Diagnosis and evaluation method for structures based on microtremors

Abstract

To provide a method for diagnosing and evaluating a structure based on the always fine movement of the structure, which is different from a conventional method in which soundness and safety of the structure is achieved by directly applying an external force or the like to an object, and earthquake resistance and soundness of the structure and the effect of a countermeasure work and a reinforcing work can be inexpensively and quickly diagnosed and evaluated.SOLUTION: Disclosed is a method for evaluating performance of a structure by the always fine observation, which includes the steps of: constantly observing a fine observation history at the same time at a plurality of observation points in the structure; calculating an estimated value of an index used for an earthquake resistant design of the structure using the root mean square (RMS) of these time histories; and performing evaluation of the earthquake resisting performance based on the observation of the structure using a ratio to a value of the index used at a point of time when this value is designed.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a technique for a method of diagnosing and evaluating a structure, which diagnoses and evaluates the earthquake resistance and soundness of the structure, as well as the effects of countermeasures and reinforcement works, based on the microtremors of the structure. [Background technology]

[0002] Diagnosing and evaluating the performance of various objects around us, from the human body, machines, and buildings to cliffs, the ground, and trees, is fundamental to living a safe and comfortable life, and many devices and technologies are already in practical use. Among these, diagnosing and evaluating the earthquake resistance and soundness of structures such as buildings and infrastructure facilities poses the following difficulties: They are exposed to various natural environmental conditions over long periods of time. Each one has a different shape and material. Destructive testing is not possible. Their size exceeds the human scale. They are difficult to move. They cannot be completely described in documents or data. Structures are supported by the ground, and the properties of the ground are more complex than man-made objects visible on the ground. There is a high degree of uncertainty regarding the timing, scale, and vibration characteristics of sudden external forces such as earthquakes.

[0003] Furthermore, the traditional method for evaluating the earthquake resistance of existing buildings has been to calculate the structural earthquake resistance index (Is value), but this requires experts to make judgments based on information such as blueprints, input it into a computer program, and perform complex calculations, which takes a lot of time and money. Furthermore, the calculation method was not unique and involved input based on branching and judgment, which ultimately led to the systematization of a third-party assessment committee. In other words, the above conventional method required a lot of money, effort, and time.

[0004] The diagnostic evaluation methods for the entire structure that have been put into practical use so far include a) checking the consistency with drawings and calculations, b) redoing structural calculations, c) redoing calculations using a different calculation method, d) measuring the shaking by applying vibrations using a vibrator or the like, e) scoring and tallying up results in the form of a checklist, and f) based on microtremor observation. Inspections at the time of new construction fall into the category of a) or b), while seismic diagnosis falls into the category of c). However, the methods using calculations listed in a) to c) pick up the numerical values ​​that are the basis for the method from drawings, etc., so it is assumed whether the actual structure and support conditions are as they are. In addition, even if detailed calculations are performed for the inside of the structure and a 100% accurate judgment can be made, the calculation results will be largely dependent on the conditions of the foundation and the surrounding ground. In addition, the method using a vibrator listed in d) is also difficult to say that it is a highly accurate judgment, just like the case of structural calculations, because the energy of the vibrator is too small compared to the potential energy of the structure and the surrounding ground.

[0005] Microtremors contain information about structures and the surrounding ground that is far more comprehensive, detailed, and voluminous than the information on which the above methods are based. Although the amplitude of microtremors is small, at only a few microns, they carry a great deal of energy because the huge mass of the structure and surrounding ground is constantly vibrating. Spatially, the structure and surrounding ground vibrate at every point, and the amount of information is far greater than that obtained from design documents or vibration exciters. In particular, when assessing the risk of a major earthquake, it is important to be able to measure actual vibrations with the input source being the ground, just like an earthquake.

[0006] Several attempts have been made to diagnose structures using microtremors, such as the technology disclosed in Patent Document 1. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 3876247 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the conventional techniques were methods of visually determining the period that was considered to be dominant from the Fourier spectrum and discussing the changes, and only extracted a small part of the abundant information contained in microtremors. Therefore, the diagnostic results were insufficient in both accuracy and content, and could not establish a position as a diagnostic method for structures. In addition, the conventional techniques including Patent Document 1 could not be applied to evaluation or diagnosis within the framework of the current standards because the calculated indexes were not indexes used in the current design standards or seismic diagnostic standards. Furthermore, the design indexes in the current standards do not directly evaluate the continued use of a structure. However, the current seismic design standards and seismic diagnostic standards for structures are collectively referred to as the current standards in this specification. In addition, the seismic diagnostic standards are simply referred to as diagnostic standards, and the seismic design standards are simply referred to as design standards.

[0009] In addition, there was no way to actually measure the story shear force distribution coefficient in the height direction, horizontal bearing capacity, and the product of cumulative strength index and shape index used in seismic diagnosis, which are currently used in earthquake-resistant designs. The current standards do not specify expected earthquake motions, and there is also the problem that the current calculation method is not unique and involves inputs that are based on branching and judgment.

[0010] In view of the above problems found in the prior art including Patent Document 1, the present invention aims to provide a new method for extracting information on an actual structure and surrounding ground system and using it for designing, diagnosing and evaluating the structure by directly obtaining estimated values ​​of the indexes and damage level from microtremor measurements, by relating information from microtremors to the expected values ​​of cumulative strength index and structural seismic index used in the diagnosis and seismic retrofit design of existing structures, the expected value of the distribution coefficient of story shear force in the height direction used in the current design of new buildings, and the damage level for directly evaluating the continued use of the structure. The method of the present invention is called Micro Tremor Diagnosis (MTD). [Means for solving the problem]

[0011] The present invention has been made to solve the above-mentioned problems, and its structural feature is that in a method for evaluating the performance of a structure through continuous microtremor observation, the microtremor time history is observed simultaneously at multiple observation points within the structure, and the root mean square (RMS) of these time histories is used to calculate an estimate of an index to be used in the seismic design of the structure, and the seismic performance of the structure is evaluated based on the observations using the ratio of this value to the value of the index used at the time of design.

[0012] In addition, the continuously measured microtremor time history can be divided, a plurality of partial time histories can be extracted, the expected value of the index can be calculated for each partial time history, and the sample average can be used as the estimated value of the index. In this case, the duration of the partial time history is preferably 1 to 2 minutes.

[0013] In the present invention, the observations may be carried out after the construction of a structure, before and after renovation work, and at the time of periodic inspections, and the estimated values ​​at each observation time may be compared with each other to diagnose and evaluate at least any of the changes over time in the seismic performance of the structure, the risk of collapse in a major earthquake, and the continuity of use, and the changes before and after renovation work.

[0014] In the present invention, the index may be the distribution coefficient of the story shear force in the height direction defined in the current standards, or the horizontal bearing capacity defined in the current standards.

[0015] In the present invention, the index is the base shear coefficient defined in the current standard or the It may also be a specified acceleration response magnification.

[0016] Furthermore, in the present invention, the index may be the product of the cumulative strength index and the shape index defined in the current standard, or the damage level or the risk of falling that are newly defined in the present invention. Effect of the Invention

[0017] According to this invention, the expected values ​​of the cumulative strength index and structural seismic index used in the diagnosis and seismic retrofit design of existing structures, the expected value of the height-wise distribution coefficient of story shear force used in the current designs of new buildings, and a newly defined estimated value of damage level to directly evaluate the continued use of a structure can be obtained directly from the measured microtremor values. By observing each part of a structure using a vertical array, it is possible to measure the vibration properties, strength, damage level, etc. of each floor part (zone), making it possible to evaluate the seismic resistance, soundness, and effect of retrofit design in much more detail, more quickly, and more cheaply than with conventional methods.

[0018] In other words, according to the present invention, by using the above-mentioned indicators, diagnostic evaluation or inspection can be performed much more quickly and cheaply than with current diagnostic evaluation or inspection methods after new construction, after renovation work, and during periodic inspections, thereby enabling rational seismic reinforcement design and seismic design of newly constructed structures. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is an explanatory diagram showing an example of the configuration of a diagnostic system to which the method of the present invention is applied; [Diagram 2] FIG. 1 is a flowchart showing a basic processing procedure performed between a micromotion sensor and an analyzer. [Diagram 3] FIG. 2 is an explanatory diagram showing factors necessary for calculating the structural seismic index, horizontal bearing capacity and damage level in the method of the present invention. [Figure 4] FIG. 2 is a flowchart showing the overall processing procedure of the method of the present invention. [Diagram 5] FIG. 2 is an explanatory diagram showing the processing contents performed in the analyzer by routine. [Figure 6] Schematic diagrams showing the action and seismic force of an actual earthquake, where (a) shows the actual action, (b) shows the spring-mass system, and (c) shows the seismic force. [Figure 7] A model (single mass system) diagram that combines the multiple masses and springs depicted in Figure 6(b) with black dots and lines. [Figure 8] A graph showing the bilinear relationship between cumulative strength index and story drift angle. [Figure 9] A graph showing the relationship between friction-type interlayer shear force and support part acceleration. [Figure 10] A graph showing the relationship between friction-type interlayer shear force and interlayer velocity. [Figure 11] A graph showing the relationship between friction-type inter-story shear force and inter-story displacement. [Figure 12] An example of the layout of four types of microtremor sensors on the first floor of a four-story hospital. [Figure 13] The layout of four types of microtremor sensors on the second floor of the four-story hospital is shown as an example. [Figure 14] The layout of four types of microtremor sensors on the third floor of the same four-story hospital is shown as an example. [Figure 15] The layout of four types of microtremor sensors on the fourth floor of the same four-story hospital is shown as an example. [Figure 16] Y Hospital 1st floor column wall and 2nd floor floor beam plan. [Figure 17] Y Hospital 2nd floor column wall and 3rd floor floor beam plan. [Figure 18] Y Hospital X direction single frame diagram. [Figure 19] Y Hospital X direction 2-way frame diagram. [Figure 20] Y Hospital X direction 4-way frame diagram. [Figure 21] Y Hospital Y direction A-through frame diagram. [Figure 22] Y Hospital Y direction B axis frame diagram. [Diagram 23] FIG. 11 is a full view of the building according to the second embodiment. [Figure 24] The installation status of the A2 measuring instrument on the first floor in Figure 23 corresponds to Figure 25. [Diagram 25] FIG. 25 is an explanatory diagram showing the arrangement of measuring instruments and the reinforcement positions corresponding to FIG. 24 . [Figure 26] Microtremor displacement trajectories for each floor. [Figure 27] Animation of vibrations measured on the roof of an 11-story SRC building before reinforcement. [Figure 28]Animation of vibrations on the roof of an 11-story SRC building measured after reinforcement. Displacement data (XYZ three components) from microtremor sensors installed in three locations on the roof surface after reinforcement was input into structural analysis result visualization software, and a moment of visualization (animation) was shown. [Figure 29] A schematic diagram showing the relative positions of a block wall, foundation, ground, and microtremor meter. [Diagram 30] An explanatory diagram showing the overall view of a block wall in different situations (a) to (c). [Diagram 31] Diagram of micromotion gauge placement on block wall and reference point. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The ground around structures is constantly vibrating minutely. The sources of vibration energy are tides, traffic vibrations, etc. The amplitude is a few microns [10 = -6 Microtremors (hereafter simply referred to as "microtremors") observed at a certain point on a structure are the result of microtremors in the surrounding ground entering the structure through the foundation and being amplified or attenuated as they propagate through the structure.

[0021] Microtremors are observed by microtremor meters (accelerometers) installed inside a structure. This is the absolute acceleration at a specific point inside the structure, and is usually measured separately in three orthogonal components: the vertical component and the horizontal component. Since the amplitude is small and the duration is short, the structure is a stationary linear system, and the microtremors can be mathematically treated as part of a stationary stochastic process.

[0022] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is an explanatory diagram showing an example of the configuration of a diagnostic system to which the method of the present invention is applied. According to the drawing, the entire diagnostic system is composed of a microtremor meter 1 arranged at the layer boundaries 10a, 10b, and 10c of each layer of a structure 10, and an analyzer (e.g., a personal computer) 2 that calculates various vibration characteristic indexes, various seismic resistance evaluation indexes used in the current standards, and new evaluation indexes based on the data recorded by the microtremor meter 1.

