CN102270254A - Fatigue design method for deep water riser - Google Patents
Fatigue design method for deep water riser Download PDFInfo
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Abstract
The invention belongs to the technical field of ocean oil and gas equipment, in particular relates to a fatigue design method for a deep water riser. In the method, while the fatigue damage of the deep water riser is considered, a coupling effect of a floating platform vortex-induced motion and riser vortex-induced vibration, influence of the fatigue damage caused by short-term flow on the fatigue damage accumulation of the deep water riser, influence of the fatigue damage caused by floating platform vortex-induced motion and the short-term flow on the fatigue damage of the riser, and influence of the fatigue damage caused by extreme wave load on the fatigue damage of the riser are considered. The fatigue design method for the deep water riser more accords with the actual fatigue damage accumulation nature of the deep water riser, the well-known Miner's linear damage accumulation standard, and current environment load variation tendency and characteristics, and is more scientific, more reasonable, and more safe and reliable in a design result.
Description
Technical field
The invention belongs to marine oil and gas equipment designing technique, be specifically related to a kind of Fatigue Design method of deep water standpipe.
Background technology
The ocean deepwater standpipe is one of important component part in the modern marine engineering structure system, also is one of member of weak rapid wear simultaneously.The ocean deepwater riser interiors generally has the crude oil of High Temperature High Pressure and rock gas to pass through, and the effect of wave, ocean current load is born in the outside because the complicacy of the residing marine environment of deep water standpipe, its influenced factor also many.Fatigue damage is the main failure mode of deep water standpipe, and therefore, the Fatigue Design of deep water standpipe is the key of deep water standpipe design.
Existing deep water standpipe Fatigue Design method mainly adopts the S-N curve method, and this method mainly is based on linear cumulative damage criterion (known method):
In the following formula: D is the fatigue damage summation that various long-range circumstances loads (comprising wave, stream and platform motion) cause; n
iBe the cycle index of a certain stress amplitude, by calculating; N
iFor this stress amplitude causes the cycle index that fatigure failure is required, from the curve of fatigue (different materials, different structure and varying environment condition have different S-N curves for S-N curve, known curve) of standpipe structured material; M is the number that causes the different stress amplitudes of fatigue damage; F is the design fatigue safety coefficient.
For the Fatigue Design of deep water standpipe, following formula can specifically be expressed as:
In the formula: D
WaveThe fatigue damage that causes for wave load; D
LTVIVFor flowing the fatigue damage that vortex-induced vibration causes for a long time; D
LTVIMFor swashing kinetic standpipe fatigue damage in floating platform whirlpool under the long-term stream effect.
Because the statistics of long-range circumstances load (stormy waves stream) is unit with the year, promptly the probability of happening of load, action direction and intensity normally are to add up the reoccurrence period with the year, so the standpipe fatigue damage D that formula (2) calculates is annual damage ratio.Therefore, design can be calculated (known method) by following formula fatigue lifetime:
If the fatigue damage that different loads cause adopts different design safety factor (DSF)s, then formula (3) can be expressed as (known method):
In the formula: f
WaveDesign fatigue safety coefficient for wave load; f
LTVIVDesign fatigue safety coefficient for long-term stream vortex-induced vibration; f
LTVIMFor considering that the design fatigue safety coefficient that motion causes the standpipe fatigue damage is swashed in the floating platform whirlpool under the long-term stream effect.
For the fatigue damage that short-term stream vortex-induced vibration causes, existing technology is not accumulated to it in fatigue damage (formula (2)) that long-range circumstances load causes, but employing formula (5) and formula (6) are calculated separately:
In the formula: D
STVIV, LAnd f
STVIV, LBe vortex-induced vibration fatigue damage and the design fatigue safety coefficient thereof that 100 years one chance circulation cause; D
STVIV, SAnd f
STVIV, SBe vortex-induced vibration fatigue damage and the design fatigue safety coefficient thereof that 100 years one chance undercurrents cause.
Prior art is not calculated short-term stream (100 years one chance circulation or 100 years one chance undercurrents) effect and is swashed kinetic standpipe fatigue damage in the floating platform whirlpool down, do not calculate the fatigue damage that Mechanics of Extreme Wave (10 years one chances, 50 a years chance or 100 years one chances) causes, because the probability of happening of past short-term stream and Mechanics of Extreme Wave is smaller yet.
