Single-tower cable-stayed urban viaduct and construction method

Abstract

The present invention discloses a single-tower cable-stayed urban viaduct and a construction method, and belongs to the technical field of viaducts. The viaduct includes: a single-column bridge tower, which is provided with a cable anchoring area; a cable-stayed cable, which is arranged in a central double-cable fan-shaped shape, the cable-stayed cable includes a core, an outer cladding, a spiral line is provided on the outer surface of the outer cladding, and a circular pit is provided, the pit avoids the spiral line, and the pit includes at least two pits with different diameters; a main beam, the other end of the cable-stayed cable is anchored and connected to the main beam, the main beam is a single-box five-chamber prestressed concrete box beam, a cross beam is provided at a predetermined interval in the middle span section, and the spacing of the cross beams is the same as the spacing of the cable-stayed cables. The current technical problem of large vibration amplitude of the cable-stayed cable dry cable is solved.

Description

Technical Field

[0001] The invention relates to the technical field of viaducts, and in particular to a single-tower cable-stayed urban viaduct and a construction method. Background Art

[0002] A viaduct, also known as an elevated road, generally refers to a bridge that is much higher than the road surface and spans a series of obstacles. Specifically, a viaduct is a three-dimensional bridge made of materials such as steel bars and cement for vehicles to travel on. It is usually built in cities to avoid traffic congestion or to cross terrain obstacles such as valleys and rivers.

[0003] According to the different obstacles crossed, viaducts can be divided into general viaducts, viaducts across railway lines, viaducts across rivers, etc. Since it is difficult to set up support columns for viaducts across rivers in water, cable-stayed bridges are used to cross rivers. The cables in cable-stayed bridges bear the load of the bridge, so during the design and construction process, it is necessary to focus on the life of the cables, and during the maintenance process, it is also necessary to pay extra attention to the condition of the cables. When it rains, rainwater is easily hung on the surface of the cables, forming water lines, changing the shape of the cables, and generating wind-rain vibration. The formation of water lines can be reduced by setting spiral lines and opening pits on the surface of the inclined cables. However, after the pits are opened, the roughness of the surface of the inclined cables will be affected, resulting in a decrease in the wind speed corresponding to the critical Reynolds number of the inclined cables. Under common wind speeds, a large amount of dry cable galloping will occur, causing fatigue or even damage to the ends of the inclined cables. Summary of the invention

[0004] The main purpose of the invention is to provide a single-tower cable-stayed urban viaduct and a construction method, aiming to reduce the wind-rain induced vibration degree of the cable-stayed bridge.

[0005] To achieve the above object, the single-tower cable-stayed urban viaduct proposed in the present invention comprises:

[0006] A single-column bridge tower is provided with a cable anchoring area, wherein the cable anchoring area is provided with a "well"-shaped prestressed steel bar;

[0007] The inclined cable is arranged in a fan-shaped manner with a central double cable surface, and viscous shear dampers and vibration-damping rubber rings are installed at both ends. One end of the inclined cable is anchored and connected to the cable anchoring area. The inclined cable includes a core and an outer layer. A spiral line and a circular pit are arranged on the outer surface of the outer layer. The pit avoids the spiral line. The pit includes at least two pits with different diameters. The depth of the pit is a, 0.5mm≤a≤1mm;

[0008] The other end of the inclined cable is anchored and connected to the main beam. The main beam is a single-box five-chamber prestressed concrete box beam. A cross beam is arranged at a predetermined interval in the middle span, and the spacing between the cross beams is the same as the spacing between the inclined cables.

[0009] Optionally, in one embodiment of the present invention, along the axial direction of the inclined cable, the cross-section of the pit has a first hypotenuse and a second hypotenuse, the first hypotenuse is close to the high end of the inclined cable, and the second hypotenuse is close to the low end of the inclined cable, the angle between the inclined cable and the ground is b, the angle between the second hypotenuse and the ground is c, 0°<c<b, and the angle between the first hypotenuse and the high end surface of the inclined cable is d, d<90°+b.

[0010] Optionally, in one embodiment of the present invention, the viaduct is a concrete bridge, and the concrete comprises at least the following raw materials:

[0011] Portland cement, wherein the content of tricalcium aluminate in the Portland cement is ≤8wt%, the cement fineness is ≤350㎡ / kg, and the free calcium oxide is ≤1.5wt%;

[0012] Aggregates, including fine aggregate and coarse aggregate, wherein the fine aggregate is medium-coarse river sand with a weight loss rate of less than 5%, and the coarse aggregate has a weight loss rate of less than 10%;

[0013] The admixture comprises at least fly ash, ground slag and silica fume, wherein the calcium oxide content in the fly ash is ≤10wt%, the ground slag is ground blast furnace water-quenched slag, and its Blaine surface area is ≥35㎡ / kg and ≤450㎡ / kg, the silicon dioxide content in the silica fume is ≥85wt%, and the Blaine surface area is ≥18000㎡ / kg.

