Bridge combined reinforcement method based on ecc-dispersed prestress

Abstract

The application discloses a kind of based on ECC-dispersed prestressed bridge combination reinforcing method, including the multiple prestressed steel strands of the web of bridge one side or both sides being arranged, multiple shear pins and the steel mesh being fixedly connected with shear pin, the ECC thick layer of prestressed steel strand, steel mesh and shear pin is covered by spraying mode;The reinforcing method specifically includes design reinforcing site, drilling, chiseling processing, hole cleaning, implantation shear pin, prestressed steel strand and tension anchoring are laid out, fixed steel mesh, watering wet and preparation ECC material and spray etc. steps.The application is based on dispersed prestressed steel strand and bridge web is reinforced by spraying ECC concrete, improves the bending bearing capacity and shear bearing capacity of bridge structure, solves the problem that concrete structure is prone to local stress concentration in traditional prestressed reinforcement, improves service performance and service life, reduces operation and maintenance cost.

Description

Technical Field

[0001] This invention relates to the field of bridge reinforcement technology, and in particular to a bridge composite reinforcement method based on ECC-distributed prestressing. Background Technology

[0002] Small and medium span beam bridges are the main type of highway bridges, accounting for about 90%, especially hollow slab beam bridges, box girder bridges and composite beam bridges. The main defects of these bridges include longitudinal cracks in the bottom slab, transverse cracks in the mid-span, vertical cracks and diagonal cracks in the web. Most of these defects are caused by insufficient bending and shear resistance, which seriously weakens the operational safety of the bridge.

[0003] To improve the load-bearing capacity and service life of bridge structures, it is necessary to reinforce existing bridges with defects. Currently, the main reinforcement methods for reinforced concrete bridges include external prestressing, bonding steel or carbon fiber plates, increasing the cross-section, and modifying the structural system. External prestressing has the advantage of balancing part of the dead load, effectively controlling the overall deflection of the structure, and limiting the generation and development of cracks. However, it can easily cause localized stress concentrations, leading to secondary damage. Bonding steel or carbon fiber plates does not increase the cross-sectional dimensions or weight of the reinforced structure and is simple and quick to construct. However, it has limited impact on improving the structural load-bearing capacity, and over long-term use, it can easily lead to delamination from the bridge structure, affecting the reinforcement effect. Conventional methods of increasing the cross-section often result in poor bonding between new and old concrete, and a significant increase in the bridge's self-weight. Therefore, the above-mentioned commonly used reinforcement techniques for reinforced concrete bridges all have certain shortcomings and are mostly limited to solving single defects in the bridge structure. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a bridge combined reinforcement method based on ECC-distributed prestressing. By designing a bridge bending and shear combined reinforcement method with reasonable structure, good comprehensive reinforcement effect and convenient construction, the bearing capacity of the reinforced bridge can be improved.

[0005] Technical Solution: The present invention discloses a bridge reinforcement method based on ECC-distributed prestressing, comprising multiple prestressed steel strands arranged longitudinally and at intervals along the bridge web, multiple shear pins uniformly anchored along the bridge web interface, with steel mesh fixedly connected to the shear pins, and an ECC thickening layer covering the prestressed steel strands, steel mesh, and shear pins by spraying; the reinforcement method specifically includes the following steps:

[0006] Step S1: Use a radar detector or rebar locator to mark the location of the original beam rebar and steel strands in the reinforcement area, avoid the original beam rebar and steel strand locations, and design reinforcement site drawings;

[0007] Step S2: Determine the location of prestressed steel strands, anchoring devices and rebar holes on the web interface of the bridge according to the design drawings, and then drill holes according to the process requirements.

[0008] Step S3: Roughen the concrete surface in the reinforcement area by manual chiseling;

[0009] Step S4: Use a brush to repeatedly pull back and forth into the bottom of the anchor hole to remove dust and debris; then use compressed air to blow out the floating dust in the anchor hole, and then wash the concrete surface with pressurized water.

[0010] Step S5: Use absorbent cotton soaked in alcohol or acetone to clean the inner wall of the rebar hole, then inject rebar adhesive into the rebar hole, filling 2 / 3 of the hole, and insert shear pins into the corresponding rebar hole in the web.

[0011] Step S6: Install the anchoring device according to the design location, arrange the prestressed steel strands longitudinally at intervals on the surface of the bridge web, and tension the prestressed steel strands one by one in stages through the front clamp jack in the anchoring device.

