CA2851725A1 - Method for determination of the stability of a mast that has been properly set up at an installation site - Google Patents
Method for determination of the stability of a mast that has been properly set up at an installation site Download PDFInfo
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- CA2851725A1 CA2851725A1 CA2851725A CA2851725A CA2851725A1 CA 2851725 A1 CA2851725 A1 CA 2851725A1 CA 2851725 A CA2851725 A CA 2851725A CA 2851725 A CA2851725 A CA 2851725A CA 2851725 A1 CA2851725 A1 CA 2851725A1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M5/00—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings
- G01M5/0041—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings by determining deflection or stress
- G01M5/005—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings by determining deflection or stress by means of external apparatus, e.g. test benches or portable test systems
- G01M5/0058—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings by determining deflection or stress by means of external apparatus, e.g. test benches or portable test systems of elongated objects, e.g. pipes, masts, towers or railways
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H13/00—Measuring resonant frequency
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M5/00—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings
- G01M5/0066—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings by exciting or detecting vibration or acceleration
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/04—Analysing solids
- G01N29/045—Analysing solids by imparting shocks to the workpiece and detecting the vibrations or the acoustic waves caused by the shocks
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- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Aviation & Aerospace Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
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- Acoustics & Sound (AREA)
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- Pathology (AREA)
- Testing Of Devices, Machine Parts, Or Other Structures Thereof (AREA)
Abstract
The invention relates to a method for determining the stability of a mast that has been properly installed at an installation site, wherein the oscillation spectrum of the mast that is artificially induced or induced by environmental influences to oscillate is recorded and at least one natural frequency of the mast is determined therefrom.
Description
Method for determination of the stability of a mast that has been properly set up at an installation site The invention relates to a method for determination of the stability of a mast that has been properly set up at an installation site and attached to a substratum.
Furthermore, the invention relates to an apparatus for implementation of this method.
A corresponding method is known, for example, from WO
2010/128056 Al. The disclosure content of this international patent application is supposed to belong to the disclosure content of the present application, by inclusion.
Within the scope of the invention, a mast can be an essentially = vertically oriented support, for example for lighting fixtures, traffic signs, traffic lights, cables, antennas, sign gantries, or the like.
Such masts can be damaged, for example by environmental influences, accidents or vandalism, so that the stability of a mast can be in danger for example due to corrosion, material
Furthermore, the invention relates to an apparatus for implementation of this method.
A corresponding method is known, for example, from WO
2010/128056 Al. The disclosure content of this international patent application is supposed to belong to the disclosure content of the present application, by inclusion.
Within the scope of the invention, a mast can be an essentially = vertically oriented support, for example for lighting fixtures, traffic signs, traffic lights, cables, antennas, sign gantries, or the like.
Such masts can be damaged, for example by environmental influences, accidents or vandalism, so that the stability of a mast can be in danger for example due to corrosion, material
2 fatigue, or crack formation. The term stability particularly covers, in the sense of the invention, the possibility that persons who must undertake repair, maintenance, or installation work on the mast, for example, can climb the mast. Methods for determination of the stability of masts, therefore fulfill the purpose, in the sense of the invention, among other things, of checking the mast just before someone climbs it, in order to determine whether or not climbing the mast is safe. Independent of this, it is necessary to check the stability of a mast at regular intervals, in order to be able to determine in timely manner whether the stability is impaired to such an extent that a mast must be replaced.
It is the task of the invention to make available a novel method for determination of the stability of a mast properly set up at an installation site, which reliably and very accurately allows a determination of the stability of the mast.
This task is accomplished, in a method of the type stated initially, in that the vibrations, for example in the form of the vibration spectrum of the mast, excited to vibrate artificially or by means of environmental influences, are detected, and at least one natural frequency of the mast is determined from this.
It is the task of the invention to make available a novel method for determination of the stability of a mast properly set up at an installation site, which reliably and very accurately allows a determination of the stability of the mast.
This task is accomplished, in a method of the type stated initially, in that the vibrations, for example in the form of the vibration spectrum of the mast, excited to vibrate artificially or by means of environmental influences, are detected, and at least one natural frequency of the mast is determined from this.
3 An essential aspect of the invention is that a non-linearity of the vibration behavior of the excited mast is analyzed. On the basis of the result of this analysis, it can be directly determined whether damage to the mast and/or to its attachment in the foundation region is present.
A non-linearity of the vibration behavior can express itself, for example, in a dependence of the vibration frequency on the vibration amplitude. This dependence can be analyzed directly and very easily. This dependence in turn can be used as an indicator for a "healthy," i.e. intact, or an "unhealthy," i.e.
damaged mast foundation.
Preferably, the dependence of the vibration frequency on the vibration amplitude is determined for the analysis of possible non-linearities of the vibration behavior. On the basis of this dependence, a calibration frequency can then be derived, with which a mechanical (static and/or dynamic) model of the mast, determined in advance (for example as described in the document WO 2010/128056 Al cited above) is calibrated, whereby the rigidity of the mast is then determined on the basis of the calibrated model.
A non-linearity of the vibration behavior can express itself, for example, in a dependence of the vibration frequency on the vibration amplitude. This dependence can be analyzed directly and very easily. This dependence in turn can be used as an indicator for a "healthy," i.e. intact, or an "unhealthy," i.e.
damaged mast foundation.
Preferably, the dependence of the vibration frequency on the vibration amplitude is determined for the analysis of possible non-linearities of the vibration behavior. On the basis of this dependence, a calibration frequency can then be derived, with which a mechanical (static and/or dynamic) model of the mast, determined in advance (for example as described in the document WO 2010/128056 Al cited above) is calibrated, whereby the rigidity of the mast is then determined on the basis of the calibrated model.
