Cross-sea bridge heat distribution pipeline along-bridge laying compensator arrangement optimization method

Abstract

The invention discloses a cross-sea bridge heat distribution pipeline along-bridge laying compensator arrangement optimization method. The method comprises the following steps that the type and the position of a compensator are selected; optimizing the structural parameters of the compensator; material and corrosion-resistant design; designing upper and lower bridge nodes and a supporting structure; performing integral system finite element verification and optimization, establishing an integral finite element model comprising a pipeline, a compensator, a bridge and a buttress, simulating stress and deformation of the pipeline in a hot state, a cold state and a bridge operation state, and performing strength evaluation on a high-stress area through a stress linearization method. Adjusting the arrangement position, the structure parameters and the supporting mode of the compensator according to the simulation result; and pre-heating installation and zero stress temperature setting are carried out. According to the method, the overall finite element model including the pipeline, the compensator, the bridge and the independent buttress is established, multi-working-condition simulation in the hot state, the cold state and the operation state is carried out, and accurate prediction and optimization of system stress and deformation are achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of pipeline laying along with bridge, and particularly relates to a method for optimizing arrangement of compensators in pipeline laying along with bridge of a sea-crossing bridge. BACKGROUND

[0002] With the rapid development of coastal areas and islands, the sea-crossing bridge as an important transportation infrastructure has increasingly prominent comprehensive utilization value. The pipeline laying along with bridge as an economic and efficient energy transmission mode is gradually applied to heating and steam supply projects. However, the sea-crossing bridge environment is special, and the bridge structure will produce significant longitudinal, transverse and vertical displacement under the influence of temperature change, vehicle load, wind load and wave action, which poses a severe challenge to the rigidly connected heat pipeline system.

[0003] In the prior art, the arrangement of the heat pipeline compensator depends on experience or simplified calculation, and lacks system analysis of overall coupling. The conventional compensator selection and arrangement often fail to fully consider the dynamic deformation characteristics of the bridge, resulting in insufficient or excessive compensation of the compensator, causing pipeline stress concentration, support structure damage and even leakage accidents. The high salt fog and high humidity conditions of the marine environment put higher requirements on the corrosion resistance of the compensator material, and the traditional protection measures are difficult to meet the long-term service needs.

[0004] In terms of support structure, most existing designs rigidly connect the pipeline support pier with the bridge structure, causing the bridge deformation to be directly transmitted to the pipeline system, aggravating the local stress and affecting the safety of the bridge structure. At the same time, the inaccurate preheating control and unreasonable zero stress temperature setting in the installation process will also cause additional stress of the pipeline in actual operation, reducing the system life.

[0005] Therefore, a systematic and scientific compensator arrangement optimization method is needed, which can comprehensively consider the bridge structure behavior, pipeline thermal characteristics, material durability and installation process, and realize the safe, reliable and long-term operation of the sea-crossing bridge heat pipeline system. SUMMARY

[0006] The application provides a method for optimizing arrangement of compensators in pipeline laying along with bridge of a sea-crossing bridge, aiming to solve the problems of lack of system analysis of overall coupling in the prior art and difficulty of traditional protection measures to meet long-term service.

[0007] The method for optimizing arrangement of compensators in pipeline laying along with bridge of a sea-crossing bridge comprises the following steps:

[0008] Selecting the type and position of the compensator, according to the type of the bridge structure, the span arrangement and the design parameters of the heat pipeline, selecting a spherical compensator or a hinge type compensator, and arranging it at the bridge expansion joint, the area with large displacement at the beam end and the pipeline up-and-down bridge node;

[0009] Optimization of compensator structure parameters, adopting variable diameter pipe structure as the compensator main body, establishing a model for stress and deformation simulation through finite element analysis software, checking the thickness of the variable diameter pipe according to the size of the pipeline axial force through finite element analysis;

[0010] Material and corrosion resistance design, the main body material of the compensator is selected from high-strength stainless steel, and the outer surface of the compensator is treated with corrosion-resistant coating to control the water quality of the medium in the heat pipe;

