Crushing method for composite girder deck slabs

Abstract

To provide a method capable of efficiently crushing a deck slab of a composite girder equipped with stud dowels. [Solution] A worker places an impulse-generating agent 15 on the girder portion 11. The impulse-generating agent 15 includes a pair of first impulse-generating agents 16 arranged on opposite sides of the stud dowel 4 in the bridge axis direction. The height of the charge center of the first impulse-generating agent 16 from the top surface of the steel main girder 3 is equal to or less than a first predetermined value. The distance between the first impulse-generating agent 16 and the stud dowel in the bridge axis direction is equal to or less than a second predetermined value. The worker detonates the impulse-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 slab that are integrated by stud dowels. [Background technology]

[0002] The deck slab of a composite girder is a reinforced concrete deck slab that is integrated with the steel main girder by embedding shear connectors installed on the top surface of the steel main girder. Block dowels and stud dowels are sometimes used as shear connectors. Block dowels, also known as horseshoe dowels, include a base that is fixed to the top surface of the steel main girder by welding or other means, and U-shaped dowel rings (ring-shaped reinforcement) connected to the base at both ends. Stud dowels include a shaft that is fixed to the top surface of the steel main girder by welding or other means at its lower end and extends upward, and a head that is attached to the upper end of the shaft and has a larger diameter than the shaft.

[0003] In bridges with composite girders, when removing the deck slab and constructing a new composite girder deck slab on the existing steel main girders, or when demolishing the bridge, the composite girder deck slab 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 arranged within a ring shape formed by the base of the block dowel and the dowel ring (dowel body) in a plan view, and a second impactor arranged on the opposite side of the base from the first impactor. Patent Document 2 also discloses a method for demolishing a concrete deck slab using a water jet method. In some cases, the concrete deck slab is demolished manually using a tool such as a hammer drill. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7467530 [Patent Document 2] Japanese Patent Publication No. 64-48972 Summary of the Invention [Problem to be solved by the invention]

[0005] The method described in Patent Document 1 requires that an impact generator be placed inside the ring-shaped structure formed by the base and dowel ring in plan view. For this reason, the method described in Patent Document 1 cannot be applied to deck slabs of composite girders that do not form a ring-shaped structure in plan view, for example, block dowels in which the dowel rings are upright without tilting, or stud dowels.

[0006] The water jet method of crushing concrete has several problems: it is less efficient at removing concrete, which lengthens the process; it uses large amounts of water, which requires significant costs for supplying and disposing of the water; it also requires large-scale countermeasures to prevent water leakage and overflow; and it generates constant noise (noise level of approximately 95 dB at a distance of 3 m).

[0007] Additionally, manual concrete breaking using tools such as hammer drills has the following problems: the removal efficiency is relatively low, which means the process tends to be lengthy; it is difficult to secure workers because it involves hard manual work; the work can cause vibration disorders; and it is accompanied by regular noise (noise levels of 85-95 dB at a distance of 10 m).

[0008] In view of the above background, an object of the present invention is to provide a method for efficiently crushing the deck slab of a composite girder equipped with stud dowels. [Means for solving the problem]

[0009] 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 stud dowels (4) arranged in one or more rows along the bridge axis direction, the method comprising the steps of: removing a girder portion (11) from the deck slab; drilling a plurality of charging holes (13) in the girder portion ... a step of charging each of the plurality of charging holes with an impact generating agent (15); and a step of detonating the impact generating agents approximately simultaneously after the removing step, the drilling step and the charging step, wherein the impact generating agents include a pair of first impact generating agents (16, 22, 32) arranged opposite each other in the bridge axis direction so that the height (he) of the charging center of the impact generating agent from the top surface of the steel main girder is equal to or less than a first predetermined value, and the distance (Lr, La) in the bridge axis direction from the stud dowel belonging to a predetermined row in the row is equal to or less than a second predetermined value. No grooves are provided in the area of ​​the girder upper part that is to be crushed by the impact generators that are detonated almost simultaneously, so that the tensile stress waves generated by the reflection of the compressive stress waves generated by the detonation of the impact generators on the steel main girder are not prevented from overlapping with each other, and the concrete in the upper part of the girder is crushed by the tensile stress waves overlapping with each other.

[0010] According to this aspect, the pair of first impact generating agents can efficiently crush the concrete around the stud dowel.