4 This method can be used for masts made of the most varied materials and the most varied shapes. It can be used, for example, in the case of a mast configured conically or in stepped shape, with a cross-sectional jump. Furthermore, the method can be used not only for posts, posts in water or overhead line masts, but also for other mast types such as, for example, whip masts, outrigger masts, traffic light masts, double masts, A masts, lattice masts, traffic sign gantries, and simple frames.
An artificial excitation of the mast can take place using .a hammer, using a cable, if necessary an imbalance exciter, or the like. Also, an artificial excitation of the mast can take place manually. The determination of the stability according to the method according to the invention is based not solely on a comparison of theoretical rigidities with a rigidity derived from a measurement. Instead, deformations as the result of external influences such as, for example, wind loads or man loads of the mast are calculated using a calibrated preferably numerical model of the mast established in advance, and then compared with limit values. In this way, a very individual determination of the stability of a mast is possible. This evaluation is not only mast-specific, but also dependent on the type of stress. Thus, for example, not only the stability with õ
regard to rated loads (generally wind loads) but also the stability with regard to a person climbing it (man loads) can be evaluated.
The following points are important within the scope of the present invention:
As has been mentioned, a calculation of the amplitude dependence of the at least one natural frequency and, based on that, a calculation of the decisive natural frequency for the stability evaluation can take place.
Furthermore, the foreseeable useful lifetime can be calculated in non-linear manner for masts, based on a velocity of damaging effects that is obtained from the measurement results. In this connection, an increase in precision (i.e. an improvement in the accuracy) of the results can take place, starting with the = second measurement.
By providing a link, a read-in possibility for characteristic mast data from Excel files or a database, for example, can be provided.
Automatic localization of masts using available GPS data and an assignment of mast data from databases can take place. The wood moisture can be predetermined as a function of the date, in each instance, and automatically be converted to the measurement time point.
A routine for identification of cable frequencies in the case of masts carrying cables and for automatic determination of mast frequencies can be used.
The cable hang can automatically be determined or calculated from tables. The dependence of the hang of the cable on the temperature in the environment of the cables can be taken into consideration. In a calculation program, a selection possibility can be provided as to whether the cable hang and/or the dependence of the hang on the temperature should be automatically predetermined or input.
A relationship between or the ratio of rotational spring rigidity and overall rigidity (see WO 2010/128056 Al) for an evaluation of the damage source (shaft or foundation) can be used, taking into consideration the amplitude dependence of the natural frequencies. , The distance between the first natural frequencies and the values of other natural frequencies can be analyzed. From this, it is possible to draw conclusions concerning further system parameters.
The method can also be used for glass fiber reinforced plastic masts, taking into consideration the special characteristic material data for glass fiber reinforced plastics.
The method can also be used for the evaluation of attached parts (for example traverses). For this purpose, the natural frequency and vibration forms of the attached parts are determined either taken out of the remaining system (if there is sufficient uncoupling) or within the overall system (in the case of coupled vibration forms.
= The method can also be used for masts in bends of conductor routes.
One or more sensors that can be connected with the mast can be used for implementation of the method.
Multiple measured, dynamic characteristic values can be taken into consideration in the determination of stability, such as, for example, taking into consideration multiple natural frequencies and/or taking into consideration measured ordinates of vibration forms when using multiple sensors. Multiple dynamic characteristic values can be used when the search is related not only to foundation rigidity, for example, but also to information concerning the mast shaft, concerning regions with damaged locations, concerning the bearing capacity of individual rods in frameworks, etc.
The method can allow localization of system regions with identified weak points or damaged areas.
The method can fundamentally be used for masts having a very complex construction. Examples of this are projection arms with outriggers (traffic light mast or outrigger sign masts on highways), frames (sign gantry on highways or toll bridges), masts for overhead lines (railways, public transit), masts of cable cars, etc.
The method can fundamentally be used for masts of any kind, such as, for example, also framework masts (such as for overhead line masts of railways), or mobile radio masts, centrifugally cast concrete masts or floodlight masts (also with an angular cross-section at the foot).
Next, an exemplary embodiment for the analysis of non-linear vibration behavior by means of a determination of the dependence of the natural frequency of the mast determined from the vibration spectrum of the mast, on the vibration amplitude, will be explained:
First, a calculation of the natural frequency in the time range is undertaken. By means of this evaluation, any dependence of the natural frequency on the vibration amplitude that might be present can be determined. This dependence, in turn, can be used as an indicator for a "healthy" or an "unhealthy"
foundation. Furthermore, this evaluation possibility allows taking the difference between the dynamic and static modulus of elasticity into consideration, for example for the ground or also for wood as a material, which is important for the determination of the static rigidity values. This evaluation is particularly recommended for masts having markedly non-linear behavior.
First, the measured time recording of the acceleration values recorded at the mast after excitation, by means of an acceleration sensor, is bandpass-filtered. The frequency band is established from the standard evaluation, from the selected -- -natural frequency ( 20% of the selected natural frequency from the standard evaluation). In this way, disruptive components (noise or frequency components having higher natural frequencies) are eliminated from the time recording.
Using an identification routine, the envelope curves for the local maxima (upper envelope curve) and minima (lower envelope curve) are first calculated. These envelope curves are than also smoothed by means of approximating splines that have the same support points as the envelope curves (see Figure 1). In a further step, this routine then looks for the range in which no manual excitation takes place any longer and the .mast is vibrating freely until the vibration dies away. This range generally lies at the end of the time progression. This range is extracted (see Figure 2).
