Transmission tower vulnerability assessment method considering earthquake and landslide effects

Abstract

The present invention proposes a transmission tower vulnerability assessment method that comprehensively considers the effects of earthquakes and landslides. The method collects historical earthquake records in a target area and design parameters and performance data of transmission towers to establish a probabilistic earthquake demand model for transmission towers to predict the effects of earthquakes on transmission towers. Based on the influencing factors of landslides caused by earthquakes in the target area, a landslide susceptibility index is calculated using a binary Logistic regression model to assess the risk of landslides to transmission towers. Combining the earthquake demand model and the landslide susceptibility index, the disaster resistance of the transmission tower is calculated, thereby comprehensively assessing the vulnerability of the transmission tower to earthquake and landslide disasters. The present invention provides an effective tool and method for safety assessment and disaster prevention and mitigation of transmission towers, and the vulnerability analysis and research on transmission towers under earthquakes and landslides has extremely important practical significance and engineering practical value.

Description

Technical Field

[0001] The invention belongs to the technical field of power transmission towers, and in particular relates to a method for evaluating the vulnerability of power transmission towers by comprehensively considering the effects of earthquakes and landslides. Background Art

[0002] The transmission network system is an important lifeline project. As an important part of the transmission network, high-voltage transmission towers will inevitably pass through high seismic intensity areas and high-risk areas for geological disasters. With the continuous commissioning of ultra-high voltage and long-distance transmission projects, the complexity of the transmission tower system has increased significantly. The destructiveness caused by earthquakes and secondary disasters has also become increasingly complex, systematic and nonlinear. How to quantitatively evaluate the degree of damage caused by earthquakes and their secondary disasters to the transmission tower line system has always been a hot topic and difficulty in the field of disaster assessment.

[0003] Existing technology expresses earthquake risk as three parts: earthquake hazard, vulnerability of engineering facilities and affected scale, establishing a basic framework for earthquake loss assessment. In this framework, the vulnerability of engineering facilities is the core content of conducting earthquake loss assessment and building earthquake catastrophe risk models. Vulnerability analysis combined with the relevant results of earthquake hazard and landslide hazard assessment can provide important reference for the site selection and route selection of transmission lines and the safety protection of existing lines.

[0004] In the actual use environment of transmission towers, landslide disasters caused by earthquake disasters often have a comprehensive impact on transmission towers. Existing assessment models often use simple linear or nonlinear relationships to describe the relationship between seismic intensity and transmission tower response, ignoring the impact of seismic spectrum characteristics, duration and other factors on the response of transmission towers. However, traditional transmission tower vulnerability assessment methods often only consider the impact of a single natural disaster factor, earthquake, and do not consider the impact of the superposition of landslide disaster factors caused by earthquakes on the stability of transmission towers. This leads to large deviations in the assessment results, which cannot accurately reflect the true vulnerability of transmission towers in complex natural environments.

[0005] Therefore, from the perspective of improving the seismic resistance of the transmission network and ensuring the safe operation of the power grid, a transmission tower vulnerability assessment method that comprehensively considers the effects of earthquakes and landslides is needed. Summary of the invention

[0006] The present invention aims at the above technical problems and provides a method for evaluating the vulnerability of transmission towers by comprehensively considering the effects of earthquakes and landslides, comprising the following steps:

[0007] Step S1, establishing a probabilistic seismic demand model for transmission towers in a target area based on a seismic intensity index and a structural seismic demand index.

[0008] The target area transmission tower probabilistic seismic demand model is the probabilistic relationship between the seismic intensity index IM and the structural seismic demand index D, which is expressed in the form of log-normal distribution as follows:

[0009]

[0010] Where P(D≥u|IM) represents the probability between the earthquake intensity index IM and the structural seismic demand index D; Φ represents the standard normal cumulative distribution function; u represents the threshold value of different limit states; S D Represents the median value of the structural seismic demand index D; β D|IM represents the logarithmic standard deviation.

[0011] The median value S of the structural seismic demand index D D The relationship between the seismic intensity index IM is expressed in exponential form: S D =a×IM b .

