JP2006337144A - Fatigue life diagnostic method and diagnostic support device of bridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fatigue life diagnostic method for carrying out accurate maintenance on the basis of estimation by accurately estimating an endurance period, even by a unskilled person, concerning a structure, in particular, a bridge. <P>SOLUTION: The fatigue life diagnostic method comprises sticking a fatigue sensor 30, by selecting a proper part for measuring repeating stress, on the basis of the whole structure of the bridge, a detailed structure and an active load mounting state; recording the result by measuring the developed length of cracks in each fatigue sensor 30 after a prescribed period; estimating the degree of damage concerning each part, in accordance with an accumulated damage rule on the basis of recorded crack developed length; calculating the lifetime by estimating the actual lifetime of an object part from the degree of damage and subtract passage period; and estimating the actual fatigue lifetime concerning each part and the whole bridge, by comparing the residual lifes at each part. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for evaluating the remaining life due to fatigue of a steel or aluminum bridge using a simple and convenient fatigue sensor, and in particular, estimates the fatigue damage degree in a welded portion to obtain the life expectancy of the bridge. The present invention relates to a method and a diagnosis support apparatus used for the method.

In order to accurately and efficiently maintain and manage bridges and other structures, it is necessary to periodically diagnose the state of the structure or evaluate the performance to quantitatively grasp the remaining life and strength.
In particular, fatigue failure and yield strength deterioration are likely to occur in the welded portion, and the useful life of the entire structure is often influenced by the life and strength of the welded portion. Although many welds exist in the structure, the life of the structure itself can be substantially extended by repairing a weld that is severely deteriorated. Therefore, in order to manage the structure economically, it is required to correctly grasp the deterioration of each welded part in the structure such as a bridge or the remaining life individually.

Patent Document 1 diagnoses the state of bridges and other structures, quantitatively grasps the remaining life and proof stress, creates a database of the structure data file, and accurately assesses maintenance costs. A structure maintenance management system is disclosed.
In Patent Document 1, the state of a structure such as a bridge is evaluated by an inspector who has been trained, with the assistance of a structural expert, qualitative judgment based on visual inspection and the like, and objectively diagnoses the structure. It is described that the remaining life and proof stress characteristics of the product are quantitatively grasped and made into a database.

According to the disclosed method, the monitoring sensor is always attached to the bridge, and the stress or strain and other characteristics of the bridge are detected, and the abnormality is detected or the state is grasped. The inspector inspects, inspects or diagnoses the bridge using a diagnostic device connected to the monitoring sensor, and aggregates the results into a database. The structural specialist will respond to consultations in actual diagnosis and train inspectors.
In Patent Document 1, there is no explanation to the extent that it is possible to determine the state of the structure and the remaining life, and a trained inspector can perform visual inspection and the remaining structure with the assistance of a structural expert. Since there is a statement that the life expectancy and proof stress are to be grasped, it is necessary to make a judgment by relying on the ability of skilled human resources with advanced expertise. In addition, the final evaluation and determination are considered to be comprehensively performed by a structural expert based on a database.

Thus, conventionally, the existing damage was found by visual observation, or the fatigue damage degree for each local area was evaluated using an instrument in which a strain gauge was attached in the vicinity of the weld and a strain transducer was incorporated.
However, the fatigue damage diagnosis method using strain gauges is a method of diagnosing the entire bridge because there is a limit to the number of measurement points because the measurement cost per location is high, and the data must be processed electronically. It was not always appropriate. In addition, the strain gauge diagnosis has a large error because it relies on short-term measurement data.

The life of the welded part is affected by the stress actually applied to the part and the number of times as represented by a so-called SN curve. In addition, since the life is exponentially shortened when the stress becomes stronger, the degree of stress concentration occurring in the weld becomes an important problem.
Therefore, a sample piece formed of a material with known crack growth characteristics is attached to the measurement target position as an alternative sensor, and the degree of damage of the target member is estimated by evaluating the degree of damage for the easily observed sample piece. A fatigue sensor may be used.
Since such a sample piece is cracked while undergoing the same cyclic stress as the target member, the crack progresses and eventually breaks, so the degree of fatigue damage caused to the target member during the measurement period from the crack state Can be estimated. In particular, by using a member thinner than the target member or preliminarily scratching it, it can be used as a leading indicator of the degree of fatigue damage of the target member.

