CN111827147B - Box-type arch bridge splicing section and arch foot section reinforcing method - Google Patents

Box-type arch bridge splicing section and arch foot section reinforcing method Download PDF

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CN111827147B
CN111827147B CN202010804008.9A CN202010804008A CN111827147B CN 111827147 B CN111827147 B CN 111827147B CN 202010804008 A CN202010804008 A CN 202010804008A CN 111827147 B CN111827147 B CN 111827147B
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tensioning
arch
anchoring
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reinforcing
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CN111827147A (en
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杨雨厚
宁怡豪
郝天之
黎力韬
王海华
李丽琳
张桥
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Guangxi Jiaoke Group Co Ltd
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    • E—FIXED CONSTRUCTIONS
    • E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
    • E01D—CONSTRUCTION OF BRIDGES, ELEVATED ROADWAYS OR VIADUCTS; ASSEMBLY OF BRIDGES
    • E01D22/00—Methods or apparatus for repairing or strengthening existing bridges ; Methods or apparatus for dismantling bridges
    • E—FIXED CONSTRUCTIONS
    • E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
    • E01D—CONSTRUCTION OF BRIDGES, ELEVATED ROADWAYS OR VIADUCTS; ASSEMBLY OF BRIDGES
    • E01D4/00—Arch-type bridges

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Abstract

The invention discloses a method for reinforcing a splicing section and an arch foot section of a box-type arch bridge, wherein the method for reinforcing the splicing section mainly adopts a fiber woven mesh tensioning unit and an ultrahigh-toughness cement-based material to realize reinforcement in a reinforcing area, the method for reinforcing the arch foot section mainly adopts an FRP mesh tensioning unit, a bottom ECC material and a top ECC material to realize reinforcement in the reinforcing area, the tensioning units of the two reinforcing methods can weave fiber nets with different cross-sectional areas by increasing or reducing the number of yarns to meet the requirements of different tensile strengths, the method can be cut according to the size of the reinforcing area, the fiber nets are tensioned and anchored to the surface of a structure through a clamp, the base material does not exceed 2.5 percent of the total volume through the fiber mixing amount, the ultimate tensile strain stably reaches more than 1 percent, so that the material has obvious strain hardening characteristics, and the crack development of the surface of the structure is effectively inhibited. The reinforcing method can solve the problem of stress lag of the reinforcing layer to the maximum extent, not only enhances the integrity of the reinforced structure, but also obviously improves the durability of the structure.

Description

Box-type arch bridge splicing section and arch foot section reinforcing method
Technical Field
The invention relates to the technical field of bridge maintenance and reinforcement, in particular to a method for reinforcing a splicing section and an arch foot section of a box-type arch bridge.
Background
Since the 80 s of the last century, a large number of reinforced concrete arch bridges are built in China, particularly in the southwest region. With the rapid development of construction technology and the development of large-scale hoisting equipment and instruments, the reinforced concrete box-type arch bridge gradually becomes the dominant bridge type of the concrete arch bridge.
The existing reinforced concrete box type arch bridge has the following problems:
1) the main arch ring of the box-type arch bridge is generally formed by segmental prefabrication and assembly, and the construction quality of the assembly section needing to be processed on site is difficult to ensure. From many box type arch bridge testing results, most box type arch bridge splice section department concrete has diseases such as damage, reinforcing bar or steel sheet expose, and this is not good with construction quality and guarantees well, still with this structural integrity is poor, the atress is relatively weak, produces concrete corrosion easily and is relevant. Under the influence of the factors and the interaction among the factors, the splicing section of the box-type arch bridge becomes a key part influencing the bearing capacity and the durability of the whole structure, and the selection of the maintenance and reinforcement method of the key part is very important.
2) The main arch ring is used as a main bearing component of the arch bridge, and under the action of constant load and live load, besides the pressure in the arch axis direction, a large negative bending moment can be generated at the arch foot position. Along with the increase of the operation life of the bridge, the material performance is deteriorated due to the influence of various actions such as vehicle overload, overrun and environmental factors, the structural strength is reduced, the phenomena such as cracks and damages are generated at the tension area of the main arch ring, and the structural bearing capacity is reduced. Therefore, the box-type arch bridge arch foot section also becomes a key part influencing the bearing capacity and durability of the whole structure, and the selection of a maintenance and reinforcement method of the key part is also important.
According to the design specification for reinforcing highway bridges (JTG/T J22-2008) and the design specification for reinforcing concrete structures (GB 50367 and 2013), the conventional technical approaches for repairing and reinforcing arch bridges are as follows: the section enlarging method (including reinforced concrete hoop reinforcement), the steel plate (section steel) adhering reinforcement method, the fiber composite adhering reinforcement method and the pre-tensioned steel wire rope (steel strand) mesh-polymer mortar surface layer reinforcement method respectively have advantages and disadvantages, and are detailed in table 1.
TABLE 1 common strengthening method for arch bridge
Figure GDA0003353826480000011
Figure GDA0003353826480000021
In the work of bridge detection and reinforcement, the applicant encounters the example that the existing reinforcement method for the arch bridge is difficult to achieve the expected target, and typically, two reinforced concrete box arch bridges are provided, wherein the former adopts a reinforcement method of adhering steel plates to the arch belly, and the latter adopts a method of reinforcing arch foot sections by using reinforced concrete hoops. However, after the first bridge is reinforced for 5 years, the steel plate void ratio reaches 32% of the total number of spot checks, and 10 steel plates are completely void. In the latter bridge, within 3 months after the reinforcement, a through crack appears between the hoop reinforcement layer and the original structure along the joint surface. The two bridge reinforcing cases are examples and show common problems, and in the feedback of the reinforcing effect of the management and maintenance unit, the applicant finds that a better scheme is not provided for reinforcing the arch bridge, particularly reinforcing the splicing section and the arch foot section of the box-type arch bridge, so that a novel reinforcing technology needs to be developed.
