JP2015090287A - Earthquake motion estimation method in consideration of earthquake response of railroad structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an earthquake motion estimation method in consideration of an earthquake response of a railroad structure, for evaluating an earthquake motion on the railroad structure, in consideration of an earthquake motion amplification effect.SOLUTION: In an earthquake motion estimation method in consideration of an earthquake response of a railroad structure, a parameter affecting a vibration characteristic of the railroad structure is extracted by utilizing observed fine motion, and the earthquake motion on the railroad structure is evaluated by multiplying together an earthquake response characteristic of the railroad structure determined from the parameter, a vibration characteristic of the ground, and an earthquake motion of the base.

Description

  The present invention relates to a method for estimating ground motion in consideration of the seismic response of a railway structure.

  The conventional seismic response of railway structures using the earthquake records of the surface did not take into account the seismic response of railway structures.

  In order to estimate damage to railway structures after an earthquake, it is necessary to accurately grasp the ground motion on the ground surface. On the other hand, in the main shock and aftershock of the 2011 off the Pacific coast of Tohoku Earthquake (Mw 9.0) that occurred on March 11, 2011, it was reported that a lot of breakage and inclination of the electrification pillars of the Shinkansen occurred due to shaking of the viaduct. (See Non-Patent Document 1 below). Therefore, in order to determine whether to stop or restart train operation after an earthquake, it is important to grasp not only the ground surface earthquake motion but also the earthquake motion on the railway structure.

Mitsunobu Mizuno and Shinichiro Nozawa, “Earthquake damage and restoration in JR East railway facilities”, Journal of Japan Society of Civil Engineers, Vol. 96, No. 7, 2011 Naoyata Iwata, Atsushi Tsuno, Shunroku Yamamoto, Shunta Noda, Akira Ito, Hiroyuki Miyakoshi, "S-wave velocity structure estimation in the central coastal area of Miyazaki Prefecture by surface wave exploration and array microtremor exploration", 127th Scientific Lecture Proceedings of the conference, lecture number 20, pp. 70-73, 2012 Naoyata Iwata, Atsushi Tsuno, Shunroku Yamamoto, Shunta Noda, Akira Ito, Hiroyuki Miyakoshi, “Simulation of S-wave velocity structure and seismic motion of linear continuation using H / V spectrum ratio” Proceedings of Lecture, Lecture No. 61, pp. 227-230, 2013 Nobuhiko Osaki, “Architecture Vibration Theory”, Shokokusha, pp. 44-51, 1996 Akihiko Nishimura, Shiro Tanamura, “Study on soundness judgment method of existing bridge piers”, Railway Research Institute report, Vol. 3, No. 8, 1989 Railway Technical Research Institute, “Railway structure design standards and explanation, earthquake-resistant design”, Maruzen Publishing, pp 356-361, 2012

  The conventional seismic response of railway structures using the earthquake records of the surface did not take into account the seismic response of railway structures.

  Therefore, in the present invention, in view of the above situation, a ground motion estimation method considering the seismic response of the railway structure is provided that evaluates the ground motion on the railway structure in consideration of the ground vibration characteristics and the vibration characteristics of the structure. The purpose is to do.

In order to achieve the above object, the present invention provides
[1] In the seismic motion estimation method considering the seismic response of the railway structure, parameters that affect the vibration characteristics of the railway structure are extracted using the observed microtremors, and the railway structure obtained from the parameters is extracted. The earthquake motion on the railway structure is evaluated by multiplying the earthquake response and the earthquake motion observed on the ground surface.

  [2] In the ground motion estimation method considering the seismic response of the railway structure according to [1] above, an observed transfer function and a one-mass system model based on microtremors simultaneously observed on the ground along the route and on the railway structure The natural frequency and the damping constant are identified so that the residual of the theoretical transfer function due to is minimized, the vibration characteristics of the railway structure are obtained, and then the calculated ground motion is input to the one-mass system model. The seismic motion on the railway structure is estimated along the route.

  [3] In the ground motion estimation method considering the seismic response of the railway structure according to [2], the railway structure is a viaduct.

