Construction method of large offshore V-shaped pier column steel structure

Abstract

The present application relates to the technical field of building engineering, and more particularly to a construction method of large offshore V-shaped pier column steel structure, comprising: step S1, setting a plurality of concrete prefabricated sleeve box pedestals on the sea, and installing corbel support assemblies; step S2, assembling prefabricated concrete sleeve boxes in sections; step S3, hoisting the concrete sleeve boxes to the prefabricated sleeve box pedestals, welding and fixing the concrete sleeve boxes with the corbel support assemblies, and pouring the bottom under water; step S4, cleaning the accumulated water in the concrete sleeve boxes, cutting the excess corbel support assemblies, chiseling and leveling the pile heads; step S5, carrying out construction of the pile cap, binding the steel bars, pouring the concrete, and watering for maintenance; step S6, dividing the V-shaped pier into three-layer structures of the bottom, the receiving part and the pier arm, and carrying out construction in layers on the pile cap; and step S7, erecting V-shaped pier cap beam supports and abutments. The present application can guarantee uniformity of overall structural stress and durability, improve construction efficiency, and reduce construction risks through real-time stress monitoring and offshore wind and wave compensation measures.

Description

Technical Field

[0001] This invention relates to the field of building engineering technology, and in particular to a construction method for a large-scale offshore V-shaped pier steel structure. Background Technology

[0002] Large offshore V-shaped steel piers are key supporting components for major infrastructure projects such as cross-sea bridges and deep-water ports. Their construction faces unique challenges from the marine environment: harsh conditions such as wind, waves, tides, and corrosion severely affect construction accuracy and safety; deep-sea foundation positioning is difficult, and the stability of large components during hoisting is poor; traditional cast-in-place construction is greatly constrained by the environment, resulting in low efficiency, high risk, and the concrete structure is prone to cracking, making it difficult to guarantee durability. To overcome these problems, a construction method that can achieve high-precision positioning, rapid installation, and structural stability and durability is needed.

[0003] Chinese Patent Publication No. CN114737494A discloses a method for offshore construction, comprising the following steps: S1, installing an offshore work platform on the waterborne structure of a bridge and fixing the offshore work platform to the waterborne structure; S2, installing a guide frame on the offshore work platform and lowering the guide frame into the sea; S3, lowering a construction pipe into the sea through the guide frame; S4, injecting reinforcing material into the construction pipe. It is evident that this invention suffers from uneven stress distribution and low stability during the installation of the offshore platform on the waterborne structure, and lacks measures to resist sea winds and waves. Summary of the Invention

[0004] Therefore, this invention provides a construction method for large offshore V-shaped pier steel structures to overcome the problems of poor stability of large component hoisting and the great environmental constraints of traditional cast-in-place construction in the prior art.

[0005] To achieve the above objectives, the present invention provides a construction method for a large offshore V-shaped pier steel structure, comprising: Step S1: Set up several precast caisson platforms made of concrete at sea, and install bracket support components on the precast caisson platforms. Step S2: Assemble the precast concrete housing in sections; Step S3: Hoist the concrete casing onto the precast casing platform, weld and fix it to the corbel support assembly, and pour the bottom sealing material underwater; Step S4: Obtain the water level inside the precast concrete casing, remove the water, cut off the excess corbel support components, and chisel away and level the pile head. Step S5: Determine the height of the foundation according to the water level, and carry out foundation construction, including tying steel bars, pouring concrete, and water curing. Step S6: Divide the V-shaped pier into three layers: bottom, bearing section, and pier arm. Determine the water-facing area of ​​the V-shaped pier based on the environmental parameters of the pier cap, and carry out construction layer by layer on the pier cap. The environmental parameters of the pier cap include the wave height and wave wavelength that the pier cap will experience. Step S7: Erect the V-shaped pier cap beam support and bridge abutment.

[0006] Further, step S2 includes: Step S21: Lay the bottom slab reinforcement bars, and place concrete spacers under the bottom slab reinforcement bars, with no less than 4 concrete spacers per square meter of bottom slab reinforcement bars. Install the caisson bottom slab formwork. Step S22: Pour concrete to form the base slab and simultaneously pour a side wall with a height of 15cm. Vibrate the concrete and remove the formwork when the concrete strength of the base slab reaches the preset strength. Then, allow the concrete to cure. Step S23: Use a lifting device to lift the base plate, apply a protective coating to its bottom, and attach rubber sheets and soft foam boards to ensure that the base plate is evenly stressed. Attach rubber pads to the bottom chamfered areas to prevent damage to the lifting straps during lifting. Step S24: Lap the side wall reinforcement on the bottom slab reinforcement and install the box girder side wall formwork; Step S25: Pour concrete into the side wall, vibrate it, and remove the formwork when the concrete strength of the side wall reaches the preset strength for curing. Step S26: Apply a protective coating to the outside of the sidewall.