Disclosure of Invention
In view of the above, there is a need for a box arch bridge splicing section and a method for reinforcing a arch leg section, which can suppress the propagation of cracks on the surface of the arch leg section, reduce the surface defects of the structure, and improve the bearing capacity of the arch bridge and the integrity and durability of the splicing section and the arch leg section.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
aiming at a box type arch bridge splicing section, the invention provides a box type arch bridge splicing section reinforcing method, which comprises the following steps:
1) determining a reinforced area according to the defect condition of the splicing section of the box-type arch bridge;
2) treating the concrete surface of the reinforced area: firstly, removing degraded concrete with the surface of which is peeled, loosened, sanded, weathered, honeycombed or corroded, and performing chiseling treatment until a new surface of aggregate is exposed, wherein the surface roughness of the new surface of the aggregate is not less than 5 mm; then, chamfering the box arch corner of the reinforced area, wherein the chamfer radius is not less than 25 mm;
3) determining the position of an arch rib steel bar by using a steel bar detector, marking an anchoring position, fixing an anchoring base plate on the anchoring position by using structural adhesive, drilling a hole in the anchoring base plate by using an impact drill, wherein the hole extends into concrete in a reinforced area, and the anchoring base plate is fixed on the reinforced area in a mode that an anchoring screw rod is inserted into the hole through threads; the operation avoids the main rib of the original structure;
4) washing the surface of the concrete in the reinforced area by using high-pressure water, filling the chamfer part of the arch of the box with an ultrahigh-toughness cement-based material, wherein the ultrahigh-toughness cement-based material is designed by taking one of cement, cement filler and small-particle-size fine aggregate as a matrix and then using short fibers as a reinforcing material;
5) the width of the fiber woven mesh tensioning unit and the number of stressed fiber bundles contained in each tensioning unit are reasonably selected by comprehensively considering the length of a reinforced area, the shear strength of an anchoring screw and a plurality of tensioning tons; each fiber woven mesh needs to be subjected to viscose sand hanging treatment;
6) tensioning fiber woven nets in batches after the ultra-high-toughness cement-based material at the chamfer part reaches a certain strength, wherein four fiber woven net tensioning units form a closed tensioning ring, each tensioning unit of one closed tensioning ring is tensioned and anchored completely and then tensioned and tensioned with the next closed tensioning ring, and during tensioning, the tensioning is performed by external and internal symmetrical tensioning construction;
7) spraying a structural interface agent for concrete on the surface of a reinforced area, uniformly pressing and smearing the prepared ultra-high toughness cement-based material on the surface of an arch rib, smoothing and leveling, and ensuring compactness and flatness; when the ultra-high toughness cement-based material is pressed and smeared, the pressing and smearing thickness of the ultra-high toughness cement-based material is not more than 25mm, the pressing and smearing thickness is more than time-division pressing and smearing, and the pressing and smearing time interval of two adjacent layers of the ultra-high toughness cement-based material is determined by initial setting of the former layer of material;
8) the water spraying maintenance is carried out on the construction surface within 0.5-4 hours after the ultra-high toughness cement-based material is pressed, smeared and polished, the maintenance time is not less than 7 days, and the reinforced part is prevented from being impacted by hard objects in the period.
Further, in step 6), the tensioning method of each fiber woven mesh tensioning unit is as follows: firstly, winding a rubber rod at one end of a fiber woven mesh and then sleeving the fiber woven mesh into an aluminum alloy clamp, fixedly connecting the aluminum alloy clamp with an anchoring base plate by using an anchoring screw rod and a high-strength bolt, winding the rubber rod at the other end of the fiber woven mesh and then sleeving the fiber woven mesh into the aluminum alloy clamp, tensioning the fiber woven mesh to a preformed hole of the anchoring base plate by using tensioning equipment, inserting the fiber woven mesh into the anchoring screw rod, and fixing the fiber woven mesh with the high-strength bolt.
Furthermore, the fiber woven mesh of each fiber woven mesh tensioning unit adopts a unidirectional grid and is formed by weaving mutually vertical carbon fiber wires and glass fiber wires, wherein the carbon fiber wires are adopted in the stressed direction, and the glass fiber wires are adopted in the unstressed direction; the blanking length of the fiber woven mesh is measured by tests to control the tensile strain epsilon of the stress and the size L of the inner edge of the anchorage deviceiThe reserved length L of the anchoring endeAnd calculating the blanking length L of the fiber woven mesh according to the following formula0：
L0＝Li/(1+ε)+2Le，
In actual engineering, the tensile control stress of the fiber woven mesh is 0.5 times of the design value of the tensile strength of the fiber woven mesh in the stress direction, and the allowable deviation is +/-10%.
Furthermore, the mixing amount of the short fiber of the ultra-high toughness cement-based material is not more than 2.5 percent of the total volume, and the ultimate tensile strain of the ultra-high toughness cement-based material is stably more than 1 percent.
Compared with the prior art, the splicing section reinforcing method has the following beneficial effects: the method belongs to an active bridge reinforcing method, can solve the problem of stress lag of a reinforcing layer to the maximum extent, and fully utilizes the high-strength characteristic of a fiber woven net; secondly, the reinforcing layer is thin, only pressing and smearing construction is needed, and heavy templates and supporting systems are not needed, so that the field construction operation is simple, the speed is high, and the safety risk is low; the adopted cement-based material with ultrahigh toughness has very high ultimate tensile strain, obvious strain hardening characteristic and can generate a plurality of fine cracks under the action of tensile stress, and the fine cracks are favorable for inhibiting the crack development at the splicing section. Even if cracks are generated, the speed of harmful media such as water or carbon dioxide entering the structure can be obviously reduced due to the control of the width of the cracks; fourthly, the fiber woven mesh is adopted as a stress material, and due to the material characteristics, the fiber woven mesh can resist aging, fatigue and corrosion, so that no special requirement is imposed on the thickness of the protective layer; the fiber woven mesh can meet the requirements of different tensile strengths by increasing or reducing the number of yarns and weaving meshes with different cross sections, and can be designed to be strong; in addition, the fiber material has soft texture and strong construction operability; the reinforcing layer has good chemical stability and durability, the integrity of the reinforced structure can be enhanced, and the durability of the structure can be obviously improved.
In addition, aiming at the box type arch bridge arch foot section, the invention also provides a box type arch bridge arch foot section reinforcing method, which comprises the following steps:
1) determining a reinforced area according to the defect condition of the arch leg of the box arch;
2) treating the concrete surface of the reinforced area: firstly, removing degraded concrete with the surface of the concrete stripped, loosened, sanded, weathered, honeycombed or corroded, roughening, exposing a new surface of an aggregate, washing the new surface of the aggregate by high-pressure water, and grouting cracks with the width of more than 0.15mm, wherein the roughness of the new surface of the aggregate is not less than 6 mm;
3) determining the position of an arch rib steel bar by using a steel bar detector, then performing steel bar planting hole position lofting, drilling and hole cleaning treatment to ensure the accuracy of the hole position and the effective depth of the drilling, and avoiding the main steel bar of the original structure by the operation;
4) planting bars, determining the anchoring depth strictly according to the design requirements, and selecting proper structural adhesive through a field drawing test;
5) installing a template and binding a reinforcing mesh on the arch back of the reinforced area;
6) the arch back reinforced concrete is poured, in order to reduce the influence of concrete shrinkage, the reinforced concrete adopts a construction process of sectional cast-in-place, and roughening treatment is carried out on the surface of the concrete after pouring is finished;
7) after the strength of the arch back reinforced concrete reaches 95% of the design strength, fixing the anchoring base plate by using structural adhesive, drilling at the position of the anchoring screw by using an impact drill, avoiding a reinforcing steel bar during drilling, and cleaning the reinforcing area of the arch foot section by using high-pressure water after the drilling is finished;
8) spraying a structural interface agent for concrete on the surface of a reinforced area, uniformly pressing and smearing a prepared bottom ECC material (an ultrahigh-toughness cement-based material) on the surface of the reinforced area, and chamfering edges and corners around the arch leg section in the pressing and smearing process, wherein the radius of the chamfer is not less than 25 mm;
9) comprehensively considering the conditions of the area of a reinforced area, the shear strength of an anchoring screw, the tensioning tonnage and the like, and reasonably selecting the width of an FRP (fiber mesh) tensioning unit and the number of stressed fiber bundles contained in each tensioning unit; carrying out viscose sand hanging treatment before tensioning the FRP net;
10) tensioning FRP net tensioning units in batches, wherein the four FRP net tensioning units form a closed tensioning ring, each FRP net tensioning unit of one closed tensioning ring is tensioned and anchored after the tensioning unit is tensioned and anchored, and tensioning construction is carried out symmetrically from outside to inside during tensioning;
11) uniformly pressing and smearing the prepared top ECC material on the surface of the arch springing section, smoothing and leveling to ensure compactness and flatness, wherein the pressing and smearing time interval of the top ECC material is subject to initial setting of the bottom ECC material;
12) and (3) performing water spraying maintenance on the construction surface within 0.5-4 hours after the ECC material is pressed and smeared, wherein the maintenance time is not less than 7 days, and the reinforced part is prevented from being impacted by hard objects during the maintenance time.