  [4] In the ground motion estimation method considering the seismic response of the railway structure according to [3] above, the ground motion is multiplied by the amplification degree of the ground and the viaduct, and the ground motion on the structure is It is characterized by accurate estimation.

  According to the present invention, since the vibration characteristics on the railway structure are taken into consideration, it is possible to perform appropriate seismic operation regulation for the train traveling on the railway structure.

It is a figure which shows the model route which estimates the earthquake motion on a viaduct. It is a figure which shows the example of the Fourier spectrum ratio on a ground and a viaduct. It is a contour diagram of an observed transfer function for a kilometer of model routes. It is a figure which shows the amplification degree with respect to a frequency. It is a figure which shows the natural frequency calculated by identification with respect to the kilometer about a model route. It is a figure which shows the relationship between the pier height and the natural frequency calculated | required by identification. It is a figure which shows the attenuation constant calculated by identification with respect to the kilometer of a model route. It is a figure which shows the example of the waveform comparison of observation on the ramen viaduct of SiteB, and estimation. It is a figure which shows the comparison of the observed and estimated maximum velocity (cm / s) about the ground motion (N = 102) recorded on the viaduct of SiteB. It is a figure which shows the result of having estimated the seismic motion linearly with respect to the kilometer about a model route. It is a figure which shows the maximum speed (SiteA) of a ground surface earthquake motion and a structure response. It is a figure which shows the maximum speed (SiteB) of a ground surface earthquake motion and a structure response. It is a figure which shows the maximum velocity (SiteA) of underground ground motion and surface ground motion. It is a figure which shows the maximum velocity (SiteB) of underground ground motion and surface ground motion. It is a figure which shows the comparison of the maximum speed amplification degree of a ground and a structure.

  The seismic motion estimation method considering the seismic response of the railway structure according to the present invention extracts parameters affecting the vibration characteristics of the railway structure using the observed microtremors, and determines the railway structure obtained from the parameters. The seismic motion on the railway structure is evaluated by multiplying the seismic response characteristics, the ground motion characteristics, and the ground motion.

  Hereinafter, embodiments of the present invention will be described in detail.

  (1) First, high-density fine movement measurement along the model route will be described.

  FIG. 1 is a diagram showing model routes for estimating ground motion on a viaduct, FIG. 2 is a diagram showing an example of a Fourier spectral ratio (hereinafter referred to as an observation transfer function) on the ground and a viaduct, and a is a Fourier in a bridge axis direction. Spectral ratio, b indicates the Fourier spectral ratio in the direction perpendicular to the bridge axis. FIG. 3 is a contour diagram of the observed transfer function for the kilometer of the model route.

  As a model route for estimating seismic motion on the viaduct, the Miyazaki linear experiment was selected as shown in FIG. This route is about 7km long. Both ends of the start and end points are ramen viaducts, and between them are girder viaducts. Seismometers were installed on the ground and viaduct at the intermediate point (Site A) and terminal point (Site B) of this route, and seismic observation was conducted for about two years. In Non-Patent Document 2, the S-wave velocity structure at the two seismometer positions is estimated by surface wave exploration and array microtremor exploration.

  On the ground of this model route and on the viaduct, microtremor measurements were performed at intervals of about 0.1 km. Among these, the H / V spectral ratio of microtremor obtained on the ground is used for estimation of the S wave velocity structure along the route (see Non-Patent Document 3 above), and the Fourier spectral ratio on the ground and the viaduct (hereinafter referred to as “the S-wave velocity structure”). Observed transfer function) is used to identify vibration characteristics of viaducts. An example of the observed transfer function is shown in FIG. In addition, Fig. 3 shows the contour diagram of the observed transfer function (in the direction perpendicular to the bridge axis) for the model route. In the figure, gray sections represent sections c and d where data is missing or data is defective, and ◯ represents a peak frequency.

  (2) Next, identification of vibration characteristics of the viaduct on the model route will be described.

