Main aftershock sequence construction method and water intake tower damage assessment method

Abstract

This application provides a method for constructing a mainshock and aftershock sequence and a method for assessing damage to an intake tower. The method includes: obtaining an unfavorable mainshock and aftershock sequence based on ground motion data, and a database of near-field measured mainshocks, near-field measured aftershocks, far-field measured mainshocks, and far-field measured aftershocks; constructing multiple input conditions using the data from the databases and performing unified amplitude modulation processing to obtain the target mainshock and target aftershocks; determining the mainshock spectrum value of the target mainshock and the aftershock spectrum value of the target aftershock; determining the sum of squared residuals (SSE) between the mainshock spectrum value and the aftershock spectrum value, and a scaling factor. k ; Combine the sum of squared residuals (SSE) with the scaling factor k The mainshock spectrum and aftershock spectrum values ​​with a difference less than a preset difference threshold are used as matching results, thereby constructing a mainshock and aftershock combination with good spectral consistency; this application uses an improved spectrum matching method to construct a mainshock and aftershock combination with good comparability.

Description

Technical Field

[0001] This application relates to the field of earthquake resistance and safety assessment technology, and in particular to a method for constructing a mainshock and aftershock sequence and a method for assessing damage to water intake towers. Background Technology

[0002] Intake towers are crucial structures in hydropower projects, enabling pressurized water intake and regulating water flow. They play a vital role in ensuring the safe operation of hydropower stations and supporting downstream water supply and irrigation. Driven by abundant hydropower resources, tall concrete hydraulic structures such as intake towers are widely deployed in Southwest China. However, this region is located at the intersection of multiple active fault zones, experiencing frequent and intense earthquakes. Due to their large height-to-width ratio and significant dynamic coupling, intake tower structures are prone to amplified response, performance degradation, and localized damage under seismic loads, threatening the safety of the entire hydropower system. However, current seismic design codes for intake towers are mostly based on single earthquake events, neglecting the cumulative effects of aftershocks and potentially underestimating the actual structural risks. Therefore, intake towers should not only be able to withstand the main shock but also possess sufficient safety reserves to cope with the cumulative structural damage and performance degradation under the combined effects of the main shock and aftershocks.

[0003] Existing research on the effects of far-field and near-field ground motions mainly employs single-type ground motion inputs or comparative analyses of structural responses under both types of ground motions to reveal their differing influence on structural response characteristics. However, the impact of mainshock sequences containing both near-field and far-field ground motion characteristics on the seismic performance of structures needs further clarification.

[0004] In summary, although there has been some research on the dynamic response and damage evolution of hydraulic structures under seismic action, the following shortcomings still exist: (1) Most existing studies assume a single earthquake event and do not adequately consider the cumulative damage and performance degradation caused by common aftershock sequences after the main shock; (2) In existing related studies, the earthquake input usually adopts a single type of ground motion, or simply compares near-field and far-field ground motions, lacking a systematic consideration of the comprehensive impact of near-field and far-field ground motions in the main shock-aftershock sequence under a unified analytical framework; (3) At the engineering performance level, there is still a lack of systematic and quantitative assessment of the differences in the impact of various near-field and far-field aftershock combinations on the damage evolution and performance degradation of intake towers, as well as the identification of the most unfavorable situation. Summary of the Invention

[0005] This application provides a method for constructing a mainshock and aftershock sequence and a method for assessing the damage of intake towers. It solves the problems in the prior art that it does not adequately consider the cumulative damage and performance degradation caused by common aftershock sequences after the mainshock, and lacks a systematic and quantitative assessment of the differences in the impact of various near-field and far-field aftershock combinations on the damage evolution and performance degradation of intake towers. It constructs a mainshock and aftershock combination working condition with good comparability and realizes a quantitative assessment of the damage to the intake tower.

[0006] To achieve the above objectives, the technical solution of this application embodiment is as follows:

[0007] In a first aspect, embodiments of this application provide a method for constructing a mainshock-aftershock sequence, the method comprising:

[0008] Seismic motion data are obtained from an earthquake database, and unfavorable mainshock and aftershock sequences are selected from the seismic motion data based on the dominant period.

[0009] Based on the aforementioned seismic data, the interlayer distance is interrupted. For sequences smaller than a preset distance range, a near-field measured mainshock database and a near-field measured aftershock database are constructed; based on the interruption layer distance of the ground motion data... For sequences exceeding a preset distance range, construct a far-field measured mainshock database and a far-field measured aftershock database;

[0010] Based on the data from the near-field measured mainshock database, near-field measured aftershock database, far-field measured mainshock database, and far-field measured aftershock database, multiple input conditions are constructed and uniform amplitude modulation processing is performed; the input conditions are near-field mainshock and near-field aftershock, far-field mainshock and far-field aftershock, near-field mainshock and far-field aftershock, or far-field mainshock and near-field aftershock.

[0011] For each main shock and its corresponding aftershock in the input working condition, amplitude modulation is performed according to the intensity ratio coefficient corresponding to the main shock to obtain the target main shock and target aftershock.

