Online monitoring and early warning system for fastening degree of steel column foundation bolt with inserted bearing platform

Abstract

The application discloses an online monitoring and early warning system for fastening degree of a pile cap plug-in type steel column foundation bolt, and relates to the technical field of building structure health monitoring, which comprises the following modules: a collection module for collecting calibration deformation response; a calibration module for extracting positive and negative calibration critical loads when a contact boundary reaches a projection position of an outer edge of a steel column; calculating calibration critical load difference in positive and negative directions, and establishing a residual pre-tightening force calibration relationship corresponding to known pre-tightening force; a monitoring module for collecting monitoring deformation response; monitoring contact pressure by monitoring deformation response and contact flexibility, extracting positive and negative monitoring critical loads, and calculating monitoring critical load difference; and an early warning module for identifying residual pre-tightening force according to monitoring critical load difference and the residual pre-tightening force calibration relationship, and outputting an early warning signal when a force transmission path corresponding to the monitoring contact pressure is disconnected in a projection area of a compression side section of the steel column.

Description

Technical Field

[0001] This invention relates to the field of building structure health monitoring technology, specifically an online monitoring and early warning system for the tightness of anchor bolts in pier foundation steel columns. Background Technology

[0002] In a pier-type steel column base connection structure, the anchor bolts, through pre-tightening, maintain compressive contact between the column base plate and the pier, creating initial constraints at the column base connection. After the steel column enters service, the superstructure load is transferred through the column body to the column base area. The contact state between the column base plate and the pier changes with the load and the pre-tightening force. When the anchor bolt tightness decreases, the force transmission state at the column base connection changes, thus affecting the performance of the connection area.

[0003] Current online monitoring of anchor bolt tightness typically uses bolt axial force measurements as the evaluation criterion. While this method reflects the axial force borne by the bolts at the moment of measurement, it is difficult to directly characterize the remaining tightness of anchor bolts when the service load on the steel column is continuous, as the measured axial force is simultaneously affected by external load transmission and preload decay. Furthermore, if the monitoring process does not establish a verifiable correlation with the stress response in the column base connection area, the warning results are prone to deviating from the actual force transmission state of the column base, failing to meet the application requirements for long-term online monitoring of anchor connections in pier-type steel columns. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art; to this end, the present invention proposes an online monitoring and early warning system for the tightness of anchor bolts of pier-type steel columns.

[0005] To achieve the above objectives, the present invention provides an online monitoring and early warning system for the tightness of anchor bolts in pier cap steel columns, comprising: The acquisition module is used to apply positive and negative static loads along the loading axis according to the known preload condition and to acquire and calibrate the deformation response. The calibration module is used to invert the calibration of the contact pressure from the calibration deformation response and contact compliance, extract the forward and reverse calibration critical loads when the contact boundary reaches the projection position of the outer edge of the steel column; calculate the calibration critical load difference by subtracting the reverse direction from the forward direction, and establish the remaining preload calibration relationship corresponding to the known preload; The monitoring module is used to collect and monitor deformation response under repeated forward and reverse static loads when the service load is constant; the monitoring contact pressure is inverted from the monitored deformation response and contact flexibility, the critical loads for forward and reverse monitoring are extracted, and the difference between the critical loads for monitoring is calculated. The early warning module is used to identify the remaining preload based on the relationship between the monitored critical load difference and the remaining preload calibration; when the force transmission path corresponding to the monitored contact pressure is broken in the projection area of ​​the compression side section of the steel column, an early warning signal is output.

[0006] Compared with the prior art, the beneficial effects of the present invention are: This invention applies forward and reverse static loads along the same loading axis under known preload conditions. Contact pressure is inverted based on calibrated deformation response and contact compliance. The remaining preload calibration relationship is established using the difference between the forward and reverse critical loads when the contact boundary reaches the projected position of the steel column's outer edge. This creates a verifiable correspondence between the preload state and the column base contact response. During service monitoring, the same loading process is repeated under constant load conditions. The forward load is used to offset the common offset caused by the constant service load, and the connection status of the force transmission path in the pressure-bearing side projection area is combined to output early warnings. This helps reduce judgment errors caused by the influence of external loads on the axial force of a single bolt. Attached Figure Description

[0007] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0008] Figure 1 This is a block diagram of the system of the present invention. Detailed Implementation

