JP2003322593A - Residual fatigue life estimating device for steel structure weld part, estimating system, estimating method, program, and storage medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To predict the residual fatigue life of a steel structure weld part. <P>SOLUTION: This device is equipped with a measurement means for continuously measuring stress or strain and displacement of a weld part, a storage means for storing the stress or strain and displacement measured by the measurement means, a frequency calculation means for calculating the frequency of the amplitude of the stress or strain, a measurement period measuring means for measuring the period of measurement of the stress or strain and displacement, an inclination calculating means for calculating an inclination in relation between the stress or strain and the displacement, a crack occurrence life determining means for determining a fatigue crack occurrence life based on the amount of change in the inclination, a fatigue life database, a life calculating means for calculating the degree of fatigue damage and residual fatigue life based on the frequency of the amplitude of the stress or strain, the measurement period, and the database, and a life correcting means for correcting the fatigue life based on the occurrence life. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for estimating the residual fatigue life of a welded steel structure used for automobiles, ships, bridges, construction machines, building structures, offshore structures, storage tanks, pen stocks, etc. The present invention relates to a system, a method, and a program and a storage medium that store processing steps for implementing them.

[0002]

2. Description of the Related Art In a welded portion of a steel structure, stress concentration and welding residual stress are superposed on each other, which often causes fatigue fracture. Since the shape of the weld toe is discontinuous due to the presence of weld beats, it is difficult to detect the occurrence of fatigue cracks along the weld toe. Further, in a steel structure having a large number of welded portions, it is necessary to inspect all the welded portions in order to identify the welded portions where fatigue cracks occur, which requires a great deal of labor. Therefore, a method or device for non-destructively measuring fatigue damage of a structure,
Several methods have been developed to predict fatigue strength.

For example, a report on the relationship between fatigue damage and changes in half width and integrated intensity due to X-ray irradiation, changes in sound velocity and frequency of ultrasonic waves, and the like, "Nondestructive Inspection" edited by the Japan Nondestructive Inspection Association. "Special Issue Material Degradation Diagnosis, Vol. 46, No. 3, 1
Shown in 997. In addition, the method of obtaining the frequency distribution of the stress amplitude or strain amplitude and estimating the fatigue life by comparing it with the fatigue data of the test piece or the fatigue design diagram is usually used. "Fatigue strength design guideline / commentary", Gihodo Publishing, April 25, 1993
Issued day).

Further, for example, in Japanese Patent Laid-Open No. 58-215211,
For shear pins, means for calculating cumulative fatigue damage from external force torque, means for calculating fatigue crack growth prediction, crack detecting means, and cumulative fatigue damage when crack detecting means detects an initial crack And a means for correcting the initial crack initiation curve in accordance with the above, a life monitoring device is proposed.

Further, Japanese Patent Application Laid-Open No. 59-56147 proposes a method and apparatus for predicting a fatigue fracture timing from a load continuously measured for a pipe expander pull rod and a fatigue limit obtained in advance.

Further, as a method and apparatus for embodying an algorithm for calculating the degree of fatigue damage to an actual load, the stress is classified into peak values, the fatigue damage due to each stress is calculated, and the fatigue damage is calculated by adding them. The method for obtaining the value is described in Japanese Patent Application Laid-Open No. 59-37443 together with the apparatus.

[0007]

Among the conventional techniques, the method of directly measuring fatigue damage by X-rays or ultrasonic waves has variations in the relationship with fatigue damage because these measured values are sensitive to changes in other materials. Is very large, and the life expectancy also varies greatly, which is not practical. Further, the method of comparing the frequency distribution of the stress amplitude or strain amplitude with the fatigue data of the test piece or the fatigue design diagram is inevitably the life estimation on the safe side in consideration of the variation of the fatigue data.

