A chloric erosion prefabricated segmental bridge pier joint opening zoning pre-tightening reinforcement system

Abstract

The present application relates to the technical field of bridge maintenance and reinforcement, and discloses a chloric corrosion prefabricated segmental pier joint opening partition pre-tightening reinforcement system, which comprises a cross-joint displacement meter arranged in a ring shape, a chlorine ion and steel bar potential sensor, and unbonded steel strands, anchorage devices, pressure bearing components and controllable tensioning devices independently arranged in each zone. A controller determines an initial compensation amount according to the opening, the chloric corrosion state and the eccentric rotation angle, and checks the total edge compressive stress in combination with the existing load effect; when the limit is exceeded, the load in the zone is limited or reduced, and the adjacent zone compensation is coordinated according to the product weight of the interval force transmission stiffness and the available load margin. The anchoring end force measuring assembly monitors the holding force during mechanical locking, and when readjusting, the load is first received, then the locking is released, the controlled tensioning or load reduction is performed, and the locking is relocked; when the data or anchoring is abnormal, the automatic load increase is stopped and the safe holding state is entered.

Description

Technical Field

[0001] This invention relates to the field of bridge maintenance and reinforcement technology, and in particular to a reinforcement system for repairing, pre-tightening, and maintaining the safety of precast segmental pier joints in the presence of chloride ion corrosion on existing bridges. Background Technology

[0002] Precast segmental bridge piers are assembled from multiple concrete segments, with the joint surfaces, prestressed tendons, and connecting components jointly bearing the axial force, bending moment, and shear force transmission. Chloride ions in sea-crossing, river-crossing, and de-icing salt environments can migrate through the protective layer, joint edges, and local defects. The expansion of steel corrosion products can cause cracking, spalling, and local stiffness degradation of the protective layer. When these damages are combined with construction deviations, vertical eccentricity, temperature and humidity changes, and vehicle loads, the joints may develop a non-uniform state along the circumference, with one side open and the other side under concentrated pressure, thereby weakening the shear force transmission of the joints and the overall bending stiffness of the pier.

[0003] Methods such as external steel sheathing, steel hoops, fiber confinement, increased cross-section, and overall prestressing are mainly used for overall column confinement or uniform reinforcement, but they are difficult to independently adjust for differences in the opening at different circumferential positions of the same joint. Directly increasing the preload of the entire circumference under eccentric rotation may also exacerbate stress concentration at the existing high-pressure edge. Durability protection can slow down subsequent erosion, but it cannot restore the normal compressive state of an opened joint on its own. Existing testing methods typically assess chloride ions, steel corrosion, cracks, and pier displacement separately, lacking a technical path to convert circumferential differences within the same joint into executable zonal tensioning amounts. After local compressive stress exceeds the limit, overall unloading or repeated manual adjustments are insufficient to simultaneously ensure opening restoration and compressive safety. Therefore, a pier joint reinforcement system is needed, which uses cross-joint prestressing components as the main body, is capable of zonal tensioning, and is constrained by pressure check. Summary of the Invention

[0004] The purpose of this invention is to provide a zonal pre-tensioning reinforcement system for precast segmental bridge pier joints subjected to chloride ion intrusion. This system features independently tensionable and mechanically locked pre-tensioning components along the circumference of the joint, enabling zonal repair of steel reinforcement corrosion, protective layer cracking, and localized joint opening after chloride ion intrusion. The joint opening, chloride ion intrusion status, and eccentric rotation angle are used to determine the initial compensation requirements. The actual tension force in each zone is simultaneously constrained by the joint edge compressive stress, anchorage bearing capacity, and local bearing capacity to avoid the formation of new high-pressure concentrations under eccentric conditions.

[0005] The system includes zoned prestressing components, circumferential monitoring components, compressive stress verification components, and closed-loop control components. Each circumferential measuring point has two measuring ends fixed to adjacent precast segments, positioned 50mm–200mm from the joint edge. Corresponding chloride ion sensors are installed within a protective layer 10mm–40mm from the outer surface of the concrete, and rebar potential sensors are electrically connected to adjacent longitudinal reinforcing bars. The reference opening is determined using verifiable joint openings from existing pier historical acceptance records, or the average of at least three valid samples under stable load boundaries. The difference between the current opening and the reference opening forms the opening increment. The calibrated and normalized chloride ion concentration, rebar potential, and their changes form the chloride corrosion index. The relative displacement and geometric position of the joints at different circumferential measuring points are used to fit the eccentric rotation angle.

[0006] The chloride corrosion index is dimensionless based on a uniform reference concentration, reference potential, and fixed comparison time interval. The concentration term is obtained by dividing the chloride ion concentration by the reference concentration; the potential term is obtained by subtracting the current potential from the reference potential and dividing by the potential scale (negative values ​​are taken as zero); the change term is obtained by subtracting the current potential from the potential at the previous comparison time and dividing by the same potential scale (negative values ​​are taken as zero). In this example, the three terms are weighted at 0.5, 0.3, and 0.2 respectively; the reference values ​​and weights are fixed during a round of rapid tensioning and are only re-evaluated during slow durability condition updates. This index is an input for adjusting priority and initial force correction and is not equivalent to the corrosion loss rate or component bearing capacity.

[0007] The reference potential must be specified and standardized to the same reference electrode. As an example of input for exponential calculation, the reference concentration is 10 mmol / L and the potential scale is 100 mV; the concentration, potential, and change terms are taken as 1.60, 1.50, and 1.30 respectively, resulting in a weighted average of... This corresponds to the M01 index in Table 3. This is the input construction for the dimensionless rule, and does not specify a universally applicable chloride corrosion threshold for engineering applications.

[0008] The eccentric rotation angle is determined by weighted least squares fitting of the opening increment of the same joint and the plane coordinates of the measuring points. The average opening is represented by a constant term in the fitted plane, and the small rotation angle components are represented by the slopes of the two coordinate directions. The result is obtained by projecting the two components of the radial unit vector at each measuring point. After eliminating invalid channels, sufficient non-collinear measurement points to determine the plane must still be retained; if the residual or the number of fitting conditions exceeds the limit, the load will not be automatically increased based on the fitting of that rotation angle.

