Performance evaluation method for friction pendulum type seismic mitigation and isolation support in service state

Abstract

The invention discloses a method for evaluating the performance of a friction pendulum type seismic mitigation and isolation support in a service state. The method comprises the following steps: S1, carrying out horizontal sliding displacement and vertical force detection on the friction pendulum type seismic mitigation and isolation support in service; s2, according to the detected data, the sliding interface friction coefficient mu of the service friction pendulum type seismic mitigation and isolation support is calculated; s3, according to the obtained sliding interface friction coefficient mu of the in-service friction pendulum type seismic mitigation and isolation support, anti-seismic performance indexes of the friction pendulum type seismic mitigation and isolation support are calculated, and the anti-seismic performance indexes comprise the horizontal rigidity and the effective damping ratio coefficient; and S4, according to the influence of the sliding interface state change and the horizontal rigidity change on the seismic damage state of the bridge structure, the anti-seismic safety risk of the friction pendulum type seismic mitigation and isolation support in the sliding interface state is graded. By means of the method, the sliding interface state and the specific friction characteristic of the friction pendulum type seismic mitigation and isolation support in the service state can be obtained, and therefore the anti-seismic performance of the friction pendulum type seismic mitigation and isolation support can be evaluated.

Description

Technical Field

[0001] The present invention relates to the technical field of seismic safety and inspection and evaluation of bridges. More specifically, the present invention relates to a method for evaluating the performance of a friction pendulum isolation bearing in service. Background Art

[0002] In order to reduce the seismic damage risk of bridge structures under earthquake actions, the seismic design of highway bridges has shifted from structural seismic reduction based on life safety to the recoverability of post-earthquake structural functions and rapid repair. Among them, the isolation system bridge is a typical seismic system for highway bridges in China. That is, the isolation bearing is used to exert its isolation and energy dissipation functions to protect the substructure and the main girder from damage or minor damage, and to meet the requirements of post-disaster emergency, damage repair, rapid repair, traffic capacity recovery, etc. Therefore, the isolation device is the key and vulnerable part for such bridges to achieve their seismic fortification goals.

[0003] As a bearing widely used in current practical engineering, the friction pendulum isolation bearing is affected by multiple factors such as vehicle loads, impact loads, wind, temperature, and corrosion during its service life, and its service state gradually deteriorates, bringing more uncertainties and potential hazards to the safety of bridge structures during the operation period and their seismic safety. In order to timely and accurately judge the seismic capacity or safety risk level of isolation bridges at different service periods, further formulate scientific and reasonable bridge seismic safety hazard investigation, disposal, and seismic resilience improvement plans, and reduce their seismic safety risks, it is crucial to master the service state and its deterioration law of the friction pendulum isolation bearing.

[0004] Currently, the current "Technical Condition Assessment Standard for Highway Bridges" (JTG / T H1-2011) and "Code for Inspection and Assessment of Bearing Capacity of Highway Bridges" (JTG / T J21-2011) do not cover the inspection and assessment of friction pendulum isolation bearings, which seriously restricts the development of work such as the inspection and assessment of the safety performance of such bridge structures. In the actual bridge inspection and assessment process, for friction pendulum isolation bearings, only visual inspections are carried out, such as rust and sliding. Since the inspection personnel do not understand the working principle of the friction pendulum isolation bearing, the detection or monitoring of the continuous deformation of the relevant bearings is ignored, resulting in a lack of quantitative indicators to characterize the functions and performance of the friction pendulum isolation bearing, and the quantitative assessment of the seismic safety performance of the friction pendulum isolation bearing and its bridge structure cannot be realized. Usually, ideal assumptions are adopted, that is, the change in the mechanical properties of the bearing is not considered or it is assumed that the change in the mechanical properties of the bearing reaches a certain level, and the mechanical performance analysis of the bridge structure is carried out, which brings great risks to the safety evaluation of the bridge structure and seismic safety.

[0005] According to the working principle, mechanical property calculation model and related research results of the friction pendulum isolation bearing, in addition to the geometric configuration, the key factor affecting the function and performance of this type of bearing is the friction characteristics of the sliding interface of the bearing. Under the combined action of long-term operating loads, wind, temperature and other factors, the state of the sliding interface and its friction characteristics of the friction pendulum isolation bearing can change, further affecting the lateral stiffness, energy dissipation capacity, damping characteristics, etc. of this type of bearing. Therefore, mastering the state of the sliding interface of the friction pendulum isolation bearing during a certain operation period and its specific friction characteristic parameters is one of the key indicators for accurately analyzing and evaluating the safety and seismic safety of bridge structures. Summary of the Invention

[0006] The present invention provides a method for evaluating the performance of a friction pendulum isolation bearing in a service state, which can obtain the state of the sliding interface of the friction pendulum isolation bearing in the service state and its specific friction characteristics, so as to evaluate the seismic performance of the friction pendulum isolation bearing.

[0007] In order to achieve these objects and other advantages of the present invention, there is provided a method for evaluating the performance of a friction pendulum isolation bearing in a service state, including:

[0008] S1. Detect the horizontal sliding displacement and vertical force of the friction pendulum isolation bearing in service;

[0009] S2. Calculate the friction coefficient μ of the sliding interface of the friction pendulum isolation bearing in service according to the detected data. The calculation process is as follows: μ0 = a1 + b1D (2); where μ0 is the initial friction coefficient, a2 and b2 are the influence coefficients of the horizontal loading displacement amplitude and compressive stress when measuring the friction coefficient respectively, N is the number of cycles of the horizontal sliding displacement between the maximum value and the minimum value, a1 and b1 are linear fitting coefficients, and D is the horizontal sliding displacement;

[0010] S3. Deduce the seismic performance indexes of the friction pendulum isolation bearing according to the friction coefficient μ of the sliding interface of the friction pendulum isolation bearing in service obtained. The seismic performance indexes include horizontal stiffness and effective damping ratio coefficient;

[0011] S4. Classify the safety risks of the friction pendulum isolation bearing with the sliding interface state according to the influence of the change of the sliding interface state and the change of the horizontal stiffness on the seismic damage state of the bridge structure.