However, since the sample piece is large and has a limited installation location, it is difficult to apply it close to the stress concentration part, and the progress of crack generation depends on the state of application to the measurement position. There was a problem that the error in estimating the fatigue damage degree was large.
Therefore, when managing bridges etc. using sample pieces, there is a measurement error, so it is necessary to set a high safety factor. In order to ensure safety, it was necessary to carry out uneconomical management, such as replacing it early.

As disclosed in Patent Document 2, the present applicant has succeeded in developing an extremely small and easy-to-handle fatigue sensor.
This fatigue sensor is made by joining both ends of a broken piece made of metal foil to a small rectangular foil-shaped base that can be placed on the fingertip. The broken piece is thin with a transverse groove formed in the center. A slit having a predetermined length from one end and having a sharp end at the farthest is formed.
When a fatigue sensor is subjected to repeated stress, a crack is generated from the slit tip and the crack progresses in response to the repeated stress. Therefore, it is possible to estimate the actual state of repeated stress received during the measurement period from the crack length. it can. Since the slit has a sharp edge, the time to crack initiation is sufficiently short, and since the metal thickness of the slit is thin enough, the crack propagation time is also short, so it is possible to detect stress conditions sensitively based on the length of the crack. it can.

By attaching this fatigue sensor to the base material and observing the cracked state after a predetermined period of time, the state of stress actually applied to the base material portion can be detected with high sensitivity during that period. Since the broken piece is fixed on the foil-like base, even when it is affixed to the surface of the target member, it has a stable detection power against stress without being affected by the affixing state.
In addition, since this fatigue sensor is extremely small, the fatigue sensor can be affixed close to the welded portion, and the base material is actually received during the period if observed after a predetermined period after the application. Since the stress is understood, the actual life of the weld corresponding to the stress can be estimated. The remaining life of the weld can be estimated by subtracting the elapsed time from the actual life. In this way, the remaining life can be estimated for the designated weld.
However, even if it is possible to know the remaining life of individual welds and members, it is difficult to manage the fatigue damage degree of the entire bridge by itself.
JP 2001-306670 A JP 2001-281120 A

Therefore, the problem to be solved by the present invention is a fatigue life diagnosis for a structure, in particular, a bridge, even if it is an unskilled person, accurately estimating its useful life and performing accurate maintenance based on this estimation. Is to provide a method.
In particular, the present invention is to provide a method for diagnosing a fatigue life of a bridge by appropriately using the previously disclosed fatigue sensor and capable of sufficiently economical maintenance management while ensuring safety.

  In order to solve the above problems, a fatigue life diagnosis method for a bridge according to the present invention selects an appropriate part for measuring repeated stress based on the overall structure, detailed structure, and active load loading state of the bridge, and selects a fatigue sensor. , Measure the crack growth length in each fatigue sensor after a predetermined period, record the result, estimate the damage degree for each part according to the cumulative damage law based on the recorded crack growth length, and determine the target part from the damage degree The remaining life is calculated by subtracting the elapsed period, and the remaining life of each part is compared with each other and the actual fatigue life is evaluated for each part and the entire bridge.

  Further, in order to solve the above-mentioned problems, the bridge fatigue life diagnosis support device according to the present invention includes a bridge data file in which the entire structure, detailed structure, and active load loading state of the bridge are integrated, and an appropriate part according to the bridge data file. Is provided with a fatigue sensor that has been selected and affixed, and a measurement data file that records the results of measuring the crack growth length of each fatigue sensor after a predetermined period of time, and a cumulative damage law based on the crack growth length recorded in the measurement data file A damage degree file for recording the result of estimating the damage degree for each part according to the above, a remaining life data file for estimating the actual life of the target part, subtracting the elapsed period, and calculating and recording the remaining life data file The actual fatigue life of each part and the entire bridge is evaluated by comparing the remaining life of each part recorded in the remaining life data file. Characterized in that it.