[0012] Determine the acceleration response spectrum of the target mainshock within the range of 0–6s, and obtain the spectral values ​​L1, L2, L3, …, L 150 and average value The main shock spectrum value was obtained by normalizing the data; and the acceleration response spectrum of the aftershock acceleration in the range of 0–6 s was determined, and the spectrum value was obtained. , , ... and average value The aftershock spectrum values ​​were obtained by normalization.

[0013] The sum of squared residuals SSE between the mainshock spectrum value and the aftershock spectrum value is determined by a first preset formula, and the scaling factor k between the mainshock spectrum value and the aftershock spectrum value is determined by a second preset formula.

[0014] The mainshock spectrum and aftershock spectrum values ​​with a difference of less than a preset difference threshold between the residual sum of squares (SSE) and the scaling factor (k) are used as the matching results to construct a mainshock and aftershock combination with good spectral consistency.

[0015] In one possible implementation, the ground motion data is data in the earthquake database that meets preset conditions; the preset conditions are that the magnitude of the main shock and aftershocks are not less than 5.0, the horizontal peak ground acceleration (PGA) is greater than or equal to 0.04g, the mean shear wave velocity is greater than 250m / s, the main shock and aftershock records are taken from the same station recording the same directional component of the same earthquake event, and the selected station has corresponding fault distance data.

[0016] The unfavorable mainshock and aftershock sequence is the dominant period T of the aftershock sequence. A The dominant period T of the main shock sequence is greater than or equal to M sequence.

[0017] In one possible implementation, the unified amplitude modulation process involves uniformly adjusting the peak ground acceleration (PGA) of the main shock and aftershocks in the input working condition to the actual peak ground acceleration of the earthquake at the engineering site; the acceleration response spectrum consists of 150 spectral values ​​determined at 0.04s intervals within the range of 0 to 6s.

[0018] In one possible implementation, the first preset formula is:

[0019] The second preset formula is: .

[0020] Secondly, embodiments of this application provide a method for assessing damage to a water intake tower, the method comprising:

[0021] A three-dimensional numerical model of the water intake tower body is constructed. The unfavorable main shock and aftershock sequence constructed by the main shock and aftershock sequence construction method is used as the input working condition. The displacement parameters and damage index parameters of the three-dimensional numerical model under the action of the main shock and the action of the main shock and aftershock are determined in the unfavorable main shock and aftershock sequence.

[0022] When the displacement parameters cannot reflect the damage increment caused by aftershocks, the damage increment of the three-dimensional numerical model is determined based on the damage index parameters, combined with the third and fourth preset formulas. and incremental damage index This leads to the determination of damage parameters characterizing the increase in aftershock damage; the damage parameters are the local damage index at the interface between the tower body and the lower backfill.

[0023] Using the main shock and aftershock combination and main shock constructed by the main shock and aftershock sequence construction method as input conditions, the damage parameters and overall tower damage index of the three-dimensional numerical model under the action of the main shock and aftershock combination and under the action of the main shock are determined respectively.

[0024] Based on the damage parameters and the overall tower damage index, the ability of the three-dimensional numerical model to reflect aftershock damage is evaluated.

[0025] In one possible implementation, the three-dimensional numerical model is constructed based on ABAQUS, and the foundation within the range of 2 times the tower height on the upstream and downstream sides, left and right sides, and 1.5 times the tower height at the bottom of the tower is taken as the generation object; the displacement parameters are the maximum displacement of the tower top in the direction along the river, across the river, and vertically; the damage index parameters are the local damage index at the interface between the tower body and the upper and lower backfills and the overall damage index of the tower body.

[0026] In one possible implementation, determining the displacement-type parameters and damage index-type parameters of the three-dimensional numerical model under the action of the mainshock and the action of the mainshock and aftershock in the unfavorable mainshock and aftershock sequence includes:

[0027] In the unfavorable mainshock and aftershock sequence, the displacement parameters of the three-dimensional numerical model response are obtained under the action of the mainshock and the action of the mainshock and aftershock.

[0028] The local damage index in the damage index class parameters is determined by the fifth preset formula, and the overall damage index in the damage index class parameters is determined by the sixth preset formula.

[0029] The fifth preset formula is: ;in, Damage area at a certain elevation The local damage index; Damaged area The Middle Damage indicators for each unit; For the region The Middle The area of ​​each unit; For a certain elevation damage area Weighting coefficients; Damage area The influence coefficient of the crack initiation location is taken as 1.0 on the water-facing side and 0.8 in other cases; Damage area The crack embedding degree influence coefficient is the ratio of crack length to the path length.

[0030] The sixth preset formula is: ;in, The overall damage index of the structure; This represents the local damage index of the component. The weighting coefficient of the component; Components under seismic loading Energy consumption; This represents the total energy consumption of the structure.