Further, Japanese Patent Application Laid-Open No. 58-215211 proposes a device equipped with a fatigue crack detecting means in addition to a fatigue damage degree calculating means due to stress. However, as the fatigue crack detecting means, an acoustic emission element or An ultrasonic flaw detector is described. However, the acoustic emission element and the ultrasonic flaw detector have low accuracy in measuring fatigue damage as described above, and it is necessary to attach these measuring devices in advance assuming a crack occurrence location.

The present invention has been made in view of the above problems, and an object thereof is to accurately estimate the fatigue life of a steel structure including a large number of welded portions.

[0010]

In order to solve the above problems, the gist of the present invention is as follows: (1) Remaining steel structure welded portion for estimating fatigue life of steel structure welded portion A show life estimation device, comprising one or more measuring means for continuously measuring stress or strain and displacement of a welded portion, and stress or strain measured by the measuring means,
And storage means for storing the displacement, frequency calculation means for calculating the frequency of the amplitude of the stress or strain stored in the storage means, and measurement period measurement for measuring the measurement period during the measurement of the stress or strain and the displacement. Means, the inclination calculation means for calculating the inclination in the relationship between the stress or strain and displacement, the crack generation life determination means for determining the fatigue crack generation life based on the amount of change in the inclination, the fatigue life database, the Frequency of stress or strain amplitude, life calculation means for calculating fatigue damage level and residual fatigue life based on the measurement period and the fatigue life database, and life for correcting the residual fatigue life based on the fatigue crack initiation life It is characterized by comprising a correction means.

(2) Further, in the apparatus for estimating the remaining life of the welded portion of the steel structure according to (1), the inclination calculating means has at least one stress or strain measured at the welded portion and at least one location. For one or more combinations of the above displacements, the slope in the relationship between the stress or strain and the displacement is calculated.

(3) Further, in the apparatus for estimating the remaining life of the welded portion of the steel structure according to the above (1) or (2), the crack initiation life determining means is a change in inclination in the relationship between stress or strain and displacement. The threshold value can be changed by comparing the amount with a threshold value for determining that a crack has occurred, and the threshold value can be changed according to the amount of change in the inclination.

(4) Further, in a fatigue life estimation system in which a plurality of devices are communicatively connected, at least one device among the plurality of devices has the above (1) to
It is characterized by having the function of the fatigue life estimation device according to any one of (3).

(5) A method of estimating the residual fatigue life of a welded portion of a steel structure, which comprises stress or strain of the welded portion,
And a measurement step of continuously measuring the displacement for a certain period of time,
Of the measured stress or strain, and a storage step of storing the displacement, a measurement period measurement step of measuring the measurement period during the measurement of the stress or strain and displacement, the stress or strain, and the stress or strain and displacement from the displacement A slope calculation step of calculating a slope in a relationship, a crack generation life determination step of determining a fatigue crack generation life based on the amount of change in the slope, a frequency calculation step of calculating a frequency of the stress or strain amplitude, and A life calculation step of calculating the degree of fatigue damage and the remaining fatigue life from the frequency of stress or strain, the fatigue life database and the measurement period;
And a life correction step of correcting the remaining fatigue life from the fatigue crack initiation life and a fatigue life database.

(6) Further, the program according to the present invention is
The function of the fatigue life estimation device according to any one of (1) to (3), the function of the fatigue life estimation system according to (4), or the processing step of the fatigue life estimation method according to (5) described above is performed by a computer. It is characterized by making it execute.

(7) Further, a computer-readable recording medium according to the present invention is characterized by recording the program described in (6) above.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION As shown in FIG. 1, the present invention relates to, for example, stress or strain generated in a structural member in the vicinity of a welded portion of a steel structure, and displacement (that is, deflection The device, system, method, program, and storage medium are proposed which have a means for determining the slope (hereinafter referred to as “compliance”) in relation to the crack generation life and determining the crack generation life from the amount of change during the measurement time. . In the state where there is no fatigue crack, the steel structure is elastically deformed as a whole, so the compliance is constant regardless of the size of the load, but as shown in Fig. 2, when a fatigue crack occurs in the steel structure, the same load acts. However, since the compliance near the crack is based on the mechanism of detecting the crack by changing from before the crack is generated, Japanese Patent Laid-Open No. 58-215
This is an invention different from that of Japanese Patent Publication No. 211.