[0011] 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) joined above and below the web and extending in the bridge axis direction, and the impact generator (15) and the stud dowel (4) belonging to the specified row may be located directly above the web.

[0012] According to this aspect, since the impact generating agent is located directly above the web, distortion of the upper flange due to the detonation of the impact generating agent is suppressed.

[0013] In the above embodiment, the height (h e) may be equal to or greater than 30 mm and equal to or less than 100 mm, and the second predetermined value may be 100 mm.

[0014] According to this aspect, concrete can be crushed more efficiently.

[0015] In the above aspect, the distance between adjacent stud dowels (4) in the specified row may be 200 mm or less, and the first impact-generating agent (16) arranged between adjacent stud dowels in the specified row, as viewed from the bridge width direction, may also serve as the first impact-generating agent for both of the adjacent stud dowels.

[0016] According to this aspect, when the interval between the stud dowels is short, concrete can be efficiently crushed and the amount of impact generating agent used can be reduced.

[0017] In the above aspect, the distance between adjacent stud dowels (4) in the specified row may be 200 mm or more and 400 mm or less, and two first impact-generating agents (22) may be arranged between adjacent stud dowels in the specified row when viewed from the bridge width direction, and each of the first impact-generating agents may satisfy the conditions of the first impact-generating agent only for one corresponding stud dowel.

[0018] According to this aspect, when the stud dowel spacing is medium, concrete can be efficiently crushed and the amount of impact generating agent used can be reduced.

[0019] In the above aspect, the distance between adjacent stud dowels (4) in the specified row may be 400 mm or more, and when viewed from the bridge width direction, two of the first impact-generating agents (32) may be arranged between adjacent stud dowels in the specified row, and the impact-generating agents may further include one or more second impact-generating agents (33) arranged between the two first impact-generating agents.

[0020] According to this aspect, when the intervals between the stud dowels are long, not only the concrete around the stud dowels but also the concrete between the stud dowels can be efficiently crushed.

[0021] In the above aspect, the impact generating agents (15) arranged between the adjacent stud dowels (4) in the predetermined row may be arranged at approximately equal intervals when viewed from the bridge width direction.

[0022] According to this embodiment, the stress wave caused by the detonation spreads uniformly, and the concrete is efficiently crushed. [Effects of the Invention]

[0023] According to the above aspect, a method can be provided that can efficiently crush the deck slab of a composite girder equipped with stud dowels. [Brief explanation of the drawings]

[0024] [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 to which the method according to the first embodiment is applied [Figure 3] Partial cross-sectional side view of a composite girder deck to which the method according to the first embodiment is applied (viewed from the bridge width direction) [Figure 4] Cross-sectional view taken along line IV-IV in Figure 2 [Figure 5] FIG. 1 shows a shock wave propagating through concrete in the method according to the first embodiment. [Figure 6] Plan view of a composite girder deck in the middle of applying the method according to the second embodiment [Figure 7] A partial cross-sectional side view of a composite girder deck in the middle of applying the method according to the second embodiment (viewed from the bridge width direction) [Figure 8] Plan view of a composite girder deck to which the method according to the third embodiment is applied [Figure 9]Partial cross-sectional side view of the deck of the composite girder to which the method according to the third embodiment is applied (viewed from the bridge width direction) [Figure 10] Plan view of a composite girder deck to which the method according to the fourth embodiment is applied [Figure 11] Partial cross-sectional side view of a composite girder deck to which the method according to the fourth embodiment is applied [Figure 12] Cross-sectional view along line XII-XII in Figure 10 [Figure 13] Plan view of a composite girder deck to which the method according to the fifth embodiment is applied [Figure 14] Partial cross-sectional side view of a composite girder deck to which the method according to the fifth embodiment is applied [Figure 15] Plan view of a composite girder deck to which the method according to the sixth embodiment is applied [Figure 16] A partial cross-sectional side view of a composite girder deck to which the method according to the sixth embodiment is applied [Figure 17] Figures showing the specimen in the example (A: plan view, B: partial cross-sectional side view, C: cross-sectional view along line CC in Figure A) [Figure 18] Photograph showing the specimen after the impulse generator was detonated [Figure 19] A photograph showing the condition of the test specimen after workers removed concrete debris from it by hand without using tools. DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0026] 1 is a perspective view of the upper part of a bridge 1 to which the method according to the first embodiment is 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 the deck slab 2 made of reinforced concrete 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.

