动态控制参数的含义dyn-control

1、Control ParameterSIC LOAD CASE FOR NONLINEAR RESTRASUS(Active for:Harmonic, Spectrum, Modal, Range, and Time History)Currently all of CAESAR IIs dynamicyseonly on linear systems, so any non-linearitiesmust be linearized prior toysis. This meanst one-directional restras will not lift ondreseat, gaps

2、will not open and close, and friction will not aa constant effort force.Therefore,for dynamicyses, all non-linear effects must be med as linear - for exle, aone-directional restramust be med as either seated (active) or lifted off (inactive), and agap must be either open (inactive) or closed (active

3、).This pros is automated when the sicload case iected here - CAESAR II automatically activates the non- linear restrashesystem to correspond to their sushe selected load case (the user may think of this as beingthe loading condition - for exload occurs).It must be notedle Operating - of the system a

4、t the time at which the dynamict this automated linearization does not always provide anappropriate dynamic mmanually alter the restra, and it may be nesary to select other sic load cases or even tocondition in order to simulate the correct dynamic response.A sic load case must precede the dynamics

5、job whenever:1) There are spring hangers to be designedhe job.The sic runs must be made in order todetermine the spring rate to be usedhe dynamic m.2) There are non-linear restras, such as one-directional restras, large-roion rods,bi-linear restras, gaps, etc. in the system.The sicysis must be made

6、in order todetermine the active sus of each of the restras for linearization of the dynamic m.3) There are frictional restrashe job, i.e. any restras winonzero(mu) value.3Sic Load Case for NonlinearRestraSus动态分析是线性的分析，在开始建立分析模型之前，选择哪个工况作为开始。STIFFNESS FACTOR FOR FRICTION (0.0-NOT USED)(Active for:Har

7、monic, Spectrum, Modal, Range, and Time History)All of CAESAR IIs dynamicyses are currently linear, so non-linear effects must belinearized.Ming of friction in dynamic ms presents a spel case, since frictionactually impacts the dynamic responsewo ways - sic friction (prior to breakaway) affects thes

8、tiffness of the system, by providing additional restra, while kinetic friction (subsequent tobreakaway) actually affects the ding component of dynamicresponse; due to mathematicalconstras, ding is ignored for allyses except time history (for which it is only consideredon a system-wide basis). CAESAR

9、 II allows friction to be takeno account through the useof this Friction Stiffness Factor. CAESAR II approximates the restraining effect of friction on thepipe by including stiffnesses transverse to the direction of the restra specified.The stiffness of these frictional restras is computed as:Kfrict

10、ion = (F)*()*(Fact)Where:at which friction wasKfriction = stiffness of frictional restrainserted by CAESAR IIF= the force at the restra= mu, friction coefficientaken from the sic solutionrestra, as definedhe sic mFact= Friction Factor from the control spreadsheetThis factor should be adjusted as nes

11、ary in order to make the dynamic msimulate thesystemual dynamic response (notet use of this factor does not correspond to any actualdynamic parameter, but is actually a tweak factor to modify system stiffness).Entering afriction factreatern zero causes these friction stiffnesses to be insertedo the

12、dynamicsjob. Increasing this factor correspondingly increases the effect of the friction. Entering a frictionfactor equal to zero ignores any frictional effecthe dynamics job.MAX. NO. OF EIGENVALUES CALCULATED (0-NOT USED)(Active for:Spectrum, Modal, and Time History)Thestage of the Spectrum, Modal,

13、 and Time Historyyses, is the use of the Eigensolveralgorithm to extract thsystems natural frequencies and mode shs.For the Spectrumand Time Historyyses, the response under loading is calculated for each of the modes, withthe system response being the sum of the individual modal responses.Obviously,

14、 the moremodest are extracted, the more the sum of those modal responses resembles the actual systemresponse.The problem ist this algorithm uses an iterative method for finding sucsivemodes, so extraction of a large number of modes usually requires muore timen does asic solution of the same pisystem

15、.The object is to extract sufficient modes to get asuitable solution, without straining compuional resour. CAESAR II permits the user tospecify - either through a mode number cutoff or a frequency cutoff - the number of modalresponses to be includedhe system results.This parameter is used, in combin

