A method of defining near-fault bridge

Abstract

The present application relates to the technical field of bridge seismic design, and particularly relates to a method for defining a near-fault bridge and application thereof, comprising the following steps: S1: collecting seismic records and geological data of the bridge location; S2: drawing a near-fault ground motion fault rupture permanent displacement attenuation relationship curve based on the data collected in step S1; S3: determining the displacement response of the transverse bridge direction, longitudinal bridge direction or vertical bridge direction caused by the permanent displacement; S4: deriving a displacement response formula acting on the bridge; S5: when the static displacement of the bridge structure caused by the fault rupture displacement exceeds half of the dynamic effect allowance (expansion joint) D, the bridge can be determined as a near-fault bridge. The present application can accurately calculate the displacement size and position that the bridge may experience under specific seismic conditions, can predict the specific influence of different types of faults (such as strike-slip faults and dip-slip faults) on the bridge, and thus provides a strong predictive tool for design.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bridge seismic design, and particularly relates to a method for defining near-fault bridge. BACKGROUND

[0002] Seismic ground motion is divided into far-field and near-field seismic ground motion, and the far-field seismic ground motion is generally a range of more than 20 km away from the source, and the near-field seismic ground motion is a range of less than 20 km. Near-fault earthquake is a very special near-field seismic ground motion, which not only has ground vibration but also has surface rupture permanent displacement. The bridge structure will be subjected to the double rupture factors of ground vibration and surface rupture, and the definition of near-fault bridge must consider the surface rupture permanent displacement in addition to the strong ground vibration of near-field seismic ground motion. The rupture displacement attenuation of near-fault seismic ground motion causes inconsistent displacement between bridge piers, thereby damaging the bridge structure. The definition of near-fault bridge must consider the influence of surface rupture permanent displacement on the mechanical behavior of the bridge. The surface rupture permanent displacement is related to factors such as magnitude and source mechanism (strike-slip fault and dip-slip fault), and the bridge damage is also related to the design parameters of the structure itself (main span length, pier and support stiffness). On the basis of considering the above two factors, the distance of the near-fault bridge from the fault is comprehensively determined, so as to define the concept of near-fault bridge. After the concept is clear, special seismic and damping measures can be taken for the near-fault bridge to reduce the damage of near-fault seismic ground motion to the bridge structure. Therefore, the present application proposes to define the concept of near-fault bridge based on the double factors of seismic ground motion characteristics (magnitude, source mechanism and surface rupture permanent displacement attenuation relationship) and bridge structure design parameters (main span length, pier and support stiffness). SUMMARY

[0003] The purpose of the present application is to provide a method for defining near-fault bridge, which defines and identifies near-fault bridge based on the double factors of seismic ground motion characteristics and bridge structure design parameters.

[0004] In order to achieve the above technical purposes and achieve the above technical effects, the present application is realized by the following technical scheme:

[0005] A method for defining near-fault bridge, comprising the following steps:

[0006] S1: collecting seismic records and geological data of the bridge location;

[0007] S2: drawing a near-fault seismic ground motion fault rupture permanent displacement attenuation relationship curve based on the data collected in step S1, and describing the change relationship of permanent displacement with fault distance under different magnitude conditions.

[0008] S3: According to the attenuation curve obtained in step S2, combined with the fault type analysis and the length L of the main span of the bridge, the size of the permanent displacement and its position of action on the bridge are estimated to determine the displacement response in the transverse direction, longitudinal direction or vertical direction of the bridge caused by the permanent displacement.

[0009] S4: According to the principle of structural mechanics, combined with the stiffness parameters (K1 and K2) of the bridge and the permanent displacement value, the displacement reaction formula acting on the bridge is derived. The displacement reaction of the bridge under the influence of permanent displacement is calculated under the conditions of strike-slip fault and dip-slip fault.

[0010] S5: The in-bridge displacement calculated by the formula derived in step S4 is compared with half of the dynamic effect reservation D. If the structural static displacement caused by the permanent displacement exceeds half of the dynamic effect reservation, the bridge is determined to be a near-fault bridge.