There are following four tangible deficiencies in prior art:
1. the independent calculating of fatigue damage difference that the vortex-induced vibration of generation under the direct effect of ocean current causes with upright fatigue damage of the sharp kinetic deep water in floating platform whirlpool and standpipe, then the two is carried out linear superposition and calculate the fatigue damage that long-term stream causes, this is a big shortcoming of prior art.Because, standpipe is that (the tubular platform passes through guide ring by certain connected mode, tension leg platform (TLP) passes through stretcher) flexibly connect with floating platform, and the vortex-induced vibration of sharp motion in the whirlpool of floating platform and standpipe produces under ocean current acts on simultaneously, because (18～28m) are far longer than the diameter (0.3～0.5m) of standpipe to the diameter of floating platform, therefore, when being subjected to the action of ocean current of identical flow velocity simultaneously, the whirlpool commendable increase power size (relevant with cylinder diameter) and the frequency (relevant with cylinder diameter) that act on floating platform and the standpipe are all different, (floating platform rigidity is big thereby motion is swashed in the whirlpool of floating platform, do not occur bending and deformation, belong to rigid motion, therefore, be called the whirlpool and swash " motion ", but still be reciprocal vibration, rather than motion as boats and ships.) all different with amplitude with vortex-induced vibration (reciprocal elastic bending deflection) frequency of standpipe, and moving through of the two connect to interact, and is that a kind of coupling fortune (shaking) is moving.Because vibration (vibration) frequency of the two is different with amplitude, therefore, has phase differential between the vibration of floating platform and the vibration of standpipe, and this phase differential is constantly to change.This coupled relation that swash between motion and the riser vortex excited vibration in the floating platform whirlpool can not calculate with the two simple linear superposition, and only when the phase differential of the two was zero, simple linear superposition was only feasible.Therefore, prior art adopt the method calculate again linear superposition respectively to calculate the floating platform whirlpool to swash the standpipe fatigue damage that motion and ocean current cause be inaccurate.
2. the fatigue damage that short-term stream vortex-induced vibration is caused is independently calculated check, does not consider the influence to the standpipe accumulation of fatigue damage of fatigue damage that short-term stream vortex-induced vibration causes, and this is the another shortcoming of prior art.The fatigue damage of structure is a kind of cumulative effect, and in the military service phase of structure, the fatigue damage that any type of load causes all will be accumulated in the damage of structure, will never be because of the disappearance of load " healing ".Therefore, no matter whether the load of which kind of form that when takes place in the structure military service phase and this load take place repeatedly, and its fatigue damage that once causes all will be accumulated in the damage of structure, thereby damage of structure is increased.Although short-term stream is not etesian, if the short-term stream that takes place of standpipe military service initial stage, its fatigue damage of causing fatigue damage accumulation that must cause with follow-up any form load and influence the safety of standpipe so.Therefore, prior art does not consider that fatigue damage that short-term stream vortex-induced vibration causes is irrational to the cumulative effect of standpipe fatigue damage.
3. do not consider that floating platform whirlpool that short-term stream causes swashs the influence to deep water standpipe fatigue damage of fatigue damage that motion causes, this is the 3rd shortcoming of prior art.The intensity of short-term stream is big, and it will cause that floating platform swashs motion (resonance) in the whirlpool significantly, therefore, should not ignore the standpipe fatigue damage that it causes.This only is an one, and it two is that the probability of happening of short-term stream increases gradually, and the definition that tradition was met in 100 years one is met even phenomenon that 1 year one meets negates at present for many years.Even if the standpipe that the next year after short-term stream takes place installs also may take place in its military service phase in 20 years for the second time with for the third time.So, do not consider that floating platform whirlpool that short-term stream causes swashs fatigue damage that motion causes and will directly cause unsafe Fatigue Design to the influence of deep water standpipe fatigue damage.Therefore, prior art does not consider that the sharp standpipe fatigue damage that is caused of moving in floating platform whirlpool that short-term stream causes does not meet engineering reality.
4. do not consider the influence to deep water standpipe fatigue damage of fatigue damage that the Mechanics of Extreme Wave load causes, this is the 4th shortcoming of prior art.Because, but still may take place in the military service phase in 20 years at standpipe even if the probability of happening of Mechanics of Extreme Wave load is low.The definition of meeting in 50 years one is not to take place once in per 50 years, therefore, even met the standpipe of the next year installation after wave takes place at 50 years one, in its military service phase in 20 years, also may take place once again to meet in 50 years one even wave load that 100 years one meet, moreover the actual military service phase of standpipe tends to prolong because of the needs of oil-field development.And in recent years owing to reasons such as climate changes, the generation frequency of extreme environmental conditions is more and more higher, and wave load has been gradually become " taking place frequently " by original " accidental " phenomenon disaster is met or met in 100 years one in 50 years of past definition.So, for the such important structure thing of deep water standpipe (say its important be because, in case have an accident, economic loss that causes and political fallout will be huge) do not consider that fatigue damage that the Mechanics of Extreme Wave load causes is inaccurate to the influence of deep water standpipe fatigue damage.
Summary of the invention
The objective of the invention is at the defective of prior art on deep water standpipe Fatigue Design, a kind of more rationally and more deep water standpipe Fatigue Design method of science is provided.