[0014] Optionally, in one embodiment of the present invention, the concrete is poured on a portion of a steel member, and the steel member at least includes a steel plate, a main steel member, and an auxiliary steel member.

[0015] The outer surface of the steel plate is coated with an inorganic zinc silicate primer protective layer;

[0016] The main steel component is coated with a layer of epoxy zinc-rich layer, two layers of epoxy micaceous iron intermediate layers and two layers of fluorocarbon layers in sequence from the inside to the outside;

[0017] The auxiliary steel member is coated with a layer of epoxy high build paint and two layers of fluorocarbon in sequence from the inside to the outside.

[0018] Optionally, in one embodiment of the present invention, the stay cable comprises:

[0019] A core, which is a zinc-aluminum alloy coated parallel steel wire rope;

[0020] A cable sheath, which is coated on the outer periphery of the zinc-aluminum alloy coated parallel steel wire cable, and the cable sheath is formed by hot extrusion of carbon black polyethylene;

[0021] A conduit, wherein the core and the cable sleeve are located inside the conduit, and the interior of the conduit is filled with foamed polyurethane;

[0022] The outer layer is sleeved on the outer circumference of the catheter, and the outer layer includes at least two high-density polyethylene layers, and the outermost high-density polyethylene layer is provided with the spiral line and the pit.

[0023] The present invention also proposes a construction method for a single-tower cable-stayed urban viaduct, comprising:

[0024] S1. Test the concrete mix ratio before construction to check the fluidity, workability, slow setting and early strength of the concrete;

[0025] S2. Use climbing formwork to construct the tower column. During the construction process, the pouring height of each section is ≤6m, and the shape of the tower column is always observed during the construction process;

[0026] S3. After the tower column construction is completed, prestressing is carried out after the concrete strength reaches 90% of the design strength, and the tensioning force and elongation are controlled during the tensioning process;

[0027] S4. After the tensioning is completed, the joint between the straight anchor concrete and the poured concrete is sealed;

[0028] S5. Roughen, degrease and clean the construction joints of each part of the single-column bridge tower.

[0029] Furthermore, in step S3, the tensioning includes longitudinal and transverse tensioning, the longitudinal prestressing of the concrete is tensioned for at least 168 hours, the longitudinal prestressing steel strands remain symmetrical in the cross section of the box girder, and the two ends of the longitudinal steel strands are tensioned synchronously in the order of bottom plate strand-top plate strand.

[0030] Furthermore, in step S3, when tensioning to 15% of the design tonnage, the load is held for 3 minutes to measure the elongation. After tensioning to the design tonnage, the load is held for 3 minutes to measure the elongation Δ1. The actual elongation Δ=Δ1 / 0.85-б, where б is the clip retraction value. After measuring Δ1, the oil is returned, and then the elongation Δ2 on both sides must satisfy Δ-Δ2≤7mm. If Δ-Δ2>7mm, it is determined that the entire wire is slipped and needs to be processed.

[0031] Furthermore, in step S4, after the prestressed steel strands are tensioned, the excess steel strands are cut and grouting is completed within 24 hours. Before grouting, impurities in the pipeline are removed and grouting is completed using a vacuum-assisted grouting method.

[0032] Furthermore, in step S2, after the construction of the lower tower column of the single-column bridge tower is completed, a tower side bracket is constructed on the top of the lower tower column, and the bracket is pre-stressed before pouring, the pre-stressing weight is N, the box girder dead load is M, N≥1.1M.

[0033] Compared with the prior art, the present invention can at least achieve the following beneficial effects. The viaduct in this scheme is composed of a single-column bridge tower, a main beam and a cable, and the cable connects the single-column bridge tower and the main beam. When it rains, rainwater will drip on the surface of the cable and flow along the cable. During the flow, the water droplets connect to form a water line, thereby changing the cross-sectional shape of the cable, reducing the stability of the cable in the airflow, and then causing a large vibration of the cable, resulting in damage to the cable.

[0034] The waterline is mainly formed on the outer surface of the cable, so a spiral line and a pit are set on the outer surface of the cable. The pit can destroy the formation of the waterline and the axial flow, thereby slowing down the change of the cross-sectional shape of the cable caused by the waterline and slowing down the vibration. After the rain, rainwater will remain in the pit, which will increase the load of the cable and corrode the cable. Therefore, the depth of the pit should not be too deep, preferably 0.5mm to 1mm. Controlling the depth of the pit can reduce the possibility of water accumulation in the pit. Even if water is accumulated, the amount of water is small and can be evaporated or discharged quickly.