Further, in step 10), the tensioning method of each tensioning unit is as follows: firstly, winding a rubber rod at one end of an FRP net and then sleeving the FRP net into an aluminum alloy clamp, fixedly connecting the aluminum alloy clamp with an anchoring backing plate by using an anchoring screw rod and a high-strength bolt, winding the rubber rod at the other end of the FRP net and then sleeving the FRP net into the aluminum alloy clamp, tensioning the FRP net to a preformed hole of the anchoring backing plate by using tensioning equipment, inserting the anchoring screw rod and fixing the FRP net by using the high-strength bolt.
Furthermore, the FRP net adopts a unidirectional grid which is formed by weaving mutually perpendicular carbon fiber wires/glass fiber wires, wherein the carbon fiber wires are adopted in the stress direction, the glass fiber wires are adopted in the non-stress direction, the blanking length of the FRP net is actually measured through tests to control the stress pull-down strain epsilon and the anchorage device inner edge size LiThe reserved length L of the anchoring endeAnd calculating the blanking length L of the FRP net according to the following formula0：
L0＝Li/(1+ε)+2Le，
In actual engineering, the tensile control stress of the FRP net is 0.5 times of the design value of the tensile strength of the FRP net in the stress direction, and the allowable deviation is +/-10%.
Further, the thickness of the bottom layer ECC material pressed is not less than the thickness of the FRP net and not more than 20 mm.
Furthermore, the bottom ECC material is designed by taking cement or cement and filler or small-particle-size fine aggregate as a matrix and short fiber as a reinforcing material, wherein the fiber content does not exceed 2.5 percent of the total volume of the bottom ECC material, and the ultimate tensile strain of the bottom ECC material is stabilized to be more than 1 percent.
Compared with the prior art, the invention has the following beneficial effects: the method belongs to a method for combining active reinforcement and passive reinforcement of a bridge, can solve the problem of stress lag of a reinforcement layer to the maximum extent, fully utilizes the high-strength characteristic of an FRP net, can remarkably increase the section area of a member, and improves the rigidity and the bearing capacity of a structure; secondly, the construction process of pouring the reinforced concrete of the arch backs of the arch springing sections is mature, the FRP net is conveniently and quickly tensioned, ECC materials only need to be pressed and smeared for construction, and heavy formworks and supporting systems are not needed, so that the field construction operation is simple, the speed is high, and the safety risk is low; the arch back reinforcing concrete pouring of the arch springing section not only obviously improves the bearing capacity of the structure, but also has the function of weight; the cement-based material with ultrahigh toughness has very high ultimate tensile strain, obvious strain hardening characteristic and can generate a plurality of fine cracks under the action of tensile stress, and the fine cracks are favorable for inhibiting the crack development at the arch springing section. Even if cracks are generated, the speed of harmful media such as water or carbon dioxide entering the structure can be obviously reduced due to the control of the width of the cracks; the FRP net is adopted as a stress material, so that the ductility of the structure can be effectively improved, and the FRP net has no special requirement on the thickness of a protective layer due to the characteristics of the material, aging resistance, fatigue resistance and corrosion resistance; the FRP net can meet the requirements of different tensile strengths by increasing or reducing the yarn number and weaving nets with different cross sections, and has strong designability; in addition, the fiber material has soft texture and strong construction operability; sixthly, the pretension FRP net-ECC has a hoop effect and prevents the arch back reinforced concrete from generating interface through seams with the original structure; the reinforcing layer has good chemical stability and durability, the integrity of the reinforcing structure can be enhanced, and the durability of the structure can be obviously improved.
Drawings
FIG. 1 is a schematic view of a reinforcing method for a spliced section of a box-type arch bridge.
FIG. 2 is a schematic diagram showing concrete breakage and steel plate leakage at the spliced section.
FIG. 3 is a schematic illustration of an example splice reinforcement.
Fig. 4 is a view from a-a in fig. 3.
Fig. 5 is an enlarged view at B in fig. 4.
Fig. 6 is a schematic view showing the spread of the reinforcing splice.
FIG. 7 is a schematic illustration of splice reinforcement.
Fig. 8 is a schematic view of a web layout.
Fig. 9 is a schematic view of a web tensioning unit deployed.
Fig. 10 is a schematic diagram of the reinforcing method for the arch leg section of the box-type arch bridge according to the invention.
Fig. 11 is a schematic view of longitudinal and transverse slits in the arch leg of the arch leg.
FIG. 12 is an illustration of an example arch leg reinforcement.
Fig. 13 is a view from direction I-I of fig. 12.
Fig. 14 is an enlarged view at D in fig. 13.
FIG. 15 is a schematic illustration of splice reinforcement.
Fig. 16 is an arrangement schematic diagram of an FRP mesh.
Fig. 17 is an expanded view of an FRP net tensioning unit.
FIG. 18 is a development of a pre-tensioned FRP web.
Description of the main elements
In the figure: the box arch comprises a box arch splicing section 1, a box arch edge 2, an anchoring base plate 3, an anchoring screw rod 4, an ultrahigh-toughness cement-based material 5, a fiber woven mesh tensioning unit 6, a stress fiber bundle 7, a closed opening pull ring 8, a rubber rod 9, an aluminum alloy clamp 10, a box arch foot section 11, arch back reinforced concrete 12, a bottom ECC material 13, an FRP mesh tensioning unit 14, a top ECC material 15 and an interface agent 16.
The following detailed description will further illustrate the invention in conjunction with the above-described figures.
Detailed Description
Referring to fig. 1, in a preferred embodiment of the present invention, for a box-type arch bridge splicing section, the present invention provides a box-type arch bridge splicing section reinforcing method, including the following steps:
1) and determining a reinforced area according to the defect condition of the splicing section 1 of the box-type arch bridge.
2) Treating the concrete surface of the reinforced area: firstly, removing degraded concrete with the surface of which is peeled, loosened, sanded, weathered, honeycombed or corroded, and performing chiseling treatment until a new surface of aggregate is exposed, wherein the surface roughness of the new surface of the aggregate is not less than 5 mm; then, the box arch corner 2 of the reinforced area is chamfered with a chamfer radius of not less than 25 mm.
3) Determining the position of an arch rib steel bar by using a steel bar detector, marking an anchoring position, fixing an anchoring backing plate 3 on the anchoring position by using structural adhesive, drilling a hole in the anchoring backing plate 3 by using an impact drill, wherein the hole extends into concrete in a reinforced area, and fixing the anchoring backing plate 3 on the reinforced area in a manner that an anchoring screw rod 4 is inserted in the hole through threads; the operation avoids the main rib of the original structure.
