Prestressed large-span composite steel beam and construction method thereof

Abstract

The invention discloses a prestressed large-span composite steel beam and a construction method thereof, and relates to the field of large-span structural engineering. The steel beam comprises a main steel beam body, a concrete laminated layer and a prestress regulation and control system, the main steel beam body is divided into a midspan and support functional area, the prestress regulation and control system comprises a first prestress unit, a second prestress unit and an adjustable anchoring assembly, the two units are arranged in a differentiated mode and tensioned in stages, and the adjustable anchoring assembly supports repeated adjustment. And the structure state monitoring unit is matched to form closed-loop regulation and control. The construction method comprises the steps of steel beam splicing and partitioning, prestress unit arrangement, staged tensioning and service period regulation and control. According to the method, refined optimization of stress in the construction and bridge forming stages is achieved, and the long-term service safety and construction adaptability of the structure are improved.

Description

Technical Field

[0001] This invention relates to the field of large-span structural engineering technology, specifically to a prestressed large-span composite steel beam and its construction method. Background Technology

[0002] With the rapid development of modern engineering construction, the demand for projects such as long-span bridges, industrial plants, and large public buildings is increasing, placing more stringent requirements on the span coverage capacity, load-bearing capacity, construction efficiency, and long-term service safety of structural components. Currently, most long-span steel beams or steel-concrete composite beams widely used in engineering adopt a constant prestressing design. Their prestressing arrangement is singular and fixed, which can only achieve general stress adjustment and is difficult to finely control according to the differentiated stress characteristics of different spans along the span direction. This leads to frequent technical defects in practical applications, such as excessive mid-span deflection, stress concentration in the support area, and insufficient utilization of material mechanical properties, affecting the overall load-bearing efficiency and service safety of the structure.

[0003] Furthermore, the prestressing of existing prestressed composite steel beams is mostly a one-time construction operation, and the prestress state is fixed after construction, making secondary adjustment or dynamic optimization impossible. Once the structure enters service, its stress state continuously changes due to factors such as load variations, concrete creep, material shrinkage, and environmental erosion. Current technologies lack effective prestress compensation methods, making it difficult to cope with the adverse effects of these changes and severely limiting the long-term service performance and safety stability of the structure. Therefore, there is an urgent need to develop a new type of prestressed large-span composite steel beam system and supporting construction methods that features a rational structural form, adjustable and controllable prestressing, strong construction adaptability, and the ability to achieve full life-cycle stress optimization. Summary of the Invention

[0004] The purpose of this invention is to provide a prestressed large-span composite steel beam and its construction method, so as to solve the problem that the existing lack of effective prestress compensation means makes it difficult to cope with the adverse effects of the above-mentioned changes.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: A prestressed large-span composite steel beam includes: a main steel beam extending along the span direction; and a concrete composite layer disposed above the main steel beam, wherein the concrete composite layer and the main steel beam are firmly connected by shear-resistant connecting members to form a combined load-bearing structure. The prestress control system includes at least a first prestress unit and a second prestress unit, wherein the first prestress unit and the second prestress unit are arranged differently along different stress areas of the main steel beam and have different functional attributes. The first prestressed unit is located at the lower edge and / or web area of ​​the main steel beam and is arranged in a non-linear or segmented manner along the length of the main steel beam. It is used to precisely control the initial alignment and internal forces of the main steel beam during the construction stage after the steel beam is erected. The second prestressed unit is set in the concrete composite layer and / or the steel-concrete composite area, and is used to optimize and control the stress performance of the composite steel beam during the bridge construction stage after the concrete composite layer reaches the set strength. The prestress control system includes at least one adjustable anchoring component, which is configured to allow the corresponding prestressed unit to be repeatedly tensioned, released or adjusted during the construction and / or operation phases, so that the prestressed large-span composite steel beam is stably in a preset stress state at different stages. The main steel beam is divided into at least a mid-span functional zone and a support functional zone along the span direction. The arrangement of prestressed units, the density of shear connection members, and the prestressing control strategy in different functional zones are independent of each other and adapted to the stress requirements of the corresponding areas, so as to achieve zoned stress optimization during the construction stage and the completed bridge stage.

[0006] In a further embodiment, the adjustable anchoring assembly includes a multi-level locking structure and a releasable connection structure. The multi-level locking structure is used to stably maintain the tension state of the prestressed unit, and the releasable connection structure is used to release the lock to achieve secondary adjustment, so that the corresponding prestressed unit can be re-tensioned or the prestress level can be precisely adjusted at least once in the subsequent construction or operation phase after the initial tensioning is completed.