Technical scheme of the present invention is as follows: a kind of Fatigue Design method of deep water standpipe comprises:
The standpipe fatigue damage rate that causes based on the long-term wave load of calculation of design parameters of the wave speckle pattern in deep water standpipe design object marine site, corresponding S-N curve and floating platform and standpipe
Unit is 1/ year, wherein, and n1
iThe cycle index of i the stress amplitude that causes for long-term wave load, N1
iFor the required cycle index of fatigure failure takes place down in this stress amplitude effect, S1 is the number of the different stress amplitudes of standpipe that every year, long-term wave load caused;
The fatigue damage rate that motion and riser vortex excited vibration cause is swashed in the floating platform whirlpool that causes based on the long-term stream of calculation of design parameters of the ocean current data in deep water standpipe design object marine site, corresponding S-N curve and floating platform and standpipe
Unit is 1/ year, wherein, and n2
iFor swashing the cycle index of i the stress amplitude that motion and riser vortex excited vibration cause, N2 in floating platform whirlpool under the long-term stream effect
iFor this stress amplitude causes the cycle index that fatigure failure is required, S2 swashs the number of the motion different stress amplitudes of standpipe that excited vibration causes with riser vortex for floating platform whirlpool under the annual long-term stream effect;
The fatigue damage rate that the vortex-induced vibration of motion and standpipe causes is swashed in the floating platform whirlpool that causes based on the calculation of design parameters short-term stream of 100 years one of deep water standpipe design object marine site meeting circulation data, corresponding S-N curve and floating platform and standpipe
Unit is 1/ time, wherein, and n3
iBe to meet the cycle index that i the stress amplitude that motion and riser vortex excited vibration cause swashed in floating platform whirlpool under the circulation effect, N3 in 100 years one
iFor this stress amplitude causes the cycle index that fatigure failure is required, S3 is the number that the motion different stress amplitudes of standpipe that excited vibration causes with riser vortex are swashed in the floating platform whirlpool under the effect of each 100 years one chance circulation;
The fatigue damage rate that the vortex-induced vibration of motion and standpipe causes is swashed in the floating platform whirlpool that causes based on the calculation of design parameters short-term stream of 100 years one of deep water standpipe design object marine site meeting undercurrent data, corresponding S-N curve and floating platform and standpipe
Unit is 1/ time, wherein, and n4
iBe to meet the cycle index that i the stress amplitude that motion and riser vortex excited vibration cause swashed in floating platform whirlpool under the undercurrent effect, N4 in 100 years one
iFor this stress amplitude causes the cycle index that fatigure failure is required, S4 is the number that the motion different stress amplitudes of standpipe that excited vibration causes with riser vortex are swashed in the floating platform whirlpool under the effect of each 100 years one chance undercurrents;
The fatigue damage rate that causes based on the calculation of design parameters Mechanics of Extreme Wave load of 10 years of deep water standpipe design object marine site meeting wave data, corresponding S-N curve and floating platform and standpipe
Unit is 1/ time, wherein, and n5
iBe the cycle index of meeting i the stress amplitude that wave loads cause in 10 years, N5
iFor this stress amplitude causes the cycle index that fatigure failure is required, S5 is the number of meeting the different stress amplitudes of standpipe that wave causes in each 10 years;
The fatigue damage rate that causes based on the calculation of design parameters Mechanics of Extreme Wave load of 50 years of deep water standpipe design object marine site meeting wave data, corresponding S-N curve and floating platform and standpipe
Unit is 1/ time, wherein, and n6
iBe the cycle index of meeting i the stress amplitude that wave loads cause in 50 years, N6
iFor this stress amplitude causes the cycle index that fatigure failure is required, S6 is the number of meeting the different stress amplitudes of standpipe that wave causes in each 50 years;
The fatigue damage rate that causes based on the calculation of design parameters Mechanics of Extreme Wave load of 100 years of deep water standpipe design object marine site meeting wave data, corresponding S-N curve and floating platform and standpipe
Unit is 1/ time, wherein, and n7
iBe the cycle index of meeting i the stress amplitude that wave loads cause in 100 years, N7
iBe the required cycle index of fatigure failure that this stress amplitude causes, S7 is the number of meeting the different stress amplitudes of standpipe that wave causes in each 100 years;
Based on Fatigue Design Criterion, carry out the Fatigue Design of standpipe by following formula and check:
D＝(D
wave×f
wave+D
LTVIM+LTVIV×f
LTVIM+LTVIV)×n
life+(D
STVIM，L+STVIV，L×n
loop+D
STVIM，S+STVIV，S×n
sub)×f
STVIM+STVIV+(D
wave，10×n
wave，10+D
wave，50×n
wave，50+D
wave，100×n
wave，100)×f
extremewave≤1
Can be calculated as follows the designed life of standpipe:
n
life＝[1-(D
STVIM，L+STVIV，L×n
loop+D
STVIM，S+STVIV，S×n
sub)×f
STVIM+STVIV-(D
wave，10×n
wave，10+D
wave，50×n
wave，50+D
wave，100×n
wave，100)×f
extremewave]/(D
wave×f
wave+D
LTVIM+LTVIV×f
LTVIM+LTVIV)
In the following formula, f
WaveBe the design fatigue safety coefficient of long-term wave load, f
LTVIM+LTVIVBe the design fatigue safety coefficient of long-term stream load, f
STVIM+STVIVBe the design fatigue safety coefficient of short-term stream load, f
ExtremewaveBe the design fatigue safety coefficient of Mechanics of Extreme Wave load, n
LifeBe standpipe designed life, n
LoopFor meeting the prediction frequency of circulation, n in phase designed life in 100 years one
SubFor meeting the prediction frequency of undercurrent, n in phase designed life in 100 years one
Wave, 10For meeting the prediction frequency of wave load, n in phase designed life in 10 years one
Wave, 50For meeting the prediction frequency of wave load, n in phase designed life in 50 years one
Wave, 100For meeting the prediction frequency of wave load in phase designed life in 100 years one.