4) The surface of the concrete in the reinforced area is washed clean by high pressure water, such as the powder ash or oil stain on the surface, and then the chamfer part of the box arch is filled with the ultra-high toughness cement-based material 5, wherein the ultra-high toughness cement-based material 5 is designed by taking one of cement, cement filler and small-particle-size fine aggregate as a matrix and then using short fiber as a reinforcing material. Furthermore, the mixing amount of the short fibers of the ultra-high toughness cement-based material 5 is not more than 2.5 percent of the total volume, and the ultimate tensile strain of the ultra-high toughness cement-based material is stably more than 1 percent, so that the hardened ultra-high toughness cement-based material 5 has obvious strain hardening characteristics and can generate a plurality of fine cracks under the action of tensile load.
5) The width of the fiber woven mesh tensioning unit 6 and the number of stressed fiber bundles 7 contained in each tensioning unit are reasonably selected by comprehensively considering a plurality of conditions of the length of a reinforced area, the shear strength of the anchoring screw rod 4 and the tensioning tonnage; each fiberThe fiber woven mesh needs to be treated by gluing and sand hanging. In the invention, the fiber woven mesh of each fiber woven mesh tensioning unit 6 adopts a unidirectional grid and is formed by weaving mutually vertical carbon fiber wires and glass fiber wires, wherein the carbon fiber wires are adopted in the stressed direction, and the glass fiber wires are adopted in the unstressed direction; the weaving mode mainly adopts fiber materials with high tensile strength in the main stress direction, and the fibers in the non-stress direction mainly play a role in transverse fixing. The length of the fiber woven net is measured by tests to actually measure the tension control stress (sigma)con＝0.5fr) Tension strain epsilon and inner edge size L of anchorage deviceiThe reserved length L of the anchoring endeAnd calculating the blanking length L of the fiber woven mesh according to the following formula0：
L0＝Li/(1+ε)+2Le，
In actual engineering, the tensile control stress of the fiber woven mesh is 0.5 times of the design value of the tensile strength of the fiber woven mesh in the stress direction, and the allowable deviation is +/-10%.
It should be noted that the fiber woven mesh can be used for weaving meshes with different cross-sectional areas by increasing or decreasing the number of yarns, and the mesh can be reasonably selected according to the actual situation of the reinforced structure.
6) After the ultra-high-toughness cement-based material 5 at the chamfer part reaches a certain strength, fiber woven meshes are tensioned in batches, four fiber woven mesh tensioning units 6 form a closed opening pull ring 8, each tensioning unit of one closed opening pull ring 8 is tensioned and anchored after the tensioning unit is tensioned and anchored, and tensioning construction is carried out by external and internal symmetrical tensioning during tensioning. In the present invention, the tensioning method of each fiber woven mesh tensioning unit 6 is: firstly, one end of a fiber woven mesh is wound with a rubber rod 9 and then sleeved into an aluminum alloy clamp 10, the aluminum alloy clamp 10 is fixedly connected with an anchoring backing plate 3 through an anchoring screw rod 4 and a high-strength bolt, the other end of the fiber woven mesh is wound with the rubber rod 9 and then sleeved into the aluminum alloy clamp 10, a tensioning device is used for tensioning the fiber woven mesh to a reserved hole of the anchoring backing plate 3, and then the fiber woven mesh is inserted into the anchoring screw rod 4 and fixed through the high-strength bolt.
7) Spraying a structural interface agent 16 for concrete on the surface of a reinforced area, uniformly pressing and smearing the prepared ultra-high toughness cement-based material 5 on the surface of an arch rib, smoothing and leveling, and ensuring compactness and flatness; when the ultra-high toughness cement-based material 5 is pressed and smeared, the thickness of the ultra-high toughness cement-based material 5 is not more than 25mm, the ultra-high toughness cement-based material is pressed and smeared more than time, and the pressing and smearing time interval of two adjacent layers of the ultra-high toughness cement-based material 5 is subject to initial setting of the former layer of material.
8) And (3) carrying out water spraying maintenance on the construction surface within 0.5-4 hours after the ultrahigh-toughness cement-based material 5 is pressed, smeared and polished, wherein the maintenance time is not less than 7 days, and the reinforced part is prevented from being impacted by hard objects in the period.
Aiming at the reinforcing method, the applicant applies the method in the actual bridge, and the method specifically comprises the following steps:
the upper structure of a certain bridge adopts a 6 x 70m reinforced concrete catenary box type arch bridge with a rise-to-span ratio of 1/6. No. 0 platform and No. 6 platform in the lower structure are grouted rubble U-shaped bridge abutments, and No. 1-No. 5 piers are reinforced concrete gravity type piers. The bridge deck is paved by concrete bridge deck, and 14 special-shaped steel expansion joints are arranged in the full bridge. The bridge has the main technical standards that:
1. full width of the bridge deck: 12.00m ═ 1.50m (sidewalk + guardrail) +9.00m (driveway) +1.50m (sidewalk + guardrail);
2. designing the load grade: steam-20 grade, hang-100 grade, crowd 350kg/m2(JTJ 021-89);
3. bridge longitudinal slope: bidirectional 1.9%.
According to a detection report provided by a detection unit, a plurality of defects such as damage, steel plate leakage and the like exist at the position of the splicing section 1 of the arch box, and a typical defect photo is shown in figure 2.
According to the existing disease conditions, the applicant adopts the box-type arch bridge splicing section 1 reinforcing method of the invention within the range of 11.50m of the bridge box arch splicing section according to the basic principles of safety, applicability, reliable technology, durability and economy and reasonability, the reinforcing diagram is shown in detail in figures 3-9, and the concrete implementation steps of the reinforcing method are as follows:
1) and determining a reinforced area according to the defect condition of the splicing section 1 of the box-type arch bridge.
2) Treating the concrete surface of the reinforced area: firstly, removing degraded concrete with the surface of which is peeled, loosened, sanded, weathered, honeycombed or corroded, and performing chiseling treatment until a new surface of aggregate is exposed, wherein the surface roughness of the new surface of the aggregate is not less than 5 mm; next, the box arch corner 2 in the reinforced area was chamfered with a chamfer radius of 25 mm.
3) Determining the position of an arch rib steel bar by using a steel bar detector, marking the position of an anchoring device, fixing an anchoring backing plate 3 on the anchoring position by using structural adhesive, drilling a hole in the anchoring backing plate 3 by using an impact drill, wherein the hole extends into concrete in a reinforced area, and fixing the anchoring backing plate 3 on the reinforced area in a manner that an anchoring screw rod 4 is inserted in the hole in a threaded manner; the operation avoids the main rib of the original structure. Specifically, the anchoring device on the top (bottom) surface of the reinforcing area is 15cm away from the side surface of the arch rib, and the side anchoring device is 2cm away from the top (bottom) surface of the arch rib. And (3) drilling holes at the screw rod position by using a percussion drill, wherein the hole diameter is 18mm, the depth of the implanted arch rib is 15cm, and the reinforcing steel bars are avoided. The thickness of the anchoring backing plate 3 is 10mm, and the anchoring backing plate 3 is fixed by structural adhesive.