[0023] Among these, the microtremor meter (for example, the microtremor meter JU410 manufactured by Hakusan Kogyo) 1 has an acceleration sensor, memory, and GPS built in. The analyzer 2 is equipped with microtremor diagnostic software, which receives data recorded by the microtremor meter 1 via USB, LAN, or the Internet, performs calculations according to the method of the present invention described in detail below, and calculates various vibration characteristic indexes, various seismic resistance evaluation indexes used in the current standards, and new evaluation indexes. The microtremor displacement data acquired by the microtremor meter 1 installed in, for example, three places on a certain story is sent to visualization software installed in the analyzer 2, and the movement of the surface is animated in three dimensions and displayed on a display means (display) (not shown) equipped in the analyzer 2, so that how the structure 10 is vibrating and the vibration mode are displayed and visualized so that it can be clearly confirmed visually at a glance.

[0024] The outline of the method of the present invention will be described below with reference to Figs. 2 to 5. Fig. 2 is a flow chart showing the basic processing procedure performed between the microtremor meter 1 and the analyzer 2. According to the figure, the vibrometer 1 measures and records the continuous microtremors (acceleration time history of the observation point and the reference point on the story boundary). The analyzer 2 filters the received measurement record data in the frequency domain and then obtains the acceleration time history of the frequency band near the natural frequency of the target structure. After obtaining the acceleration time history, it is divided into parts of about 2 minutes in the time domain, and the time history of interest, the energy transfer rate, and various indices are calculated for each part. After the calculation, the average value and standard deviation of the vibration characteristic index, the seismic performance index, and the seismic absorption performance index for each part are calculated, and the average value is used as an estimate of each index.

[0025] In addition, according to FIG. 3, the magnitude of the earthquake motion assumed in the method of the present invention is the maximum acceleration, the maximum velocity, and the maximum The performance of the target story of the target structure is expressed in terms of required horizontal bearing capacity, ductility index, age index, and maximum number of repeated earthquakes. After the installation of the microtremor meters is completed, microtremor measurements are performed using the microtremor meter 1 and the measurement results are analyzed using the analyzer 2 according to the processing procedure shown in Figure 2, and vibration characteristic indexes (central period, coefficients showing distribution of story shear force in the height direction), seismic performance evaluation indexes (horizontal bearing capacity, product of ultimate cumulative strength index and shape index), and seismic absorption evaluation indexes (hysteretic absorbed energy, damage level). After the above processing, the structural seismic index, horizontal bearing capacity ratio, and damage level are calculated to finish the processing.

[0026] FIG. 4 is a flow chart showing the overall processing procedure of the method of the present invention. According to the figure, first, a preliminary survey of the target structure is conducted. Specifically, document materials such as design drawings, calculations, expansion and reconstruction history, damage history, and past seismic resistance diagnosis are collected, and a possible location for installing a microtremor meter is determined by a site survey. Next, the measurement time period, measurement time, placement of the microtremor meter (instrument), and reference plane are determined as a microtremor measurement plan. After the microtremor measurement plan is formulated, the absolute time of the instrument is adjusted, microtremor measurement is performed, and data is recorded, and the analysis is performed by calculating the time history of interest, vibration characteristic index, and performance index. After the above is completed, the diagnosis is performed. In this case, the structural seismic resistance index or horizontal bearing capacity ratio is used for diagnosis in accordance with the current standards, and the damage degree is used for seismic performance evaluation.

[0027] Fig. 5 is an explanatory diagram showing the processing contents by routine performed in the analyzer 2. According to the diagram, the input data includes each data as the expected earthquake motion specifications, as well as the observed microtremor time history, observation time, observation frequency band, analysis time, and analysis frequency band, as well as each data as the observation point attributes and each data as the structure specifications.

[0028] The calculation routine performs calculation of the time history of the microtremor of interest, part division, calculation of the vibration characteristic index, and calculation of the performance index. The preliminary calculation routine performs FFT, filtering, zero point correction, calculation of the mean square value, calculation of the central frequency, and calculation of the bandwidth index.

[0029] The display routine displays input data, observed time history, spectrum, central frequency, bandwidth index, vibration characteristic index, and performance index, as well as time history, power spectrum, trajectory, and surface motion animation. The output / transfer routine is performed via paper, hard device, USB, LAN, radio waves, etc.

[0030] The method of the present invention has been outlined above based on Figures 1 to 5, but will be described in more detail below. The method of the present invention (MTD: Micro Tremor Diagnosis) quantitatively analyzes the vibration characteristics of microtremors and structures using the root mean square (RMS) of the duration, displacement, velocity, and acceleration time history of the microtremors, peak factor, zero crossing period, central period, and bandwidth index, as well as the energy transfer rate between the microtremor displacement, velocity, and acceleration time history of a reference point and the microtremor time history of interest. This involves grasping the characteristics of the stochastic process using the second moment and analyzing the correlation between input and output.

[0031] In microtremor measurements, several sets of time histories are extracted from the continuous measurement duration for one microtremor sensor arrangement, and the following quantities are calculated for each set to obtain the sample mean and standard deviation. For seismic resistance evaluation, the sample mean of each quantity is used as an estimate of the expected value of each quantity.

[0032] Figure 6 is a schematic diagram showing the action and seismic force of an actual earthquake, where (a) shows the actual action, (b) shows the spring and mass point gauge, and (c) shows the seismic force. Microtremor diagnosis is calculated by modeling the structure-ground system as shown in Figures 6(a) to (c), with the surrounding ground 21 as a rigid bed and the structure 10 as mass points and springs. This is the same as the current earthquake resistance standards.

[0033] The ground is constantly being affected by tides, traffic vibrations, etc., and is constantly changing in size by several microns [10 -6 Vibrations occur with minute amplitudes of about [m]. This is called micro tremor. The same is true for the surrounding ground 21 of the structure 10, represented by a solid-line rectangle in Figure 6(a). The micro tremors enter the structure 10 from the foundation and propagate inside the structure 10, so the structure 10 also generates micro tremors constantly. Because it is subjected to random inputs for a sufficiently long period of time, it is believed that both the surrounding ground 21 and the structure 10 are vibrating in their own natural vibration mode.

[0034] By installing multiple microtremor sensors (accelerometers) 1 inside a structure 10 as shown in Figure 1, it is possible to observe the time history of microtremors. For example, as shown in Figure 6(b), one sensor is installed in a vertical array at the representative point of each layer, so that each layer of the structure 10 is modeled as a mass point and a spring. Because the amplitude of microtremors is minute, the structure 10 is a stationary linear system over a finite duration, and constant microtremors can be mathematically treated as part of a stationary stochastic process.

[0035] Seismic motion is a phenomenon in which displacement due to the destruction of bedrock and ground in the epicenter becomes waves that reach the ground around structures and cause them to vibrate. Therefore, the source of vibration energy is different from that of microtremors. However, in the small amplitude range, both the surrounding ground and structures are thought to vibrate in their natural modes, so the vibrations are thought to be the same as those of microtremors. Based on the above, the following indices are calculated through microtremor observations, the dynamic properties of the structure and its behavior during an earthquake are predicted, and the current seismic performance evaluation indexes and new evaluation indexes are calculated.

[0036] 1. Central period (vibration characteristic index 1) The central period T of microseismic displacement in a certain direction at a certain point in a structure c [sec] is calculated as follows:

[0037]

number

[0038]

number

[0039] However, ω cy [rad / sec] is the RMS of the time history obtained by differentiating the time history of any microtremor. The central frequency is calculated by dividing the frequency by its own RMS. (The "central" here is the Japanese translation of the English "central frequency" and does not mean that it is located at the center of something in particular. It is the expected value of the zero cross frequency and means the frequency that plays a central role in discussing the frequency characteristics of the time history in the theory of random vibration.) a (see column a in Table 1) and b (see column b in Table 1) are the displacement times, respectively. and RMS of the velocity time history.

[0040] [Table 1]

[0041]

number

[0042] Here, [0,t0] is the duration of the microtremor time history. Similarly, the central period can be defined for each of the above. By calculating the central period of the time history obtained from multiple microtremor sensors installed in a certain part of a structure and comparing them with each other, it is possible to determine whether that part is vibrating in its inherent vibration mode.

[0043] 2. Expected value of coefficient expressing distribution of story shear force in the height direction (Vibration characteristic index No. 2) The current earthquake resistance and earthquake diagnosis standards for buildings are based on the mechanical model shown in Figure 6(b). , the earthquake force acting on the jth story of the building (P j ) to the seismic intensity (k j) and its layer weight (w j )

[0044]

number

[0045] From the above relationship, when an n-story building is subjected to an earthquake and vibrates, the maximum shear force occurring in the i-th story is called the story shear force a (see column a in Table 2), and the weight supported by that story b (see column b in Table 2) and the earthquake story shear force coefficient (C i ) is given as a product of

[0046] [Table 2]

[0047]

number

[0048] In addition, the seismic layer shear coefficient (C i ) with the area coefficient (Z) and vibration characteristic coefficient (R t ), standard shear coefficient (C0) and coefficient expressing the distribution of story shear force in the height direction (A i ) is specified as the product of C0=0.2 for the primary design assuming small to medium earthquakes, and C0=2 for large earthquakes. In the next design, it has been decided that C0 = 1.0 will be used.

[0049]

number

[0050] Regarding the first layer,

[0051]

number

[0052] From the above, Ai is calculated by normalizing the story shear force to the first story shear force a (see column a in Table 3). The weight of the layer above that layer is standardized by the total weight (W) of the layer above the first layer and α i It can be derived that the ratio is:

[0053] [Table 3]

[0054]

number

[0055] Using the above relationship, we assume that the absolute acceleration energy transfer rate a (see column a in Table 4) in the k direction of the i-th story obtained by the microtremor diagnosis is preserved even during elastic response due to earthquake motion input. We multiply this by the maximum acceleration of the reference point to calculate the expected value b of the maximum absolute acceleration (see column b in Table 4), and then multiply this by the mass m of each story of the structure. j From the above, the expected value c of the maximum story shear force (see column c in Table 4) is calculated, and the expected value E[A ik ] of It can be obtained (Equation 9). However, the maximum acceleration of the reference point is not shown because it is in the denominator and numerator of the rightmost side of Equation 9 and is reduced. Also, the absolute acceleration energy transmissibility a (see column a in Table 4) is the energy transmissibility defined in paragraph "0067" of this specification, where the microtremor time history of interest is taken as the absolute acceleration time history, that is, the ratio of the RMS of the absolute acceleration time history in the k direction of the i-th story to the RMS of the absolute acceleration time history in the k direction of the 1st story. Also, the second equal sign from the right in Equation 9 is derived from the equation of motion for the mechanical model of the structure in FIG. 6(b) (see paragraphs "0032" to "0034"). The final equal sign in Equation 9 is based on the assumption stated in paragraph "0021", that is, that the absolute acceleration time history of each story (i-th story) obtained by microtremor observation can be mathematically treated as a part of a stationary stochastic process, and based on the knowledge that the expected value of the maximum value within a certain duration can be calculated by multiplying the RMS by the peak factor, the peak factors of the absolute acceleration time history of each story are set to be equal to each other. As shown above, the method of the present invention estimates the design index of the current standard defined using the maximum value of the force acting on the structure during an earthquake based on the above assumptions, using the RMS of the absolute acceleration time history of each story obtained by microtremor observation. This method obtains an estimate of the maximum value with less variation (stable) than the method using the actually measured maximum value, i.e., an estimate of the design index.

[0056] [Table 4]

[0057]

number

[0058] Incidentally, in the earthquake resistance standards, based on various analyses and considerations, α appearing in the above two formulas is as follows: i (standardized weight), and the first natural period T of the building are used as parameters. i It stipulates:

[0059]

number

[0060]

number

[0061] However, T [sec] is the value for λ, where the majority of the columns and beams of the building are made of wood or steel. The ratio to the total height of the floors (excluding the basement) h [m] is calculated using the following formula: It is being done.

[0062]

number

[0063] The above regulations were devised to express the maximum response shear force distribution of each floor of a tower-like structure, from low-rise to super-high-rise, in one formula. i Instead of calculating A, we directly create a model of each building in Fig. 6(b) and calculate the maximum value of the story shear force by using a time history response analysis method or the like. i It is also permissible to ask for

[0064] 3. Expected value of average transmissibility and response magnification (Vibration characteristic index 3) When considering the action of an earthquake on the i-th layer in the model of Figure 6(b), it is convenient to use the following indices, which give the RMS or maximum value of the average acceleration, average velocity, etc. of the part b (from the i-th layer to the n-th layer) supported by that layer.