Beneficial effect of the present invention is as follows: deep water standpipe Fatigue Design method provided by the present invention has been considered the coupling effect of sharp motion in floating platform whirlpool and riser vortex excited vibration, considered the influence of fatigue damage that short-term stream causes to deep water standpipe accumulation of fatigue damage, considered that floating platform whirlpool that short-term stream causes swashs the influence to the standpipe fatigue damage of fatigue damage that motion causes, considered the influence of fatigue damage that the Mechanics of Extreme Wave load causes to the standpipe fatigue damage, the simple linear of calculating than the non-coupling of the existing method more science that superposes, more meet the natural law, and more meet the fatigue damage mechanism of structure.
Embodiment
Describe the present invention below in conjunction with embodiment.
Short-term stream is the high current field of a kind of " accidental ", but owing to be not etesian environmental phenomenon, therefore, existing deep water standpipe Fatigue Design method is in the design of calculating standpipe during fatigue lifetime, do not consider the fatigue damage that short-term stream vortex-induced vibration causes, that is do not comprise the fatigue damage that short-term stream causes when, calculating accumulation of fatigue damage.But because the intensity big (flow velocity is big) of short-term stream, existing deep water standpipe Fatigue Design is calculated individually to the fatigue damage that short-term stream causes.This obviously is irrational, because the fatigue damage that short-term stream causes will be with the disappearance of short-term stream " healing ", it will be present among the standpipe and with original fatigue damage and follow-up fatigue damage accumulation, with total accumulation of fatigue damage effect harm structural safety, rather than the fatigue damage that is independent of other form endangers structural safety separately.Therefore, the Fatigue Design of deep water standpipe should be considered the influence of short-term stream vortex-induced vibration fatigue.
The Mechanics of Extreme Wave load is meant the wave load that may only take place once in longer a period of time, as 50 years or 100 years one chances, all are far longer than its wave height and period of wave the wave load of 1 year one chance.Existing deep water standpipe Fatigue Design method is not considered the influence to the standpipe fatigue damage of fatigue damage that such " accidental " property Mechanics of Extreme Wave load causes, reason is to be generally the designed life of deep water standpipe 20 years, therefore, such wave load may not can take place in the standpipe military service phase, even if take place, also only continue several days, its caused fatigue damage is minimum to the fatigue damage contribution of standpipe, can ignore.But entered since 21 century, extreme marine environment takes place frequently, and the hurricane in the Gulfian no longer is 50 years one chances, and almost is 1 year one chance.The typhoon of China's southeastern coast also almost all can take place every year, and according to National Bureau of Oceanography's statistics, the wave of meeting in 50 years is annual the generation 26 days in marine site, the Bohai Sea.This shows, the Mechanics of Extreme Wave load no longer has been an accidental phenomenon of meeting for many years, and becomes the environmental load of meeting in a year.Therefore, when carrying out deep water standpipe Fatigue Design, should consider the contribution of fatigue damage that the Mechanics of Extreme Wave load causes to the standpipe fatigue damage.
The deep water standpipe is that (the tubular platform passes through guide ring by certain connected mode, tension leg platform (TLP) passes through stretcher) flexibly connect with floating platform, and the vortex-induced vibration of sharp motion in the whirlpool of floating platform and standpipe produces under ocean current acts on simultaneously, because (18～28m) are far longer than the diameter (0.3～0.5m) of standpipe to the diameter of floating platform, therefore, when being subjected to the action of ocean current of identical flow velocity simultaneously, the whirlpool commendable increase power size (relevant with cylinder diameter) and the frequency (relevant with cylinder diameter) that act on floating platform and the standpipe are all different, (floating platform rigidity is big thereby motion is swashed in the whirlpool of floating platform, do not occur bending and deformation, belong to rigid motion, therefore, be called the whirlpool and swash " motion ", but still be reciprocal vibration, rather than the motion as boats and ships) vortex-induced vibration (reciprocal elastic bending deflection) frequency with standpipe is all different with amplitude, and moving through of the two connect to interact, and is that a kind of coupling fortune (shaking) is moving.Because vibration (vibration) frequency of the two is different with amplitude, therefore, has phase differential between the vibration of floating platform and the vibration of standpipe, and this phase differential is constantly to change.This coupled relation that swash between motion and the riser vortex excited vibration in the floating platform whirlpool can not calculate with the two simple linear superposition, and only when the phase differential of the two was zero, simple linear superposition was only feasible.Therefore, prior art adopt the method calculate again linear superposition respectively to calculate the floating platform whirlpool to swash the fatigue damage that motion and riser vortex excited vibration cause be inaccurate.