[0009] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0010] Please see Figure 1 This embodiment provides an online monitoring and early warning system for the tightness of anchor bolts in pier cap steel columns, including: The acquisition module 101 is used to apply positive and negative static loads along the loading axis according to the known preload condition and to acquire and calibrate the deformation response. Calibration module 102 is used to invert the calibration contact pressure from the calibration deformation response and contact compliance, extract the forward and reverse calibration critical loads when the contact boundary reaches the projection position of the outer edge of the steel column; calculate the calibration critical load difference by subtracting the reverse direction from the forward direction, and establish the remaining preload calibration relationship corresponding to the known preload; Monitoring module 103 is used to repeatedly perform forward and reverse static loads when the service load is constant, collect and monitor deformation response; invert the monitored contact pressure from the monitored deformation response and contact flexibility, extract the forward and reverse monitoring critical loads and calculate the monitoring critical load difference; The early warning module 104 is used to identify the remaining preload based on the relationship between the monitoring critical load difference and the remaining preload calibration; when the force transmission path corresponding to the monitoring contact pressure is broken in the projection area of ​​the compression side section of the steel column, an early warning signal is output.

[0011] In practical implementation, the pier-type inserted steel column includes a steel column, a column base plate, a pier, and anchor bolts. The column base plate is set on the top surface of the pier, and the anchor bolts pass through the column base plate and are anchored inside the pier. A contact surface is formed between the column base plate and the pier. The projected outline of the outer edge of the steel column section, the centroid of the column base plate, the loading axis, the load application point, the deformation measuring point, and the contact element are determined before calibration and remain consistent during the calibration and monitoring processes.

[0012] In one specific approach, the column base plate is a rectangular steel plate, the steel column is an H-shaped steel column, and there are four anchor bolts. The total preload of the four anchor bolts is used as the remaining preload identification object. The dimensions of the column base plate, the cross-sectional dimensions of the steel column, the arrangement of the anchor bolts, the material parameters of the foundation, the material parameters of the column base plate, the location of deformation measuring points, and the results of contact element division are all pre-entered as system parameters. The above system parameters provide a unified geometric and mechanical benchmark for subsequent calibration, inversion, monitoring, and early warning.

[0013] Specifically, the acquisition module 101 operates during the calibration phase. In this phase, a known preload is first applied to the anchor bolts to press the column base plate tightly against the bearing platform. The known preload is applied by a preload device and recorded by an axial force gauge or preload calibration device. For each known preload condition, both forward and reverse static loads are applied. The known preload value, actual static load value, and normal displacement measurement constitute the data source for the calibration phase; the acquisition module 101 outputs the calibration deformation response under each known preload condition.

[0014] Furthermore, the forward and reverse static loads are applied by a loading device. The loading device records the actual static load value for each loading level. Deformation measuring points are set at the column base plate, and displacement is measured along the normal direction of the column base plate. After each loading level reaches the target static load value, the acquisition module 101 records the normal displacement measurement values ​​of all deformation measuring points. All normal displacement measurement values ​​are arranged according to fixed measuring point numbers to form the calibration deformation response for the corresponding loading level.

[0015] The positive and negative static loads are applied to the same load point on the steel column body and are applied in the opposite direction along the loading axis passing through the centroid of the column base plate; the projected position of the outer edge of the steel column is the two intersection points formed by the loading axis and the projected outline of the outer edge of the steel column section.

[0016] In this embodiment, the load application point is located at a predetermined height on the steel column. Both the positive and negative static loads are applied to this load application point. The loading axis lies in the plane of the column base plate and passes through the centroid of the column base plate. The positive static load is applied along the positive direction of the loading axis, and the negative static load is applied along the negative direction of the loading axis. The same load application point and the same loading axis ensure that the positive and negative static loads have the same lever arm reference, which can reduce the influence of the difference in loading position on the critical load extraction.

[0017] The projected profile of the outer edge of the steel column section is the projected profile of the outer boundary of the steel column section onto the column base plate. The loading axis intersects with the projected profile of the outer edge of the steel column section, forming two intersection points. These two intersection points are the projected positions of the outer edge of the steel column. Under positive loading, one intersection point corresponds to the projected position of the outer edge of the steel column on the positive tension side; under negative loading, the other intersection point corresponds to the projected position of the outer edge of the steel column on the negative tension side. The two projected positions of the outer edge of the steel column are determined by the geometry of the column base and do not change with the loading level.