[0027] As shown in Figures 2 and 3, stud 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 stud 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 stud dowels 4, vertical reinforcement 6, and horizontal reinforcement 7 are embedded.

[0028] The stud dowels 4 include a steel shaft 8 fixed to the upper surface of the upper flange 3b of the steel main girder 3 by welding or the like, and a head 9 provided at the upper end of the shaft 8 and having a larger diameter than the shaft 8. The stud dowels 4 are arranged in rows along the bridge axis direction. In the example shown, the stud dowels 4 are arranged in three rows, with the central row being located directly above the web 3a.

[0029] The overall flow of the method for crushing the deck slab 2 will now be explained. When dismantling the deck slab 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 outward in the bridge width direction from the girder portions 11 on the steel main girders 3.

[0030] 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.

[0031] Next, as shown in Figures 2 to 4, workers drill charge holes 13 based on the positions of the stud dowels 4 that were previously investigated. Then, the workers load impulse generators 15 into the charge holes 13. Each impulse generator 15 is loaded 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 stud 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 will determine these positions using a rebar detector (not shown) or the like.

[0032] Next, the worker detonates the multiple impact generators 15, which are aligned in the bridge axis direction, approximately simultaneously. This breaks up the concrete 5 of the deck slab 2. If necessary, the worker uses a tool such as a hammer drill (not shown) 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.

[0033] 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 stud dowels 4 as shear stoppers, or may cut the existing stud 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 stud 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).

[0034] The arrangement and installation method of the impulse generators 15 will be described. In the first embodiment, the impulse generators 15 are arranged at approximately equal intervals in the bridge axis direction, with one being arranged at the center of two adjacent stud dowels 4 in the bridge axis direction. Therefore, the average installation interval of the impulse generators 15 in the bridge axis direction matches the average installation interval of the stud dowels 4. The impulse generators 15 are also arranged directly above the web 3a, which is approximately the center of the girder portion 11 in the bridge width direction. The term "approximately" in relation to the arrangement of the impulse generators 15 means, for example, that a deviation of up to about 20% from the strict distance or interval is permitted, or that a deviation of about the diameter of the vertical reinforcing bars 6 or horizontal reinforcing bars 7 is permitted when drilling the charge holes 13 while avoiding the vertical reinforcing bars 6 and horizontal reinforcing bars 7.

[0035] 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).

[0036] In the first embodiment, the installation interval L of the stud dowels 4 in the bridge axis direction d is 200 mm or less, and the width W of the upper flange 3b of the steel main girder 3 f is 400 mm or less, and the width W of the girder part 11 s is less than 500 mm.

[0037] The peak impact pressure Ps when the impact generator 15 is detonated is preferably 1.5 GPa or more, and the impact pressure duration ΔT when the impact generator 15 is detonated is preferably 150 μs or less. It is more preferable that the impact pressure of the impact generator 15 increases to 1.5 to 2.0 GPa within about 130 μs after detonation. Types of impact generators 15 that satisfy these conditions include nitromethane-based impact generators 15 and impact generators 15 containing a mixture of aluminum powder and metal oxide powder.

[0038] When the peak impact pressure Ps and the impact pressure duration ΔT of the impact generating agents 15 are values ​​within the above ranges, it is preferable that the following conditions be satisfied. In the first embodiment, all the impact generating agents 15 are first impact generating agents 16 for pincer simultaneous detonation, which will be described later. Distance L between the center of the first impact generator 16 and the center of the stud dowel in the bridge axis direction r :100mm or less Height h from the top surface of the steel main girder 3 to the center of the impact generating agent 15 e : 30 mm or more and 100 mm or less, preferably 30 mm or more and 70 mm or less

[0039] 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 impact generator 15. The mechanism by which the concrete 5 around the stud dowel 4 in the deck slab 2 is crushed will be described with reference to FIG. 5. As shown in FIG. 5, the compressive stress wave (shown by the dashed line in the figure) caused by the detonation of the impact generator 15 is reflected by the upper surface of the upper flange 3b of the steel main girder 3 and converted into a tensile stress wave (shown by the two-dot chain line in the figure). The tensile stress wave propagates inside the concrete 5 and inside the stud dowel 4. The tensile stress wave propagating inside the concrete 5 propagates upwards approximately parallel to the upper surface of the upper flange 3b while attenuating. In general, waves propagating inside metal propagate faster with almost no attenuation than waves propagating inside the concrete 5 (the propagation speed in metal C s > Propagation velocity C in concrete 5 c ) For this reason, the tensile stress waves propagating within the stud dowels 4 propagate faster than the tensile stress waves propagating within the concrete 5 with almost no attenuation, and the propagation points become new wave sources, propagating further into the concrete 5. Therefore, on the surfaces connecting the stud dowels 4, the tensile stress waves propagating within the concrete 5 from the upper flanges 3b and the tensile stress waves propagating from the stud dowels 4 overlap, forming a fracture surface, causing the concrete 5 to fracture.