[0031] In one possible implementation, the displacement parameters cannot reflect the damage increment caused by aftershocks as follows: when the difference between the first displacement parameter value under the action of the main shock in the unfavorable main shock and aftershock sequence and the second displacement parameter value under the action of the main shock and aftershock in the unfavorable main shock and aftershock sequence is less than a preset difference threshold, it is determined that the first displacement parameter value and the second displacement parameter value are close, so that the displacement parameters cannot effectively reflect the damage increment caused by aftershocks.

[0032] The third preset formula is: ;in, For the increase in damage, Structural damage under the action of main shock and aftershock Structural damage under the action of the main shock; the fourth preset formula is: ;in, This is the incremental damage index.

[0033] In one possible implementation, the damage increment of the three-dimensional numerical model is determined based on the damage index class parameters, combined with a third preset formula and a fourth preset formula. and incremental damage index This leads to the determination of damage parameters characterizing the increase in aftershock damage, including:

[0034] Local damage increment at the interface between the tower body and the lower backfill in the three-dimensional numerical model The average value is greater than the overall damage increment of the tower body. Mean and local damage increment at the interface between the tower body and the upper backfill The mean, and the incremental damage index of local damage at the interface between the tower body and the lower backfill. The mean is greater than the incremental damage index of the overall tower damage. Mean and incremental damage index of local damage at the interface between the tower body and the upper backfill Under the mean, it is determined that the plastic deformation and damage accumulation are greater at the interface between the tower body and the lower backfill, and the local damage is more sensitive to the impact of aftershocks. Therefore, the local damage index at the interface between the tower body and the lower backfill is used as a damage parameter to characterize the increase in aftershock damage.

[0035] In one possible implementation, evaluating the ability of the three-dimensional numerical model to reflect aftershock damage based on the damage parameters and the overall tower damage index includes:

[0036] Under the combined effect of main shocks and aftershocks, all of which are near-field, the greatest damage is caused to the area at the interface between the tower body and the lower backfill and the tower body as a whole in the three-dimensional numerical model, with an overall damage index of 0.5 and a local damage index of 0.4.

[0037] Under the combined action of the main shock and aftershocks, which are all in the far field, the damage to the area at the interface between the tower body and the lower backfill and the tower body as a whole in the three-dimensional numerical model is minimal, with an overall damage index of 0.26 and a local damage index of 0.13.

[0038] The damage to the area at the interface between the tower body and the lower backfill and the tower body as a whole caused by the combined action of near-field main shock and far-field aftershock, or the combined action of far-field main shock and near-field aftershock, falls between the damage caused by the combination of near-field main shock and aftershock and the damage caused by the combination of far-field main shock and aftershock.

[0039] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages:

[0040] (1) Based on the selected real mainshock and aftershock ground motion records, the spectrum matching method is improved by combining unified amplitude modulation processing and normalized response spectrum, which effectively eliminates the influence of ground motion intensity differences on spectrum comparison and realizes the spectrum similarity control of the mainshock and aftershock combination; the residual sum of squares (SSE) between normalized response spectra is used as the matching index, and the aftershock record that is closest to the target mainshock spectrum is selected, so that the constructed mainshock and aftershock combination has the consistency of spectrum characteristics and conforms to the physical laws of real earthquake records.

[0041] (2) Through comparative analysis of the damage index of the backfill and the overall damage under four main shock and aftershock combination conditions, it was determined that the main shock and aftershock combination with all near-field ground motion caused the greatest damage to the local and overall backfill of the water intake tower. The damage caused by the main shock and aftershock combination with near-field ground motion was significantly greater than that caused by the main shock and aftershock combination with all far-field ground motion. Furthermore, since near-field ground motion has a high-energy velocity pulse effect, it has a greater impact on the structure of the water intake tower. Therefore, incorporating a representative main shock-aftershock combination into the seismic design and strengthening the area connected to the foundation, such as the lower backfill area, can effectively enhance the seismic resistance of the water intake tower structure against cumulative damage. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments of this application or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 A flowchart illustrating a method for constructing a mainshock and aftershock sequence, as provided in this application embodiment;

[0044] Figure 2 A schematic diagram of the curves corresponding to the combination of near-field mainshock and far-field aftershock provided in an embodiment of this application;

[0045] Figure 3 A schematic diagram of the curves corresponding to the combination of far-field mainshock and near-field aftershock provided in an embodiment of this application;

[0046] Figure 4 A flowchart of a water intake tower damage assessment method provided in this application embodiment;

[0047] Figure 5 A schematic diagram of damage increment provided for an embodiment of this application;

[0048] Figure 6 A schematic diagram of an incremental damage index provided in an embodiment of this application;

[0049] Figure 7 This is a schematic diagram of the damage index under various combined working conditions provided in an embodiment of this application. Detailed Implementation

[0050] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0051] In the description of the embodiments of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the embodiments of this application and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; a mechanical connection or an electrical connection; a direct connection or an indirect connection through an intermediate medium; or a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application according to the specific circumstances.

[0052] Figure 1 This is a flowchart illustrating a method for constructing a mainshock and aftershock sequence, as provided in an embodiment of this application. Figure 1 As shown, the method may include the following steps.