[0012] Preferably, step S1 is specifically:

[0013] S101. Obtain the test data of the vertical force and horizontal sliding displacement of the friction pendulum isolation bearing for at least one day;

[0014] S102. Filter the test data to obtain the maximum vertical force, minimum vertical force, and average vertical force of the friction pendulum isolation bearing, so as to determine the compressive stress value of the friction pendulum isolation bearing.

[0015] S103. Extract the maximum and minimum values of the horizontal sliding displacement, and calculate the number of cycles of the horizontal sliding displacement between the maximum and minimum values during the detection time.

[0016] Preferably, before step S2, it further includes: using the model test and theoretical deduction methods to calculate the influence parameters of the interface friction characteristics of the friction pendulum isolation bearing, and obtaining the calculation formulas (1) and (2) of the sliding interface friction coefficient of the friction pendulum isolation bearing. The influence parameters include: the number of cycles of horizontal sliding displacement, horizontal sliding displacement, horizontal loading displacement amplitude, and compressive stress. Among them, when using the model test, the model of the friction pendulum isolation bearing used is the same as that of the in-service friction pendulum isolation bearing.

[0017] Preferably, in step S3, A. For the horizontal stiffness: under the influence of the sliding interface state, the calculation method of the horizontal stiffness of the friction pendulum isolation bearing is:

[0018] where K is the horizontal stiffness of the friction pendulum isolation bearing corresponding to the horizontal sliding displacement D when reaching the service time of t years, t≥0, W is the vertical force, μ is the friction coefficient considering the influence of the service time, α is the amplification coefficient of the horizontal stiffness of the friction pendulum isolation bearing, and the value range is 1.3 - 1.5;

[0019] If the horizontal stiffness of the friction pendulum isolation bearing is calculated according to the cumulative number of cycles of the sliding displacement, the calculation method is:

[0020] where K i is the horizontal equivalent stiffness of the friction pendulum isolation bearing at the i-th horizontal cumulative cycle number, K o is the horizontal equivalent stiffness of the friction pendulum isolation bearing at the first horizontal sliding displacement cycle number, a3 and b3 are respectively the horizontal loading displacement amplitude and compressive stress influence coefficient when measuring the horizontal stiffness, and N is the number of cycles of the horizontal sliding displacement;

[0021] B. For the effective damping ratio coefficient β eq , its calculation method is: β eq =A + BN (5), where A and B are respectively the horizontal loading displacement amplitude and compressive stress influence coefficient when measuring the effective damping ratio coefficient, and N is the number of cycles of the horizontal sliding displacement.

[0022] Preferably, it further includes S5. Based on the horizontal deformation of the friction pendulum isolation bearing as a quantitative characterization index, the post-earthquake damage state of the in-service friction pendulum isolation bearing is classified as follows:

[0023] S501. The displacement parameter of the friction pendulum isolation bearing based on which the classification is made: The horizontal sliding displacement D of the in-service friction pendulum isolation bearing, the value X of the displacement demand under normal operating load S , the design displacement X D , the ultimate displacement X L ;

[0024] S502. A. When D ≤ X S , and the horizontal sliding displacement can be reset, the post-earthquake damage state of the in-service friction pendulum isolation bearing is intact;

[0025] B. When D ≤ X S , and the sliding friction characteristics change within a short distance, the post-earthquake damage state of the in-service friction pendulum isolation bearing is slightly damaged;

[0026] C. When X S < D ≤ X D , and the interface sliding function deteriorates within a limited horizontal sliding distance and the horizontal sliding displacement cannot be fully restored, the post-earthquake damage state of the in-service friction pendulum isolation bearing is moderately damaged;

[0027] D. When X D < D ≤ X L , and the interface sliding function deteriorates; the horizontal sliding displacement is basically irrecoverable, the post-earthquake damage state of the in-service friction pendulum isolation bearing is severely damaged;

[0028] E. When D > X L , and the connecting parts of the in-service friction pendulum isolation bearing fail, the rubber extrudes, and the sliding function fails, the post-earthquake damage state of the in-service friction pendulum isolation bearing is extremely severely damaged.

[0029] Preferably, in step S4, the seismic safety risk of the friction pendulum isolation bearing with the sliding interface state is classified as follows: A. When the change amount of the friction coefficient Δμ of the sliding interface of the in-service friction pendulum isolation bearing ≤ 5%, and the change amount of the shear stiffness ΔK ≤ 10%, the safety risk level is I good;

[0030] B. When the change amount of the friction coefficient of the sliding interface of the in-service friction pendulum isolation bearing 5% < Δμ ≤ 10%, and the change amount of the shear stiffness 10% < ΔK ≤ 20%, the safety risk level is II slightly deteriorated;

[0031] C. When the change amount of the friction coefficient of the sliding interface of the in-service friction pendulum isolation bearing satisfies 10% < Δμ ≤ 40% and the change amount of the shear stiffness satisfies 20% < ΔK ≤ 40%, the safety risk level is III, indicating moderate deterioration;

[0032] D. When the change amount of the friction coefficient of the sliding interface of the in-service friction pendulum isolation bearing is Δμ > 40% and the change amount of the shear stiffness is ΔK > 40%, the safety risk level is IV, indicating severe deterioration;

[0033] E. When the change amount of the friction coefficient of the sliding interface of the in-service friction pendulum isolation bearing is Δμ > 40% and its seismic performance does not meet the verification requirements, the safety risk level is V, indicating extremely severe deterioration;

[0034] Among them, Δμ is the change amount of the friction coefficient of the sliding interface of the in-service friction pendulum isolation bearing compared with the initial sliding friction coefficient, and ΔK is the change amount of the horizontal stiffness of the in-service friction pendulum isolation bearing compared with the horizontal stiffness at the first horizontal sliding displacement cycle number.