[0009] To ensure that the opening degree, chlorination state, and rotation angle inputs correspond to the same execution unit, the measurement point parameters are first converted according to the geometric influence range of the candidate area, and then the measurement points are estimated. The initial target force proposed for this execution unit The formula for its calculation is:

[0010]

[0011] In the formula, For measuring points The initial target force is converted to the candidate region execution unit; The equivalent normal stiffness is calibrated based on the force value of the actuator and the closed displacement of the measuring point; This is the opening increment relative to the reference opening. The equivalent area of ​​the chloride-corroded steel bars within the influence range of the measuring point, converted to the execution unit; The chloride corrosion index is a dimensionless relative reference value and is not limited to the range of 0 to 1. To convert the equivalent area and chloride corrosion index into the equivalent expansion stress coefficient of force; This is the eccentricity angle influence coefficient; The signed projection of the small rotation angle fitted by the circumferential opening increment onto the radial direction of the measuring point is expressed in radians. The initial target force correction uses its absolute value to represent the rotation angle amplitude, and the opening side is identified by the measured opening distribution. The parameter calibration and actual calculation use the same force, length, and angle units. It should be within the verified applicable range that is greater than zero. If it exceeds the range, the automatic update of the correction item should be stopped and the error checked. If the calculated target force is less than zero, it should be taken as zero. If it exceeds the bearing or anchorage limit, the amplitude should be limited first. The initial target force is not directly used as the actual execution command.

[0012] The process for obtaining stiffness and correction coefficients is as follows: After confirming the anchorage, force value, and load boundaries, apply no fewer than three safe small increments to the candidate zone execution unit, and record the force, tension end displacement, and closed displacement of each measuring point at the same time; use the relationship between the controlled incremental force and the effective closed displacement to obtain... Then, the area of ​​the reinforcing bars within the influence range of the same execution unit is converted to... In traceable comparison records of different chloride corrosion states and corner states, the measured target force was used as the response quantity for... A constrained fit was performed with the interaction term of the rotation magnitude to obtain... , Some operating conditions should be left for independent inspection, and the applicable load and contact state should be recorded. When there is no valid calibration basis, only manually verified conservative loading is permitted; automatic amplification of compensation by arbitrary coefficients should not be used.

[0013] Each pretensioning zone is equipped with at least one independently tensioned unbonded steel strand, anchorage, bearing pad or local stiffening member, controllable tensioner, and anchorage end force measuring component. The steel strand should preferentially pass through existing or pre-reserved ducts; if ducts are not available, external guiding members verified by structural calculations should be used. Any new perforations must be detected by reinforcement and avoid main reinforcement, stirrup reinforcement zones, shear keys, grouting channels, and severely deteriorated zones. After simultaneous low-load placement in each zone, the load is increased in stages, with the opening, force value, and anchorage status checked at each stage. To avoid only checking the new pretensioning effect and neglecting existing loads, the pretensioning zone... The total compressive stress at the corresponding compression edge is checked using the following formula:

[0014]

[0015] In the formula, This represents the total compressive stress at the compressed edge. For the same load combination and the same check edge, the compressive stress is formed by the combination of existing dead load, live load, existing prestress, and other existing effects. This is the equivalent normal resultant force that the newly added preload in each area is distributed to the effective pressure area through the joint force transmission relationship; The effective pressure-bearing area; To determine the eccentricity of the newly added equivalent resultant force relative to the centroid of the region, the direction of pressure increase corresponding to the pressure-bearing edge is taken; This is the section modulus of the compressed edge. Existing and newly added effects in this formula must not be repeatedly considered. The allowable value and the total compressive stress use the same working condition caliber. For bidirectional bending, the increased pressure contribution in both directions should be considered separately, and the control edge should be taken. If a new stress increment is used for verification, its allowable margin is the total allowable value minus the existing compressive stress at that point. The above parameters should be recalculated when the contact area, compressed edge, or load combination changes. When there is significant separation, crushing, or contact nonlinearity exceeding the applicable range of linear elastic superposition, a verified overall contact analysis should be used instead of directly using the original section parameters. (Over-limit zone) There is still an uncompensated amount after limiting the amplitude or reducing the load. At that time, candidate neighboring regions The amount transferred in is given by the following formula:

[0016]

[0017] In the formula, Candidate neighboring regions The amount transferred in; Over-limit zone The unfulfilled gap between the initial target force and the executable force confirmed by pressure limiting; Adjacent areas For the over-limit area Positive equivalent normal force transmission stiffness; The available load margin is the result of subtracting the current preload from the rated allowable tension force in the adjacent zone; if it is less than zero, it is taken as zero. The number of adjacent regions participating in the allocation; summation index. This indicates the region participating in the allocation. The force transmission stiffness is defined as the increment of the equivalent closed reaction force in the over-limit region caused by the unit equivalent axial adjustment displacement of adjacent regions. This reaction force increment is determined by multiplying the local normal stiffness of the over-limit region by the measured closed displacement; its unit is force divided by length, and it does not directly use the reciprocal sensitivity of "incremental tension force divided by over-limit region closed displacement" as a weight. The coefficients are obtained from small load disturbances or structural models verified in the field. Coupling values ​​that cannot promote the closure of the over-limit region do not participate in the allocation.

[0018] Load coordination follows a sequence of "candidate allocation—full-area prediction—constrained execution—resampling." Commands must simultaneously satisfy the constraints of total joint compressive stress, steel strands, anchorages, bearing components, and single adjustment step size; they cannot only check the receiving area while omitting pressure increases in other areas caused by force coupling. Automatic transfer will not be executed if the denominator is zero, there is no positively bearing area, or the data is invalid. Stability maintenance conditions are determined jointly based on the opening degree of each effective measuring point, total compressive stress in the entire area, and anchorage status, not by the algebraic sum of the allocated quantities as the criterion for reinforcement completion.