[0007] In a further embodiment, the first prestressed unit is arranged in a zigzag, curved, or segmented variable height shape along the length of the main steel beam. Its prestressing path is precisely matched and set according to the actual bending moment distribution of the main steel beam along the span direction, ensuring the pertinence and effectiveness of internal force control during the construction stage.

[0008] In a further embodiment, the mid-span functional zone is the core area for stiffness and deflection control, and the arrangement density of its prestressed units and shear connection members is higher than that of the corresponding members in the support functional zone, so as to enhance the structural stiffness and strictly control the mid-span deflection; the support functional zone is the internal force release optimization zone, and the arrangement density of its shear connection members is lower than that in the mid-span functional zone, or a rotation-allowed connection structure is adopted, thereby effectively reducing the secondary internal forces of the composite structure.

[0009] In a further embodiment, the first prestressed unit is tensioned after the main steel beam is erected and the assembly accuracy meets the standard, in order to form a stable initial internal force state during the construction phase and ensure that the structural alignment is controllable during construction; the second prestressed unit is tensioned after the concrete composite layer reaches the designed strength and the curing quality is qualified, in order to form a target stress state that meets the design requirements during the bridge completion phase and improve the overall load-bearing capacity of the structure.

[0010] In a further embodiment, the prestress control system also includes a structural state monitoring unit, which is used to acquire in real time the deflection, strain, or internal force information of the main steel beam and the concrete composite layer during the construction and / or operation stages. Based on the monitoring data of the structural state monitoring unit, the prestress of the adjustable anchoring component is dynamically adjusted to form a "monitoring-control" closed-loop system.

[0011] In a further proposed approach, the prestressed units in different functional zones are designed differently in terms of tensioning sequence, tension force magnitude, and prestress level. The mid-span functional zone prioritizes meeting the core requirements for deflection control, while the support functional zone prioritizes meeting the requirements for internal force redistribution optimization, thereby achieving precise matching of the mechanical objectives of each functional zone.

[0012] In a further embodiment, the main steel beam is assembled from multiple standardized steel beam segments. Each steel beam segment has a pre-set prestressed channel and anchorage interface during the factory prefabrication stage to ensure on-site assembly accuracy and connection reliability. The prestressed unit is activated as a whole or in segments after on-site assembly, thereby improving construction efficiency and project adaptability.

[0013] A construction method for prestressed large-span composite steel beams, applicable to the aforementioned prestressed large-span composite steel beams, includes the following steps: S1. Assemble or erect the main steel beams according to the design requirements. After passing the accuracy test, divide the main steel beams into the mid-span functional area and the support functional area along the span direction. S2. Based on the stress characteristics and control requirements of different functional areas, the first prestressed unit and the second prestressed unit are arranged differently in the main steel beam or between the main steel beam and the concrete composite layer, and adjustable anchors are precisely installed at the ends of each prestressed unit. S3. Before pouring the concrete composite layer, the first prestressed unit is tensioned in the first stage. The tensioning parameters are set according to the internal force control requirements of the construction stage to form an initial prestressed state for controlling the structural alignment and deflection during the construction stage. S4. Complete the pouring and curing of the concrete composite layer according to the construction specifications to ensure that the main steel beam and the concrete composite layer firmly form a combined load-bearing structure. S5. After the concrete composite layer reaches the designed strength, the second prestressed unit is tensioned in the second stage. The tensioning parameters are set according to the stress optimization requirements of the completed bridge stage to optimize the internal force distribution in the mid-span and support areas of the completed bridge stage. S6. During the service phase of the structure, structural deformation or stress parameters are acquired in real time by a structural condition monitoring device installed on the main steel beam and / or concrete composite layer. Based on the structural condition monitoring results, at least one set of prestressed units are dynamically adjusted using the adjustable anchors to achieve coordinated control of prestress during the construction phase, bridge completion phase, and service phase, thereby ensuring the long-term service performance and safety of the structure.