For these reasons, the present invention proposes a kind of Fatigue Design method of deep water standpipe, comprise the calculating content of following several respects:
1. the standpipe fatigue damage rate that long-term wave load causes
The standpipe fatigue damage rate that causes based on the long-term wave load of calculation of design parameters of the wave speckle pattern (the wave probability of happening of different wave height and different wave direction in a year) in deep water standpipe design object marine site, corresponding S-N curve and floating platform and standpipe
Unit is 1/ year, wherein, and n1
iThe cycle index of i the stress amplitude that causes for long-term wave load, N1
iFor this stress amplitude causes the cycle index that fatigure failure is required, S1 is the number of the different stress amplitudes that cause of long-term wave load.The cycle index n1 of i the stress amplitude that long-term wave load causes
iCan adopt floating platform and standpipe model of coupling or block mold and adopt time history analysis method and rain flow method calculating, i stress amplitude causes the cycle index N1 that fatigure failure is required
iCan check in by corresponding S-N curve.These calculate and analytical approach all is a known technology, and those skilled in the art can realize fully.
2. the fatigue damage rate that sharp motion in floating platform whirlpool that long-term stream causes and riser vortex excited vibration cause
The fatigue damage rate that motion and riser vortex excited vibration cause is swashed in the floating platform whirlpool that causes based on the long-term stream of calculation of design parameters of the ocean current data (the ocean current probability of happening of the flow velocity of the different depth of waters and different directions in a year) in deep water standpipe design object marine site, corresponding S-N curve and floating platform and standpipe
Unit is 1/ year, wherein, and n2
iFor swashing the cycle index of i the stress amplitude that motion and riser vortex excited vibration cause, N2 in floating platform whirlpool under the long-term stream effect
iFor this stress amplitude causes the cycle index that fatigure failure is required, S2 is the number that the motion different stress amplitudes that excited vibration causes with riser vortex are swashed in the floating platform whirlpool under the long-term stream effect.N2
i, N2
iCalculating also can adopt above-mentioned identical method, as time history analysis method and rain flow method, S-N curve.
3. the fatigue damage rate that sharp motion in floating platform whirlpool that circulation causes in the short-term stream and riser vortex excited vibration cause
The fatigue damage rate that motion and riser vortex excited vibration cause is swashed in the floating platform whirlpool that causes based on the calculation of design parameters short-term stream of 100 years one of deep water standpipe design object marine site meeting circulation data (flow velocity of the different depth of waters, the flow direction and duration), corresponding S-N curve and floating platform and standpipe
Unit is 1/ time, wherein, and n3
iBe to meet the cycle index that i the stress amplitude that the vortex-induced vibration of motion and standpipe causes swashed in floating platform whirlpool under the circulation effect, N3 in 100 years one
iFor this stress amplitude causes the cycle index that fatigure failure is required, S3 is the number that the motion different stress amplitudes that excited vibration causes with riser vortex are swashed in the floating platform whirlpool under the effect of 100 years one chance circulation.N3
i, N3
iCalculating also can adopt above-mentioned identical method, as time history analysis method and rain flow method, S-N curve.
4. the fatigue damage rate that sharp motion in floating platform whirlpool that undercurrent causes in the short-term stream and riser vortex excited vibration cause
The fatigue damage rate that motion and riser vortex excited vibration cause is swashed in the floating platform whirlpool that causes based on the calculation of design parameters short-term stream of 100 years one of deep water standpipe design object marine site meeting undercurrent data (flow velocity of the different depth of waters, the flow direction and duration), corresponding S-N curve and floating platform and standpipe
Unit is 1/ time, wherein, and n4
iBe to meet the cycle index that i the stress amplitude that the vortex-induced vibration of motion and standpipe causes swashed in floating platform whirlpool under the undercurrent effect, N4 in 100 years one
iFor this stress amplitude causes the cycle index that fatigure failure is required, S4 is the number that the motion different stress amplitudes that excited vibration causes with riser vortex are swashed in the floating platform whirlpool under the effect of 100 years one chance undercurrents.N4
i, N4
iCalculating also can adopt above-mentioned identical method, as time history analysis method and rain flow method, S-N curve.
5.10 year one is met the fatigue damage rate that the Mechanics of Extreme Wave load causes
The fatigue damage rate that causes based on the calculation of design parameters Mechanics of Extreme Wave load of 10 years of deep water standpipe design object marine site meeting wave data (wave height, wave direction, period of wave and duration), corresponding S-N curve and floating platform and standpipe
Unit is 1/ time, wherein, and n5
iBe the cycle index of meeting i the stress amplitude that wave loads cause in 10 years, N5
iFor this stress amplitude causes the cycle index that fatigure failure is required, S5 is the number of meeting the different stress amplitudes that wave loads cause in 10 years.N5
i, N5
iCalculating also can adopt above-mentioned identical method, as time history analysis method and rain flow method, S-N curve.