[0018] Specifically, the calibration module 102 receives the calibration deformation response output by the acquisition module 101 and calls the pre-established contact compliance. The contact compliance represents the influence of unit pressure at each location on the normal displacement of each deformation measuring point. The calibration module 102 uses the calibration deformation response as a known quantity and the contact pressure on the contact surface as the unknown quantity to solve for the calibration contact pressure corresponding to each loading level. A positive calibration contact pressure indicates that the column base plate and the foundation transmit normal pressure; a zero calibration contact pressure indicates that no normal pressure is transmitted at that location.

[0019] As the positive static load increases progressively, the contact pressure on the compression side increases, while the contact pressure on the tension side decreases. With each change in loading level, the calibrated contact pressure at the projected location of the outer edge of the steel column changes from a positive value to zero. This zero-value transition indicates that the contact boundary has reached the projected location of the outer edge of the steel column. The calibration module 102 extracts the positive and negative calibration critical loads based on this zero-value transition. Subsequently, the calibration module 102 subtracts the negative calibration critical load from the positive calibration critical load to obtain the calibration critical load difference, and stores this difference in association with the corresponding known preload. This association links the preload action, contact boundary migration, and critical load difference, facilitating subsequent identification of the remaining preload by monitoring the critical load difference.

[0020] It should be noted that the calibration module 102 first inverts the calibration contact pressure, and then extracts the critical load when the contact boundary reaches the projected position of the outer edge of the steel column. This process converts the deformation data of multiple measuring points into a contact pressure distribution, avoiding the direct inference of the anchor bolt tightness based on the displacement of a single measuring point.

[0021] Specifically, establishing the remaining preload calibration relationship includes: When establishing the calibration relationship for residual preload, each known preload condition uses the same contact element division, the same deformation measurement point numbering, the same contact compliance, and the same critical load extraction rules. Each known preload condition corresponds to a calibration critical load difference. The known preloads and their corresponding calibration critical load differences together constitute the residual preload calibration relationship. The data sources for this relationship are the inversion results of forward and reverse static loads, calibration deformation response, contact compliance, and calibration contact pressure under the known preload conditions; the output is the calibration correspondence relationship available for use in the monitoring phase.

[0022] The contact surface between the column base plate and the foundation is divided into multiple contact units, and a contact compliance matrix is ​​constructed based on the unit pressure displacement response of each contact unit. The contact surface between the column base plate and the foundation is divided into multiple contact elements according to a fixed grid. Specifically, the contact surface is divided into 4 columns along the loading axis and 3 rows perpendicular to the loading axis, forming a total of 12 contact elements. Each contact element has a fixed number, fixed area, and fixed geometric position. The contact element where the outer edge of the steel column is projected is determined based on geometric coordinates. If the projected position of the outer edge of the steel column is located on the boundary between two contact elements, the equivalent contact pressure is determined according to the area weight of the adjacent contact elements in their neighborhood at that position. This division method ensures that the geometric critical position corresponds to the contact pressure inversion result.

[0023] The contact compliance matrix is ​​constructed using the unit pressure displacement response. A unit normal pressure is applied to the first contact element, while no unit normal pressure is applied to the other contact elements. The normal displacement response of all deformation measurement points is recorded; this set of displacement responses forms one column of the contact compliance matrix. Subsequently, the same unit normal pressure is applied to the remaining contact elements sequentially, and the normal displacement response of all deformation measurement points is recorded for each. The columns are then arranged according to the contact element number to obtain the contact compliance matrix.

[0024] The contact compliance matrix is ​​expressed as: in, For the contact compliance matrix; This represents the number of deformation measurement points. This refers to the number of contact units; For the first When the contact unit is subjected to a unit normal pressure, the first The normal displacement response generated by each deformation measuring point.

[0025] The contact compliance matrix is ​​obtained from the column base elastic calculation model or from a calibration specimen consistent with the actual column base structure. The data required for calculation or testing includes the dimensions of the column base plate, the elastic modulus of the steel, the elastic modulus of the foundation material, the geometric positions of the contact elements, and the locations of deformation measurement points. The matrix representation establishes a quantitative correspondence between contact pressure and measurement point displacement, providing a clear basis for inversion calculations.