  FIG. 4 is a diagram showing the degree of amplification with respect to frequency, where e is an observed value and f is a theoretical value. FIG. 5 is a diagram showing the natural frequency calculated by identification with respect to the kilometer of the model route, where ■ indicates the direction of the bridge axis, and ● indicates the direction perpendicular to the bridge axis. Fig. 6 shows the relationship between the height of the pier and the natural frequency obtained by identification. ■ is the bridge axis direction of the girder viaduct, ● is the direction perpendicular to the bridge axis of the girder viaduct, and ▲ is the bridge axis direction of the ramen viaduct , ▼ indicate the direction perpendicular to the bridge axis of the ramen viaduct. FIG. 7 is a diagram showing the attenuation constant calculated by identification with respect to the kilometer of the model route.

For the observed transfer function, the viaduct is modeled as a one-mass system, and the inverse response is performed to match the theoretical response characteristics (hereinafter, the theoretical transfer function) (see Non-Patent Document 4 above), and the natural frequency and attenuation constant are identified went. Since the vibration characteristics of linear railway structures differ between the track direction and the direction perpendicular to the track, the vibration characteristics in the present invention were identified in each direction.
The grid search method was used for identification, and the target range was 0.5 to 1.5 times the first natural frequency of the observed transfer function. This range generally corresponds to a band having an observed transfer function of 1 or more (see FIG. 4). In addition, a search range is provided for efficient calculation of the solution, the natural frequency is -1 to + 1% of the peak frequency of the observed transfer function (search interval 0.01 Hz), and the attenuation constant is 0 to 20% (same as above). 0.1%). For the purpose of obtaining the peak frequency stably, the observation transfer function that determines the target range and the search range is subjected to smoothing processing. On the other hand, the observed transfer function for inverse analysis is not smoothed for the purpose of preserving the sharpness of the peak and estimating the attenuation constant well.
An example of identification results for the direction perpendicular to the bridge axis is shown in FIG. The thick solid line in the figure is the identification target band. From this figure, it can be confirmed that the vibration characteristics of the viaduct using the one-mass system model are generally well identified. According to FIG. 5, the natural frequency differs greatly depending on the point in both the bridge axis direction and the bridge axis perpendicular direction. A formula for calculating the natural frequency of the pier from the pier height and the girder weight has been proposed (see Non-Patent Document 5 above). According to FIG. 6, the natural frequency of the viaduct is the height of the pier for both the girder viaduct and the ramen viaduct. There was a strong correlation, and the identified natural frequencies were consistent with previous findings. In FIG. 7, the variation in the direction perpendicular to the bridge axis is small, and the distribution is approximately around 1%. On the other hand, although the bridge axis direction varies greatly depending on the location, most of them are in the range of 1% to 5%. Although the values obtained here are slightly smaller than 3% to 5% of the attenuation constant shown in the design standard (see Non-Patent Document 6 above), they are almost equal and a good value is identified.

  (3) Next, estimation of ground motion on the ground and viaduct will be explained.

  For the purpose of verifying the accuracy of ground motion estimation on the viaduct using a one-mass system model and identification parameters, the seismometer position was observed and estimated. Fig. 8 shows an example of the comparison of observed and estimated waveforms on the ramen viaduct of Site B (November 11, 2011, earthquake in Hyuga-nada, M3.5, seismic depth 34 km), g is the observed value, h is the observed value Represents an estimated value. FIG. 9 shows a comparison of observed and estimated maximum velocity (cm / s) for ground motion recorded on the Site B viaduct (N = 102). The observation and the estimation are in good agreement with both FIG. 8 and FIG. 9, and it is considered that the ground motion estimation method on the viaduct based on the one mass system model of the present invention has reliability.

  Next, the ground motion on the viaduct along the model route is estimated. Here, the earthquake in the Kumamoto region (M4.5, Dep. 10 km) that occurred at 23:33 on October 5, 2011 was targeted, and the ground motion on the ground surface was measured using the method described in Non-Patent Document 3 above. Estimated along the model route. The estimation of seismic motion on the viaduct uses the natural frequency and attenuation constant at each microtremor measurement point identified in (2) above. In the present invention, for simplicity, the interaction between the ground and the railway structure is not considered. For the target earthquake, FIG. 10 shows the estimated ground motion on the ground and the estimated ground motion on the viaduct. The evaluation target seismic motion index is the maximum speed of horizontal two-component synthesis. Here, with reference to the ground motion observed on the ground of Site A, the ground motion at the other microtremor measurement points and on the viaduct are estimated. Compared to the observation and estimation on SiteB viaduct, which is the position of the verification point, it is a little overestimated, but it is almost in good agreement, and the seismic motion can be estimated almost well over the entire model line. ing.