[0035] Preferably, it further includes S6. Based on the lateral stiffness and displacement ductility of the pier column as quantitative characterization indexes, and combining the influence of its service performance deterioration on its seismic damage state, the seismic safety risk of the friction pendulum isolation bridge is classified.

[0036] The present invention has at least the following beneficial effects:

[0037] First, by detecting the horizontal sliding displacement and vertical force, the key parameters of the in-service friction pendulum isolation bearing can be obtained. It not only considers the directly measured parameters such as horizontal sliding displacement and vertical force, but also further calculates the key performance indexes such as the friction coefficient of the sliding interface, horizontal stiffness, and effective damping ratio coefficient through these parameters, reflecting the working state of the friction pendulum isolation bearing from multiple dimensions. Therefore, the performance of the friction pendulum isolation bearing can be comprehensively evaluated from multiple dimensions. Generally speaking, this evaluation method includes multiple steps such as basic data detection, friction coefficient calculation, seismic performance index calculation, and safety risk and damage state classification, comprehensively evaluating the performance of the friction pendulum isolation bearing and avoiding the one-sidedness of single-index evaluation.

[0038] Second, according to the influence of the change of the sliding interface state and the horizontal stiffness on the seismic damage state of the bridge structure, the safety risks of the friction pendulum isolation bearing are classified, and the safety risks existing in the friction pendulum isolation bearing can be detected in time. Once a situation with a relatively high risk level is found, corresponding maintenance or replacement measures can be taken in time to avoid the damage of the bridge structure caused by the poor performance of the bearing during natural disasters such as earthquakes, ensuring the safe use of the bridge. Taking the horizontal deformation of the friction pendulum isolation bearing as a quantitative characterization index, the post-earthquake damage state of the in-service friction pendulum isolation bearing is classified, making the evaluation result more intuitive and clear, and being able to clearly reflect the damage degree of the friction pendulum isolation bearing.

[0039] Other advantages, objectives and features of the present invention will be partially reflected by the following description, and partially will also be understood by those skilled in the art through the research and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a schematic flow chart of the performance evaluation method for the friction pendulum isolation bearing in the service state of the present invention;

[0041] Figure 2 It is a data graph of the relationship between the horizontal loading displacement amplitude and the horizontal force;

[0042] Figure 3 It is a data graph of the relationship between the friction coefficient of the friction pendulum isolation bearing and the horizontal loading displacement amplitude;

[0043] Figure 4 It is the seismic risk safety risk level classification standard for the friction pendulum isolation bearing;

[0044] Figure 5 It is the damage state classification standard for the friction pendulum isolation bearing;

[0045] Figure 6 It is the seismic risk safety risk level classification standard for the in-service bridge pier;

[0046] Figure 7 It is the pier column damage state classification standard;

[0047] Figure 8 It is the seismic risk safety risk level classification standard for the seismic measures;

[0048] Figure 9 It is the seismic risk safety risk level classification for the isolated and seismically isolated girder bridge;

[0049] Figure 10 It is a schematic diagram of the relationship between the vertical displacement and time at different measuring points in the laboratory test;

[0050] Figure 11Schematic diagram of the relationship between vertical displacement and vertical force in laboratory tests. Specific implementation mode

[0051] The present invention will be further described in detail below with reference to the accompanying drawings, so that those skilled in the art can implement it according to the description in the specification.

[0052] It should be understood that the terms such as "having", "including" and "comprising" used herein do not exclude the presence or addition of one or more other elements or their combinations.

[0053] It should be noted that the experimental methods described in the following embodiments are all conventional methods unless otherwise specified, and the reagents and materials can be obtained from commercial channels unless otherwise specified; in the description of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "installed", "connected", and "set" should be understood in a broad sense. For example, they can be fixedly connected and set, or detachably connected and set, or integrally connected and set. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. The orientation or positional relationship indicated by the terms "lateral", "longitudinal", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention.

[0054] As Figure 1 shown, the embodiment of the present invention provides a method for evaluating the performance of a friction pendulum isolation bearing under service conditions, including:

[0055] S1. Detect the horizontal sliding displacement and vertical force of the friction pendulum isolation bearing in service.

[0056] Among them, step S1 is specifically:

[0057] S101. Obtain the test data of the vertical force and horizontal sliding displacement of the friction pendulum isolation bearing for at least one day;

[0058] S102. Filter the test data to obtain the maximum vertical force, minimum vertical force and average vertical force of the friction pendulum isolation bearing, so as to determine the compressive stress value of the friction pendulum isolation bearing;

[0059] S103. Extract the maximum and minimum values of the horizontal sliding displacement, and calculate the number of cycles of the horizontal sliding displacement between the maximum and minimum values during the detection time.

