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动力边界模型对土与结构非线性动力系统数值计算影响的分析

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维普资讯 http://www.cqvip.com 第7卷第l5期2007年8月 科学技术与工程 @Vo1.7 No.15 Aug.2007 1671—1819(2007)15—3803.08 Science Technology and Engineering 2007 Sci.Tech.Engng. 水利技术 动力边界模型对土与结构非线性 动力系统数值计算影响的分析 吴艺房营光 (华南理工大学建筑学院,广州510640) 摘要对不同参数条件下自由的远置边界、固定的远置边界、简单的远置边界、粘性局部人S-边界和粘弹性局部人S-边界 等动力边界模型对土与结构非线性相互作用数值计算的影响进行了分析,根据实例计算分析了各种动力边界模型的有效性、 数值计算量及计算结果的可靠性。分析结果表明:不同的远置边界模型,对地基计算的合理取值范围有重要的影响,而只要 地基的计算范围取得合理,都获得可靠的数值计算结果;粘性与粘弹性局部人工边界对数值计算结果虽有一定的影响,但具 有足够的可靠性,而且可把地基计算范围取得较小,大大地减小数值计算量,在满足工程设计计算精度要求的基础上有效地 节约计算成本。 关键词 非线性动力相互作用 中图法分类号TV312; 人工边界条件 A 可靠性 文献标识码ally truncated boundary must be treated properly in 1 Introduction time domain dynamic FEM.Three aspects must be taken into account,especilly in nonlineaar dynamic The analysis methods for soil—structure dynamic interaction can be categorized into frequency method and time method in solution domain and categorized in. to analytic method,numeric method,semi—analytic method,concentrated parameter method in solution methods at present….problems,when treating with fictitious boundaries: precision,cost and numeric stability.Global artiifcila boundaries[ ]have great precision.but the coupling in time and space limits their wide application.Signii— fcant boundaries[ , ’ 一l0]also have high precision.but Because nonlinear problems can cost a lot.Viscous and viscous—spring local artifcil aboundaries【 .4]together with signiicant boundarfies, ,be treated in time domain and the FEM iS characterized with high precision,well adaptability,matured in corn— mercil,starong function,etc.,FEM in time domain is the most popular method for analyzing soil—structure nonlinear dynamic interaction problems.In order to simulate wave propagating in infinite base,the fiction一 have widely used in dynamic FEM for their good preci— sion,little cost and well stbiality.However,different dynamic boundary models have different rational boundary scopes.In order to make clear the effect law of dynamic boundary models and base parameters, etc.,on rational boundary scopes,and the correspond— 2007年1月15 13收到 ing effects on calculation cost and reliability,some cal— culation instances of base・.sluice gate nonlinear dynam.. 第一作者简介:吴艺,男,(197一),华南理工大学土木工程系 博士生,研究方向:土与结构动力相互作用。E.mail:W.em@ 163.tom。 ic interaction problems were carried out in this paper. Researches show that different dynamic boundary mod. 维普资讯 http://www.cqvip.com 38O4 科学技术与工程 7卷 els have great effect on rational base calculation range; free,fix and simple dynamic boundary model can get same results under their own rational base calculation range;viscous and viscous—spring local dynamic artii— fcial boundary model may lose some precision,but still have enough reliability,and the smaller base calcula— tion range is allowed without exceeding engineering precision limit,SO they can save a lot of computer re— layer soils totally and the mass of water and equip— ments was treated as plus one according to document [。 .The base constitutive equation takes Drucker— .Prager model[ ・。 which has the following 5 param— eters:elastic modulus,minor Poisson’S ratios,cohe— sion,angle of internal friction and dilatation angle. The dilatation angle takes zero in this paper,and the 0ther parameter values are shown in table 1.The ma— source and calculation cost. terils ofa brace,sluice room and stirring piles are thought to be linearly elastic,and contact elements 2 The calculation models of soil-structure nonlinear dynamic systems are introduced to simulate the contact behavior be— tween piles and soil.Yb=97 m and Xb is determined bv trial calculation.The lateral boundary condition is The dynamic system discussed in this paper con— sists of upper brace,sluice loom,reinforced base with deep stirring piles and natural base,as shown in depended on analysis need.The radius,space,and length of piles are d=400 mm.s=3 d[。 ]and Z---20 m respectively The firction coefifcient can take{:0. 33 with precisi0n and practice consideration[。 '。