In the extracted decay range, the distances between the local maxima and the distances between the local minima as well as the related vibration amplitudes ypp,i (accelerations) are then calculated. The distances are the periods Ti of the time progression, from which frequency values fi = 1/Ti can then be calculated, section by section (per period i). The frequency can thereby be represented as a function of the acceleration vibration amplitude ypp. An example is shown in Figure 3.
The dependence of the frequency on the vibration amplitude determined in this way is then approximated using a potency function. This function is defined as follows:
f(2) = a = yb First, the quality of the adaptation is checked by way of an error value. If this error value is close to zero, practically no adaptation is present. For an error value close to 1, practically perfect adaptation is present. Preferably, approximations having error values less than 0.3 are not evaluated. In these cases, it is assumed that no dependence of the frequency on the amplitude exists.
If dependence is present (error > 0.3), the exponent b is analyzed:
If b < 0, a degressive dependence is present. This means that the frequency becomes smaller with an increasing amplitude.
This case indicates problems in the foundation, since a progressive dependence normally occurs there.
If b 0, a progressive dependence is present. In this case, the frequency increases with an increasing amplitude. This is the normal case, which is based, just like the modulus of elasticity, on the effect that during rapid movements in the ground, the water in the capillaries cannot be displaced just as quickly, and an apparent increase in rigidity of the ground occurs.
In both cases, a calibration frequency fa, which is used for calibration of the mathematical model of the mast and thereby for calculation of the deflections and deformations of the mast, is recalculated using the dependence of the natural frequency that was found. For these calculations, the following amplitudes are used;
, Value range Amplitude y for frequency Amplitude Consequence for co- calculation in the case dependence efficient b of amplitude dependence and frequency fa for evaluation 0Sb<0.01 f a=f a none none b>0.01 Ygrenz= 0.2-0. 2-2-(0.05.H) progressive Foundation OK
but frequency is fa=a = ygrenz b being reduced as compared with the value from the spectrum n -0.01b<0 Ygrenz=0 . 02-2- (0.05=H) weakly Foundation still OK but frequency i fa=a ' Ygren zb ' 0 . 952 degressive is being somewhat reduced as 0 I.) co compared with the value from the in H
spectrum I.) -0.02b<- Ygranz=0.02=2=(0.05-H) moderately Foundation should be watched, in 0.01 fa=a = Sigreazb = 0.92 degressive frequency is being reduced as I.) H
compared with the value from the a, spectrum a, , 1 b<-0.02 Ygrenz=0 . 02 -6)2- (0.05-H) strongly Foundation is probably damaged, H
f a=a- ' Sigrenzb ' 0 . 852 degressive frequency is being clearly reduced as compared with the value from the spectrum _ The limit amplitudes result from the spectrum, as a function of the mast height H above ground level and the natural circular frequency w from the spectrum.
For the case b < 0, it was assumed, in this connection, that proceeding from a maximal amplitude of 5% of the mast height, the quasi-static range of the decay curve is reached when the vibration amplitudes have decayed to 2% of the maximal amplitude. In this amplitude range, it is assumed that the dynamic rigidities correspond to the rigidities that occur in the case of quasi-stationary stress. The calibration frequency fa is then reduced once again as a function of the order of magnitude of the parameter b. These reduction factors are quasi safety factors that are supposed to absorb the uncertainties of this evaluation routine, among other things, in the case of degressive dependence. As a function of the order of magnitude of b, these factors correspond to reductions in rigidity by 5%
(f: -0.01 S b < 0), 10% (f: -0.02 S b < 0.01) or 15% (f: b < -0.02).
For the case b > 0.01, a smaller amplitude is used for calculation of the calibration frequency. This amounts to 20%
of the amplitude for the case b < 0.
The further calculation (for example according to WO 2010/128056 Al) then takes place using the calibration frequency fa. This frequency is generally less than or at most equal to the natural frequency fa determined from the spectrum.
According to another important aspect of the invention, the stability of a mast set up at an installation site, attached to a foundation, can be determined, whereby the vibration spectrum of the mast, excited to vibrate artificially or by means of environmental influences, is detected, and at least one natural frequency of the mast is determined from this, and whereby the useful lifetime of the mast is then determined on this basis.
For example, the residual useful lifetime can be estimated based on the results of the frequency measurements, as described below.
A useful lifetime is estimated for the mast, depending on the year of construction of the mast and/or depending on the calculated displacement or deflection or deformation and, if applicable, the class limits (as described, for example, in WO
2010/128056 Al).
In general, the measurements lead to the conclusion that the masts have greater displacements at the measurement time point than a perfect, "undamaged" mast. The causes for the greater displacements are, among others, due to the rigidity of the foundation (softer than in the case of a perfect mast) and by time-related factors that lead to a decrease in system rigidity.
Because no information concerning the mast properties at an earlier point in time are available during a first measurement on a mast, it is assumed that the mast was perfect, i.e. intact at the time of installation. From the assumption of system rigidity during the time period between installation and first measurement, a speed of rigidity decrease can thereby be derived. For this purpose, it is assumed that the mast is always clamped in place, and that changes in rigidity are caused only by a (time-dependent) reduction in cross-section. In this connection, it is assumed that the mast cross-section, i.e. the outside diameter, decreases from the outside to the inside at this speed. This assumption results from the consideration that according to various standards (for example DIN 4133), corrosion supplements have to be taken into consideration in the dimensioning of specific components. In principle, these corrosion supplements also describe a decrease in the statically relevant cross-section as a function of time. In the case of wooden masts, the reduction in cross-section results, for example, from shrinkage, rot or fungal infestation.