[0011] Further, the data collection in step S1 specifically includes:

[0012] Magnitude (M w ): The moment magnitude of the earthquake, representing the total amount of energy released by the earthquake.

[0013] Source mechanism: Including fault type, mainly divided into strike-slip fault and dip-slip fault.

[0014] Seismic fault rupture permanent displacement attenuation relationship: This is a curve representing the change of fault rupture permanent displacement with fault distance, usually derived from a seismological model.

[0015] Bridge design parameters: including main span length (L), pier stiffness (K1), support stiffness (K2), dynamic effect reservation (D, equal to half of the expansion joint width).

[0016] Further, step S2 specifically includes: statistical analysis of seismic event seismic data, drawing scatter plots of upper and lower disc seismic displacement attenuation, and fitting the curve of seismic permanent displacement with fault distance, represented as:

[0017] GSRPD=f(R rup , M w )

[0018] Further, step S3 specifically includes:

[0019] The length of the main span of the bridge is calibrated according to the fault distance, and the permanent displacement ΔP D acting on the bridge pier is found on the curve, and the permanent displacement ΔP D acting on the transverse and longitudinal directions of the bridge under the condition of strike-slip fault, and the permanent displacement ΔP D acting on the vertical and longitudinal directions of the bridge under the condition of dip-slip fault.

[0020] Further, the step S4 specifically comprises:

[0021] The pier stiffness is K1, and the height is H1, and according to structural mechanics, the following can be obtained

[0022]

[0023] Similarly, the support stiffness is EI is the bending stiffness; and the equivalent stiffness of the pier and the support is

[0024]

[0025] The following is obtained

[0026]

[0027] K 11 is the stiffness coefficient caused by unit displacement ΔX;

[0028] Under the action of permanent displacement ΔP DX , R=-3K eff ×ΔP DX

[0029] R is the counterforce on the additional chain bar;

[0030] According to the basic equation of the displacement method, the following can be obtained:

[0031] K 11 ΔX+R=0

[0032] The following is obtained

[0033]

[0034] According to the above, the longitudinal displacement of the bridge under the action of permanent displacement ΔP DX is

[0035]

[0036] Further, the step S5 specifically comprises:

[0037] When the static displacement of the bridge structure caused by the fault rupture displacement exceeds half of the dynamic effect allowance (expansion joint) D, the bridge can be determined as a near-fault bridge.

[0038] That is That is, when ΔP DX ≥D, the bridge is a near-fault bridge;

[0039] ΔP DX With the main span L and the fault distance R rup , according to the main span L and the fault distance Rrup calibrate ΔP DX , judge ΔP DX whether it is greater than the dynamic effect reservation D, if greater, it is near-fault bridge, otherwise not.

[0040] The near-fault bridge judgment criterion of dip-slip fault is consistent with strike-slip fault, which is:

[0041] When the fault rupture displacement causes the static displacement of the bridge structure to exceed half of the dynamic effect reservation (expansion joint) D, the bridge can be determined as a near-fault bridge.

[0042] That is That is ΔP DX ≥D, the bridge is a near-fault bridge;

[0043] ΔP DX With the main span span L, fault distance R rup and the change curve of the permanent displacement of the ruptured fault with the fault distance, according to the main span span L and fault distance R rup and the change curve of the permanent displacement of the ruptured fault with the fault distance in the actual situation, ΔP DX is calibrated, and ΔP DX whether it is greater than the dynamic effect reservation D is judged, if greater, it is near-fault bridge, otherwise not.

[0044] On the other hand, the application proposes the application of the above method in the definition of near-fault bridge concept research.

[0045] The beneficial effects of the application are:

[0046] Traditionally, the seismic design of bridges often only considers the intensity of ground motion and rarely considers the permanent displacement of surface rupture. This technical solution can accurately calculate the displacement size and position that the bridge may experience under specific seismic conditions by collecting detailed seismic records and geological data and based on the permanent displacement attenuation relationship curve drawn based on these data. This analysis is based on the principles of seismology and structural dynamics, which can predict the specific effects of different types of faults (such as strike-slip faults and dip-slip faults) on bridges, thereby providing a predictive tool for design. It can assist in predicting the behavior of bridges in actual earthquakes during the design stage, so that the seismic design not only depends on general design standards, but is based on detailed analysis of specific ground motion characteristics and bridge responses, improving the pertinence and adaptability of the design.