[0012] Step S7: Arrange a reinforcing mesh on the surface of the bridge web outside the prestressed steel strands, and fix the reinforcing mesh to the shear pins.

[0013] Step S8: Moisten the surface of the bridge's web with water and keep the concrete surface saturated and dry.

[0014] Step S9: Prepare ECC material and apply a 10-15cm thick layer of ECC concrete to the surface of the bridge web using a wet spraying method to form an ECC thickening layer.

[0015] Preferably, in step S3, the roughening process involves using a perforated hammer to roughen the surface, followed by using an electric hammer or hand hammer to chisel out pits on the ground concrete surface; wherein the pits are formed to a depth of 3 mm, and the density of the evenly distributed pits is 600-800 points / m². 2 .

[0016] Preferably, in step S5, the insertion depth of the shear pin is greater than 5 cm, and the distance from the shear pin extending out of the rebar hole is 5 mm; the distance between the shear pin and the edge of the web should not be less than 100 mm.

[0017] Preferably, in step S6, the prestressed steel strand is one of galvanized steel strand, epoxy resin coated steel strand, or indented steel strand, and the bundle type of the prestressed steel strand is straight or broken.

[0018] Preferably, in step S6, there can be one or more anchoring devices; multiple prestressed steel strands can share one anchoring device, or a single prestressed steel strand can correspond to one anchoring device.

[0019] Preferably, in step S7, the steel mesh is arranged longitudinally along the bridge and is fixedly connected to the protruding end of the shear pin by welding or binding to form an integral structure.

[0020] Preferably, the mesh size of the steel mesh in step S7 is 10cm × 15cm.

[0021] Preferably, the ECC material in step S9 is composed of the following raw materials in parts by weight:

[0022] 300-400 parts of PO 52.5 silicate cement;

[0023] 50-80 parts fly ash;

[0024] 500-600 parts of fine aggregate;

[0025] Water-reducing agent 0.5-1 part;

[0026] 40-60 parts of expanding agent;

[0027] Thixotropic lubricant 1-2 parts;

[0028] 2-3 parts fiber;

[0029] 120-150 parts water.

[0030] Preferably, the fiber is a mixture of PVA fiber and polypropylene fiber in a volume ratio of 5:1.

[0031] Preferably, the thixotropic lubricant is magnesium aluminum silicate, used to improve the viscosity and anti-sagging properties of ECC concrete.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. The reinforcement method of this invention mainly addresses the problems of bending and shear cracking in the web of bridges such as box girders and hollow slab girders, as well as insufficient bearing capacity. It proposes a method for strengthening the bending / shear resistance of bridge webs based on distributed prestressed steel strands and shotcrete ECC concrete, which is an active reinforcement method that does not interrupt traffic. The reinforcement method of this invention can effectively solve the long-standing technical problems of low web reinforcement efficiency and easy material cracking.

[0034] 2. This reinforcement method involves adding prestress longitudinally to the bridge web. The axial pressure and bending moment generated by the prestress offset some of the internal forces generated by external loads, improving the bridge structure's bending and shear bearing capacity, delaying crack initiation, and increasing structural durability. Simultaneously, the use of distributed prestressed anchorage significantly reduces local stress concentration at the anchorage ends, avoiding damage risks in the anchorage zone, and resulting in stronger overall reinforcement.

[0035] 3. In this reinforcement method, the ECC material is applied using a spraying method, which can significantly improve construction progress and shorten the construction period. Using an ECC thickening layer increases the cross-section of the bridge web. The high ductility, high toughness, and crack resistance of ECC material enhance the bridge's shear capacity and cross-sectional stiffness, resulting in a thickness reduction of over 30% compared to traditional methods of increasing the cross-section, significantly reducing the added concrete weight and cost. Simultaneously, interface treatment ensures a tight bond between the ECC thickening layer and the original bridge web structure, allowing them to share the load, significantly improving the stress distribution of the bridge structure and enhancing its load-bearing capacity.

[0036] 4. This reinforcement method requires no special maintenance during construction, saving related expenses; the construction speed is fast, reducing costs caused by traffic control; the service performance and service life of the bridge are greatly improved after reinforcement, and no subsequent maintenance is required, reducing operating and maintenance costs and generating significant economic benefits. Attached Figure Description

[0037] Figure 1 A schematic diagram of the bridge structure before reinforcement;

[0038] Figure 2 This is a schematic diagram of the bridge structure after processing according to the present invention;

[0039] Figure 3 for Figure 2 Schematic diagram of a partial structure of the bridge web after reinforcement;

[0040] Figure 4 This is a schematic diagram of the web interface rebar anchoring structure of the present invention;

[0041] Figure 5 This is a schematic diagram of the distributed prestressed steel strand structure arranged at the web interface of the present invention.