[0053] S101. Obtain ground motion data from the earthquake database, and filter out unfavorable mainshock and aftershock sequences from the ground motion data based on the dominant period.

[0054] S102, Interruption of layer distance based on this seismic data For sequences smaller than a preset distance range, a near-field measured mainshock database and a near-field measured aftershock database are constructed; based on the interruption layer distance of this ground motion data... For sequences exceeding a preset distance range, construct a far-field measured mainshock database and a far-field measured aftershock database.

[0055] For example, the preset distance range can be 8-15km, such as 8km, 10km or 15km, etc., and is not limited here.

[0056] S103. Based on the data from the near-field measured mainshock database, the near-field measured aftershock database, the far-field measured mainshock database, and the far-field measured aftershock database, multiple input conditions are constructed and uniform amplitude modulation processing is performed.

[0057] The input conditions are near-field main shock and near-field aftershock, far-field main shock and far-field aftershock, near-field main shock and far-field aftershock, or far-field main shock and near-field aftershock.

[0058] S104. For each main shock and corresponding aftershock in the input working condition, perform amplitude modulation processing according to the intensity ratio coefficient corresponding to the main shock to obtain the target main shock and target aftershock.

[0059] S105. Determine the acceleration response spectrum of the target mainshock within the range of 0–6s, and obtain the spectrum values ​​L1, L2, L3, …, L 150 and average value The main shock spectrum value was obtained by normalizing the data; and the acceleration response spectrum of the aftershock acceleration in the range of 0–6 s was determined, and the spectrum value was obtained. , , ... and average value The aftershock spectrum values ​​were obtained by normalizing the values.

[0060] For example, normalization could be done by standardizing the maximum spectral value to 1, thus focusing more on the consistency of the spectral shape rather than the amplitude.

[0061] S106. Determine the sum of squared residuals SSE between the mainshock spectrum value and the aftershock spectrum value using the first preset formula, and determine the scaling factor k between the mainshock spectrum value and the aftershock spectrum value using the second preset formula.

[0062] For example, the sum of squared residuals (SSE) determined based on the normalized response spectrum measures the consistency of the mainshock and aftershock spectra in the frequency domain, thereby eliminating the interference of amplitude differences on spectral comparison. The scaling factor k reflects the relative intensity relationship between the aftershock and mainshock spectra in terms of overall amplitude. The combined application of these two factors ensures that the selected aftershocks, while maintaining spectral similarity, have a reasonable correspondence in overall intensity level with the mainshock, thus effectively capturing the intensity coupling characteristics between the mainshock and aftershocks.

[0063] S107. The main shock spectrum and aftershock spectrum values ​​with a difference of less than a preset difference threshold between the residual sum of squares SSE and the scaling factor k are used as the matching results, thereby constructing a main shock and aftershock combination with good spectral consistency.

[0064] According to the above technical solution, based on the selected real mainshock and aftershock ground motion records, the spectral matching method is improved by combining unified amplitude modulation processing and normalized response spectrum, which effectively eliminates the influence of ground motion intensity differences on spectral comparison and realizes the spectral similarity control of the mainshock and aftershock combination. The sum of squared residuals (SSE) between normalized response spectra is used as the matching index to select the aftershock record that is closest to the target mainshock spectral shape, so that the constructed mainshock and aftershock combination has the consistency of spectral characteristics and conforms to the physical laws of real earthquake records.

[0065] In one possible implementation, the ground motion data is data from the seismic database that meets preset conditions; these preset conditions include: the magnitude of both the mainshock and aftershocks is not less than 5.0; the horizontal peak ground acceleration (PGA) is greater than or equal to 0.04g; the mean shear wave velocity is greater than 250 m / s; the mainshock and aftershock records are taken from the same station recording the same directional component of the same seismic event; and the selected station has corresponding fault distance data; the unfavorable mainshock-aftershock sequence is the dominant period T of the aftershock sequence. A The dominant period T of the main shock sequence is greater than or equal to M sequence.

[0066] For example, the ground motion database could be the Pacific Earthquake Engineering Research Center (PEER) ground motion database. Adverse mainshock and aftershock sequences that satisfy the above spectral relationships are used as the earthquake input conditions to more realistically assess the impact of aftershocks on the performance degradation of the intake tower structure, thereby providing a more reasonable basis for screening aftershock incremental damage indicators.

[0067] Specifically, some information about unfavorable mainshock and aftershock sequences is illustrated here, as shown in Table 1.

[0068] Table 1:

[0069]

[0070] In one possible implementation, the uniform amplitude modulation process can be to uniformly adjust the peak ground acceleration (PGA) of the main shock and aftershock in the input working condition to the actual earthquake peak ground acceleration of the engineering site, so as to eliminate the influence of the difference in ground motion intensity on the spectral comparison; the acceleration response spectrum is a spectral value determined at 0.04s intervals within the range of 0 to 6s, and the number of spectral values ​​is 150.

[0071] In one possible implementation, the first preset formula is:

[0072] The second preset formula is: .