Further, Japanese Patent Laid-Open No. 59-56147 is a method and apparatus for predicting a fatigue fracture timing from a fatigue limit obtained in advance only by measuring an acting stress. It is a different invention in that it does not include a means for determining the crack initiation life due to.
Further, JP-A-59-37443 discloses a method and apparatus for determining the degree of fatigue damage by classifying the operating stress according to its magnitude, and also provided with a means for determining the fatigue crack occurrence life. Apparatus and method different from the present invention.

Embodiments of the present invention will be described below with reference to the drawings. The present invention is applied to a fatigue life estimation system 100 as shown in FIG. 3, for example.

<Overall Configuration of Fatigue Life Estimation System 100>
As shown in FIG. 3, the fatigue life estimation system 100 of the present embodiment uses a stress or strain measuring device 111 as a measuring device 110.
(1), 111 (2), ... 111 (y) and displacement measuring instrument 112
(1), 112 (2), ... 112 (x) are connected to the storage device 120 through wiring, and further, the storage device 120 is connected to the computing device 130.

<Outline of Configuration and Operation of Stress or Strain Measuring Instrument 111> Stress or Strain Measuring Instrument 111 (1), 111
(2), ... 111 (y) have the same configuration, so for the sake of simplicity of explanation, an arbitrary stress or strain measuring instrument is used here.
The description will be given focusing on the configuration and operation of 111 (y).

The stress or strain measuring device 111 (y) is a device for measuring the stress or strain at a specific position of the steel structure, for example, a combination of a strain gauge and a strain amplifier, and a gauge length interval. It can be realized by combining an extensometer and an amplifier. Stress or strain measuring instrument 111
(Y) has a function of continuously measuring the stress or strain at a specific position and outputting the measured stress or strain as a voltage or current to the storage device 120. The stress or strain measuring instrument 111 (y) may be installed in at least one place when there is only one fatigue crack occurrence point in advance and the main stress or strain direction is clear, but there are many welding points. When it is difficult to specify the fatigue crack occurrence location and the main stress or strain direction, and in order to improve the accuracy of determining the crack initiation life, it is preferable to install two or more.

<Outline of Configuration and Operation of Displacement Measuring Device 112>
The displacement measuring instruments 112 (1), 112 (2), ... 112 (x) are
Since each has the same configuration, for simplicity of explanation here,
The description will be made focusing on the configuration and operation of the arbitrary displacement measuring instrument 112 (x).

The displacement measuring device 112 (x) is a device for measuring the displacement of the steel structure at a specific position. For example, a laser displacement meter is combined with a control device, and an operating transformer type contact displacement meter is combined with an amplifier. It can be realized with things.
The displacement measuring device 112 (x) continuously measures the displacement at a specific position and stores the measured displacement as a voltage or current in the storage device 12.
It has the function of outputting to 0. The displacement measuring instrument 112 (x) may be installed at least at one location if there is only one fatigue crack generation location in advance and the direction of the displacement (deflection) caused by the crack generation is clear. There are many, and it is difficult to identify the location of fatigue cracks and the direction of displacement (deflection) that occurs with the occurrence of cracks.
And 2 to improve the accuracy of the crack initiation life
It is preferable to install the above.

<Outline of Configuration and Operation of Storage Device 120> The storage device 120 is a measurement period measuring device 121 having a timer function.
Hold it by yourself (replace the "time measuring device" in Fig. 3 with a "measuring period measuring device") and stress or strain measuring instruments 111 (1), 111 (2), ... 111 (y) and It has a function of storing the displacement measuring devices 112 (1), 112 (2), ... 112 (x) in synchronization with the electric signals output at the same timing. Stress or strain measuring instrument 111 (1), 111
(2), ... 111 (y) and displacement measuring instruments 112 (1), 112
(2), ... The electric signal output from 112 (x) is continuous, and it is desirable to record data for the longest possible operating time of the steel structure. If the sampling is difficult, the operating time of the measuring instrument is measured by a timer. In addition, the above-mentioned recorded stress or strain and displacement can be calculated online or offline.
Output to 130. The storage device 120 can be realized by a data recorder, a computer having an A / D conversion function, or the like.