[0014] The present invention has the following beneficial effects: This invention achieves precise matching between stiffness and deflection control in the mid-span region and internal force release in the support region through differentiated design of functional zones. Combined with the phased tensioning of the double prestressed units, it realizes the synergistic optimization of stress during the construction and completed bridge stages. The multi-level locking and release structure of the adjustable anchoring component enables repeated adjustment of prestress, forming a closed-loop control with the structural condition monitoring unit, effectively addressing the adverse effects of load changes and material creep and shrinkage during service. The factory prefabrication and on-site assembly mode of the main steel beams not only ensures construction accuracy and structural reliability, but also improves construction adaptability and efficiency. It comprehensively solves the problems of insufficient precision in prestress control and limited long-term service performance of traditional large-span steel beams, and achieves simultaneous improvement in structural span capacity, load-bearing capacity and safety stability. Attached Figure Description

[0015] Figure 1 This is a structural block diagram of the invention; Figure 2 This is a diagram illustrating the specific steps of the construction method in this invention.

[0016] In the figure: main steel beam 1, concrete composite layer 2, adjustable anchoring assembly 31, structural condition monitoring unit 32, first prestressing unit 3a, and second prestressing unit 3b. Detailed Implementation

[0017] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0018] (I) Implementation details of composite steel beam structure Main steel beam 1: Made of Q355 or Q420 high-strength steel, it is prefabricated in the factory from 3-5 standardized steel beam segments. The segment length is set at 15-25m depending on transportation and construction conditions. The segments are connected and fixed by high-strength bolts or welding. The connection surfaces are pre-set with positioning pins and sealing structures to ensure assembly accuracy ≤2mm. Main steel beam 1 is divided into a mid-span functional area and a support functional area along the span direction. The length of the mid-span functional area is 1 / 3-1 / 2 of the span, and the length of the support functional area is 5-8m.

[0019] Concrete composite layer 2: Made of C50-C60 self-compacting concrete, with a thickness of 180-250mm, internally reinforced with a double-layer bidirectional steel mesh (steel diameter 12-16mm, spacing 150-200mm). Concrete composite layer 2 is connected to the main steel beam 1 by shear studs (diameter 19-22mm, height 100-120mm). The density of shear studs in the mid-span functional area is 8-10 studs / m², and the density in the support functional area is 3-5 studs / m². Rotatable hinge joints are provided at the ends of the support functional areas.

[0020] Prestress control system: The first prestressed unit 3a: adopts Φs15.2 high-strength low-relaxation steel strand, which is set in the prestressed duct at the lower edge of the main steel beam 1 and arranged in a curved shape along the length of the main steel beam. The radius of the curve is set to 150-200m according to the bending moment distribution, and the tension control stress is 0.75fptk (fptk=1860MPa).

[0021] The second prestressed unit 3b uses Φs15.2 high-strength, low-relaxation steel strands, which are installed in the embedded pipes within the concrete composite layer 2 and arranged in a straight line along the span direction. The tension control stress is 0.70fptk.

[0022] Adjustable anchoring component 31: includes a primary locking nut, a secondary anti-loosening washer and a hydraulic release device, with an anchoring efficiency coefficient ≥0.95, repeated tensioning times ≥3 times, and prestress adjustment accuracy ≤5%.

[0023] Structural condition monitoring unit 32: It adopts fiber optic grating sensors (monitoring strain, accuracy ±2με) and displacement gauges (monitoring deflection, accuracy ±0.1mm). One monitoring point is set up every 5-8m in the mid-span functional area, and 2-3 monitoring points are set up near each support in the support functional area. The sensor data is uploaded to the control terminal in real time through a wireless transmission module. Adjustable anchoring component 31 uses "dual-stage locking + hydraulically controllable release" as its core structure. Through the coordinated action of the primary locking nut, the secondary anti-loosening washer, and the hydraulic release device, it realizes the entire process of initial tensioning and locking of the prestressed unit, repeated tensioning and supplementary tensioning, controllable release and unloading, and precise adjustment and locking. The specific working mechanism is explained in detail according to different scenarios: The entire assembly is installed on the anchorage end bearing plate of the main steel beam 1 or the concrete composite layer 2. The installation positions and functions of each component are as follows: Primary locking nut: It is directly fitted onto the anchor at the end of the prestressed steel strand and threadedly connected to the bearing plate. It provides the "main locking" function for prestressing and bears more than 90% of the prestressed load. Secondary anti-loosening washer: Located between the primary locking nut and the pressure plate, it adopts a disc spring + anti-slip tooth structure, and uses the spring preload to eliminate thread clearance and prevent the primary locking nut from loosening naturally due to vibration and creep; Hydraulic release device: It is arranged in a ring between the first-stage locking nut and the pressure plate (without direct contact with the steel strand), with a built-in miniature hydraulic cylinder and a push piston. It is powered by an external hydraulic pump and is used to controllably push open the first-stage locking nut to achieve the "unlocking" function. Auxiliary components include a displacement sensor (monitoring the nut's pushing distance) and a pressure sensor (providing feedback on locking pressure), which work in conjunction with the structural status monitoring unit 32 to ensure adjustment accuracy.