[0040] The effects of the first embodiment will be described. When the impact generator 15 detonates near the upper flange 3b, a strong tensile stress wave is generated (deep charge initiation). When the first impact generator 16 detonates near the stud dowel 4, a low-attenuation, strong tensile stress wave propagates within the stud dowel 4 (dowel proximity initiation). When viewed from the bridge width direction, a pair of corresponding first impact generators 16 sandwich each stud dowel 4 at approximately equal distances in the bridge axis direction and detonate simultaneously, amplifying the strength of the tensile stress wave propagating within the dowel (pincer simultaneous initiation). In this way, the combination of deep charge initiation, dowel proximity initiation, and pincer simultaneous initiation efficiently fractures the concrete 5 around the stud dowel 4. Furthermore, the concrete 5 between adjacent stud dowels 4 in the bridge axis direction is also fractured by the initiation of the first impact generator 16 because the spacing between the stud dowels 4 is narrower than in the third embodiment described later.

[0041] One impact generator 15 placed between two adjacent stud dowels 4 in the bridge axis direction functions as an impact generator 15 for simultaneous pincer detonation of both stud dowels 4, thereby reducing the amount of impact generator 15 used.

[0042] As shown in FIGS. 2 to 4, the impact generating agent 15 is disposed directly above the web 3a, so that the upper flange 3b is prevented from being distorted by the impact caused by the detonation of the impact generating agent 15.

[0043] A second embodiment of the present invention will be described with reference to Figures 6 and 7. In the description, the same components as those in the first embodiment will be denoted by the same reference numerals and will not be described again. In the second embodiment, the installation interval L of the stud dowels 4 in the bridge axis direction is d The second embodiment differs from the first embodiment in the arrangement of the impact generating agent 15, but has the same other configurations as the first embodiment.

[0044] In the girder portion 21 of the second embodiment, the installation interval L of the stud dowel 4 in the bridge axis direction dThe distance between the first impulse generators 15 is 200 mm or more and 400 mm or less. All the impulse generators 15 are first impulse generators 22 for pincer simultaneous detonation. A pair of first impulse generators 22 is provided for each stud dowel 4 in the center row in the bridge width direction so as to sandwich it in the bridge axis direction (in Figure 7, of the pair of first impulse generators 22 sandwiching the n-th stud dowel 4 from the left, the one located on the left is called the l n and the one on the right is written as r n The first impact generator 16 (see FIG. 2) of the first embodiment exerts the pincer simultaneous detonation function on both of the two stud dowels 4 that sandwich the first impact generator 22 in the bridge axis direction, but the first impact generator 22 of the second embodiment exerts the pincer simultaneous detonation function only on the stud dowel 4 that is closest to the two stud dowels 4 that sandwich the first impact generator 22 in the bridge axis direction. Therefore, two first impact generators 22 are placed between two stud dowels 4 that are adjacent to each other in the bridge axis direction. The impact generator 15 is placed directly above the web 3a, which is approximately the center of the girder portion 11 in the bridge width direction.

[0045] Width W of the upper flange 3b of the steel main girder 3 f , width W of girder part 11 s The peak impact pressure Ps and the impact pressure duration ΔT of the impact generating agent 15 are the same as those in the first embodiment. When the peak impact pressure Ps and the impact pressure duration ΔT of the impact generating agent 15 are within the above-mentioned ranges, it is preferable that the following conditions are satisfied. Distance L between the center of the first impact generating charge 22 and the center of the stud dowel in the bridge axis direction a : 50mm or more and 100mm or less Height h from the top surface of the steel main girder 3 to the center of the impact generating agent 15 e : 30 mm or more and 100 mm or less, preferably 30 mm or more and 70 mm or less The distance L between the two first impact generators 16 arranged between two adjacent stud dowels 4 in the bridge axis direction b :100mm or more and 200mm or less