[0042] Figure 6 This is a schematic diagram of the steel mesh arrangement at the web interface of the present invention;

[0043] Figure 7 This is a schematic diagram of the ECC material spraying structure at the web interface of the present invention;

[0044] Figure 8 A schematic diagram of stress distribution in the mid-span bottom slab of the bridge for reinforcement;

[0045] Figure 9 This is a schematic diagram of the stress distribution in the mid-span bottom slab after bridge reinforcement according to the present invention;

[0046] Figure 10 This is a bar chart illustrating the peak frequency of strain in the mid-span bottom slab before and after the bridge reinforcement according to the present invention.

[0047] Figure 11 for Figure 5 The corresponding images show the layout of prestressed steel strands and the tensioning and anchoring construction.

[0048] Figure 12 for Figure 7 Images of ECC (Electro-Concrete Composite) spraying construction.

[0049] Figure label:

[0050] 1. Bridge; 2. Web; 3. Prestressed steel strand; 4. Reinforcing mesh; 5. ECC thickening layer; 6. Shear pin; 7. Anchoring device; 8. Concrete spraying machine. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will be described in conjunction with the accompanying drawings of the embodiments of the present invention. Figure 1-12 The technical solutions of the embodiments of the present invention will be clearly and completely described herein. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0052] The embodiment of this invention selects a reinforcement project of a continuous box girder bridge with equal cross-section on the Shenhai Expressway. The bridge cross-section is a single box with three cells, and the bridge length is 44 meters. There are a large number of cracks and defects. The reinforcement method of this invention is used for reinforcement. The embodiment of this invention will be further described below with reference to the accompanying drawings.

[0053] Example 1:

[0054] like Figure 1-7 As shown, the present invention discloses a bridge composite reinforcement method based on ECC-distributed prestressing, comprising multiple prestressed steel strands 3 arranged longitudinally at intervals along the web 2 of the bridge, multiple shear pins 6 uniformly anchored along the interface of the web 2 of the bridge, with steel mesh 4 fixedly connected to the shear pins 6, and an ECC thickening layer 5 covering the prestressed steel strands 3, steel mesh 4, and shear pins 6 by spraying. Specifically, the two outermost webs 2 of the single-box three-cell box girder only require reinforcement of their inner interfaces, while the two central webs of the single-box three-cell box girder require reinforcement of both side interfaces to improve the tensile and shear strength of the individual box girder.

[0055] The reinforcement method of this invention specifically includes the following steps:

[0056] (1) Use a radar detector or a rebar locator to mark the position of the original beam rebar and steel strand in the reinforcement area on the interface to be reinforced in the web 2 of bridge 1, and mark it clearly, avoiding the position of the original beam rebar and steel strand, to ensure that the original beam rebar and steel strand will not be damaged during drilling, and complete the design drawings of the reinforcement site.

[0057] (2) Determine the positions of the prestressed steel strands 3, anchoring devices 7 and rebar holes on the interface of the web 2 of the bridge according to the design drawings, and then drill holes according to the process requirements.

[0058] (3) The concrete surface in the reinforcement area is roughened manually using a chisel. The surface is then roughened with a hammer, followed by the use of an electric hammer or hand hammer to chisel out pits on the roughened concrete surface. The pits are 3 mm deep and evenly distributed at a density of 600 pits / m². 2 Simultaneously, longitudinal grooves with a depth of 4 mm and a spacing of 50 mm are chiseled out at equal intervals along the longitudinal reinforcement interface of web 2.

[0059] (4) Use a brush and an extension rod to repeatedly pull back and forth into the bottom of the anchor hole to remove dust and debris; then blow out the floating dust in the anchor hole with compressed air, and then wash the concrete surface of the web plate 2 with pressurized water.