[0012] Convert the exponential relationship to a logarithmic relationship and we get: ln(S D )=bln(IM)+c, where b and c are the linear coefficient and constant term of linear regression analysis respectively, a is the constant term, and c=ln(a).

[0013] Step S2, according to the influencing factors of landslides caused by earthquakes in the target area, the landslide susceptibility index is calculated based on the binary logistic regression model.

[0014] The binary logistic regression model is: ln(1-pp)=β0+β1X1+β2X2+…+β10X10.

[0015] Among them, p is the landslide susceptibility index, that is, the probability of landslide occurrence; ln(1-pp) is the logarithmic probability logit, that is, the logarithm of the probability ratio of landslide occurrence to non-occurrence; β0 is the intercept term; β1, β2,…, β10 are regression coefficients, corresponding to 10 influencing factors X1, X2,…, X10 respectively.

[0016] The landslide susceptibility index is obtained by taking the antilog of logit:

[0017]

[0018] Step S3, calculating the disaster resistance capacity of the transmission towers based on the target area transmission tower probabilistic earthquake demand model and the landslide susceptibility index.

[0019] According to the landslide disaster intensity I of the transmission towers in the target area and the disaster resistance R of the transmission towers, the vulnerability assessment model of the transmission towers is obtained:

[0020]

[0021] Among them, V represents the quantitative evaluation result of vulnerability, where 0 < V ≤ 1. The larger the value of V, the more vulnerable the transmission tower is. I = 1 indicates that the action intensity of the landslide disaster causes complete damage to the transmission tower, and R = 0 indicates that the disaster resistance ability R of the transmission tower cannot withstand the action of the disaster.

[0022] Further, in step S1, the limit state refers to selecting the top displacement of the tower as the performance index of the transmission tower structure. The seismic damage grades corresponding to the four performance levels of being affected under normal use, member yielding, structural yielding, and structural collapse are taken as the limit states, and the quantification indexes of these limit states are defined as u1, u2, u3, and u4. The corresponding seismic damage grades are divided into four levels: slight damage, moderate damage, severe damage, and near collapse.

[0023] The threshold u of the different limit states is obtained by calculating the limit values of the top displacement of the tower corresponding to the four-level limit states of being affected under normal use, member yielding, structural yielding, and structural collapse failure of the transmission tower, and u = ui, where 1 ≤ i ≤ 4;

[0024]

[0025] Among them, h is the height from the top surface of the longest leg foundation of the tower to the calculation point.

[0026] Further, in step S1, the linear regression analysis is carried out by performing incremental dynamic analysis on the structural finite element model using a set of ground motion records. The conditional standard deviation used to estimate the discreteness of the regression analysis is:

[0027]

[0028] where, d i represents the peak value of the i-th seismic demand in the linear regression analysis; N represents the total number of IDA analyses. Then the probabilistic seismic demand model of the transmission tower is:

[0029]

[0030] Among them, P(D ≥ u|IM) represents the probability between the ground motion intensity index IM and the structural seismic demand index D.

[0031] Further, in step S2, the 10 influencing factors X1, X2, …, X10 are respectively the elevation, slope, aspect, slope position, distance from the transmission tower, distance from the seismogenic fault, stratum, distance from the epicenter, seismic intensity, and PGA of the target area.

[0032] Furthermore, the landslide disaster intensity I is defined as a function of the landslide volume v and the expected landslide velocity s:

[0033] I=p×v 2 s 3 , s = 0.98 × v 0.274 ×Q 0.33 , v = 0.074 × A L 1.45

[0034] Among them, p is the landslide susceptibility index obtained by taking the antilog of logit, Q is the slope of the landslide body, and A L is the landslide area.

[0035] Furthermore, the resistance factors of the disaster resistance R of the transmission tower include: spatial characteristic resistance factor, self-structure resistance factor and earthquake impact resistance factor.

[0036] The spatial characteristic resistance factor is the position of the transmission tower line and the main sliding direction and the position of the transmission tower relative to the slope.

[0037] The resistance factor indicators of the self-structure include: structural materials of the tower, main materials of the tower, basic protection facilities, foundation depth-to-width ratio, tower material tightness, and tower corrosion degree parameters.