The diameter of the masts is thereby a function of time t:
d5(t) = de) - v. = t with da0 outside diameter at the time of installation d.(t)outside diameter at the time point t di inside diameter in the case of a circular ring cross-section v8 speed of decrease in the outside diameter in mm/year From the underlying mechanical model, the head point displacements of the mast El(t) can be calculated as a function of time, at an acting force (for example wind load typical for the location). A determination equation for v2 can thereby be obtained, because the variable v5 is the only unknown. The solution of this equation and the determination of v5 takes place by means of an iteration algorithm, for example. With this speed võ it can then be calculated at what point in time the permissible deformation Etna is exceeded. For this purpose, the time t is increased until the following equation has been met:
An artificial excitation of the mast can take place using .a hammer, using a cable, if necessary an imbalance exciter, or the like. Also, an artificial excitation of the mast can take place manually. The determination of the stability according to the method according to the invention is based not solely on a comparison of theoretical rigidities with a rigidity derived from a measurement. Instead, deformations as the result of external influences such as, for example, wind loads or man loads of the mast are calculated using a calibrated preferably numerical model of the mast established in advance, and then compared with limit values. In this way, a very individual determination of the stability of a mast is possible. This evaluation is not only mast-specific, but also dependent on the type of stress. Thus, for example, not only the stability with õ
regard to rated loads (generally wind loads) but also the stability with regard to a person climbing it (man loads) can be evaluated.
The following points are important within the scope of the present invention:
As has been mentioned, a calculation of the amplitude dependence of the at least one natural frequency and, based on that, a calculation of the decisive natural frequency for the stability evaluation can take place.
Furthermore, the foreseeable useful lifetime can be calculated in non-linear manner for masts, based on a velocity of damaging effects that is obtained from the measurement results. In this connection, an increase in precision (i.e. an improvement in the accuracy) of the results can take place, starting with the = second measurement.
By providing a link, a read-in possibility for characteristic mast data from Excel files or a database, for example, can be provided.
Automatic localization of masts using available GPS data and an assignment of mast data from databases can take place. The wood moisture can be predetermined as a function of the date, in each instance, and automatically be converted to the measurement time point.
A routine for identification of cable frequencies in the case of masts carrying cables and for automatic determination of mast frequencies can be used.
The cable hang can automatically be determined or calculated from tables. The dependence of the hang of the cable on the temperature in the environment of the cables can be taken into consideration. In a calculation program, a selection possibility can be provided as to whether the cable hang and/or the dependence of the hang on the temperature should be automatically predetermined or input.
A relationship between or the ratio of rotational spring rigidity and overall rigidity (see WO 2010/128056 Al) for an evaluation of the damage source (shaft or foundation) can be used, taking into consideration the amplitude dependence of the natural frequencies. , The distance between the first natural frequencies and the values of other natural frequencies can be analyzed. From this, it is possible to draw conclusions concerning further system parameters.
The method can also be used for glass fiber reinforced plastic masts, taking into consideration the special characteristic material data for glass fiber reinforced plastics.
The method can also be used for the evaluation of attached parts (for example traverses). For this purpose, the natural frequency and vibration forms of the attached parts are determined either taken out of the remaining system (if there is sufficient uncoupling) or within the overall system (in the case of coupled vibration forms.
= The method can also be used for masts in bends of conductor routes.
One or more sensors that can be connected with the mast can be used for implementation of the method.
Multiple measured, dynamic characteristic values can be taken into consideration in the determination of stability, such as, for example, taking into consideration multiple natural frequencies and/or taking into consideration measured ordinates of vibration forms when using multiple sensors. Multiple dynamic characteristic values can be used when the search is related not only to foundation rigidity, for example, but also to information concerning the mast shaft, concerning regions with damaged locations, concerning the bearing capacity of individual rods in frameworks, etc.
The method can allow localization of system regions with identified weak points or damaged areas.
The method can fundamentally be used for masts having a very complex construction. Examples of this are projection arms with outriggers (traffic light mast or outrigger sign masts on highways), frames (sign gantry on highways or toll bridges), masts for overhead lines (railways, public transit), masts of cable cars, etc.
The method can fundamentally be used for masts of any kind, such as, for example, also framework masts (such as for overhead line masts of railways), or mobile radio masts, centrifugally cast concrete masts or floodlight masts (also with an angular cross-section at the foot).
Next, an exemplary embodiment for the analysis of non-linear vibration behavior by means of a determination of the dependence of the natural frequency of the mast determined from the vibration spectrum of the mast, on the vibration amplitude, will be explained:
First, a calculation of the natural frequency in the time range is undertaken. By means of this evaluation, any dependence of the natural frequency on the vibration amplitude that might be present can be determined. This dependence, in turn, can be used as an indicator for a "healthy" or an "unhealthy"
foundation. Furthermore, this evaluation possibility allows taking the difference between the dynamic and static modulus of elasticity into consideration, for example for the ground or also for wood as a material, which is important for the determination of the static rigidity values. This evaluation is particularly recommended for masts having markedly non-linear behavior.
First, the measured time recording of the acceleration values recorded at the mast after excitation, by means of an acceleration sensor, is bandpass-filtered. The frequency band is established from the standard evaluation, from the selected -- -natural frequency ( 20% of the selected natural frequency from the standard evaluation). In this way, disruptive components (noise or frequency components having higher natural frequencies) are eliminated from the time recording.