[0060] In the above steps, the upper connecting plate of the friction pendulum isolation bearing is connected to the bridge or the superstructure, and the lower connecting plate is connected to the pier column. For the in-service friction pendulum isolation bearing, within the space range of the beam bottom and pier top on-site, a vertical force measuring device and a horizontal displacement testing device are installed. The horizontal displacement testing device can adopt a contact or non-contact laser displacement sensor. The vertical force measuring device can adopt a pressure sensor, which is set at the connecting part of the friction pendulum isolation bearing to measure the vertical load of the friction pendulum isolation bearing. Obtain the test data of the vertical force and horizontal sliding displacement of the friction pendulum isolation bearing for at least one day, and then perform filtering processing on the test data, so as to obtain the maximum vertical force, minimum vertical force and average vertical force of the friction pendulum isolation bearing. Divide the vertical force by the bearing area to obtain the compressive stress value, and thus the maximum compressive stress value, minimum compressive stress value and average compressive stress value can be calculated. Extract the maximum and minimum values of the horizontal sliding displacement from the filtered test data, and calculate the number of cycles of the horizontal sliding displacement between the maximum and minimum values during the monitoring time.

[0061] S2. According to the detected data, calculate the sliding interface friction coefficient μ of the in-service friction pendulum isolation bearing. The calculation process is as follows: μ0 = a1 + b1D (2); where μ0 is the initial friction coefficient, a2 and b2 are the horizontal loading displacement amplitude and compressive stress influence coefficient when measuring the friction coefficient respectively, N is the number of cycles of the horizontal sliding displacement between the maximum and minimum values, a1 and b1 are the linear fitting coefficients, and D is the horizontal sliding displacement.

[0062] Among them, before step S2, it also includes step S1-2: adopt the model test and theoretical deduction methods to calculate the influence parameters of the interface friction characteristics of the friction pendulum isolation bearing, and obtain the calculation formulas (1) and (2) of the sliding interface friction coefficient of the friction pendulum isolation bearing. When adopting the model test, the model of the friction pendulum isolation bearing used is the same as that of the in-service friction pendulum isolation bearing.

[0063] In the above steps, it is necessary to first calculate the influence parameters of the interface friction characteristics of the friction pendulum isolation bearing through the model test and theoretical deduction methods. As Figure 2 and Figure 3 shown, in Figure 2 , a relationship data graph between the horizontal loading displacement amplitude and the horizontal force is given. In Figure 3 , a relationship data graph between the friction coefficient of the friction pendulum isolation bearing and the horizontal loading displacement amplitude is given. It can be seen from Figure 3 that the friction coefficient of the friction pendulum isolation bearing is related to parameters such as the horizontal loading displacement amplitude and the number of cycles of the horizontal sliding displacement. By Figure 2 and Figure 3By processing the relational data diagram, the calculation formula for the relationship between the sliding interface friction coefficient of the friction pendulum bearing and the cumulative number of horizontal displacement cycles can be obtained:

[0064] μ0 is the initial friction coefficient, which varies with the horizontal loading displacement. b2 is the influence coefficient of the compressive stress when measuring the friction coefficient. The influence coefficient of the compressive stress is an index reflecting the change degree of various performance parameters of the friction pendulum isolation bearing under different compressive stress states. It reflects the influence of the vertical compressive stress on the horizontal mechanical properties of the bearing. With the change of the compressive stress, the relationship between the horizontal loading displacement amplitude and the horizontal force will also change. By analyzing the horizontal loading data under different compressive stresses, the specific value or variation law of the influence coefficient of the compressive stress can be determined.

[0065] In addition, for the friction pendulum isolation bearing, when the sliding block slides along the entire sliding curve, the sliding interface friction coefficient changes with the sliding displacement. However, in the current analysis of the mechanical properties of the friction pendulum isolation bearing, an ideal constant friction coefficient is usually adopted, which does not conform to the actual situation. Therefore, in order to accurately obtain the mechanical properties of the friction pendulum isolation bearing, the initial friction coefficient μ0 can be obtained through the friction test of the bearings of the same model: μ0 = a1 + b1D (2), where a1 and b1 are linear fitting coefficients, and D is the horizontal sliding displacement.

[0066] According to the horizontal sliding displacement test data of the in-service friction pendulum isolation bearing, first calculate the initial sliding friction coefficient of the friction pendulum isolation bearing within a certain range of horizontal sliding displacement through formula (2). Then, through the number of cycles of the horizontal sliding displacement within a certain test time, and then use formula (1) to calculate the sliding interface friction coefficient of the current friction pendulum isolation bearing.

[0067] S3. According to the obtained sliding interface friction coefficient μ of the in-service friction pendulum isolation bearing, deduce the seismic performance indexes of the friction pendulum isolation bearing, and the seismic performance indexes include horizontal stiffness and effective damping ratio coefficient.

[0068] Among them, in step S3, A. For the horizontal stiffness: Under the influence of the sliding interface state, the calculation method of the horizontal stiffness of the friction pendulum isolation bearing is:

[0069] Among them, K is the horizontal stiffness of the friction pendulum isolation bearing corresponding to the horizontal sliding displacement D when reaching the service time of t years, t ≥ 0. The number of horizontal displacement cycles N is the cumulative reciprocating cycle number of the horizontal displacement of the friction pendulum bearing measured during the service time of the bridge for t years. W is the vertical force, μ is the friction coefficient considering the influence of the service time, and α is the amplification coefficient of the horizontal stiffness of the friction pendulum isolation bearing, and the value range is 1.3 - 1.5;

[0070] If the horizontal stiffness of the friction pendulum isolation bearing is calculated based on the cumulative number of sliding displacement cycles, the calculation method is as follows:

[0071] Wherein, K i is the horizontal equivalent stiffness of the friction pendulum isolation bearing at the i-th horizontal cumulative cycle number, and K o is the horizontal equivalent stiffness of the friction pendulum isolation bearing at the first horizontal sliding displacement cycle number. Specifically, it is the value corresponding to 20% of the design displacement for the horizontal sliding displacement. a3 and b3 are respectively the horizontal loading displacement amplitude and the compressive stress influence coefficient when measuring the horizontal stiffness, which can be determined according to the test data. N is the number of horizontal sliding displacement cycles;

[0072] B. For the effective damping ratio coefficient β eq , its calculation method is: β eq = A + BN (5), where A and B are respectively the horizontal loading displacement amplitude and the compressive stress influence coefficient when measuring the effective damping ratio coefficient, and N is the number of horizontal sliding displacement cycles. The equivalent damping ratio coefficient develops linearly with the increase of the cumulative number of horizontal sliding displacement cycles.