[0073] For example, the curves generated by the sum of squared residuals (SSE) and scaling factor k under the combined near-field mainshock and far-field aftershock conditions can be as follows: Figure 2 As shown, the curves generated by the sum of squared residuals (SSE) and scaling factor k under the combined conditions of far-field mainshock and near-field aftershock can be obtained as follows: Figure 3 As shown in the figure, the sum of squared residuals (SSE) of both types of combinations remained stable in the range of 0.002–0.012, indicating that the spectral differences between each aftershock and the target mainshock were small and the matching accuracy was high. The scaling factor k basically remained within the range of 0.98–1.10, indicating that the spectral similarity between the mainshock and aftershocks was high after normalization.

[0074] In some embodiments, the near-field mainshock and far-field aftershock, as well as some information on the far-field mainshock and near-field aftershock in the input conditions constructed above, can be shown in Table 2 below.

[0075] Table 2:

[0076]

[0077] Figure 4 This is a flowchart illustrating a method for assessing damage to a water intake tower, as provided in an embodiment of this application. Figure 4 As shown, the method may include the following steps.

[0078] S401. Construct a three-dimensional numerical model of the water intake tower body. Use the unfavorable mainshock and aftershock sequence constructed by the mainshock and aftershock sequence construction method as the input working condition. Determine the displacement parameters and damage index parameters of the three-dimensional numerical model under the action of the mainshock and the action of the mainshock and aftershock in the unfavorable mainshock and aftershock sequence.

[0079] S402. When the displacement parameters cannot reflect the damage increment caused by aftershocks, the damage increment of the three-dimensional numerical model is determined based on the damage index parameters, combined with the third and fourth preset formulas. and incremental damage index This allows us to determine the damage parameters that characterize the increase in aftershock damage.

[0080] The damage parameter is the local damage index at the interface between the tower body and the lower backfill.

[0081] S403. Using the mainshock-aftershock combination and mainshock constructed by the mainshock-aftershock sequence construction method as input conditions, determine the damage parameters and overall tower damage index of the three-dimensional numerical model under the action of the mainshock-aftershock combination and the action of the mainshock, respectively.

[0082] S404. Based on the damage parameters and the overall tower damage index, evaluate the ability of the three-dimensional numerical model to reflect aftershock damage.

[0083] Based on the above technical solutions, through comparative analysis of the damage indices of the backfill and the overall structure under four main shock and aftershock combinations, it was determined that the main shock and aftershock combinations, all of which are near-field, cause the greatest damage to the local and overall backfill of the intake tower. The damage caused by the main shock and aftershock combinations containing near-field ground motion is significantly greater than that caused by the main shock and aftershock combinations, all of which are far-field. Furthermore, since near-field ground motion has a high-energy velocity pulse effect, it has a greater impact on the structure of the intake tower. Therefore, incorporating representative main shock and aftershock combinations into the seismic design and strengthening areas connected to the foundation, such as the lower backfill area, can effectively enhance the seismic resistance of the intake tower structure against cumulative damage.

[0084] In one possible implementation, the three-dimensional numerical model is constructed based on ABAQUS, taking the foundation within the range of 2 times the tower height on the upstream and downstream sides of the water intake tower, the left and right sides, and 1.5 times the tower height at the bottom of the tower as the generation object; the displacement parameters are the maximum displacement of the tower top in the direction along the river, across the river, and vertically; the damage index parameters are the local damage index at the interface between the tower body and the upper and lower backfills and the overall damage index of the tower body.

[0085] For example, the coordinate system of the three-dimensional numerical model of the intake tower can be defined as follows: the Y-axis is along the river, with the water flow direction as the positive direction; the Z-axis is vertical, with the upward direction as the positive direction; the X-axis is the right side of the tower body across the river, with the origin of the coordinate system at the upstream of the intake tower foundation (elevation 1815m). The tower body, backfill soil, and bedrock are all discretized using hexahedral solid elements. The Rayleigh damping coefficient is calculated based on the first two frequencies obtained from linear elastic analysis, and the damping ratio is taken as 5%. The constitutive relation adopts the ABAQUS concrete plastic damage constitutive model. C20 is selected for the tower body concrete, C15 for the backfill soil and base, and C25 for the hoisting frame. The static calculation parameters of the materials are shown in Table 3 below. The key parameters of the ABAQUS concrete damage plastic model are shown in Table 4. Among them, hydrostatic pressure, self-weight, hydrodynamic pressure, and seismic load are mainly considered. The hydrodynamic pressure is simulated using the added mass method, and the seismic load is applied using the boundary acceleration method. The peak ground acceleration (PGA) of the mainshock in the mainshock and aftershock sequence was uniformly modulated to 0.267g, and the aftershocks were modulated proportionally. The magnitude of the vertically input earthquake was considered to be 2 / 3 of the horizontal magnitude. Fixed constraints were used at the bottom of the foundation, and normal constraints were used around the perimeter. The ground motion was input as a uniform massless foundation.