[0011] Design of upper and lower bridge nodes and support structure, independent concrete piers are arranged at the upper and lower bridge nodes of the pipeline, and the piers are separated from the bridge structure; the pipeline bending section is encapsulated inside the pier;

[0012] Finite element verification and optimization of the overall system, an overall finite element model including the pipeline, compensator, bridge and pier is established, the stress and deformation of the pipeline under hot and cold states and bridge operation state are simulated, the strength of the high stress area is evaluated by linearization method, and the compensator arrangement position, structure parameters and support mode are adjusted according to the simulation results;

[0013] Preheating installation and zero stress temperature setting, preheating installation process is adopted, the zero stress temperature of the pipeline is set as the average of the installation temperature and the design temperature, and the compensator is installed after the pipeline is preheated and elongated.

[0014] Optionally, the rated compensation amount of the compensator is greater than the maximum longitudinal displacement and transverse displacement of the bridge under the design load, and a group of compensators are arranged every A group of compensators are arranged to form segmented compensation.

[0015] Optionally, the thickness of the variable diameter pipe is preliminarily calculated by referring to the calculation method of the inner pressure folded cone shell thickness in GB / T 150.3 standard, and the strength is rechecked by finite element analysis to ensure that the membrane stress is ≤1.5 , the sum of primary and secondary stresses is ≤3 .

[0016] Optionally, the protective coating system on the outer surface of the compensator includes an arc sprayed aluminum coating, an intermediate layer of epoxy cloud iron sealing coating and a surface layer of polysiloxane modified ceramic coating.

[0017] Optionally, the foundation bottom area of the independent concrete pier is determined according to the characteristic value of the foundation bearing capacity, a stainless steel anti-seismic support is arranged at the top of the pier to allow the pipeline to slide axially; the pipeline bending section is encapsulated with C35 micro-expansive concrete, and a closed-cell foam rubber buffer layer and a disc spring group are arranged.

[0018] Optionally, a whole three-dimensional finite element model containing the bridge main structure, the heat pipe system and the independent pier is established, the temperature field, the mechanical load and the bridge deformation in the hot state, the cold state and the operation state are simulated, and the stress linearization evaluation is performed on the transition area of the compensator variable diameter pipe, the pipe upper and lower bridge elbow and the pier connection area.

[0019] Optionally, adjustable zero stress temperature compensators are arranged in the area where the temperature changes sharply, and the pre-tensioning amount is dynamically adjusted within ±5℃ according to the real-time monitoring data.

[0020] Optionally, after the pipe is cooled to the ambient temperature, the X-ray stress tester is used to detect the residual stress in the key weld area, and the residual stress is required to be less than 100MPa. wherein is the yield strength of the material.

[0021] Optionally, adjustable zero stress temperature compensators are arranged in the area where the temperature changes sharply, and the pre-tensioning amount is dynamically adjusted within ±5℃ according to the real-time monitoring data.

[0022] Compared with the prior art, the present application has at least the following beneficial effects:

[0023] The present application establishes a whole finite element model containing the pipe, the compensator, the bridge and the independent pier, performs multi-condition simulation in the hot state, the cold state and the operation state, and realizes the accurate prediction and optimization of the system stress and deformation.

[0024] The present application also reasonably selects the spherical compensator or the hinge type compensator based on the bridge structure type, the span arrangement and the pipe parameters, and optimizes the design of the variable diameter pipe structure, thereby effectively reducing the stress concentration and improving the compensation efficiency and the fatigue life. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The flowchart of the compensator arrangement optimization method for the heat pipe laid along the bridge of the sea-crossing bridge provided by an embodiment of the present application is shown. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application is further described in detail below with reference to the drawings and embodiments.

[0027] The compensator arrangement optimization method for the heat pipe laid along the bridge of the sea-crossing bridge provided by the present application includes the following steps:

[0028] The compensator type and position are determined, the spherical compensator or the hinge type compensator with longitudinal and transverse deformation capacity is selected according to the bridge structure type, the span arrangement and the heat pipe design parameters, and is arranged at the bridge expansion joint, the area where the displacement of the beam end is large and the pipe upper and lower bridge node; the pipe is preferentially arranged in the bridge main beam web or the space below the sidewalk.