[0019] Compared to a uniform pre-tightening method that treats the entire joint as a single load-bearing unit, this invention forms independently implementable pier joint repair units through cross-joint steel strands, anchorages, and pressure-bearing components. This allows for compensation on sides with larger openings, more significant chloride corrosion effects, or eccentric openings, while simultaneously limiting further load accretion at high-pressure edges. Uncompensated compensation is only distributed in a coordinated manner among adjacent zones that have been calibrated under small loads and confirmed to have force transmission coupling and sufficient self-bearing capacity. The control results are simultaneously constrained by the joint opening target, effective compression section, anchorage structure, and load margin of the tensioning components. Attached Figure Description

[0020] Figure 1 This is a technical roadmap for the present invention, from seam status acquisition, initial compensation calculation, pre-tensioning zone formation, zone tensioning, compressive stress verification to feedback adjustment.

[0021] Figure 2 A schematic diagram showing the layout of the pre-tensioning components, anchoring bearing components, tensioning units, and monitoring components installed along the joints of precast bridge segment piers on existing bridges.

[0022] Figure 3 This is a schematic diagram illustrating the installation, monitoring, control, and long-term maintenance process of this invention.

[0023] Figure 4 This is a schematic diagram of the elevation layout of the bridge pier height sections H1-H4 and the cross-joint reinforcement components.

[0024] Figure 5The diagram shows the contact pressure distribution and circumferential boundary pressure comparison for five given states in an independent parameterized morphological example.

[0025] Figure 6 This is a diagram showing the change of total edge compressive stress with the execution record point and the amount of compensation transfer between adjacent zones after pressure limiting in the circumferential four-zone control example.

[0026] Figure 2 In the diagram, 1 is a precast concrete segment, 2 is an unbonded steel strand, 3 is an anchor, 4 is a bearing plate or local stiffening component, 5 is a cross-joint displacement gauge, 6 is a chloride ion and steel bar potential sensor, 7 is a controllable tensioner, and 8 is an anchorage end force measuring component. Figure 2 The circumferential zoning is for layout purposes only; the specific boundaries are determined according to the status of each joint measuring point. Figure 4 H1-H4 in the text only represent the height section, and are used separately from the circumferential pre-tightening sections Z1-Z4. Detailed Implementation

[0027] This embodiment addresses the joint repair of precast segmental piers in existing bridges exposed to chlorine corrosion environments, such as seaports, cross-sea passages, and coastal viaducts. When adjacent concrete segments form circumferential joints, uneven opening caused by chlorine corrosion, eccentric loading, and temperature deformation can easily lead to localized overpressure or insufficient compensation if the entire circumference is uniformly pre-tightened. Figure 1 The following procedures are provided: state acquisition, compensation calculation, zone tensioning, compressive stress verification, and feedback adjustment. Figure 2 The arrangement relationships of the cross-joint steel strands, anchorages, pressure-bearing components, tensioners, and sensors are given; Figure 3 The installation and monitoring control process is shown. Figure 4 The elevation sections of the bridge piers are shown. Figure 5 The contact pressure distribution and circumferential comparison of the independent parameterized morphological examples are shown. Figure 6 The total compressive stress and pressure transfer results for the circumferential four-zone control example are given. Existing piers should prioritize the use of existing or maintenance ducts; if duct conditions are not available, external guide members verified by structural calculations should be used. If it is necessary to add new perforations, the reinforcement and duct should be detected first, avoiding the main reinforcement, stirrup reinforcement zone, shear key, grouting channel and severely deteriorated zone.

[0028] Before implementation, the segment number, cross-sectional dimensions, original prestressed structure, duct location, concrete strength, and defect data of the target joint were verified, and a circumferential coordinate system was established based on the construction drawing baseline. At least eight measuring points were set along the circumference of each joint, spaced 0.2m to 1.0m apart, with increased spacing in areas of significant opening, on the seaward side, and near cracks. The two measuring ends of the cross-joint displacement gauge at each measuring point were fixed to the stable concrete areas on both sides of the joint, with a range of 5mm to 50mm and a resolution not exceeding 0.01mm. Redundant displacement gauges were installed at critical locations. Chloride ion sensors and rebar potential sensors were correspondingly installed within the protective layer, and temperature and humidity data were used to correct sensor drift. The target opening, allowable compressive stress value, compressive stress difference between adjacent zones, limits for steel strands and anchors, loading step length, and sampling cycle were all determined based on the original design, on-site testing, small load calibration, and load-bearing verification, without using forced complete closure as the control target.

[0029] In one specific configuration, the active end employs a re-tensionable, controllable unloading anchor and matching locking components; the tensioner maintains a re-connectable interface and effective tail length with the steel strand, and is equipped with temporary clamps to bear the load, locking status detection components, and auxiliary mechanical stops. The anchorage end force measuring component is located on the effective force transmission path of the anchorage reaction force, using a fully calibrated force measuring washer or equivalent force measuring structure, which can still read the holding force after the tensioner is no longer under working force; the tensioner force sensor is only used for verifying the loading force during the adjustment phase. The force value after mechanical locking cannot be replaced by the hydraulic pressure of the unloaded tensioner.

[0030] When load reduction or reloading is required, first engage the tensioner to accept the existing steel strand force, and verify the consistency of tension force, anchor end force, and displacement. Only after confirming that the load transfer is complete should the unlocking mechanism matched with the anchor be activated, and its positioning status checked. Subsequently, load increase or decrease should be controlled according to the limited step size, re-tightening or restoring the mechanical lock, and then the working load of the tensioner should be slowly removed. After the force, displacement, and locking position are verified to be qualified, the monitoring state should be entered. Ordinary anchors that cannot be reloaded should not be used to replace the above configuration, nor should the anchor be forcibly removed before the steel strand force has been accepted. The pressure loss self-locking valve and auxiliary mechanical stop cover the load transfer stage; if any interlock signal is invalid, the operation will stop.