[0060] (5) Use absorbent cotton soaked in alcohol or acetone to wipe the inner wall of the anchoring hole; it should be noted that water should not be used to clean the anchoring hole, as alcohol or acetone evaporates easily while water does not. Washing with water will slow down the drying of the anchoring hole and delay the construction period; after cleaning the hole, put the anchoring adhesive into the glue gun, connect the glue gun to the mixing tube, insert the mixing tube into the bottom of the anchoring hole, and inject the anchoring adhesive from the bottom of the anchoring hole outward. It is advisable to fill 2 / 3 of the depth of the anchoring hole with the anchoring adhesive to ensure the fullness of the anchoring; after the adhesive is injected into the anchoring hole, put the rust-removed shear pin 6 into the anchoring hole, and then slowly screw it in one direction. Do not reverse the direction in the middle, until the shear pin 6 reaches the bottom of the anchoring hole; the insertion depth of the shear pin 6 is greater than 5 cm, and the distance of the shear pin 6 extending out of the anchoring hole is 5 cm. The shear pin 6 is arranged in a 20 cm × 20 cm quincunx pattern; the distance between the shear pin and the edge of the web 2 should not be less than 100 mm. mm, after the anchoring adhesive has completely cured, the next process can be carried out.

[0061] (6) Install anchoring devices 7 according to the design location. Prestressed steel strands 3 are longitudinally spaced on the surface of the bridge web. The prestressed steel strands 3 are then tensioned sequentially, one at a time, using the front-clamping jacks in the anchoring devices 7. There can be one or more anchoring devices 7; multiple prestressed steel strands 3 can share one anchoring device 7, or a single prestressed steel strand 3 can correspond to one anchoring device 7. The prestressed steel strands 3 are one of galvanized steel strands, epoxy-coated steel strands, or indented steel strands, and the bundle type of the prestressed steel strands 3 is either straight or zigzag. Specifically, nine steel strands Фs15.2-1 are longitudinally arranged on the surface of the web 2 at 10 cm intervals. Every three prestressed steel strands 3 share one anchoring device 7. The anchoring device 7 can be an existing anchoring device. The prestressed steel strands are then tensioned sequentially, one at a time, using the front-clamping jacks in the anchoring device. The tensioning control force of the prestressed steel strands is 16.6 t. The construction process is as follows: Figure 5-7 and Figure 11 As shown.

[0062] (7) A steel mesh 4 is longitudinally arranged on the surface of the web of the bridge outside the prestressed steel strand 3. The mesh size of the steel mesh 4 is 10cm×15cm. The steel mesh 4 is fixedly connected to the protruding end of the shear pin 6 by welding or binding and connected into an integral structure.

[0063] (8) After the steel mesh 4 is installed, the surface of the bridge web is moistened with water and the concrete surface is kept saturated and dry (no water accumulation or water film on the surface). Depending on the situation, a concrete composite interface agent, such as vinyl acetate or ethylene adhesive, is sprayed, and then the next process is carried out.

[0064] (9) Prepare ECC material, which consists of the following raw materials in parts by weight: 300 parts of PO 52.5 silicate cement; 50 parts of fly ash; 500 parts of fine aggregate; 0.5 parts of water-reducing agent (polycarboxylate water-reducing agent can be selected); 40 parts of expanding agent (calcium oxide expanding agent can be selected); 1 part of thixotropic lubricant (magnesium aluminum silicate used to improve the viscosity and anti-sagging properties of ECC concrete); 2 parts of fiber (the fiber is a mixture of PVA fiber and polypropylene fiber in a volume ratio of 5:1); and 120 parts of water. Mix the ECC material evenly to prepare a slurry concrete, and then use a concrete spraying machine 8 for spraying construction. The spraying construction process adopts a block and layer method to ensure effective and continuous operation during spraying. The reinforcement thickness of ECC layer 5 is 10 cm, with each sprayed layer approximately 3 cm thick. The next layer of concrete is applied after the first layer has initially set. Once the ECC concrete reaches the required quantity and thickness as per the construction plan, the surface of the ECC layer is smoothed and finished with a trowel. Smoothing should ideally be done after the final layer of ECC concrete has been applied. After the ECC concrete has fully set, water curing is performed. The sprayed concrete construction process is as follows: Figure 7 and Figure 12 As shown.

[0065] Example 2:

[0066] like Figure 1-7 As shown, the present invention discloses a bridge composite reinforcement method based on ECC-distributed prestressing, comprising multiple prestressed steel strands 3 arranged longitudinally at intervals along the web 2 of the bridge, multiple shear pins 6 uniformly anchored along the interface of the web 2 of the bridge, with steel mesh 4 fixedly connected to the shear pins 6, and an ECC thickening layer 5 covering the prestressed steel strands 3, steel mesh 4, and shear pins 6 by spraying. Specifically, the two outermost webs 2 of the single-box three-cell box girder only require reinforcement of their inner interfaces, while the two central webs of the single-box three-cell box girder require reinforcement of both side interfaces to improve the tensile and shear strength of the individual box girder.