4) Washing the powder ash or oil stain on the surface of the concrete in the reinforced area with high pressure water, filling the chamfer part of the arch of the box with ultra-high toughness cement-based material 5, wherein the ultra-high toughness cement-based material 5 is designed by taking one of cement, cement filler and small-particle-size fine aggregate as a matrix and then using short fiber as a reinforcing material, wherein the mixing amount of the short fiber is not more than 2.5 percent of the total volume of the ultra-high toughness cement-based material 5, and the ultimate tensile strain of the ultra-high toughness cement-based material is stably over 1 percent, so that the hardened ultra-high toughness cement-based material 5 has remarkable strain hardening characteristics and can generate a plurality of fine cracks under the action of tensile load. In the present embodiment, the performance index of the ultra-high toughness cement-based material 5 doped with short fibers is shown in table 2.
TABLE 2 ultra high toughness Cement-based Material 5 blend short fiber Performance index
Length (mm) Diameter (μm) Tensile strength (Mpa) Elongation (%) Tensile modulus of elasticity (GPa) Density (g/cm)3)
12 39 1620 7 42.8 1.3
5) The width of the fiber woven mesh tensioning unit 6 and the number of stressed fiber bundles 7 contained in each tensioning unit are reasonably selected by comprehensively considering a plurality of conditions of the length of a reinforced area, the shear strength of the anchoring screw rod 4 and the tensioning tonnage; each woven fiber mesh requires a viscose sanding process. In this example, the fiber mesh grid is woven by mutually perpendicular carbon fiber filaments/glass fiber filaments, wherein the carbon fiber filaments are adopted in the stress direction, the glass fiber filaments are adopted in the non-stress direction, the width of the carbon fiber filaments in the stress direction is 5mm and the distance between the carbon fiber filaments is 17mm, the width of the glass fiber filaments in the non-stress direction is 2mm and the distance between the glass fiber filaments is 20mm, and the designed tensile strength of the carbon fiber in the stress direction is 1600 MPa.
In this case, the woven fiber net is cut into a strip-shaped fiber net with the same width by blanking in a factory in advance according to the size of the reinforcing area, and the length of the woven fiber net is measured by a test to measure the tension control stress (sigma)con＝0.5fr) Tension strain epsilon and inner edge size L of anchorage deviceiThe reserved length L of the anchoring endeAnd calculating the blanking length L of the fiber woven mesh according to the following formula0：
L0＝Li/(1+ε)+2Le，
Wherein, the blanking length of the bottom (top) surface fiber net is as follows:
L0＝(20+9300+20)÷(1+0.5×1600÷240000)+2×4/3×3.14×12＝9410mm
the blanking length of the side fiber net is as follows:
L0＝(150+1300+150)÷(1+0.5×1600÷240000)+2×4/3×3.14×12＝1695mm
6) after the ultra-high-toughness cement-based material 5 at the chamfer part reaches a certain strength, the fiber woven mesh is stretched, four fiber woven mesh stretching units 6 form a closed stretching ring 8 for stretching, one end of the fiber woven mesh is firstly sleeved into an anchoring end clamp 10 and is fixed by an M16 full-thread screw rod, the other end of the fiber woven mesh is sleeved into the stretching end clamp 10, then the fiber woven mesh is sequentially stretched and fixed along the annular direction, after all the four fiber woven mesh stretching units 6 forming a closed ring are stretched and anchored, the next closed stretching ring 8 can be stretched, and the stretching construction is carried out by external and internal batch symmetric stretching.
7) Spraying a structural interface agent 16 for concrete on the surface of a reinforced area, uniformly pressing and smearing the prepared ultra-high toughness cement-based material 5 on the surface of an arch rib, smoothing and leveling, and ensuring compactness and flatness; in this example, two layers of ultra-high toughness cementitious material 5 are pressed, wherein the first layer of ultra-high toughness cementitious material 5 is pressed to a thickness of 20mm and the second layer of ultra-high toughness cementitious material is pressed to a thickness of 510mm before initial setting.
8) And (3) spraying water to the construction surface for maintenance within 0.5-4 hours after the super-high toughness cement-based material 5 is pressed, smeared and polished, wherein the maintenance time is 14 days, and the reinforced part is prevented from being impacted by hard objects during the maintenance time.
Referring to fig. 10, for the box-type arch bridge arch foot section 11, the invention further provides a method for reinforcing the box-type arch bridge arch foot section 11, which includes the following steps:
1) and determining a reinforced area according to the disease condition of the arch leg section 11 of the box arch.
2) Treating the concrete surface of the reinforced area: firstly, removing degraded concrete with the surface of the concrete stripped, loosened, sanded, weathered, honeycombed or corroded, roughening, exposing a new surface of an aggregate, washing the new surface of the aggregate by high-pressure water, and grouting cracks with the width of more than 0.15mm, wherein the roughness of the new surface of the aggregate is not less than 6 mm.
3) The position of the arch rib steel bar is determined by using a steel bar detector, then steel bar planting hole position lofting, drilling and hole cleaning are carried out, the accuracy of the hole position and the effective depth of the drilling are ensured, and the operation avoids the main steel bar of the original structure.
4) And (4) planting the steel bars, determining the anchoring depth strictly according to the design requirement, and selecting proper structural adhesive through a field drawing test.
5) And (5) carrying out template installation and reinforcement mesh binding on the arch backs in the reinforcement areas.
6) The arch back reinforced concrete 12 is poured, the reinforced concrete adopts a construction process of sectional cast-in-place, and roughening treatment is carried out on the surface of the concrete after pouring is finished so as to reduce the influence of concrete shrinkage.
7) After the strength of the arch back reinforced concrete 12 reaches 95% of the design strength, the anchoring base plate 3 is fixed by using structural adhesive, the impact drill is used for drilling holes in the positions of the anchoring screw rods 4, the reinforcing steel bars are avoided during drilling, and the reinforcing area of the arch foot section 11 is cleaned by using high-pressure water after the drilling is finished.
8) Spraying a structural interface agent 16 for concrete on the surface of the reinforced area, uniformly pressing and smearing the prepared bottom ECC material 13 on the surface of the reinforced area, and chamfering edges and corners 2 around the arch leg section 11 in the pressing and smearing process, wherein the radius of the chamfer is not less than 25mm, and the thickness of the pressed and smeared bottom ECC material 13 is not less than the thickness of the FRP net and not more than 20 mm. In the invention, the ECC material is designed by taking cement or cement and filler or small-particle-size fine aggregate as a matrix and short fiber as a reinforcing material, wherein the fiber doping amount is not more than 2.5 percent of the total volume of the ECC material, the ultimate tensile strain of the ECC material is stabilized to be more than 1 percent, so that the hardened ECC material has obvious strain hardening characteristics, and a plurality of fine cracks can be generated under the action of tensile load.