[0047] The definition method of the application considers the following influence factors: magnitude, source mechanism (fault type: strike-slip fault and dip-slip fault) and near-fault ground motion fault rupture permanent displacement attenuation relationship curve, structure design parameters: main span span, pier and support stiffness parameters, dynamic effect reservation (half of the expansion joint width). The near-fault bridge criterion defined in this way is more reasonable, and the accuracy is greatly improved.

[0048] In addition, based on the foregoing influence factors, the application also proposes a determination formula, which comprehensively considers the fault mechanism, bridge span, pier support stiffness and dynamic effect reservation. The calculation complexity is reduced, and the determination accuracy is improved.

[0049] The determination of the near-fault bridge will be beneficial to the reasonable design of the bridge, avoid collision damage, improve the seismic performance and safety of the bridge, and at the same time, it is of great significance to perfect the corresponding seismic design standard.

[0050] Of course, implementing any product of the application does not necessarily need to achieve all the advantages described above at the same time. BRIEF DESCRIPTION OF DRAWINGS

[0051] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description only some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0052] Figure 1 The variation of the near-fault ground motion fault rupture permanent displacement with the fault distance of the application;

[0053] Figure 2 The front view and parameter description of the simply supported bridge of the application; the main span span L of the bridge, the pier stiffness K1, the support stiffness K2, the fault permanent displacement ΔP conducted to the bottom of the pier D , dynamic effect reservation D;

[0054] Figure 3 The permanent displacement acting on the pier of the application is shown in the schematic diagram; the main span span L is calibrated on the horizontal coordinate axis, and the permanent displacement ΔP is calibrated on the vertical coordinate axis D ;

[0055] Figure 4 The permanent displacement acting on the bridge in the transverse and longitudinal directions of the bridge of the application is shown in the schematic diagram;

[0056] Figure 5 The permanent displacement acting on the bridge in the vertical and longitudinal directions of the bridge of the application is shown in the schematic diagram;

[0057] Figure 6Moment diagram under unit displacement for the embodiment 2 of the present application;

[0058] Figure 7 Moment diagram under additional chain bar reaction force for the embodiment 2 of the present application;

[0059] Figure 8 Seismic displacement attenuation scatter diagram of upper and lower disks;

[0060] Figure 9 Schematic diagram of fitting permanent displacement of ground motion with fault distance;

[0061] In the drawings:

[0062] 1, simplified bridge main span, 2, bridge pier, 3, bridge side span, 4, pile cap, 5, support, 6, strike-slip fault, 7, dip-slip fault. DETAILED DESCRIPTION

[0063] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0064] Embodiment 1

[0065] The method for defining a bridge near a fault in the embodiment comprises the following steps.

[0066] S1: Collecting seismic records and geological data of the bridge location;

[0067] S2: Drawing a fault rupture permanent displacement attenuation relationship curve of near-fault ground motion based on the data collected in step S1, and describing the variation relationship of permanent displacement with fault distance under different magnitude conditions.

[0068] S3: According to the attenuation curve obtained in step S2, combining fault type analysis and bridge main span length L, estimating the size of permanent displacement and its action position on the bridge, to determine the displacement response in the transverse bridge direction, longitudinal bridge direction or vertical bridge direction caused by permanent displacement.

[0069] S4: According to the principle of structural mechanics, combining the stiffness parameters (K1 and K2) of the bridge and the permanent displacement value, a displacement reaction formula acting on the bridge is derived. The displacement response of the bridge under the influence of permanent displacement under the conditions of strike-slip fault and dip-slip fault is calculated.