[0067] The reinforcement method of this invention specifically includes the following steps:

[0068] (1) Use a radar detector or a rebar locator to mark the position of the original beam rebar and steel strand in the reinforcement area on the interface to be reinforced in the web 2 of bridge 1, and mark it clearly, avoiding the position of the original beam rebar and steel strand, to ensure that the original beam rebar and steel strand will not be damaged during drilling, and complete the design drawings of the reinforcement site.

[0069] (2) Determine the positions of the prestressed steel strands 3, anchoring devices 7 and rebar holes on the interface of the web 2 of the bridge according to the design drawings, and then drill holes according to the process requirements.

[0070] (3) The concrete surface in the reinforcement area is roughened manually using a chisel. The surface is roughened with a hammer, and then an electric hammer or hand hammer is used to chisel out pits on the roughened concrete surface. The pits are 3 mm deep and the density of the pits is 700 points / m². 2 Simultaneously, longitudinal grooves with a depth of 4.5 mm and a spacing of 50 mm are chiseled out at equal intervals along the longitudinal reinforcement interface of web 2.

[0071] (4) Use a brush and an extension rod to repeatedly pull back and forth into the bottom of the anchor hole to remove dust and debris; then blow out the floating dust in the anchor hole with compressed air, and then wash the concrete surface of the web plate 2 with pressurized water.

[0072] (5) Use absorbent cotton soaked in alcohol or acetone to clean the inner wall of the rebar hole; it should be noted that water should not be used to clean the rebar hole, as alcohol or acetone is volatile, while water is not. Cleaning with water will slow down the drying of the rebar hole and delay the construction period; after cleaning the hole, put the rebar adhesive into the glue gun, connect the glue gun to the mixing tube, insert the mixing tube into the bottom of the rebar hole, and inject the rebar adhesive from the bottom of the rebar hole outward. It is advisable to fill the rebar hole with 2 / 3 of its depth to ensure the fullness of the rebar after installation; after the adhesive is injected into the rebar hole, put the rust-removed shear pin 6 into the opening of the rebar hole, and then slowly screw it in one direction. Do not reverse the direction midway until the shear pin 6 reaches the bottom of the rebar hole; the insertion depth of the shear pin 6 should be greater than 5cm, and the distance of the shear pin 6 extending out of the rebar hole should be 5cm. The shear pin 6 should be arranged in a 20cm×20cm quincunx pattern; the distance between the shear pin and the edge of the web 2 should not be less than 100. mm, after the anchoring adhesive has completely cured, the next process can be carried out.

[0073] (6) Install anchoring devices 7 according to the design location. Prestressed steel strands 3 are longitudinally spaced on the surface of the bridge web. The prestressed steel strands 3 are then tensioned sequentially, one at a time, using the front-clamping jacks in the anchoring devices 7. There can be one or more anchoring devices 7; multiple prestressed steel strands 3 can share one anchoring device 7, or a single prestressed steel strand 3 can correspond to one anchoring device 7. The prestressed steel strands 3 are one of galvanized steel strands, epoxy-coated steel strands, or indented steel strands, and the bundle type of the prestressed steel strands 3 is either straight or zigzag. Specifically, nine steel strands Фs15.2-1 are longitudinally arranged on the surface of the web 2 at 10 cm intervals. Every three prestressed steel strands 3 share one anchoring device 7. The anchoring device 7 can be an existing anchoring device. The prestressed steel strands are then tensioned sequentially, one at a time, using the front-clamping jacks in the anchoring device. The tensioning control force of the prestressed steel strands is 16.6 t. The construction process is as follows: Figure 5-7 and Figure 11 As shown.

[0074] (7) A steel mesh 4 is longitudinally arranged on the surface of the web of the bridge outside the prestressed steel strand 3. The mesh size of the steel mesh 4 is 10cm×15cm. The steel mesh 4 is fixedly connected to the protruding end of the shear pin 6 by welding or binding and connected into an integral structure.

[0075] (8) After the steel mesh 4 is installed, the surface of the bridge web is moistened with water and the concrete surface is kept saturated and dry (no water accumulation or water film on the surface). Depending on the situation, a concrete composite interface agent, such as vinyl acetate or ethylene adhesive, is sprayed, and then the next process is carried out.