[0024] The component's workflow strictly matches the "initial tensioning, repeated tensioning, controlled release, and precise locking" requirements of the prestressed unit, covering control scenarios during the construction, bridge completion, and service phases. 1. Initial tensioning and locking (initial fixation during construction / bridge completion phase) Applicable scenarios: Initial tensioning and fixing of the first prestressed unit (main steel beam construction stage) and the second prestressed unit (bridge completion stage after concrete reaches the required standard); Working steps: 1. After the prestressed steel strands are threaded, apply the design tension force (e.g., 0.75fptk for the first unit) using a through-type jack. After tensioning to the preset stress value, maintain the jack load stable. 2. Tighten the primary locking nut manually or with an electric wrench until the nut is in contact with the bearing plate. Confirm the locking torque with a torque wrench (match the prestressed load to avoid over-tightening or under-tightening). 3. After tightening the primary nut, the disc spring of the secondary anti-loosening washer is compressed, generating a continuous preload. The anti-slip teeth are embedded in the surface of the bearing plate, forming a "mechanical anti-loosening" to prevent the nut from loosening. 4. Remove the jack. At this time, the component achieves stable prestressing locking through "primary nut bearing + secondary washer anti-loosening", with an anchoring efficiency coefficient ≥0.95.

[0025] 2. Repeated tensioning (supplementary tensioning): Adjustment when stress is insufficient during service. Applicable scenarios: When the prestress decreases due to creep or cable relaxation during the service life of the structure, or when excessive deflection at mid-span is detected and prestress needs to be added; Working steps: 1. The structural condition monitoring unit 32 feeds back a "insufficient prestress" signal (e.g., strain value is lower than the preset threshold), and the external hydraulic pump is connected to the hydraulic release device; 2. Start the hydraulic pump and inject pressurized oil into the miniature hydraulic cylinder of the hydraulic release device. The jacking piston simultaneously lifts the first-stage locking nut (the jacking distance is monitored in real time by the displacement sensor, and only 3-5mm needs to be opened to allow the nut to disengage from the pressure plate and release the lock); 3. Keep the jacking force of the hydraulic release device stable (to prevent the first-stage nut from retracting), reinstall the through-hole jack, and perform supplementary tensioning on the steel strand until the stress reaches the preset target value (e.g., supplemented to 100% of the design value); 4. After the supplementary tensioning is completed, maintain the jack load, turn off the hydraulic pump, and the jacking piston of the hydraulic release device retracts. The first-stage locking nut re-adheres to the pressure plate under the action of prestress; 5. Tighten the first-stage locking nut again, and the second-stage anti-loosening washer is recompressed to prevent loosening, completing the repeated tensioning. This process can be repeated ≥3 times, and the prestress deviation after each supplementary tensioning is ≤5%.

[0026] 3. Controllable release (unloading): Adjustable in case of stress concentration or overload. Applicable scenarios: stress concentration in the support area, excessive prestress accumulation after temporary heavy load, requiring appropriate removal of some prestress; Working steps: 1. The monitoring unit sends a "stress exceeding standard" signal, connects the hydraulic release device to the hydraulic pump, and simultaneously installs a pressure sensor between the jack and the steel strand (to monitor stress changes in real time during the unloading process); 2. Start the hydraulic pump, push the piston to lift the first-stage locking nut, and release the lock; 3. Slowly reduce the pushing force of the hydraulic release device, and the steel strand is slowly unloaded under the action of structural rebound. The pressure sensor provides real-time feedback of the stress value until the preset unloading target is reached (e.g., from 165MPa to 150MPa); 4. After unloading to the target value, maintain the pushing force of the hydraulic release device, retighten the first-stage locking nut, and use the second-stage anti-loosening washer to complete the controllable release. The stress change is stable and without sudden changes during the unloading process (to avoid structural impact).