[0026] The calibrated deformation response is composed into a displacement vector according to the location of the deformation measurement point; the displacement vector is approximated by the product of the contact compliance matrix and the contact pressure vector, and the least squares solution is performed under the non-negative contact pressure constraint to obtain the calibrated contact pressure. Furthermore, at each loading level, the calibration module 102 arranges the normal displacement measurements of each deformation measuring point according to the fixed measuring point number to form a displacement vector: in, It is the displacement vector; For the first The normal displacement measurement value of each deformation measuring point.

[0027] The contact pressure vector is represented as: in, This is the contact pressure vector; For the first Contact pressure of each contact unit.

[0028] Calibration module 102 solves: in, To calculate the squared error between the displacement and the measured displacement; constraints. This indicates that the contact surface can only transmit normal compressive forces, not normal tensile forces. The contact compressive vector obtained by solving is the calibrated contact compressive force for the corresponding loading level. The non-negative constraint can eliminate tensile force solutions that do not conform to the contact force mechanism, ensuring that the calibrated contact compressive force is consistent with the force state between the column base plate and the foundation.

[0029] The non-negative least squares algorithm is used for the solution. If a contact element corresponds to a negative pressure in the unconstrained solution, the pressure of that contact element is fixed to zero, and the solution continues for the remaining unknown contact pressures until all contact pressures satisfy the non-negative constraint. The input to this calculation process is the contact compliance matrix and displacement vector, and the output is the calibrated contact pressure of each contact element. The data sources and calculation results can be correlated step by step.

[0030] The deformation measuring points measure displacement along the normal direction of the column base plate, the number of deformation measuring points is greater than or equal to the number of contact units, and the column rank of the contact flexibility matrix is ​​equal to the number of contact units.

[0031] In this embodiment, the displacement is measured along the normal direction of the column base plate at the deformation measuring points, ensuring that the displacement measurement direction corresponds to the contact pressure direction. The number of deformation measuring points is greater than or equal to the number of contact elements, ensuring that the number of displacement equations is not less than the number of contact pressures to be determined. The column rank of the contact compliance matrix is ​​equal to the number of contact elements, making the unit pressure displacement response of each contact element distinguishable. This improves the stability of contact pressure inversion and reduces the risk of different contact pressure distributions producing the same displacement fitting results.

[0032] The critical loads for forward and reverse calibration are determined by converting the zero value of the contact pressure at the projected position of the outer edge of the steel column; the difference between the critical load for forward calibration and the critical load for reverse calibration is corresponding to the known preload to form the remaining preload calibration relationship.

[0033] Furthermore, after the calibration contact pressure is calculated, the calibration module 102 processes the forward loading data and the reverse loading data respectively. In the forward loading data, the calibration contact pressure at the projected location of the outer edge of the steel column on the forward tension side is extracted, and load-contact pressure data is generated according to the loading level sequence. In the reverse loading data, the calibration contact pressure at the projected location of the outer edge of the steel column on the reverse tension side is extracted, and load-contact pressure data is generated according to the loading level sequence. When the calibration contact pressure at the above locations changes from a positive value to zero, the calibration module 102 determines the calibration critical load in the corresponding direction.

[0034] The positive calibration critical load is denoted as The reverse calibration critical load is denoted as The calibrated critical load difference is denoted as... The calculation formula is: In this method, the critical load for reverse calibration is recorded with the sign of the reverse loading direction. The calculation method of forward minus reverse retains the load span between the forward and reverse critical states, which can reduce the impact of constant eccentric load on subsequent preload identification.

[0035] The step of determining the critical load for forward and reverse calibration based on the zero value conversion of the calibrated contact pressure at the projected position of the outer edge of the steel column includes: Specifically, the calibration module 102 applies the same rules to both forward and reverse loading data. The processing object is the calibration contact pressure at the projected position of the outer edge of the steel column on the tension side in the corresponding direction. When the calibration contact pressure at this position becomes zero, it indicates that the contact boundary has reached the projected position of the outer edge of the steel column.