[0029] Specifically, the compensator type needs to be selected according to the bridge structure type (such as a cable-stayed bridge or a suspension bridge) and the span arrangement, and a compensator type with multi-directional displacement compensation capability is preferred, including:

[0030] A spherical compensator is suitable for absorbing angular displacement and transverse displacement of a pipeline in three-dimensional space.

[0031] A hinge-type compensator is suitable for angular swing in a plane and is commonly used at a pipeline turning point or on both sides of a bridge expansion joint.

[0032] A transverse + longitudinal composite corrugated compensator has longitudinal compression and transverse shear capability and is suitable for a bridge end large displacement area.

[0033] The selection basis is that the rated compensation amount of the compensator should be greater than the maximum longitudinal displacement (≥200 mm) and the transverse displacement (≥20 mm) of the bridge under the design load, and the pipeline temperature deformation amount (ΔL = L0αΔT) should be considered. wherein, L0 is the original length of the object, α is the linear expansion coefficient of the material, L0 is the original length of the object, ΔT is the change in temperature);

[0034] The optimization of the compensator arrangement position can consider the following positions:

[0035] Bridge expansion joint, compensators are symmetrically arranged on both sides of the expansion joint between the bridge girder and the approach bridge to absorb the longitudinal and transverse displacement of the girder end.

[0036] Girder end displacement concentration area, compensators are arranged in the large deformation area of the bridge span (such as 1 / 3 of the main span of a cable-stayed bridge) to deal with the pipeline deformation caused by vertical deflection of the bridge.

[0037] Pipeline up and down bridge node, compensators are arranged at the bending points where the pipeline transitions from the bridge deck to the bridge pier, and independent piers are matched to decompose the horizontal thrust.

[0038] Pipeline segment interface, a set of compensators are arranged every 200-300 m along the bridge length to form "segment compensation" and avoid displacement accumulation.

[0039] The pipeline arrangement can be selected from the following positions:

[0040] Main girder web, the pipeline is laid in the web of a steel box girder or a concrete box girder to utilize the internal space of the structure and reduce the influence of wind load.

[0041] Under the sidewalk, the pipeline is arranged under the sidewalk on the bridge deck, a hatch is provided, a maintenance access (the cover plate can be opened, the interval is ≤10 m) is reserved, and maintenance is facilitated.

[0042] The pipeline arrangement needs to follow the principle of symmetrical arrangement. When there are two pipelines, they are arranged symmetrically along the center line of the bridge to balance the load and reduce the adverse effects on the bridge structure.

[0043] At the same time, the pipeline arrangement also needs to consider environmental adaptability. The exposed part of the pipeline is equipped with a fairing to reduce wind vibration effects. The installation position of the compensator should avoid bridge drainage outlets and salt mist accumulation areas and be preferentially set in a ventilated and dry area.

[0044] Optimization design of compensator structural parameters. The variable diameter pipe structure is used as the main body of the compensator. Through finite element analysis software, a model is established for stress and deformation simulation. The half-apex angle of the variable diameter pipe is optimized. To , the folding arc radius R is optimized to , and the thickness of the variable diameter pipe is checked by finite element analysis according to the size of the pipeline axial force.

[0045] Specifically, the steps for optimizing the structural parameters of the compensator include:

[0046] Finite element modeling and analysis of the variable diameter pipe structure. A three-dimensional solid model of the variable diameter pipe structure of the compensator is established. Solid186 high-order 20-node hexahedral elements are used for meshing to ensure that the stress concentration area is densely meshed. Symmetric boundary conditions are set, and symmetric constraints are applied to the 1 / 4 model to improve computational efficiency. The applied loads include:

[0047] Internal pressure load: applied to the inner wall of the variable diameter pipe according to the pipeline design pressure (e.g., 2.5 MPa);

[0048] Axial force load: applied to the end face according to the pipeline axial force after preheating installation (e.g., 11000 kN);

[0049] Temperature field coupling: considering the effect of pipeline design temperature (e.g., 130℃) on material properties;

[0050] Through the statics analysis module, the equivalent stress distribution and deformation state of the structure under combined load are calculated.