According to the fatigue life diagnosis method and diagnosis support apparatus of the present invention, the overall structure and detailed structure of the bridge based on the bridge data file, and the active load loading state are referred to, and the entire fatigue damage is determined based on the state of the entire bridge. It is possible to select a member to be influenced or a welding part. A fatigue sensor is affixed to the selected part, and the crack growth length of the fatigue sensor measured after a predetermined period is stored in the measurement data file.
The fatigue sensor used in the present invention is formed by joining both ends of a broken piece made of metal foil to a rectangular foil-shaped base, and the broken piece is thinned with a transverse groove formed in the central portion. It is preferable that a slit having a predetermined length from the side end and having a sharp end at the back is formed. This fatigue sensor is used by adhering and fixing a foil-like base to a target site, and can estimate the stress acting on the target site from the state of a crack growing at the tip of the slit.

When stress concentration occurs in the material, it is preferable to attach a plurality of fatigue sensors along the stress gradient so that the concentration degree can be estimated. In the fatigue sensor, there is a correlation between the actual value of the repeated stress and the crack length in a predetermined period at the site where it is applied. The arithmetic unit calculates the fatigue damage degree for each part according to the cumulative damage rule using the crack growth length recorded in the measurement data file. The calculated fatigue damage degree data is stored in a damage degree file.
The calculation result is combined with the information stored in the bridge data file, edited in a form that is easy for humans to understand, and output through a display or a printer.

The remaining life of the bridge follows the shortest remaining life of the measurement site. Therefore, if the remaining life is extended by performing appropriate repairs such as repairs and replacement of parts and parts having the shortest remaining life, the remaining life of the bridge itself is also extended. For this reason, it is preferable to display the information regarding a member with a short remaining life so that an employee may call attention.
Note that the repeated load during the measurement period does not change over the entire service period. When the past live load loading state is known, the measurement value and the calculated value can be corrected and evaluated. Moreover, when the predicted value about the future is known, it can correct and utilize similarly.

The method of the present invention requires some expertise and skill to attach a fatigue sensor, but the evaluation of the fatigue sensor requires no special training because it can measure the crack growth length. In addition, the remaining life calculation is easy, and since the calculation function of an electronic computer is usually used, it is not necessary to use a skilled person.
In this way, some specialized knowledge is required when selecting the part where the fatigue sensor is to be attached to the target bridge, but other experts and skilled workers are not required, so many bridges are targeted. This is advantageous when implementing a project that accurately estimates the remaining life.

In addition, although the said invention is applied to a bridge, it cannot be overemphasized that the same method is applicable also to another structure, a ship, a vehicle, etc.
Moreover, although the fatigue sensor currently available for steel members and aluminum members is available, it is possible to measure any material by selecting the material of the fracture piece of the fatigue sensor. Therefore, if a suitable fatigue sensor is procured as necessary, a remaining life can be obtained for a structure formed of an arbitrary material including a composite material.

Hereinafter, the present invention will be described in detail based on examples with reference to the drawings.
FIG. 1 is a flowchart showing a procedure of a fatigue life diagnosis method for a bridge according to one embodiment of the present invention, and FIG. 2 is a block diagram showing a configuration of a fatigue life diagnosis support apparatus according to the present embodiment.
As shown in FIG. 1, the overall flow when performing a remaining life diagnosis using a fatigue sensor follows the planning, pasting, inspection, and evaluation steps in sequence.
The planning process 1 is a process of conducting a preliminary survey on the target bridge and the application site of the fatigue sensor, and determining the application position of the fatigue sensor based on the preliminary survey.
The sticking step 2 is a step of sticking the fatigue sensor to the determined sensor sticking position.
Inspecting step 3 is a step of confirming the state of attachment of the sensor and measuring the crack propagation length of the sensor at a fixed time.
The evaluation process 4 calculates the fatigue damage degree Ds of the sensor during a predetermined period based on the crack propagation length at of the fatigue sensor, refers to the service history, and accumulates the cumulative fatigue damage of the target part based on the traffic data so far This is a step of calculating the degree of fatigue and remaining fatigue life of each part according to future traffic volume prediction with reference to the service plan.