[0073] S4. According to the influence of the change of the sliding interface state and the change of the horizontal stiffness on the seismic damage state of the bridge structure, the seismic safety risk of the friction pendulum isolation bearing with the sliding interface state is classified.

[0074] Among them, in step S4, the safety risk of the friction pendulum isolation bearing with the sliding interface state is classified as follows: A. When the change amount of the sliding interface friction coefficient Δμ of the in-service friction pendulum isolation bearing ≤ 5%, and the change amount of the shear stiffness ΔK ≤ 10%, the safety risk level is I good;

[0075] B. When the change amount of the sliding interface friction coefficient 5% < Δμ ≤ 10% and the change amount of the shear stiffness 10% < ΔK ≤ 20% of the in-service friction pendulum isolation bearing, the safety risk level is II slightly deteriorated;

[0076] C. When the change amount of the sliding interface friction coefficient 10% < Δμ ≤ 40% and the change amount of the shear stiffness 20% < ΔK ≤ 40% of the in-service friction pendulum isolation bearing, the safety risk level is III moderately deteriorated;

[0077] D. When the change amount of the sliding interface friction coefficient Δμ > 40% and the change amount of the shear stiffness ΔK > 40% of the in-service friction pendulum isolation bearing, the safety risk level is IV severely deteriorated;

[0078] E. When the change amount Δμ of the friction coefficient of the sliding interface of the in-service friction pendulum isolation bearing is > 40% and the seismic performance does not meet the verification requirements, the safety risk level is extremely seriously deteriorated at level V;

[0079] Among them, Δμ is the change amount of the friction coefficient of the sliding interface of the in-service friction pendulum isolation bearing and the initial sliding friction coefficient, and ΔK is the change amount of the horizontal stiffness of the in-service friction pendulum isolation bearing and the horizontal stiffness under the number of cycles of the first horizontal sliding displacement.

[0080] In the above steps, the safety risk of the friction pendulum isolation bearing with the state of the sliding interface is mainly classified. For more detailed classification content, please refer to Figure 4 . In Figure 4 , based on the variation law of the friction coefficient of the sliding interface and the cumulative movement distance or the number of cycles, that is, considering the influence of the reciprocating sliding of the friction pendulum isolation bearing under normal operating conditions on the interface state and its further influence on the seismic performance of the bearing, the seismic safety risk classification standard of the friction energy dissipation type seismic bearing is formulated.

[0081] It should be noted that in the E level of the safety risk classification, the verification requirements are in accordance with the performance requirements of bridge isolation and seismic design in Section 10.4 of the current "Code for Seismic Design of Highway Bridges" (JTG / T 2231-01-2020), that is, under the action of E2 earthquake, local slight damage may occur to the piers, abutments and foundations, but they are still in the elastic state and do not need to be repaired after the earthquake or can continue to be used after simple repair; after combining the E2 earthquake action effects and permanent effects in the longitudinal and transverse directions of the bridge, the strength of the piers, abutments and foundations should be checked in accordance with the relevant provisions of the current highway bridge and culvert design code; and the isolation and seismic devices should be checked in accordance with 10.4.3. Because, after the friction coefficient of the sliding interface of the friction pendulum bearing increases, the lateral stiffness and recoverable force of the bearing will be affected; in addition, the horizontal force transmitted to the pier column will change, and it may not meet the strength performance requirements of the pier. The existing research conclusions show that when the friction coefficient of the sliding interface of the friction pendulum bearing increases by 40%, the horizontal stiffness of the friction pendulum bearing increases, the force on the lower pier column increases, the damage of the pier column increases, and the damage risk of not meeting the performance requirements increases.

[0082] S5. Based on the horizontal deformation of the friction pendulum isolation bearing as a quantitative characterization index, the damage state of the in-service friction pendulum isolation bearing is classified, specifically as follows:

[0083] S501. The displacement parameters of the friction pendulum isolation bearing based on which the classification is made: the horizontal sliding displacement D of the in-service friction pendulum isolation bearing, the value X of the displacement demand under normal operating load S , the design displacement X D , the ultimate displacement X L ;

[0084] S502, A. When D ≤ X S and the horizontal sliding displacement is resetable, the post - earthquake damage state of the service friction pendulum isolation bearing is intact;

[0085] B. When D ≤ X S and the sliding friction characteristics change within a short distance, the post - earthquake damage state of the service friction pendulum isolation bearing is slightly damaged;

[0086] C. When X S < D ≤ X D and the interface sliding function deteriorates within a limited horizontal sliding distance and the horizontal sliding displacement cannot be fully restored, the post - earthquake damage state of the service friction pendulum isolation bearing is moderately damaged;

[0087] D. When X D < D ≤ X L and the interface sliding function deteriorates; the horizontal sliding displacement is basically irrecoverable, the post - earthquake damage state of the service friction pendulum isolation bearing is severely damaged;

[0088] E. When D > X L and the connecting parts of the service friction pendulum isolation bearing fail, the rubber extrudes, and the sliding function fails, the post - earthquake damage state of the service friction pendulum isolation bearing is extremely severely damaged.