Using an identification routine, the envelope curves for the local maxima (upper envelope curve) and minima (lower envelope curve) are first calculated. These envelope curves are than also smoothed by means of approximating splines that have the same support points as the envelope curves (see Figure 1). In a further step, this routine then looks for the range in which no manual excitation takes place any longer and the .mast is vibrating freely until the vibration dies away. This range generally lies at the end of the time progression. This range is extracted (see Figure 2).
In the extracted decay range, the distances between the local maxima and the distances between the local minima as well as the related vibration amplitudes ypp,i (accelerations) are then calculated. The distances are the periods Ti of the time progression, from which frequency values fi = 1/Ti can then be calculated, section by section (per period i). The frequency can thereby be represented as a function of the acceleration vibration amplitude ypp. An example is shown in Figure 3.
The dependence of the frequency on the vibration amplitude determined in this way is then approximated using a potency function. This function is defined as follows:
f(2) = a = yb First, the quality of the adaptation is checked by way of an error value. If this error value is close to zero, practically no adaptation is present. For an error value close to 1, practically perfect adaptation is present. Preferably, approximations having error values less than 0.3 are not evaluated. In these cases, it is assumed that no dependence of the frequency on the amplitude exists.
If dependence is present (error > 0.3), the exponent b is analyzed:
If b < 0, a degressive dependence is present. This means that the frequency becomes smaller with an increasing amplitude.
This case indicates problems in the foundation, since a progressive dependence normally occurs there.
If b 0, a progressive dependence is present. In this case, the frequency increases with an increasing amplitude. This is the normal case, which is based, just like the modulus of elasticity, on the effect that during rapid movements in the ground, the water in the capillaries cannot be displaced just as quickly, and an apparent increase in rigidity of the ground occurs.
In both cases, a calibration frequency fa, which is used for calibration of the mathematical model of the mast and thereby for calculation of the deflections and deformations of the mast, is recalculated using the dependence of the natural frequency that was found. For these calculations, the following amplitudes are used;
, Value range Amplitude y for frequency Amplitude Consequence for co- calculation in the case dependence efficient b of amplitude dependence and frequency fa for evaluation 0Sb<0.01 f a=f a none none b>0.01 Ygrenz= 0.2-0. 2-2-(0.05.H) progressive Foundation OK
but frequency is fa=a = ygrenz b being reduced as compared with the value from the spectrum n -0.01b<0 Ygrenz=0 . 02-2- (0.05=H) weakly Foundation still OK but frequency i fa=a ' Ygren zb ' 0 . 952 degressive is being somewhat reduced as 0 I.) co compared with the value from the in H
spectrum I.) -0.02b<- Ygranz=0.02=2=(0.05-H) moderately Foundation should be watched, in 0.01 fa=a = Sigreazb = 0.92 degressive frequency is being reduced as I.) H
compared with the value from the a, spectrum a, , 1 b<-0.02 Ygrenz=0 . 02 -6)2- (0.05-H) strongly Foundation is probably damaged, H
f a=a- ' Sigrenzb ' 0 . 852 degressive frequency is being clearly reduced as compared with the value from the spectrum _ The limit amplitudes result from the spectrum, as a function of the mast height H above ground level and the natural circular frequency w from the spectrum.
For the case b < 0, it was assumed, in this connection, that proceeding from a maximal amplitude of 5% of the mast height, the quasi-static range of the decay curve is reached when the vibration amplitudes have decayed to 2% of the maximal amplitude. In this amplitude range, it is assumed that the dynamic rigidities correspond to the rigidities that occur in the case of quasi-stationary stress. The calibration frequency fa is then reduced once again as a function of the order of magnitude of the parameter b. These reduction factors are quasi safety factors that are supposed to absorb the uncertainties of this evaluation routine, among other things, in the case of degressive dependence. As a function of the order of magnitude of b, these factors correspond to reductions in rigidity by 5%
(f: -0.01 S b < 0), 10% (f: -0.02 S b < 0.01) or 15% (f: b < -0.02).
For the case b > 0.01, a smaller amplitude is used for calculation of the calibration frequency. This amounts to 20%
of the amplitude for the case b < 0.
The further calculation (for example according to WO 2010/128056 Al) then takes place using the calibration frequency fa. This frequency is generally less than or at most equal to the natural frequency fa determined from the spectrum.
According to another important aspect of the invention, the stability of a mast set up at an installation site, attached to a foundation, can be determined, whereby the vibration spectrum of the mast, excited to vibrate artificially or by means of environmental influences, is detected, and at least one natural frequency of the mast is determined from this, and whereby the useful lifetime of the mast is then determined on this basis.
For example, the residual useful lifetime can be estimated based on the results of the frequency measurements, as described below.
A useful lifetime is estimated for the mast, depending on the year of construction of the mast and/or depending on the calculated displacement or deflection or deformation and, if applicable, the class limits (as described, for example, in WO
2010/128056 Al).
In general, the measurements lead to the conclusion that the masts have greater displacements at the measurement time point than a perfect, "undamaged" mast. The causes for the greater displacements are, among others, due to the rigidity of the foundation (softer than in the case of a perfect mast) and by time-related factors that lead to a decrease in system rigidity.