[0031] To illustrate the correspondence between parameter input, region formation, total compressive stress verification, and pressure limit transfer, this section uses a constructed control example. Table 3 provides the given opening, opening increment, chloride corrosion index, and target force comparison values ​​for 12 circumferential measuring points; Table 6 lists the equivalent calculation parameters compatible with these target forces; Table 7 supplements the compressive stress calculation parameters; and Table 8 provides all execution record points. The equivalent area and compression section parameters are determined using the algebraic construction method disclosed below and are used to verify the calculation relationships, not as field calibration or engineering verification results; the holding opening in Table 4 is the given feedback input for the holding judgment test and is not derived from a separate compressive stress formula. The material test excerpt in Table 2 is independent of the above control example. Figure 5 Use another set of independent parsed morphological inputs, as fully given in Table 9.

[0032] Before sensor connection, zero point, range, and time synchronization verification are completed. After data arrives at the controller, it is associated with a unified timestamp. When the displacement gauge continuously deviates beyond the consistency threshold, the measuring point is marked as pending verification and is not allowed to trigger load increase independently. When chloride ion or rebar potential channels fail, the corresponding chloride corrosion correction item is no longer updated, and the relevant pre-tightening zone is limited to the confirmed safe load before manual verification. The source, applicable joint, and effective time of the reference opening, chloride corrosion index conversion factor, local normal stiffness, and interval force transmission stiffness are all recorded to prevent the direct use of parameters from other joints or non-pier parameters for current control.

[0033] Table 1 Key parameters for illustrative numerical examples

[0034] parameter Value unit use Number of circumferential measurement points 12 indivual One measuring point every 30° Execution record point 6 indivual See Table 8, including newly added zeros. Protective layer calculation depth 30 mm Chlorine corrosion state estimation Input method Fixed given value — Interface inputs in Tables 3 and 4 Low load placement ratio 5～15 ％ Rated allowable tension ratio Seam opening target 0～0.25 mm Example control band Total compressive stress allowable value 10.0 MPa Including the existing contribution of 2.2 MPa Limit of total compressive stress difference between adjacent zones 5.6 MPa Example Preservation Decision

[0035] Scope of application of the material record. Table 2 lists the nominal area, maximum force, and tensile strength of 14mm, 20mm, and 32mm ordinary reinforcing bars, for batch comparison of the corresponding reinforcing bars. Parameters for steel strands, anchorages, bearing plates, and tensioners are determined according to their respective product data, inspection records, and stress calculations; the tensile strength of ordinary reinforcing bars is not converted into the allowable tension force of steel strands. This material record is not used to demonstrate the control effectiveness of this system.

[0036] Table 2 Excerpt from Tensile Test Records of Ordinary Steel Reinforcing Bars

[0037] Specifications (mm) Nominal area (mm²) Maximum force kN Tensile strength (MPa) Average maximum force kN Average tensile strength (MPa) Record date environment Work Order 14 153.9 94.60、95.25 614.71、618.92 94.93 616.82 2026-01-05 23℃ 2026MJL-JCX0008 20 314.2 194.26、196.51 618.27、625.43 195.39 621.85 2026-01-05 23℃ 2026MJL-JCX0010 32 804.2 502.56、497.94 624.92、619.17 500.25 622.05 2026-01-05 23℃ 2026MJL-JCX0013

[0038] When using Table 2, verify the material source, specifications, inspection batch, and stress conditions of the actual components; only parameters that match the original material records and the intended use of the components are included in the corresponding calculations. The record date, environment, and work order number are only used to trace the material record and are archived together with the original report, component drawings, and calculation documents.

[0039] State identification and zoning. The controller calculates the opening increment under stable load boundaries and processes chloride ion and rebar potential information using a unified reference electrode, time interval, and normalized benchmark; it also fits the eccentric rotation angle based on the geometric coordinates of each measuring point. Figure 3 The process is presented, including data acquisition, preprocessing, state analysis, initial target force calculation, threshold verification, pressure limiting measures, and long-term monitoring. The target force in Table 3 is used to verify the multi-point estimation and partitioning rules of the same execution unit; its calculation input is shown in Table 6.

[0040] Table 3 Comparison of given state and initial target force at circumferential measuring points

[0041] measuring point Angle (°) Opening (mm) Increment (mm) Chlorine corrosion index Initial target force (kN) Pre-tensioning area M01 0 0.125 0.008 1.510 28.900 Z1 M02 30 0.297 0.180 1.735 30.500 Z1 M03 60 0.449 0.335 1.712 32.472 Z1 M04 90 0.489 0.380 1.498 51.900 Z2 M05 120 0.481 0.378 1.255 54.300 Z2 M06 150 0.506 0.409 1.215 56.877 Z2 M07 180 0.452 0.358 1.249 33.800 Z3 M08 210 0.381 0.288 1.322 35.500 Z3 M09 240 0.252 0.156 1.361 37.608 Z3 M10 270 0.071 -0.030 1.262 9.900 Z4 M11 300 0.025 -0.082 1.206 10.500 Z4 M12 330 0.025 -0.088 1.346 11.274 Z4

[0042] This example selects 15% as the threshold for the difference in adjacent target forces: when the absolute difference in target forces between adjacent measuring points is no greater than 15% of the larger of the two and is continuous along the circumferential direction of the joint, they are merged into the same pre-tightening zone. During comparison, the last and first measuring points are checked simultaneously to form a circumferential closed boundary; when both are zero, it can be classified as a zone without additional load requirements. The zone boundary should also meet the layout conditions of the duct, external guide component, and anchorage. In Table 3, the three measuring points in each group have been converted to the target force estimate of the same execution unit in that group, and therefore the arithmetic mean is taken under the conditions of equal spacing and equal confidence; these values ​​are not the three local reaction forces that should be added together. When the spacing is not equal or the confidence is different, the normalized influence length and measurement confidence weight are used. If any effective measuring point in the zone still does not meet the opening target, the completion should not be judged solely based on the average value.