[0076] (9) Prepare ECC material, which consists of the following raw materials in parts by weight: 350 parts of PO 52.5 silicate cement; 65 parts of fly ash; 550 parts of fine aggregate; 0.75 parts of water-reducing agent (polycarboxylate superplasticizer can be selected); 50 parts of expanding agent (calcium oxide expanding agent can be selected); 1.5 parts of thixotropic lubricant (magnesium aluminum silicate used to improve the viscosity and anti-sagging properties of ECC concrete); 2.5 parts of fiber (a mixture of PVA fiber and polypropylene fiber in a volume ratio of 5:1); and 135 parts of water. Mix the ECC material evenly to prepare a slurry concrete, and then use a concrete spraying machine 8 for spraying. The spraying process is carried out in blocks and layers to ensure effective and continuous operation during spraying. The reinforcement thickness of ECC layer 5 is 12.5 cm, with each sprayed layer approximately 3.5 cm thick. The next layer of concrete is applied after the first layer has initially set. Once the ECC concrete reaches the required quantity and thickness as per the construction plan, the surface of the ECC layer is smoothed and finished with a trowel. Smoothing should ideally be done after the final layer of ECC concrete has been applied. After the ECC concrete has fully set, it is then water-cured. The sprayed concrete construction process is as follows: Figure 7 and Figure 12 As shown.

[0077] Example 3:

[0078] like Figure 1-7 As shown, the present invention discloses a bridge composite reinforcement method based on ECC-distributed prestressing, comprising multiple prestressed steel strands 3 arranged longitudinally at intervals along the web 2 of the bridge, multiple shear pins 6 uniformly anchored along the interface of the web 2 of the bridge, with steel mesh 4 fixedly connected to the shear pins 6, and an ECC thickening layer 5 covering the prestressed steel strands 3, steel mesh 4, and shear pins 6 by spraying. Specifically, the two outermost webs 2 of the single-box three-cell box girder only require reinforcement of their inner interfaces, while the two central webs of the single-box three-cell box girder require reinforcement of both side interfaces to improve the tensile and shear strength of the individual box girder.

[0079] The reinforcement method of this invention specifically includes the following steps:

[0080] (1) Use a radar detector or a rebar locator to mark the position of the original beam rebar and steel strand in the reinforcement area on the interface to be reinforced in the web 2 of bridge 1, and mark it clearly, avoiding the position of the original beam rebar and steel strand, to ensure that the original beam rebar and steel strand will not be damaged during drilling, and complete the design drawings of the reinforcement site.

[0081] (2) Determine the positions of the prestressed steel strands 3, anchoring devices 7 and rebar holes on the interface of the web 2 of the bridge according to the design drawings, and then drill holes according to the process requirements.

[0082] (3) The concrete surface in the reinforcement area is roughened manually using a chisel. The surface is roughened with a hammer, and then an electric hammer or hand hammer is used to chisel out pits on the roughened concrete surface. The pits are 3 mm deep and the density of the pits is 800 points / m². 2 Simultaneously, longitudinal grooves with a depth of 5 mm and a spacing of 50 mm are chiseled out at equal intervals along the longitudinal reinforcement interface of web 2.

[0083] (4) Use a brush and an extension rod to repeatedly pull back and forth into the bottom of the anchor hole to remove dust and debris; then blow out the floating dust in the anchor hole with compressed air, and then wash the concrete surface of the web plate 2 with pressurized water.

[0084] (5) Use absorbent cotton soaked in alcohol or acetone to clean the inner wall of the rebar hole; it should be noted that water should not be used to clean the rebar hole, as alcohol or acetone is volatile, while water is not. Cleaning with water will slow down the drying of the rebar hole and delay the construction period; after cleaning the hole, put the rebar adhesive into the glue gun, connect the glue gun to the mixing tube, insert the mixing tube into the bottom of the rebar hole, and inject the rebar adhesive from the bottom of the rebar hole outward. It is advisable to fill the rebar hole with 2 / 3 of its depth to ensure the fullness of the rebar after installation; after the adhesive is injected into the rebar hole, put the rust-removed shear pin 6 into the opening of the rebar hole, and then slowly screw it in one direction. Do not reverse the direction midway until the shear pin 6 reaches the bottom of the rebar hole; the insertion depth of the shear pin 6 should be greater than 5cm, and the distance of the shear pin 6 extending out of the rebar hole should be 5cm. The shear pin 6 should be arranged in a 20cm×20cm quincunx pattern; the distance between the shear pin and the edge of the web 2 should not be less than 100. mm, after the anchoring adhesive has completely cured, the next process can be carried out.