Because no information concerning the mast properties at an earlier point in time are available during a first measurement on a mast, it is assumed that the mast was perfect, i.e. intact at the time of installation. From the assumption of system rigidity during the time period between installation and first measurement, a speed of rigidity decrease can thereby be derived. For this purpose, it is assumed that the mast is always clamped in place, and that changes in rigidity are caused only by a (time-dependent) reduction in cross-section. In this connection, it is assumed that the mast cross-section, i.e. the outside diameter, decreases from the outside to the inside at this speed. This assumption results from the consideration that according to various standards (for example DIN 4133), corrosion supplements have to be taken into consideration in the dimensioning of specific components. In principle, these corrosion supplements also describe a decrease in the statically relevant cross-section as a function of time. In the case of wooden masts, the reduction in cross-section results, for example, from shrinkage, rot or fungal infestation.
The diameter of the masts is thereby a function of time t:
d5(t) = de) - v. = t with da0 outside diameter at the time of installation d.(t)outside diameter at the time point t di inside diameter in the case of a circular ring cross-section v8 speed of decrease in the outside diameter in mm/year From the underlying mechanical model, the head point displacements of the mast El(t) can be calculated as a function of time, at an acting force (for example wind load typical for the location). A determination equation for v2 can thereby be obtained, because the variable v5 is the only unknown. The solution of this equation and the determination of v5 takes place by means of an iteration algorithm, for example. With this speed võ it can then be calculated at what point in time the permissible deformation Etna is exceeded. For this purpose, the time t is increased until the following equation has been met:
5(t = tim) = 6zul. The time tw is the estimated useful lifetime.
The difference between tix and the time that has elapsed from the installation time point until the measurement time point tmes is the estimated residual duration of use being searched for.
In this connection, the speed is still multiplied by a safety factor of 1.5, in order to take an increase in the speed of damage into consideration by approximation. The time dependence of the rigidity taken into consideration by the method described is non-linear, because the assumed speed of damage relates to the diameter.
Starting from the second measurement, a more precise calculation of the speed of damage can take place by taking the first measurement values into consideration. In this way, a possible increase in the speed of damage can be detected more precisely, but on the other hand, overestimated speeds of damage from the first estimate can also be corrected, and thereby a more advantageous estimate of useful lifetime can be achieved.
Next, an exemplary embodiment will be given for taking the influence of wood moisture on properties of structural mechanics into consideration in the evaluation of frequency measurements on overhead line masts made of wood:
The wood moisture influences properties of structural mechanics of wood as a material. In the case of wooden masts freely exposed to the weather, the wood moisture approximately follows the changes in temperature, on average. Over the course of the year, variations in wood moisture of approximately 12% to 20%
can occur as a result. A range of approximately 12% to 18% is relevant for wooden masts, because there, temperatures of >0 C
can be assumed. In the case of temperatures below 0 C, the = possibility exists that the ground is frozen, so that in this case, the system rigidity is not representative for the case with maximum wind (winter storm or spring storm with air = temperature approximately 4-5 C). Short-term increases as the result of precipitation are possible. As a result, wood moisture values on the outside of up to 30% can be reached, but these generally dry off again quickly due to the influence of wind.
A decisive parameter of structural mechanics is the modulus of = elasticity (which also influences the bending rigidity). This parameter is dependent on the current wood moisture. It turns out that the modulus of elasticity varies, in the relevant moisture range u = (12%-18%), from about 9200 MPa to 10,000 MPa, in other words by approximately 8%. This range can be viewed as being realistic for impregnated wooden masts. In the short term, wood moisture values of 30% on the outside are possible.
There, the modulus of elasticity drops to about 8600 MPa.
However, the modulus of elasticity relevant for bending rigidity appears as an average value, depending on the tension distribution over the cross-section. Because the inner regions of the mast are not influenced or influenced only slightly by short-term increases in moisture on the outside (depending on the duration of exposure), the variation range can be assumed to be as indicated above.
If the moisture i$ not explicitly entered, a modulus of elasticity is used that applies for a moisture of 15%. This means that the maximal deviations for the calculated bending rigidity and thereby the calculated deformations from the bending component lie at about 3.5%. These deviations can already be viewed as tolerable, taking implemented safety values into account. In this connection, it must also be considered that the overall rigidity is composed of a rotational spring component (foundation) and a bending component (mast). Because the rotational spring component can certainly amount to as much as 30-40% in the case of realistic masts, the variation range of the overall rigidity dependent on the moisture is less than the variation range of the bending rigidity alone. Variation ranges of approximately 2.5% are realistic.
Nevertheless, a correction function that makes use of the dependence of the wood moisture on the time of year is preferably used.
The system rigidity is thereby calculated based on a modulus of elasticity that applies for u = 15% or for the moisture u mess read in during the measurement. This rigidity represents the status at the measurement. For the perfect system (clamped in place), a comparison frequency of fvoll,mes is thereby obtained. For the evaluation of the system behavior, the modulus of elasticity is converted to a moisture of u = 18% (matches 5 C in the case of a storm). In this way, the calculated displacements that are used for the evaluation are maximally approximately 5% greater (for the case: measurement at u = 12% in the summer). The frequency of the perfect system fvou, bewertung at u = 18% thereby becomes less, specifically by maximally approximately 2.5%.
The invention relates not only to a method but also to an = apparatus for implementation of the method according to one of the preceding claims, using a calculation unit that supports the determination of the rigidity of the mast. For this purpose, the calculation unit has suitable programming with corresponding program steps. The apparatus can have at least one acceleration sensor and means for transmission of vibration measurement values detected by the sensor to the calculation unit.
Furthermore, the apparatus can have a moisture sensor and means for transmission of moisture values detected by the sensor to the calculation unit. Finally, it is practical if the apparatus has output means for output of the stability data of the mast that are determined.
The difference between tix and the time that has elapsed from the installation time point until the measurement time point tmes is the estimated residual duration of use being searched for.