6.50 year one is met the fatigue damage rate that the Mechanics of Extreme Wave load causes
The fatigue damage rate that causes based on the calculation of design parameters Mechanics of Extreme Wave load of 50 years of deep water standpipe design object marine site meeting wave data (wave height, wave direction, period of wave and duration), corresponding S-N curve and floating platform and standpipe
Unit is 1/ time, wherein, and n6
iBe the cycle index of meeting i the stress amplitude that wave loads cause in 50 years, N6
iFor this stress amplitude causes the cycle index that fatigure failure is required, S6 is the number of meeting the different stress amplitudes that wave loads cause in 50 years.N6
i, N6
iCalculating also can adopt above-mentioned identical method, as time history analysis method and rain flow method, S-N curve.
7.100 year one is met the fatigue damage rate that the Mechanics of Extreme Wave load causes
The fatigue damage rate that causes based on the calculation of design parameters Mechanics of Extreme Wave load of 100 years of deep water standpipe design object marine site meeting wave data (wave height, wave direction, period of wave and duration), corresponding S-N curve and floating platform and standpipe
Unit is 1/ time, wherein, and n7
iBe the cycle index of meeting i the stress amplitude that the Mechanics of Extreme Wave loads cause in 100 years, N7
iBe the required cycle index of fatigure failure that this stress amplitude causes, S7 is the number of meeting the different stress amplitudes that wave loads cause in 100 years.N7
i, N7
iCalculating also can adopt above-mentioned identical method, as time history analysis method and rain flow method, S-N curve.
8. designed life of the fatigue damage of standpipe and standpipe
With D
WaveMultiply by the design fatigue safety coefficient f of long-term wave load
WaveWith n designed life
LifeD
LTVIM+LTVIVMultiply by the design fatigue safety coefficient f of long-term stream load
LTVIM+LTVIVWith n designed life
LifeD
STVIM, L+STVIV, LMultiply by the design fatigue safety coefficient f of short-term stream load
STVIM+STVIVWith the prediction frequency n that met circulation in phase designed life in 100 years
LoopD
STVIM, S+STVIV, SMultiply by the design fatigue safety coefficient f of short-term stream load
STVIM+STVIVWith the prediction frequency n that met undercurrent in phase designed life in 100 years
SubD
Wave, 10Multiply by the design fatigue safety coefficient f of Mechanics of Extreme Wave load
ExtremewaveWith the prediction frequency n that met wave load in phase designed life in 10 years
Wave, 10D
Wave, 50Multiply by the design fatigue safety coefficient f of Mechanics of Extreme Wave load
ExtremewaveWith the prediction frequency n that met wave load in phase designed life in 50 years
Wave, 50D
Wave, 100Multiply by the design fatigue safety coefficient f of Mechanics of Extreme Wave load
ExtremewaveWith the prediction frequency n that met wave load in phase designed life in 100 years
Wave, 100, and based on Fatigue Design Criterion (known criterion):
Carry out the Fatigue Design of standpipe checks by following formula:
D＝(D
wave×f
wave+D
LTVIM+LTVIV×f
LTVIM+LTVIV)×n
life+(D
STVIM，L+STVIV，L×n
loop+D
STVIM，S+STVIV，S×n
sub)×f
STVIM+STVIV+(D
wave，10×n
wave，10+D
wave，50×n
wave，50+D
wave，100×n
wave，100)×f
extremewave≤1
Can be calculated as follows the designed life of standpipe:
n
life＝[1-(D
STVIM，L+STVIV，L×nloop+D
STVIM，S+STVIV，S×n
sub)×f
STVIM+STVIV-(D
wave，10×n
wave，10+D
wave，50×n
wave，50+D
wave，100×n
wave，100)×f
extremewave]/(D
wave×f
wave+D
LTVIM+LTVIV×f
LTVIM+LTVIV)
In the following formula, f
WaveBe the design fatigue safety coefficient of long-term wave load, f
LTVIM+LTVIVBe the design fatigue safety coefficient of long-term stream load, f
STVIM+STVIVBe the design fatigue safety coefficient of short-term stream load, f
ExtremewaveBe the design fatigue safety coefficient of Mechanics of Extreme Wave load, n
LifeBe standpipe designed life, n
LoopFor meeting the prediction frequency of circulation, n in phase designed life in 100 years one
SubFor meeting the prediction frequency of undercurrent, n in phase designed life in 100 years one
Wave, 10For meeting the prediction frequency of wave load, n in phase designed life in 10 years one
Wave, 50For meeting the prediction frequency of wave load, n in phase designed life in 50 years one
Wave, 100For meeting the prediction frequency of wave load in phase designed life in 100 years one.
Design fatigue safety coefficient f
Wave, f
LTVIM+LTVIV, f
STVIM+STVIV, f
ExtremewaveValue be that safe class according to platform is checked in design fatigue safety coefficient f by design specifications
Wave, f
LTVIM+LTVIV, f
STVIM+STVIVAnd f
ExtremewaveDesirable identical value also can be got different value according to the character of load.Load is uncertain big, and its design fatigue safety coefficient is got higher value, and vice versa.