<Outline of Configuration and Operation of Calculation Device 130> The calculation device 130 receives as input the continuous data of the stress or strain and the displacement output from the storage device 120, and receives at least one stress or strain and the displacement. Relationship, preferably for all combinations of stress or strain of 2 or more and displacement of 2 or more, the slope in the relationship of stress or strain and displacement, that is, the compliance is calculated by the calculation software 131, and the time when the compliance starts to change is calculated. The fatigue crack occurrence life is judged by the life judgment software 132. Thus, by using at least one relationship between stress or strain and displacement, preferably stress or strain at multiple locations, and displacement, and using a means to determine the varying life of compliance in these combinations, It is possible to easily detect a place where a fatigue crack occurs and a life in a steel structure including many welded portions where a fatigue crack easily occurs. In addition, the fatigue crack detection accuracy can be adjusted by changing the threshold value of the amount of change in compliance in which it is determined that a fatigue crack has occurred.

Further, the calculation device 130 calculates the stress amplitude or strain amplitude and its frequency by the frequency calculation software 133 from the set of sequential data of stress or strain. As a method for calculating the frequency distribution of stress amplitude or strain amplitude, for example, methods such as the rainflow method and the range pair method have been proposed. Commentary ", Gihodo Publishing, 19
Published April 25, 1993, p.261-264). The frequency of stress or strain amplitude is calculated by these calculation algorithms. Further, in the life calculation software 135, the fatigue damage degree D and the residual fatigue life N of the steel structure are calculated from the stress or strain amplitude frequency and the fatigue life database 134 using the following linear damage law.

[0028]

[Equation 1]

Since the above equations (1) and (2) are the fatigue damage degree and the remaining fatigue life obtained from the stress or strain during the measurement period, the life calculation software 135 further indicates the remaining fatigue life within the actual operating time. Convert to. It can be considered that the fatigue damage degree D is damaged when the fatigue damage degree D reaches a constant value C, but generally, the fatigue life has a very large variation. In the present invention, further, in the life correction software 136, the remaining fatigue life is obtained by comparing the crack initiation life determined by the crack initiation life determination software 132 and the fatigue life database 134, and the lifetime calculation software 135
It is corrected by comparing with the residual fatigue life obtained in. When the crack initiation life is detected in this way, a more accurate residual fatigue life can be obtained by correcting the fatigue life. In particular, when the life of the actual structure varies toward the short life side, it is possible to prevent the estimation of the remaining life on the dangerous side by making a correction according to the detected crack occurrence life.

<Overall Operation of Fatigue Life Estimation System 100>
FIG. 4 is a flowchart showing the overall operation of the fatigue life estimation system 100. First, the stress or strain and the displacement of the welded portion of the steel structure in the operating state are continuously measured by the stress or strain measuring device 111 and the displacement measuring device 112 (step S41). These data are output to the storage device 120 and sequentially stored together with the measurement period (step S42).

Next, from the above data, the calculation device 130 calculates the combinations of the inclinations in the relationship between the stress or strain and the displacement by the inclination calculation software 131 (step S43), and then the crack initiation life determination software.
The time series change of these compliances is calculated by 132, and the time when there is a change exceeding the threshold value is detected as the fatigue crack initiation life (step S44).

On the other hand, also in the calculation device 130, the frequency of the stress amplitude or strain amplitude is calculated from the stress or strain data by the frequency calculation software 133 (step S4).
6), the fatigue damage level D and the remaining fatigue life N are calculated by the equation (1) by comparing the fatigue life data previously extracted from the fatigue life database 134 with the life calculation software 135.
It is calculated by the equation (2) (step S47). On this occasion,
From the relationship between the measurement period and the actual operating time, it is converted into the fatigue damage level during the actual operating time.