[0070] S5: Calculate the along-bridge displacement using the formula derived in step S4, and compare this displacement with half of the dynamic effect allowance D. If the structural static displacement caused by the permanent displacement exceeds half of the dynamic effect allowance, the bridge is determined to be a near-fault bridge.

[0071] The near-fault bridge has a main span length L;

[0072] The pier and support stiffnesses are defined as K1 and K2, respectively;

[0073] The pier and support heights are defined as H1 and H2, respectively;

[0074] The dynamic effect allowance parameter is D.

[0075] In this embodiment, the data collection in step S1 specifically includes:

[0076] Magnitude (M w ): The moment magnitude of the earthquake, representing the total amount of energy released by the earthquake.

[0077] Source mechanism: Including fault type, mainly divided into strike-slip fault and dip-slip fault.

[0078] Seismic fault rupture permanent displacement decay relationship: This is a curve representing the change of fault rupture permanent displacement with fault distance, usually derived from a seismological model.

[0079] Bridge design parameters: Including main span length (L), pier stiffness (K1), support stiffness (K2), dynamic effect allowance (D, equal to half of the expansion joint width).

[0080] In this embodiment, the fault rupture permanent displacement decay relationship curve in step S2 is represented as:

[0081] GSRPD = f(R rup , M w )

[0082] Statistical 80 sets of seismic data in Chi-Chi earthquake events, the long-period component shows the relationship between permanent displacement and fault distance, the up-and-down disc seismic displacement decay scatter plot is shown in Figure 8 .

[0083] According to the scatter plot, the approximate seismic permanent displacement curve with fault distance is fitted, as shown in Figure 9 .

[0084] In this embodiment, step S3 specifically includes:

[0085] In the fault distance calibration bridge main span, according to the main span length, find out the permanent displacement ΔP D, the permanent displacement ΔP D acting on the transverse and longitudinal directions of the bridge, the permanent displacement ΔP D acting on the vertical and longitudinal directions of the bridge.

[0086] In the embodiment, the step S4 specifically comprises:

[0087] The pier stiffness is K1, and the height is H1, and according to structural mechanics, the permanent displacement ΔP

[0088]

[0089] Similarly, the support stiffness is EI is the bending stiffness, and the equivalent stiffness of the pier and the support is

[0090]

[0091] The permanent displacement ΔP

[0092]

[0093] K 11 is the stiffness coefficient caused by the unit displacement ΔX;

[0094] Under the action of the permanent displacement ΔP DX , R=-3K eff ×ΔP DX

[0095] R is the counterforce on the additional chain bar;

[0096] According to the basic equation of the displacement method, the following is obtained:

[0097] K 11 ΔX+R=0

[0098] The permanent displacement ΔP

[0099]

[0100] According to the above, the transverse displacement of the bridge under the action of the permanent displacement ΔP DX is obtained.

[0101]

[0102] In the embodiment, the step S5 specifically comprises:

[0103] When the static displacement of the bridge structure caused by the fault rupture displacement exceeds half of the dynamic effect allowance (expansion joint) D, the bridge can be determined as a near-fault bridge.

[0104] That is, That is, ΔP DXWhen the value is ≥D, the bridge is a bridge near a fault.

[0105] ΔP DX With the main span L and fault distance R rup Regarding the main span L and fault distance R in the actual situation. rup Calibrate ΔP DX Determine ΔP DX If the dynamic effect is greater than the reserved D, it means that the bridge is a bridge near a fault; otherwise, it is not.

[0106] The criteria for identifying bridges near dip-slip faults are the same as those for strike-slip faults:

[0107] When the static displacement of a bridge structure caused by fault rupture exceeds half of the dynamic effect reserved (expansion joint) D, the bridge can be determined to be a bridge near a fault.

[0108] Right now That is, ΔP DX When the value is ≥D, the bridge is a bridge near a fault.

[0109] ΔP DX With the main span L and fault distance R rup And the curve showing the relationship between the permanent displacement of the ruptured fault and the fault distance, based on the actual main span L and fault distance R. rup And the curve showing the relationship between the permanent displacement of the ruptured fault and the fault distance was used to calibrate ΔP. DX Determine ΔP DX If the dynamic effect is greater than the reserved D, it means that the bridge is a bridge near a fault; otherwise, it is not.