[0065]

number

[0066]

number

[0067] where m j is the mass of the jth layer, a (see column a in Table 5), and b (see column b in Table 5) are the energy transfer rates of acceleration and velocity in the k-direction of the jth layer, respectively, and B aik is the average acceleration energy transfer rate, B vik is called the average velocity energy transfer rate. Here, the energy transfer rate is the ratio of the RMS of the microtremor time history of interest to the microtremor time history of the reference point. In microtremor diagnosis, this is assumed to be preserved at the time of the maximum elastic response due to earthquake motion input, and the peak factor is appropriately set. Assuming appropriate, the maximum response of the time history of interest is calculated by multiplying the maximum input value at the reference point by the energy transfer rate.

[0068] [Table 5]

[0069] For example, using the above average acceleration energy transfer rate, the absolute acceleration time history a of each point (mass dM) of part b supported by a certain story i in a structure is k The spatial average value of (t) in the k direction A k The expected value of RMS of (t) E[σ Ak ] can be calculated as follows depending on the a of the acceleration time history of the reference point (see Table 6):

[0070] [Table 6]

[0071]

number

[0072]

number

[0073] Expected value A of the coefficient expressing the distribution of story shear force in the height direction in Equation 9imk and is defined in Equation 13. Average acceleration energy transfer rate B aik There is the following relationship between:

[0074]

number

[0075] That is, A imk is the average acceleration of the part supported by the focus part i and the part supported by the first layer. It can be said that this is the ratio of the average acceleration (of the entire structure). In Equation 13, the average acceleration transmissibility B when j=1 aik is the ratio of the average absolute acceleration of the structure, a (see column a in Table 7), to the absolute acceleration of the reference point, b (see column b in Table 7), that is, the acceleration response magnification R when the entire structure is reduced to a single degree of freedom system as shown in Figure 7. amk is the expected value.

[0076] [Table 7]

[0077]

number

[0078] Similarly, B with j=1 in Equation 14 v1k can be said to be the expected value of the velocity response magnification when the entire structure is reduced to a single degree of freedom system.

[0079]

number

[0080] The current standard standard shear coefficient in Equation 6 is C0=0 for the primary design assuming small to medium earthquakes. .2 In the secondary design for large earthquakes, C0 = 1.0 is used because This is because the maximum acceleration of vibration is considered to be 0.07G to 0.08G for small to medium earthquakes and 0.33 to 0.4G for large earthquakes, and the acceleration response magnification of short-period buildings is considered to be 2.5 to 3.

[0081] 4. Expected horizontal strength (earthquake resistance performance index 1) In the earthquake resistance standard, each story of the structural model of the building is i The distributed shear force is gradually increased and the story shear force a (see column a in Table 8) acting on the i-th story when the i-th story yields is defined as the available horizontal strength b (see column b in Table 8). The relationship between the story shear force generated in the structure due to the ground motion and the acceleration at the reference point is the average acceleration transmissibility (B aik ) by In addition, the relationship between the story displacement and the acceleration at the reference point can be expressed using the transmissibility defined in paragraph "0067" of this specification. Using these, it is possible to calculate the expected story shear force when the maximum story displacement of the i-th story reaches the yield displacement when the structure responds linearly. This can be considered as the expected horizontal bearing capacity c (see column c in Table 8) on the assumption that stories other than the i-th story will not yield. Acceleration d in the k direction of the reference point (see column d in Table 8) versus story drift in the k direction of the i-th story (e ik The energy transfer rate e (see column e in Table 8) of the two components (t) is defined as the ratio of their RMS values ​​as follows:

[0082] [Table 8]

[0083]

number

[0084] Maximum story drift e ikmax is the yield displacement e ikY The maximum acceleration of the reference point when it reaches a ikY So,

[0085]

number

[0086] The expected value a of the maximum value of the story shear force at this time (see column a in Table 9) is calculated by multiplying the mass b of the part b supported by the i-th story (see column b in Table 9) by the expected value A of the maximum value of the average acceleration of this part. bkmax It can be calculated by multiplying

[0087] [Table 9]

[0088]

number

[0089] The expected value of the maximum acceleration of the reference point and the maximum value of the average acceleration of the above part b is the average acceleration energy transfer rate B aik are related using

[0090]

number

[0091] From the above,

[0092]

number

[0093] From formula 21 and formula 24,

[0094]

number

[0095] Expected value of story shear coefficient when ultimate horizontal strength is reached C uikmThe relationship in Equation 5 is This is obtained by dividing the above formula by the weight that the layer supports.

[0096]

number

[0097] However, the height of the i-th floor in the k direction is H 0ik [m], yield deformation angle is R Yik [rad], g[m / sec 2 ] is the gravitational acceleration. The expected value of the first story shear coefficient when the horizontal bearing capacity is reached, that is, the expected value of the base shear coefficient, C ui1km From the relationship of Equation 8, the above equation is A i This can be calculated by dividing the acceleration response magnification R by Equation 9, Equation 17, and Equation 19. amk It can be seen that this can be expressed as the energy transfer rate a of the inter-story displacement relative to the acceleration at the reference point (see Table 10).

[0098] [Table 10]

[0099]

number

[0100] The horizontal load-bearing capacity ratio is calculated by dividing the expected horizontal load-bearing capacity obtained above by the required horizontal load-bearing capacity specified by the earthquake resistance standards.

[0101] 5. Expected value of the product of ultimate cumulative strength index and shape index and structural seismic index (seismic performance index part 2) The seismic assessment standard is to determine the structural seismic index I for each beam and girder direction (horizontal two directions) of each floor (each story) of a low- to mid-rise RC building. s The basic performance index E0 and the shape index S D , and the aging index T.

[0102]

number

[0103] Regarding the basic performance index E0 in the above formula, a detailed formula is prescribed to calculate it by aggregating the product of the strength index (C) and ductility index (F) of each direction of each column, wall, and beam of each story. However, in principle, the basic performance index E0 is the product of the strength index and ductility index of that story (E0 = The toughness index of a layer is the toughness index corresponding to the inter-layer deformation at which the layer reaches its ultimate limit, so this is called F U and accordingly, the coefficient equivalent to the base shear coefficient at the story drift angle at which the story reaches its ultimate limit (ultimate cumulative strength index) is expressed as C TU This is expressed as:

[0104]

number

[0105] From the above relationship,

[0106]

number

[0107] Equation 29 is derived by assuming that the story shear force a (see column a in Table 11) is bilinear with respect to the story displacement e, as shown by the line segment OYU in Figure 8. In this case, the story shear force (cumulative strength index) at the yield point Y and the ultimate point U are equal (C TY =C TU ), yield correlation displacement (e Y ) is the cumulative strength index for the story shear force a (see column a in Table 11). However, Figure 8 shows the relationship between the weight Σw that the story supports and the distribution coefficient A of the story shear force in the height direction. i Divide by the cumulative strength index C T The story drift e is divided by the story height H0 to obtain the story drift angle R. Note that the subscript i is omitted.

[0108] [Table 11]

[0109] The relationship between story displacement and story shear force obtained by microtremor diagnosis is assumed to represent the relationship shown in Figure 8, although it is close to the origin of the relationship. U When the I of a layer reaches its ultimate state against the earthquake motion assumed in the code (designated earthquake motion: G0), the I of the layer is S The value is set to 0.6. Therefore, the correlation displacement energy transfer rate h egi Multiplying by the reference point displacement corresponding to the design basis earthquake motion (G0) gives the expected value of the correlation displacement (E[e G0 ] ) is calculated as , yield displacement (e Y =R Y H0), the value is 0.6. 0 for F U If =1,T=1, then

[0110]

number

[0111] Since it is assumed that the cumulative strength index and the story drift angle (story displacement) are proportional, the ultimate cumulative strength index in the k direction of the i-th story multiplied by the shape index ((C TU S D ) ik The expected value of Correlation displacement energy transfer rate h obtained by dynamic diagnosis egik corresponds to the standard earthquake motion (G0) Reference point displacement x G0

[1978] to obtain the correlation displacement (e G0ik ) and calculate the yield displacement (e Yik ) and multiplying it by 0.6.

[0112]

number

[0113] Now, according to the earthquake resistance assessment criteria, s The value of 0.6 is the I value for buildings that sustained moderate or greater damage in the 1968 Tokachi-oki earthquake and the 1978 Miyagi-ken offshore earthquake. s Estimated distribution of earthquake damage and I for buildings that have not experienced earthquake damage s The validity of the criteria was verified by comparing the distribution of values. In addition, studies on the 1978 Izu Oshima earthquake, the 1987 Chiba Prefecture East Coast earthquake, and the 2011 Great East Japan Earthquake are also published, but the maximum acceleration, velocity, duration, etc. of observed earthquake motions up until the 1978 Miyagi Prefecture Offshore Earthquake are on a completely different order of magnitude from those observed in the 21st century, as represented by the 2011 Great East Japan Earthquake, so the earthquake motion assumed by the diagnostic criteria should be considered to be the earthquake motion up until 1978, when the criteria were first established.

[0114] The National Oceanic and Atmospheric Administration (NOAA) has compiled a database of records of strong earthquakes observed in Japan up until 1978 and made it public. Based on the results of statistical analysis of these records, it is considered appropriate to expect a maximum displacement of approximately 2.5 cm in both horizontal directions at that time, and this is substituted into Equation 32. In addition, the yield displacement e in the k direction of the i-th layer in the same equation is Y [m] to floor height H0 [m] and yield deformation angle R Y The formula for calculating the expectation value of the product of the ultimate cumulative strength index and the shape index from the energy transfer rate is obtained, expressed in [rad].

[0115]

number

[0116] From Formula 30 and the above formula, the structural seismic index I s can be calculated from microtremor diagnosis.

[0117]

number

[0118] However, I sm is the structural seismic index obtained from microtremor diagnosis, F U , and T are the ultimate toughness index and the aging index.

[0119] 6. Hysteretic energy absorption (seismic performance index 1) Nonlinear response calculations, i.e., calculations of how a structure will deform and move in response to an earthquake after a certain layer of the structure has reached its yield strength, i.e., after it has become nonlinear with respect to stress, from the information contained in or planned to be contained in the design documents, are not easy even if the seismic motion is specified and the structure and ground are simplified as in Figure 6(b) or Figure 7.

[0120] A wide variety of models (constitutive laws) have been devised for the stress and strain that act between each layer of a structure after yielding. Concrete and soil exhibit nonlinearity even with very small strains. Furthermore, variables that explain nonlinearity include not only inter-story displacement as shown in Figure 8, but also its relative velocity, absolute acceleration, and even stress and strain in other directions such as axial force. The components that make up a layer, the materials that make them up, and the connection conditions of each component are diverse, and there are also many ways to reduce them to a single constitutive law. It is difficult to say which is the correct answer.

[0121] In earthquake-resistant design, there are several representative nonlinear models that are used to analyze experimental results at the component level or full-scale models. However, even if the load application method and displacement measurement method of the experimental equipment are compatible, it is not possible to verify their effectiveness in the action of an actual earthquake in three-dimensional space.

[0122] Figure 9 shows the relationship between friction-type inter-story shear force and support part acceleration, Figure 10 shows the relationship between friction-type inter-story shear force and inter-story velocity, and Figure 11 shows the relationship between friction-type inter-story shear force and inter-story displacement. The diagnosis allows us to measure the vibrations at representative points of each story of the actual structure and quantify the response characteristics of each story with respect to the structural model in Fig. 6(b). From the results, we can calculate the expected value of hysteretic energy absorption using a friction model such as those shown in Figs. 9 to 11.

[0123] This model is a stress model for a structure in which stones are stacked on top of each other, and as shown in Figures 9 and 10, when the absolute acceleration of the part supporting the layers exceeds the critical acceleration and a relative velocity occurs between the layers, a constant shear force acts in the opposite direction to that velocity.