[0035] In addition to wind-rain induced vibration, dry-cable galloping is also a common vibration mode of the cable. After pits are opened on the surface of the outer sheath of the cable, the roughness of the outer surface of the cable increases, and the wind speed corresponding to its critical Reynolds number decreases, making the cable prone to large-amplitude vibration under common wind speeds. To this end, circular pits with different diameter ranges are designed, and pits with different diameters are opened on the outer sheath. By adjusting the size of the pits to improve the smoothness of the cable surface after the pits are opened, the wind speed corresponding to its critical Reynolds number is increased, and the wind-rain induced vibration is reduced while preventing the dry-cable galloping amplitude from being too large in clear weather. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0037] Figure 1 It is a schematic structural diagram of a cable-stayed bridge in a single-tower cable-stayed urban viaduct according to the present invention;

[0038] Figure 2 A cross-sectional view of a pit in a single-tower cable-stayed urban viaduct of the present invention;

[0039] Figure 3 It is a cross-sectional schematic diagram of a stay cable in a single-tower cable-stayed urban viaduct of the present invention;

[0040] Figure 4The present invention is a structural schematic diagram of a single-tower cable-stayed urban viaduct.

[0041] Description of Figure Numbers:

[0042] 100, stay cable; 110, core; 120, cable sleeve; 130, guide tube; 140, outer cladding; 150, helix; 160, pit; 161, first hypotenuse; 162, second hypotenuse; 200, single-column bridge tower; 300, main beam;

[0043] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0044] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0046] In the present invention, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0047] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the meaning of "and / or" appearing in the full text includes three parallel schemes. Taking "A and / or B" as an example, it includes scheme A, or scheme B, or a scheme that satisfies both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in the field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0048] When the cable-stayed cable vibrates greatly, cracks will appear at its anchor connection, causing fatigue or even damage to the cable ends, destroying the bridge structure and causing the bridge to become unstable. Therefore, in the design process of cable-stayed bridges, it is necessary to pay special attention to the vibration problem of the cables.

[0049] Reference Figure 1~Figure 4 The present invention proposes a single-tower cable-stayed urban viaduct, comprising:

[0050] The single-column bridge tower 200 is provided with a cable anchoring area, and the cable anchoring area is provided with a "well"-shaped prestressed steel bar;

[0051] The inclined cable 100 is arranged in a fan-shaped manner with a central double cable surface, and viscous shear dampers and vibration-damping rubber rings are installed at both ends. One end of the inclined cable 100 is anchored and connected to the cable anchoring area. The inclined cable 100 includes a core 110 and an outer layer 140. A spiral line 150 is arranged on the outer surface of the outer layer 140, and a circular pit 160 is opened. The pit 160 avoids the spiral line 150. The pit 160 includes at least two pits 160 with different diameters. The depth of the pit 160 is a, 0.5mm≤a≤1mm;

[0052] The other end of the main beam 300 and the inclined cable 100 are anchored and connected to the main beam 300. The main beam 300 is a single-box five-chamber prestressed concrete box beam. A cross beam is arranged at a predetermined interval in the middle span section, and the spacing between the cross beams is the same as the spacing between the inclined cables 100.

[0053] The viaduct in this scheme is composed of a single-column bridge tower 200, a main beam 300 and a stay cable 100, and the stay cable 100 connects the single-column bridge tower 200 and the main beam 300. When it rains, rain drops on the surface of the stay cable 100 and flows along the stay cable 100. During the flow, the water droplets connect to form a water line, thereby changing the cross-sectional shape of the cable, reducing the stability of the stay cable 100 in the airflow, and then causing a large vibration of the cable, resulting in damage to the cable.

[0054] The waterline is mainly formed on the outer surface of the inclined cable 100. For this purpose, a spiral line 150 is provided on the outer surface of the inclined cable 100 and a pit 160 is provided. The pit 160 can destroy the formation of the waterline and the axial flow, thereby slowing down the change of the cross-sectional shape of the inclined cable 100 caused by the waterline and slowing down the vibration. After the rain, rainwater will be retained in the pit 160. The retained rainwater will not only increase the load of the inclined cable 100, but also corrode the inclined cable 100. For this reason, the depth of the pit 160 should not be too deep, preferably 0.5mm to 1mm. Controlling the depth of the pit 160 can reduce the possibility of water accumulation in the pit 160. Even if water is accumulated, the amount of water is small and can be evaporated or discharged quickly.

[0055] The spiral line 150 can play a role in forcibly guiding rainwater to avoid the formation of a waterline. The spiral line 150 and the pit 160 reduce the vibration amplitude of the inclined cable 100 when it is excited by wind and rain.

[0056] A "well"-shaped prestressed bar is arranged in the cable anchorage area of ​​the bridge tower to improve the compressive strength of the concrete and the overall stability of the structure. The well-shaped prestressed arrangement forms multiple crossed prestressed bundles in the anchorage area, so that the prestressed bars can be more evenly distributed in the tower wall, thereby improving the overall force performance of the anchorage area. It reduces the impact and fatigue damage of the inclined cable 100 on the bridge tower structure when it vibrates due to wind and rain.