4]. Fig.1.The system is simpliifed as a plane strain mod— el by taking unit long base and structure perpendicular t0 liver flow.In this system,structure,base and deep stirring piles were modeled respectively.There are 6 The seismic excitation takes Nanjing seismic record, whose acceleration and displacement time history CUI'Ves are shown in Fig.3. Table 1 Parameter values of materials Note:1.The data in the table is referencod to the anti—seismic calculation and security evaluation of sluice structure of Chaozhou water supply hub, Chan ̄ing aScience Institute,2003,6 2.The data in parenthesis is used in later small modulus and big damp analysis・ 维普资讯 http://www.cqvip.com 暑glO O  elp 15期 吴艺,等:动力边界模型对土与结构非线性动力系统数值计算影响的分析 38O5 Fig.1 Sluice—base nonlinear dynamic model(unit:m) .2 0 2 4 6 8 10 12 14 16 18 -2 0 2 4 6 8 10 12 14 16 18 (a)Acceleration time history (b)Displacement time history Fig.2 Nanjing seismic record 3 The analysis of dynamic boundary model effects on numeric calculation As mentioned above,in order to simulate wave propagating in infinite base,the fictionally truncated boundary must be treated properly in time domain dy- namic FEM.At present,dynamic boundary model can be classiifed into three categories:signiifcant bounda- yr,global artificial boundary and local artiifcial bound- ary.Of which,significant boundary can still be treated as fix boundary[ (a zero displacement is enforced), free boundary (a zero surface traction is enforced) and simple boundaries[ _ according to different treat- ment methods.Simple boundaries are some special boundary conditions for some special situation.For ex- ample,when a SV wave propagates vertically,the 1at- erla boundary can be constrained vertically but free horizontally.The mature local artificial boundaries in‘ clude Viscous Boundary[】5].Viscous.Spring Bounda- yr[16]Transmitting Boundary[17],,Paraxial Approxima- tion Boundary ̄ 8。Absorbing Boundary[19]and Unified .Boundary[驯etc..Significant boundaries.viscous lo- cal artificial boundary and viscous-spring artiifcial boundary are widely used for their clear concept,feasi- ble,good precision and well stability.Global artiifcial boundary cannot be popular for its coupling in time and space.The compare research of free boundary,fix boundary,simple boundary,viscous boundary and vis- COUS-spring boundary was proceeded below in order to determine the law of their effects on rational boundary scope,computer resource and calculation time cost, and the reliability of result,which is hope to be a ref- erence for researchers and engineers in their practice. 3.1 The dynamic boundary model effects on ra- tional boundary scope In this session,research of various dynamic boundary models’effects on Xb was made by analyzing the sluice.base nonlinear dynamic instance in Fig.1. In this instance,displacement response was observed. Judging from present knowledge,the displacement of point A in Fig.1 would be fairly large,so point A can be looked as observed control point. hTe effects of various dynamic boundary models on Xb are shown in Fig.3,where the vertical axes in- dicate the displacement response of point A in Fig.1; L is the structure dimension in horizontal direction. Fig.3(a)一(c)and Fig.3(d)一(e)are the dis- placement response of significant boundaries and local artiifcial dynamic boundaries respectively.As seen from the Fig.3,the responses corresponding to various dynamic boundaries all tend to their own some value respectively as their boundary scope increase.The Xb corresponding to the stable response is called rational boundary scope.Different dynamic boundary models have diiferent rational boundary scopes. 维普资讯 http://www.cqvip.com 38O6 暑、《lu10盘 菪u暑0譬_IdsIp 科学技术与暑 工程 lu10口 luu暑u譬Id∞Ip 0 04 O.o2 0.O0 O.02 0.4 00.06 0 08 0.10 0 l2 0.14 0 l6 0.18 0 20 0.22 O24 0.26 O 28 0-30 7卷 』 1 O O5 0 O0 ..■ .{蕾 ,- 、 / \ / ’^一 、-./I Tl|’ 一.—.-■ .、I1 L-■ 。 ∥ J , 、一 j ● 0 O5 0 l0 5 } , ....0 l5 ・一  L=11 =—21 -0.2O .+x0L=31 ; } } I  {‘ ’ l 、 /1 L i, , I 、 、 J ...——-_ , :1 1 ,L=:21 , =:31 ...t一虬,£=4l ・~ L=51 .十X0L--41 —弋 O V O r】瘩0 等0.25 0-30 0 .