[0051] The half-apex angle of the variable diameter pipe is optimized, which includes the following steps: The optimal

[0052] range is Within this range, the stress concentration of the structure is significantly reduced, and the length of the variable diameter pipe will not be too long due to the small angle, which will reduce the economy; If the installation space of the corrugated pipe is limited, a corrugated pipe neck-in design can be used to shrink the lowest end of the corrugated pipe below the inner diameter of the cylinder segment to provide installation space for the small-angle variable diameter pipe.

[0053]

[0054] ​The flange arc radius R is optimized, which comprises the following steps: in combination with the feasibility of the forming process, the R value range of 150 mm to 190 mm is recommended, the stress level is ensured, and the stamping forming difficulty caused by too large R is avoided;

[0055] For large diameter pipes (DN≥1200), R≥170mm is preferred to improve the smoothness of the transition zone;

[0056] The thickness of the variable diameter pipe is checked and the strength is verified. Referring to the thickness calculation method of the variable diameter pipe under internal pressure in GB / T150.3 standard, the thickness of the variable diameter pipe is preliminarily calculated:

[0057] The conical shell thickness formula is: ;

[0058] The thickness of the large end transition section is: ;

[0059] The thickness of the small end transition section is: ;

[0060] On the basis of theoretical calculation, the strength of the variable diameter pipe under the combined load of internal pressure + axial force is verified by finite element analysis, and the stress linearization path in the thickness direction of the large end arc transition of the variable diameter pipe is extracted;

[0061] Assess the membrane stress , assess the sum of the first + second stress (limit 489MPa), if the finite element result shows that the stress is out of limit, increase the thickness of the variable diameter pipe or upgrade the material grade;

[0062] Structural parameter optimization, establish a thickness multi-parameter optimization model, take the minimum equivalent stress as the objective function, take the installation space and process cost as the constraint conditions, determine the optimal parameter combination through response surface analysis method, ensure that the structure is lightweight under the premise of meeting the strength requirement, evaluate the fatigue life of the optimized structure, and verify its long-term service performance in the bridge vibration environment;

[0063] Material and corrosion resistance design: the main body material of the compensator is selected from nickel-based high-temperature alloy or high-strength stainless steel containing molybdenum and chromium elements; the outer surface of the compensator is treated with anti-corrosion coating; the water quality in the heat pipe is controlled, the chloride ion concentration is ≤50mg / L, and the pH value is maintained at ;

[0064] Specifically, the main body material of the compensator should preferably be Inconel 625 or Hastelloy C-276, which have excellent creep resistance, fatigue resistance and chloride stress corrosion resistance below 650℃; or high-performance stainless steel can be selected, such as 316L or 254SMO ultra-low carbon austenitic stainless steel with a molybdenum content ≥6%, which can effectively resist marine atmospheric pitting and crevice corrosion.

[0065] The key performance indicators for the above materials are as follows:

[0066] High-temperature strength: At a working temperature of 150℃, the yield strength of the material is ≥250MPa and the tensile strength is ≥550MPa;

[0067] Creep resistance: Creep limit ≥100,000 hours at 150℃ and 2.5MPa pressure;

[0068] Fatigue life: in Number of cycles under stress amplitude Second-rate;

[0069] Surface protective coating design, wherein the coating system consists of:

[0070] Base layer: Arc-sprayed aluminum coating, thickness This forms a sacrificial anode protection;

[0071] Intermediate layer: Utilizes an epoxy micaceous iron oxide sealing coating, with a thickness of [missing information]. It fills the pores in the substrate and enhances adhesion;

[0072] Top layer: Polysiloxane modified ceramic coating, thickness It is resistant to ultraviolet rays, salt spray, and high temperature (long-term operating temperature ≤200℃).