[0007] Further, in step S3, the hoisting process includes: Step S31: Use a crane vessel with slings to lift and transport the precast concrete caisson to its destination via a barge; Step S32: Use the boom of the crane vessel to lift the precast concrete caisson onto the pre-installed corbel support assembly; Step S33: When the precast concrete casing is lowered to the bracket marking position, the precast concrete casing is welded to the bracket support assembly using a steel plate, and the gap between the rubber plate and the bracket support assembly is filled. Step S34: Pour the sealing material.

[0008] Further, in step S5, determining the height of the foundation based on the water accumulation height includes: Step S51: Determine the normal water level based on the water level inside the concrete casing; Step S52: Determine the high water level based on historical data of the river's highest water level; Step S53: Determine the standard height of the top of the pier and the standard height of the bottom of the pier based on the normal water level and the high water level, and correct the standard height using a safety redundancy coefficient; wherein, the top of the pier is buried below the normal water level or the beach surface to reduce water obstruction and direct wind impact; Step S54: Calculate the buoyancy load based on the standard height of the top of the pier and the standard height of the bottom of the pier.

[0009] Further, in step S6, determining the water-facing area of ​​the V-shaped pier based on the environmental parameters of the pier cap includes: Step S61: Obtain historical data on the wave height and wave wavelength experienced by the pier; Step S62: Calculate the wave impact force based on the historical data; Step S63: Calculate the water-facing area of ​​the bottom of the V-shaped pier based on the wave impact force.

[0010] Further, step S5, pouring concrete, includes: The concrete is poured in layers, with each layer poured from the middle outwards, so that the next layer is poured before the previous layer has set. Each layer of concrete is also vibrated. The layered pouring process uses a pump truck to pour concrete from a floating platform on the side of the foundation.

[0011] Furthermore, in step S6, the V-shaped pier construction process includes: The first and second stages of the V-shaped pier were concrete-poured using a pump truck. The third stage was carried out by a crane lifting the hopper and connecting a tremie pipe below the hopper for pouring. A reserved hole was opened in the middle of the formwork in the third stage so that the concrete could be transported to the bottom through the tremie pipe and an attached vibrator was installed at the bottom. The third stage of pouring should be done symmetrically on both sides to avoid safety hazards caused by eccentric stress on the V-shaped pier.

[0012] Further, in step S6, after the V-shaped pier structure is constructed, the installation of temporary consolidation support structure includes installing several temporary support steel pipes on each V-shaped pier arm, with the inside of the steel pipes filled with concrete to provide restraint during external prestressing tensioning so that the deformation value of the V-shaped pier does not exceed the design requirements. After the temporary fixed support structure is installed, it is subjected to external prestressing tension, and the bridge deck structure, including the main beam and precast slab, is installed on the V-shaped pier structure. After installation, the temporary fixed support structure is removed. The bridge deck structure includes the main beam and precast slab.

[0013] Furthermore, in steps S5 and S6, concrete for pouring is prepared in advance, wherein modifications are made to the concrete based on the environmental impact, including: Obtain ambient temperature data; When the ambient temperature data is greater than or equal to the preset temperature threshold, a water-reducing agent is added to the concrete to reduce the water-cement ratio and improve crack resistance, or a retarder is added to extend the setting time of the concrete and slow down the rate of cement hydration reaction. The concrete is poured in layers to control the pouring speed within the preset value of the formwork stress calculation. Based on the formwork stress calculation, the pouring height of a single layer is obtained, and vibration is performed after each layer is poured.

[0014] Furthermore, in steps S5 and S6, an immersion vibrator is used to compact the concrete structure.

[0015] Compared with the prior art, the beneficial effects of the present invention are that the precast concrete caisson adopts the segmented prefabrication of the bottom plate and side walls, and the steel reinforcement binding, formwork installation and concrete pouring are completed on land, avoiding the uncertainties at sea, ensuring the dimensional accuracy of the components and the quality of the concrete. The side wall formwork adopts segmented installation and vertical line adjustment to ensure verticality and linear accuracy.