[0089] In the above steps, it is mainly aimed at classifying the post - earthquake damage state of the service friction pendulum isolation bearing according to the horizontal deformation of the friction pendulum isolation bearing as a quantitative characterization index. For more detailed classification content, please refer to Figure 5 . In Figure 5 , according to the whole - process force - deformation evolution process of the friction pendulum isolation bearing under the action of horizontal seismic load, based on the seismic vulnerability analysis and damage - deformation control objectives of this type of bearing for seismic isolation and vibration reduction bridges, with the horizontal deformation of the friction pendulum isolation bearing as a quantitative characterization index, considering the friction - slip energy - dissipation function and mechanical property change laws of the friction pendulum isolation bearing, and the influence on seismic damage and traffic function, starting from the values of displacement requirements (X S ), design displacement (X D ), ultimate displacement (X L ) and other states under normal operation load, a quantitative classification evaluation standard for the damage state of the service friction pendulum isolation bearing is formulated.

[0090] S6. Classify the seismic safety risk of the friction pendulum isolation bearing bridge according to the pier column lateral stiffness and displacement ductility as quantitative characterization indicators, combined with the influence of its service performance degradation on its seismic damage state.

[0091] In Figure 6In this study, based on the research results of the seismic performance of piers with durability degradation and the test results of the seismic performance of structurally flexurally cracked damaged piers carried out in this invention, and considering the vulnerability analysis results of piers under different flexural stiffnesses, taking the lateral stiffness and displacement ductility of piers as quantitative characterization indicators, and considering the influence law of their service performance degradation on their seismic damage states, a classification standard for the seismic safety risk levels of service piers was formulated. For existing single damage models, cumulative damage models, and comprehensive damage models, the contribution of displacement or deformation to the damage degree is relatively large, the combined coefficient of cumulative energy dissipation is very small, and the discreteness is relatively large, so it is generally ignored. The estimation of medium damage degree and the damage level classification standard of the above damage models are basically the same as the test phenomena, and are applicable to the damage discrimination of the lower piers of seismic isolation and energy dissipation girder bridges. Based on the theoretical calculation of the damage index of existing flexural ductile piers, combined with the classification standard of pier damage and performance level based on the residual drift ratio, a classification standard for the seismic damage state of flexural ductile piers was formed, as shown in Figure 7 As shown. Considering the influence of various seismic measures on the seismic damage mode of bridges or the risk probability of increasing the seismic damage degree, etc., a seismic safety risk level evaluation standard was formulated, as shown in Figure 8 As shown.

[0092] According to the vulnerable components of the seismic isolation and energy dissipation girder bridge under horizontal seismic loads, considering the key role of each vulnerable component in the typical damage failure mode and the correlation between components, as well as the influence law of each service state factor on the damage failure probability of vulnerable components and systems, a classification standard for the seismic safety risk levels of highway bridges was formulated as shown in Figure 9 As shown, and its classification criteria are as follows:

[0093] (1) Based on the seismic safety risk level of key and vulnerable seismic isolation and energy dissipation devices, the seismic safety risk level of the system structure changes accordingly;

[0094] (2) When the service state degradation of seismic isolation and energy dissipation devices, piers, and seismic measures occurs simultaneously, according to the influence of each part on the seismic damage state of the structure (without considering the interaction between components), the seismic safety risk level of the corresponding combination is given under the seismic safety risk benchmark level of the corresponding structural system;

[0095] (3) Considering the correlation of seismic isolation and energy dissipation devices, piers, and seismic measures under earthquake action and their influence on the seismic damage state of the structure, a more reasonable combined seismic safety risk level is further determined.

[0096] (4) When the service state degradation of seismic isolation and energy dissipation devices, piers, and seismic measures occurs simultaneously, when the seismic safety risk level of the seismic isolation and energy dissipation device is less than the seismic safety risk level of other components, the seismic safety risk level of the structure system takes the higher level.

[0097] In summary, the present invention can solve the problems of lack of detection and evaluation methods and indicators for the service conditions of friction pendulum isolation bearings, and lack of seismic safety evaluation and grading quantification standards for friction pendulum isolation bearings and their bridge structures, providing support for timely and accurately grasping the seismic safety risks and disposal timing, strategies, etc. of friction pendulum isolation bearings and their bridge structures.

[0098] In addition, it should be noted that for in-service bridges, when testing the service state indicators of friction pendulum isolation bearings, in order to reduce the on-site construction workload, time and economic costs, and reflect the advantages of the test technology such as feasibility, convenience, and reliability, the following key points need to be understood and mastered in advance before installing the test system on-site:

[0099] 1) Basic information such as the model, design parameters, and displacement sliding direction of the friction pendulum isolation bearing, providing a basis for further formulating the mechanical deformation performance indicators and test schemes of the friction pendulum isolation bearing;

[0100] 2) The spatial dimensions of the installation position of the friction pendulum isolation bearing, such as the width and thickness of the cushion layer of the friction pendulum isolation bearing, and whether there is a pre-embedded steel plate, etc., providing a reference for further formulating the test instrument installation scheme;

[0101] 3) The power supply and network conditions in the bridge site area, providing a reference for further forming corresponding systems such as test instruments, acquisition instruments, and data transmission.

[0102] For in-service bridges, since the load of the superstructure has been applied to the friction pendulum isolation bearing before testing, the theoretical vertical force of the friction pendulum isolation bearing at different positions can be obtained through calculation. Further, test instruments are arranged on the symmetric sides of the friction pendulum isolation bearing to test the change amount of the mechanical performance of the friction pendulum isolation bearing under the action of loads such as vehicles, temperature, and wind. By observing the change trend of the data of a single test instrument and the relative change trend of the symmetric test index in the long term, the state and performance change of the friction pendulum isolation bearing are judged, and it is further applied to the analysis of the change law of the seismic performance of the friction pendulum isolation bearing and the bridge with the service state and operation time. Therefore, on the basis of mastering the basic design parameters and performance parameters of the friction pendulum isolation bearing, the sampling frequency and accuracy of the adopted test instruments are tested and calibrated to determine the reliability of the test data.