[0073] At the same time, special areas need to be protected. For example, for easily corroded parts such as the trough of the compensator and the weld area, laser cladding of Inconel 625 alloy should be used, with a cladding layer thickness ≥0.8mm.

[0074] A solid lubricating coating of PTFE impregnated with MoS2 is applied to the telescopic movement parts, with a thickness of [missing information]. It combines corrosion prevention and friction reduction;

[0075] Construct a material-structure collaborative corrosion protection system. Install insulating flanges or non-metallic gaskets at the connection between the compensator and the carbon steel pipeline to block galvanic corrosion. Install drainage holes (Φ6~Φ8mm) at the trough of the compensator to avoid liquid accumulation corrosion.

[0076] Monitoring and maintenance: Electrochemical corrosion monitoring probes are pre-embedded in key parts of the compensator to monitor corrosion potential and current in real time;

[0077] The upper and lower bridge nodes are designed with support structures. Independent concrete support piers are arranged at the upper and lower bridge nodes of the pipeline. The support piers are separated from the bridge structure. The pipeline bending section is encapsulated inside the support piers. The size of the support piers is determined according to the calculation results of the thrust force.

[0078] The water pressure thrust acting on the part where the direction of the pipeline changes is calculated by the formula: where P is the pipeline test pressure (1.5 times the working pressure), A is the cross-sectional area of the pipeline, and θ is the elbow angle (45°).

[0079] The deformation stress thrust acting on the part that restricts or constrains the free movement of the pipeline is calculated according to the compensator stiffness K (such as 262 N / mm) and the maximum displacement amount (such as 13 mm).

[0080] Total horizontal thrust:

[0081] The independent concrete support pier structure is a C40 reinforced concrete cast-in-place structure, completely separated from the bridge pile cap, with a spacing of ≥500 mm. The base area is determined according to the characteristic value of the foundation bearing capacity (fak≥180 kPa) to ensure uniform stress distribution on the base. The typical size is selected: 3.5 m in length, 3.3 m in width, and 2.8 m in height. Stainless steel anti-seismic supports (model JQZ-GD-1500) are arranged on the top to allow the pipeline to slide axially. HRB400Φ25@150mm double-layer double-direction reinforcement is used, with additional shear reinforcement Φ16@200mm arranged at 45°. Steel frames (H200×200×8×12) are arranged in the thrust action area to enhance the local resistance to punching shear.

[0082] The encapsulation structure selected for the pipeline bending section is: C35 micro-expansion concrete is used for integral pouring at the elbow and the adjacent 2m straight pipe section to form a protective shell with a thickness of 400mm. Polypropylene fibers (0.9kg / m³) are mixed in the concrete to improve the crack resistance.

[0083] At the same time, shock absorption design is added. A closed-cell foam rubber buffer layer (30mm thick) is arranged between the pipeline and the encapsulated concrete. A disc spring set (stiffness coefficient 50kN / mm) is embedded at the center of the elbow curvature to absorb impact energy.

[0084] The bridge interface is finely processed. A 2000×1500mm rectangular hole is opened in the main beam flange plate at the corresponding position of the support pier. A box-shaped reinforcement frame (t=20mm Q345 steel plate) is arranged around the hole to disperse stress concentration.

[0085] ​​Enhanced transition connection: SCB-80 type expansion joint device is arranged between the top surface of the support pier and the bridge pavement layer to allow relative displacement, and stainless steel drainage channels are arranged around to guide rainwater away from the support pier area;

[0086] Strain monitoring points (3 on each surface, a total of 12) are arranged on the surface of the support pier to monitor the stress state of the concrete in real time, displacement sensors are installed at the interface between the support pier and the pipeline to monitor the pipeline slip amount, and an ultrasonic detection tube is reserved to facilitate non-destructive testing of the pipeline in the enclosed section;

[0087] Whole system finite element verification and optimization: a whole finite element model including the pipeline, compensator, bridge and support pier is established to simulate the stress and deformation of the pipeline under hot, cold and bridge operation conditions; the strength of the high stress area is evaluated by the stress linearization method; the compensator arrangement position, structure parameters or support mode are adjusted according to the simulation results;

[0088] Specifically, the steps of whole system finite element verification and optimization include:

[0089] S1: establishment of whole finite element model, wherein:

[0090] Model range: a whole three-dimensional model including the main structure of the bridge (main girder, bridge tower, support), heat pipeline system (including compensator, support), and independent concrete support pier is established.