[0086] Table 3:

[0087]

[0088] Table 4:

[0089]

[0090] In one possible implementation, S401 may include: obtaining displacement parameters of the three-dimensional numerical model response under the action of the mainshock and the action of the mainshock and aftershock in the unfavorable mainshock and aftershock sequence; determining the local damage index in the damage index parameters through a fifth preset formula, and determining the overall damage index in the damage index parameters through a sixth preset formula; the fifth preset formula is: ;in, Damage area at a certain elevation The local damage index; Damaged area The Middle Damage indicators for each unit; For the region The Middle The area of ​​each unit; For a certain elevation damage area Weighting coefficients; Damage area The influence coefficient of the crack initiation location is taken as 1.0 on the water-facing side and 0.8 in other cases; Damage area The crack embedment degree influence coefficient is the ratio of crack length to the path length; the sixth preset formula is: ;in, The overall damage index of the structure; This represents the local damage index of the component. The weighting coefficient of the component; Components under seismic loading Energy consumption; This represents the total energy consumption of the structure.

[0091] In one possible implementation, the displacement parameters in S402 above cannot reflect the damage increment caused by aftershocks when: if the difference between the first displacement parameter value under the action of the mainshock in the unfavorable mainshock-aftershock sequence and the second displacement parameter value under the action of the mainshock-aftershock in the unfavorable mainshock-aftershock sequence is less than a preset difference threshold, it is determined that the first displacement parameter value and the second displacement parameter value are close, so that the displacement parameters cannot effectively reflect the damage increment caused by aftershocks; the third preset formula is: ;in, For the increase in damage, Structural damage under the action of main shock and aftershock Structural damage under the action of the main shock; the fourth preset formula is: ;in, This is the incremental damage index.

[0092] For example, the range of this preset difference threshold can be set by the user and is not limited here. In most cases, the maximum displacement at the top of the tower, a displacement-type parameter, occurs during the main shock phase. Only when the peak ground acceleration (PGA) of the aftershock is significantly greater than that of the main shock will the maximum displacement under the action of the main shock and aftershock be greater than the maximum value under the action of the main shock. Therefore, the maximum displacement at the top of the tower is limited by the magnitude of the peak ground acceleration and cannot effectively reflect the damage increment caused by aftershocks. It should not be used as a damage parameter to characterize the damage increment caused by aftershocks.

[0093] In one possible implementation, S402 may include: local damage increment at the interface between the tower body and the lower backfill in the three-dimensional numerical model. The average value is greater than the overall damage increment of the tower body. Mean and local damage increment at the interface between the tower body and the upper backfill The mean, and the incremental damage index of local damage at the interface between the tower body and the lower backfill. The mean is greater than the incremental damage index of the overall tower damage. Mean and incremental damage index of local damage at the interface between the tower body and the upper backfill Under the mean, it is determined that the plastic deformation and damage accumulation are greater at the interface between the tower and the lower backfill, and the local damage is more sensitive to the impact of aftershocks. Therefore, the local damage index at the interface between the tower and the lower backfill is used as a damage parameter to characterize the increase in aftershock damage.

[0094] In some embodiments, refer to Figure 5 In this unfavorable mainshock and aftershock sequence, under the action of the mainshock and aftershock, the overall damage increment of the three-dimensional numerical model is... The mean value can be 0.008, representing the increment of local damage (upper backfill local damage) at the interface between the tower body and the upper backfill in this three-dimensional numerical model. With a mean of 0.013, the increment of local damage (lower backfill local damage) at the interface between the tower body and the lower backfill in this three-dimensional numerical model is represented by the value 0.013. The mean value can be 0.019. It can be seen that the mean local damage increment at the interface between the tower and the lower backfill is the largest, which is attributed to the combined effect of structural constraints and stress concentration in the tower-backfill-foundation system. The lower backfill is directly connected to the foundation and is subject to stronger geometric and kinematic constraints, which leads to higher stiffness differences and stress concentration under seismic loading.

[0095] Reference Figure 6 In this unfavorable mainshock and aftershock sequence, under the action of mainshocks and aftershocks, the incremental damage index of the overall damage in this three-dimensional numerical model is... The mean is 5%, which is the incremental damage index of local damage (upper backfill local damage) at the interface between the tower body and the upper backfill in this three-dimensional numerical model. The mean is 5%, which is the incremental damage index of local damage (lower backfill local damage) at the interface between the tower body and the lower backfill in this three-dimensional numerical model. The average value is 7%. It can be seen that the incremental damage index of local damage at the interface between the tower body and the lower backfill is the largest, with a maximum value of 13%, indicating that the local damage at the interface between the lower backfill and the lower backfill is more sensitive to the impact of aftershocks than the overall damage and the damage to the upper backfill water intake tower.