[0046] Distance L between the center of the first impact generating charge 22 and the center of the stud dowel 4 in the bridge axis directiona and the distance L between the two first impact generators 16 arranged between two adjacent stud dowels 4 in the bridge axis direction. b The sum of these is the spacing L between stud dowels 4. d This becomes:

[0047] The processes of removing the non-raising portion 12 (see Figure 1), drilling the charging hole 13, charging the impact generating agent 15, detonating the impact generating agent 15, and removing the debris are performed in the same manner as in the first embodiment, except for the positions of the charging hole 13 and the impact generating agent 15.

[0048] In the second embodiment, the concrete 5 between two first impact-generating agents 22 located between adjacent stud dowels 4 in the bridge axis direction is crushed by the compressive stress waves generated by the detonation of these two first impact-generating agents 22 being reflected by the upper flange 3b and becoming tensile stress waves that overlap each other. In other respects, the second embodiment has the same effects as the first embodiment.

[0049] A third embodiment of the present invention will be described with reference to Figures 8 and 9. In the description, the same components as those in the first embodiment will be denoted by the same reference numerals and will not be described again. In the third embodiment, the installation interval L of the stud dowels 4 in the bridge axis direction is d The second embodiment differs from the first embodiment in the arrangement of the impact generating agent 15, but has the same other configurations as the first embodiment.

[0050] In the girder portion 31 of the third embodiment, the installation interval L of the stud dowel 4 in the bridge axis direction dis 400 mm or more. The impact generator 15 includes a first impact generator 32 for pincer simultaneous detonation and a second impact generator 33 arranged in the bridge axis direction at a distance from the stud dowel 4 with respect to the first impact generator 32. A pair of first impact generators 32 is provided for each stud dowel 4 in the center row in the bridge width direction so as to sandwich the stud dowel 4 in the bridge width direction. As in the second embodiment, the first impact generator 32 exerts the pincer simultaneous detonation function only on the stud dowel 4 closest to it, of the two stud dowels 4 that sandwich the first impact generator 32 in the bridge axis direction. Therefore, two first impact generators 32 are arranged between two stud dowels 4 adjacent to each other in the bridge axis direction. One or more (two in the illustrated example) second impact generators 33 are arranged between the two first impact generators 32 arranged between two stud dowels 4 adjacent to each other in the bridge axis direction. The distance L between the impact generators 15 arranged between two adjacent stud dowels 4 in the bridge axis direction c In the illustrated example, the distance L between the two first impact generating elements 32 between two adjacent stud dowels 4 in the bridge axis direction is m The second impact generators 33 are arranged so as to divide the area into three equal parts. The impact generator 15 is arranged directly above the web 3a, which is approximately the center of the girder portion 11 in the bridge width direction.

[0051] Width W of the upper flange 3b of the steel main girder 3 f , width W of girder part 11 s The peak impact pressure Ps and the impact pressure duration ΔT of the impact generating agent 15 are the same as those in the first embodiment. When the peak impact pressure Ps and the impact pressure duration ΔT of the impact generating agent 15 are within the above-mentioned ranges, it is preferable that the following conditions are satisfied. Distance L between the center of the first impact generating charge 22 and the center of the stud dowel in the bridge axis direction a : 50mm or more and 100mm or less Height h from the top surface of the steel main girder 3 to the center of the impact generating agent 15 e : 30 mm or more and 100 mm or less, preferably 30 mm or more and 70 mm or less The distance L between the impact generators 15 arranged between two adjacent stud dowels 4 in the bridge axis direction c:100mm or more and 200mm or less

[0052] Distance L between the center of the first impact generating charge 22 and the center of the stud dowel 4 in the bridge axis direction a and the interval L between the two first impact generators 32 arranged between two adjacent stud dowels 4 in the bridge axis direction. m The sum of these is the spacing L between stud dowels 4. d This becomes:

[0053] The processes of removing the non-raising portion 12 (see Figure 1), drilling the charging hole 13, charging the impact generating agent 15, detonating the impact generating agent 15, and removing the debris are performed in the same manner as in the first embodiment, except for the positions of the charging hole 13 and the impact generating agent 15.