[0038] The earthquake impact resistance factor is: the probability P (D≥d|IM) between the earthquake intensity index IM and the structural earthquake demand index D.

[0039] The disaster resistance level of the transmission tower is determined based on various resistance factors:

[0040] R is the resistance of the transmission tower, ξ i is the total number of indicators n s ≥1, the value of the i-th resistance factor.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] 1. The present invention comprehensively considers the impact of two natural disasters, earthquake and landslide, on transmission towers. By establishing a probabilistic earthquake demand model and a landslide susceptibility index for transmission towers in the target area, the vulnerability of transmission towers in a complex natural environment can be more comprehensively and accurately evaluated. Advanced mathematical tools and methods such as log-normal distribution and binary logistic regression model are used to conduct in-depth analysis of earthquake intensity index, structural earthquake demand index and landslide influencing factors, and a scientific evaluation model is established. This evaluation method based on statistics and probability not only improves the accuracy of the evaluation results, but also makes the evaluation process more scientific and reasonable.

[0043] 2. The evaluation method proposed in the present invention has strong practicality and operability. By collecting and analyzing the data of natural disasters such as earthquakes and landslides in the target area and the structural characteristics of the transmission towers, the quantitative evaluation results of the vulnerability of the transmission towers can be easily calculated. The method of the present invention has extremely important practical significance and engineering practical value for the vulnerability analysis of the transmission towers under the action of earthquakes and landslides. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 The flowchart of the method for evaluating the vulnerability of power transmission towers taking into account the effects of earthquakes and landslides is provided in the present invention. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention is described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] like Figure 1 FIG. 1 is a flow chart of a method for evaluating the vulnerability of a transmission tower taking into account the effects of earthquakes and landslides according to the present invention. The method comprises the following steps:

[0047] Step S1, establishing a probabilistic seismic demand model for transmission towers in a target area based on a seismic intensity index and a structural seismic demand index.

[0048] Before performing step S1, it is necessary to collect historical earthquake records, design parameters and performance data of transmission towers in the target area. These data will provide a solid foundation for establishing a probabilistic earthquake demand model for transmission towers. For historical earthquake records, it is necessary to collect relevant information on all earthquakes that occurred in the target area in the past period of time, including magnitude, epicenter location, focal depth, etc. These data will be used to analyze the distribution and characteristics of the seismic intensity index (IM). Regarding the design parameters of transmission towers, it is necessary to obtain detailed design information of all transmission towers in the target area, such as the height, material type, structural form, etc. of the towers. The actual response and performance of the transmission towers in previous earthquake events are recorded and analyzed, including the displacement, stress, deformation and other data of the towers.

[0049] The target area transmission tower probabilistic seismic demand model is the probabilistic relationship between the seismic intensity index IM and the structural seismic demand index D, which is expressed in the form of log-normal distribution as follows:

[0050]

[0051] Where P(D≥u|IM) represents the probability between the earthquake intensity index IM and the structural seismic demand index D; Φ represents the standard normal cumulative distribution function; u represents the threshold value of different limit states; S D Represents the median value of the structural seismic demand index D; β D|IM represents the logarithmic standard deviation.

[0052] The median value S of the structural seismic demand index D D The relationship between the seismic intensity index IM is expressed in exponential form: S D =a×IM b .

[0053] Convert the exponential relationship to a logarithmic relationship and we get: ln(S D )=lbn(IM)+c, where b and c are the linear coefficient and constant term of linear regression analysis respectively, a is the constant term, and c=ln(a).

[0054] In step S1, the limit state refers to selecting the tower top displacement as the performance index of the transmission tower, and taking the earthquake damage levels corresponding to the four performance levels of normal use affected, component yielding, structural yielding and structural collapse as the limit state, and defining these limit state quantitative indicators as u1, u2, u3 and u4, and the corresponding earthquake damage levels are divided into 4 levels: slight damage, moderate damage, severe damage and near collapse.

[0055] The thresholds u of the different limit states are obtained by calculating the top displacement limit values ​​of the four limit states corresponding to the transmission tower being affected in normal use, component yielding, structural yielding and structural collapse failure, u=ui, 1≤i≤4;

[0056]

[0057] Where h is the height from the top surface of the longest leg foundation of the tower to the calculation point.