The remaining life diagnosis in this embodiment is efficiently performed using a support device configured as a computer system as shown in FIG.
In FIG. 2, the remaining life diagnosis support device 10 includes a bridge data file 11, a measurement site data file 12, a measurement data input device 13, a measurement data file 14, a damage degree file 15, a remaining life file 16, an arithmetic expression file 17, a calculation. It comprises a control device 18 and a data output device 19 such as a printer or a display device.
In addition, a design database 21, a pasting method database 22, and a service history / plan database 23 are provided outside, and data can be input as necessary.
The data output device 19 outputs a fatigue sensor handling manual 25 and a measurement result display screen 26 which are necessary for determining the remaining life. The measurement data input device 13 is a device for inputting crack length data observed for the fatigue sensor 30 affixed to various places on the bridge.

Hereinafter, each process is demonstrated in detail about the fatigue life diagnostic method of the bridge which concerns on a present Example using the remaining life diagnosis assistance apparatus 10. FIG.
In the planning process 1, the overall structure and microstructure information based on the design drawings and design documents of the target bridge, the live load loading history received by the bridge during the previous service period, and the future traffic volume based on the service plan Various information such as predictions is collected, and the fatigue sensor sticking position is determined using these information.
Also, on-site inspections will confirm the surrounding situation, confirmation of the access method to the fatigue sensor application site, confirmation of the fatigue sensor application position and orientation, and verification with design drawings such as plate assemblies. For access to the sensor attachment site, consideration should be given to means such as inspection roads, aerial work platforms, and installation of scaffolding. Since there is a case where there is a difference between the actual on-site and the design drawing, it is preferable to confirm the board assembly.

It is necessary to select an appropriate fatigue sensor application site based on the overall structure, detailed structure, live load loading state, and the like. The site where fatigue cracks are likely to occur can be estimated from past fatigue crack occurrence examples and fatigue damage maps. The fatigue sensor does not generate a fatigue crack at present, but it is preferable that the fatigue sensor is attached to a site where a crack is likely to occur.
In addition, when the fatigue sensor is reinforced against fatigue damage, there is a utilization method in which the reinforced effect is confirmed by sticking to a reinforced part and detecting that the amplitude of repeated stress is small.

When the remaining life diagnosis support apparatus 10 is used, information on the shape and structure such as the entire structure and microstructure of the bridge to be subjected to the remaining life diagnosis is taken from the design database 21 and stored in the bridge data file 11. Information lacking in the design database 21 is collected by other means and stored in the bridge data file 11. The data to be collected should include both design data and construction data for each weld. In addition, information obtained through field surveys in advance is organized and recorded in the bridge data file 11.
The design database 21 may store CAD data. The CAD data can be directly taken into the bridge data file 11 without going through the arithmetic and control unit 18.

Based on the information stored in the bridge data file 11, a measurement position where a measurement effect can be expected is determined, and the result is stored in the measurement site data file 12.
By examining design drawings and the like, it is possible to estimate the fatigue strength and life of the target welded joint based on a predetermined fatigue strength grade. In addition, referring to past fatigue crack occurrence examples and fatigue damage maps, a specific part where fatigue cracks are likely to occur, such as a stiffener (stiffener), is found. As a result, a fatigue sensor is affixed to determine a portion for evaluating the remaining life.