[0124] Starting from zero story displacement, the story displacement increases in a certain direction until it reaches a certain magnitude, at which point the structure deforms so that the story displacement continues to decrease, and once it has decreased to a certain magnitude, the structure deforms so that it then increases. If we plot the relationship with the story displacement, we get the result shown in Figure 11. For the bilinear shear force-story displacement relationship shown in Figure 8, if we plot the relationship between the story shear force and the acceleration of the supporting parts, we get Figure 9. Therefore, the above frictional model can be applied to the part of the bilinear shear force-story displacement relationship where the shear force is constant (line segment YU in Figure 8).

[0125] The hysteretic absorbed energy W of the i-th layer calculated from the k-direction component ik is the relative movement of the top surface of the i-th story of the structure with respect to the bottom surface (inter-story displacement e ik ) is the work done by the restoring force (story shear force) a (see column a in Table 12) W ik and is obtained by integrating the increment (see column b of Table 12) over the duration of the vibration, t0.

[0126] [Table 12]

[0127]

number

[0128] The spatial average absolute acceleration and mass in the k direction of the part supported by the i-th layer are respectively expressed as A ik If we define them as (t) and (Σm), the equation of motion in the k direction of the part supported by the part of interest is as follows:

[0129]

number

[0130] Since the restoring force is assumed to have the yield limit strength a (see Table 13), from Equation 36, A ik It can be seen that (t) also has a limit value, and this is called the limit acceleration A cik Let us assume that.

[0131] [Table 13]

[0132]

number

[0133] Microtremor observations allow us to predict the spatial average acceleration of the part supported by the i-th story when the structure responds elastically, i.e., when the restoring force does not have a limit value, and this is designated as a (see Table 14).

[0134] [Table 14]

[0135] The hysteretic absorbed energy W per unit mass when the restoring force is of friction type and the bottom surface of the layer vibrates with acceleration a (see Table 14), where a (see Table 14) is part of a stationary Gaussian process with duration s0. ik The expected value of each parameter obtained from the power spectral density function of a (see Table 14) and the critical acceleration A ci The theoretical equation expressed as follows has been obtained from random vibration theory.

[0136]

number

[0137] Where: E[*]: Expected value of * [operator]

[0138] In addition, for the k direction of the i-th layer a (see Table 15): Restoring force [N] e ik (t): Relative displacement of the upper and lower surfaces [m] A cik :Limit acceleration [m / sec 2 ] Σw: Supported weight [N]

[0139] [Table 15]

[0140] In addition, the spatially averaged elastic response acceleration time history a of the part supported by the i-th story during an earthquake (see Table 14) and the k-direction component of the velocity time history integrated from this are as follows: s0: Strong earthquake duration [sec] T vik : Central period of velocity time history [sec] σ aik : RMS of acceleration time history [m / sec 2 ] α vik : Bandwidth exponent of velocity time history [dimensionless] σ vik :RMS of velocity time history [m / sec]

[0141] Here, the duration of a strong earthquake, s0, is the duration for treating the time history (x(t)) of duration t0, which is non-stationary like earthquake motion, as part of the duration s0 of a stationary Gaussian process (G(t)) that has the same power spectral density function, so that the maximum value of x(t) appears as a maximum value on average once during the duration s0 of G(t).

[0142] Above T vikThe following parameters are calculated from the time history and energy transfer rate obtained from microtremor observations and the predicted maximum value of the vibration time history of the reference point due to the assumed earthquake. First, we assume that the structure will vibrate in the vibration mode obtained from the microtremor observations during the elastic response even during an earthquake, and calculate the vibration period T vik , bandwidth exponent α vik is calculated using the micro-tremor acceleration time history b (see column b in Table 16) of the bottom surface of the part supported by the i-th layer, i.e., the top surface of the i-th layer. Furthermore, the RMS σ vik and the RMS σ of this velocity time history vik Regarding is calculated using the average transmissibility of each layer (j=i...n) (see paragraphs "0059" to "0075" of this specification) and the RMS of the reference point during the earthquake.

[0143] [Table 16]

[0144]

number

[0145]

number

[0146] The RMS of the acceleration and velocity during an earthquake at the reference point is calculated using the peak factor to obtain the expected maximum velocity V maxk and the expected maximum acceleration A maxk can be rewritten as a relationship between

[0147]

number

[0148]

number

[0149] Furthermore, the ultimate acceleration in the k direction of the i-th story is calculated by using the fact that the horizontal bearing strength a (see column a of Table 17) obtained in paragraphs "0081" to "0100" of this specification is equal to the yield story shear strength (a (see column b of Table 17)). From Formula 37 and Formula 25,

[0150] [Table 17]

[0151]

number

[0152] From the above, the expected value of the hysteretic absorbed energy of the i-th layer due to a large earthquake calculated from the k-direction component, W mik [Nm] can be calculated as follows:

[0153]

number

[0154] where the yield displacement e ikY is expressed as the product of the yield deformation angle and the story height. Regarding the direction, R Yik : Yield deformation angle [dimensionless] H 0ik :Standard floor height [m] a (see Table 18): Inter-story displacement energy transfer rate for reference point acceleration [dimensionless]

[0155] [Table 18]

[0156] In addition, regarding the k-direction component of the microtremor time history on the upper surface of the target area, T vik : Central period of micromotion velocity time history [sec] α vik : Bandwidth exponent of microtremor velocity time history [dimensionless] Here, the bandwidth index is the central frequency of that time history divided by the central frequency of the differential time history, and the bandwidth index of the microtremor velocity time history is the ratio of the central frequency of the microtremor velocity time history to the central frequency of the microtremor acceleration time history.

[0157] In addition, regarding the part supported by the layer, Σm: Mass [kg] B aik : Average acceleration transmissibility (see formula 13) [dimensionless] B vik : Average speed transmission ratio (see formula 14) [dimensionless]

[0158] Furthermore, with regard to the k-direction component of the large earthquake motion at the reference point, the following parameters determine the magnitude and nature of the input and are given by the designer's judgment or standards. s0: Strong earthquake duration [sec] V maxk :Maximum speed [m / sec] A maxk :Maximum acceleration [m / sec 2 ] Gamma v : Peak factor of velocity time history [dimensionless] Gamma a : Peak factor of acceleration time history [dimensionless]

[0159] In addition, both sides of the above equation are divided by Σm / 2 to obtain the velocity conversion value V of the expected value of hysteretic absorbed energy per unit mass supported. mik Get [m / sec].

[0160]

number

[0161] 7. Damage level (seismic performance index 2) The degree of damage to a certain layer of a structure due to the action of an earthquake is assumed to be proportional to the hysteretic absorbed energy, and the ratio of this to the limit value is called the damage degree (I d ) and can be used as a design guideline.

[0162]

number

[0163] where for the ith layer in the k direction: I dik :Damage degree [dimensionless] W mik : Expected value of hysteretic absorbed energy [Nm 2 / sec 2 ] W lik : Limit value of hysteretic absorbed energy [Nm 2 / sec 2 ]

[0164] Limit value of hysteretic energy absorption W lik can be calculated by assuming the restoring force of each member or group of members to be a bilinear type as shown in Figure 8 and accumulating each limit value.

[0165]

number

[0166] However, the limit value is the energy absorbed in one repetition, which is twice the area of ​​the projection of the line segment OYU on the horizontal axis in Figure 8, and this n kj where, for each member or member group j in the k-th layer, we use: n kj : Limit number of repetitions [dimensionless] q kj :Strength [N] F jk :Toughness index [dimensionless] e Yj : Yield displacement [m] R Yik : Yield deformation angle [rad] H 0ik :Floor height [m]

[0167] The expected value of the yield story shear strength (horizontal strength) in the k direction of the i-th story is calculated in paragraphs "0081" to "0100" of this specification, so if the story toughness index and the limit number of cycles are given, The limit value of the hysteretic energy absorption can be calculated by using the formula 47, which treats the entire layer as one group, and the formula 25.

[0168]

number

[0169] However, for the i-th layer in the k-direction N ik : Limit number of repetitions [dimensionless] a (see column a in Table 17): expected value of yield shear strength (horizontal strength) [N] F uik : Toughness index [dimensionless] Σm: Mass of the supported part [kg]

[0170] The damage level is calculated as the quotient of the expected value of the hysteretic absorbed energy in Equation 44 and the limit value in Equation 48 as follows:

[0171]

number

[0172] Damage degree I dik is the average acceleration transmissibility B of the part that supports the vibration characteristics obtained from microtremor observation of the ground system around the structure in the k direction of the i-th layer. aik , average velocity transmission rate T vik , and the inter-story displacement energy transfer coefficient a in the k direction of the i-th story for the reference point acceleration (see Table 20), and the central period T of the velocity time history vik , and the bandwidth exponent α vik The input earthquake motion characteristics are expressed as the strong earthquake duration s0 and maximum velocity V maxk and maximum acceleration A maxk and the respective peak factors γ v , γ a In addition, as a structural parameter, the yield deformation angle RYik , and standard floor height H 0ik The recovery performance is measured using the toughness index F uik and the limit number of iterations N ik It is expressed as:

[0173] 8. Seismic assessment standards, current standards, and earthquake motion levels in line with recent earthquake environments In microtremor diagnosis (MTD2017), the vibration amplification characteristics of a structure are quantified as a sample average of the energy transmissibility from the observed microtremor time history. In addition, the vibration mode is visualized and the natural period and bandwidth are measured. In earthquake resistance evaluation, the vibration caused by a large earthquake at reference points set on the first floor, basement, etc. of the structure is used as input, the maximum elastic response is estimated from the energy transmissibility, and the expected value of the structural seismic index is calculated. In addition, the historical absorbed energy is estimated from the predicted values ​​of the average acceleration and velocity of the part supported by the target layer or part, and the damage level is calculated. The setting of the earthquake motion level required for the above is at the discretion of each designer, but it is effective to convert the expected levels of the current standards, etc. into microtremor diagnosis input values ​​and display them.

[0174] Table 19 shows the diagnostic criteria, the standard earthquake motion levels (maximum acceleration, velocity, expected displacement (Amax, Vmax, Dmax) and strong earthquake duration) that are considered to be assumed by the current criteria. The expected value (S0) of the seismic activity is shown. At the bottom, the seismic activity levels from recent observed seismic activity are shown for reference. As mentioned above, the diagnostic criteria are estimated from seismic activity observed in Japan up until 1978. The current criteria are estimated from the opinions of those involved in the establishment of the criteria and the shape of the notification spectrum (2015 edition of the Structural Technical Standards for Buildings Commentary, pp. 488-490, published by the National Official Gazette Sales Cooperative). The recent observed seismic activity is estimated from the strong earthquake observation records of the 2011 Tohoku Pacific Coast Earthquake and the 2016 Kumamoto Earthquake, but no statistical processing has been performed. In addition, the earthquake motion level in recent earthquake environments is an order of magnitude higher than the current standard level, and it is meaningless to use it as the input earthquake motion for the current standard framework and the framework for microtremor diagnosis, which are based on maximum elastic response. Seismic design for earthquake motion of this level must be carried out using a method fundamentally different from that of the current law.

[0175] [Table 19]

[0176] Positioning of Micromotion Diagnosis In rational seismic design, microtremor diagnosis plays the following roles:

[0177] (1) Post-completion inspection and additional countermeasures After the structure is completed, a microtremor diagnosis is carried out to determine the vibration mode and vibration period (T c ), story shear force distribution coefficient (A im ), response ratio (R amk , R vmk ), cumulative strength index a (see Table 20), damage degree (I dm ) are measured and compared with design calculations to confirm the validity of the calculations and construction, and additional countermeasures are added if necessary. The above indexes are calculated for the entire structure, and vertical array measurements are installed in specific areas to determine the vibration characteristics of those areas.

[0178] [Table 20]

[0179] (2) Regular health checks and repairs Conduct regular microtremor diagnosis and measure the above-mentioned indexes. Repairs will be carried out if deterioration of the structure is found. After repairs, conduct microtremor diagnosis again to confirm the effect of the repairs.

[0180] (3) Diagnosis and seismic reinforcement of existing structures We carry out microtremor diagnosis for existing structures built under current or old earthquake resistance standards, and design and construct countermeasures as necessary. We also carry out measurements and diagnosis before and after reinforcement to quantitatively confirm the effectiveness of the reinforcement.