[0016] Furthermore, the prefabricated caissons are transported and hoisted as a whole by crane vessels and barges, which reduces the time spent at sea and the interference of wind and waves. During the hoisting process, special lifting tools, bottom protective coatings and rubber pads are used to avoid damage to the lifting slings and stress concentration, ensuring that the components are evenly stressed and that the hoisting is safe.

[0017] Furthermore, the bracket support assembly is made of H-beams welded to steel casings, with an annular steel plate on top to provide stable support for the casing. The diameter of the pre-drilled hole at the bottom of the casing is larger than that of the steel casing, which compensates for the misalignment error when the steel casing is installed and improves the installation tolerance. By welding the pre-embedded steel plate to the annular steel plate and filling the gaps in the rubber plate, buoyancy and wave impact are effectively resisted, ensuring the rigid connection between the casing and the support system. The annular steel plate also serves as the bottom formwork for the sealing concrete, optimizing the construction process.

[0018] Furthermore, during the template installation phase, the linearity and stability of the template are adjusted using diagonal supports, tie rods, and top brackets, and a comprehensive acceptance test is conducted to ensure uniform stress distribution.

[0019] Furthermore, the third stage of the V-shaped pier is poured symmetrically to avoid eccentric stress, and the concrete is compacted by an attached vibrator. The temporary consolidation support structure provides restraint during external prestressing tensioning, controls deformation within the design limits, ensures safety through monitoring, and ensures no residual impact during final removal.

[0020] Furthermore, by using prefabricated steel bar semi-finished products in the factory, prefabricating caissons in sections, and pouring foundations in layers, the amount of manual labor at sea and the construction period were reduced.

[0021] Furthermore, the corbel support, welded fixing, and bottom sealing pouring form a stable working platform, avoiding the instability of traditional offshore supports. The temporary consolidation structure ensures the safety of the V-shaped pier during tensioning and bridge deck installation, and is eventually removed without any residual impact.

[0022] Furthermore, the pouring process can be optimized by using equipment such as pump trucks and tremie pipes to reduce the risks of working at height. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the construction method for a large offshore V-shaped pier steel structure in an embodiment of the present invention; Figure 2 This is a schematic diagram of the concrete caisson bottom plate lifting method in the construction method of a large offshore V-shaped pier steel structure in an embodiment of the present invention; Figure 3 This is a schematic diagram of the overall lifting method of the concrete caisson in the construction method of the large marine V-shaped pier steel structure in an embodiment of the present invention; Figure 4 This is a three-dimensional schematic diagram of the first stage of the construction method of the large marine V-shaped pier steel structure in this embodiment of the invention; Figure 5 This is a three-dimensional schematic diagram of the second stage of the construction method of the large marine V-shaped pier steel structure in this embodiment of the invention; Figure 6 This is a three-dimensional schematic diagram of the third stage of the construction method of the large marine V-shaped pier steel structure in this embodiment of the invention.

[0024] Among them, 100 is the bottom plate of the concrete casing, 101 is the reserved hole of the concrete casing, 102 is the lifting strap, 200 is the side wall of the concrete casing, 201 is the lifting tool of the crane ship, 300 is the pier cap, 301 is the water-facing surface of the bottom of the V-shaped pier, 400 is the bottom of the V-shaped pier, 401 is the bearing part of the V-shaped pier, and 402 is the pier arm of the V-shaped pier. Detailed Implementation