  Moreover, the comparison of the maximum speed of the ground surface earthquake motion and structure response in Site A and Site B is shown in FIGS. 11 and 12, respectively. Both sites have a high correlation coefficient (Cor in the figure), although there are variations in the amplification of viaducts due to earthquakes. A comparison of the maximum velocity of underground ground motion and surface ground motion in Site A and Site B is shown in FIGS. 13 and 14, respectively. The amplification level of the ground is also determined by a high correlation coefficient (Cor in the figure) at both sites, although there are variations in the amplification level due to earthquakes.

  Next, for the purpose of grasping the spatial fluctuation of the impact on the ground motion on the viaduct, the amplification factor of the ground (ratio of the maximum velocity between the base and the surface) and the amplification factor of the viaduct (on the surface and the viaduct) The ratio of the maximum speed, Vdc / Grd in the figure, is organized. FIG. 15 is a diagram showing a comparison of the amplification rate of the maximum speed of the ground (Grd / Bsm in the figure) and the structure (Vdc / Grd in the figure), and the amplification degree of the ground obtained from the velocity data of 15 earthquakes. And the degree of amplification of the viaduct, and the average of the degree of amplification considering both. The input ground motion of the base here is the same for all model lines. As shown in FIG. 15, the amplification degree of the ground is different at a boundary of about 5 km, and it is about 4.5 to 5 times for 5 km or less, and about 3.5 to 4 times for 5 km or more. The variation is small. On the other hand, the amplification degree of the viaduct is slightly smaller than the amplification degree of the ground, but varies greatly from point to point and is distributed about 1.5 to 5 times, and the variation is large. In order to accurately evaluate the ground motion on the viaduct on the model line, the amplification factor (Fig. 15, ▲) and the amplification factor of the viaduct (■, Fig. 15) are multiplied (Fig. It is important to evaluate (+) of 15.

  As described above, it is necessary to consider not only the ground surface earthquake motion but also the earthquake motion on the railway structure in order to judge the train operation regulation after the earthquake occurs.

  In addition, this invention is not limited to the said Example, Based on the meaning of this invention, a various deformation | transformation is possible and these are not excluded from the scope of the present invention.

  The seismic motion estimation method considering the seismic response of the railway structure according to the present invention is used as a seismic motion estimation method considering the seismic response of the railway structure, in which the seismic motion amplification effect is considered and the seismic motion on the railway structure is evaluated. Can do.

Claims (4)

  By using the observed microtremors, parameters that affect the vibration characteristics of the railway structure are extracted, and by multiplying the earthquake response of the railway structure obtained from the parameters and the earthquake motion observed on the ground surface, the railway Seismic motion estimation method considering seismic response of railway structures, characterized by evaluating seismic motion on structures.   2. A method for estimating ground motion in consideration of seismic response of a railway structure according to claim 1, wherein an observed transfer function based on microtremors simultaneously observed on the ground along the route and the railway structure and a theoretical transfer function based on a one-mass system model. The natural frequency and damping constant are identified so that the residual of the rail is minimized, the vibration characteristics of the railway structure are obtained, and then the calculated ground motion is input to the one-mass system model and A seismic motion estimation method in consideration of the seismic response of the railway structure, wherein the seismic motion on the railway structure is estimated along the rail.   3. The ground motion estimation method considering the seismic response of the railway structure according to claim 2, wherein the railroad structure is a viaduct.   4. The method for estimating ground motion according to claim 3 taking into account the seismic response of the railway structure, and using the ground motion on the base, multiplying the ground and the amplification degree of the viaduct to accurately estimate the ground motion on the structure. A ground motion estimation method considering the seismic response of railway structures.

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