[0181] (4) Analysis of the relationship between earthquake damage and vibration characteristics of the ground and structures Using an example where a building that has undergone microtremor diagnosis is damaged by an earthquake, the relationship between the degree of damage and the diagnosis index will be analyzed, leading to revisions to future design methods, diagnosis methods, and standard values ​​for each index. EXAMPLES

[0182] 1) Target facilities and measurement methods Completed in 1972, it has one basement floor, four floors above ground, and a total floor space of 838 m 2 The first floor 12 to the fourth floor 15 of a reinforced concrete hospital building 11 (one span in the X direction, three spans in the Y direction) (the fourth floor is steel, tentatively named Y Hospital) are as shown in Figures 12 to 15, and the results of a microtremor diagnosis carried out on this reinforced concrete hospital building 11 are presented here. A seismic diagnosis was carried out in April 2014, and a reinforcement plan was drawn up to achieve a value of over 0.6, but it was determined that construction work could not be carried out while the hospital was in operation, and so "axial strength reinforcement" was carried out to reinforce the main columns with the SRF method (a wrapping method using polyester fiber belts: see paragraph "0194" of this specification) in order to prevent collapse.

[0183] Microtremor observations were carried out using four microtremor meters 21 in four different arrangements as shown in Figures 12 to 15. In the first (measurement 1) and second (measurement 2), they were installed in a vertical array at one location each on A2 Street and A4 Street on each floor from the first to fourth floors. In measurement 3, they were installed at a point on A4 Street on the first floor and at points A2, A4, and B1 on the second floor. In measurement 4, they were installed at a point on A4 Street on the first floor and at points A2, A4, and B1 on the third floor.

[0184] The measurements took approximately two hours, and consisted of installing the instruments, taking continuous measurements for five minutes, rearranging the instruments, and then taking measurements with four different instrument arrangements and then removing them. Before the reinforcement work was carried out, the measurements were carried out while the hospital was in operation, between 3pm and 6pm on August 8th, 2017. After the reinforcement work was carried out, the measurements were carried out between 2pm and 4pm on September 22nd, 2017. The reinforcement work was scheduled to run from July 20th to September 30th, 2017, but as of August 8th, only preparations were being carried out and no construction had taken place. Furthermore, as of September 22nd, the structural work had been completed, with only minor finishing touches remaining.

[0185] For the microtremor diagnosis, the time history of the total record length of 5 minutes observed at each point was divided into 5 to 7 sections of approximately 1 minute each, with some overlapping, and the indices for each section were calculated, and the average value and standard deviation were calculated for each measurement. These average values ​​are shown in the tables shown after Table 21. The above measurements were taken before (before reinforcement) and after (after reinforcement) the reinforcement work was carried out using the SRF method, to see the impact of the reinforcement.

[0186] The microtremor meter observed the acceleration time history, and after using a 10 Hz high-cut filter and a 0.2 Hz low-cut filter (4th-order Butterworth), the velocity and displacement were obtained by numerical integration using the linear acceleration method. Figures 16 to 22 show the floor plan and frame plan of the target building. An expansion joint is installed in 4' street. Seismic assessments were conducted separately for 1 to 4' streets and the rest. The assessment results cited in this specification are for 1 to 4' streets.

[0187] 2) Performance indicators Table 21 shows the expected value of the cumulative strength index (C T S D ) mik The values ​​of C before and after reinforcement were calculated from the seismic diagnostic calculation. TU S D Measurement 1 shows the vertical array of A2, and measurement 2 shows the vertical array of A4. Table 22 shows the rate of change before and after reinforcement and the comparison with the calculated value. Tables 23 and 24 show the standardized input energy W obtained by microtremor diagnosis before and after reinforcement.Komik and the calculated value W Koik The change rate before and after reinforcement and the calculation are compared. In addition, Tables 25 and 26 show the expected value of the damage degree (I d0m ) before and after reinforcement and calculated values ​​(I d ) and a comparison with calculations before and after reinforcement is shown. The value in parentheses is the value taking into account the second-class structural element. The damage degree is calculated by calculating the limit value of hysteretic absorbed energy from the strength and toughness of the member group obtained in the seismic diagnosis calculation using Formula 47, and calculating the hysteretic absorbed energy using an approximate formula (see paragraph "0199" in this specification). Furthermore, in the calculation of this example, when determining the limit acceleration used in the calculation of hysteretic absorbed energy (see paragraph "0149" in this specification), the product of the cumulative strength index and the shape index (see Formula 32) is used instead of the horizontal bearing capacity.

[0188] [Table 21]

[0189] [Table 22]

[0190] [Table 23]

[0191] [Table 24]

[0192] [Table 25]

[0193] [Table 26]

[0194] The reinforcement work was carried out using a method (SRF method) in which high-ductility polyester fiber material (belts) was wrapped around the main columns of each floor from the first to the third floor to ensure shear strength and axial strength. The reinforcement design was designed so that the test ratio of all columns was greater than 1.0. The maximum test ratio of the axial force during an earthquake on each floor was set as the collapse risk value (I f The I value is used as a design index for reinforcement to prevent collapse. f In the calculation, the axial strength of the column is the remaining axial strength at the time of large deformation (F>3.0), so for RC columns, it is zero before reinforcement, Collapse risk level I f is infinite.

[0195] Looking at the diagnostic calculations on the right side of Table 21 before and after reinforcement, the cumulative strength index C TU S D This is because slits were cut in the wall with columns or the column with sleeve walls and the columns were wrapped around them. However, after the reinforcement, C TU S D Before reinforcement, The strength and toughness of the reinforced members are reflected in the fracture results, and the grouping is repeated to calculate the approximate value. D The decrease in strength index due to reinforcement work is the result of the reinforcement design aiming to secure axial strength and prevent collapse even if the strength is reduced slightly, assuming that there is a margin of strength in the Y direction. Also, as shown in Tables 25 and 26, the reinforcement work has reduced the damage level I d was significantly reduced to about 20-30% of the level before reinforcement, and after reinforcement, it was below the standard value of 1.0 for all floors and directions, indicating that the reinforcement work had brought the damage within the allowable limits.

[0196] Cumulative strength index C according to diagnostic calculations shown in Tables 21 and 22 TU S D and the expected value of the cumulative intensity index obtained by the microtremor diagnosis (C T S D ) mikLet's compare the values ​​before and after reinforcement. For measurement 2, the microtremor diagnosis value for the third floor is about 40% lower, but the values ​​are almost the same for the other floors and directions. On the other hand, for measurement 1, the values ​​for the first floor are almost the same, but the microtremor diagnosis results for the second and third floors are significantly smaller, at about 20% of the diagnosis calculation. This is thought to reflect the structural characteristics around the measurement locations, as follows. As shown in the frame diagram in Figure 17, the X direction of measurement 1 (2-way) is a frame with almost no walls. Also, the opening of the wall in the adjacent 1-way is large, and there is no wall in the 3-way. On the other hand, the X direction of measurement 2 (4-way) is a frame with almost no walls, and the same is true for the adjacent 4' frame. For measurement 1 (2-way, A-way), the Y direction has no walls or a large opening. On the other hand, for measurement 2 (4-way, A-way), the Y direction has an opening but a wall. This is also reflected in the shape index of the seismic diagnosis. That is, the shape index S shown on the right side of Table 21 D The value of 0.63 is small on the 2nd and 3rd floors in the X direction. As a result of the uneven distribution of the walls in the X direction, the story displacement in both the X and Y directions is large near the 2nd floor.

[0197] Looking at the rate of change before and after reinforcement in Table 22, in measurement 1 (around 2 letters), (C T S D ) mik The improvement was almost uniform, about 20%. This can be said to be the result of column reinforcement using the SRF method shown in Figures 16 to 22, which improved the vibration characteristics of the X-direction frames 1 to 3 at the center of the column and the Y-direction A-frame near the second frame, reducing the inter-story displacement for the standard earthquake motion. On the other hand, in measurement 2, there was almost no change before and after reinforcement, or (C T S D ) mik However, looking at the absolute values ​​in Table 21, in measurement 2, after reinforcement, the values ​​are consistent, at around 0.5 to 0.6 for the 1st and 2nd floors and around 0.2 for the 3rd floor, in both the X and Y directions. Similarly, in measurement 1, the values ​​are consistent, at around 0.6 for the 1st floor and around 0.2 for the 2nd and 3rd floors. We believe that the above is a result of reinforcing the main columns with the SRF method, resulting in stable vibration characteristics.

[0198] Comparing the magnitude of the values ​​obtained by diagnostic calculations and microtremor measurements shown in Table 22, on the first floor with little eccentricity, the calculations and measurements were nearly the same for both Measurements 1 and 2. This shows that the settings of the expected maximum ground surface displacement due to earthquake motion assumed in the microtremor diagnostic method and seismic resistance diagnosis (see paragraphs "0113" to "0114" of this specification) were appropriate in this example. Also, on the second and third floors with eccentricity, measurements 1 and 2 measured values ​​that were significantly different, showing that detailed structural characteristics can be ascertained by vertical array observations.

[0199] Standardized input energy W shown in Table 23 K0ik and the allowable limit value W l0ik The standardized hysteretic absorbed energy (hereinafter referred to as standardized input energy) W shown on page 112 of the 2015 edition of the SRF method design and construction guidelines and commentary published by the Structural Quality Assurance Institute. E In the simplified formula, the effect of earthquake motion and structures on input energy is calculated using a uniform coefficient m E = 5.0, the input energy does not change before and after reinforcement. On the other hand, as shown in Equation 49 in this specification, the input energy changes before and after reinforcement because it is a formula that reflects the effects of the strength of the structure, the response magnification, and the vibration bandwidth. However, in Table 23, W in the Midori Book E A i The value is multiplied by and displayed as a value normalized only by the supporting mass.

[0200] As for the absolute value of the standardized input energy, in the X direction of measurement 1 before reinforcement, which is greatly affected by eccentricity, the measured value is about 4 to 7 times larger than the calculated value, but the rest are almost the same. Therefore, this example shows that the microtremor diagnostic method and the set values ​​of the earthquake motion levels equivalent to the current standards shown in Table 19 are appropriate in terms of the degree of damage.

[0201] Looking at the rate of change in standardized input energy before and after reinforcement shown in Tables 23 and 24, for measurement 1, which is heavily affected by eccentricity, it has uniformly decreased to about 60%. On the other hand, for measurement 2, there is a large decrease in the X direction on the 1st and 2nd floors, but on the 3rd floor, there is an increase in both directions. In particular, the rate of increase in the Y direction for measurement 2 is large, at about 7 times. These directly relate to the change in strength (C T S D ) mik This reflects the change in the value of the cumulative strength index. In other words, in this example, the cumulative strength index is used in the calculation of the critical acceleration of the standardized input energy, so the result reflects the increase or decrease in this strength. However, although the rate of increase in the Y direction is large, the absolute value itself is not large compared to the allowable value.

[0202] Let's take a look at the damage levels shown in Tables 44 and 45. Calculations show that before reinforcement, the damage exceeded the standard value of 1.0 in the X direction, but after reinforcement it fell below the standard value in both the X and Y directions (damage below the allowable value). According to the microtremor diagnosis, it is below the standard value, except for the X direction of measurement 1, which is affected by eccentricity. The Y direction on the 3rd floor of measurement 2 was 1.16, which can be considered to be close to the standard value.

[0203] From the above, if this building were to encounter a major earthquake as assumed by the current standards, it is possible that vibrations in the X direction would cause damage in the two areas that would exceed the allowable limit, but it is highly likely that damage in other areas would be within the allowable limit. Although this cannot be determined by microtremor diagnosis, the collapse risk level I shown in Table 44 f Since after reinforcement, the value is below the standard value of 1.0, it is believed that the building will be able to avoid collapse even if it experiences earthquake motion that significantly exceeds the current standard.

[0204] 3) Coefficient A expressing the distribution of story shear force in the height direction i Table 27 shows the coefficient A, which represents the distribution of story shear force in the height direction. i The expected value of (A imk ) before and after reinforcement is calculated by using Equation 9, the absolute acceleration energy transfer rate a obtained by microtremor observation (see Table 4) and the mass m of each story of the structure. jThe values ​​calculated from the formula are compared with the values ​​obtained from the current standard formula (Formula 10), and Table 29 shows the rate of change before and after reinforcement and the ratio of the calculated values ​​to the measured values.