[0058] In step S1, the linear regression analysis is performed by using a set of ground motion records to perform incremental dynamic analysis on the structural finite element model, wherein the conditional standard deviation used to estimate the discreteness of the regression analysis is:

[0059]

[0060] Among them, d i represents the i-th earthquake demand peak in the linear regression analysis; N represents the total number of IDA analyses, and the transmission tower probabilistic earthquake demand model is:

[0061]

[0062] Among them, P(D≥u|IM) represents the probability between the earthquake intensity index IM and the structural seismic demand index D.

[0063] Step S2, according to the influencing factors of landslides caused by earthquakes in the target area, the landslide susceptibility index is calculated based on the binary logistic regression model.

[0064] The binary logistic regression model is: ln(1-pp)=β0+β1X1+β2X2+…+β10X10.

[0065] Among them, p is the landslide susceptibility index, that is, the probability of landslide occurrence; ln(1-pp) is the logarithmic probability logit, that is, the logarithm of the probability ratio of landslide occurrence to non-occurrence; β0 is the intercept term; β1, β2,…, β10 are regression coefficients, corresponding to 10 influencing factors X1, X2,…, X10 respectively.

[0066] The landslide susceptibility index is obtained by taking the antilog of logit:

[0067]

[0068] In step S2, the 10 influencing factors X1, X2, ..., X10 are respectively the elevation, slope, slope direction, slope position, distance from the transmission tower, distance from the seismogenic fault, stratum, distance from the epicenter, earthquake intensity and PGA of the target area. PGA (Peak Ground Acceleration) refers to the peak ground acceleration, which is the maximum absolute value of acceleration in the seismic record. PGA is an important parameter for measuring the intensity of seismic motion and is used to describe the maximum inertial force generated by an earthquake on the ground structure.

[0069] In practical applications, the data must first be preprocessed, such as standardization or normalization, to eliminate the impact of the dimension. Then, logistic regression analysis is performed using statistical software (such as R, SPSS, SAS, Python's statsmodels library, etc.) to obtain the intercept term and regression coefficient; finally, these coefficients are substituted into the above formula to calculate the probability of landslide occurrence at a given location under given earthquake conditions.

[0070] The landslide disaster intensity I is defined as the function of the landslide volume v and the expected landslide velocity s:

[0071] I=p×v 2 s 3 , s = 0.98 × v 0.274 ×Q 0.33 , v = 0.074 × A L 1.45

[0072] Among them, p is the susceptibility index of landslide occurrence obtained by taking the antilogarithm of logit, Q is the slope of the landslide slope, and A L is the area of the landslide body.

[0073] Step S3: Calculate the disaster resistance ability of the transmission towers based on the probabilistic seismic demand model of the transmission towers in the target area and the landslide susceptibility index.

[0074] Obtain the vulnerability evaluation model of the transmission towers according to the landslide disaster intensity I of the transmission towers in the target area and the disaster resistance ability R of the transmission towers:

[0075]

[0076] Among them, V represents the quantitative evaluation result of vulnerability, 0 < V ≤ 1. The larger the value of V, the more vulnerable the transmission tower is. I = 1 means that the action intensity of the landslide disaster causes complete damage to the transmission tower, and R = 0 means that the disaster resistance ability R of the transmission tower cannot withstand the action of the disaster.

[0077] The resistance factor indicators of the disaster resistance ability R of the transmission towers include: the spatial characteristic resistance factor, the resistance factor of its own structure, and the seismic influence resistance factor.

[0078] The spatial characteristic resistance factor is the position of the transmission tower line relative to the main landslide direction and the position of the transmission tower relative to the slope body.

[0079] The resistance factor of its own structure includes: the structural material of the tower, the main material of the tower, the foundation protection facilities, the foundation depth-width ratio, the fastening degree of the tower materials, and the corrosion degree parameter of the tower.

[0080] The seismic influence resistance factor is: the probability P(D≥d|IM) between the ground motion intensity index IM and the structural seismic demand index D.