In addition, if the type of bridge is determined, members and positions with a short fatigue life can be understood to some extent from experience. For example, stress concentration occurs at the weld toe at the welded joint, and it is easy to break. In a railway bridge, the fatigue of the stiffener especially under the sleepers and near the rail joint is remarkable. Further, since the load is concentrated on the sole plate, the fatigue is large. Therefore, in order to see the fatigue life of the entire bridge, it is necessary to grasp the fatigue state of these particularly easily fatigued members.
Portions where fatigue failure is likely to occur in the bridge structure can be automatically detected and enumerated based on the data of the entire structure and microstructure. If the screening algorithm is not reliable, it is safe to enumerate the candidates and have the engineers confirm them.

FIG. 3 is a diagram illustrating an example of an upper plate girder type railway bridge, and FIG. 4 is a diagram illustrating a plate girder type road bridge with circles of places where fatigue sensors are attached. FIG. 5 is a partial perspective view illustrating the state of attachment of the fatigue sensor in the welded portion. As shown in FIG. 5, it is preferable to attach a fatigue sensor along a stress gradient to a portion where stress concentration is likely to occur, such as a toe portion or a butting position of a plurality of members, even in a welded portion.
The obtained measurement site list is stored in the measurement site data file 12.
The fatigue life diagnosis support device 10 outputs a sensor handling manual 25 via an output device 19 such as a display or a printer in order to inform the worker of the position to attach the fatigue sensor. In the sensor handling manual 25, the matters to be noted in sensor pasting are extracted from the pasting method database 22, and are necessary for the pasting process and the inspection process such as the type of fatigue sensor to be used, the fatigue sensor pasting position, the posture, and the inspection time. It is preferable to describe such matters.

In the pasting step 2, an engineer who fully understands the pasting procedure sticks the fatigue sensor to a designated place. The fatigue sensor 30 is affixed in a state where an operator is designated at a designated position on the bridge in the field according to the sensor handling manual 25. The fatigue sensor 30 can be applied in the same order as the strain gauge in the order of removal of the coating film, cleaning, application, and protective measures, but the structure is slightly more complicated than that of the strain gauge. Alternatively, it is preferable to receive training.
The affixed location is accessed using an inspection road, an aerial work platform, a scaffold, etc., and affixed and inspected.

The inspection process 3 is performed after a predetermined period. In the fatigue sensor 30, an operator checks the state and measures the crack length every predetermined period, and inputs the collected crack length of each fatigue sensor from the measurement data input device 13.
Usually, for example, the inspection is performed three times after one month, three months, and six months. Of these, the first inspection is to confirm that the fatigue sensor is properly attached. The crack growth length of the sensor is measured at the second and third inspections. When there are special circumstances, the inspection timing and frequency can be adjusted appropriately. The crack growth length is measured using a magnifying glass method, a replica method, a CCD camera method, or the like. In practice, a method using a replica is preferred because measurement can be performed with high accuracy and recording remains.
The measurement data input device 13 can use various input devices such as a keyboard, an IC card reader, or a device for inputting via a USB memory. The input measurement data is stored in the measurement data file 14.

In the evaluation process 4, based on the crack growth length of the fatigue sensor, the actual life of the target part such as a welded part is estimated by knowing the situation of the repeated stress during a predetermined period, and the service history and service plan are referred to. The fatigue life expectancy is calculated for each part.
In the remaining life diagnosis support apparatus 10, the arithmetic and control unit 18 calls a necessary mathematical expression from the arithmetic expression file 17, first calculates the damage degree of each part from the data of the measurement data file 14 and stores it in the damage degree file 15. . Next, the damage degree is read from the damage degree file and processed, the actual life of each part is calculated, and the remaining life is calculated for each part by considering the past service history and the future service plan. To store. The service history and service plan information can be acquired from the service history / plan database 23.

FIG. 6 is a perspective view showing an example of a fatigue sensor used in this embodiment.
The fatigue sensor 30 used in the present embodiment is, for example, a sensor whose technical idea is disclosed in Patent Document 2, and as representatively shown in FIG. 6, invariant steel (invar), polyimide film, etc. On a thin base 31 made of a material having high dimensional stability against heat, for example, a thin base 31 having a thickness of 0.05 mm, for example, a foil-shaped metal fracture piece 32 having a thickness of, for example, 0.1 mm and having a groove portion 33 in the transverse direction. Only the both ends are fixed to the base.
The size of the broken piece 32 is extremely small, for example, 12 mm long and 5 mm wide. Further, the groove 33 at the center of the broken piece has a width of 1 mm and a thickness of 0.02 mm, for example, and the groove 33 is formed with a slit 34 of an appropriate length having a sharp end at the innermost part in the direction from the one end to the central axis. Has been.