[0025] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0026] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0027] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0028] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0029] Please see Figure 1 As shown, it is a schematic diagram of the construction method of the large offshore V-shaped pier steel structure of the present invention, including: Step S1: Set up several precast caisson platforms made of concrete at sea, and install bracket support components on the precast caisson platforms. Specifically, the corbel support assembly consists of four H-beams of equal length welded to a steel casing, with an annular steel plate welded to the top of the steel casing. Step S2: Assemble the precast concrete housing in sections; Specifically, the assembly process includes: Step S21: Lay the bottom slab reinforcement bars, and place concrete spacers under the bottom slab reinforcement bars, with no less than 4 concrete spacers per square meter of bottom slab reinforcement bars. Install the caisson bottom slab formwork. Step S22: Pour concrete to form a base slab 100 and simultaneously pour a side wall with a height of 15cm. Vibrate the concrete and remove the formwork when the concrete strength of the base slab reaches the preset strength (preferred value, 2.5MPa). Then, allow the concrete to cure. Specifically, the bottom of the precast concrete casing has a reserved hole 101 with a diameter larger than that of the steel casing, so that it is not affected by the deviation during the installation of the steel casing. Furthermore, around the reserved hole 101 at the bottom of the precast concrete casing, a reserved steel plate with a preset height (preferred value, 10cm) is welded, and the top of the reserved steel plate is sealed with a water-stop strip. Step S23, please refer to Figure 2As shown, the base plate 100 is lifted using a lifting device 102. Preferably, a 200T crane is used with two 80T slings. A protective coating is applied to the bottom of the base plate 100. Preferably, a 350μm thick silane primer and acrylic topcoat protective coating are applied, and a 20mm thick rubber sheet and a 5mm thick soft foam board are attached to ensure that the base plate 100 is subjected to uniform force. Rubber pads are attached to the bottom chamfered position to avoid damage to the slings 102 during the lifting process. Step S24: Lap the side wall reinforcement on the bottom slab reinforcement and install the box girder side wall formwork; Specifically, the installation of the side wall formwork for the housing includes: The side wall formwork of the casing is divided into inner formwork and outer formwork. The height of the inner formwork is lower than that of the outer formwork. The outer formwork uses two types of steel pipes of different lengths as diagonal and horizontal supports. The bottom of the diagonal and horizontal supports is fixed to the ground with expansion bolts. The spacing between the diagonal supports is no more than 1.2m, preferably 1m. The side wall templates of the casing are installed in sections along the direction of the casing. One of the outer templates is lifted and installed on one side of the base plate, and the diagonal support is used to make the template stable. Then the inner template is lifted and installed. After the inner and outer templates are aligned, the top and bottom bolts are tightened. The template linearity is adjusted using tie rods to make the template in the overall closed state. After the side wall formwork is fixed, install support rods on top of it, tighten all the connecting bolts between the support rods and the side wall formwork, and lay them out to form a working passage. Erect a high scaffolding operating platform on the side wall formwork for subsequent formwork and steel reinforcement installation. Set up ladders to allow workers to enter the inside of the casing for work.

[0030] The side wall formwork is adjusted for verticality using a plumb line method. When the verticality meets the requirements, i.e., the error is less than 8mm, the position and elevation of the top plane are measured and verified, and finally a comprehensive inspection and acceptance are carried out.

[0031] Step S25: Pour 200 mm of concrete into the side wall, vibrate it, and remove the formwork when the concrete strength of the side wall reaches the preset strength (preferred value, 2.5 MPa) and then cure it. Step S26: Apply a protective coating to the outside of the sidewall 200, preferably a 350μm protective coating of silane primer and acrylic topcoat. The side walls 200 are the four walls perpendicular to the base plate 100 in the concrete casing, and they are distributed around the base plate 100.

[0032] Step S3: Hoist the concrete casing onto the precast casing platform, weld and fix it to the corbel support assembly, and then pour underwater to seal the bottom. Please see Figure 3 As shown, specifically, the hoisting process includes: Step S31: Use a crane vessel with lifting equipment 201 to lift and transport the precast concrete cassette to its destination via a barge. Step S32: Use the boom of the crane vessel to lift the precast concrete caisson onto the pre-installed corbel support assembly; Step S33: When the precast concrete casing is lowered to the bracket marking position, the precast concrete casing is welded to the bracket support assembly using a steel plate, and the gap between the rubber plate and the bracket support assembly is filled. Specifically, during the welding process, the pre-embedded steel plate is welded to the annular steel plate using a steel plate to resist buoyancy. The annular steel plate serves as the bottom mold when the sealing material is poured.

[0033] It is understandable that during the welding process, water will accumulate because the bottom of the casing is not completely sealed. Therefore, underwater welding technology is required. Underwater welding technology is existing technology and will not be described in detail in this invention.

[0034] Step S34: Pour the sealing material underwater.

[0035] The sealing material is a cement-based grouting material with good underwater sealing properties. Those skilled in the art can select the corresponding material according to the specific scenario. This invention does not limit the selection of materials, and all of them are within the protection scope of this invention.