[0027] Precision Adjustment: Precision Calibration After Tensioning / Release Through closed-loop control using a "monitoring unit + sensor" approach, the prestress deviation after adjustment is ensured to be ≤5%. Calibration method: 1. After each tensioning / release, the structural status monitoring unit 32 collects the strain and deflection data of the steel strands in real time and calculates the actual prestress value; 2. If the actual value deviates from the preset value by more than 3%, repeat the "unlock-fine-adjust-lock" process: slightly open the first-level nut, tension / release slightly with the jack (adjustment amount ≤ 2% of the design value), and then lock; 3. Until the monitoring data shows that the deviation between the prestress value and the preset value is ≤ 5%, the accurate calibration is completed.

[0028] Traditional anchoring components can only be locked once and cannot be unlocked for adjustment. However, this component achieves a closed loop of tensioning, locking, adjusting and re-locking through dual-level locking and hydraulically controllable unlocking. This ensures the stability of prestress during long-term service and can cope with the adverse effects of construction errors, environmental changes and load fluctuations, perfectly matching the core requirement of "full life cycle prestress control".

[0029] (II) Implementation steps of construction methods Step S1: Main steel beam assembly and functional zoning. The prefabricated steel beam segments are transported to the construction site and hoisted and erected using crawler cranes (lifting capacity ≥300t). The segment assembly sequence proceeds from the mid-span to both ends. After assembly, the alignment is checked using a laser rangefinder and a level to ensure that the mid-span pre-camber deviation is ≤5mm. After passing the test, the boundaries of the mid-span functional zone and the support functional zone are marked along the span direction.

[0030] Step S2: Prestressed Unit Layout and Adjustable Anchor Installation. Prestressed ducts (diameter 80-100mm, wall thickness 5-8mm) are pre-embedded in the main steel beam 1 according to the design drawings. The pre-embedded ducts are fixed in the formwork of the concrete composite layer 2, ensuring that the duct axis deviation is ≤3mm / m. The steel strands of the first prestressed unit 3a and the second prestressed unit 3b are threaded one by one, and adjustable anchor components 31 are installed at the ends. The anchoring surface is perpendicular to the steel strand axis, with a perpendicularity deviation ≤0.5°.

[0031] Step S3: Tensioning of the first prestressed unit Before pouring the concrete composite layer, the first prestressed unit 3a is tensioned using a through-hole jack (rated tension force ≥ 5000kN). The tensioning sequence is symmetrical tensioning from both ends to the mid-span, in four stages (25%→50%→75%→100% control stress), with each stage held for 5 minutes. After tensioning, it is fixed with a first-level locking nut to form the initial prestressed state, ensuring that the mid-span deflection of the main steel beam during the construction stage is ≤ L / 5000 (L is the span).

[0032] Step S4: Concrete Composite Layer Pouring and Curing. Concrete composite layer 2 is poured using a pump, proceeding from the mid-span towards both ends. The pouring speed is controlled at 0.5-1 m / h. An immersion vibrator is used for compaction, avoiding contact with the prestressed ducts. After pouring, cover with geotextile and water for curing. The curing time is ≥14 days. Strength is monitored using test blocks cured under the same conditions. Subsequent procedures can only proceed when the strength reaches 85% or more of the design strength.

[0033] Step S5: The second prestressed unit 3b is tensioned using a through-hole jack. The tensioning sequence is symmetrical synchronous tensioning, divided into 3 levels (50%→80%→100% control stress), with each level held for 3 minutes. After tensioning, it is locked with a secondary anti-loosening washer. After tensioning, the mid-span deflection is checked to be ≤L / 2500, and the stress in the support area is ≤90% of the design value.

[0034] Step S6: After the prestressed collaborative control structure is put into operation during the service phase, the structural condition monitoring unit 32 collects deflection and strain data in real time. The data sampling frequency is 1 time / h. When the mid-span deflection exceeds L / 2000 or the strain change rate exceeds 5%, the prestress adjustment program is started: the adjustable anchor component 31 is released by the hydraulic release device, and the corresponding prestress unit is tensioned or released by the jack. The adjustment amount is calculated and determined according to the monitoring data. After the adjustment is completed, it is locked again to ensure that the structure is always in a safe stress state.

[0035] In this embodiment, the composite steel beam has a span of 60m and is used in urban viaduct bridge projects. Actual testing showed that the maximum deflection at mid-span during the construction phase was 28mm (L / 2143), and the maximum deflection at mid-span during the completed bridge phase was 18mm (L / 3333). The maximum stress in the support area was 165MPa (less than the design value of 180MPa). After one year of service, the mid-span deflection was corrected to 15mm through prestressing adjustment. The structural performance is stable and reliable, fully meeting the design and usage requirements.