16、ation with the0Max.No.of Eigenvalues Calculated (0 - Not Used)解释这个含义0.0StiffnessFactorfor Friction (0.0-Not Used)解释这个含义Frequency Cutoff described below, to limit theum number of modes of vibration to beextracted during the dynamicysis.If this parameter is entered as 0, the number of modesextracted i

17、s limited only by the frequency cutoff (and potentially, the number ofdegrees-of-freedomhe system m).If theyst is moreerested in providing an accurate represenion of the systemdisplacements, it may only be nesary to request the extraction of a few modes, allowing a racalculation time.However, if an

18、accurate estimate of the for, stresses, etc.he system is theobjective, calculation time grows as ites nesary to extract far more modes.This isparticularly true in the case when solving a fluid hammroblem in the presence of axialrestra s; often modes with natural frequencies of up to 300 Hz can be la

19、rge contributors to the solution.The usual procedure for determining how many modes are sufficient is to extract a certain number of modes and review the results; then to repeat the ysis while extracting 5 to 10additional modes, and comparing the new results to the old. If there is a significant cha

20、ngebetn the results, a newwere extracted for the secondysis is made, again extracting 5 to 10 more modes above thosetrysis.This iterative pros continues until the results toff,involveding asymptotic. This procedure has two drawbacks, theone obvious - the timeaking the multipleyses, as well as the ti

21、me involved in extracting the potentiallylarge number of modes.The second drawback, occurring with Spectrumysis, is less obvious- a degree of conservatism isroduced when combining the contributions of the higher ordermodes. methodsthe rigidsible spectral mode summation methods include SRSS, ABSOLUTE

22、, and GROUP - allt combine modal results as same-sign (itive) values.In reality, theory sestmodes actually act in phase with each other, and should therefore be combinedalgebraically, thus permitting the response of some rigid modes to cancel the effect of other rigidmodes (this iually what occurs i

23、n a time historyysis).Because of this conservatism, it isactuallysible to get results which exceed twice the appd load, despite the factt theDynamic Load Factor (DLF) of an impulse load cannot be greatern 2.0.ternative method of ensuringt sufficient modes are consideredhe dynamic misthrough the use

24、of the Included Mass Data Report.This report (available from the DynamicOutput Screen) is compiled for all spectrum and time history shock cases, whether missing mass(see descriptionhe section Include Missing Mass Components) is to be included or not.Itdisplays the percent of system mass along each

25、of the three global axes, as well as the percent of total force, which has been captured by the extracted modes. The percent of system mass active along each of the three global axes (X-, Y-, and Z-) is calculated by summing themodal mass (corresponding to the appropriate directional degree-of-freed

26、om) attributed to theextracted modes and dividingt sum by the sum of the system masinghe same direction.Frequency Cutoff (HZ)(Active for:Spectrum, Modal, and Time History)As noted above, CAESAR II permits the user to specify either a number of modes or a frequencycutoor extracting modes to be consid

27、eredhe dynamicysis.Modal extraction ceaseswhen the Eigensolver extracts either the number of modes requested, or extracts a mode wifrequency abovet of the Frequency Cutoff, whichever comes. Onemendation forselection of a frequency cutoff poist the user extract modes up to, but not far, a40Frequency

28、Cutoff (Hz)recognized rigid frequency, and then include the missing mass correction (discussed in thesection Include Missing Mass Components). Choosing a cutoff frequency to the left of the response spectrums resonant peak will provide a non-conservative result, since resonantresponses may be missed

29、.During spectrumysis, using a cutorequency to the right of thepeak, but still in the resonant range, will yield either overly- or underly-conservative results,depending upon the method used to extract the ZPA from the response spectrum. (he case oftime historyysis, selecting a cutorequency to the ri

30、ght of the peak, but stillhe resonantrange, will probably yield non-conservative results, since the missing mass force is appd widynamic load factor of 1.0).Extracting a large number of rigid modes for calculation of thedynamic response may be conservative in the case of Spectrumysis, since allspect