[0036] Step S4: Clean the water inside the concrete casing, cut off the excess corbel support components, and chisel away and level the pile head; Step S5: Construct the foundation 300mm, tie the reinforcing bars, pour the concrete, and water it for curing. Determining the height of the foundation 300 based on the water accumulation height includes: Step S51: Determine the normal water level based on the water level inside the concrete casing; Step S52: Determine the high water level based on historical data of the river's highest water level; Step S53: Determine the standard height of the top of the foundation and the standard height of the bottom of the foundation based on the normal water level and the high water level, and correct the standard height using a safety redundancy factor. The safety redundancy coefficient is an empirical coefficient, and its preferred value is 1.1 to cover risks such as material properties, construction errors, and model uncertainties. Specifically, the standard height of the top of the pier is greater than 1.1 times the normal water level, and the standard height of the bottom of the pier is less than 1.1 times the high water level. Step S54: Calculate the buoyancy load based on the standard height of the top of the pier and the standard height of the bottom of the pier.

[0037] It is understandable that calculating the buoyancy load based on the height of the pier is existing technology, and will not be elaborated here.

[0038] When pouring 300mm concrete for the foundation, the concrete is poured in layers, each layer being 30-40cm thick. Each layer is poured from the middle outwards, so that the next layer is poured before the previous layer has set. Each layer of concrete is also vibrated. The layered pouring process uses a pump truck to pour concrete from the water platform on the side of the pier cap 300 to the pier cap.

[0039] Please see Figure 4-6 As shown, in step S6, the V-shaped pier is divided into three layers: bottom 400, bearing part 401, and pier arm 402. The water-facing surface 301 of the bottom of the V-shaped pier is determined according to the environmental parameters of the pier cap, so that construction can be carried out layer by layer on the pier cap. The environmental parameters of the pier cap include the wave height and average wave frequency experienced by the pier cap 300. The determination of the bottom water-facing surface area of ​​the V-shaped pier based on the environmental parameters of the pier cap includes: Step S61: Obtain data on wave height, wave velocity, and average wave frequency experienced by the pier. Step S62, calculate the wave impact force;

[0040] Where F represents the wave impact force. Where is the density of seawater (kg / m³), g is the acceleration due to gravity, H is the wave height, and L is the wave wavelength; Step S63: Calculate the water-facing area of ​​the bottom of the V-shaped pier based on the wave impact force;

[0041] Where A is the water-facing surface area at the bottom of the V-shaped pier, and F is the wave impact force. Where is the density of seawater (kg / m³), g is the acceleration due to gravity, H is the wave height, and k is an empirical coefficient selected based on hydrological conditions, with a preferred value of 0.7.

[0042] Specifically, the construction process of the V-shaped pier includes: The first and second stages of the V-shaped pier were concrete-poured using a pump truck. The third stage was carried out by a crane lifting the hopper and connecting a tremie pipe below the hopper for pouring. A reserved hole was opened in the middle of the formwork in the third stage so that the concrete could be transported to the bottom through the tremie pipe and an attached vibrator was installed at the bottom. The third stage of pouring should be done symmetrically on both sides to avoid safety hazards caused by eccentric stress on the V-shaped pier.

[0043] After the V-shaped pier structure is constructed, a temporary consolidation support structure is installed, including installing several temporary support steel pipes on each V-shaped pier arm. The steel pipes are filled with concrete to provide restraint during external prestressing tensioning so that the deformation value of the V-shaped pier does not exceed the design requirements. After the temporary consolidation support structure is installed, it is subjected to external prestressing tension, and the bridge deck structure, including the main beam and precast slab, is installed on the V-shaped pier structure. After the installation is completed, the temporary consolidation support structure is removed.

[0044] Step S7: Erect the V-shaped pier cap beam support and bridge abutment.

[0045] Specifically, in steps S5 and S6, concrete for pouring is prepared in advance, wherein improvements are made to the concrete based on the environmental impact on it, including: Acquire ambient temperature data; When the ambient temperature data is greater than or equal to the preset temperature threshold, a water-reducing agent is added to the concrete to reduce the water-cement ratio and improve crack resistance, or a retarder is added to extend the setting time of the concrete and slow down the cement hydration reaction. The concrete temperature when it is placed in the formwork is less than 25°C, the core temperature is less than 68°C, and the temperature difference between the inside and outside is less than 40°C. In this embodiment, the preset temperature threshold is 30°C, the amount of water-reducing agent added is 1% to 5% of the total mass, the water-cement ratio is reduced by 15% to 30%, the amount of retarder added is 0.1% to 0.3% of the total mass, and the setting time of concrete is extended by 2h to 10h.