[0036] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A prestressed large-span composite steel beam, characterized in that, include: Main steel beam extending along the span direction (1); A concrete composite layer (2) is set above the main steel beam (1), and the concrete composite layer (2) and the main steel beam (1) form a combined load-bearing structure through shear-resistant connection members; The prestress control system includes at least a first prestress unit and a second prestress unit, which are arranged along different stress areas of the main steel beam (1). The first prestressed unit is set at the lower edge and / or web area of ​​the main steel beam (1) and is arranged in a non-linear or segmented manner along the length of the main steel beam (1); The second prestressed unit is disposed within the concrete composite layer (2) and / or the steel-concrete composite area; The prestress control system includes at least one adjustable anchoring component (31), which allows the corresponding prestressed unit to be repeatedly tensioned, released or adjusted during the construction and / or operation phases, so that the prestressed large-span composite steel beam is in a preset stress state at different stages; the main steel beam (1) is divided into at least a mid-span functional area and a support functional area along the span direction.

2. The prestressed large-span composite steel beam according to claim 1, characterized in that, The adjustable anchoring assembly (31) includes a multi-level locking structure and a releasable connection structure. After the corresponding prestressed unit completes its initial tensioning, it undergoes at least one re-tensioning or prestress level adjustment during subsequent construction or operation phases.

3. The prestressed large-span composite steel beam according to claim 1, characterized in that, The first prestressed unit is arranged in a broken line, a curved line or a segmented variable height along the length of the main steel beam (1), and the prestressing path matches the bending moment distribution of the main steel beam (1) along the span direction.

4. The prestressed large-span composite steel beam according to claim 1, characterized in that, The mid-span functional area is the core area for stiffness and deflection control, and the arrangement density of its prestressed units and shear connection members is higher than that of the corresponding members in the support functional area. The support functional area is an internal force release optimization area, and the arrangement density of its shear connection components is lower than that of the mid-span functional area.

5. The prestressed large-span composite steel beam according to claim 1, characterized in that, The first prestressed unit is tensioned after the main steel beam (1) is erected; the second prestressed unit is tensioned after the concrete composite layer (2) reaches the set strength.

6. The prestressed large-span composite steel beam according to claim 5, characterized in that, The prestress control system also includes a structural state monitoring unit (32), which acquires information on the deflection, strain or internal force of the main steel beam (1) during the construction and / or operation phases, and adjusts the prestress of the adjustable anchoring assembly (31) based on the monitoring results.

7. The prestressed large-span composite steel beam according to claim 1, characterized in that, The prestressed units in different functional zones differ from each other in tensioning sequence, tension force magnitude, and prestress holding level.

8. The prestressed large-span composite steel beam according to claim 1, characterized in that, The main steel beam (1) is formed by splicing multiple steel beam segments. Each steel beam segment is pre-stressed with corresponding prestressing channels and anchoring interfaces during the factory prefabrication stage. The prestressing unit is activated as a whole or in segments after on-site assembly.

9. A construction method for a prestressed large-span composite steel beam, applicable to the prestressed large-span composite steel beam as described in any one of claims 1-8, characterized in that, Includes the following steps: S1. Assemble or erect the main steel beam, and divide the main steel beam into the mid-span functional area and the support functional area along the span direction; S2. According to the stress requirements of different functional areas, the first prestressed unit and the second prestressed unit are arranged differently in the main steel beam or between the main steel beam and the concrete composite layer, and adjustable anchors are installed at the ends of each prestressed unit. S3. Before pouring the concrete composite layer, the first prestressed unit is tensioned in the first stage to form the initial prestressed state of the construction stage. S4. Complete the pouring and curing of the concrete composite layer so that the main steel beam and the concrete composite layer form a combined load-bearing structure. S5. After the concrete composite layer reaches the design strength, the second prestressed unit is tensioned in the second stage to optimize the force distribution in the mid-span and support areas of the completed bridge. S6. During the service phase of the structure, structural deformation or stress parameters are obtained by a structural condition monitoring device installed on the main steel beam and / or concrete composite layer. Based on the monitoring results, at least one set of prestressed units are adjusted using the adjustable anchors to achieve coordinated control of prestressing during the construction phase, the completed bridge phase, and the service phase.

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