[0091] Element type selection: SHELL181 shell element is used to simulate steel box girder for the main girder of the bridge; PIPE289 element and SOLID186 solid element are used to model the pipeline and compensator; SOLID185 element is used for the support pier, and BEAM188 element is used for the embedded reinforcement.

[0092] Contact definition: friction contact is set between the pipeline and the support ( ); spring element is set between the support pier and the foundation to simulate the soil-structure interaction;

[0093] S2: multi-condition load simulation, simulating the following conditions:

[0094] Temperature condition: hot condition: pipeline temperature 150℃, bridge temperature 35℃; cold condition: pipeline temperature 10℃, bridge temperature -10℃; zero stress condition: pipeline temperature 80℃ (preheating installation temperature);

[0095] Mechanical load: internal pressure load: 2.5MPa uniformly distributed; bridge deformation: longitudinal displacement ±220mm, transverse displacement ±18mm, and vertical deflection 314mm of the main girder are applied at the beam end; wind load: according to the basic wind pressure of 50-year return period Calculation;

[0096] Load combinations: Combination 1: Hot state + internal pressure + maximum bridge elongation; Combination 2: Cold state + internal pressure + maximum bridge contraction; Combination 3: Operational state (temperature cycle + vehicle dynamic load).

[0097] S3: Stress analysis and strength assessment

[0098] First, identify the high-stress areas, including: the transition area of ​​the compensator reducer; the bends at the top and bottom of the pipeline; and the connection area between the support and the pipeline.

[0099] Stress linearization: Set stress assessment paths (path length = wall thickness, number of segments ≥ 10) at key locations, and extract the membrane stress of each path. Thin film + bending stress Peak stress;

[0100] Strength assessment standard, according to JB4732 specification: Overall membrane stress (K=1.0, =163MPa); Local membrane stress Primary and secondary stress ≤3 ;

[0101] S4: System optimization iteration, including:

[0102] The layout of the compensators was optimized. If the pipeline stress exceeded the limit, compensators were added in the middle 1 / 3 area of ​​the span, and the spacing was shortened from 300m to 200m. The installation angle of the compensators was adjusted to make them best match the direction of bridge deformation.

[0103] Structural parameters were corrected based on stress cloud diagrams. For compensators in high-stress areas, the half-apex angle was optimized from 17° to 14°, and the pier size was increased from 3.5m×3.3m to 3.8m×3.5m to improve lateral stiffness.

[0104] The support system was improved by replacing fixed supports with guide supports, releasing lateral constraints, and adding hydraulic dampers (damping coefficient) in sections of the pipeline with significant vibration. );

[0105] S5: Special analysis and validation, mainly including:

[0106] Modal analysis was performed to calculate the first 10 modes of the system, ensuring that the natural frequency of the pipeline avoids the main excitation frequency of the bridge (0.5-3.0Hz).

[0107] Fatigue life assessment: Based on Miner's linear cumulative damage theory, the fatigue life of the compensator under 2 million thermal cycles is calculated, with a focus on the trough area, requiring a safety factor ≥15;

[0108] S6: Optimization effect verification. The optimized system should meet the following requirements:

[0109] The maximum equivalent stress in the pipeline is ≤145MPa;

[0110] The maximum compressive stress in the concrete of the support pier is ≤16MPa;

[0111] The displacement absorption efficiency of the compensator is ≥92%;

[0112] The system's fundamental frequency should be ≥3.5Hz, avoiding the main resonance region;

[0113] Through overall system finite element verification and optimization, the maximum equivalent stress of the heating pipeline under various working conditions of the bridge is reduced, the stress non-uniformity is reduced from 1.8 to below 1.3, the system safety factor reaches 2.1, and the safety and reliability of the heating pipeline system of the cross-sea bridge are improved.