[0054] In the third embodiment, the concrete 5 between two first impact generators 22 located between adjacent stud dowels 4 in the bridge axis direction is crushed by compressive stress waves generated by the detonation of adjacent first impact generators 32 and second impact generators 33, or two adjacent second impact generators 33, which are reflected by the upper flange 3b and become tensile stress waves that overlap each other. Furthermore, because the impact generators 15 located between adjacent stud dowels 4 in the bridge axis direction are arranged at approximately equal intervals, the stress waves caused by the detonation spread uniformly, and the concrete 5 is efficiently crushed. In other respects, the third embodiment has the same effects as the first embodiment.

[0055] A fourth embodiment of the present invention will be described with reference to Figures 10 to 12. In the description, components common to the first embodiment will be denoted by the same reference numerals and will not be described again. The fourth embodiment differs from the first to third embodiments in that a block dowel 40 is used as a shear stopper.

[0056] The block dowels 40 are located approximately in the center of the girder portion 41 in the bridge width direction, and are lined up along the bridge axis direction. The block dowels 40 include a steel base 44 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 45 with both ends fixed to the base 44 by welding or the like. The base 44 extends in the bridge width direction and is shaped like a block or plate. Both ends of the base 44 may be curved so as to face the bridge axis direction. The dowel ring 45 includes a U-shaped steel rod with both ends spaced apart from each other in the bridge width direction, and stands upright relative to the upper surface of the upper flange 3b. The installation interval L of the block dowels 40 in the bridge axis direction d is less than 500mm.

[0057] The impact-generating agent 15 includes one first impact-generating agent 42 arranged between two block dowels 40 adjacent to each other in the bridge axis direction, close to the block dowel 40, and one second impact-generating agent 43 located farther away from the block dowel 40 than the first impact-generating agent 42. The first impact-generating agents 42 and the second impact-generating agents 43 are arranged alternately along the bridge axis direction. The interval L between the impact-generating agents 15 in the bridge axis direction is c are approximately equal to each other, and the spacing L of the block dowel 40 d It is 1 / 2 of that.

[0058] Width W of the upper flange 3b of the steel main girder 3 f , width W of girder part 11 s The peak impact pressure Ps of the impact generator 15 and the impact pressure duration δT of the impact generator 15 are the same as in the first embodiment. In addition, it is preferable that the protruding width ΔW of the girder portion 11 relative to the upper flange 3b in the bridge width direction is equal on the left and right. When the peak impact pressure Ps and impact pressure duration δT of the impact generator 15 are values ​​within the above-mentioned ranges, it is preferable that the following conditions are satisfied. The distance L between the charging center of the first impact generating agent 42 and the surface of the base 44 on the side of the first impact generating agent 42 in a plan view a :50mm or less Height h from the top surface of the steel main girder 3 to the bottom end of the impact generator 15 e :60mm or less Distance L between impact generators 15 in the bridge axis direction c :250mm or less

[0059] The processes of removing the non-raising portion 12 (see Figure 1), drilling the charging hole 13, charging the impact generating agent 15, detonating the impact generating agent 15, and removing the debris are performed in the same manner as in the first embodiment, except for the positions of the charging hole 13 and the impact generating agent 15.

[0060] When the first impactor 42 is detonated near the block dowel 40, a strong tensile stress wave with low attenuation propagates within the block dowel 40 (dowel proximity detonation). When the impactor 15 is detonated near the upper flange 3b, a strong tensile stress wave is generated (deep charge detonation). When the impactor 15 is arranged at roughly equal intervals, a tensile stress wave propagates uniformly throughout the girder portion 11, and the concrete 5 is crushed by the superposition of the tensile stress waves (equal-interval charge). When the dowel proximity detonation occurs, a strong tensile stress wave is generated near the block dowel 40. As a result, the propagation speed C of the stress wave between the concrete 5 and the metal block dowel 40 increases. c ,C s Utilizing the difference in the surface tension (see Figure 5), a Mach effect occurs in the concrete 5 around the block dowel 40, forming a fracture surface along the surface of the dowel ring 45, nullifying the integration of the block dowel 40 and the concrete 5, and fragmenting the concrete 5 near the block dowel 40. The deep charge detonation and the equally spaced charge generate strong, uniform tensile stress waves. This causes the concrete 5 around the block dowel 40 to shred into small fragments (spalling), and nullifies the adhesive force between the concrete 5 and the surface of the upper flange 3b (interface wave propagation). Furthermore, because the impact generator 15 is positioned directly above the web 3a, distortion of the upper flange 3b due to the impact of the detonation of the impact generator 15 is suppressed.