[0057] In addition to wind and rain induced vibration, dry cable galloping is also a common vibration mode of the inclined cable 100. After the pits 160 are opened on the surface of the outer layer 140 of the inclined cable 100, the roughness of the outer surface of the inclined cable 100 increases, and the wind speed corresponding to its critical Reynolds number decreases, making the inclined cable 100 prone to large-scale vibration under common wind speeds. For this reason, the circular pits 160 are designed to have different diameter ranges, and pits 160 with different diameters are opened in the outer layer 140. By adjusting the size of the pits 160 to improve the smoothness of the surface of the inclined cable 100 after the pits 160 are opened, the wind speed corresponding to its critical Reynolds number is increased, and the wind and rain induced vibration is reduced while preventing the dry cable galloping amplitude from being too large in clear weather.

[0058] In order to further adjust the surface smoothness of the inclined cable 100, the pits 160 are not designed to be distributed on all surfaces of the inclined cable 100. The side of the inclined cable 100 facing the ground can have fewer pits 160 or no pits 160, and only the spiral line 150 is set.

[0059] Furthermore, along the axial direction of the inclined cable 100, the cross-section of the pit 160 has a first oblique side 161 and a second oblique side 162, the first oblique side 161 is close to the high end of the inclined cable 100, the second oblique side 162 is close to the low end of the inclined cable 100, the angle between the inclined cable 100 and the ground is b, the angle between the second oblique side 162 and the ground is c, 0°<c<b, the angle between the first oblique side 161 and the high end surface of the inclined cable 100 is d, d<90°+b.

[0060] In order to prevent water from being accumulated in the pit 160, the pit 160 is designed as described above. Since there are multiple inclined cables 100, and the angles between each inclined cable 100 and the ground or horizontal plane are different, the first oblique side 161 and the second oblique side 162 in the cross section of the pit 160 on each inclined cable 100 are designed to meet the above-mentioned angle ranges.

[0061] The angle b between the second oblique side 162 and the ground is greater than 0° and less than the angle b between the inclined cable 100 and the ground, so that the second oblique side 162 is inclined toward the ground, and rainwater can flow along the second oblique side 162, out of the pit 160 and gradually flow away from the inclined cable 100.

[0062] The angle between the first oblique side 161 and the surface near the high end of the inclined cable 100 is d, which is called the path angle, and d<90°+b. When d>90+b, the connection between the first oblique side 161 and the second oblique side 162 is relatively smooth, and rainwater may flow continuously along the first oblique side 161 and the second oblique side 162.

[0063] At this time, the path angle is an acute angle, and when rainwater flows through the path angle, the flow path is cut off, further preventing rainwater from forming a water line. In addition, when the path angle is an acute angle, compared with when the path angle is an obtuse angle, the surface area of ​​the pit 160 can be reduced, thereby reducing wind resistance in daily life.

[0064] In order to further reduce the vibration amplitude of the inclined cable 100, viscous shear dampers and vibration-damping rubber rings are installed at both ends. When the inclined cable 100 vibrates, the viscous shear damper converts the vibration energy into the energy of the viscous medium flow and the shear mechanism movement inside the damper, thereby achieving energy dissipation and vibration reduction. The vibration-damping rubber ring also dissipates the vibration energy by using the damping properties of the rubber material. When the inclined cable 100 vibrates, the rubber material undergoes elastic deformation and produces a hysteresis effect to weaken the vibration energy, thereby playing a vibration reduction role.

[0065] One end of the cable 100 is anchored to the single-column bridge tower 200, and the other end is anchored to the main beam 300. A plurality of cross beams are arranged in the middle span of the main beam 300, and the spacing of the cross beams is the same as the spacing of the cable 100. The rigidity and stability of the main beam 300 are enhanced by arranging a plurality of cross beams, and better support is provided for the cable 100. At the same time, the spacing of the cross beams is the same as the spacing of the cable 100, which can maintain the symmetry and coordination of the structure and reduce the stress concentration of the cable 100.

[0066] Specifically, the main beam 300 adopts a single-box five-chamber prestressed concrete box beam, and a 2% outward slope is set at the top of the beam. A cross beam is set every 6m in the standard section of the middle span of the main beam 300, and a cross beam is set every 4m or 6m in the standard section of the side span. The spacing between the cross beams is the same as that of the inclined cable 100. The thickness of the cross beam in the side box is at least 50cm, and the thickness of the cross beam in the box chamber at the cable anchorage is at least 70cm; the main beam 300 adopts a longitudinal and transverse bidirectional prestressing system, and the transverse prestressing is set at the transverse diaphragm.