[0114] Preheating installation and setting the zero-stress temperature: a preheating installation process is adopted, and the zero-stress temperature of the pipeline is set as the average of the installation temperature and the design temperature; the compensator is installed after the pipeline has been preheated and expanded.

[0115] Zero-stress temperature calculation, including:

[0116] Basic calculation formula: Theoretical zero-stress temperature: ;

[0117] in: The lowest ambient temperature in recent years (taken as -5℃). Pipeline design temperature (150℃). Additional temperature rise to overcome soil friction (take 15℃);

[0118] Engineering correction formula: Actual zero stress temperature:

[0119] in, Soil resistance coefficient (taken as 0.8), L: Pipeline length (taken as the value of the most unfavorable pipe section). : Coefficient of friction between pipeline and soil (taken as 0.4);

[0120] The preheating installation process includes the following steps:

[0121] Before preheating, set up temperature monitoring points (K-type thermocouples) every 50m along the straight section of the pipeline and install temporary tensioning devices (hydraulic jack assembly, thrust accuracy ±2%).

[0122] Segmented preheating control, including the first stage: heating to 50℃ at a rate of ≤10℃ / h and holding at that temperature for 2h to eliminate installation stress;

[0123] Second stage: Continue heating to the zero-stress temperature at a rate of ≤5℃ / h, and monitor the temperature gradient throughout the process, which is ≤15℃ / m.

[0124] Key control indicators include: axial elongation of the pipeline. ;

[0125] The actual elongation must deviate from the axial elongation of the pipe by ≤±3%;

[0126] Precise installation of compensators includes: timing of installation, when the pipe temperature stabilizes at... Installation should begin after the temperature is within ±2℃ and the duration is ≥1 hour. During installation, a laser rangefinder should be used to monitor the compensator gap in real time to ensure accurate installation position.

[0127] Prestressing: Apply a compression of 50% of the design displacement to the compensator (for hot working conditions), tighten the connecting bolts using the torque control method, and apply the load to the design torque (200 N·m ± 5%) in three stages.

[0128] Stress state verification and adjustment, including cold stress verification, involves using an X-ray stress meter to detect residual stress in critical weld areas after the pipeline has cooled to ambient temperature. The residual stress must be ≤0.3. (Material yield strength);

[0129] Thermal simulation: 80℃ hot water is circulated for 24 hours, and the displacement of the compensator is monitored. The actual displacement should deviate from the theoretical value by ≤8%.

[0130] In addition, it also has special working condition response measures, including:

[0131] Diurnal temperature difference compensation: In areas with drastic temperature changes (such as near bridge towers), an adjustable zero-stress temperature compensator is installed to dynamically adjust the pre-tension amount within ±5℃ based on real-time monitoring data.

[0132] For long-term stress relaxation control, stress scans are performed every two weeks during the initial operation period (first 3 months). If stress relaxation ≥15% is found, local electric heat tracing compensation is used to restore the design stress state.

[0133] Finally, data recording is required throughout the entire process. The data includes automatically recording key parameters such as the temperature rise curve, elongation, and compensator installation gap, forming a preheating installation data package containing at least 1,000 sets of valid data.

[0134] The overall acceptance criteria must meet the following: Temperature control accuracy: ±3℃; Pipeline alignment deviation: ≤2mm / m; Compensator installation angle error: ≤0.5°.