[0036] Select the two consecutive positive pressure loading stages before the calibrated contact pressure changes to zero; The calibration module 102 checks the calibrated contact pressure at the projected position of the outer edge of the steel column according to the loading level sequence. If the calibrated contact pressure of a certain loading level is zero, and there are two consecutive loading levels with positive calibrated contact pressures preceding this loading level, then these two loading levels are selected as the interpolation basis. Two consecutive positive pressure loading levels refer to two adjacent loading levels in the loading level sequence, and the corresponding calibrated contact pressures are both greater than zero. This selection rule ensures that the interpolated data is within the zero-value transition neighborhood, which can reduce the impact of the loading level interval on the extraction of critical loads.

[0037] A load-contact pressure line is established based on two positive pressure loading levels, and the loading parameter corresponding to the intersection of the load-contact pressure line and the zero contact pressure line is determined as the calibration critical load. The forward loading data and the reverse loading data are processed respectively to obtain the forward calibration critical load and the reverse calibration critical load.

[0038] Furthermore, let the loading parameters of the two consecutive positive pressure loading stages be respectively... and The corresponding calibrated contact pressures are respectively and ,and , Based on two points and Establish a load-contact pressure straight line. The intersection of this line and the zero contact pressure line corresponds to the calibration of the critical load. Calculate using the following formula: in, To calibrate the critical load; and These are the loading parameters for two consecutive positive pressure loading stages; and To correspond to the calibration contact pressure, calibration module 102 processes the forward loading data and reverse loading data respectively to obtain the forward calibration critical load and the reverse calibration critical load.

[0039] After processing each known preload condition, the calibration module 102 associates and stores each set of known preloads with the corresponding calibration critical load difference, forming a residual preload calibration relationship. Each set of data in the residual preload calibration relationship comes from known preload, forward and reverse static loads, calibration deformation response, contact compliance matrix, and zero-value conversion calculations, which can provide quantitative basis for the monitoring stage.

[0040] Specifically, after the steel column enters service, the monitoring module 103 monitors it during the constant service load period. The monitoring phase uses the load application point, loading axis, loading level sequence, deformation measurement point number, contact element division results, and contact compliance matrix from the calibration phase. The monitoring module 103 collects the normal displacement measurements under each loading level and compiles them into a monitoring deformation response; simultaneously, it records the actual static load value, column top axial force measurement value, and column top bending moment measurement value for each loading level. The outputs of the monitoring phase are the monitoring contact pressure, the forward monitoring critical load, the reverse monitoring critical load, and the monitoring critical load difference.

[0041] The inversion process for monitoring contact pressure is consistent with the inversion process for calibrating contact pressure. Let the monitored displacement vector be... The monitored contact pressure vector is Then solve: in, To monitor the displacement vector; To monitor the contact pressure vector; For the first The monitoring contact pressure of each contact unit is measured. Using the same contact flexibility and the same non-negative constraint ensures that the monitored contact pressure and the calibrated contact pressure have consistent mathematical and physical meanings, guaranteeing that the difference in the monitored critical load corresponds to the calibrated relationship of the remaining preload.

[0042] The monitoring process of the monitoring module uses the same load application point, loading axis and loading stage sequence as the known preload condition; the column top axial force measurement values ​​before positive loading, before reverse loading and after monitoring are equal, and the column top bending moment measurement values ​​are equal.

[0043] In this embodiment, the measured values ​​of the column top axial force before positive loading, before reverse loading, and after monitoring are all equal, and the measured values ​​of the column top bending moment are also equal, indicating that the service load did not change during the monitoring period. If the above measured values ​​are not equal, the monitoring data will not be included in the remaining preload identification calculation, and data will be collected again during a constant service load period.

[0044] When the service load is constant, the service load component along the loading axis will cause the forward and reverse monitoring critical loads to shift in the same direction. Let the constant component of the service load along the forward direction be... ,but: therefore: in, To monitor critical loads in a positive direction; To monitor critical loads in reverse; To monitor the critical load difference. This relationship shows that monitoring the critical load difference can offset the common translation caused by constant service load, preserving the load span corresponding to the remaining preload.

[0045] Specifically, the calculation and monitoring of the critical load difference includes: Furthermore, after obtaining the monitored contact pressure, the monitoring module 103 processes the forward loading data and the reverse loading data respectively. The forward loading data is used to determine the forward monitoring critical load, and the reverse loading data is used to determine the reverse monitoring critical load. Both directions are extracted based on the zero-value conversion of the monitored contact pressure at the projected position of the outer edge of the steel column.

