-generating charge 15c is loaded. One first impact-generating charge 15a and one second impact-generating charge 15b are arranged for one block dowel 4. In the illustrated example, one third impact-generating charge 15c is arranged between adjacent block dowels 4, but the distance L between the block dowels 4 is d In some cases, a plurality of third impact generating agents 15c are arranged between the block dowels 4 adjacent to each other.

[0029] The charging holes 13 are drilled downward from the upper surface of the girder portion 11. The charging holes 13 may be drilled from the side of the girder portion 11 in the bridge width direction, or may be drilled obliquely from the upper surface or side of the girder portion 11, and the drilling directions of each charging hole 13 may be the same or different from each other. When the charging holes 13 are drilled downward from the upper surface of the girder portion 11, the drilling of the charging holes 13 and the charging of the impulse generating agent 15 may be performed before the removal of the non-girder portion 12 (see Figure 1).

[0030] The impulse generators 15 are preferably arranged at approximately equal intervals along the bridge axis between the bases 9 or throughout the entire girder section 11. The term "approximately" in relation to the arrangement of the impulse generators 15 means, for example, that a deviation of up to about 20% is permitted, or that a deviation of approximately the diameter of the longitudinal reinforcement 6 or the transverse reinforcement 7 is permitted when the charge holes 13 are drilled to avoid the longitudinal reinforcement 6 or the transverse reinforcement 7. The impulse generators 15 are preferably arranged directly above the webs 3a, and are preferably spaced approximately the same distance from the top surface of the steel main girder 3. When a block dowel 4 of standard dimensions (width: 180 mm to 250 mm, height: 180 mm to 220 mm) is used, the peak impact pressure Ps when the impulse generators 15 are detonated is preferably 1.5 GPa or more, and the impact pressure duration ΔT when the impulse generators 15 are detonated is preferably 150 μs or less. The types of impact generating agent 15 that satisfy these conditions include a nitromethane-based impact generating agent 15 and an impact generating agent 15 containing a mixture of aluminum powder and metal oxide powder. It is preferable that the types of agents used in the first impact generating agent 15a, the second impact generating agent 15b, and the third impact generating agent 15c are the same.

[0031] When the peak impact pressure Ps and the impact pressure duration ΔT of the impact generating agent 15 are values ​​within the above ranges, it is preferable that the following conditions are satisfied. Spacing of impact generators 15 in the bridge axis direction: 150mm to 200mm The distance L between the charging center of the first impact generating charge 15a in a plan view and the inner edge of the midpoint of the dowel ring 10 in the curved extension direction cr : 15mm or more The distance L between the charging center of the second impulse generating agent 15b and the surface of the base 9 on the side of the second impulse generating agent 15b in a plan view cd :20mm or more and 60mm or less Distance l from the top of the steel main girder 3 to the bottom of the impact generator 15: 30 mm or more and 60 mm or less Depth d of the charging hole 13: 180 mm or more Width W of girder part 11 in the bridge width direction c :500mm or less

[0032] The third impact generating agent 15c has a distance L between the adjacent block dowels 4. d It is preferable to provide the distance L d If the distance between the third impact generators 15c is 600 mm or less, as shown in the figure, one third impact generator 15c is placed between the adjacent block dowels 4, and if the impact generators 15 are placed at equal intervals along the bridge axis direction throughout the entire girder portion 11, the interval between the impact generators 15 is L d The distance between adjacent block dowels 4 is L d If the distance is longer than 600 mm, the number of third impact generating agents 15c between adjacent block dowels 4 is determined so as to satisfy the condition that the interval between the impact generating agents 15 in the bridge axis direction is 150 mm or more and 200 mm or less.

[0033] Next, the worker detonates the first, second, and third impact generating agents 15a, 15b, and 15c, which are aligned so as to be substantially aligned in the bridge axis direction, at approximately the same time. This breaks up the concrete 5 of the deck slab 2. If necessary, the worker uses a tool (not shown) such as a hammer drill to break up the concrete 5 that remains attached to the vertical reinforcement 6, horizontal reinforcement 7, and upper flange 3b after detonation, and removes the broken concrete 5, as well as the vertical reinforcement 6 and horizontal reinforcement 7.