[0096] In one possible implementation, S404 may include: under the action of a combination of near-field main shocks and aftershocks, the damage to the area at the interface between the tower body and the lower backfill and the tower body as a whole in the three-dimensional numerical model is the greatest, with an overall damage index of 0.5 and a local damage index of 0.4; under the action of a combination of far-field main shocks and aftershocks, the damage to the area at the interface between the tower body and the lower backfill and the tower body as a whole in the three-dimensional numerical model is the least, with an overall damage index of 0.26 and a local damage index of 0.13; under the action of a combination of near-field main shocks and far-field aftershocks, or a combination of far-field main shocks and near-field aftershocks, the damage to the area at the interface between the tower body and the lower backfill and the tower body as a whole in the three-dimensional numerical model is between the damage caused by a combination of near-field main shocks and aftershocks and a combination of far-field main shocks and aftershocks.

[0097] For example, a diagram illustrating the damage index under various combined operating conditions can be found here. Figure 7 As shown, the near-field main shock and aftershock combinations cause the most significant damage to the local area of ​​the backfill beneath the intake tower (the area at the interface between the tower body and the backfill). Conversely, the far-field main shock and aftershock combinations have the least impact on the intake tower. The other two main shock and aftershock combinations cause similar levels of damage to the intake tower, falling between the first two types. This is because near-field ground motions often exhibit strong pulse characteristics, with high peak acceleration and high energy concentration. They easily cause transient impacts and local stress concentrations at weak points such as the tower top and the backfill interface, making them more prone to causing significant damage. Therefore, the seismic design of intake towers should focus on considering the influence of near-field main shock and aftershock sequences and the changes in local damage to the backfill.

[0098] The various embodiments in this specification are described in a progressive manner. For the same or similar parts between the various embodiments, please refer to each other. Each embodiment focuses on describing the differences from other embodiments.

[0099] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of this application.

Claims

1. A method for constructing a mainshock-aftershock sequence, characterized in that, The method includes: Seismic motion data are obtained from an earthquake database, and unfavorable mainshock and aftershock sequences are selected from the seismic motion data based on the dominant period. Based on the aforementioned seismic data, the interlayer distance is interrupted. For sequences smaller than a preset distance range, a near-field measured mainshock database and a near-field measured aftershock database are constructed; based on the interruption layer distance of the ground motion data... For sequences exceeding a preset distance range, construct a far-field measured mainshock database and a far-field measured aftershock database; Based on the data from the near-field measured mainshock database, near-field measured aftershock database, far-field measured mainshock database, and far-field measured aftershock database, multiple input conditions are constructed and uniform amplitude modulation processing is performed; the input conditions are near-field mainshock and near-field aftershock, far-field mainshock and far-field aftershock, near-field mainshock and far-field aftershock, or far-field mainshock and near-field aftershock. For each main shock and its corresponding aftershock in the input working condition, amplitude modulation is performed according to the intensity ratio coefficient corresponding to the main shock to obtain the target main shock and target aftershock. Determine the acceleration response spectrum of the target mainshock within the range of 0–6s, and obtain the spectral values ​​L1, L2, L3, …, L 150 and average value The main shock spectrum value was obtained by normalizing the data; and the acceleration response spectrum of the aftershock acceleration in the range of 0–6 s was determined, and the spectrum value was obtained. , , ... and average value The aftershock spectrum values ​​were obtained by normalization. The sum of squared residuals SSE between the mainshock spectrum value and the aftershock spectrum value is determined by a first preset formula, and the scaling factor k between the mainshock spectrum value and the aftershock spectrum value is determined by a second preset formula. The mainshock spectrum and aftershock spectrum values ​​with a difference of less than a preset difference threshold between the residual sum of squares (SSE) and the scaling factor (k) are used as the matching results to construct a mainshock and aftershock combination with good spectral consistency.

2. The method according to claim 1, characterized in that, The ground motion data are data in the earthquake database that meet preset conditions; the preset conditions are that the magnitude of the main shock and aftershocks are not less than 5.0, the horizontal peak ground acceleration (PGA) is greater than or equal to 0.04g, the average shear wave velocity is greater than 250m / s, the main shock and aftershock records are taken from the same station recording the same earthquake event in the same direction, and the selected station has corresponding fault distance data. The unfavorable mainshock and aftershock sequence is the dominant period T of the aftershock sequence. A The dominant period T of the main shock sequence is greater than or equal to M sequence.

3. The method according to claim 1, characterized in that, The unified amplitude modulation process involves uniformly adjusting the peak ground acceleration (PGA) of the mainshock and aftershock in the input working condition to the actual peak ground acceleration of the earthquake at the engineering site; the acceleration response spectrum consists of 150 spectral values ​​determined at 0.04s intervals within the range of 0 to 6s.