Deep water standpipe Fatigue Design method proposed by the invention has been considered the coupling effect of sharp motion in floating platform whirlpool and riser vortex excited vibration, considered the influence of fatigue damage that short-term stream causes to deep water standpipe accumulation of fatigue damage, considered that floating platform whirlpool that short-term stream causes swashs the influence to the standpipe fatigue damage of fatigue damage that motion causes, considered the influence of fatigue damage that the Mechanics of Extreme Wave load causes to the standpipe fatigue damage, the simple linear of calculating than the non-coupling of the existing method more science that superposes, more meet the natural law, and, more meet the fatigue damage mechanism of structure than existing method.The present invention more meets the fatigue damage accumulation essence of deep water standpipe reality, more meets known Miner ' s linear damage accumulation criterion, more meets current environmental load variation tendency and characteristics, science, more reasonable more, design result safety and reliability.
Obviously, those skilled in the art can carry out various changes and modification to the present invention and not break away from the spirit and scope of the present invention.Like this, if of the present invention these are revised and modification belongs within the scope of claim of the present invention and equivalent technology thereof, then the present invention also is intended to comprise these changes and modification interior.
Claims (6)
1. the Fatigue Design method of a deep water standpipe comprises:
The standpipe fatigue damage rate that causes based on the long-term wave load of calculation of design parameters of the wave speckle pattern in deep water standpipe design object marine site, corresponding S-N curve and floating platform and standpipe
Unit is 1/ year, wherein, and n1
iThe cycle index of i the stress amplitude that causes for long-term wave load, N1
iFor the required cycle index of fatigure failure takes place down in this stress amplitude effect, S1 is the number of the different stress amplitudes of standpipe that every year, long-term wave load caused;
The fatigue damage rate that motion and riser vortex excited vibration cause is swashed in the floating platform whirlpool that causes based on the long-term stream of calculation of design parameters of the ocean current data in deep water standpipe design object marine site, corresponding S-N curve and floating platform and standpipe
Unit is 1/ year, wherein, and n2
iFor swashing the cycle index of i the stress amplitude that motion and riser vortex excited vibration cause, N2 in floating platform whirlpool under the long-term stream effect
iFor this stress amplitude causes the cycle index that fatigure failure is required, S2 swashs the number of the motion different stress amplitudes of standpipe that excited vibration causes with riser vortex for floating platform whirlpool under the annual long-term stream effect;
The fatigue damage rate that the vortex-induced vibration of motion and standpipe causes is swashed in the floating platform whirlpool that causes based on the calculation of design parameters short-term stream of 100 years one of deep water standpipe design object marine site meeting circulation data, corresponding S-N curve and floating platform and standpipe
Unit is 1/ time, wherein, and n3
iBe to meet the cycle index that i the stress amplitude that motion and riser vortex excited vibration cause swashed in floating platform whirlpool under the circulation effect, N3 in 100 years one
iFor this stress amplitude causes the cycle index that fatigure failure is required, S3 is the number that the motion different stress amplitudes of standpipe that excited vibration causes with riser vortex are swashed in the floating platform whirlpool under the effect of each 100 years one chance circulation;
The fatigue damage rate that the vortex-induced vibration of motion and standpipe causes is swashed in the floating platform whirlpool that causes based on the calculation of design parameters short-term stream of 100 years one of deep water standpipe design object marine site meeting undercurrent data, corresponding S-N curve and floating platform and standpipe
Unit is 1/ time, wherein, and n4
iBe to meet the cycle index that i the stress amplitude that motion and riser vortex excited vibration cause swashed in floating platform whirlpool under the undercurrent effect, N4 in 100 years one
iFor this stress amplitude causes the cycle index that fatigure failure is required, S4 is the number that the motion different stress amplitudes of standpipe that excited vibration causes with riser vortex are swashed in the floating platform whirlpool under the effect of each 100 years one chance undercurrents;
The fatigue damage rate that causes based on the calculation of design parameters Mechanics of Extreme Wave load of 10 years of deep water standpipe design object marine site meeting wave data, corresponding S-N curve and floating platform and standpipe
Unit is 1/ time, wherein, and n5
iBe the cycle index of meeting i the stress amplitude that wave loads cause in 10 years, N5
iFor this stress amplitude causes the cycle index that fatigure failure is required, S5 is the number of meeting the different stress amplitudes of standpipe that wave causes in each 10 years;
The fatigue damage rate that causes based on the calculation of design parameters Mechanics of Extreme Wave load of 50 years of deep water standpipe design object marine site meeting wave data, corresponding S-N curve and floating platform and standpipe