[0135] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. An optimized method for the arrangement of compensators for thermal pipelines laid along the bridge in cross-sea bridges, characterized in that... Includes the following steps: Select the type and location of the compensator. Based on the bridge structure type, span arrangement and thermal pipeline design parameters, select spherical compensators or hinged compensators and place them at bridge expansion joints, areas with large beam end displacement, and pipeline nodes at the bridge entrance and exit. The structural parameters of the compensator were optimized, and a variable diameter pipe structure was adopted as the main body of the compensator. A model was established using finite element analysis software to simulate stress and deformation. The thickness of the variable diameter pipe was checked by finite element analysis based on the magnitude of the axial force of the pipeline. Materials and corrosion-resistant design: The main body of the compensator is made of high-strength stainless steel, and the outer surface of the compensator is treated with an anti-corrosion coating to control the water quality of the medium in the thermal pipeline. The design of the upper and lower bridge nodes and supporting structures involves setting independent concrete supports at the upper and lower bridge nodes of the pipeline, with the supports separated from the bridge structure; the pipeline bending section is enclosed inside the supports. The overall system was verified and optimized using finite element methods. A finite element model was established, including pipelines, compensators, bridges, and supports. The stress and deformation of the pipelines under hot, cold, and bridge operation conditions were simulated. The strength of high-stress areas was evaluated using the stress linearization method. The compensator layout, structural parameters, and support methods were adjusted based on the simulation results. Preheating installation and setting the zero-stress temperature: The preheating installation process is adopted, and the zero-stress temperature of the pipeline is set as the average of the installation temperature and the design temperature. The compensator is installed after the pipeline has been preheated and expanded.

2. The method for optimizing the arrangement of compensators for cross-sea bridge thermal pipelines as described in claim 1, characterized in that, The rated compensation capacity of the compensator is greater than the maximum longitudinal and lateral displacements of the bridge under design loads, and is calculated along the bridge length at intervals of [missing information]. Set up a set of compensators to form segmented compensation.

3. The method for optimizing the arrangement of compensators for cross-sea bridge thermal pipelines as described in claim 1, characterized in that, The thickness of the reducing pipe was initially calculated according to the calculation method for the thickness of the conical shell with internal pressure in GB / T 150.3 standard, and the strength was verified by finite element analysis to ensure that the membrane stress ≤ 1.

5. The sum of the first and second stresses is ≤3 .

4. The method for optimizing the arrangement of compensators for cross-sea bridge thermal pipelines as described in claim 1, characterized in that, The compensator's outer surface protective coating system includes a base layer of arc-sprayed aluminum coating, an intermediate layer of epoxy micaceous iron oxide sealing coating, and a top layer of polysiloxane-modified ceramic coating.

5. The method for optimizing the arrangement of compensators for cross-sea bridge thermal pipelines laid along the bridge as described in claim 1, characterized in that, The foundation area of ​​the independent concrete support is determined according to the characteristic value of the bearing capacity of the foundation. Stainless steel seismic bearings are installed on the top of the support to allow axial sliding of the pipeline. The pipeline bend is encapsulated with C35 micro-expansion concrete and a closed-cell foam rubber buffer layer and disc spring assembly are installed.

6. The method for optimizing the arrangement of compensators for thermal pipelines laid along the bridge in a cross-sea bridge according to claim 1, characterized in that, A three-dimensional finite element model was established, including the main structure of the bridge, the thermal pipeline system, and the independent supports. The temperature field, mechanical load, and bridge deformation were simulated under hot, cold, and operational conditions. The stress linearization evaluation was carried out in the transition zone of the compensator reducer, the bends of the pipelines above and below the bridge, and the connection area of ​​the supports.

7. The method for optimizing the arrangement of compensators for thermal pipelines laid along the bridge in a cross-sea bridge according to claim 1, characterized in that, An adjustable zero-stress temperature compensator is installed in areas with drastic temperature changes, and the pre-tension amount is dynamically adjusted within ±5℃ based on real-time monitoring data.

8. The method for optimizing the arrangement of compensators for thermal pipelines laid along the bridge in a cross-sea bridge according to claim 1, characterized in that, After the pipeline cools to ambient temperature, an X-ray stress analyzer is used to detect the residual stress in the critical weld area. The residual stress is required to be... ,in This represents the yield strength of the material.

9. The method for optimizing the arrangement of compensators for cross-sea bridge thermal pipelines as described in claim 1, characterized in that, An adjustable zero-stress temperature compensator is installed in areas with drastic temperature changes, and the pre-tension amount is dynamically adjusted within ±5℃ based on real-time monitoring data.

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