[0081] Then determine the disaster resistance ability level of the transmission towers based on each resistance factor:

[0082] R is the resistance ability of the transmission tower, and ξ i is the value of the i-th resistance factor of a specific index in the case of the total number of indicators n s ≥ 1.

[0083] It should be noted that the spatial characteristic resistance factor mainly considers the positional relationship between the transmission tower line and the main sliding direction and the position of the transmission tower relative to the slope. The quantitative evaluation method of this factor: the angle θ is used to represent the angle between the transmission tower line and the main sliding direction. The smaller the angle, the weaker the resistance may be. The evaluation value is f(θ), where f is a decreasing function, indicating that it decreases as θ decreases. The position of the transmission tower relative to the slope is evaluated based on the distance d between the transmission tower and the top, bottom or potential landslide surface of the slope. The closer the distance, the weaker the resistance. The evaluation value is g(d), where g is a decreasing function, indicating that the evaluation value decreases as d decreases. The two sub-factors are combined to obtain a comprehensive spatial characteristic resistance factor, which is combined by weighted average or product, and this embodiment does not make specific limitations.

[0084] The resistance factor of the structure itself includes multiple parameters, such as the structural material of the tower, the main material of the tower, the foundation protection facilities, the foundation depth-to-width ratio, the tightness of the tower material, the degree of corrosion of the tower, etc. These parameters can be quantified through specific engineering standards or tests, and a weight is assigned to each sub-factor. The evaluation value of each sub-factor is multiplied by the corresponding weight and then summed up to obtain the comprehensive resistance factor of the structure itself.

[0085] The above equation can be used to estimate the disaster intensity of a single landslide in a certain area. The transmission lines passing through the area are often threatened by a series of landslides. The speed and volume of a single landslide can be estimated based on the above equation and divided into speed and volume ranges for scenario-based landslide intensity calculation.

[0086] The landslide intensity was estimated by taking into account the landslide velocity scale, ranging from very slow (5×10 -10 m / s) to very fast (5m / s); the landslide volume classes range from low (<1000m 3 ) to extremely high (>100000m 3 ), finally, the landslide intensity degree of different combinations of landslide velocity and volume can be expressed in the form of landslide intensity matrix.

[0087] The landslide intensity matrix is ​​a tool to represent the degree of landslide intensity under different combinations of landslide velocity and volume, where the rows represent different levels of landslide volume, the columns represent different levels of landslide velocity, and each cell represents the landslide intensity level under a specific volume and velocity combination.

[0088] Exemplarily, the landslide volume (v) can be divided into three levels (low, medium, and high), represented by 1, 2, and 3 respectively; the landslide speed (s) can also be divided into three levels (slow, medium, and fast), represented by 1, 2, and 3 respectively; the landslide intensity (I) can be represented by an integer from 1 to 9, where 1 represents the lowest intensity and 9 represents the highest intensity, then the landslide intensity matrix can be represented by a combination of numbers, and the specific matrix is ​​not limited in this embodiment. The actual landslide intensity matrix may vary according to the specific evaluation method and standard, and the specific value of the landslide intensity matrix needs to be determined based on detailed geological surveys, historical data analysis, and expert judgment.