4. The method according to claim 1, characterized in that, The first preset formula is: The second preset formula is: .

5. A method for assessing damage to a water intake tower, characterized in that, The method includes: A three-dimensional numerical model of the water intake tower body is constructed. The unfavorable main shock and aftershock sequence constructed by the method described in any one of claims 1 to 4 is used as the input working condition. The displacement parameters and damage index parameters of the three-dimensional numerical model under the action of the main shock and the action of the main shock and aftershock are determined in the unfavorable main shock and aftershock sequence. When the displacement parameters cannot reflect the damage increment caused by aftershocks, the damage increment of the three-dimensional numerical model is determined based on the damage index parameters, combined with the third and fourth preset formulas. and incremental damage index This leads to the determination of damage parameters characterizing the increase in aftershock damage; the damage parameters are the local damage index at the interface between the tower body and the lower backfill. Using the main shock and aftershock combination and main shock constructed by any one of claims 1 to 4 as input conditions, the damage parameters and overall tower damage index of the three-dimensional numerical model under the action of the main shock and aftershock combination and under the action of the main shock are determined respectively. Based on the damage parameters and the overall tower damage index, the ability of the three-dimensional numerical model to reflect aftershock damage is evaluated.

6. The method according to claim 5, characterized in that, The three-dimensional numerical model is constructed based on ABAQUS, and the foundation within the range of 2 times the tower height on the upstream and downstream sides, left and right sides, and 1.5 times the tower height at the bottom of the tower is taken as the generated object; the displacement parameters are the maximum displacement of the tower top in the direction along the river, across the river, and vertically; the damage index parameters are the local damage index at the interface between the tower body and the upper and lower backfills and the overall damage index of the tower body.

7. The method according to claim 5, characterized in that, The determination of displacement-type parameters and damage index-type parameters of the three-dimensional numerical model under the action of the mainshock and the action of the mainshock and aftershock in the unfavorable mainshock and aftershock sequence includes: In the unfavorable mainshock and aftershock sequence, the displacement parameters of the three-dimensional numerical model response are obtained under the action of the mainshock and the action of the mainshock and aftershock. The local damage index in the damage index class parameters is determined by the fifth preset formula, and the overall damage index in the damage index class parameters is determined by the sixth preset formula. The fifth preset formula is: ;in, Damage area at a certain elevation The local damage index; Damaged area The Middle Damage indicators for each unit; For the region The Middle The area of ​​each unit; For a certain elevation damage area Weighting coefficients; Damage area The influence coefficient of the crack initiation location is taken as 1.0 on the water-facing side and 0.8 in other cases; Damage area The crack embedding degree influence coefficient is the ratio of crack length to the path length. The sixth preset formula is: ;in, The overall damage index of the structure; This represents the local damage index of the component. The weighting coefficient of the component; Components under seismic loading Energy consumption; This represents the total energy consumption of the structure.

8. The method according to claim 7, characterized in that, The displacement parameters cannot reflect the damage increment caused by aftershocks when: if the difference between the first displacement parameter value under the action of the main shock in the unfavorable main shock and aftershock sequence and the second displacement parameter value under the action of the main shock and aftershock in the unfavorable main shock and aftershock sequence is less than a preset difference threshold, the first displacement parameter value and the second displacement parameter value are determined to be close, so that the displacement parameters cannot effectively reflect the damage increment caused by aftershocks. The third preset formula is: ;in, For the increase in damage, Structural damage under the action of main shock and aftershock Structural damage under the action of the main shock; the fourth preset formula is: ;in, This is the incremental damage index.

9. The method according to claim 8, characterized in that, The damage increment of the three-dimensional numerical model is determined based on the damage index parameters and in combination with the third and fourth preset formulas. and incremental damage index This leads to the determination of damage parameters characterizing the increase in aftershock damage, including: Local damage increment at the interface between the tower body and the lower backfill in the three-dimensional numerical model The average value is greater than the overall damage increment of the tower body. Mean and local damage increment at the interface between the tower body and the upper backfill The mean, and the incremental damage index of local damage at the interface between the tower body and the lower backfill. The mean is greater than the incremental damage index of the overall tower damage. Mean and incremental damage index of local damage at the interface between the tower body and the upper backfill Under the mean, it is determined that the plastic deformation and damage accumulation are greater at the interface between the tower body and the lower backfill, and the local damage is more sensitive to the impact of aftershocks. Therefore, the local damage index at the interface between the tower body and the lower backfill is used as a damage parameter to characterize the increase in aftershock damage.

10. The method according to claim 9, characterized in that, The evaluation of the three-dimensional numerical model's ability to reflect aftershock damage based on the damage parameters and the overall tower damage index includes: Under the combined effect of main shocks and aftershocks, all of which are near-field, the greatest damage is caused to the area at the interface between the tower body and the lower backfill and the tower body as a whole in the three-dimensional numerical model, with an overall damage index of 0.5 and a local damage index of 0.

4. Under the combined action of the main shock and aftershocks, which are all in the far field, the damage to the area at the interface between the tower body and the lower backfill and the tower body as a whole in the three-dimensional numerical model is minimal, with an overall damage index of 0.26 and a local damage index of 0.

13. The damage to the area at the interface between the tower body and the lower backfill and the tower body as a whole caused by the combined action of near-field main shock and far-field aftershock, or the combined action of far-field main shock and near-field aftershock, falls between the damage caused by the combination of near-field main shock and aftershock and the damage caused by the combination of far-field main shock and aftershock.

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