[0061] A fifth embodiment of the present invention will be described with reference to Figures 13 and 14. In the description, the same components as those in the fourth embodiment will be denoted by the same reference numerals and will not be described again. In the fifth embodiment, the installation interval L of the block dowels 40 is dAlso, the arrangement of the impact generating agent 15 is different from that of the fourth embodiment.

[0062] Installation interval L of block dowels 40 in the bridge axis direction in the girder part 51 d is longer than 500 mm. Block dowel 40 is installed at intervals L d Other than that, it is configured in the same way as the block dowel 40 of the fourth embodiment.

[0063] The impact generator 15 includes one first impact generator 52 arranged close to the block dowel 40 between two block dowels 40 adjacent to each other in the bridge axis direction, and a plurality of (N, two in the illustrated example) second impact generators 53 that are spaced further from the block dowel 40 than the first impact generator 42. The one first impact generator 52 and the two second impact generators 53 are arranged in a similar pattern between each pair of adjacent block dowels. The spacing L of the impact generators 15 in the bridge axis direction is c are approximately equal to each other, and the spacing L of the block dowel 40 d (In the illustrated example, N=3, which is 1 / 3).

[0064] Width W of the upper flange 3b of the steel main girder 3 f , width W of girder part 11 s The peak impact pressure Ps and the impact pressure duration ΔT of the impact generating agent 15 are the same as those in the first embodiment. When the peak impact pressure Ps and the impact pressure duration ΔT of the impact generating agent 15 are within the above-mentioned ranges, it is preferable that the following conditions are satisfied. The distance L between the charging center of the first impact generating agent 42 and the surface of the base 44 on the side of the first impact generating agent 42 in a plan view a :50mm or less Height h from the top surface of the steel main girder 3 to the bottom end of the impact generator 15 e :60mm or less Distance L between impact generators 15 in the bridge axis direction c :150mm or more and 250mm or less

[0065] The processes of removing the non-raising portion 12 (see Figure 1), drilling the charging hole 13, charging the impact generating agent 15, detonating the impact generating agent 15, and removing the debris are performed in the same manner as in the fourth embodiment, except for the positions of the charging hole 13 and the impact generating agent 15.

[0066] In the fifth embodiment, the concrete 5 is crushed by the same mechanism as in the fourth embodiment. In addition, since the impact generator 15 is disposed directly above the web 3a, distortion of the upper flange 3b due to the impact caused by the detonation of the impact generator 15 is suppressed.

[0067] A sixth embodiment of the present invention will be described with reference to Figures 15 and 16. In the description, components common to the fifth embodiment will be denoted by the same reference numerals and will not be described again. The sixth embodiment differs from the fifth embodiment in the arrangement of the impact generating agent 15.

[0068] Installation interval L of block dowels 40 in the bridge axis direction in the girder part 61 d is longer than 500 mm. The block dowel 40 is configured in the same manner as the block dowel 40 of the fifth embodiment.

[0069] The impact generators 15 include a pair of first impact generators 62 arranged near each block dowel 40 on opposite sides of each block dowel 40 in the bridge axis direction, and one or more (three in the figure) second impact generators 63 arranged between the two first impact generators 62 between two block dowels 40 adjacent to each other in the bridge axis direction. c The distances L from the center of the corresponding block dowel 40 of the pair of first impact generating agents 62 in the bridge axis direction are approximately equal to each other. a are approximately equal to each other, and the distance L between the impact generators 15 in the bridge axis direction is c It is 1 / 2 of that.

[0070] Width W of the upper flange 3b of the steel main girder 3 f , width W of girder part 11 sThe peak impact pressure Ps and the impact pressure duration ΔT of the impact generating agent 15 are the same as those in the first embodiment. When the peak impact pressure Ps and the impact pressure duration ΔT of the impact generating agent 15 are within the above-mentioned ranges, it is preferable that the following conditions are satisfied. Distance L between adjacent impact generators 15 in the bridge axis direction c (2L a ):150mm or more and 200mm or less Height h from the top surface of the steel main girder 3 to the bottom end of the impact generator 15 e :60mm or less

[0071] The processes of removing the non-raising portion 12 (see Figure 1), drilling the charging hole 13, charging the impact generating agent 15, detonating the impact generating agent 15, and removing the debris are performed in the same manner as in the fourth embodiment, except for the positions of the charging hole 13 and the impact generating agent 15.