[0103] Purchase a friction pendulum isolation bearing with the same type and model as that used in the actual project. According to the vertical force and vertical displacement indexes to be tested, design and conduct the laboratory test of the vertical force and vertical displacement of the friction pendulum isolation bearing, obtain the relationship curve between the tested vertical displacement and the vertical force, and obtain the change amount of the vertical force represented by the change amount of the vertical displacement, as well as the difference in the stress state of the friction pendulum isolation bearing corresponding to the symmetric displacement change amount. Then, reverse deduce the absolute vertical force and vertical displacement values of the current friction pendulum isolation bearing, and judge the service state of the friction pendulum isolation bearing, such as slip, uneven stress, etc. As Figure 10 and Figure 11 shown, in Figure 10 , the vertical displacement deviation of local voiding exists between the symmetric No. 1 measuring point and No. 3 measuring point. In Figure 11 , by using different test instruments, the vertical force-vertical displacement curve of the friction pendulum isolation bearing can be obtained, and the relationship between the change amount of the vertical displacement and the change amount of the vertical force can be obtained.

[0104] According to the pseudo-static test of the friction pendulum isolation bearing, the friction coefficient of the friction pendulum isolation bearing can be fitted, such as the friction pendulum isolation bearing model FPB3000-ZX-e150-0, with a compressive stress of 6 Mpa.

[0105] First, obtain the initial friction coefficient of the friction pendulum isolation bearing under a compressive stress of 6 Mpa through the pseudo-static test results, which is about 0.02. Then, during the cumulative cyclic horizontal loading displacement, when the horizontal loading displacement reaches 30 mm, the fitted change curve of the friction coefficient is the formula μ = μ0 + 0.0048e 0.005N . According to this method, the friction coefficients of the sliding interfaces under different loading displacements can be obtained. When N = 100 cycles are reached, the friction coefficient of the sliding interface of the friction pendulum isolation bearing is equal to 0.027. After determining the friction coefficient (0.027) of the sliding interface corresponding to a certain horizontal sliding displacement D (such as 30 mm), after calculating the change value of the vertical force (2652 kN) in a day and substituting it into formula (3), the stiffness of the friction pendulum isolation bearing corresponding to the horizontal sliding displacement (300 mm) can be calculated as 334 kN / m. Then, according to the 35% change in the friction coefficient of the sliding interface and the 35.0% change in the shear stiffness, the safety risk level can be determined as III medium deterioration. At this time, the state corresponding to the friction pendulum isolation bearing is that the characteristics of the service friction pendulum isolation bearing change, and there will be slight damage in the post-earthquake damage state.

[0106] According to the variation law of the effective damping ratio coefficient with the number of cycles β eq = 0.39 + 5.27×10 -4When N cycles 100 times, the effective damping ratio coefficient of the friction pendulum isolation bearing is further calculated to be 0.45. Finally, the calculated stiffness and effective damping ratio coefficient of the friction pendulum isolation bearing are input into the mechanical constitutive relationship of the friction pendulum isolation bearing in the finite element numerical model to analyze the seismic performance of the entire bridge under the influence of the in-service friction pendulum isolation bearing.

[0107] The equipment quantities and processing scales described herein are used to simplify the description of the present invention. Applications, modifications, and variations of the present invention will be apparent to those skilled in the art.

[0108] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily made. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to specific details and the illustrated and described examples herein.

Claims

1. A method for evaluating the performance of a friction pendulum type seismic isolation bearing in service, characterized in that: include: S1. Detect the horizontal sliding displacement and vertical force of the friction pendulum type seismic isolation bearing in service; S2. According to the test data, the sliding interface friction coefficient μ of the friction pendulum type seismic isolation bearing in service is calculated. The calculation process is: μ0=a1+b1D(2); Among them, μ0 is the initial friction coefficient, a2 and b2 are the horizontal loading displacement amplitude and compressive stress influence coefficient when measuring the friction coefficient, N is the number of cycles between the maximum and minimum values ​​of the horizontal sliding displacement, a1 and b1 are linear fitting coefficients, and D is the horizontal sliding displacement; S3, according to the obtained sliding interface friction coefficient μ of the friction pendulum type seismic isolation bearing in service, the seismic performance index of the friction pendulum type seismic isolation bearing is calculated, wherein the seismic performance index includes horizontal stiffness and effective damping ratio coefficient; S4. Based on the impact of changes in the sliding interface state and horizontal stiffness on the seismic damage state of the bridge structure, the seismic safety risk of the friction pendulum type seismic isolation bearing in the sliding interface state is graded.

2. The performance evaluation method of the friction pendulum type seismic isolation bearing in service state as claimed in claim 1 is characterized in that: Step S1 is specifically as follows: S101. Obtain at least one day's worth of test data on the vertical force and horizontal sliding displacement of the friction pendulum type seismic isolation bearing; S102, filtering the test data to obtain the maximum vertical force, the minimum vertical force and the average vertical force of the friction pendulum type seismic isolation bearing, so as to determine the compressive stress value of the friction pendulum type seismic isolation bearing; S103, extracting the maximum and minimum values ​​of the horizontal sliding displacement, and calculating the number of cycles of the horizontal sliding displacement between the maximum and minimum values ​​within the detection time.