Further, in the life correction software 136, the remaining fatigue life is calculated from the comparison between the crack initiation life detected by the crack initiation life determination software 132 and the fatigue life database 134 (step S45), and the remaining fatigue life calculated by the lifetime calculation software 135. The fatigue life is compared and corrected (step S4).
8). As described above, according to the present invention, the presence or absence of fatigue cracks and the residual fatigue life can be estimated by measuring the stress or strain and the displacement of the welded portion of the steel structure.

Another object of the present invention is to supply a storage medium storing a program code of software for realizing the functions of the measuring instrument, the storage device and the calculation device of the present embodiment to the system or the device, and the system or the device. Needless to say, is also achieved by reading and executing the program code stored in the storage medium.
In this case, the program code itself read from the storage medium realizes the function of the present embodiment, and the storage medium storing the program code constitutes the present invention.

As a storage medium for supplying the program code, ROM, flexible disk, hard disk, optical disk, magneto-optical disk, CD-ROM,
CR-RW, magnetic tape, non-volatile memory card,
A DVD or the like can be used.

<Example> The present invention was applied to a traveling girder of an overhead crane in a factory in which fatigue fracture is a problem. A schematic diagram of the example is shown in FIG. The dimensions of the running girder are girder height 2500
mm, girder width 500 mm, span length 16000 mm, girder flange thickness 50 mm, web and stiffener thickness 20 mm. The crane traverses between five spans, but the invention was applied here to the one span that passes most. The span of the overhead crane is 20000 mm wide and its own weight is 250.
Tons.

One span of a running girder of 16000 mm is divided by stiffeners every 4000 mm, and each is welded to a flange and fillet. Further, the flange has an increased width at the center of the span and is joined by butt welding. As the crane travels, tensile stress acts on the lower flange, and there is a high possibility that fatigue cracks will occur in the fillet welds and butt welds. Therefore, in order to measure the strain of the welded portion of these flanges, 14 uniaxial strain gauges were attached near the toe (position 200 mm away from the toe). Strain gauges (1) to (10) are on the upper side of the lower flange and (11) to (1
4) was attached to the lower side. (1), (2), (5), (6), (9), (10)
Is near the toe of fillet weld, (3), (4), (7), (8) and (1
1), (12), (13), and (14) were attached near the toe of the butt joint. Strain gauges (11), (12), (13), (14) are
It was attached to the back side of (3), (4), (7), and (8) (below the lower flange). The strain gauge was attached so as to measure the strain in the direction along the longitudinal direction of the running girder. The strain gauge was connected to a dynamic strain amplifier via a bridge box, and the voltage output was connected to a data recorder for recording. The dynamic strain amplifier and recorder were mounted on the girder flange and fixed, and power was supplied from the ground using a power cord.

Also, the vertical displacement (deflection) of the running girder
A laser displacement meter was used to measure Use a laser displacement meter with a long focal length, about 12000m from the ceiling
Measured from the ground at a distance of m. There are 10 measurement positions, which are the same as the strain measurement positions. The displacement was measured with one laser displacement meter at the places where strain gauges were attached to the front and back. Also for the laser displacement meter, the voltage output from the displacement output device was recorded in the data recorder.

The above strain and displacement measurements were carried out for 91 days. The tape feed rate was kept constant, and the tape was exchanged so that data recording would not be interrupted during that time. Also, the measurement period was measured by the tape counter and the set feed rate.