[0043] Each pretensioning zone is equipped with an independent steel strand and anchoring pressure-bearing components at both ends. Each tensioner is independently numbered and adjusted by the controller. Figure 4 The zero height reference is the position of the pier top surface, which corresponds to the bottom surface of the cap beam, and the vertical upward direction is positive. The illustrated standard height unit shows the total indicated pier height as follows: H4 is 0 to H3 is to H2 is to H1 is To the top surface of the foundation The height segmentation does not represent four additional circumferential pre-tensioning zones, nor does it change the zoning control of a single joint. In the diagram, vertical lines represent the steel strand layout channels, horizontal double lines represent the elevations of the joints and anchorage bearing components, and small rectangles adjacent to the joints represent the anchorage bearing components; the actual joint length, segment height, and anchorage position are determined according to the bridge pier drawings and calculations.

[0044] After the pre-tension zone is formed, the controller sequentially checks the rated allowable tension of the steel strands, the anchorage bearing margin, the local pressure on the bearing pad, the condition of the ducts or external guide components, and the current joint compressive stress. If any condition is not met, the zone is not included in the automatic load increase targets, but remains at the verified safe load. Adjacent zones can only receive compensation if their own opening, edge compressive stress, steel strands, anchorages, and local bearing margin all meet the requirements. This constraint ensures that the zone identification results correspond to the actual executable pier reinforcement path, and the calculated output cannot replace the verification of anchorage, local bearing pressure, and joint force transmission.

[0045] Graded tensioning and holding verification. Each zone is simultaneously positioned at 5%–15% of the confirmed rated allowable tension force, eliminating permissible component gaps and checking the response direction, followed by controlled step adjustments. Before each command, the total edge compressive stress of the entire zone is predicted. After the command is executed, the actual tension force, locking end holding force, cross-joint displacement, and rotation angle are read and verified. The working load of the tensioner is only removed after mechanical locking is confirmed. The given holding opening in Table 4 is all within the control zone of 0mm–0.25mm. The total compressive stress calculated according to Table 7 does not exceed the total allowable value of 10.0MPa in this example, and the maximum difference in total compressive stress between adjacent zones does not exceed 5.6MPa. Z3 is constrained by the upper limit of the total compressive stress, while other zones still have margin.

[0046] Table 4. Calculation results of the given opening degree and total compressive stress for maintaining the judgment.

[0047] Pre-tensioning area Actual preload (kN) Maintain opening (mm) Total edge compressive stress (MPa) Maximum total compressive stress difference between adjacent zones (MPa) Is the voltage limited? Z1 30.624 0.061 5.306 3.042 no Z2 54.659 0.089 8.348 3.042 no Z3 35.000 0.142 10.000 5.266 yes Z4 10.894 0.025 4.734 5.266 no

[0048] In Table 4, the actual preload of Z2 increased by 0.300 kN relative to the initial target value, and Z4 increased by 0.336 kN, both from the compensation transfer after the pressure limit of Z3. The actual preload of Z3 was lower than the initial target value, and the total edge compressive stress was already limited, so the load of Z3 was not increased separately. Monitoring continued after entering the holding state. The controller compared the newly sampled opening, the difference in compressive stress between adjacent zones, and the anchorage status, and returned to graded adjustment when the changes reached the set trigger conditions. During the loading stage, the tension sensor and the anchorage end force measuring component were cross-calibrated. During the locking and holding stage, the effective reading of the anchorage end force measuring component was used as the standard, and the opening was based on the relative displacement of the two measuring ends of the cross-joint displacement gauge. When redundant displacement time was set, only the effective value that passed the consistency judgment was used.

[0049] Pressure Limit Transfer and Operation Judgment. In this example, the allowable total compressive stress is 10.0 MPa, the existing load contribution is 2.2 MPa, and the corresponding available margin for the new compressive stress is 7.8 MPa. When the predicted initial target force of Z3 will cause its total compressive stress to exceed the limit, the unexecuted command is directly limited to 35.000 kN; only when the applied load causes the exceedance is the load acceptance, unlocking, and controlled load reduction procedure processed. The initial target force of Z3 is 35.636 kN, and the uncompensated amount after limiting is 0.636 kN; compensation commands are issued to Z2 and Z4, which have positive force transmission coupling on the same joint and can accept the load, and all areas including Z3 are reviewed before execution. Figure 6 The recording points and calculation process are shown in Table 8; when there is no receptive area, maintain the verified safe status and prompt for manual verification.

[0050] Table 5. Weighted compensation of equivalent force transmission stiffness after Z3 pressure limiting.

[0051] Load level Transfer out area Transfer area Transfer volume (kN) Preload / margin before transfer (kN) Total compressive stress after transfer (MPa) Steel strand / anchor limit (kN) determination Level 4 Z3 Z2 0.300 54.359 / 5.641 8.348 60 / 65 pass Level 4 Z3 Z4 0.336 10.558 / 19.442 4.734 30 / 35 pass

[0052] The weights in Table 5 are calculated as follows: , These two values ​​are coupling parameters set for recalculating the given transfer amount in this example, not field calibration records. The available load margins for Z2 and Z4 are 5.641 kN and 19.442 kN, respectively, with corresponding product weights of 0.4716981132 and 0.5283018868. Distributing 0.636 kN according to the above proportions yields 0.300 kN and 0.336 kN, respectively. Before allocation, candidate regions without positive coupling, without load margin, or with invalid data are excluded. When a region is limited by step size, compressive stress, or bearing margin, its transfer amount is first truncated, and then the remaining candidate regions are redistributed with the unexecuted margin until the margin is zero or there are no more feasible regions. The weights only propose controlled increments and do not mean that the same force value in adjacent regions can completely replace the closure effect of the over-limit region. After execution, the effective opening and the total compressive stress of the entire region are still used for verification.