[0205] [Table 46]

[0206] [Table 47]

[0207] [Table 48]

[0208] Let's take a look at the actual measurements before and after reinforcement. In measurement 1, there was a maximum change of only about 2% on each floor and in each direction. In measurement 2, there was a 10% to 20% increase on the third floor, but on the second floor the change was less than 5%. Looking at the ratio of calculations to actual measurements, on the second floor, they are almost the same regardless of the measurement point or whether reinforcement was present. Meanwhile, on the third floor, before reinforcement, the actual measurements were about 10% smaller than the calculations for both measurements 1 and 2, but after reinforcement, in measurement 2, the actual measurements and calculations matched, or were about 10% larger in the Y direction.

[0209] Looking at the absolute values ​​of the above figures, the actual measurements and calculations are almost identical. This shows that the microtremor measurement method used to measure the coefficient representing the distribution of story shear force in the height direction measured a uniform distribution of seismic intensity, which is considered to be the maximum response story shear force distribution for low-rise buildings under current standards. Also, a comparison of the changes before and after reinforcement on the third floor and with calculations suggests that the reinforcement work has had the effect of correcting the strength of the third floor, which was particularly high, by cutting slits, bringing it closer to that of the second floor and below.

[0210] For the Y direction on the 3rd floor of measurement 2, the actual A i (A imk) is much larger than the calculation, which indicates that the slits have been cut, resulting in a structure that increases the vibration of this part. This is the actual measured value of the strength index (C T S D ) mik The decrease in the standardized input energy W shown in Table 23 (0.60 → 0.20) K0ik (5.4→37.9), and the damage level I shown in Table 25 d0ik This is reflected in the increase in the risk of collapse (0.80 → 1.16). However, by wrapping the columns with the SRF method after cutting the slits, the risk of collapse on each floor is below 1.0 in the table. Also, the table confirms that microtremor observations have shown that the damage level on each floor near measurement 2 is almost below the standard value (1.0). Also, near measurement 1, the damage level in the Y direction is below 1.0. Regarding the fact that damage in the X direction at measurement 1 can be predicted to a certain extent, it is because one type of wall was covered with seismic covering using the SRF method. It is effective to absorb vibration energy by carrying out such measures. The reinforcement work this time was carried out for the purpose of preventing collapse, and from the standpoint of damage control, we would like to implement the above measures in future construction works.

[0211] 4) Average acceleration, average velocity transmission rate B aik , B vik From the microtremor observation results, the average acceleration and average velocity transmission ratio were calculated using formulas 13 and 14, and the values ​​before and after reinforcement were compared and shown in Tables 30 and 31. These are the ratios of the spatial average acceleration or velocity of the part supported by the i-th story of the structure to the acceleration or velocity of the reference point. Therefore, the value for the first floor is the average response magnification of the entire structure. Also, A i is the average acceleration energy transfer rate B aik is the value obtained by normalizing the value of each floor by the value of the first floor (see Equation 17).

[0212] [Table 30]

[0213] [Table 31]

[0214] This building is located on Class 2 ground, and the natural period of the ground is T c = 0.6sec, building height h = 14.3m, the height of the steel frame part is 2.95m, and the ratio λ to the height h [m] of the steel frame floor (excluding the basement) is 0.206. Therefore, according to the current formula (see formula 12), the natural period of the building is calculated as T = h (0.02 + 0.01λ) = 0.32sec. Therefore, T <T c Therefore, the vibration characteristic coefficient R t = 1.0, and it is concluded that the acceleration response magnification is 2.5 to 3.0, which is the standard value at the time the current standards were established.

[0215] With the above in mind, let's look at the measured response magnifications, which are the values ​​for the first floor. The acceleration and velocity are almost similar values, with measurement 1 being 2.5-4.0 before reinforcement and 2.0-3.7 after reinforcement, and measurement 2 being 2.0-2.4 before reinforcement and 1.6-2.2 after reinforcement. The absolute values ​​are roughly the same as the current standard's assumption of 2.5-3.0. This demonstrates the validity of the microtremor diagnostic method.

[0216] Next, we will look at the rate of change before and after reinforcement. As shown in Table 31, the acceleration response magnification of the parts supported by each floor increased slightly (7%) only in the Y direction at measurement 2 after reinforcement, but decreased to about 70-90% in each direction at the other measurement points. Also, the velocity response magnification increased slightly in the Y direction at measurement 2, but decreased at the others. These figures quantitatively show that the reinforcement work has made the structural system less susceptible to the effects of earthquakes. These values ​​are used to calculate the degree of damage, and the above-mentioned features are reflected in the index values ​​mentioned in the previous sections.

[0217] 5) Microtremor characteristics Table 32 shows the RMS of microtremor acceleration before and after reinforcement, as well as the energy transfer coefficient and the rate of change before and after reinforcement. Table 52 shows the central period and bandwidth index of microtremor acceleration before and after reinforcement. Tables 34 to 37 show the characteristics of micro-tremor speed and displacement. The micro-tremor acceleration is measured by an accelerometer, and the speed and displacement are calculated by integrating the data using the linear acceleration method after processing it with a 10Hz high-cut and 0.2Hz low-cut filter. In each table, floor refers to the floor surface of that floor.

[0218] [Table 32]

[0219] [Table 33]

[0220] [Table 34]

[0221] [Table 35]

[0222] [Table 36]

[0223] [Table 37]

[0224] The energy transfer rate is the ratio of the RMS of the reference point defined in paragraph "0067" of this specification to the RMS of each floor, i.e., the vibration amplification rate, and is the basis for calculating each diagnostic index shown in the previous section.

[0225] The central period is calculated using Equation 1, and the bandwidth index is calculated using the method described in paragraph "0156" of this specification. The central period is the expected value of the zero crossing period in the case of a stationary Gaussian process, and the bandwidth index is 1.0 for a sine wave and 0 for white noise. The larger the bandwidth, the closer it is to zero. Looking at the changes before and after reinforcement, the acceleration is almost the same or slightly larger before and after. Also, for the velocity, the central period is slightly larger in measurement 1 and slightly decreased in measurement 2. The bandwidth index increases at both observation points. In other words, the bandwidth is narrower. Looking at the microtremor displacement, the central period clearly decreases and the bandwidth increases after reinforcement. This indicates that the vibration approaches a sine wave and the rigidity of the structural system is improved due to the reinforcement.

[0226] Tables 38 to 40 show the central period measurement values ​​and the current standard primary fixed values ​​for micro-motion acceleration, velocity, and displacement. The figures show a comparison of calculated values ​​with a period. Structures subjected to microtremors or seismic motion vibrate irregularly, so the central periods of displacement, velocity, and acceleration increase according to the bandwidth (see paragraph "0156" in this specification). In this example, the central periods of acceleration, velocity, and displacement are located around the value of the primary natural period calculated using the formula of the current standards. Note that for acceleration, velocity, and displacement, the central period values ​​obtained are almost the same for each point, each floor, and each direction, so it is believed that the entire building is vibrating in a natural mode.

[0227] [Table 38]

[0228] [Table 39]

[0229] [Table 40] EXAMPLES

[0230] 1) Target facilities and measurement methods The measurement subject is an 11-story SRC building (2 spans in the X direction, 1 span in the Y direction, with pilotis apartment building with a parking lot on the first floor (see Figure 24)) completed in 1994. However, there is a staircase in the X direction. Between the end of August and September 2017, two independent columns (A2, A3) on the first floor were wrapped using the SRF method (see lines 1 to 3 of paragraph "0194" in these specifications). Floors 2 to 11 are residential units, and the two floors from 2 to 10 are earthquake-resistant walls. The measurements consisted of two vertical arrays with instruments installed near pillars B2 and B3 on each floor, and three-point planar observations with three instruments each near B1, A2 (see Figure 25) and B3 on the first floor and roof. Before reinforcement, four instruments were used on August 25, 2017, and after reinforcement, 12 instruments were used on December 19 of the same year. It was not possible to enter the second floor near B2. The location of the reinforced pillars and the arrangement of the instruments are shown in the first floor plan in Figure 26.

[0231] 2) Measurement results Figure 27 shows the horizontal traces of the micro-tremor displacement of the B3 vertical array after reinforcement, divided into three parts of two minutes each for six minutes on each floor. It can be seen that the displacement is amplified from the first floor to the upper floors, and that each point moves in a circular motion.

[0232] Table 41 shows the energy transfer rate (ratio of micro-motion displacement RMS of the first floor and that floor) and the rate of change before and after reinforcement for the B2 vertical array and rooftop surface, and Table 42 shows the energy transfer rate for the B3 vertical array. The column marked "surface" in Table 41 shows the energy transfer rate for rotation around the coordinate axes of the rooftop surface. After reinforcement, the rate around the X-axis was reduced to about 1 / 10, and the rate around the Y-axis was reduced to about 1 / 30. The columns below RF in Tables 41 and 42 show the energy transfer rate for translational motion and the ratio before and after reinforcement, but for B2 and B3 Both of these values ​​decreased significantly on higher floors. These results show that the vibration mode was stabilized by wrapping the two independent columns (A2, A3) in the first floor pilotis section, and especially the lower floor wall-passing column A2, using the SRF construction method.

[0233] Moreover, Figure 27 shows a moment before reinforcement, and Figure 28 shows a moment after reinforcement, when the displacement data (3 components of XYZ) from microtremor gauges installed at three points on the roof surface was input into the structural analysis results visualization software AVS and visualized (animated). The animation shows that before reinforcement, the roof surface vibrated significantly up and down and left and right, but after reinforcement, it vibrates in a circular motion on an approximately horizontal plane. This clearly shows that the energy transfer coefficients around the X-axis and Y-axis, shown as surfaces in Table 1.3.9.1, have decreased to 11% and 3%, respectively, before and after reinforcement.

[0234] [Table 41]

[0235] [Table 42]

[0236] Tables 43 and 44 show the measured values ​​of the story shear force distribution coefficient (Ai) and the central period of microtremor displacement (Tc) after reinforcement, and the calculated values ​​of the primary natural period (T) according to the earthquake resistance code (described in paragraphs "0038" to "0058" of this specification). The measured values ​​of A1 are almost the same up to around the 5th floor, but are clearly smaller than the calculated values ​​on the upper floors, indicating that the amplification of earthquake motion is small, that is, this is a vibration mode specific to pilotis structures. The central period varies slightly between the lower floors and the roof, but on the upper floors, both B2 and B3 are almost constant and close to the calculated values.

[0237] [Table 43]

[0238] [Table 44]

[0239] Table 45 shows the story shear coefficient of the first story when the horizontal bearing capacity near B3 is reached (C ui1km) is the actual measured value (Equation 27). For the 2nd to 10th floors, the Y direction is smaller than the X direction. The high value reflects the fact that the partition walls on both sides from the 2nd to 10th floors are earthquake-resistant. Also, the value on the 4th and 5th floors is lower than the other floors. This building was hit by heavy rain while concrete was being poured on the 4th and 5th floors, and work was halted, evacuated, and resumed about a week later. It is believed that the heavy rain and the interruption to the work caused a deterioration in the quality of the concrete, resulting in a decrease in its horizontal bearing capacity (strength).

[0240] [Table 45]

[0241] Tables 46 and 47 show the contents of paragraphs "0119" to "0172" of this specification and the velocity conversion values ​​(V mik ) and damage level (I dik The characteristics of the input earthquake motion are as follows: strong earthquake duration s0 = 7 sec, maximum velocity V max =0.8m / sect, maximum acceleration V max =4.0m / sec 2 In addition, taking into consideration that this is a building that complies with the new earthquake resistance standards, the ductility index F is set for each floor and in each direction. uik = 3.0. Note that the limit number of repetitions is set to N = 3.0, taking into consideration that the columns on the second floor and above are made of steel-reinforced concrete. ik = 15, and the first floor was reinforced by the SRF method. ik =45.

[0242] Tables 46 and 47 show the input earthquake motion as a value representative of the recent earthquake environment, with the strong earthquake duration s0 = sec and maximum velocity V max =1.2m / sec, maximum acceleration A max =10m / sec 2 (See Table 19.) The toughness index and the limit number of cycles are as described above.

[0243] Looking at the calculation results of the hysteretic energy absorption in Table 46, it turns out that for the earthquake motion assumed in the current standards, almost no energy is absorbed in the Y direction (yield displacement is not reached). However, In the X direction, the results show that the 4th, 5th and top floors, where poor concrete construction is suspected, will yield. In addition, for the earthquake motion representative of the recent earthquake environment in Table 48, the results show that a large amount of absorbed energy will be observed, except for the intermediate floors in the Y direction near B3.