Next, the strain and displacement measurement data stored on the data tape are loaded into a personal computer,
The slope of the relation between strain and displacement was calculated. The slope was calculated by performing linear regression on the relationship between the strain peak value and the displacement peak value applied on one day. A value that was 10% lower than the average value of the slopes for the first 10 days was determined as a threshold value, and when the threshold value was continuously decreased for 2 days, the crack initiation life was determined. Examples of inclination of displacement gauges 1, 3 and 5 with respect to strain gauge No. 5 are shown in Fig. 6 (a) to (c).
Figure 7 shows the changes in the inclination of displacement gauges 1-6. The inclinations when using displacement gauges 5 and 6 dropped below the threshold on days 88 and 90, respectively, and fatigue cracks were found near displacement gauges 5 and 6, that is, near the fillet welded joint. It is expected that it has occurred.

Further, from the strain gauge No. 5 which is in the vicinity of the displacement gauges 5 and 6 where fatigue cracks are assumed to occur,
Figure 8 shows the result of the rainflow method for the frequency distribution in the strain range. Fatigue damage is calculated by dividing the strain range into 100μ intervals as shown in Table 1, multiplying each by the longitudinal elastic modulus, and converting it into a stress range. The crack initiation life and rupture life corresponding to that stress range are calculated. The degree of fatigue damage was calculated from the regression diagram of the fatigue life data and the ratio of the frequency of the strain range to the crack initiation life and the fracture life. Fatigue life data used for calculation of crack initiation life and fracture life are as shown in the margin of Table 1, the relationship between the stress range and the crack initiation life in the ribbed cross fillet joint (non-load transfer type, plate thickness 50 mm), And the relationship between stress range and rupture life was used. Table 1 is a table showing an example of calculation of the degree of fatigue damage in the example of the present invention.

[0042]

[Table 1]

Furthermore, Table 2 shows the expected fatigue damage degree, the expected remaining fatigue damage degree, and the expected remaining life for the actual operation period (about 8 years and 3 months) including the measurement period (91 days).
Shown in. Table 2 is a table showing a calculation example of the residual fatigue life in the example of the present invention.

[0044]

[Table 2]

In the calculation of the expected residual fatigue damage degree and the expected residual life, it was assumed that the fracture occurred when the fatigue damage degree D became a constant value C = 1. According to the calculation based on the fatigue life database, there should be some residual life for the crack initiation life even at the end of the measurement, that is, the fatigue damage degree for the crack initiation life should also be less than 1, Since cracks have been confirmed to have been generated, the crack generation life was corrected. The results are shown in Table 3. Table 3 is a table showing correction of the residual fatigue life based on the crack initiation life in the example of the present invention.

[0046]

[Table 3]

In this example, since crack generation was observed during the measurement period (88th day), the fatigue damage degree for the crack generation life after the measurement period was corrected to a value exceeding 1. Therefore, it was judged that the fatigue crack initiation life exceeded the expected number of cycles. Therefore, the fatigue damage level, the residual fatigue damage level, and the residual fatigue life were also corrected to the shorter life side with respect to the fracture life. In this way, the life expectancy of the dangerous side was modified so that it would be more realistic by considering the occurrence of cracks.

[0048]

As described above, in the present invention, the stress or strain and the displacement are measured, the data and the measurement time are stored, and then the slope in the relation between the stress or the strain and the displacement, that is, the compliance is calculated. Then, the fatigue crack generation time is detected by the change in compliance, and the continuous data of stress or strain is converted into the frequency distribution of stress amplitude or strain amplitude, and the fatigue damage degree is calculated to calculate the remaining life. With such a configuration, it is possible to accurately estimate the fatigue life of a steel structure including many welded portions.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a slope (compliance) in a relationship between stress or strain and displacement.

FIG. 2 is an explanatory diagram of changes in compliance when a fatigue crack occurs in a welded portion.

FIG. 3 is a block diagram showing a configuration of a fatigue life estimation system according to an embodiment of the present invention.

FIG. 4 is a flowchart for explaining the operation of the fatigue life estimation system according to the embodiment of the present invention.

FIG. 5 is an explanatory diagram showing application to a fatigue life estimation system for a crane traveling girder in an example of the present invention.