In this connection, the speed is still multiplied by a safety factor of 1.5, in order to take an increase in the speed of damage into consideration by approximation. The time dependence of the rigidity taken into consideration by the method described is non-linear, because the assumed speed of damage relates to the diameter.
Starting from the second measurement, a more precise calculation of the speed of damage can take place by taking the first measurement values into consideration. In this way, a possible increase in the speed of damage can be detected more precisely, but on the other hand, overestimated speeds of damage from the first estimate can also be corrected, and thereby a more advantageous estimate of useful lifetime can be achieved.
Next, an exemplary embodiment will be given for taking the influence of wood moisture on properties of structural mechanics into consideration in the evaluation of frequency measurements on overhead line masts made of wood:
The wood moisture influences properties of structural mechanics of wood as a material. In the case of wooden masts freely exposed to the weather, the wood moisture approximately follows the changes in temperature, on average. Over the course of the year, variations in wood moisture of approximately 12% to 20%
can occur as a result. A range of approximately 12% to 18% is relevant for wooden masts, because there, temperatures of >0 C
can be assumed. In the case of temperatures below 0 C, the = possibility exists that the ground is frozen, so that in this case, the system rigidity is not representative for the case with maximum wind (winter storm or spring storm with air = temperature approximately 4-5 C). Short-term increases as the result of precipitation are possible. As a result, wood moisture values on the outside of up to 30% can be reached, but these generally dry off again quickly due to the influence of wind.
A decisive parameter of structural mechanics is the modulus of = elasticity (which also influences the bending rigidity). This parameter is dependent on the current wood moisture. It turns out that the modulus of elasticity varies, in the relevant moisture range u = (12%-18%), from about 9200 MPa to 10,000 MPa, in other words by approximately 8%. This range can be viewed as being realistic for impregnated wooden masts. In the short term, wood moisture values of 30% on the outside are possible.
There, the modulus of elasticity drops to about 8600 MPa.
However, the modulus of elasticity relevant for bending rigidity appears as an average value, depending on the tension distribution over the cross-section. Because the inner regions of the mast are not influenced or influenced only slightly by short-term increases in moisture on the outside (depending on the duration of exposure), the variation range can be assumed to be as indicated above.
If the moisture i$ not explicitly entered, a modulus of elasticity is used that applies for a moisture of 15%. This means that the maximal deviations for the calculated bending rigidity and thereby the calculated deformations from the bending component lie at about 3.5%. These deviations can already be viewed as tolerable, taking implemented safety values into account. In this connection, it must also be considered that the overall rigidity is composed of a rotational spring component (foundation) and a bending component (mast). Because the rotational spring component can certainly amount to as much as 30-40% in the case of realistic masts, the variation range of the overall rigidity dependent on the moisture is less than the variation range of the bending rigidity alone. Variation ranges of approximately 2.5% are realistic.
Nevertheless, a correction function that makes use of the dependence of the wood moisture on the time of year is preferably used.
The system rigidity is thereby calculated based on a modulus of elasticity that applies for u = 15% or for the moisture u mess read in during the measurement. This rigidity represents the status at the measurement. For the perfect system (clamped in place), a comparison frequency of fvoll,mes is thereby obtained. For the evaluation of the system behavior, the modulus of elasticity is converted to a moisture of u = 18% (matches 5 C in the case of a storm). In this way, the calculated displacements that are used for the evaluation are maximally approximately 5% greater (for the case: measurement at u = 12% in the summer). The frequency of the perfect system fvou, bewertung at u = 18% thereby becomes less, specifically by maximally approximately 2.5%.
The invention relates not only to a method but also to an = apparatus for implementation of the method according to one of the preceding claims, using a calculation unit that supports the determination of the rigidity of the mast. For this purpose, the calculation unit has suitable programming with corresponding program steps. The apparatus can have at least one acceleration sensor and means for transmission of vibration measurement values detected by the sensor to the calculation unit.
Furthermore, the apparatus can have a moisture sensor and means for transmission of moisture values detected by the sensor to the calculation unit. Finally, it is practical if the apparatus has output means for output of the stability data of the mast that are determined.
Claims (21)
1. Method for determination of the stability of a mast that has been set up at an installation site, attached to a foundation, or standing in the ground, wherein the vibrations of the mast, excited to vibrate artificially or by means of environmental influences, are detected using measurement technology, and at least one natural frequency of the mast is determined from this.
2. Method according to claim 1, characterized in that a non-linearity of the vibration behavior of the excited mast is analyzed, and on the basis of the result of this analysis, it is determined whether damage to the mast and/or to its attachment in the foundation region is present.
3. Method according to claim 2, characterized in that the dependence of the natural frequency on the vibration amplitude is determined and a calibration frequency is calculated on the basis of this dependence, with which a mechanical model of the mast is calibrated, and the stability of the mast is determined on this basis.
4. Method according to claim 3, characterized in that the calibration frequency is less than the determined natural frequency or maximally equal to it.
5. Method according to one of the preceding claims, characterized in that a deflection of the mast head under external stress on the mast is determined on the basis of the rigidity of the mast derived from the vibration spectrum, wherein the deflection determined is compared with a permissible deflection, in order to determine the stability of the mast.
6. Method for determination of the stability of a mast that has been set up at an installation site, attached to a foundation, or standing in the ground, particularly according to one of claims 1 to 5, wherein the vibration spectrum of the mast, excited to vibrate artificially or by means of environmental influences, is detected, and at least one natural frequency of the mast is determined from this, wherein the useful lifetime of the mast is determined on this basis.