[0089] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A vulnerability assessment method for transmission towers considering the impacts of earthquakes and landslides, characterized in that, the method comprises the following steps: Step S1, establish a probabilistic seismic demand model for transmission towers in the target area based on seismic ground motion intensity indices and structural seismic demand indices; The probabilistic seismic demand model for transmission towers in the target area is the probabilistic relationship between the seismic ground motion intensity index IM and the structural seismic demand index D, which is expressed in the form of a lognormal distribution as: Where P(D≥u|IM) represents the probability between the earthquake intensity index IM and the structural seismic demand index D; Φ represents the standard normal cumulative distribution function; u represents the threshold value of different limit states; S D Represents the median value of the structural seismic demand index D; β D|IM represents the logarithmic standard deviation; The median value S of the structural seismic demand index D D The relationship between the seismic intensity index IM is expressed in exponential form: S D =a×IM b ; Convert the exponential relationship to a logarithmic relationship and we get: ln(S D )=bln(IM)+c, where b and c are the linear coefficient and constant term of linear regression analysis, a is the constant term, and c=ln(a); The limit state refers to selecting the top displacement of the tower as the performance index of the transmission tower frame, taking the seismic damage grades corresponding to the four performance levels of being affected in normal use, member yielding, structural yielding, and structural collapse as the limit states, and defining the quantification indices of these limit states as u1, u2, u3, and u4, and the corresponding seismic damage grades are divided into four levels: slight damage, moderate damage, severe damage, and near collapse; The thresholds u of different limit states are obtained by calculating the limit values of the top displacements of the towers corresponding to the four limit states of being affected in normal use, member yielding, structural yielding, and structural collapse of the transmission tower, u = ui, 1 ≤ i ≤ 4; where h is the height from the top surface of the longest leg foundation of the tower to the calculation point; The linear regression analysis is to perform incremental dynamic analysis on the structural finite element model by using a set of seismic ground motion records, and the conditional standard deviation used to estimate the discreteness of the regression analysis is: Among them, d i represents the i-th earthquake demand peak in the linear regression analysis; N represents the total number of IDA analyses, and the transmission tower probabilistic earthquake demand model is: where P(D≥u|IM) represents the probability between the seismic ground motion intensity index IM and the structural seismic demand index D; Step S2, based on the influencing factors of landslides caused by earthquakes in the target area, calculate the landslide susceptibility index based on the binary Logistic regression model; The binary Logistic regression model is: ln(1 - pp) = β0 + β1X1 + β2X2 + … + β10X10; where p is the landslide susceptibility index, that is, the probability of landslide occurrence; ln(1 - pp) is the logit, that is, the logarithm of the ratio of the probability of landslide occurrence to non-occurrence; β0 is the intercept term; β1, β2, …, β10 are regression coefficients, corresponding to the 10 influencing factors X1, X2, …, X10 respectively; The 10 influencing factors X1, X2, …, X10 are respectively the elevation, slope, aspect, slope position, distance from the transmission tower, distance from the seismogenic fault, stratum, distance from the epicenter, seismic intensity, and PGA of the target area; The susceptibility index of landslide occurrence is obtained by taking the antilogarithm of the logit: Step S3, calculate the disaster resistance ability of the transmission tower based on the probabilistic seismic demand model of the transmission tower in the target area and the landslide susceptibility index; Obtain the vulnerability evaluation model of the transmission tower according to the landslide disaster-causing intensity I of the transmission tower in the target area and the disaster resistance ability R of the transmission tower; where V represents the quantitative evaluation result of vulnerability, 0 < V ≤ 1, and the larger the value of V, the more vulnerable the transmission tower is. I = 1 means that the action intensity of the landslide disaster causes complete damage to the transmission tower, and R = 0 means that the disaster resistance ability R of the transmission tower cannot withstand the action of the disaster; Define the landslide disaster-causing intensity I as a function of the landslide volume v and the expected landslide velocity s: I=p×v 2 s 3 ,s=0.98×v 0.274 ×Q 0.33 ,v=0.074×A L 1.45 Among them, p is the landslide susceptibility index obtained by taking the antilog of logit, Q is the slope of the landslide body, and A L is the landslide area.

2. According to the method for evaluating the vulnerability of transmission towers taking into account the effects of earthquakes and landslides as described in claim 1, It is characterized in that The resistance factor index of the disaster resistance capacity R of the transmission tower includes at least: spatial characteristic resistance factor, self-structure resistance factor and earthquake impact resistance factor; The spatial characteristic resistance factor is the position of the transmission tower line and the main sliding direction and the position of the transmission tower relative to the slope; The resistance factors of the self-structure include: structural materials of the tower, main materials of the tower, basic protection facilities, foundation depth-to-width ratio, tower material fastening degree, and tower corrosion degree parameters; The earthquake impact resistance factor is: the probability P (D≥d|IM) between the earthquake intensity index IM and the structural earthquake demand index D; The disaster resistance level of the transmission tower is determined based on various resistance factors: R is the resistance of the transmission tower, ξ i is the total number of indicators n s ≥1, the value of the i-th resistance factor.

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