[0067] The upper end of the inclined cable 100 is anchored in the tower column, and the lower end is anchored in the main beam 300. The center distance between the two cable planes in the transverse direction of the bridge is 1.2m. The anchorage used for anchoring the inclined cable 100 consists of an anchor cup, an anchor ring, a wire dividing plate, a rear cover plate, a connecting tube, a sealing rubber ring, a sealing pressure ring and a cold-cast anchor filler.

[0068] The cable 100 is composed of a core 110, a cable sleeve 120, a guide tube 130 and an outer layer 140. The core 110 is a zinc-aluminum alloy coated parallel steel wire rope. The zinc-aluminum alloy coated parallel steel wire rope is composed of a plurality of parallel arranged steel wires, and the surface of these steel wires is coated with a layer of zinc-aluminum alloy coating, which has excellent corrosion resistance and can prevent the steel wire rope from corroding in a humid or salt spray environment. In addition, the coating also has good wear resistance and adhesion. When the cable vibrates, friction will occur between the steel wires. During the friction process, the coating is not easy to be damaged or peeled off, and can provide stable protection for the steel wires.

[0069] The outer periphery of the steel wire rope is also coated with a rope sheath 120 formed by a hot extrusion process of carbon black polyethylene. The hot extruded carbon black polyethylene rope sheath 120 can resist fatigue caused by cyclic stress and can resist erosion by ultraviolet rays, thus protecting the steel wire rope.

[0070] The steel wire and the cable sleeve 120 are both placed in the conduit 130, and the gap between the cable sleeve 120 and the inner wall of the conduit 130 is filled with foamed polyurethane. After filling with foamed polyurethane, the connection between the steel wire and the conduit 130 can be made tighter, preventing the steel wire from shaking or shifting in the conduit 130, and the polyurethane can limit the position of the steel wire to prevent direct contact between the steel wire and the conduit 130, thereby reducing the wear between the two. After the filling is completed, there is no gap between the steel wire and the conduit 130, and moisture, particulate impurities, etc. cannot enter the conduit 130, preventing them from corroding the steel wire.

[0071] In this solution, the outer layer 140 is two layers of high-density polyethylene, the inner layer is black high-density polyethylene, the outer layer is black high-density polyethylene, and the outer layer is colored high-density polyethylene. The outer layer is provided with a spiral line 150 and a circular pit 160. Specifically, the number of the spiral line 150 can be one or more, and the diameter of the circular pit 160 can be selected according to the specific size of the inclined cable 100.

[0072] The depth of the pit 160 is in the range of 0.5 mm to 1 mm, so as to prevent the pit 160 from being too deep and causing rainwater to remain in the pit 160 after rainfall.

[0073] Furthermore, the viaduct is a concrete bridge, and the concrete in this solution is composed of silicate cement, aggregate, admixtures and the like.

[0074] Specifically, when mixing concrete, it is necessary to verify the parameter standards of each material, including:

[0075] The content of tricalcium aluminate in silicate cement is ≤8wt%, the cement fineness is ≤350㎡ / kg, and the free calcium oxide is ≤1.5wt%.

[0076] Among the four mineral components of cement, tricalcium aluminate has the fastest hydration reaction rate with water and releases a large amount of heat. If the content of tricalcium aluminate is too high and the hydration reaction is too fast, it will cause the cement to false set, resulting in reduced workability and operability of the concrete, which is not conducive to the construction of the high part of the bridge tower.

[0077] Free calcium oxide is a dense component with a slow hydration process. When free calcium oxide reacts with water to form calcium hydroxide, its volume expands by about one time. Excessive volume expansion will cause expansion stress inside the hardened cement body, reducing the tensile strength of the cement, and uneven volume expansion will also cause cracks in the cement body. Even cracks, so the content of free calcium oxide needs to be strictly controlled.

[0078] Aggregates include fine aggregate and coarse aggregate. Fine aggregate is medium-coarse river sand with a weight loss rate of less than 5%, and coarse aggregate has a weight loss rate of less than 10%. Both fine aggregate and coarse aggregate must be tested for alkali activity before use.

[0079] Admixtures include fly ash, ground slag, silica fume, etc. The calcium oxide content in fly ash is less than 10wt%;

[0080] The ground slag is ground blast furnace water-quenched slag, and its Blaine surface area is ≥35㎡ / kg and ≤450㎡ / kg. The larger the Blaine surface area, the finer the slag particles are, and the larger the contact area with the cement product is, which is beneficial to the later strength development of concrete. However, if the Blaine surface area is too large, it will increase the water consumption of concrete and generate too much heat during the hardening process of concrete, which is not conducive to the stability of concrete. Therefore, the Blaine surface area of ​​ground blast furnace water-quenched slag is controlled within the range of 35㎡ / kg~450㎡ / kg.