7. Method according to claim 6, characterized in that the year of construction of the mast and/or class limits are used as an additional status parameter in the estimation of the useful lifetime.
8. Method according to claim 6 or 7, characterized in that a deflection of the mast head under an external stress on the mast is determined on the basis of the rigidity of the mast derived from the vibration measurement, wherein the deflection of the mast head is used for a determination of the useful lifetime of the mast.
9. Method according to claim 8, characterized in that the speed of the decrease in rigidity of the mast is determined with the assumption that the technical ideal state is present at the time of installation of the mast, and that the mast has its maximal possible rigidity.
10. Method according to one of the preceding claims, characterized in that in the determination of the rigidity of a mast made of wood, the moisture of the wood is taken into consideration.
11. Method according to one of the preceding claims, characterized in that for a determination of the rigidity of the mast, characteristic data from a database are taken into consideration.
12. Method according to claim 10 or 11, characterized in that the characteristic data contain a predetermined season-dependent moisture of the wood, which is taken into consideration in the determination of the stability.
13. Method according to one of the preceding claims, characterized in that for the determination of the stability of the mast, automatic localization of the mast by way of a navigation satellite system takes place, and on the basis of this localization, automatic feed and/or assignment of characteristic data from a database takes place.
14. Method according to one of the preceding claims, characterized in that the stability of a mast with cables takes place taking a temperature-dependent cable hang into consideration.
15. Method according to claim 14, characterized in that the environment-related cable hang is obtained from a database or determined by means of a measurement of the temperature of the environment, taking cable-specific characteristic data into consideration.
16. Method according to one of the preceding claims, characterized in that the stability of the mast is determined taking the generalized mass of the mast and of the components possibly disposed on it into consideration.
17. Method according to one of the preceding claims, characterized in that the stability of a mast equipped with current-conducting cables is determined taking into consideration the electric power that is conducted through the cables.
18. Apparatus for implementation of the method according to one of the preceding claims, having a calculation unit that supports the determination of the rigidity of the mast.
19. Apparatus according to claim 18, characterized by at least one acceleration sensor and means for transmission of the vibration measurement values detected by the sensor to the calculation unit.
20. Apparatus according to claim 18 or 19, characterized by at least one moisture sensor and means for transmission of the moisture values detected by the sensor to the calculation unit.
21. Apparatus according to one of claims 18 to 20, characterized by output means for output of the stability of the mast that is determined.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE102011107564 | 2011-07-11 | ||
| DE102011107564.3 | 2011-07-11 | ||
| PCT/EP2012/002918 WO2013007382A1 (en) | 2011-07-11 | 2012-07-11 | Method for determining the stability of a mast that has been properly installed at an installation site |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2851725A1 true CA2851725A1 (en) | 2013-01-17 |
| CA2851725C CA2851725C (en) | 2019-11-12 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA2851725A Active CA2851725C (en) | 2011-07-11 | 2012-07-11 | Method for determination of the stability of a mast that has been properly set up at an installation site |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP2732259B9 (en) |
| CA (1) | CA2851725C (en) |
| ES (1) | ES2718673T3 (en) |
| HU (1) | HUE043199T2 (en) |
| PL (1) | PL2732259T3 (en) |
| WO (1) | WO2013007382A1 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB201411694D0 (en) | 2014-07-01 | 2014-08-13 | Aluminium Lighting Company The Ltd | A system for monitoring the structural health of lighting column stock |
| US10365293B2 (en) | 2014-07-01 | 2019-07-30 | The Aluminium Lighting Company Ltd | Monitoring the structural health of columns and like structures |
| DE202015105600U1 (en) | 2014-10-30 | 2015-12-10 | argus electronic Gesellschaft mit beschränkter Haftung Meßtechnik und Automation | Device for measuring the stability of masts |
| DE102019133275A1 (en) * | 2019-12-06 | 2021-06-10 | Fischerwerke Gmbh & Co. Kg | Method for measuring a hardening process of a hardenable mass |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA1249664A (en) * | 1986-03-11 | 1989-01-31 | Maurice W. Murphy | Apparatus and method for testing wooden poles |
| DE10300947A1 (en) * | 2003-01-13 | 2004-07-22 | Mh Technologie Gmbh | Mast, antenna and anchored upright structure testing method, wherein the mast is set in vibration and the resultant reactive forces measured using acceleration sensors |
| EP1517141B1 (en) * | 2003-09-19 | 2013-10-16 | SAG Energieversorgungslösungen GmbH | Method for testing stability of partially burried metal poles |
| DE102009002818B4 (en) | 2009-05-05 | 2022-02-10 | Axel Meyer | Method and device for testing the stability of a mast |
-
2012
- 2012-07-11 EP EP12747884.0A patent/EP2732259B9/en active Active
- 2012-07-11 CA CA2851725A patent/CA2851725C/en active Active
- 2012-07-11 WO PCT/EP2012/002918 patent/WO2013007382A1/en active Application Filing
- 2012-07-11 PL PL12747884T patent/PL2732259T3/en unknown
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| Publication number | Publication date |
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| PL2732259T3 (en) | 2019-06-28 |
| EP2732259B1 (en) | 2019-01-02 |
| ES2718673T3 (en) | 2019-07-03 |
| WO2013007382A1 (en) | 2013-01-17 |
| HUE043199T2 (en) | 2019-08-28 |
| EP2732259A1 (en) | 2014-05-21 |
| CA2851725C (en) | 2019-11-12 |
| EP2732259B9 (en) | 2019-05-08 |
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