9) Comprehensively considering a plurality of conditions of the area of the reinforced area, the shear strength of the anchoring screw rod 4 and the tensioning tonnage, reasonably selecting the width of the FRP net tensioning unit 14 and each tensioning unitThe number of the stressed fiber bundles contained in the pulling unit is 7; and (3) gluing and sand hanging treatment is needed before the FRP net is tensioned. In the invention, the FRP net adopts a unidirectional grid which is formed by weaving mutually vertical carbon fiber wires/glass fiber wires, wherein the carbon fiber wires are adopted in the stress direction, the glass fiber wires are adopted in the non-stress direction, the weaving mode mainly ensures that the fiber material with high tensile strength is adopted in the main stress direction, and the fiber in the non-stress direction mainly plays a role in transverse fixing. The method for calculating the blanking length of the FRP net is the same as the method for calculating the blanking length of the fiber woven net, and particularly, the blanking length of the FRP net is actually measured by tests to control the tensile strain epsilon of stress and the size L of the inner edge of an anchorage deviceiThe reserved length L of the anchoring endeAnd calculating the blanking length L of the FRP net according to the following formula0：
L0＝Li/(1+ε)+2Le，
In actual engineering, the tensile control stress of the FRP net is 0.5 times of the design value of the tensile strength of the FRP net in the stress direction, and the allowable deviation is +/-10%.
It should be noted that the FRP mesh can be used to weave meshes of different cross-sectional areas by increasing or decreasing the number of yarns, and is selected reasonably according to the actual situation of the reinforced structure.
10) Tensioning FRP net tensioning units 14 in batches, wherein four FRP net tensioning units 14 (top tensioning units, bottom tensioning units and two side tensioning units) form a closed opening pulling ring 8, each FRP net tensioning unit 14 of one closed opening pulling ring 8 is tensioned and anchored after the next closed opening pulling ring 8 is tensioned, and during tensioning, tensioning construction is performed symmetrically from outside to inside; specifically, the tensioning method of each tensioning unit comprises the following steps: firstly, winding a rubber rod 9 at one end of an FRP net and then sleeving the FRP net into an aluminum alloy clamp 10, fixedly connecting the aluminum alloy clamp 10 with an anchoring backing plate 3 by using an anchoring screw rod 4 and a high-strength bolt, winding the rubber rod 9 at the other end of the FRP net and then sleeving the FRP net into the aluminum alloy clamp 10, tensioning the FRP net to a preformed hole of the anchoring backing plate 3 by using tensioning equipment, inserting the anchoring screw rod 4 and fixing the FRP net by using the high-strength bolt.
11) And uniformly pressing and smearing the prepared top layer ECC material 15 on the surface of the arch leg section 11, smoothing and leveling to ensure compactness and flatness, wherein the pressing and smearing time interval of the top layer ECC material 15 is based on the initial setting of the bottom layer ECC material 13.
12) And (3) performing water spraying maintenance on the construction surface within 0.5-4 hours after the ECC material is pressed and smeared, wherein the maintenance time is not less than 7 days, and the reinforced part is prevented from being impacted by hard objects during the maintenance time.
Aiming at the method, the applicant also applies to the actual bridge, and the specific steps are as follows:
the bridge in Xijiang province, Teng county, is located near Longmu temple about 1km downstream of Baisha aqueduct in Teng county, and the developing area of south China Tu river east is connected with the starting point of Jinmeng highway north. The Xijiang bridge is built in 2003, the main span is an 11-hole equal span arch bridge, the net span is 90m, the arch axis coefficient m is 1.543m, and the rise-span ratio f0/l 01/6. The main arch ring of the upper structure adopts a reinforced concrete double-rib box arch; the lower bridge abutment adopts a combined bridge abutment, the pier is a gravity pier, and the pier adopts open cut to enlarge the foundation; the bridge deck in the bridge deck system is paved by adopting a cement concrete pavement layer; a reinforced concrete anti-collision guardrail is arranged between the sidewalk and the traffic lane, and the sidewalk guardrail is a steel guardrail; the bridge deck expansion joints adopt rubber expansion joints, 12 full bridges are arranged in total and are respectively arranged on the bridge deck at the tops of all the piers.
The bridge has the main technical standards that:
1. full width of the bridge deck: 0.5m (sidewalk guardrail) +2.75m (sidewalk) +0.5m (anti-collision wall) +9.0m (roadway) +0.5m (anti-collision wall) +2.75m (sidewalk) +0.5m (sidewalk guardrail);
2. designing the load grade: steam-20 grade, hang-100 grade, crowd 350kg/m2(JTJ 021-89);
3. bridge floor cross slope: 1.5 percent.
In 2013, in 4 months, a bridge management and maintenance unit finds that a bridge has serious diseases in the inspection, a related detection unit is entrusted to perform periodic inspection, the technical condition grade of the bridge is evaluated to be 4 according to the inspection result, and the technical condition is described that main components have large defects, so that the service function of the bridge is seriously influenced; or the bearing capacity is influenced, and normal use cannot be guaranteed.
According to a detection report provided by a detection unit, a plurality of defects such as longitudinal cracks, transverse cracks and the like exist at the arch springing section 11 of the box arch, and a typical defect photo is shown in fig. 11.
According to the existing damage condition of the bridge, the bridge is designed to be reinforced, and the automobile load grade is improved. The applicant team adopts a box-type arch bridge arch foot section 11 reinforcement method for the three small span ranges of the bridge box arch foot section 11 according to basic principles of safety, applicability, reliable technology, durability and economy and reasonability, the reinforcement method is shown in detail in figures 12-18, and the concrete implementation steps of the reinforcement method are as follows:
1) and determining a reinforced area according to the disease condition of the arch leg section 11 of the box arch.
2) Treating the concrete surface of the reinforced area: firstly, removing degraded concrete with the surface of the concrete stripped, loosened, sanded, weathered, honeycombed or corroded, roughening, exposing a new surface of an aggregate, washing the new surface of the aggregate by high-pressure water, and grouting cracks with the width of more than 0.15mm, wherein the roughness of the new surface of the aggregate is not less than 6 mm.
3) The position of the arch rib steel bar is determined by using a steel bar detector, then steel bar planting hole position lofting, drilling and hole cleaning are carried out, the accuracy of the hole position and the effective depth of the drilling are ensured, and the operation avoids the main steel bar of the original structure. In the embodiment, the diameter of the drilled hole is 16mm, the arch rib is implanted for 15cm, and the bar-planting glue is poured into the drilled hole, so that the construction process and the material property of the bar-planting glue meet the requirements of relevant specifications;
4) and (4) planting the steel bars, determining the anchoring depth strictly according to the design requirement, and selecting proper structural adhesive through a field drawing test.
5) And (5) carrying out template installation and reinforcement mesh binding on the arch backs in the reinforcement areas.
6) And pouring the arch back reinforced concrete 12, wherein the reinforced concrete adopts a construction process of sectional cast-in-place, and roughening treatment is carried out on the surface of the concrete after pouring is finished.
7) After the strength of the arch back reinforced concrete 12 reaches 95% of the designed strength, the anchoring base plate 3 is fixed by using structural adhesive, a percussion drill is used for drilling holes at the position of the anchoring screw rod 4, the reinforcing steel bars are avoided during drilling, and after drilling is completed, the powder dust or oil stains and the like in the reinforcing area of the arch foot section 11 are cleaned by using high-pressure water. In this example, the specific operation is: marking the position of an anchoring device on the arch springing section 11, wherein the top (bottom) surface anchoring device is 30cm away from the side surface of the arch rib, and the side surface anchoring device is 30cm away from the top (bottom) surface of the arch rib; drilling holes at the screw rod position by using a percussion drill, wherein the hole diameter is 18mm, implanting 15cm of arch ribs, and paying attention to avoid reinforcing steel bars; the thickness of the anchoring backing plate 3 is 10mm, and the anchoring backing plate 3 is fixed by structural adhesive.