[0081] The silica content in silica fume must be higher than 85wt%, and the Blaine surface area must be higher than 18,000㎡ / kg. Silica is the main component of silica fume, and its content is a key indicator for measuring silica fume. Silica fume with high silica content can react more effectively with calcium hydroxide in concrete to generate more stable calcium silicate gel, thereby improving the strength and durability of concrete. The larger the Blaine surface area of ​​silica fume, the finer and more dispersed the silica fume particles are, so that the silica fume particles can be effectively filled in the pores of concrete, improving the density and strength of concrete, and increasing the bonding force between concrete and aggregate, thereby improving the overall performance of concrete.

[0082] During the construction of the viaduct, a variety of steel components are needed. Some steel components (such as steel plates and main steel components) are used for concrete pouring, and some steel components (such as auxiliary steel components) are used for bridge ancillary facilities. In order to extend the service life of the steel components, anti-corrosion treatment is performed on the steel components.

[0083] Steel plates need to be pretreated during processing and manufacturing, and after pretreatment, the surface is coated with 20μm inorganic zinc silicate primer.

[0084] The main steel components are first treated with sandblasting to remove rust so that the surface roughness reaches Rz50~80μm, and then anti-corrosion treatment is carried out. From the inside to the outside, they are coated with a layer of epoxy zinc-rich layer with a thickness of 80μm; two layers of epoxy micaceous iron middle layer, each layer is 75μm thick; and two layers of fluorocarbon layers, with thicknesses of 40μm and 30μm respectively.

[0085] The attached steel components also need to be sandblasted to remove rust on the surface, and then coated from the inside to the outside with a layer of epoxy zinc phosphate with a thickness of 60μm; epoxy high-build paint, 80μm; and two layers of fluorocarbon paint, both 70μm.

[0086] Furthermore, the viaduct is also designed with a drainage system. The top surface of the main beam 300 is divided into a carriageway surface and a sidewalk surface. The carriageway surface is set with a 2% outward transverse drainage slope, and the sidewalk surface is set with a 1% inward transverse drainage slope. A 160mm diameter PVC-U transverse drainage pipe is set every 4~6m on the outside of the carriageway to pass through the inclined cable 100 area. Correspondingly, a drainage outlet is set at the outer side crash wall of the auxiliary non-motorized vehicle lane every 4~6m. A 160mm diameter PVC-U transverse drainage pipe is set and bent down to pass through the cantilever plate of the box beam. A 299mm diameter drainage steel pipe is set under the cantilever plate of the box beam to collect rainwater, which is led to the underground municipal drainage network through the downpipe at the main tower or pier. In order to ensure the firmness of the external drain pipe and the drain pipe, the drain pipe and the drain pipe are fixed to the lower edge of the box beam using pipe clamps and expansion bolts.

[0087] Furthermore, the ancillary facilities of the viaduct also include anti-glare panels, anti-throwing nets, etc.

[0088] To achieve the above object, the present invention further proposes a construction method of a single-tower cable-stayed urban viaduct, which is applied to the single-tower cable-stayed urban viaduct described above, comprising:

[0089] S1. Test the concrete mix ratio before construction to check the fluidity, workability, slow setting and early strength of the concrete;

[0090] S2. Use climbing formwork to construct the tower column. During the construction process, the pouring height of each section is ≤6m, and the shape of the tower column is always observed during the construction process;

[0091] S3. After the tower column construction is completed, prestressing is carried out after the concrete strength reaches 90% of the design strength, and the tensioning force and elongation are controlled during the tensioning process;

[0092] S4. After the tensioning is completed, the joint between the straight anchor concrete and the poured concrete is sealed;

[0093] S5. Roughen, degrease and clean the construction joints of each part of the single-column bridge tower.

[0094] Before the construction of the single-column bridge tower, a mix ratio test must be carried out to ensure the fluidity, workability, slow setting, early strength and other properties of the pumped concrete. After the concrete is poured, it is gently cured to control the hydration heat temperature to prevent the tower column from cracking due to excessive temperature.

[0095] After the concrete inspection is completed, the tower column is constructed using a climbing formwork. The number of tension screws used to fix the formwork in the construction formwork is reduced to ensure the appearance quality of the tower column concrete. The pouring height of each section of concrete is controlled below 6m, and the shape of the tower column is always observed during the construction process to prevent the tower column from having a large inclination error.

[0096] After pouring, wait for the concrete to solidify. When the concrete strength reaches 90%, the prestressed steel strands are tensioned. Before inserting the prestressed steel strands, use high-pressure air or water to remove impurities in the pipe, and tension them after cleaning.

[0097] After tensioning is completed, straighten the joint between the anchor concrete and the poured concrete.

[0098] Finally, the construction joints of each part of the single-column bridge tower are roughened, degreased, and cleaned to ensure the combination of new and old concrete. Check whether there are honeycombs, pits, shrinkage cracks, etc. on the exposed surface of the single-column bridge tower.