[0034] When installing a new composite girder deck slab using cast-in-place concrete on the existing steel main girder 3 after removing the existing deck slab 2, workers may use the existing block dowels 4 as shear stoppers, or may cut the existing block dowels 4 and install new shear stoppers. Also, when installing a new composite girder deck slab using precast concrete members on the existing steel main girder 3, workers cut the existing block dowels 4 and install the precast concrete members on the steel main girder 3, then install shear stoppers in box-punching holes that penetrate the precast concrete members in the vertical direction, and fill the box-punching holes with concrete (not shown).

[0035] FIG. 5 shows a schematic diagram of the propagation of the maximum pressure portion or the leading edge portion of the shock wave (stress wave) caused by the detonation of the first and second impact generators 15a and 15b. The reason why the concrete 5 around the block dowel 4 in the deck 2 is crushed will be explained with reference to FIG. 5(A). As shown in FIG. 5(A), a compressive stress wave 17 generated by the detonation of the first and second impact generators 15a and 15b is reflected by the upper surface of the upper flange 3b of the steel main girder 3 and converted into a tensile stress wave 18. As shown in FIG. 5(B), the tensile stress wave 18 propagates through the concrete 5 and the block dowel 4. The tensile stress wave 18 propagates upward in a direction substantially parallel to the upper surface of the upper flange 3b while attenuating. In general, waves propagating through metal propagate faster with little attenuation than waves propagating through concrete 5. For this reason, the tensile stress wave 18 propagating within the block dowel 4 propagates faster than the tensile stress wave 18 propagating within the concrete 5 with almost no attenuation, and the propagation point becomes a new wave source, propagating into the interior of the concrete 5.

[0036] The first tensile stress wave 18a generated by the first impact generator 15a is the main source of the tensile stress wave 18 traveling from the top surface of the upper flange 3b toward the dowel ring 10 of the block dowel 4 above it. The second tensile stress wave 18b generated by the second impact generator 15b is the main source of the tensile stress wave 18 traveling within the block dowel 4. At least a portion of the first tensile stress wave 18a, which is reflected by the top surface of the upper flange 3b and propagates within the concrete 5 toward the block dowel 4, propagates within the block dowel 4, and then collides with at least a portion of the second tensile stress wave 18b, which propagates within the concrete 5 toward the top flange 3b of the steel main girder 3. This collision applies a tensile force to the concrete 5, causing it to fracture. Furthermore, the first tensile stress wave 18a and the second tensile stress wave 18b overlap and interfere with each other, forming a complex propagation path for the tensile stress wave 18, thereby fractured the concrete 5 into smaller pieces. Collision, overlap and interference between the first tensile stress wave 18a and the second tensile stress wave 18b occur mainly in the region below the dowel ring 10, so that the concrete 5 in that region can be crushed in a short time.

[0037] Therefore, the condition for arranging the first impact generating agent 15a and the second impact generating agent 15b is to arrange them so that the first tensile stress wave 18a and the second tensile stress wave 18b collide with each other.

[0038] Furthermore, a compressive stress wave (not shown) generated by the detonation of the third impact generator 15c is reflected by the upper surface of the upper flange 3b of the steel main girder 3 and converted into a tensile stress wave (not shown), which then propagates through the concrete 5. The tensile stress wave generated by the third impact generator 15c collides with the first tensile stress wave 18a generated by the first impact generator 15a and the second tensile stress wave 18b generated by the second impact generator 15b, causing the concrete 5 between adjacent block dowels 4 to be crushed. The concrete 5 located between the adjacent block dowels 4 is not subject to the restraining effect of the block dowels 4 that occurs in the concrete 5 around the block dowels 4, and therefore can be crushed by the overlapping of reflected waves from the upper flange 3b.