FIG. 6 is a diagram showing an example of calculation of the inclination in the relation between the strain range and the displacement in the embodiment of the present invention, (a) an example of inclination calculation in the displacement gauge 1 and the strain gauge No. 5, (b)
Example of calculation of inclination in displacement gauge 3 and strain gauge No. 5,
(C) It is the figure which showed the example of calculation of the inclination in the displacement gauge 5 and the strain gauge No. 5.

FIG. 7 is a diagram showing a change in the slope during the measurement period in the relationship between the strain range and the displacement in the example of the present invention.

FIG. 8 is a diagram showing a frequency distribution of a strain range during a measurement period in the example of the present invention.

[Explanation of symbols]

100 Fatigue Life Estimation System 110 Measuring Devices 111 (1), 111 (2), ..., 111 (y)
Stress or strain measuring instrument 112 (1), 112 (2), ..., 112 (x)
Displacement measuring device 120 Storage device 121 Time measuring device 130 Calculation device 131 Inclination calculation software 132 Crack generation life judgment software 133 Frequency calculation software 134 Fatigue life database 135 Life calculation software 136 Life correction software

Claims (7)

[Claims] 1. A residual structure life estimation device for a steel structure welded portion for estimating a residual fatigue life of a steel structure welded portion, which continuously measures stress or strain and displacement of the welded portion. Or two or more measuring means, a storage means for storing the stress or strain and the displacement measured by the measuring means, a frequency calculation means for calculating the frequency of the amplitude of the stress or strain stored in the storage means, Stress or strain,
And a measurement period measuring means for measuring a measurement period during the displacement measurement, a slope calculating means for calculating a slope in the relationship between the stress or strain and the displacement, and determining a fatigue crack initiation life based on the change amount of the slope. Crack occurrence life determining means, a fatigue life database, a frequency of the amplitude of the stress or strain, a life calculation means for calculating the fatigue damage level and the remaining fatigue life based on the measurement period and the fatigue life database, and the fatigue A remaining fatigue life estimation apparatus for a welded portion of a steel structure, comprising: a life correction means for correcting the remaining fatigue life based on a crack initiation life. 2. The inclination calculating means is an inclination in the relationship between stress or strain and displacement for one or more combinations of at least one stress or strain measured at a weld and at least one displacement. The residual fatigue life estimation device for a welded portion of a steel structure according to claim 1, wherein 3. The crack generation life determining means makes a determination by comparing the amount of change in the inclination with a threshold value for determining the occurrence of cracks, and the threshold value can be changed according to the amount of change in the inclination. The residual fatigue life estimation device for a welded portion of a steel structure according to claim 1 or 2. 4. A fatigue life estimation system comprising a plurality of devices communicatively connected to each other, wherein at least one of the plurality of devices is a fatigue life estimation system according to any one of claims 1 to 3. A residual fatigue life estimation system for a welded portion of a steel structure, which is characterized by having a device function. 5. A method for estimating the residual fatigue life of a welded portion of a steel structure, comprising a measuring step of continuously measuring stress or strain and displacement of the welded portion for a certain period of time, and the measured stress or strain, and A storage step of storing the displacement, a measurement period measuring step of measuring a measurement period during the measurement of the stress or strain and the displacement, and a slope for calculating the slope in the relationship between the stress or the strain and the displacement from the stress or the strain and the displacement. Calculation step, a crack generation life determination step to determine the fatigue crack generation life based on the amount of change in the slope, a frequency calculation step of calculating the frequency of the amplitude of the stress or strain, the frequency of the stress or strain, fatigue A life calculation step for calculating the degree of fatigue damage and residual fatigue life from the life database and measurement period, and the fatigue crack initiation life and fatigue life data And a life correcting step of correcting the remaining fatigue life from the database, the method for estimating the remaining fatigue life of a steel structure welded portion. 6. A computer comprising the functions of the fatigue life estimation apparatus according to claim 1, the functions of the fatigue life estimation system according to claim 4, or the processing steps of the fatigue life estimation method according to claim 5. Program to run on. 7. A computer-readable storage medium in which the program according to claim 6 is recorded.