[0053] Calculation conditions and verification for the example. This example lists the given monitoring state, constructed equivalent parameters, and calculation outputs. The state and target force in Table 3 are given control values. The parameters in Tables 6 and 7 are constructed based on the following algebraic relationships; material test excerpts are not involved in the calculation of these equivalent parameters. The above given conditions are used to illustrate the algorithm interface and calculation relationships.

[0054] Table 6 adopts , and The radius of the measuring points on the example section is 750 mm. Zero degrees are located above the section, and the angles increase counter-clockwise, with one point set every 30 degrees according to Table 3. The average term is obtained by fitting the opening increments in Table 3. The slopes of the two planes are respectively and The rotation angles in Table 6 are obtained by radial projection. These rotation angles only describe the fitted plane portion; the remaining non-planar differences in the original given opening are still retained as measurement point residuals.

[0055] Using the target forces given in Table 3 as a reference for recalculation, this example will use the values ​​given in each row... Divide by ,deduct Then divide by Construct Table 6 This inverse relationship limits the construction method of the example parameters and does not belong to the identification of physical parameters. Substituting the values ​​in Table 6 back into the initial target force calculation formula in the forward direction can verify the accuracy of Table 3 up to 0.001kN; the actual device should replace these constructed values ​​with the independent calibration parameters of the corresponding joints.

[0056] Table 6 Construction parameters for initial target force recalculation

[0057] measuring point (Mrad) (mm²) (kN) M01 -0.225432304 945.280189005 28.900 M02 -0.066575632 671.177250566 30.500 M03 0.110119927 556.487464002 32.472 M04 0.257308941 1222.740791864 51.900 M05 0.335552231 1557.332675748 54.300 M06 0.323884573 1663.581934415 56.877 M07 0.225432304 778.300433743 33.800 M08 0.066575632 906.512358460 35.500 M09 -0.110119927 1151.627643052 37.608 M10 -0.257308941 439.274151063 9.900 M11 -0.335552231 570.580970755 10.500 M12 -0.323884573 548.877122780 11.274

[0058] The substitution process for M01 is as follows:

[0059]

[0060] Based on a 15% adjacent difference threshold, Table 3 defines four continuous zones Z1 to Z4, with initial target force averages of 30.624 kN, 54.359 kN, 35.636 kN, and 10.558 kN, respectively. After the zoning is completed, the opening degree is still checked point by point; the average value cannot be used as a substitute for point-by-point compliance.

[0061] The total compressive stress structural example takes the existing action contribution at each check edge as 0. The total allowable value is 10.000 MPa. The equivalent distribution of the additional force is 96% of the actual preload in this zone plus 2% of the actual preload in each of the two adjacent zones, i.e., distributed in a circumferential closed sequence; the sum of the distribution coefficients for each column is 1, therefore no additional total preload is added. The eccentricity of each zone is taken as... , (Area and section modulus are expressed in mm² and mm³, respectively). Based on the effective compressive area of ​​the structurally compatible structures corresponding to the new compressive stresses of 3.106, 6.148, 7.800, and 2.534 MPa corresponding to the final values ​​in Table 4, the obtained parameters are listed in Table 7. This is a partial algebraic calculation example of the strip, and the geometry of this equivalent strip is not taken as the actual pier section.

[0062] Table 7 Construction parameters for total compressive stress recalculation

[0063] Pre-tensioning area (MPa) (mm²) (mm³) (mm) (kN) Z1 2.200 19774.694140 1977469.414037 100 30.710100 Z2 2.200 17496.785947 1749678.594665 100 53.785120 Z3 2.200 8951.553846 895155.384615 100 34.911060 Z4 2.200 9290.228887 929022.888713 100 11.770720

[0064] For example, the new equivalent normal resultant force of Z3 after the transfer is:

[0065]

[0066] Convert the force to Newtons and substitute it into the parameters in Table 7 to obtain... Similarly, the total compressive stresses for Z1, Z2, and Z4 are 5.306, 8.348, and 4.734 MPa, respectively; the maximum differences between adjacent zones remain 3.042, 3.042, 5.266, and 5.266 MPa, respectively. The newly added stress margin of 7.8 MPa corresponds to different calculation methods than the total allowable value of 10.0 MPa. The chart in this example uses the total compressive stress including the existing 2.2 MPa load.

[0067] Figure 6 All execution record points in Table 8 are used: Point 0 is the newly added load zero point; Point 1 is the position of 10% of the rated allowable force in each zone; Points 2 and 3 are 40% and 70% of the initial target force, respectively; Point 4 is the candidate safety force after the fourth level of pressure limiting; and Point 5 is the force after the transfer of adjacent zones at the same level. The rated allowable tension forces of Z1 to Z4 are 40, 60, 50, and 30 kN, respectively; the anchorage limits for the two transfer zones are 65 and 35 kN, respectively. This sequence is used to verify the interface between force and total compressive stress calculations point by point and does not represent the field response at fixed time intervals; in actual execution, the decision to maintain or readjust should be made after each sampling based on the target opening and safety conditions.

[0068] Table 8 Figure 6 Complete execution log point

[0069] Recording point state Z1 (kN) Z2 (kN) Z3 (kN) Z4 (kN) 0 Add zero points 0.0000 0.0000 0.0000 0.0000 1 Low load placement 4.0000 6.0000 5.0000 3.0000 2 Level 2 12.2496 21.7436 14.2544 4.2232 3 Level 3 21.4368 38.0513 24.9452 7.3906 4 Level 4 voltage limit 30.6240 54.3590 35.0000 10.5580 5 After transfer at the same level 30.6240 54.6590 35.0000 10.8940

[0070] In Table 4, 0.061mm, 0.089mm, 0.142mm, and 0.025mm are used as the given effective opening of the four-zone holding judgment interface, respectively. Table 8 only discloses the discrete calculation of force and stress values, and does not generate undisclosed continuous displacement curves based on this. The holding state must simultaneously meet the opening, total compressive stress, difference between adjacent zones, sensor consistency, and mechanical locking conditions. The calculation example is checked using three consecutive effective sampling cycles for confirmation. The sampling interval is determined separately by the execution speed and load stability.