31、ral modal combination methods (SRSS, GROUP, ABS, etc.) give conservative results versusthe algebraic combination method (always used during time historyrealistic represenion of the net response of the rigid modes.ysis), which gives a moreWhen theysis type is SPECTRUM, MODES, or TIMEHIST, either this

32、 parameter or theprevious one must be entered.CLOSELY SPACED MODE CRITERIA/TIME HISTORY TIME STEP (MS)(Active for:Spectrum/GROUP and Time History)This parameter does double duty, depending upon theysis type. For a Spectrumysis typewith GROUP modal Combination Method (as defined by USNRC Regulatory G

33、uide 1.92), thisparameter specifies the frequency spacing defining each modal group - i.e., the percent (ofthe base frequency) betn the lowest and highest frequency of the group. Regulatory Guide1.92 specifies the group spacing criter10% (entered here as 0.1), so it is unlikelyt the userwould ever w

34、ish to change the Closely Spaced Mode Criteria from the CAESAR II default valueof 0.1. For a Time Historyysis type, this parameter is used to enter the length of the time slice,illiseconds, to be used by the program during its step-by-stntegration of the equations ofmotion for each of the extracted

35、modes (CAESAR II uses the unconditionally stable Wilson qegration method, so any size time step will provide a solution, wismaller step providinggreater accuracy -sufficiently small should be smallerand more strain on compuional resour). The time step should bet it can accuray map the force vs. time

36、 load profile (i.e., the time stepn typical force rtimes).Additionally, the time step must be smallenought the contribution of the higher order modes is not filtered from the response.For thisreason, it istimesmendedt the time step should be selected sucht Time Step (in seconds)le, if the modal freq

37、uencyum Modal Frequency (in Hz) be lessn 0.1.For excutoff is set to 50 Hz, the time step should be set to aHz = 0.1um of milliseconds: 0.002 sec x 50Re-use Last Eigensolution(Active for:Spectrum and Time History)When repeating a dynamicysis, this parameter may be set to Yes, causing CAESARII toNRe-u

38、seLast Eigensolution (Frequencies andMode Shs)解释这个含义0.1CloselySpaced Mode Criteria解释这个含义skip the eigensolution (reusing the results of the earrysis), and only perform thecompuions for displacements, reactions, for, and stresses.Activating this option is onlyvalid after an initial eigensolution has b

39、een performed and is still available.Additionally, themass and stiffness parameters of the minvalid.must be unchanged or the previous eigensolution isSpatial or Modal Combination(Active for:Spectrum)This directivels CAESAR II whether to combine the Spatial components or the Modalcomponents of the lo

40、ad case. When performing a spectrumysis, each of the modalresponses must be summed.In addition, if multiple shocks have been appd to the structure inmoren one direction, the results from different directions must be combined - for exle,spatially combining the X-direction, Y-direction, and Z-directio

41、n results. The question arises as towhether the spatial summations should precede or follow the modal summations.A difference inthe final results (of Spatialvs. Modal) arises whenever different methods are used for thespatial and modal combinations. The combination of Spatial componentsshock loads a

42、re dependent, while the combination of Modal componentsimpsimpst thet the nshock loads are independent. Dependent and Independent refer to the time relationship betthe X, Y, and Z components of the earthquake.Widependent shock case, the X, Y, and Zcomponents of the earthquake have a direct relations

43、hip - a change in the shock along onedirection produa corresponding changehe other directions.For exle, this would bethe case when the earthquake acts along a specific direction having componentsoren oneaxis - such as when a fault runs at a 30o angle betn the X- and Z-axes.In this case, theZ-directi

44、on load would be a scaled (by a factor of tan 30o), but otherwise identical verof theX-direction load.his case, spatial combinations should be made.An Independent shock ishere the X, Y, and Z time histories produce related frequencyspectra but have compley unrelated time histories.It is the Independ

45、ent type of earthquaket is far more common, and thusost cases the modal components should be combined.For exle, IEEE 344-1975 (IEEEmended Practifor Seismic Qualification of Class1E Equipment for Nuclearer Generating Sions) ses: Earthquakes produce randomground motions which are characterized by simu