8) Spraying a structural interface agent 16 for concrete on the surface of the reinforced area, uniformly pressing and smearing the prepared bottom ECC material 13 on the surface of the reinforced area, and chamfering edges and corners 2 around the arch leg section 11 in the pressing and smearing process, wherein the radius of the chamfer is not less than 25mm, and the thickness of the pressed and smeared bottom ECC material 13 is 20 mm. In the invention, the ECC material is designed by taking cement or cement and filler or small-particle-size fine aggregate as a matrix and short fiber as a reinforcing material, wherein the fiber doping amount is not more than 2.5 percent of the total volume of the ECC material, the ultimate tensile strain of the ECC material is stabilized to be more than 1 percent, so that the hardened ECC material has obvious strain hardening characteristics, and a plurality of fine cracks can be generated under the action of tensile load.
9) Comprehensively considering a plurality of conditions of the area of a reinforced area, the shear strength of the anchoring screw rod 4 and the tensioning tonnage, and reasonably selecting the width of the FRP net tensioning unit 14 and the number of the stressed fiber bundles 7 contained in each tensioning unit; and (3) gluing and sand hanging treatment is needed before the FRP net is tensioned. In the invention, the FRP net adopts a unidirectional grid which is formed by weaving mutually vertical carbon fiber wires/glass fiber wires, wherein the carbon fiber wires are adopted in the stress direction, the glass fiber wires are adopted in the non-stress direction, the weaving mode mainly ensures that the fiber material with high tensile strength is adopted in the main stress direction, and the fiber in the non-stress direction mainly plays a role in transverse fixing. Specifically, the width of the carbon fiber yarns in the stress direction of the FRP net is 5mm, and the distance between the carbon fiber yarns is 20 mm; the width of the glass fiber yarns in the non-stress direction is 2mm, and the distance between the glass fiber yarns is 20 mm; the design tensile strength of the carbon fiber in the stress direction is 1600 MPa.
The FRP net is blanked in a factory in advance according to the size of a reinforced area and cut into strip-shaped FRP nets with the same width, and the blanking length of the FRP net is actually measured by tests to control the tension stress (sigma)con＝0.5fr) Tension strain epsilon and inner edge size L of anchorage deviceiThe reserved length L of the anchoring endeAnd calculating the blanking length L of the FRP net according to the following formula0：
L0＝Li/(1+ε)+2Le，
Bottom (top) surface FRP net blanking length:
L0＝(30+2340+30)÷(1+0.5×1600÷240000)+2×4/3×3.14×20＝2660mm
side FRP net blanking length:
L0＝(30+2200+30)÷(1+0.5×1600÷240000)+2×4/3×3.14×20＝2420mm。
10) tensioning FRP net tensioning units 14 in batches, wherein four FRP net tensioning units 14 (namely tensioning units on the top surface, the bottom surface and two side surfaces of a reinforced area) form a closed opening pull ring 8, and each FRP net tensioning unit 14 of one closed opening pull ring 8 is tensioned and anchored after the whole tensioning and anchoring, and is subjected to tensioning construction by external and internal symmetry during tensioning; specifically, after the FRP net is cut in a factory, rubber rods 9 with the diameter of 20mm are wound at two ends of the FRP net to ensure firmness and reliability, and the FRP net needs to be subjected to viscose sand hanging treatment before being tensioned; the four FRP net tensioning units 14 form a closed ring for tensioning, one end of the FRP net is sleeved into the anchoring end clamp 10 and fixed by an M16 full-thread screw, the other end of the FRP net is sleeved into the tensioning end clamp 10, then the FRP net is sequentially tensioned and fixed along the ring direction, so that the next closed ring can be tensioned after all the four FRP net tensioning units 14 forming the closed ring are tensioned and anchored, and the tensioning is performed by external and internal batch symmetric tensioning construction.
11) The prepared top layer ECC material 15 is uniformly pressed on the surface of the arch leg section 11, and is smoothed and leveled to ensure compactness and flatness, the pressing time interval of the top layer ECC material 15 is based on the initial setting of the bottom layer ECC material 13, and in this example, the pressing thickness of the top layer ECC material 15 is 30 mm.
12) And (3) carrying out water spraying maintenance on the construction surface within 0.5-4 hours after the ECC material is pressed and smeared, wherein the maintenance time is 14 days, and the reinforced part is prevented from being impacted by hard objects in the period.
The above description is intended to describe in detail the preferred embodiments of the present invention, but the embodiments are not intended to limit the scope of the claims of the present invention, and all equivalent changes and modifications made within the technical spirit of the present invention should fall within the scope of the claims of the present invention.

Claims (8)

1. A box arch bridge splicing section reinforcing method is characterized by comprising the following steps:
1) determining a reinforced area according to the defect condition of the splicing section of the box-type arch bridge;
2) treating the concrete surface of the reinforced area: firstly, removing degraded concrete with the surface of which is peeled, loosened, sanded, weathered, honeycombed or corroded, and performing chiseling treatment until a new surface of aggregate is exposed, wherein the surface roughness of the new surface of the aggregate is not less than 5 mm; then, chamfering the box arch corner of the reinforced area, wherein the chamfer radius is not less than 25 mm;
3) determining the position of an arch rib steel bar by using a steel bar detector, marking an anchoring position, fixing an anchoring base plate on the anchoring position by using structural adhesive, drilling a hole in the anchoring base plate by using an impact drill, wherein the hole extends into concrete in a reinforced area, and the anchoring base plate is fixed on the reinforced area in a mode that an anchoring screw rod is inserted into the hole through threads; the operation avoids the main rib of the original structure;
4) washing the surface of the concrete in the reinforced area by using high-pressure water, filling the chamfer part of the arch of the box with an ultrahigh-toughness cement-based material, wherein the ultrahigh-toughness cement-based material is designed by taking one of cement, cement filler and small-particle-size fine aggregate as a matrix and then using short fibers as a reinforcing material;
5) the width of the fiber woven mesh tensioning unit and the number of stressed fiber bundles contained in each tensioning unit are reasonably selected by comprehensively considering a plurality of conditions of the length of a reinforced area, the shear strength of an anchoring screw and the tensioning tonnage; each fiber woven mesh needs to be subjected to viscose sand hanging treatment;
6) tensioning fiber woven nets in batches after the ultra-high-toughness cement-based material at the chamfer part reaches a certain strength, wherein four fiber woven net tensioning units form a closed tensioning ring, each tensioning unit of one closed tensioning ring is tensioned and anchored completely and then tensioned and tensioned with the next closed tensioning ring, and during tensioning, the tensioning is performed by external and internal symmetrical tensioning construction; the tensioning method of each fiber woven net tensioning unit comprises the following steps: firstly, winding a rubber rod at one end of a fiber woven mesh and then sleeving the fiber woven mesh into an aluminum alloy clamp, fixedly connecting the aluminum alloy clamp with an anchoring backing plate by using an anchoring screw rod and a high-strength bolt, winding the rubber rod at the other end of the fiber woven mesh and then sleeving the fiber woven mesh into the aluminum alloy clamp, tensioning the fiber woven mesh to a preformed hole of the anchoring backing plate by using tensioning equipment, inserting the fiber woven mesh into the anchoring screw rod and fixing the fiber woven mesh with the high-strength bolt;
7) spraying a structural interface agent for concrete on the surface of a reinforced area, uniformly pressing and smearing the prepared ultra-high toughness cement-based material on the surface of an arch rib, smoothing and leveling, and ensuring compactness and flatness; when the ultra-high toughness cement-based material is pressed and smeared, the pressing and smearing thickness of the ultra-high toughness cement-based material is not more than 25mm, the pressing and smearing thickness is more than time-division pressing and smearing, and the pressing and smearing time interval of two adjacent layers of the ultra-high toughness cement-based material is determined by initial setting of the former layer of material;
8) the water spraying maintenance is carried out on the construction surface within 0.5-4 hours after the ultra-high toughness cement-based material is pressed, smeared and polished, the maintenance time is not less than 7 days, and the reinforced part is prevented from being impacted by hard objects in the period.