Unit is 1/ time, wherein, and n6
iBe the cycle index of meeting i the stress amplitude that wave loads cause in 50 years, N6
iFor this stress amplitude causes the cycle index that fatigure failure is required, S6 is the number of meeting the different stress amplitudes of standpipe that wave causes in each 50 years;
The fatigue damage rate that causes based on the calculation of design parameters Mechanics of Extreme Wave load of 100 years of deep water standpipe design object marine site meeting wave data, corresponding S-N curve and floating platform and standpipe
Unit is 1/ time, wherein, and n7
iBe the cycle index of meeting i the stress amplitude that wave loads cause in 100 years, N7
iBe the required cycle index of fatigure failure that this stress amplitude causes, S7 is the number of meeting the different stress amplitudes of standpipe that wave causes in each 100 years;
Based on Fatigue Design Criterion, carry out the Fatigue Design of standpipe by following formula and check:
D＝(D
wave×f
wave+D
LTVIM+LTVIV×f
LTVIM+LTVIV)×n
life+(D
STVIM，L+STVIV，L×n
loop+D
STVIM，S+STVIV，S×n
sub)×f
STVIM+STVIV+(D
wave，10×n
wave，10+D
wave，50×n
wave，50+D
wave，100×n
wave，100)×f
extremewave≤1
Can be calculated as follows the designed life of standpipe:
n
life＝[1-(D
STVIM，L+STVIV，L×n
loop+D
STVIM，S+STVIV，S×n
sub)×f
STVIM+STVIV-(D
wave，10×n
wave，10+D
wave，50×n
wave，50+D
wave，100×n
wave，100)×f
extremewave]/(D
wave×f
wave+D
LTVIM+LTVIV×f
LTVIM+LTVIV)
In the following formula, f
WaveBe the design fatigue safety coefficient of long-term wave load, f
LTVIM+LTVIVBe the design fatigue safety coefficient of long-term stream load, f
STVIM+STVIVBe the design fatigue safety coefficient of short-term stream load, f
ExtremewaveBe the design fatigue safety coefficient of Mechanics of Extreme Wave load, n
LifeBe standpipe designed life, n
LoopFor meeting the prediction frequency of circulation, n in phase designed life in 100 years one
SubFor meeting the prediction frequency of undercurrent, n in phase designed life in 100 years one
Wave, 10For meeting the prediction frequency of wave load, n in phase designed life in 10 years one
Wave, 50For meeting the prediction frequency of wave load, n in phase designed life in 50 years one
Wave, 100For meeting the prediction frequency of wave load in phase designed life in 100 years one.
2. the Fatigue Design method of deep water standpipe as claimed in claim 1 is characterized in that: the wave speckle pattern in described deep water standpipe design object marine site is represented is the wave probability of happening of different wave height and different wave direction in a year.
3. the Fatigue Design method of deep water standpipe as claimed in claim 1 is characterized in that: the ocean current data in described deep water standpipe design object marine site are meant the distribution along the depth of water of the probability of happening of different in flow rate and different directions ocean current in a year and flow velocity thereof.
4. the Fatigue Design method of deep water standpipe as claimed in claim 1 is characterized in that: met circulation flow velocity, the flow direction and the duration that the circulation data are meant the different depth of waters in 100 years one of described deep water standpipe design object marine site.
5. the Fatigue Design method of deep water standpipe as claimed in claim 1 is characterized in that: met undercurrent flow velocity, the flow direction and the duration that the undercurrent data are meant the different depth of waters in 100 years one of described deep water standpipe design object marine site.
6. the Fatigue Design method of deep water standpipe as claimed in claim 1 is characterized in that: met wave height, wave direction, period of wave and the duration that the wave data are meant wave in 10 years, 50 years of described deep water standpipe design object marine site, 100 years one.
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| CN103206205A (en) * | 2013-03-22 | 2013-07-17 | 中国石油天然气股份有限公司 | Tubing string service life prediction method |
| CN103206205B (en) * | 2013-03-22 | 2015-10-14 | 中国石油天然气股份有限公司 | A kind of tubing string life-span prediction method |
| CN103353382A (en) * | 2013-07-10 | 2013-10-16 | 天津大学 | Analyzing method for parametric-excitation and vortex-induced vibratory fatigue of deep-ocean top tension riser |
| CN103778276A (en) * | 2013-12-27 | 2014-05-07 | 河海大学 | Reliability degree predication method for composite material based on fatigue life distribution |
| CN103778276B (en) * | 2013-12-27 | 2016-08-31 | 河海大学 | Composite Predicting Reliability method based on FATIGUE LIFE DISTRIBUTION |
| CN108138562A (en) * | 2015-10-09 | 2018-06-08 | 通用电气公司 | For estimating the system of fatigue damage |
| CN108138562B (en) * | 2015-10-09 | 2021-08-27 | 通用电气公司 | System for estimating fatigue damage and method for producing hydrocarbon-containing fluid |
| CN108563846A (en) * | 2018-03-27 | 2018-09-21 | 浙江工业大学 | A kind of marine riser wave based on reliability causes the determination method of fatigue safety coefficient |
| CN108595767A (en) * | 2018-03-27 | 2018-09-28 | 浙江工业大学 | A kind of determination method of marine riser VIV fatigue safety coefficients based on reliability |
| CN108595767B (en) * | 2018-03-27 | 2022-04-05 | 浙江工业大学 | Reliability-based marine riser VIV fatigue safety coefficient determination method |
| CN108563846B (en) * | 2018-03-27 | 2022-07-15 | 浙江工业大学 | Method for determining marine riser wave-induced fatigue safety coefficient based on reliability |
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