[0046] Two consecutive positive pressure loading levels were selected at the outer edge projection position of the steel column during positive and negative loading, respectively, before the contact pressure turned to zero; the critical loads for positive and negative monitoring were determined based on the two corresponding positive pressure loading levels. Specifically, during forward loading, monitoring module 103 checks the contact pressure at the projected location of the outer edge of the steel column on the tension side in sequence according to the loading levels. When the contact pressure at this location changes from positive to zero, two consecutive positive pressure loading levels before the zero-value transition are selected, and a load-contact pressure straight line is established based on these two loading levels. The intersection of this straight line and the zero contact pressure line corresponds to the forward monitoring critical load. During reverse loading, monitoring module 103 determines the reverse monitoring critical load according to the same rules. The same interpolation rules ensure that the forward and reverse critical loads have consistent discrete data processing standards.

[0047] The difference between the critical load for forward monitoring and the critical load for reverse monitoring is defined as the critical load difference.

[0048] Among them, monitoring module 103 calculates the critical load difference by subtracting the reverse load from the forward load: in, To monitor the critical load difference; To monitor critical loads in a positive direction; This is for reverse monitoring of critical loads. The difference in critical loads is used as the basis for the calculation of the remaining preload in the early warning module 104.

[0049] Specifically, the early warning module 104 receives the monitored critical load difference and invokes the remaining preload calibration relationship. Based on the position of the monitored critical load difference within the calibrated critical load difference interval, the early warning module 104 obtains the remaining preload. Simultaneously, based on the monitored contact pressure at the endpoints of the forward and reverse static loads, the early warning module 104 checks whether a continuous force transmission path exists within the projection area of ​​the steel column's compression side section. This setting allows the early warning signal to reflect the anchor bolt tightness and the continuity of the contact force transmission path, based on both the remaining preload identification result and the connectivity of the contact force transmission path.

[0050] Specifically, the step of identifying the remaining preload based on the monitoring critical load difference and the remaining preload calibration relationship includes: In practical implementation, the early warning module 104 first arranges the remaining preload calibration relationships according to the calibration critical load difference. If the monitored critical load difference is equal to a certain calibration critical load difference, the known preload corresponding to that calibration critical load difference is determined as the remaining preload. If the monitored critical load difference is located between two adjacent calibration critical load differences, the remaining preload is calculated according to the interval position ratio.

[0051] A set of known preloads and corresponding critical load differences in the remaining preload calibration relationship are determined as a calibration point, and the critical load difference interval is determined to include two adjacent calibration points for monitoring the critical load difference. The early warning module 104 identifies each known preload and its corresponding critical load difference as a calibration point, and searches for the calibration critical load difference interval containing the monitored critical load difference in the remaining preload calibration relationship. The calibration points located at both ends of this interval are considered two adjacent calibration points. Adjacent calibration points limit the interpolation range and can avoid deviations in the correspondence caused by cross-interval calculations.

[0052] Determine the position ratio of the monitoring critical load difference within the calibrated critical load difference interval, and map the preload interval between two adjacent calibration points according to the position ratio to obtain the remaining preload.

[0053] Furthermore, let the difference in the critical load between two adjacent calibration points be respectively... and The corresponding known preloads are as follows: and The critical load difference is monitored. Positional proportions for: Remaining preload for: in, To monitor the proportion of the critical load difference within the calibrated critical load difference range; The remaining preload is used as the quantitative identification result of the current tightness of the anchor bolts by the early warning module 104. This mapping method calculates the remaining preload using adjacent calibration intervals, which can maintain local consistency between the identification result and the calibration relationship.

[0054] Specifically, the step of outputting a warning signal when the force transmission path corresponding to the monitored contact pressure is broken within the projection area of ​​the compression side section of the steel column includes: In practical implementation, after obtaining the remaining preload, the early warning module 104 continues to process the monitored contact pressure at the endpoints of the forward static load and the reverse static load. The endpoint of the forward static load is the last loading stage in the forward loading stage sequence, and the endpoint of the reverse static load is the last loading stage in the reverse loading stage sequence. The contact pressure distribution at the endpoints is used to characterize the compressive force transmission state between the column base plate and the foundation under the corresponding loading direction.