[0072] In the sixth embodiment, in addition to the concrete 5 being crushed by the same mechanism as in the fourth embodiment, the concrete 5 around the block dowel 40 is crushed by the pincer simultaneous detonation of a pair of first impact generating agents 62. In addition, since the impact generating agent 15 is disposed directly above the web 3a, distortion of the upper flange 3b due to the impact caused by the detonation of the impact generating agent 15 is suppressed. [Example]

[0073] As shown in Figure 17, a test specimen corresponding to the configuration of the girder portion 11 of the first embodiment was created. In the test specimen, the spacing between the stud dowels 4 in the bridge axis direction was 100 mm, the spacing between the impact generating agents 15 (first impact generating agents 16) in the bridge axis direction was 100 mm, and the height from the top surface of the upper flange 3b to the charge center of the impact generating agent 15 was 65.5 mm. Each of the impact generating agents 15 was 5 mL of nitromethane. The charge holes 13 were drilled from the side of the test specimen in the bridge width direction.

[0074] Fig. 18 is a photograph of the test specimen immediately after the detonation of the impact generator 15, and Fig. 19 is a photograph of the state in which a worker has manually removed pieces of concrete 5 from the test specimen after detonation without using any tools. As shown in Figs. 17 to 19, the concrete 5 of the test specimen was crushed by the detonation of the impact generator 15.

[0075] Although the description of specific embodiments has been completed above, the present invention is not limited to the above-described embodiments and modifications, and can be implemented in a wide variety of modifications. The above-described embodiments may be applied not only to the replacement of composite girder deck slabs, but also to bridge demolition work. In the first to third embodiments, the impact generators and stud dowels may not be arranged in the same straight line in the bridge axis direction, but may be offset in the bridge width direction. [Explanation of symbols]

[0076] 2: Floor slab 3: Steel main girder 3a:Web 3b: Upper flange 4: Stud dowel 5: Concrete 11,21,31,41,51,61: Upper part 12: Non-carriage part 13: Charge hole 15: Impact generator 16, 22, 32, 42, 52, 62: First impact generator 33, 43, 44, 53, 63: Secondary 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 stud dowels arranged in one or more rows 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 impact generators include a pair of first impact generators arranged opposite each other in the bridge axis direction so that the height of the charge center of the impact generator from the top surface of the steel main girder is equal to or less than a first predetermined value, and the distance in the bridge axis direction from the stud dowel belonging to a predetermined row in the row is equal to or less than a second predetermined value, The height of the charge center of the impact generating agent is 30 mm or more and 100 mm or less, the second predetermined value is 100 mm, A method in which no grooves are provided in the area of ​​the girder upper part that is to be crushed by the impact generating agents that are detonated almost simultaneously, thereby not preventing the tensile stress waves generated by the reflection of the compressive stress waves generated by the detonation of the impact generating agents on the steel main girder from overlapping with each other, and the concrete in the upper part of the girder is crushed by the tensile stress waves overlapping with each other.

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 and the stud dowels belonging to the predetermined row are located directly above the web.

3. The distance between adjacent stud dowels in the predetermined row is 200 mm or less, 2. The method according to claim 1, wherein the first impact-generating agent arranged between adjacent stud dowels in the predetermined row, when viewed from the bridge width direction, serves as the first impact-generating agent for both of the adjacent stud dowels.

4. The distance between adjacent stud dowels in the predetermined row is 200 mm or more and 400 mm or less, 2. The method according to claim 1, wherein, when viewed from the bridge width direction, two of the first impact-generating agents are arranged between adjacent stud dowels in the predetermined row, and each of the first impact-generating agents satisfies the conditions of the first impact-generating agent only for one corresponding stud dowel.

5. The distance between adjacent stud dowels in the predetermined row is 400 mm or more, 2. The method according to claim 1, wherein, when viewed from the bridge width direction, two of the first impact-generating agents are arranged between adjacent stud dowels in the predetermined row, and the impact-generating agents further include one or more second impact-generating agents arranged between the two first impact-generating agents.

6. The method according to claim 1, wherein the impact generators arranged between the adjacent stud dowels in the predetermined row are arranged at approximately equal intervals from each other when viewed in the bridge width direction.

Images