[0110] On the other hand, this invention proposes the application of the above method in the conceptual study of defining near-fault bridges.

[0111] Example 2

[0112] Definition and formula of near-fault bridges under strike-slip faults

[0113] Permanent displacement and magnitude of near-fault ground motion fault rupture (M) w ), fault distance (R) rup The permanent displacement attenuation curve of a fault rupture is related to the fault dip angle (δ). This invention provides a curve that better reflects the actual situation, describing the relationship between permanent displacement and fault distance. Figure 1 As shown.

[0114] Combination Figure 2 The parameters of the simply supported bridge include: the main span L, the pier stiffness K1, the bearing stiffness K2, and the permanent fault displacement ΔP transmitted to the bottom of the pier. D, dynamic effect reserve D (half of the expansion joint width), etc., to derive specific formulae;

[0115] In this embodiment, in Figure 1 The fault distance calibration bridge main span span, according to the main span span in the curve to find out the permanent displacement ΔP D , as shown in Figure 3 ;

[0116] The resulting permanent displacement ΔP D acting on the bridge transverse and longitudinal bridge, as shown in Figure 4 ;

[0117] According to the relevant knowledge of structural mechanics, the calculation formula is derived as follows:

[0118] The pier stiffness is K1, and the height is H1. According to the knowledge of structural mechanics, it can be obtained that

[0119]

[0120] Similarly, the support stiffness is The equivalent stiffness of the pier and support is

[0121]

[0122] In Figure 6 In

[0123]

[0124]

[0125] Then in Figure 7 Permanent displacement ΔP DX R1 = -3K eff × ΔP DX

[0126] Then according to the basic equation of displacement method, we can get:

[0127] K 11 ΔX + R = 0

[0128]

[0129]

[0130] In summary, the bridge in the permanent displacement ΔP DX The transverse displacement of the bridge under the action of the permanent displacement ΔP

[0131]

[0132] ​​The judgment condition is that when the static displacement of the bridge structure caused by the fault rupture displacement exceeds half of the dynamic effect allowance (the expansion joint) D, the bridge is determined to be a near-fault bridge.

[0133] That is ΔP DX ≥D, the bridge is a near-fault bridge,

[0134] ΔP DX With the main span L and the fault distance R rup , according to the main span L and the fault distance R rup in the actual situation, ΔP DX is calibrated, and whether ΔP DX is greater than the dynamic effect allowance D is judged. If it is greater, it means that the bridge belongs to a near-fault bridge, otherwise it does not.

[0135] Example 3

[0136] Definition and formula of near-fault bridge under dip-slip fault

[0137] The definition method and formula derivation process of the near-fault bridge under the strike-slip fault in Example 2 are given. In this embodiment, the definition and formula of the near-fault bridge under the dip-slip fault will be studied.

[0138] In this embodiment, the difference between and Example 2 is that the permanent displacement ΔP D of the dip-slip fault acts on the vertical and longitudinal directions of the bridge, as shown in Figure 5 , and the rest of the parameters do not change. It is proved by formula derivation that the displacement of the bridge in the bridge direction is only related to the permanent displacement ΔP DX of the rupture fault, so the near-fault bridge judgment criterion of the dip-slip fault is consistent with that of the strike-slip fault, and both are:

[0139] The judgment condition is that when the static displacement of the bridge structure caused by the fault rupture displacement exceeds half of the dynamic effect allowance (the expansion joint) D, the bridge is determined to be a near-fault bridge.

[0140] That is ΔP DX ≥D, the bridge is a near-fault bridge,

[0141] ΔP DX With the main span L, the fault distance R rup , and the change curve of the permanent displacement of the rupture fault with the fault distance, according to the main span L and the fault distance R rup in the actual situation, ΔP DX is calibrated, and whether ΔP DX is greater than the dynamic effect allowance D is judged. If it is greater, it means that the bridge belongs to a near-fault bridge, otherwise it does not.