46、ltaneous but sistically INDEPENDENThorizontal and vertical components. This is usually less of an ie for force spectrumcombinations, since normally there are no separate spatial components to combine - i.e., there arenot X-, Y-, and Z-shocking simultaneously. However,he eventt there is moren onepote

47、ntial force load (such as when there is a bof ref valvest can fire individually or incombination), the spatial combination method may be used to indicate the independence of theloadings.For exle, if two ref valves may or may not fire simultaneously (i.e., they areindependent), the two shocks should

48、be defined as being in different directions (for exle, X-and Y-), and the combination method selected should be Modal before Spatial.If under certaincircumstan, the two valves will definiy open simultaneously (i.e., the loadings aredependent), the combination method should be Spatial before Modal.(O

49、therwise, the directiondefined for a forpectrum loading has no particular meaning.)MODALSpatial or Modal Combination解释这个含义Nuclear Regulatory Guide 1.92 (published in February, 1976) describes the requirements forcombining spatial components when performing seismic response spectraysis for nuclearlan

50、ts.Notet since all Time History combinations are done algebraically (in-phase)this parameter has no effect on Time History results.Spatial Combination Method (SRSS/ABS) (Active for:Spectrum)This parameter is used to define the method for combining the spatial contributions of the shocksin a single s

51、pectrum load case. This option is only used for spectrum runs with moren a singleexciion direction.Since directional forare usually combined vectorially, this pos to aSquare Root of the Sum of the Squares (SRSS) combination method as being most appropriate.An Absolute method is provided for addition

52、al conservativism.Notet since all Time History combinations are done algebraically (in-phase) this parameterhas no effect on Time History results.Modal Combination Method (GROUP/10%/DSRSS/ABS/SRSS)(Active for:Spectrum)During a spectrumysis, responses are calculated for each of the individual modes;

53、theseindividual responses are then combined to get the total system response.Consideringt theresponse spectrum yields theum response at any time during the course of the appd load,and considering t each of the modes of vibration will probably have different frequencies, it is probable t the peak res

54、ponses of all modes will not occur simultaneously. Therefore an appropriate means of summing the modal responses must be considered. Nuclear RegulatoryGuide 1.92 (published in February, 1976) defines the requirements for combining modal responseswhen performing seismic response spectra presented the

55、re are also available, along non-nuclear seismic and force spectrummethods:ysis for nuclearwith one other, forlants.The four optionsmodal combinations underyses. There are 5 available modal combination1) GrouGrouMethod:This method is defined in USNRC Regulatory Guide 1.92.TheMethod attempts to elimi

56、nate the drawbacks of the Absolute and SRSS methods (seebelow) by amingt modes are compley correlated winy modes with similar (closelyspaced) frequencies, and are complefrequencies. Effectively, this method frequencies within 10% of each othery uncorrelated with those modes with widely differentdice

57、st the responses of any modes which havebe added together absoluy, with the results of each ofthese groups then combined with the remaining individual modal results using the SRSS method.Notet the 10% figure controlling the definition of a group may be changed by using theClosely Spaced Mode Criteri

58、a/Time History Time Step (ms) parameter.SRSSModal Combination Method (Group/10%/DSRSS/ABS/SRSS)解释这个含义SRSSSpatial Combination Method(SRSS/ABS)解释这个含义2) Ten Percent Method:This method is defined in USNRC Regulatory Guide 1.92.The TenPercent Method is similar to the GrouMethodhat it amest modes are comp

59、leycorrelated with any modes with similar (closely spaced) frequencies, and are compleyuncorrelated with those modes with widely different frequencies.The difference betn thisone and the preceding method ist the GrouMethod amest modes are onlycorrelated with thoset fall withhe group - i.e., are with

60、in a 10% band, while this methodamest modes are correlated with thoset fall within 10% of the subject mode - effectivelycreating a 20% band - 10% up and approximay 10% down. Notet the 10% figure controllingthe definition of closely spaced frequencies may be changed by using the Closely Spaced Mode C