[0085] (6) Install anchoring devices 7 according to the design location. Prestressed steel strands 3 are longitudinally spaced on the surface of the bridge web. The prestressed steel strands 3 are then tensioned sequentially, one at a time, using the front-clamping jacks in the anchoring devices 7. There can be one or more anchoring devices 7; multiple prestressed steel strands 3 can share one anchoring device 7, or a single prestressed steel strand 3 can correspond to one anchoring device 7. The prestressed steel strands 3 are one of galvanized steel strands, epoxy-coated steel strands, or indented steel strands, and the bundle type of the prestressed steel strands 3 is either straight or zigzag. Specifically, nine steel strands Фs15.2-1 are longitudinally arranged on the surface of the web 2 at 10 cm intervals. Every three prestressed steel strands 3 share one anchoring device 7. The anchoring device 7 can be an existing anchoring device. The prestressed steel strands are then tensioned sequentially, one at a time, using the front-clamping jacks in the anchoring device. The tensioning control force of the prestressed steel strands is 16.6t. The construction process is as follows: Figure 5-7 and Figure 11 As shown.

[0086] (7) A steel mesh 4 is longitudinally arranged on the surface of the web of the bridge outside the prestressed steel strand 3. The mesh size of the steel mesh 4 is 10cm×15cm. The steel mesh 4 is fixedly connected to the protruding end of the shear pin 6 by welding or binding and connected into an integral structure.

[0087] (8) After the steel mesh 4 is installed, the surface of the bridge web is moistened with water and the concrete surface is kept saturated and dry (no water accumulation or water film on the surface). Depending on the situation, a concrete composite interface agent, such as vinyl acetate or ethylene adhesive, is sprayed, and then the next process is carried out.

[0088] (9) Prepare ECC material, which consists of the following raw materials in parts by weight: 400 parts of PO 52.5 silicate cement; 80 parts of fly ash; 600 parts of fine aggregate; 1 part of water-reducing agent (polycarboxylate superplasticizer can be selected); 60 parts of expanding agent (calcium oxide expanding agent can be selected); 2 parts of thixotropic lubricant (magnesium aluminum silicate used to improve the viscosity and anti-sagging properties of ECC concrete); 3 parts of fiber (the fiber is a mixture of PVA fiber and polypropylene fiber in a volume ratio of 5:1); and 150 parts of water. Mix the ECC material evenly to prepare a slurry concrete, and then use a concrete spraying machine 8 for spraying construction. The spraying construction process adopts a block and layer method to ensure effective and continuous operation during spraying. The reinforcement thickness of ECC layer 5 is 15cm, with each sprayed layer approximately 4cm thick. The next layer of concrete is applied after the first layer has initially set. Once the ECC concrete reaches the required quantity and thickness as per the construction plan, the surface of the ECC layer is smoothed and finished with a trowel. Smoothing should ideally be done after the final layer of ECC concrete has been applied. After the ECC concrete has fully set, water curing is performed. The sprayed concrete construction process is as follows: Figure 7 and Figure 12 As shown.

[0089] The effectiveness of the reinforcement method of the present invention is further illustrated by the following test results:

[0090] Figure 8 and Figure 9 A schematic diagram of the stress distribution in the mid-span bottom slab of a bridge before and after web reinforcement, for comparison. Figure 8 and Figure 9 It can be seen that before reinforcement, the strain peaks of the bridge mid-span bottom plate were mostly distributed between 5 and 15 µε, and the frequency of peaks in other ranges was relatively low, but there were also peaks exceeding 20 µε, with the maximum value being 26 µε; after reinforcement using the reinforcement method of the present invention, the strain peaks of the bridge mid-span bottom plate no longer exceeded 15 µε. Figure 10 A bar chart illustrating the peak frequency of strain in the mid-span bottom slab before and after bridge reinforcement, by Figure 10 It can be seen that the strain range with the highest frequency of peak strain in the mid-span bottom slab of the bridge before reinforcement was 9-11µε, while the strain range with the highest frequency of peak strain in the mid-span bottom slab of the bridge after reinforcement was 7-9µε. The peak value of the distribution curve after reinforcement shifted significantly to the left compared to before reinforcement. In summary, under the condition of relatively uniform traffic flow of various types of vehicles, the overall response of the bridge bottom slab after reinforcement was significantly reduced, indicating that the reinforcement method of the present invention greatly improved the bearing capacity and overall stiffness of the bridge structure.