[0039] As shown in FIGS. 2 to 4, the impact generator 15 is disposed directly above the web 3a, which prevents the upper flange 3b from being distorted by the impact of the detonation of the impact generator 15. By disposing the impact generator 15 near the upper flange 3b, the compression wave generated by the detonation is attenuated less until it is reflected on the surface of the upper flange 3b, and the tension wave generated by the reflection propagates through the block dowel 4 with low attenuation and high strength. By disposing the impact generators 15 at approximately equal intervals between adjacent base portions 9 or throughout the entire girder portion 11, the tension wave generated by the detonation of the impact generator 15 propagates uniformly through the concrete 5, increasing the concrete 5 crushing effect caused by the overlap of the tension waves, and preventing an increase in the amount of impact generator 15 used. By ensuring that the peak impact pressure Ps of the impact generator 15, the impact pressure duration δT, the spacing between the impact generators 15, the distance Lcr between the first impact generator 15a and the dowel ring 10 in a planar view, the distance Lcd between the second impact generator 15b and the base 9 in a planar view, and the distance l from the top surface of the steel main girder 3 to the impact generator 15 meet the above conditions, excessive use of the impact generator 15 and the remaining of uncrushed parts in the concrete 5 are prevented.

[0040] Although the description of the specific embodiment has been completed above, the present invention is not limited to the above embodiment and its modifications, and can be widely modified and implemented. The above embodiment may be applied not only to the replacement of deck slabs of composite girders, but also to bridge demolition work. [Explanation of symbols]

[0041] 2: Floor slab 3: Steel main girder 3a:Web 3b: Upper flange 3c: Lower flange 4: Block Diver 5: Concrete 9: Base 10: Gibel Ring 11: Girder part 12: Non-carriage part 13: Charge hole 13a: 1st charge hole 13b:Second charge hole 13c: 3rd charging hole 15: Impact generator 15a: First impact generator 15b: Secondary impact generator 15c: Third Impact Generator

Claims

1. A method for crushing a reinforced concrete deck slab that is integrated with a steel main girder by a plurality of block dowels arranged in a row along the bridge axis direction, comprising: a step of removing the non-girder portion from the deck slab, which includes a girder portion including a portion located on the steel main girder, and a non-girder portion including a portion between adjacent girder portions and a portion on the steel main girder arranged at an end in the bridge width direction that is further outward in the bridge width direction than the girder portion; Drilling a plurality of charge holes in the beam portion; charging each of the plurality of charging holes with an impact generating agent; substantially simultaneously detonating the impulse generator after the removing, drilling, and charging steps; Equipped with The block dowel includes a steel base fixed to the upper surface of the steel main girder, and a steel dowel ring having both ends fixed to the base so as to be combined with the base to form a ring shape in a plan view, The impact-generating agents include a first impact-generating agent that is arranged inside the ring shape of the block dowel in a plan view and diagonally below the dowel ring when viewed from the bridge width direction, a second impact-generating agent that is arranged on the opposite side of the first impact-generating agent with respect to the base in a plan view, and a third impact-generating agent that is arranged between the first impact-generating agent and the second impact-generating agent that are located between the bases of the block dowels that are adjacent to each other in the bridge axis direction, and are arranged at approximately equal intervals from each other in the bridge axis direction, A method in which a plurality of the impact generating agents are arranged at approximately equal intervals in the bridge axis direction and detonated at approximately the same time, so that the compressive stress waves generated by the detonation are reflected on the top surface of the steel main girder, generating tensile stress waves that propagate uniformly to the concrete in the upper part of the girder, and the tensile stress waves caused by the third impact generating agent and the other impact generating agents located next to the third impact generating agent overlap each other, thereby crushing the portions of the concrete located midway between the adjacent block dowels.

2. The steel main girder includes a web extending in the bridge axis direction and a pair of flanges joined to the top and bottom of the web and extending in the bridge axis direction, The method of claim 1 , wherein the impact generator is disposed directly above the web.

3. The method according to claim 1, wherein the distance between adjacent impact generating agents in the bridge axis direction is 150 mm or more and 200 mm or less.

4. The distance from the upper surface of the steel main girder to the lower end of the impact generator is 30 mm or more and 60 mm or less, The distance between the charging center of the first impact generating charge and the inner edge of the midpoint of the dowel ring in a plan view is 15 mm or more; 4. The method according to claim 3, wherein the distance between the charging center of the second impact generating charge and the surface of the base on the second impact generating charge side in a plan view is 20 mm or more and 60 mm or less.

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