[0142] The preferred embodiments of the application disclosed above are only to help explain the present application. The preferred embodiments are not intended to be exhaustive or to limit the application to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the application be limited not with this detailed description, but rather by the claims and the full range of equivalents to which such claims are entitled.

Claims

1. A method for defining bridges near faults, characterized in that, Includes the following steps: S1: Collect seismic records and geological data of the bridge location; S2: Based on the data collected in step S1, plot the permanent displacement decay curve of the fault rupture near the fault to describe the relationship between permanent displacement and fault distance under different magnitude conditions. S3: Based on the attenuation curve obtained in step S2, combined with the fault type analysis and the main span length L of the bridge, estimate the magnitude of the permanent displacement and its position on the bridge to determine the transverse, longitudinal, or vertical displacement response caused by the permanent displacement. S4: Based on the principles of structural mechanics, combined with the stiffness parameters and permanent displacement values ​​of the bridge, derive the displacement response formula acting on the bridge; calculate the displacement response of the bridge under the influence of permanent displacement in the case of strike-slip faults and dip-slip faults. S5: Calculate the longitudinal displacement of the bridge using the formula derived in step S4, and compare this displacement with half of the dynamic effect reserve D; if the static displacement of the structure caused by the permanent displacement exceeds half of the dynamic effect reserve, then the bridge is determined to be a bridge near a fault. Step S4 specifically includes: The pier stiffness is K1, and the height is H1. According to structural mechanics, we can obtain... Similarly, the support stiffness can be obtained as follows: EI is the bending stiffness; therefore, the equivalent stiffness of the pier and bearing is: Seek K 11 Stiffness coefficient for unit displacement ΔX; In permanent displacement ΔP DX R = -3K under action eff ×ΔP DX R is the reaction force on the additional link; According to the basic equations of the displacement method, we can obtain: K 11 ΔX+R=0 Seek In summary, the bridge under permanent displacement ΔP DX The longitudinal displacement of the bridge under the action is 2. The method for defining bridges near faults as described in claim 1, characterized in that: The data collection in step S1 specifically includes: Magnitude: The moment magnitude of an earthquake represents the total amount of energy released during the earthquake; Earthquake source mechanism: includes fault type, which is divided into strike-slip faults and dip-slip faults; Attenuation relationship of permanent displacement due to seismic fault rupture: a curve characterizing the change of permanent displacement due to fault rupture with fault distance; Bridge design parameters include main span, pier stiffness, bearing stiffness, and dynamic effect allowance.

3. The method for defining bridges near faults as described in claim 1, characterized in that: Step S2 specifically includes: statistically analyzing ground motion data during earthquake events, plotting scatter plots of seismic displacement attenuation in the hanging wall and footwall, and fitting a curve of permanent ground motion displacement versus fault distance based on the scatter plots, expressed as: GSRPD=f(R rup ,M w ) Where R rup M is the fault distance. w The magnitude is [magnitude].

4. The method for defining bridges near faults as described in claim 1, characterized in that: Step S3 specifically includes: The main span of the bridge is determined by calibrating the fault distance, and the permanent displacement ΔP acting on the bridge piers is found on the curve based on the main span. D Under strike-slip fault conditions, the obtained permanent displacement ΔP D The permanent displacement ΔP obtained under the conditions of dip-slip fault acting on the transverse and longitudinal directions of the bridge. D The vertical and longitudinal directions acting on the bridge.

5. The method for defining a bridge near a fault as described in claim 1, characterized in that: Step S5 specifically includes: When the static displacement of a bridge structure caused by fault rupture exceeds half of the dynamic effect allowance D, the bridge can be determined to be a bridge near a fault. Right now That is, ΔP DX When the value is ≥D, the bridge is a bridge near a fault. The criteria for identifying bridges near dip-slip faults are the same as those for strike-slip faults: When the static displacement of a bridge structure caused by fault rupture exceeds half of the dynamic effect allowance D, the bridge can be determined to be a bridge near a fault. Right now That is, ΔP DX When the value is ≥D, the bridge is a bridge near a fault.

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