2. The box-type arch bridge splicing section reinforcing method as set forth in claim 1, wherein: the fiber woven mesh of each fiber woven mesh tensioning unit is a unidirectional mesh and is formed by weaving mutually vertical carbon fiber wires and glass fiber wires, wherein the carbon fiber wires are adopted in the stressed direction, and the glass fiber wires are adopted in the unstressed direction; the blanking length of the fiber woven mesh is measured by tests to control the tensile strain epsilon of the stress and the size L of the inner edge of the anchorage deviceiThe reserved length L of the anchoring endeAnd calculating the blanking length L of the fiber woven mesh according to the following formula0：
L0＝Li/(1+ε)+2Le，
In actual engineering, the tensile control stress of the fiber woven mesh is 0.5 times of the design value of the tensile strength of the fiber woven mesh in the stress direction, and the allowable deviation is +/-10%.
3. The box-type arch bridge splicing section reinforcing method as set forth in claim 1, wherein: the mixing amount of the short fiber of the ultra-high toughness cement-based material is not more than 2.5 percent of the total volume, and the ultimate tensile strain of the ultra-high toughness cement-based material can stably reach more than 1 percent.
4. A box arch bridge arch foot section reinforcing method is characterized by comprising the following steps:
1) determining a reinforced area according to the defect condition of the arch leg of the box arch;
2) treating the concrete surface of the reinforced area: firstly, removing degraded concrete with the surface of the concrete stripped, loosened, sanded, weathered, honeycombed or corroded, roughening, exposing a new surface of an aggregate, washing the new surface of the aggregate by high-pressure water, and grouting cracks with the width of more than 0.15mm, wherein the roughness of the new surface of the aggregate is not less than 6 mm;
3) determining the position of an arch rib steel bar by using a steel bar detector, then performing steel bar planting hole position lofting, drilling and hole cleaning treatment to ensure the accuracy of the hole position and the effective depth of the drilling, and avoiding the main steel bar of the original structure by the operation;
4) planting bars, determining the anchoring depth strictly according to the design requirements, and selecting proper structural adhesive through a field drawing test;
5) installing a template and binding a reinforcing mesh on the arch back of the reinforced area;
6) pouring the arch back reinforced concrete, wherein the reinforced concrete adopts a construction process of sectional cast-in-place, and roughening treatment is carried out on the surface of the concrete after pouring;
7) after the strength of the arch back reinforced concrete reaches 95% of the design strength, fixing the anchoring base plate by using structural adhesive, drilling at the position of the anchoring screw by using an impact drill, avoiding a reinforcing steel bar during drilling, and cleaning the reinforcing area of the arch foot section by using high-pressure water after the drilling is finished;
8) spraying a structural interface agent for concrete on the surface of the reinforced area, uniformly pressing and smearing the prepared bottom ECC on the surface of the reinforced area, and chamfering edges and corners around the arch leg section in the pressing and smearing process, wherein the radius of the chamfer is not less than 25 mm;
9) comprehensively considering a plurality of conditions of the area of a reinforced area, the shear strength of an anchoring screw and the tensioning tonnage, and reasonably selecting the width of the FRP net tensioning unit and the number of stressed fiber bundles contained in each tensioning unit; carrying out viscose sand hanging treatment before tensioning the FRP net;
10) tensioning FRP net tensioning units in batches, wherein the four FRP net tensioning units form a closed tensioning ring, each FRP net tensioning unit of one closed tensioning ring is tensioned and anchored after the tensioning unit is tensioned and anchored, and tensioning construction is carried out symmetrically from outside to inside during tensioning;
11) uniformly pressing and smearing the prepared top ECC material on the surface of the arch springing section, smoothing and leveling to ensure compactness and flatness, wherein the pressing and smearing time interval of the top ECC material is subject to initial setting of the bottom ECC material;
12) and (3) performing water spraying maintenance on the construction surface within 0.5-4 hours after the ECC material is pressed and smeared, wherein the maintenance time is not less than 7 days, and the reinforced part is prevented from being impacted by hard objects during the maintenance time.
5. The box-type arch bridge arch foot section reinforcing method according to claim 4, wherein: in step 10), the tensioning method of each tensioning unit is as follows: firstly, winding a rubber rod at one end of an FRP net and then sleeving the FRP net into an aluminum alloy clamp, fixedly connecting the aluminum alloy clamp with an anchoring backing plate by using an anchoring screw rod and a high-strength bolt, winding the rubber rod at the other end of the FRP net and then sleeving the FRP net into the aluminum alloy clamp, tensioning the FRP net to a preformed hole of the anchoring backing plate by using tensioning equipment, inserting the anchoring screw rod and fixing the FRP net by using the high-strength bolt.
6. The box-type arch bridge arch foot section reinforcing method according to claim 4, wherein: the FRP net adopts a unidirectional grid which is formed by weaving mutually vertical carbon fiber wires/glass fiber wires, wherein the carbon fiber wires are adopted in the stress direction, the glass fiber wires are adopted in the non-stress direction, the blanking length of the FRP net is measured and tensioned through tests to control the tensile strain epsilon and the size L of the inner edge of an anchorage deviceiThe reserved length L of the anchoring endeAnd calculating the blanking length L of the FRP net according to the following formula0：
L0＝Li/(1+ε)+2Le，
In actual engineering, the tensile control stress of the FRP net is 0.5 times of the design value of the tensile strength of the FRP net in the stress direction, and the allowable deviation is +/-10%.
7. The box-type arch bridge arch foot section reinforcing method according to claim 4, wherein: the thickness of the bottom ECC material pressed and smeared is not less than that of the FRP net and not more than 20 mm.
8. The box-type arch bridge arch foot section reinforcing method according to claim 4, wherein: the bottom ECC material is designed by taking cement or cement and filler or small-particle-size fine aggregate as a matrix and short fiber as a reinforcing material, wherein the fiber doping amount does not exceed 2.5 percent of the total volume of the bottom ECC material, and the ultimate tensile strain of the bottom ECC material is stabilized to be more than 1 percent.
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