[0099] Specifically, in the tensioning step, tensioning includes longitudinal and transverse tensioning, the longitudinal prestressing of concrete is tensioned for at least 168 hours, the longitudinal prestressed steel strands remain symmetrical in the cross section of the box girder, and the two ends of the longitudinal steel strands are tensioned synchronously in the order of bottom plate strand-top plate strand.

[0100] The purpose of controlling the longitudinal prestressing tensioning time is to ensure that the bond between the prestressed steel strands and the concrete reaches the optimal state, allowing the concrete to have enough time to adapt to the tensioning of the prestressed steel strands, thereby reducing the prestress loss, improving the overall stability and durability of the structure, and making the stress distribution inside the concrete more uniform, which is beneficial to the long-term performance of the single-column bridge tower structure.

[0101] The two ends of the longitudinal steel bundles are tensioned synchronously to ensure that the load can be evenly distributed when the structure is under stress, preventing cracks or deformation in the structure.

[0102] Prestressing the bottom plate first can establish an effective prestress field in the concrete in advance, provide better stress transfer conditions for the subsequent tensioning of the top plate, and reduce the occurrence of local stress concentration during the tensioning process. In addition, as the main load-bearing part of the box girder, the stress state of the bottom plate has the greatest impact on the stability of the overall structure. Therefore, prestressing the bottom plate first can enhance the stability of the structure and provide better conditions for the subsequent tensioning of the top plate.

[0103] In addition, the tension stress and elongation are controlled during the tensioning process. The friction loss of the anchor ring and the internal friction loss of the jack should be considered during the construction of prestressed steel strands. This should be measured before construction and adjusted during tensioning.

[0104] When measuring the elongation, the non-elastic deformation should be deducted. The specific method is as follows: when tensioning to 15% of the design tonnage, hold the load for 3 minutes to measure the elongation. After tensioning to the design tonnage, hold the load for 3 minutes to measure the elongation Δ1. The actual elongation Δ=Δ1 / 0.85-б, where б is the clip retraction value. After measuring Δ1, return the oil, and then the elongation Δ2 on both sides must meet Δ-Δ2≤7mm. If Δ-Δ2>7mm, it is determined that the whole wire is slipped and needs to be processed. At the same time, check whether the mark at the end of the steel strand is still a plane after tensioning. If there is a change, the surface has slipped.

[0105] In step S4, after the tensioning of the prestressed steel strands is completed, the anchor heads and steel strands shall not be impacted. Excess steel strands shall be cut using a device such as a grinding wheel cutter, and grouting shall be completed within 24 hours. Grouting nozzles and exhaust holes can be set according to actual construction needs. Before grouting, compressed air should be used to remove impurities in the pipeline, and then grouting should be performed. The grouting adopts the vacuum assisted grouting method. The slurry material should be mixed with special additives for vacuum grouting. The pipeline grouting is required to be dense, the water-cement ratio of the cement slurry is not greater than 0.4, and the strength of the cement slurry is required to be not less than C50.

[0106] In step S2, after the construction of the lower tower column of the single-column bridge tower is completed, a tower side bracket is constructed on the top of the lower tower column. The bracket is pre-stressed before pouring. The pre-stressing weight is N, and the dead load of the box beam is M, N≥1.1M.

[0107] The brackets beside the tower are preloaded to simulate the actual load conditions, further verify whether the bearing capacity of the brackets meets the design requirements, and eliminate possible inelastic deformation, making the brackets more stable in subsequent use. In the actual construction process, due to various factors (such as material performance differences, construction errors, etc.), the actual bearing capacity of the brackets may differ from the design value. Therefore, the preload weight is designed to be more than 1.1 times the dead load of the box girder to reduce the risks brought by this uncertainty.

[0108] The above descriptions are only optional embodiments of the present invention, and are not intended to limit the patent scope of the present invention. All equivalent structural changes made using the contents of the present invention's specification and drawings, or directly / indirectly applied in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A single-tower cable-stayed urban viaduct, characterized in that: include: A single-column bridge tower is provided with a cable anchoring area, wherein the cable anchoring area is provided with a "well"-shaped prestressed steel bar; The cable is arranged in a fan-shaped shape with a central double cable surface, and viscous shear dampers and vibration-absorbing rubber rings are installed at both ends. One end of the cable is anchored and connected to the cable anchoring area. The cable includes a core and an outer cladding. A spiral line and a circular pit are arranged on the outer surface of the outer cladding. The pit avoids the spiral line. The pit includes at least two pits with different diameters. The depth of the pit is a, 0.5mm≤a≤1mm. Along the axial direction of the cable, the cross section of the pit has a first hypotenuse and a second hypotenuse. The first hypotenuse is close to the high end of the cable, and the second hypotenuse is close to the low end of the cable. The angle between the cable and the ground is b, and the angle between the second hypotenuse and the ground is c, 0°<c<b, and the angle between the first hypotenuse and the high end surface of the cable is d, d<90°+b; The other end of the inclined cable is anchored and connected to the main beam. The main beam is a single-box five-chamber prestressed concrete box beam. A cross beam is arranged at a predetermined interval in the middle span, and the spacing between the cross beams is the same as the spacing between the inclined cables.