[0244] The damage levels in Tables 47 and 49 indicate whether the energy absorbed by each floor falls within the damage limit, and for the earthquake motion assumed in the current standards, the results show that the energy absorbed in the vicinity of B2 and B3 falls below the limit value (1.0) in both the X and Y directions. In this sense, it can be said that the building complies with the current standards (new earthquake resistance standards). However, the results show that the 4th, 5th and top floors, where poor concrete construction is suspected, are almost at the limit. On the other hand, for the earthquake motion representative of the recent earthquake environment in Table 49, the results show that the energy absorbed in the Y direction near B3 falls within the limit except for the 4th and 5th floors, but there is significant damage in the X direction. This building has a pilotis structure, and Table 48 calculates that a large hysteretic energy will be generated on the first floor, but even so, the results show that the first floor, which has columns reinforced by wrapping with the SRF method, and the second floor directly above it fall within the limit value. The results show that the damage reduction measures should be considered for other floors as well, such as wrapping methods.

[0245] Although the above example is tentative, the limit number of cycles and ductility index for each component can be determined from the load-displacement history and damage level obtained from repeated loading tests on the same type of component. The maximum acceleration, velocity, displacement, and duration of the strong earthquake motion can be determined by combining the results of earthquake motion observations.

[0246] [Table 46]

[0247] [Table 47]

[0248] [Table 48]

[0249] [Table 49]

[0250] As described above, the damage level of the present invention can quantitatively indicate the degree of damage to a structure according to the level of earthquake motion and the effectiveness of countermeasures against it, using various transmissibility rates actually measured by microtremor observation of the structure, the number of limit cycles, and the ductility index, which contributes to the rationalization of earthquake-resistant design.

[0251] An example of application of the method of the present invention to a block wall will now be described.

[0252] 1. Installation Figure 29 is a schematic diagram showing the relative positioning of the block wall, foundation, and ground in relation to the microtremor meter, with the microtremor meter 1 installed horizontally on the top 17 of the block wall 16, on the foundation 18, or on the ground surface 20 near the foundation 18. When installing the microtremor meter 1 on the top 17 of the block wall 16, the foot 1a of the microtremor meter 1 should be on the center line of the top 17 of the block wall 16. When installing on the top 17 and surrounding ground 21, or when the friction on the foundation 18 is large, a steel plate is used.

[0253] 2. Measurement Simultaneous measurements are taken for about six minutes on the top 17 and foundation 18. The data is analyzed using a free kick and microtremor diagnostics Excel, just like the building diagnosis. At this time, the floor height is taken to be H, the height of the block wall 16 (the difference in z coordinate between the microtremor gauge 1 on the top 17 and the microtremor gauge 1 on the foundation 18 or surrounding ground 21), and the weight supported by the story is taken to be zero. The calculations are the velocity, displacement, RMS, central period, and transmissibility of each time history. The inter-story displacement or absolute displacement of the top is set as the time history of interest d(t), and the measurement point of the foundation 17 or the surrounding ground 21 (see No. 1 in Figure 29) is set as the reference point, and the transmissibility (h dk ) to calculate

[0254] 3. Diagnosis Displacement of the reference point x for a large earthquake assumed by the diagnostic criteria Gkmax The relative or absolute displacement of the top 23 when the height is set to 2.5 cm is predicted using the formula below (formula 1.4.8 in yellow).

[0255]

number

[0256] In the above equation, d(t)=y2(t)-y1(t), h dk = RMS[d(t)] / RMS[y1(t)], the relative displacement is predicted.

[0257] Also, d(t) = y2(t), h dk = RMS[d(t)] / RMS[y1(t)], the absolute displacement is predicted.

[0258] Here, d(t), y2(t), and y1(t) are the relative displacement between the top 23 and the reference point, the absolute displacement of the top 23, and the y-direction (orthogonal to the block wall 22) component of the absolute displacement of the reference point, respectively.

[0259] The risk of collapse of the block wall 15 (I tbw ) to calculate

[0260] If the average value of the tipping limit slope is D / H, the formula is as follows.

[0261]

number

[0262] where D [cm] is the width of the block wall 15 (see Figure 29), and E [d Gkmax ] is the expected absolute or relative displacement of the top 16 of the block wall 15 in the event of a major earthquake as assumed in the seismic assessment standards, and a (see Table 50) is the limit displacement of the top when the limit slope is D / H.

[0263] [Table 50] EXAMPLES

[0264] Next, a specific example of microtremor measurement in which the method of the present invention is applied to a block wall will be described below.

[0265] The specifications are as follows: Location: Block wall of an apartment building in Hirakata, Osaka Prefecture Structure: CB construction Thickness: 150mm Extension: ~15000[mm] Height: 1870 [mm] (The height from the reference measuring device to the top is 1790 [ mm] Block size: (thickness x extension x height) 150 [mm] x 390 [mm] x 200 [mm] Buttress: None Four micromotion measuring devices used

[0266] Figure 30(a)-(c) show the actual measurement conditions at each measurement point, with (a) showing the condition at measurement point 1, (b) showing the condition at measurement point 2, and (c) showing the condition at measurement point 3. Also, Figure 31 is an explanatory diagram that shows a schematic diagram of the arrangement of the measurement device (micromotion gauge) when the block wall is viewed from above, corresponding to Figure 30.

[0267] The risk of a block wall collapsing was calculated using Formula 51. The results are shown in Table 51.

[0268] [Table 51]

[0269] According to Table 51, the risk of falling is below 1.0 in all cases, and it was determined that the risk of falling is not high for earthquake motions assumed in the seismic assessment standards (maximum displacement 2.5 cm). However, there is a risk of falling for earthquake motions that exceed this level (for example, recent earthquake motions).

[0270] The role of micromotion diagnosis The method of assuming that the action of an earthquake is an inertial force proportional to the ground acceleration (inertial force approximation) is the basic principle of current earthquake-resistant design, regardless of whether the earthquake resistance standards are new or old, or whether the calculation is dynamic or static. This, combined with the development of numerical calculation methods such as the finite element method and digital computers, has been the driving force behind the construction of structures of a scale, shape, and material that have never existed before on earth in earthquake zones around the world, including Japan, from the latter half of the 1960s to the present. The new earthquake resistance standards stipulate that the collapse process of structures must be numerically tracked, making earthquake resistance calculations so complicated that structural design is impossible without specialized software. Even experts cannot physically grasp the details of structural earthquake resistance indices, horizontal bearing capacity, or the calculation process of dynamic analysis. The current situation is that we have no choice but to trust the numbers that computers churn out. Meanwhile, earthquake activity has increased from the end of the 20th century to the beginning of this century, with both the magnitude and duration of observed earthquake motion exceeding the assumptions of the current standards, which were established based on earthquake observations up until the 1970s, by several times to an order of magnitude.

[0271] The inertial force approximation does not hold for recent earthquakes where ground acceleration exceeds 1G. The irrationality of designing a structure-ground system that is moving three-dimensionally in separate x- and y-directions also becomes evident. In the first place, the spatiotemporal scale of a large earthquake is incomparable to the scale of an individual structure. If we try to capture the seismic motion of a large earthquake at the scale of a structure, it becomes extremely random. The phenomena caused by a large earthquake change significantly and discontinuously with even a slight change in conditions. It is called a statistical phenomenon. It is not reasonable to build a structure of a size or type that has never existed before based on calculations using the current standard methods, both in terms of the input seismic motion and the assumptions and models of the calculations.

[0272] Research into modern earthquake-resistant structures, which began in Japan after the 1891 Nobi earthquake, combined with the development and improvement of design and construction techniques for reinforced concrete materials, allowed the country to withstand the Great Kanto Earthquake of 1923, and by the 1960s had created a dignified landscape of low- to mid-rise RC buildings in major cities such as Tokyo. However, the lifting of height restrictions in 1963, the 1964 Tokyo Olympics, the high economic growth policy, and the rapid spread of concrete pumping construction methods contributed to the demolition of older buildings, leading to overcrowding and rapid construction of high-rise buildings.

[0273] In the 1995 Great Hanshin-Awaji Earthquake, which hit areas with a seismic intensity of 7, about half of low- to mid-rise RC buildings were undamaged, even under the old standards, except for the pilotis. Only a few percent of buildings collapsed. Civil engineering structures such as Shinkansen viaducts and expressways collapsed, but they were subjected to earthquake motions several times greater than expected in the design, and the damage was concentrated in areas where the ground was heavily influenced, such as old river channels, so it is said that they were bound to collapse. The same was true in the 2011 Great East Japan Earthquake. Even under the old standards, only a few buildings collapsed due to earthquake motions. Of the 98 low-rise reinforced concrete public buildings with an Is value of 0.3 or less that were subjected to an earthquake of intensity 5 or more, none collapsed, and 97 buildings continued to be used with almost no damage. On the other hand, school buildings and apartment buildings that had been reinforced against earthquakes became unusable and were demolished or had to undergo large-scale repairs. In addition, although the Tohoku Shinkansen had already been reinforced against earthquakes using steel plates on its piers, it was closed after the earthquake due to the destruction of beams and damage to the superstructure such as overhead wires, and it took more than 50 days to restore the line.

[0274] The need for a fundamental revision of the current earthquake resistance standards is stated in the aforementioned diagnostic criteria. Here, we will explain the features of microtremor diagnosis and the role that microtremor diagnosis plays in carrying out rational earthquake resistance design, supervision, and reinforcement work.

[0275] (1) Response calculation The performance required of a structure during an earthquake is to minimize damage and to be able to continue to use it. With recent earthquake motion levels where the ground acceleration exceeds 1G, not only is it physically difficult to track a structure after it has become nonlinear using indicators such as horizontal bearing capacity, but from the perspective of ensuring continued use, structures that do not become nonlinear themselves, that is, buildings with high strength (high hurdles for nonlinearization) as stated in the diagnostic criteria, are desired. Response calculations reveal vibration modes, maximum acceleration, velocity, displacement, and hysteretic absorbed energy when a structure-ground system responds linearly to a specific earthquake motion or general earthquake motion. Microtremor diagnosis can directly obtain the information necessary for calculations within the elastic range. It is also easy to compare calculations with actual measurements.

[0276] (2) Earthquake motion assumptions The action of an earthquake is a near-field action. It is reasonable to determine the expected earthquake motion (earthquake motion used in calculations) based on the actual phenomenon of earthquakes traveling from the epicenter to the surrounding ground, from the surrounding ground to the foundation, and from the foundation to the first floor columns, from bottom to top. The method of determining the response acceleration or response spectrum of a structure in advance, as is done in the current building standards, is not only irrational, but also poses the risk of generating excessive seismic forces in the structure, causing it to collapse or suffer major damage. Furthermore, it would be counterproductive to numerically synthesize earthquake motion that matches the response spectrum and perform a time history response analysis.

[0277] One method for defining the expected earthquake motion is to use the engineering bedrock surface, which is used in limit strength calculations, etc. However, the earthquake motion that a structure actually receives is not only that of the engineering bedrock directly below it, but is also affected by a wide area of ​​the bedrock surface that spreads out in three dimensions. Calculations based on the actual phenomenon, that is, three-dimensional vibration analysis calculations of the ground, are almost impossible. If one instead calculates one-dimensional multiple reflections, the difference between the earthquake motion actually input to the structure and the calculated earthquake motion is inevitably very large.

[0278] In microtremor diagnosis, input vibrations are applied to the foundations of structures. The characteristics of the expected earthquake motion are the maximum acceleration, maximum velocity, maximum displacement, and duration of the strong earthquake. However, even if specific values ​​are determined for the magnitude of the expected earthquake motion, these are still only expected values ​​(average values). The actual earthquake motion will vary greatly from these values.

[0279] (3) Performance evaluation In recent earthquakes where ground acceleration exceeds 1G and lasts for more than a few minutes, visible displacements are unavoidable in buildings from wooden to high-rise buildings, and many repeated displacements occur. Furthermore, rather than tallying up indicators for each layer of a structure, it is necessary to evaluate performance using an aggregate of indicators for each individual component or part. In microtremor diagnosis, the degree of damage is defined and used as an index to directly evaluate the continuity of use. This is called the seismic isolation performance index.