When repeated stress is applied in the axial direction of the fatigue sensor 30, a crack is generated in the groove 33. In the case of an ordinary member, a crack should occur after a long crack generation period, and then there should be a crack propagation period in which the crack develops. However, since this fatigue sensor 30 has a slit 34 having a sharp edge, There are almost no cracks and a crack is immediately generated from the slit tip and propagates in the transverse direction. As clarified in Patent Document 2, the crack growth length a is proportional to the number of repetitions N if the stress σ is constant.
In addition, since the fracture piece 32 is obtained by forming a thin foil using a material corresponding to the crack propagation characteristics of the base material, when the fracture piece 32 is affixed to the base metal welded portion, the groove portion 33 of the fracture piece 32 is obtained. The mechanism by which cracks propagate is the same as when cracks propagate in the weld of the base metal. Therefore, there is a predetermined relationship between the crack growth of the two, and when the SN diagram representing the fatigue life is made using the stress σ and the number of repetitions N as a logarithmic scale, the two become substantially parallel lines.
Since the fatigue sensor 30 is sufficiently small, it can be affixed in the very vicinity of a region where stress concentration occurs in the target member. Moreover, the stress concentration degree can also be detected by arranging and attaching a plurality of sensors in the middle of the stress gradient as necessary.

FIG. 7 is an explanatory diagram in which an SN diagram of a fatigue sensor and a welded portion is drawn together.
FIG. 7 is an SN diagram in which the vertical axis is a logarithmic scale of the stress σ, the horizontal axis is a logarithmic scale of the repetition number N, the fatigue life of the welded portion is indicated by a dotted line, and the life of the fatigue sensor 30 is indicated by a solid line. is there. Note that the SN diagram of the target region is preferably analyzed using both the average line and the design line. The average line is a diagram representing the fatigue life when the non-destructive probability is 50.0%, which is the average of the variation in fracture, and the design line is fatigue when the non-destructive probability is 97.7%, which is the lower limit of the variation of fracture. It is a diagram showing a lifetime.
The SN diagram of the member of the structure is almost a straight line, and the inclination becomes steeper as the degree of stress concentration increases. The SN diagram of the weld has the largest slope. Since the fatigue sensor disclosed in Patent Document 2 is a slit having a sharp end, the SN diagram has the same inclination as the SN diagram in the weld, and is separated by Δ from the SN diagram of the weld in the figure. Parallel lines.

That is, between the fatigue sensor life Ts (to be exact, the allowable number of repetitions Ns) and the weld life Tm (to be exact, the allowable number of repetitions Nm),
logNm−logNs = log (Nm / Ns) = Δ
The relationship is established.
Here, if log α = Δ, the allowable number of repetitions Nm of the member is
Nm = αNs
It is obtained with.

Therefore, when an SN diagram is given, the fatigue life Tm of the welded part in the same live load loading state is estimated by multiplying the fatigue life Ts shown in the live load loading state actually accepted by the fatigue sensor by the constant α. it can.
Further, by subtracting the service period Th from the fatigue life Tm of the welded part to the time of diagnosis, the period until the end of the life, that is, the remaining life Tr can be obtained.
That is,
Tr = Tm-Th
It is.

Since there are a plurality of types of fatigue sensors having different sensitivities, the fatigue sensors can be selectively used according to the size of the applied site and the estimated stress amplitude, or fatigue sensors having different sensitivities can be used in combination.
The fatigue sensor Sb having high sensitivity has a shape in which the inclination of the SN diagram does not change and shifts in parallel with the direction in which the allowable number of repetitions Nsb decreases, so that the value of the difference Δb from the SN diagram of the welded portion increases. The coefficient α to be multiplied to estimate the fatigue life Nm of the member to which is attached is increased.