[0046] The concrete is poured in layers to control the pouring speed within the preset value of the formwork stress calculation. Based on the formwork stress calculation, the pouring height of a single layer is obtained, and each layer is vibrated and compacted after pouring.

[0047] Specifically, by performing stress calculations on the template, the maximum lateral pressure value of the poured concrete on the template can be obtained. The maximum lateral pressure value can be divided by the concrete density obtained through testing to calculate the single-layer pouring height.

[0048] It is understandable that the stress calculation of the template is a current technology, and will not be elaborated here.

[0049] The standard for compaction is that the concrete stops settling, no more air bubbles emerge, the surface is flat and covered with slurry, the vibrator does not touch the reinforcing bars when vibrating the concrete in the reinforcing bar area, and a safe distance should be maintained between the vibrator and the formwork. When vibrating newly poured concrete, the vibrator head should be inserted into the next layer of concrete to make the two layers bond together.

[0050] Specifically, all steel bars are processed and bent by the processing plant according to the design drawings, and the semi-finished products are transported to the construction site for steel bar binding.

[0051] Example: At a location more than 2 meters from the dock retaining wall in the nearshore area, six precast concrete-cast caisson platforms were installed, each measuring 14.9m x 7.4m and 300mm thick. A 6mm thick steel plate was placed on the platform as the bottom formwork, and a corbel support assembly was installed. The corbel support assembly consisted of four 400mm long H-beams and a 20mm thick ring steel plate, which were welded to a steel casing with a diameter of 1.38m.

[0052] Precast concrete caissons are assembled in sections, and the bottom slab reinforcement is laid. Four concrete pads are placed under the bottom slab reinforcement per square meter. The location of the pile hole is reserved according to the design requirements. The diameter of the reserved pile hole 101 is 1.48m. When the bottom slab reinforcement is tied, the reserved reinforcement with a length of 30cm is lapped with the side wall reinforcement.

[0053] A 100mm thick concrete base slab was poured, along with 15cm high side walls. After pouring, the concrete was vibrated. Once the concrete strength of the base slab reached 2.5MPa, the formwork was removed, and the slab was water-cured. A 200T crane with two 80T slings was used to lift the base slab. A 350μm thick silane primer and acrylic topcoat protective coating were applied to the bottom, and a 20mm thick rubber sheet and a 5mm thick soft foam board were attached. Rubber pads were attached to the bottom chamfered corners. A 10cm high steel plate was welded around the pre-drilled holes, and the top of the steel plate was sealed with a water-stop strip.

[0054] The side wall reinforcement is tied in sections, with a maximum length of 5m. The formwork is installed immediately after the reinforcement sections are tied to prevent the side wall reinforcement from collapsing.

[0055] The outer formwork of the side wall is 3m high and the inner formwork is 2.4m high. The formwork is reinforced with tie rods. The outer formwork uses 2.6m steel pipes as horizontal supports and 1.295m steel pipes as diagonal supports. The bottom of the supports is fixed to the ground with expansion bolts. The spacing between the diagonal supports is 1m.

[0056] The side wall formwork of the casing is installed in sections along the direction of the casing. An outer formwork is hoisted and installed on one side of the base plate. The formwork is stabilized by the diagonal support. Then the inner formwork is hoisted and installed. After the inner and outer formwork are aligned, the top and bottom bolts are tightened. The linearity of the formwork is adjusted by tie rods so that the formwork is in the overall closed state. After the side wall formwork is fixed, install support rods on top of it, tighten all the connecting bolts between the support rods and the side wall formwork, and lay them out to form a working passage. Erect a high scaffolding operating platform on the side wall formwork for subsequent formwork and steel reinforcement installation. Set up ladders to allow workers to enter the inside of the casing for work.

[0057] The side wall formwork is adjusted for verticality using a plumb line method. When the verticality error is less than 8mm, the position and elevation of the top plane are measured and verified. Finally, a comprehensive inspection and acceptance are carried out.

[0058] Pour 200mm of concrete into the side wall, vibrate it, and remove the formwork when the concrete strength of the side wall reaches 2.5MPa. Then cure it and apply a 350μm protective coating of silane primer and acrylic topcoat to the outside of the side wall.