[0055] Contact elements with positive pressure at the endpoints of the forward and reverse static loads are extracted to form forward and reverse monitoring contact areas; forward and reverse contact connectivity diagrams are established according to the common edge relationship of the contact elements. The early warning module 104 extracts contact units with positive monitoring contact pressure at the endpoint of the forward static load, forming a forward monitoring contact area. Each contact unit in the forward monitoring contact area is considered a node. When two contact units share a common edge, a connection is established between the corresponding nodes, forming a forward contact connectivity graph. The same method is used at the endpoint of the reverse static load to form a reverse monitoring contact area and a reverse contact connectivity graph. A common edge relationship means that two contact units share a common boundary line segment; corner contact alone does not constitute a common edge relationship. This limitation ensures that the contact connectivity graph corresponds to continuous surface contact, reflecting the spatial continuity of the pressure transmission path.

[0056] In each contact connectivity diagram, the contact element intersecting with the first side boundary of the projected area of ​​the compression side section of the steel column is defined as the first boundary node group, and the contact element intersecting with the second side boundary is defined as the second boundary node group; when the two boundary node groups in any contact connectivity diagram belong to different connectivity components, an early warning signal is output.

[0057] Furthermore, for the positive contact connectivity diagram, the early warning module 104 determines the projection area of ​​the compression side section of the steel column based on the positive static load direction. In the positive contact connectivity diagram, the contact element intersecting with the first side boundary is determined as the first boundary node group; the contact element intersecting with the second side boundary is determined as the second boundary node group. If the two boundary node groups belong to different connectivity components, it indicates that the force transmission path within the projection area of ​​the compression side section of the steel column at the end of the positive static load is broken, and the early warning module 104 outputs an early warning signal.

[0058] For the reverse contact connectivity diagram, the early warning module 104 determines the projection area of ​​the compression side section of the steel column according to the reverse static load direction, and uses the same rules to determine the first boundary node group and the second boundary node group. If the two boundary node groups in any contact connectivity diagram belong to different connectivity components, an early warning signal is output. This judgment can identify interruptions in the compressive force transmission path under a single loading direction, avoiding outputting an early warning based solely on the remaining preload value.

[0059] As a necessary explanation, if the projection area of ​​the compression section of a steel column covers multiple sequentially shared contact elements along a direction perpendicular to the loading axis, and the contact element located in the middle position monitors zero contact pressure, then the contact elements on both sides with positive pressure cannot be connected through their shared edge relationship. In this case, if the first boundary node group and the second boundary node group are located within the contact elements on both sides with positive pressure, then the two boundary node groups belong to different connected components, and the early warning module 104 outputs an early warning signal. This example is used to illustrate the method of determining connected components and does not limit the number of contact elements or the shape of the projection area.

[0060] Wherein, the projection area of ​​the compression side section of the steel column is the projection range of the compression side section of the steel column in the corresponding static load direction on the column base plate; the first side boundary and the second side boundary are two boundaries of the projection area of ​​the compression side section of the steel column that are set opposite each other along the direction perpendicular to the loading axis.

[0061] In this embodiment, the projection area of ​​the compression side section of the steel column is determined according to the direction of the static load. A positive static load corresponds to the projection area of ​​the positive compression side section, and a negative static load corresponds to the projection area of ​​the negative compression side section. The first and second side boundaries are set opposite each other along a direction perpendicular to the loading axis to define the lateral range where continuous compressive force transmission needs to be maintained. The early warning module 104 uses whether the two boundary node groups belong to the same connected component as the criterion for determining whether the force transmission path is broken. This determination is directly derived from monitoring the contact pressure and the shared edge relationship of the contact units.

[0062] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An online monitoring and early warning system for the tightness of anchor bolts in a foundation-type steel column, characterized in that, include: The acquisition module is used to apply positive and negative static loads along the loading axis according to the known preload condition and to acquire and calibrate the deformation response. The calibration module is used to invert the calibration of the contact pressure from the calibration deformation response and contact compliance, extract the forward and reverse calibration critical loads when the contact boundary reaches the projection position of the outer edge of the steel column; calculate the calibration critical load difference by subtracting the reverse direction from the forward direction, and establish the remaining preload calibration relationship corresponding to the known preload; The monitoring module is used to collect and monitor deformation response under repeated forward and reverse static loads when the service load is constant. The contact pressure is inverted from the monitored deformation response and contact flexibility, and the critical loads in the forward and reverse directions are extracted and the difference between the critical loads is calculated. The early warning module is used to identify the remaining preload based on the relationship between the monitored critical load difference and the remaining preload calibration; when the force transmission path corresponding to the monitored contact pressure is broken in the projection area of ​​the compression side section of the steel column, an early warning signal is output.