[0091] The above are preferred embodiments of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A bridge composite reinforcement method based on ECC-distributed prestressing, characterized in that, The reinforcement method includes multiple prestressed steel strands (3) arranged longitudinally along the web (2) of the bridge, multiple shear pins (6) uniformly anchored along the interface of the web (2) of the bridge, and steel mesh (4) fixedly connected to the shear pins (6), and an ECC thickening layer (5) covering the prestressed steel strands (3), steel mesh (4) and shear pins (6) by spraying; the reinforcement method specifically includes the following steps: Step S1: Use a radar detector or rebar locator to mark the location of the original beam rebar and steel strands in the reinforcement area, avoid the original beam rebar and steel strand locations, and design reinforcement site drawings; Step S2: Determine the location of the prestressed steel strands (3), anchoring devices (7) and rebar holes on the interface of the bridge web (2) according to the design drawings, and then drill holes according to the process requirements; Step S3: Roughen the concrete surface in the reinforcement area manually. The roughening process involves using a chisel to create a rough surface, followed by using an electric hammer or hand hammer to chisel out pits on the roughened concrete surface. The pits should be 3mm deep and evenly distributed at a density of 600-800 points / m². 2 ; Step S4: Use a brush to repeatedly pull back and forth into the bottom of the anchor hole to remove dust and debris; then use compressed air to blow out the floating dust in the anchor hole, and then wash the concrete surface with pressurized water. Step S5: Use degreased cotton soaked in alcohol or acetone to wipe the inner wall of the rebar hole, then inject rebar adhesive into the rebar hole, filling 2 / 3 of the rebar hole, and insert shear pins (6) into the corresponding rebar hole in the abdominal plate; wherein the insertion depth of the shear pins (6) is greater than 5cm, and the distance of the shear pins (6) extending out of the rebar hole is 5mm; the distance between the shear pins and the edge of the abdominal plate (2) should not be less than 100mm; Step S6: Install anchoring devices (7) according to the design location, arrange prestressed steel strands (3) longitudinally at intervals on the surface of the bridge web, and tension the prestressed steel strands (3) one by one in stages through the front clamp jack in the anchoring device (7); wherein the prestressed steel strands (3) are one of galvanized steel strands, epoxy resin coated steel strands, and indented steel strands, and the bundle type of the prestressed steel strands (3) is straight or broken; there can be one or more anchoring devices (7); multiple prestressed steel strands (3) can share one anchoring device (7), or one prestressed steel strand (3) corresponds to one anchoring device (7); Step S7: Arrange a steel mesh (4) on the surface of the bridge web outside the prestressed steel strands (3) and fix the steel mesh (4) to the shear pins (6); Step S8: Moisten the surface of the bridge web with water and keep the concrete surface saturated and dry. Step S9: Prepare ECC material and spray a 10-15cm thick ECC concrete layer onto the surface of the bridge web using a wet spraying method to form an ECC thickening layer (5); wherein the ECC material is composed of the following raw materials in parts by weight: 300-400 parts of PO 52.5 silicate cement; 50-80 parts of fly ash; 500-600 parts of fine aggregate; 0.5-1 part of water-reducing agent; 40-60 parts of expansion agent; 1-2 parts of thixotropic lubricant; 2-3 parts of fiber; and 120-150 parts of water.

2. The bridge composite reinforcement method based on ECC-distributed prestressing according to claim 1, characterized in that: In step S7, the steel mesh (4) is arranged along the longitudinal direction of the bridge and is fixedly connected to the protruding end of the shear pin (6) by welding or binding to form an integral structure.

3. The bridge composite reinforcement method based on ECC-distributed prestressing according to claim 2, characterized in that: The grid size in step S7 is 10cm × 15cm.

4. The bridge composite reinforcement method based on ECC-distributed prestressing according to claim 1, characterized in that, The fiber is a mixture of PVA fiber and polypropylene fiber in a volume ratio of 5:

1.

5. The bridge composite reinforcement method based on ECC-distributed prestressing according to claim 1, characterized in that, The thixotropic lubricant is magnesium aluminum silicate, used to improve the viscosity and anti-sagging properties of ECC concrete.

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