3. The performance evaluation method of the friction pendulum type seismic isolation bearing in service state as claimed in claim 1 is characterized in that: Before step S2, the method also includes: using model tests and theoretical deduction methods to calculate the influencing parameters of the interface friction characteristics of the friction pendulum type seismic isolation bearing, and obtaining the calculation formula (1) and formula (2) of the sliding interface friction coefficient of the friction pendulum type seismic isolation bearing, wherein the influencing parameters include: the number of horizontal sliding displacement cycles, the horizontal sliding displacement, the horizontal loading displacement amplitude and the compressive stress; wherein, when using the model test, the model of the friction pendulum type seismic isolation bearing used is the same as the model of the friction pendulum type seismic isolation bearing in service.

4. The performance evaluation method of the friction pendulum type seismic isolation bearing in service state as claimed in claim 1 is characterized in that: In step S3, A. for horizontal stiffness: under the influence of the sliding interface state, the horizontal stiffness of the friction pendulum type seismic isolation bearing is calculated as follows: Wherein, K is the horizontal stiffness of the friction pendulum type seismic isolation bearing corresponding to the horizontal sliding displacement D when the service time reaches t years, t≥0, W is the vertical force, μ is the friction coefficient considering the influence of service time, α is the horizontal stiffness magnification factor of the friction pendulum type seismic isolation bearing, and the value range is 1.3~1.5; If the horizontal stiffness of the friction pendulum type seismic isolation bearing is calculated based on the cumulative number of sliding displacement cycles, the calculation method is: Among them, K i is the horizontal equivalent stiffness of the friction pendulum type seismic isolation bearing under the i-th horizontal cumulative number of cycles, K o is the horizontal equivalent stiffness of the friction pendulum type seismic isolation bearing under the first horizontal sliding displacement cycle number, a3 and b3 are the horizontal loading displacement amplitude and compressive stress influence coefficient when measuring horizontal stiffness, and N is the horizontal sliding displacement cycle number; B. For the effective damping ratio coefficient β eq , which is calculated as: β eq =A+BN(5), A and B are the horizontal loading displacement amplitude and compressive stress influence coefficient when measuring the effective damping ratio coefficient, respectively, and N is the number of horizontal sliding displacement cycles.

5. The performance evaluation method of the friction pendulum type seismic isolation bearing in service state as claimed in claim 1 is characterized in that: It also includes S5, based on the horizontal deformation of the friction pendulum type seismic isolation bearing as a quantitative characterization index, the post-earthquake damage state of the friction pendulum type seismic isolation bearing in service is classified into: S501. Displacement parameters of the friction pendulum type seismic isolation bearing used for classification: horizontal sliding displacement D of the friction pendulum type seismic isolation bearing in service, the displacement demand value X under normal operating load S , design displacement X D , limit displacement X L ; S502, A, when D≤X S If the horizontal sliding displacement can be reset, the post-earthquake damage state of the in-service friction pendulum type seismic isolation bearing is intact; B. When D≤X S When the sliding friction characteristics change within a short distance, the post-earthquake damage state of the friction pendulum type seismic isolation bearing in service is slightly damaged; C. When X S <D≤X D When the interface sliding function deteriorates within the limited horizontal sliding distance and the horizontal sliding displacement cannot be fully restored, the post-earthquake damage state of the in-service friction pendulum type seismic isolation bearing is medium damage; D. When X D <D≤X L When the interface sliding function is degraded and the horizontal sliding displacement is basically irreversible, the post-earthquake damage state of the in-service friction pendulum type seismic isolation bearing is seriously damaged; E. When D>X L If the connecting parts of the friction pendulum type seismic isolation bearing in service fail, the rubber is extruded, and the sliding function fails, the post-earthquake damage state of the friction pendulum type seismic isolation bearing in service will be extremely serious.

6. The performance evaluation method of the friction pendulum type seismic isolation bearing in service state as claimed in claim 1 is characterized in that: In step S4, the seismic safety risk of the friction pendulum type seismic isolation bearing in the sliding interface state is classified into levels, specifically: A. When the change in the sliding interface friction coefficient of the service friction pendulum type seismic isolation bearing is Δμ≤5% and the change in the shear stiffness is ΔK≤10%, the safety risk level is I good; B. When the sliding interface friction coefficient of the in-service friction pendulum type seismic isolation bearing changes by 5%<Δμ≤10%, and the shear stiffness changes by 10%<ΔK≤20%, the safety risk level is II slightly deteriorated; C. When the change in the sliding interface friction coefficient of the in-service friction pendulum type seismic isolation bearing is 10% < Δμ ≤ 40%, and the change in the shear stiffness is 20% < ΔK ≤ 40%, the safety risk level is III moderate degradation; D. When the change in the friction coefficient of the sliding interface of the friction pendulum type seismic isolation bearing in service Δμ>40% and the change in the shear stiffness ΔK>40%, the safety risk level is IV severe degradation; E. When the change in the friction coefficient of the sliding interface of the friction pendulum type seismic isolation bearing in service Δμ>40% and the seismic performance does not meet the verification requirements, the safety risk level is V, which is extremely severely degraded; Among them, Δμ is the change of the sliding interface friction coefficient of the friction pendulum type seismic isolation bearing in service and the initial sliding friction coefficient, and ΔK is the change of the horizontal stiffness of the friction pendulum type seismic isolation bearing in service and the horizontal stiffness under the first horizontal sliding displacement cycle number.

7. The performance evaluation method of the friction pendulum type seismic isolation bearing in service state as claimed in claim 1 is characterized in that: It also includes S6, which classifies the seismic safety risks of friction pendulum-type seismic isolation bridges based on the lateral stiffness and displacement ductility of the piers as quantitative characterization indicators and the influence of their service performance degradation on their seismic damage status.

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