[0059] A 200T crane vessel was used with two 80T slings to lift the container, and an 800T barge was used for transportation. The barge measures 36.6m x 12.1m and can carry two precast concrete caissons at a time. The barge and crane vessel were then transferred to the caisson installation area by tugboats. The precast concrete caisson was lifted onto the pre-installed corbel support assembly using the boom of the crane vessel. When the precast concrete casing is lowered to the bracket marking position, a 16mm steel plate is used to weld the precast concrete casing to the bracket support assembly, and the gap between the rubber plate and the bracket support assembly is filled. A ring-shaped steel plate is used as the bottom mold, and the bottom sealing material is poured.

[0060] Clean the water inside the concrete casing, cut off excess corbel support components, and chisel and level the pile heads; determine the normal water level based on the water level inside the concrete casing, and determine the high water level based on historical data of the highest river water level; determine the standard height of the top and bottom of the pier cap based on the normal water level and the high water level, and correct the standard height using a safety redundancy coefficient; calculate that the pier cap height of 300mm is 2.15m; after buoyancy load verification, pier cap construction can proceed, including tying reinforcing bars, pouring concrete, and water curing; The V-shaped pier is divided into three layers: the bottom 400, the supporting part 401, and the pier arm 402. Construction is carried out layer by layer on the pier cap 300. Based on the environmental parameters of the pier cap, the area of ​​the water-facing surface 301 at the bottom of the V-shaped pier is determined to be 22.4㎡.

[0061] The first and second stages of the V-shaped pier were concrete-poured using a pump truck. The third stage was carried out by a crane lifting the hopper and connecting a tremie pipe below the hopper for pouring. A reserved hole was opened in the middle of the formwork in the third stage so that the concrete could be transported to the bottom through the tremie pipe and an attached vibrator was installed at the bottom. The third stage of pouring should be done symmetrically on both sides to avoid safety hazards caused by eccentric stress on the V-shaped pier.

[0062] After the V-shaped pier structure is constructed, a temporary consolidation support structure is installed, including installing several temporary support steel pipes on each V-shaped pier arm. The steel pipes are filled with concrete to provide restraint during external prestressing tensioning so that the deformation value of the V-shaped pier does not exceed the design requirements. After the temporary consolidation support structure is installed, it is subjected to external prestressing tension, and the bridge deck structure, including the main beam and precast slab, is installed on the V-shaped pier structure. After the installation is completed, the temporary consolidation support structure is removed.

[0063] Erect V-shaped pier cap beam supports and bridge abutments.

[0064] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

[0065] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A construction method for a large offshore V-shaped pier steel structure, characterized in that, include: Step S1: Set up several precast caisson platforms made of concrete at sea, and install bracket support components on the precast caisson platforms. Step S2: Assemble the precast concrete housing in sections; Step S3: Hoist the precast concrete casing onto the precast casing platform, weld and fix it to the corbel support assembly, and pour the bottom sealing material underwater; Step S4: Obtain the water level inside the precast concrete casing, remove the water, cut off the excess corbel support components, and chisel away and level the pile head. Step S5: Determine the height of the foundation according to the water level, and carry out foundation construction, including tying steel bars, pouring concrete, and water curing. Step S6: Divide the V-shaped pier into three layers: bottom, bearing section, and pier arm. Determine the water-facing area of ​​the V-shaped pier based on the environmental parameters of the pier cap, and carry out construction layer by layer on the pier cap. The environmental parameters of the pier cap include the wave height and wave wavelength that the pier cap will experience. Step S7: Erect the V-shaped pier cap beam support and bridge abutment.

2. The construction method for a large offshore V-shaped pier steel structure according to claim 1, characterized in that, Step S2 includes: Step S21: Lay the bottom slab reinforcement bars, place concrete spacers under the bottom slab reinforcement bars, wherein there are no less than 4 concrete spacers under each square meter of bottom slab reinforcement bars, and install the caisson bottom slab formwork. Step S22: Pour concrete to form the base slab and simultaneously pour a side wall with a height of 15cm. Vibrate the concrete and remove the formwork when the concrete strength of the base slab reaches the preset strength. Then, allow the concrete to cure. Step S23: Use a lifting device to lift the base plate, apply a protective coating to its bottom, and attach rubber sheets and soft foam boards to ensure that the base plate is evenly stressed. Attach rubber pads to the bottom chamfered areas to prevent damage to the lifting straps during lifting. Step S24: Lap the side wall reinforcement on the bottom slab reinforcement and install the box girder side wall formwork; Step S25: Pour concrete into the side wall, vibrate it, and remove the formwork when the concrete strength of the side wall reaches the preset strength for curing. Step S26: Apply a protective coating to the outside of the sidewall.