Furthermore, in order to estimate the fatigue life of the member in detail, there is a method of using the damage degree D based on the crack length of the fatigue sensor.
FIG. 8 is a plan view showing a state in which a crack of the fatigue sensor progresses. A slit 33 is formed from one end of the groove 33 formed in the center of the broken piece 32 fixed on the base 31. When the repeated stress is applied, a crack 35 is generated from the tip of the slit 34 and progresses as the number of repetitions increases.
As shown in FIG. 8, if the crack length becomes at during the measurement period Tt, the total length of the crack is a0, and the damage degree (damage) Ds of the fatigue sensor is
Ds = at / a0
It is expressed. The damage degree Ds is an index representing 0 when there is no damage and 1 when it is destroyed.

Even when the stress σ is not constant, the damage degree can be calculated by accumulating the number of loads for each stress (cumulative damage law).
According to the cumulative damage law, for stresses σ1, σ2,... Where the number of loads leading to fracture is Ns1, Ns2,..., The number of loads during the measurement period Tt is n1, n2,. For example, the damage degree Ds is
Ds = n1 / Ns1 + n2 / Ns2 +... = Σ _i (ni / Nsi)
It is represented by That is, the damage degree Ds corresponds to the load state that has been recorded by the fatigue sensor in a proportional relationship.

On the other hand, since the welded part to be measured receives the same load as the fatigue sensor in the same measurement period Tt, the number of repeated fractures corresponding to each stress is expressed as Nm1, Nm2,. Then, the damage degree Dm is determined by the cumulative damage law.
Dm = n1 / Nm1 + n2 / Nm2 +... = Σ _i (ni / Nmi)
It is expressed.
Since Nm = αNs as described above with reference to FIG.
Dm = Σ _i (ni / Nmi) = Σ _i (ni / αNsi)
It becomes. That is,
Dm = Ds / α
The damage degree Dm of the welded portion that occurs during the measurement period is 1 / α times the damage degree Ds that occurs in the fatigue sensor.

Since the fatigue life Tm of the welded portion is the time until the damage degree Dm becomes 1, the measurement time Tt
Tm = Tt / Dm = αTt / Ds
It becomes. Furthermore, assuming that the service period of the welded part is Th, the remaining life Tr of the welded part is
Tr = Tm−Th = αTt / Ds−Th
Can be obtained.

Based on the information stored in the measured part data file 12, the part that is the target of the remaining life calculation is checked for the specific position and posture of the fatigue sensor, and the relationship between the measurement result and the stress state of the target part is determined. It is necessary to determine the lifetime.
In addition, when it is known that the load of the inspection period in the part subject to the remaining life calculation is different from that in the previous service period, the remaining service life is calculated by correcting the service period Th according to the degree. Have to do. Further, when a load state different from the current state is predicted, such as an increase in traffic volume in a future service plan, it is necessary to calculate the remaining life Tr in the same manner.
The service history and service plan of the welded portion can be obtained from the service history / plan database 23.
These equations are stored in the arithmetic expression file 17 and are called up and used as necessary.

The obtained remaining life data for each part is arranged so that it can be easily judged, and is output in a table format via a display or a printer.
FIG. 9 shows an output example of the measurement result. The result of estimating the remaining life based on the design line and the remaining life based on the average line is shown for the site based on the crack length of the fatigue sensor attached to each site.
For parts where cracks did not occur during the application period of the fatigue sensor, the life given based on the fatigue strength grade defined by the Japan Steel Structure Association or the like is adopted.

The life of the entire bridge is constrained by the member with the shortest life, so if maintenance work is performed from a member with the shortest life and replaced with a new member, it can be extended to the life of the member with the next shortest life. .
The fatigue sensor used in this embodiment is small and inexpensive, and does not use special measurement equipment, so it can be installed at many locations in the bridge. For this reason, although a highly reliable diagnosis is possible, it is difficult to find the shortest remaining life part at a glance only by displaying the result in a table format as illustrated in FIG. 9, and there is a risk of overlooking important data. is there. Therefore, by utilizing the structure data stored in the bridge data file 11 and expressing the image, it is possible to find a problem part intuitively and without oversight.