2. The single-tower cable-stayed urban viaduct according to claim 1, characterized in that: The viaduct is a concrete bridge, and the concrete includes at least the following raw materials: Portland cement, wherein the content of tricalcium aluminate in the Portland cement is ≤8wt%, the cement fineness is ≤350㎡ / kg, and the free calcium oxide is ≤1.5wt%; Aggregates, including fine aggregate and coarse aggregate, wherein the fine aggregate is medium-coarse river sand with a weight loss rate of less than 5%, and the coarse aggregate has a weight loss rate of less than 10%; The admixture comprises at least fly ash, ground slag and silica fume, wherein the calcium oxide content in the fly ash is ≤10wt%, the ground slag is ground blast furnace water-quenched slag, and its Blaine surface area is ≥35㎡ / kg and ≤450㎡ / kg, the silicon dioxide content in the silica fume is ≥85wt%, and the Blaine surface area is ≥18000㎡ / kg.

3. The single-tower cable-stayed urban viaduct according to claim 1, characterized in that: The concrete is poured on part of the steel components, and the steel components at least include steel plates, main steel components and auxiliary steel components. The outer surface of the steel plate is coated with an inorganic zinc silicate primer protective layer; The main steel component is coated with a layer of epoxy zinc-rich layer, two layers of epoxy micaceous iron intermediate layers and two layers of fluorocarbon layers in sequence from the inside to the outside; The auxiliary steel member is coated with a layer of epoxy high build paint and two layers of fluorocarbon in sequence from the inside to the outside.

4. The single-tower cable-stayed urban viaduct according to claim 1, characterized in that: The stay cable comprises: A core, which is a zinc-aluminum alloy coated parallel steel wire rope; A cable sheath, which is coated on the outer periphery of the zinc-aluminum alloy coated parallel steel wire cable, and the cable sheath is formed by hot extrusion of carbon black polyethylene; A conduit, wherein the core and the cable sleeve are located inside the conduit, and the interior of the conduit is filled with foamed polyurethane; The outer layer is sleeved on the outer circumference of the catheter, and the outer layer includes at least two high-density polyethylene layers, and the outermost high-density polyethylene layer is provided with the spiral line and the pit.

5. A construction method for a single-tower cable-stayed urban viaduct, applied to the single-tower cable-stayed urban viaduct as claimed in any one of claims 1 to 4, characterized in that: include: S1. Test the concrete mix ratio before construction to check the fluidity, workability, slow setting and early strength of the concrete; S2. Use climbing formwork to construct the tower column. During the construction process, the pouring height of each section is ≤6m, and the shape of the tower column is always observed during the construction process; S3. After the tower column construction is completed, prestressing is carried out after the concrete strength reaches 90% of the design strength, and the tensioning force and elongation are controlled during the tensioning process; S4. After the tensioning is completed, the joint between the straight anchor concrete and the poured concrete is sealed; S5. Roughen, degrease and clean the construction joints of each part of the single-column bridge tower.

6. The construction method of the single-tower cable-stayed urban viaduct according to claim 5, characterized in that: In step S3, the tensioning includes longitudinal and transverse tensioning. The longitudinal prestressing of the concrete is tensioned for at least 168 hours. The longitudinal prestressing steel strands remain symmetrical in the cross section of the box girder. Both ends of the longitudinal steel strands are tensioned synchronously in the order of bottom plate strands-top plate strands.

7. The construction method of a single-tower cable-stayed urban viaduct as claimed in claim 6, characterized in that: In step S3, when tensioning to 15% of the design tonnage, the load is held for 3 minutes to measure the elongation. After tensioning to the design tonnage, the load is held for 3 minutes to measure the elongation Δ1. The actual elongation Δ=Δ1 / 0.85-б, where б is the clip retraction value. After measuring Δ1, the oil is returned, and then the elongation Δ2 on both sides must satisfy Δ-Δ2≤7mm. If Δ-Δ2>7mm, it is determined that the entire wire is slipped and needs to be processed.

8. The construction method of a single-tower cable-stayed urban viaduct as claimed in claim 5, characterized in that: In step S4, after the prestressed steel strands are tensioned, the excess steel strands are cut and grouting is completed within 24 hours. Before grouting, impurities in the pipeline are removed and grouting is completed using a vacuum-assisted grouting method.

9. The construction method of a single-tower cable-stayed urban viaduct as claimed in claim 5, characterized in that: In step S2, after the construction of the lower tower column of the single-column bridge tower is completed, a tower side bracket is constructed on the top of the lower tower column. The bracket is pre-stressed before pouring. The pre-stressing weight is N, and the dead load of the box beam is M, N≥1.1M.

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