3. The construction method for a large offshore V-shaped pier steel structure according to claim 2, characterized in that, In step S3, the hoisting process includes: Step S31: Use a crane vessel with slings to lift and transport the precast concrete caisson to its destination via a barge; Step S32: Use the boom of the crane vessel to lift the precast concrete caisson onto the pre-installed corbel support assembly; Step S33: When the precast concrete cascade descends to the bracket marking position, the precast concrete cascade is welded to the bracket support assembly using a steel plate, and the gap between the rubber plate and the bracket support assembly is filled. Step S34: Pour the sealing material.

4. The construction method for a large offshore V-shaped pier steel structure according to claim 3, characterized in that, In step S5, determining the height of the foundation based on the water accumulation height includes: Step S51: Determine the normal water level based on the water level inside the concrete casing; Step S52: Determine the high water level based on historical data of the river's highest water level; Step S53: Determine the standard height of the top of the pier and the standard height of the bottom of the pier based on the normal water level and the high water level, and correct the standard height using a safety redundancy coefficient; wherein, the top of the pier is buried below the normal water level or the beach surface to reduce water obstruction and direct wind impact; Step S54: Calculate the buoyancy load based on the standard height of the top of the pier and the standard height of the bottom of the pier.

5. The construction method for a large offshore V-shaped pier steel structure according to claim 4, characterized in that, In step S6, the area of ​​the water-facing surface at the bottom of the V-shaped pier is determined based on the environmental parameters of the pier cap, including: Step S61: Obtain historical data on the wave height and wave wavelength experienced by the pier; Step S62: Calculate the wave impact force based on the historical data; Step S63: Calculate the water-facing area of ​​the bottom of the V-shaped pier based on the wave impact force.

6. The construction method for a large offshore V-shaped pier steel structure according to claim 1, characterized in that, Step S5, pouring concrete, includes: The concrete is poured in layers, with each layer poured from the middle outwards, so that the next layer is poured before the previous layer has set. Each layer of concrete is also vibrated. The layered pouring process uses a pump truck to pour concrete from a floating platform on the side of the foundation.

7. The construction method for a large offshore V-shaped pier steel structure according to claim 1, characterized in that, In step S6, the V-shaped pier construction process includes: The first and second stages of the V-shaped pier were concrete-poured using a pump truck. The third stage was carried out by a crane lifting the hopper and connecting a tremie pipe below the hopper for pouring. A reserved hole was opened in the middle of the formwork in the third stage so that the concrete could be transported to the bottom through the tremie pipe and an attached vibrator was installed at the bottom. The third stage of pouring should be done symmetrically on both sides to avoid safety hazards caused by eccentric stress on the V-shaped pier.

8. The construction method for a large offshore V-shaped pier steel structure according to claim 7, characterized in that, In step S6, after the V-shaped pier construction is completed, a temporary consolidation support structure is installed, including installing several temporary support steel pipes on each V-shaped pier arm. The steel pipes are filled with concrete to provide restraint during external prestressing tensioning so that the deformation value of the V-shaped pier does not exceed the design requirements. After the temporary fixed support structure is installed, it is subjected to external prestressing tension, and the bridge deck structure is installed on the V-shaped pier. After installation, the temporary fixed support structure is removed. The bridge deck structure includes the main beam and precast slab.

9. The construction method for a large offshore V-shaped pier steel structure according to claim 1, characterized in that, In steps S5 and S6, concrete for pouring is prepared in advance, wherein improvements are made to the concrete based on the environmental impact, including: Acquire marine ambient temperature data; When the ambient temperature data is greater than or equal to the preset temperature threshold, a water-reducing agent is added to the concrete to reduce the water-cement ratio and improve crack resistance, or a retarder is added to extend the setting time of the concrete and slow down the rate of cement hydration reaction. The concrete is poured in layers to control the pouring speed within the preset value of the formwork stress calculation. Based on the formwork stress calculation, the pouring height of a single layer is obtained, and vibration is performed after each layer is poured.

10. The construction method for a large offshore V-shaped pier steel structure according to claim 1, characterized in that, In steps S5 and S6, an immersion vibrator is used to compact the concrete structure.

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