[0071] Figure 5 The morphological examples are independent of Tables 3 to 8. Let... For normalized radial coordinates, the range is 0 to 1. #imgpt79# is the circumferential angle measured counterclockwise from above the cross-section; the pressure in state #imgpt80# uses the given analytical field #imgpt81#. #imgpt82#, #imgpt83#, and #imgpt84# are all in MPa, #imgpt85# is the peak direction angle, and the angle unit is unified when calculating trigonometric functions; negative values ​​are truncated to zero to represent the zero-contact zone, and the lower right curve takes the boundary value of #imgpt86#. Table 9 lists all parameters. The five field maps share a common grayscale scale of 0 to 11 MPa, and each map is not individually normalized.

[0072] Table 9 Figure 5 Given conditions for independent parameterized morphological cases

[0073] state #imgpt87# (MPa) #imgpt88# (MPa) #imgpt89#(°) meaning Baseline state 3.0 1.5 0 Reference Field Eccentric opening 2.0 7.0 30 Open side zero contact Chlorine Corrosion Correction 2.3 8.2 30 Candidate field to be checked Zone tensioning 3.1 7.4 30 Candidate field to be checked Pressure limiting transfer 4.0 6.0 30 Schematic field satisfying the 10.0MPa limit

[0074] Figure 5 In the "chlorine corrosion correction" and "zonal tensioning" modes, candidate fields to be verified before execution are used, with boundary peak values ​​exceeding 10.0 MPa; the peak value of the morphological field given by "pressure-limited transfer" is 10.0 MPa. These five states illustrate the expression of non-uniform contact, candidate overpressure, and constrained distribution, and do not treat the truncation operation of the analytical field as a solution for the equilibrium contact of the actual bridge pier; engineering control still uses the validated contact model and effective monitoring feedback for this bridge pier.

[0075] The closed-loop control component completes data integrity judgment, outlier handling, opening and rotation angle updates, zone load calculation, and total edge compressive stress verification within each sampling cycle, and outputs load increase, hold, load decrease, or transfer commands. When the opening is between 0mm and 0.25mm, the total edge compressive stress does not exceed the allowable value of 10.0MPa in this example, the stress difference between adjacent zones does not exceed 5.6MPa, the steel strands and anchorages are not over-limit, and the sensors are consistent, it enters mechanical locking hold or low-frequency monitoring; when data is missing, anchorage slippage, opening exceeds the limit, rotation angle changes abruptly, or the total compressive stress approaches the upper limit, sampling is intensified; controlled adjustment is only executed after the data, load-bearing, and mechanical interlocking conditions are met again. Existing piers should determine the anchorable and penetration areas based on as-built drawings, rebar scanning, and test results; external guide components verified by structural calculations should be used at locations where penetration is not suitable, and monitoring should only be retained at locations where pre-tightening components cannot be installed, without forcibly allocating compensation exceeding the bearing capacity of adjacent zones.

[0076] After major pier repairs, significant temperature cycling, earthquakes, or sudden changes in joint condition, the local normal stiffness, zone load-bearing stiffness, effective compression area, and control parameters should be re-verified before resuming zoned adjustments. Operational records should be kept of confirmed measuring point status, tensioning commands, actual force values, mechanical locking status, pressure limit markers, and manual intervention information for bridge maintenance verification. Control terminals can be industrial computers, programmable logic controllers, or embedded devices; the data acquisition unit is connected to the pier maintenance box via a communication bus. The control box, wiring terminals, and tensioners should be waterproof, dustproof, corrosion-resistant, and lightning-protected. No new adjustment or unlocking commands should be executed during power or communication interruptions. When locked, the preload is maintained by the anchorage and mechanical locking structure; during load transitions, it is maintained by the pressure-loss self-locking valve and the auxiliary mechanical stop that has already borne the load. Relocking should be completed after manual verification. After restoration, the force value, displacement, and anchorage status should be verified before accepting new adjustment commands.

[0077] In actual implementation, the flatness, local compression, and anti-slip verification of the anchorage surface should be completed before tensioning, and necessary anti-corrosion and waterproofing structures should be installed around the pre-tensioned components. Changes to control parameters should retain version, basis, and approval records; parameters should not be shared between different joints, different cross-sections, or different damage states without verification. The calculation relationships shown in the illustrative numerical examples are still subject to the original pier design data, material and anchorage verification, duct detection, contact surface and waterproofing verification, and continuous measured data in engineering applications, and cannot be used to replace on-site reinforcement design.

[0078] Maintenance personnel conduct regular inspections to confirm the protective layer, joint seepage, anchorages, mechanical locking status, and sensor effectiveness. If further deterioration or damage to the protective structure is found, the causes affecting load-bearing capacity and monitoring reliability are addressed first, and then controlled adjustments are restored based on valid data. The controller calculates increments using a confirmed baseline and the current state, and does not treat short-term vehicle vibrations, wind-induced disturbances, or single communication anomalies as continuous opening changes. Tables 3-8 illustrate the interface relationships for zoning, force value calculation, total compressive stress verification across the entire zone, and hold-through determination. Table 9 explains... Figure 5 Independent input form; in actual engineering, parameters and real feedback data verified by corresponding bridge piers are used, and the applicable boundaries are continuously reviewed.