  By using the analysis result obtained by the fatigue life diagnosis method of the bridge of the present invention, it is possible to accurately determine which member should be repaired by when. It is possible to save an unnecessary maintenance cost such as exchanging parts, and to perform efficient maintenance work.

It is a flowchart which shows the procedure of the fatigue life diagnostic method of the bridge concerning one Example of this invention. It is a block diagram showing the structure of the fatigue life diagnosis assistance apparatus which concerns on a present Example. It is drawing which illustrated the place which attaches a fatigue sensor about a railway bridge in the fatigue life diagnostic method of a present Example. It is drawing which illustrated the place which attaches a fatigue sensor about a road bridge in the fatigue life diagnostic method of a present Example. It is a fragmentary perspective view which illustrates the sticking condition of the fatigue sensor in a welding part in the fatigue life diagnostic method of a present Example. It is a perspective view which shows the example of the fatigue sensor utilized for the present Example. It is explanatory drawing which drew together the SN diagram of a fatigue sensor and a welding part. It is a top view which shows the crack progress state of the fatigue sensor in a present Example. It is. It is drawing which shows the example of an output of the measurement result in a present Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Planning process 2 Pasting process 3 Inspection process 4 Evaluation process 10 Remaining life diagnosis support apparatus 11 Bridge data file 12 Measurement site data file 13 Measurement data input device 14 Measurement data file 15 Damage degree file 16 Remaining life file 17 Calculation formula file 18 Calculation Control device 19 Data output device 21 Design database 22 Pasting method database 23 Service history / plan database 25 Fatigue sensor operation manual 26 Measurement result display screen 30 Fatigue sensor 31 Base 32 Fragment 33 Groove 34 Slit

Claims (4)

Select an appropriate site for measuring cyclic stress based on the overall structure, detailed structure, and live load state of the bridge, attach a fatigue sensor, and measure the crack propagation length in each fatigue sensor after a predetermined period. Record the results, estimate the degree of damage for each part according to the cumulative damage law based on the recorded crack growth length, estimate the actual life of the target part from the degree of damage, subtract the elapsed period, calculate the remaining life, A method for diagnosing a fatigue life of a bridge, characterized by evaluating the fatigue life of each part and the entire bridge by comparing the remaining lives of the respective bridges. The fatigue sensor is formed by joining both ends of a broken piece made of metal foil to a rectangular foil-shaped base, and the broken piece is thinned with a transverse groove formed in the center, and one end of the transverse groove is formed in the transverse groove. 2. The fatigue life diagnosis method according to claim 1, wherein a slit having a predetermined length and having a sharp end at the back is formed. It is equipped with a bridge data file that integrates information on the overall structure, detailed structure, and live load loading state of the bridge, and is equipped with a fatigue sensor that is attached by selecting an appropriate part according to the information stored in the bridge data file for a predetermined period. It is equipped with a measurement data file that records the results of the measurement of the crack growth length in each fatigue sensor later, and records the results of estimating the damage degree for each part according to the cumulative damage law based on the crack growth length recorded in the measurement data file. A remaining life data file for estimating the actual life of the target part, subtracting the elapsed period and calculating and recording the remaining life, and recording the remaining life of each part recorded in the remaining life data file Fatigue life of a bridge characterized by comprising an arithmetic and control unit that evaluates the fatigue life of each part and the whole bridge by comparison Diagnosis support apparatus. The fatigue sensor is formed by joining both ends of a broken piece made of metal foil to a rectangular foil-shaped base, and the broken piece is thinned with a transverse groove formed in the center, and one end of the transverse groove is formed in the transverse groove. 4. A fatigue life diagnosis support apparatus according to claim 3, wherein a slit having a predetermined length and a sharp end at the back is formed.

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