[0280] (4) Rational earthquake-resistant structure With recent earthquake motion levels, structures that exhibit a total collapse pattern, as assumed in the current standards, will inevitably collapse according to calculations, and continued use is not possible. A rational structure would be one that is designed in advance to allow large deformations and vibrations, with parts that absorb the energy of earthquake motion and parts that keep deformation within the damage limit. In regular RC structures, the capitals and bases of each column act as bending hinges, causing overall deformation and movement. In eccentric structures or pilotis structures, the capitals and bases of columns in the areas with fewer walls move, and the pilotis floor, or the part that is shaken by the eccentricity, vibrates greatly and absorbs the energy, thereby minimizing deformation in other floors and areas. In RC structures, unless the site is on bedrock, the rigidity of the structural frame is sufficiently greater than the surrounding ground, so in addition to the vibrating parts of the frame mentioned above, you should plan to absorb energy at the boundary (foundation) between the frame and the surrounding ground. It is effective to incorporate the relative movement between the foundation and the surrounding ground into the design. In wooden structures, the deformation and energy absorption capacity of each joint and nailing part is large, so the joints and nailing parts should have three-dimensional mobility and resilience. You should also specifically reflect in the design the reduction in earthquake action caused by the foundation lifting off the foundation. By calculating the cumulative strength index and damage level of each part of a structure against the assumed earthquake motion of the current standards through microtremor diagnosis and visualizing the natural vibration mode, it is possible to extract vibration antinodes and nodes, and by carrying out reinforcement to give the key members and joints an energy absorption capacity, it is possible to create a structure with the movement and energy absorption capacity to withstand a major earthquake. The SRF method is effective for the above reinforcement.

[0281] (5) New construction inspections and structural repair inspections After the construction of a structure is completed or after the renovation work is completed, a microtremor diagnosis is carried out to determine the vibration mode and vibration period (T m ), story shear force distribution coefficient (A im ), response ratio (R amk, R vmk ), cumulative strength index (C T S D ) m , damage degree (I dm ) and compare it with the design calculation. It can be used to confirm the validity of calculations and construction, and to decide whether to add countermeasures if necessary. The above indexes are calculated for the entire structure, and the vibration characteristics of each part are also understood by installing vertical array measurements in each part. Currently, in mid-term and confirmation inspections of new buildings, inspectors only visually check whether the building conforms to the blueprint. The same is true for seismic retrofitting. Microtremor diagnosis can add objective numerical values ​​to the inspectors' judgment criteria.

[0282] (6) Periodic health checks Conduct microtremor diagnosis periodically and measure each of the indicators mentioned above. If deterioration of the structure is found, the results will be used as a basis for making a decision on whether to carry out repairs. In addition, after repairs are made, microtremor diagnosis can be carried out again to provide information to confirm the effectiveness of the repairs.

[0283] (7) Seismic assessment and seismic retrofit design for existing structures Microtremor diagnosis is carried out on existing structures built under current or previous earthquake resistance standards, and the seismic performance is evaluated, and the results are used to design and implement countermeasures, if necessary. Measurements and diagnosis are also carried out before and after reinforcement, and the results can be used to quantitatively confirm the effectiveness of reinforcement. Currently, seismic assessments are carried out over a period of several months and at a cost of several million yen or even more than 10 million yen. This is because the calculations are complex and require advanced expertise. If the diagnostic calculations were simplified and judged in conjunction with the indices obtained from microtremor assessments, the cost and time would be reduced. can be significantly reduced.

[0284] (8) Analysis of Damaged and Non-Damaged Cases In the future, if many actual measurement examples are accumulated and correlation analyses are performed with actual damage / non-damage in actual earthquakes, it is expected that the ratio of calculations and diagnostician's judgments will be minimized, and it will be possible to carry out seismic diagnosis mainly based on microtremor diagnosis results and retrofit design such as identifying areas that need to be renovated. Furthermore, it will be possible to increase the role of microtremor diagnosis at the time of new construction, after renovation, and in regular inspections, and narrow down calculations and judgments to the necessary scope.

[0285] Regarding the issues with earthquake resistance standards and solutions using the SRF method (bandage reinforcement), we published a paper titled "Revolutionizing Earthquake Resistance" in April 2017. We hope that this, along with microtremor diagnosis, will help streamline earthquake resistance design and reduce the economic burden and risk of earthquakes.

[0286] As is clear from the above detailed explanation, according to the present invention, the expected values ​​of the cumulative strength index and structural seismic index used in the diagnosis and seismic retrofit design of existing structures, the expected value of the height-wise distribution coefficient of story shear force used in current designs for new buildings, and the damage degree for directly evaluating the continued use of a structure are defined and each expected value is obtained directly from the measured microtremor values. By observing each part of a structure with a vertical array, it is possible to measure the vibration properties, strength, damage degree, etc. of each floor part (zone). As a result, it is possible to directly, inexpensively and quickly evaluate the soundness and safety of a structure not only by far more detailed seismic design and reinforcement than by conventional methods in which external forces are applied directly to the target object, but also by far more detailed seismic evaluation according to individual vibration characteristics, and the seismic design and continued use of a structure (which is the most important target performance in implementing seismic reinforcement work).

[0287] In other words, according to the present invention, by using the above-mentioned indicators, seismic diagnosis can be performed much more cheaply and quickly than current seismic diagnosis after new construction, after renovation work, and during periodic diagnosis, thereby enabling rational seismic reinforcement design and seismic design of newly constructed structures. [Explanation of symbols]

[0288] 1 Microtremometer 1a Foot 2 Analyzer 10 Structures 10a,10b,10c layer boundary surface 11 RC hospital building 12 1st floor 13 2nd floor 14 3rd floor 15 4th floor 16 Block Wall 17 Top 18 Basics 20 Ground surface 21 Surrounding ground

Claims

1. In a method for evaluating the performance of a structure through continuous microtremor observation, The microtremor time histories are simultaneously observed at multiple observation points within the structure, and the square of these time histories is calculated. Using the root mean square (RMS), calculate the estimated value A of the index used in the seismic design of the structure. Then, the ratio of this value A to the value B of the index used at the time of design corresponding to this value A is used to calculate the above structure. An evaluation of seismic performance of a structure based on the observation, The index is the horizontal bearing capacity specified in the current standards, The horizontal bearing capacity b (see column b in Table 8) is distributed to each story of the structural model of the building. The shear force is gradually increased and the story shear force a acting on the i-th story when the i-th story yields is calculated as follows (Table (See column a of Section 8.) The relationship between the story shear force generated in a structure due to the ground motion and the acceleration of the reference point is the average acceleration Transmission rate (B ａｉｋ ) The relationship between the story drift and the acceleration at the reference point is expressed by the energy transfer rate, The expected horizontal strength is the maximum value of the inter-story displacement of the i-th story when the structure responds linearly. The expected value when the yield displacement is reached, assuming that layers other than the i-th layer do not yield. is the expected horizontal strength, The average acceleration energy transfer rate is When considering the action of an earthquake on the i-th layer, the part b supported by that layer (i-th to n-th layers) is an index that gives the RMS of the average acceleration of the [Equation 13] (where m ｊ is the mass of the jth layer, a (see column a in Table 5) is the acceleration of the jth layer in the k direction. Energy transfer rate, B ａｉｋ is called the average acceleration energy transfer rate. The energy transfer ratio is the ratio of the RMS of the microtremor time history of interest to the microtremor time history of the reference point. In the diagnosis, it is assumed that this is preserved at the time of maximum elastic response due to earthquake motion input, and the peak factor is With appropriate assumptions, the maximum response of the time history of interest is calculated by multiplying the maximum input value at the reference point by the energy transfer rate. Calculate. [Table 5] ） and The expected value of the horizontal bearing capacity is the expected value c of the horizontal bearing capacity shown in column c of Table 8, The acceleration in the k direction of the reference point is the acceleration d in the k direction of the reference point shown in column d of Table 8, The inter-story displacement in the k direction of the i-th story relative to the acceleration d in the k direction of the reference point (e ｉｋ (t)) energy The energy transfer coefficient is the acceleration d in the k direction of the reference point shown in column e of Table 8. Story displacement (e ｉｋ (t)) is the energy transfer rate e, [Table 8] The inter-story displacement in the k direction of the i-th story relative to the acceleration d in the k direction of the reference point (e ｉｋ (t)) energy The gear transfer coefficient e is [Equation 20] It is expressed as (where σ eik is the RMS of the story displacement time history in the k direction of the i-th story, and is the component on the right side of Equation 20. is the RMS of the acceleration time history in the k direction of the reference point. a ｉｋＹ is the maximum value of the story drift e ｉｋｍａｘ is the yield displacement e ｉｋＹ The standard for reaching is the maximum value of the acceleration of the point, [Equation 21] The expected maximum value of the story shear force at this time, a (see column a in Table 9), is the part supported by the i-th story. The mass b of b (see column b of Table 9) is the expected maximum average acceleration of this part A ｂｋｍａｘ It is calculated by multiplying [Table 9] [Equation 22] The estimated value A of the index is the expected value a of the maximum value of the story shear stress (see column a in Table 9), i.e., The expected horizontal strength shown in column c of 8 is A diagnostic evaluation method for structures based on their microtremors.

2. In a method for evaluating the performance of a structure through continuous microtremor observation, The microtremor time histories are simultaneously observed at multiple observation points within the structure, and the square of these time histories is calculated. Using the root mean square (RMS), calculate the estimated value A of the index used in the seismic design of the structure. Then, the ratio of this value A to the value B of the index used at the time of design corresponding to this value A is used to calculate the above structure. An evaluation of seismic performance of a structure based on the observation, The index is the base shear coefficient defined in the current standard, The base shear coefficient is the story shear coefficient of the first story when the horizontal bearing capacity is reached, Expected value of base shear coefficient C ｕｉ１ｋｍ but, [Equation 8] (Here, Ai is the story shear force normalized by the first story shear force a (see column a in Table 3). The value b (see column b in Table 3) and the weight of the layer above that layer are taken as the total weight (total weight) W The amount normalized by α ｉ is a ratio of the story shear force to the height direction. [Table 3] C ｉ is the earthquake layer shear force coefficient, Z is the regional coefficient, R ｔ is the vibration characteristic coefficient and C ０ Standard is the shear force coefficient, C ｉ teeth [Equation 6] It is expressed as For the first layer, [Equation 7] It is. In addition, when a building consisting of n stories vibrates due to the action of an earthquake, the story shear force a is is the maximum shear force generated in the specimen (see column a in Table 2), The weight b supported by that layer is the value shown in the b column of Table 2. [Table 2] [Equation 5] Also, column a in Table 3 is the shear force of the first layer, Column b in Table 3 indicates the shear force standardized by the shear force a of the first layer. P ｊ is the seismic force acting on the jth story of the building, k ｊ is the seismic intensity, W ｊ is the weight of the jth story of the building, P ｊ teeth, [Equation 4] It is expressed as α ｉ is the standardized weight.) [Equation 26] (Here, H ０ｉｋ [m] is the floor height of the i-th floor in the k-direction, R Ｙｉｋ [rad] is the yield deformation angle, g [m / sec ２ ] is the acceleration due to gravity.) is obtained by dividing by Ai, The estimated value of the index, A, is the expected value of the base shear coefficient, C ｕｉ１ｋｍ That is, A diagnostic evaluation method for structures based on their microtremors.

3. The continuously measured microtremor time history is divided, and a plurality of partial time histories are extracted. The expected value of the index is calculated for the time history, and the sample average is used as the estimate of the index. The structure based on microtremors of a structure according to claim 1 or 2. Diagnostic evaluation methods for artifacts.

4. The continuous micromotion measurement method for a structure according to claim 3, wherein the duration of the partial time history is 1 to 2 minutes. A diagnostic evaluation method for structures based on the above.

5. The above observations are carried out after the construction of the structure, before and after renovation work, and during regular inspections. By comparing the estimated values ​​of the above points, the seismic performance of the structure and the risk of collapse in a major earthquake can be calculated. Diagnose and evaluate at least one of the changes over time in the continuity of use and the changes before and after the repair work.

3. A method for diagnosing and evaluating a structure based on microtremors of the structure according to claim 1 or 2.

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