2. The system according to claim 1, characterized in that, The positive and negative static loads are applied to the same load point on the steel column body and are applied in the opposite direction along the loading axis passing through the centroid of the column base plate; the projected position of the outer edge of the steel column is the two intersection points formed by the loading axis and the projected outline of the outer edge of the steel column section.

3. The system according to claim 1, characterized in that, The establishment of the remaining preload calibration relationship includes: The contact surface between the column base plate and the foundation is divided into multiple contact units, and a contact compliance matrix is ​​constructed based on the unit pressure displacement response of each contact unit. The calibrated deformation response is composed into a displacement vector according to the location of the deformation measurement point; the displacement vector is approximated by the product of the contact compliance matrix and the contact pressure vector, and the least squares solution is performed under the non-negative contact pressure constraint to obtain the calibrated contact pressure. The critical loads for forward and reverse calibration are determined by converting the zero value of the contact pressure at the projected position of the outer edge of the steel column; the difference between the critical load for forward calibration and the critical load for reverse calibration is corresponding to the known preload to form the remaining preload calibration relationship.

4. The system according to claim 3, characterized in that, The deformation measuring points measure displacement along the normal direction of the column base plate. The number of deformation measuring points is greater than or equal to the number of contact units, and the column rank of the contact flexibility matrix is ​​equal to the number of contact units.

5. The system according to claim 3, characterized in that, The determination of the critical load for forward and reverse calibration based on the zero value conversion of the calibrated contact pressure at the projected position of the outer edge of the steel column includes: Select the two consecutive positive pressure loading stages before the calibrated contact pressure changes to zero; A load-contact pressure line is established based on two positive pressure loading levels, and the loading parameter corresponding to the intersection of the load-contact pressure line and the zero contact pressure line is determined as the calibration critical load. The forward loading data and the reverse loading data are processed respectively to obtain the forward calibration critical load and the reverse calibration critical load.

6. The system according to claim 1, characterized in that, The monitoring process of the monitoring module uses the same load application point, loading axis and loading stage sequence as the known preload condition; the column top axial force measurement values ​​before positive loading, before reverse loading and after monitoring are equal, and the column top bending moment measurement values ​​are equal.

7. The system according to claim 1, characterized in that, The calculation and monitoring of the critical load difference includes: Two consecutive positive pressure loading levels were selected at the outer edge projection position of the steel column during both positive and negative loading, before the contact pressure turned to zero. The critical loads for positive and negative monitoring were determined based on the two corresponding positive pressure loading levels. The difference between the critical load for forward monitoring and the critical load for reverse monitoring is defined as the critical load difference.

8. The system according to claim 1, characterized in that, The step of identifying the remaining preload based on the relationship between the monitored critical load difference and the remaining preload calibration includes: A set of known preloads and corresponding critical load differences in the remaining preload calibration relationship are determined as a calibration point, and the critical load difference interval is determined to include two adjacent calibration points for monitoring the critical load difference. Determine the position ratio of the monitoring critical load difference within the calibrated critical load difference interval, and map the preload interval between two adjacent calibration points according to the position ratio to obtain the remaining preload.

9. The system according to claim 1, characterized in that, The method of outputting an early warning signal when the force transmission path corresponding to the monitored contact pressure is broken within the projection area of ​​the compression side section of the steel column includes: Contact elements with positive pressure at the endpoints of the forward and reverse static loads are extracted to form forward and reverse monitoring contact areas; forward and reverse contact connectivity diagrams are established according to the common edge relationship of the contact elements. In each contact connectivity diagram, the contact element intersecting with the first side boundary of the projected area of ​​the compression side section of the steel column is defined as the first boundary node group, and the contact element intersecting with the second side boundary is defined as the second boundary node group; when the two boundary node groups in any contact connectivity diagram belong to different connectivity components, an early warning signal is output.

10. The system according to claim 9, characterized in that, The projection area of ​​the compression side section of the steel column is the projection range of the compression side section of the steel column in the static load direction on the column base plate; the first side boundary and the second side boundary are two boundaries of the projection area of ​​the compression side section of the steel column that are set opposite each other along the direction perpendicular to the loading axis.

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