Claims

1. A pre-tensioned reinforcement system for the joint opening of precast segmental bridge piers subjected to chlorination corrosion, characterized in that, The system includes multiple pre-tensioning zones arranged circumferentially along the joint to be reinforced, partitioned pre-tensioning components spanning the joint, a circumferential monitoring component, a compressive stress verification component, and a closed-loop control component. Each partitioned pre-tensioning component includes at least one unbonded steel strand spanning adjacent precast segments along the pier axis, anchors at both ends of the steel strand, bearing pads or local stiffening components cooperating with the anchors, and a controllable tensioner. The steel strands in each zone can be tensioned independently and mechanically locked by the anchors. The circumferential monitoring component obtains the joint opening, corrosion status, and eccentricity angle. The closed-loop control component determines the initial compensation amount of the measuring points based on the target opening range and the calibrated joint force transmission parameters, merges circumferentially continuous measuring points with similar compensation amounts into pre-tensioning zones, and controls each zone to be simultaneously positioned under low load and then gradually increases the load. The compressive stress verification component calculates the total edge compressive stress based on the actual preload of each zone and the effective compression section parameters of the joint, combined with the existing load effect. Before candidate load increase or compensation transfer, the total edge compressive stress of each zone is verified. If the limit is predicted to exceed, the corresponding command is restricted. If the applied load causes the limit to exceed, the load of that zone is reduced. After verifying the bearing capacity of adjacent zones, the uncompleted compensation amount is allocated according to the product weight of the equivalent normal force transmission stiffness between the over-limit zone and the adjacent bearing zone and the available load margin of the adjacent zone. The target opening range, allowable compressive stress value, equivalent normal force transmission stiffness, and load limit value are determined by the original design data, on-site testing, small load calibration, and component bearing capacity verification. Before load increase or transfer, the actual force value, opening, compressive stress, anchorage status, and data validity are verified. If monitoring is missing, communication is abnormal, anchorage is abnormal, or there is no bearing zone, automatic load increase is stopped and the confirmed safe load is maintained.

2. The system according to claim 1, characterized in that, At least one cross-joint displacement meter is installed at each circumferential measuring point. The two measuring ends of the cross-joint displacement meter are fixed to the adjacent precast segments on both sides of the joint. The relative displacement of the two measuring ends along the pier axis is used as the joint opening. The circumferential measuring point spacing is 0.2m to 1.0m. The measuring point density is higher in the significantly opened area, the sea-facing side, or the area adjacent to the crack than in other locations. Important measuring points are equipped with independent redundant displacement meters.

3. The system according to claim 1, characterized in that, Chloride ion sensors and rebar potential sensors are arranged circumferentially along the joint and corresponding to the cross-joint displacement gauge. The chloride ion sensors are installed in the protective layer 10mm to 40mm from the outer surface of the concrete, and the rebar potential sensors are electrically connected to the longitudinal reinforcing bars adjacent to the joint. The chloride ion concentration, rebar potential, and joint opening adopt the same time reference and are associated with the same circumferential influence range. The sensor readings are used for state correction after zero-point, temperature drift, and validity checks, and are not directly used as the value for determining the bearing capacity of the component.

4. The system according to claim 1, characterized in that, The chloride corrosion index is determined by the calibrated and normalized chloride ion concentration, steel bar potential and its change; the eccentric rotation angle is obtained by fitting the relative displacement and geometric position of the cross joint of different circumferential measuring points in the same joint; the chloride corrosion index and eccentric rotation angle are used to correct the initial compensation amount, and the final tensioning command is simultaneously constrained by the measured opening value, the total edge compressive stress of the joint and the anchorage bearing margin.

5. The system according to claim 1, characterized in that, The initial compensation amount of each measuring point is estimated based on the joint opening increment, chlorine corrosion index and eccentric rotation angle; when the absolute difference of the compensation amount of adjacent measuring points is no greater than 5% to 15% of the larger value and is continuous along the circumference of the joint, they are merged into the same pre-tightening zone; the boundary of the pre-tightening zone is determined in combination with the original or reserved duct, external guide component and anchoring position, the pre-tightening zone of the circular section is set continuously along the circumference, and the boundary of the pre-tightening zone of the rectangular or irregular section corresponds to the corner, edge or disease concentration area.

6. The system according to claim 1, characterized in that, Unbonded steel strands are threaded through existing or pre-reserved ducts, or, after reinforcement detection and structural calculation, cross joints via external guide components. The controllable tensioner includes a tensioning drive, a tension force sensor, and a displacement feedback component. The anchoring end is equipped with a force-measuring component that monitors the holding force during mechanical locking. The anchor is equipped with a repeatedly adjustable mechanical locking structure and a locking status detection component. After each level of tensioning is completed, the anchor and the mechanical locking structure maintain the preload. The tensioner is not used as a long-term load-bearing component. During readjustment, the tensioner first bears the load of the steel strand. After confirming the load bearing and locking status, the corresponding mechanical locking is released, controlled adjustment is performed, and the tensioner is relocked. After the holding force is checked, the working load of the tensioner is removed. If the anchor slips, the force value deviates, or the local bearing pressure check does not meet the requirements, the load increase in the corresponding area is stopped.

7. The system according to claim 1, characterized in that, The load for low-load synchronous positioning is 5% to 15% of the rated allowable tension of each pre-tensioning zone; then it is increased in stages according to a preset ratio not exceeding the remaining allowable tension of each zone. After each stage of increase, the actual tension, cross-joint displacement and eccentric rotation angle are read and the total edge compressive stress of the joint is checked; after the opening and compressive stress are stable for several consecutive sampling cycles and the anchoring status is confirmed, the mechanical locking state is maintained or low-frequency monitoring is entered. No new load increase command is executed during power supply or communication interruption.

8. The system according to claim 1, characterized in that, The available load margin is the difference between the rated allowable tension force of the adjacent bearing zone and the current preload force; the equivalent normal force transmission stiffness between the over-limit zone and the adjacent bearing zone is determined by the over-limit zone closure displacement caused by the small adjustment of the adjacent zone, the local normal stiffness of the over-limit zone, and the equivalent axial adjustment displacement of the adjacent zone, and only the positive coupling value that can promote the closure of the over-limit zone is used; the product weight is the ratio of the product of the equivalent normal force transmission stiffness and the available load margin to the sum of the corresponding products of all participating distribution zones, and the single transfer amount is simultaneously limited by the load margin, the preset adjustment step size, and the total edge compressive stress check result of the entire zone. The remaining amount after the limitation is only redistributed in other bearing zones; when there is no adjacent zone that meets the requirements of total edge compressive stress, steel strand, anchorage, and local bearing pressure margin, the verified safe load is maintained and a manual verification prompt is output.

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