+ ,L一5 1 l l ...2 4 6 8 10 l2 l4 l6 0 2 4 6 8 time/s l0 l2 l4 l6 time/s (a)Free lateral boundary (b)Fix lateral boundary 0.05 0.O0 -o.05 -o.10 -o l5 J■J|1- 暑,v lu_oc一 luu暑uoB1dsIp .srst' ̄ { f 暑\《_go4苗luu暑uo旦4矾Ip O O I ,,--一| t r ; } { \ 、 I ≮ 一 l lf  ・ x0L:3 XdL=-0.20 -0.25 .0 30 …I:l J l :.-』 2 4 6 8 time/s l0 l2 l4 \ 、. l6 0 +x—・一 £0l =11 —7 _~^ ; 、 主 l2 l4 l6 0 2 4 6 8 l0 itme/s (C)Simple lateral boundary (d)Viscous lateral bou,a ̄y J—● 、|  .I i } l | I fl  t l \ f —●・一*一^ /L— I1 1 } 一・一 L ———・一XJL=15 0 2 4 6 8 l0 l2 l4 l6 ttme/s (e)Viscous—spring lateral boundary Fig.3 Dynamic boundary models’effects Oil rationM boundary scope 维普资讯 http://www.cqvip.com l5期 目\《luIoA瓮苗。目。 Id∞Ip O O 吴艺,等:动力边界模型对土与结构非线性动力系统数值计算影响的分析 0 3807 changes in local artificial dynamic boundaries are all h● H _. very slim.The rational boundaries corresponding to va-  .}  .— 毫 \ |  1I I l I 建 6 8 tune/s rious dynamic artificil boundary models aare shown in table 2.  。3.2 The effects of dynamic boundary models oil the reliability of:calculation results  ,f饽e ●一 ‘ 一▲v●““s榍懵' cDoIe  —’--vbcOu 0rIl'a Fig.4 shows the effects of different dynamic  10 2 4 l0 l2 l4 l6 boundary models on the reliability of calculation results wi出rational scopes.As seen in Fig.4.there are the response curves of free,fix and simple boundary super- Fig.4 Dynamic boundary models’effects on reliability of results position.Documents keys.[2 ,6]point out that he results wit}It significant boundary are accurate nu- Fig.3 shows that local dynamic boundary condiitons are far better than significant ones in the term of cost. The rational boundary scopes of viscous and viscous- spring local artificial dynamic boundaries are 15 and 11 meric ones.So a conclusion can be drawn that the type of sinigifcant boundary(free,fix or simple)has no effects on the rehability of calculation.But for viscous and viscous-spring artiiciafl boundaries,the results would have some error compared to accurate ones, which is coincided to documents[2 ]’ conclusion that v ̄iscous and viscous-spring artificial boundaries have only one order precision.So for viscous and viscous— times as lrge asa structure dimension.But in signii-f cant boundaries,the rational boundary scopes of free, ifx and simple boundary are 41,51 and 21 times as lrge as stauctrure dimension.Fig.3 also shows that in local artiifcil boundaraies,viscous—spring artiifcil aboundary is better than viscous one;in signiifcant boundaries,simple bounda/'y isthe best and it is far .spring local artfciil boundaraies,the relibiality of their results would be affected in some degree.It is also seen from Fig.4,the precision of viscous—spring boundary is better than that of viscous one,which rea— son is that:viscous--spring can not only eliminate the re—- better than fix and free ones;fix boundary is he wont,t and free boundary is only a little better than fix one. What's more,when Xb is less than rational boundary scope,the change of response vs.Xb in free,especial- lfection wave on artiifcil aboundaries,but lso siamulate the inevitblae attenuation of wave amplitude during its  propagation.This.is coincided to document[。’ .ly fix boundary is larger than simple one,and these . Table 2 The effects of various dynamic boundary conditions on calculation costs Signiifcant boundarios' Local artificial boundaries Simple boundary Viscous boundary Vicous-sspring boundary Boundary condiitons. Free boundary Fix boundary Rationalboundaryscopo(Xb・L一‘) Number of elements Size ofinputfile/MB Size of result ilfes/GB Calculation time 41 6523 29.8 20.6o9 7:19 52 >51I 7723 33.8 24.695 4:45 33 21 4123 22.3 12.632 4:22 53 15 3673 22.5 10.161 2:31 17” 11 3153 20.1 8.579 2:11 38 Note:The meshing methods ale 8anle in various boundary calculation models so that the same parts of various models have the some element topology 维普资讯 http://www.cqvip.com 科学技术与工程 7卷 3.3 Effects of dynamic boundary models on corn- purer resource and time cost As mentioned above,diferent a ̄iifcil dynamiac boundary models would affect rational boundary that it can almost be inored.Butg the comparing be・ tween Fig.6 and Fig.3(e)shows that tll the base damp increasing,not only is the structure response af- fcteed markedly,but also rational boundary scope changes markedly.When damp increases by 4 times, rational boundary scope almost decreases by 4 times.It shows that damp has remarkable effect on rational scopes,and size of the scope would affect the cost of computer resource and calculation time.Even if the boundary SCOpeS are same,but diferent artiifcil dy・a namic boundary would require diferent calculation itme.The effects of diferent artiifcila dynamic bounda・ yr models on computer resource and calculation cost are detmled in table2.It can be seen from tbale 2,the most economical boundary model is viscous・spring local artiifcila dynamic boundary model,and the most ex・ pensive one is fix signiifcant one.The rational obunda・ yr scope of viscous・spring boundary is only 1/5 that of ifx.singiifcant boundary;the number of elements and calculation time of the former are less than half of hte latter and the size of result files of the former is also only about 1/3 that of the latter.One conclusion can be drawn that among the dynamic obundary models lis・ ted in table 2,viscous・spring boundary is the best if only with the cost of computer resource and calculation itme regarded. 4 The analysis of parameters effects on nu‘ meric calcuiation It can be predicted that diferent base parameters would affect rational boundary scope because they may faect the speed of wave propagation and aRenuation. .Fig.5 and Fig.6 are the responses corresponding to smla.l modulus and big damp condition in parenthesis in tbale 1 wiht viscous・spring lateral local artiifcial bound・ ary.It van be seen by comparing Fig.5 with Fig.3 (a)that the response changes with the base elastic modulus’change,but the rational boundary scope changes little,which shows that the effect of base elsa・ tic modulus on rational boundary scope is very slim so boundary scope,and this effect is almost linear.It will not be rigorous enough to say simply rational boundary scope should be n times as lrage as that of structure di・ mension because the effect of base parameters is ig— nored.Diferent documents have different conclusion about rational boundary scopes[ ]because they are based on diferent soil parameters. O O . , ∞ 。 A I l f .宣 ’墓 I f ; 苎 £ l / ▲、●r ■ 器 —一十l {—・~ 也五 :7 i:3;,  J/ T  l喜 十五 :11 0 2 4 6 8 10 12 14 16 time/s Fig.5 stnlcture resp0nse under smaIl base m。duIus 0.05 0.00 J■▲ - .0.05  ..0.10 I、L .0.15 1. 产 j .0_20 +五 :3 l —●一玉 .7} .0_25 ▲一XJL=I11 .0_30 0 2 4 6 8 10 12 14 16 time/s Fig.6 Structure response under large base damp 盎-、《维普资讯 http://www.cqvip.com 15期 吴 艺,等:动力边界模型对土与结构非线性动力系统数值计算影响的分析 38O9 5 Conciusions 1 Zhang Chuhan.Structure・base dynamic interaction problems.In:E d Several conclusions call be drawn through the analysis above: Cao ghinan.Theoryy of structure and media interaction and its appli・ cations.Nanjin8:Publisher of Hehai University.1993.243—266 (in Chinese) (1)It is not irgorous enough to give a uniform ra— tional boundary scope because diferent dynamic oundary modelbs and base parameters have great effect on it.In signiifcant boundary models,rational bounda— ry SCOpe of simple boundary is the smallest,and that of 2 Zhao Mi.Compare research between viscous・spring artiicifal boundary nd taransmititng artificial boundary.Beijing University of Technology, 2004.3 f;n Chinese) 3 Zhang Dongyin.The application of LS—DYNA to soil・s ̄cture dy・ nanlic interaction.The Engineering Mechanic insittute of China Seis— ifx boundary is the largest;the one of free boundary is a little smaller than that offix boundary.In local artifi・ cial boundaries,rational boundary scope of viscous mic Bureau,2003.29(in Chinese) 4 Fang Yinggnang.The theory of rock and soil media and structure dy— namic interaction and its applications.Beijing:Science Publiher。s 2005.288(in Chinese) 5 AltermanZ/S.KarulF/C/J.Propagation ofelasticwavesinlay- ered media by fiitne.diference methods.Bulletin of the Seismological oundary ibs a little smaller than that of viscous・ spring's.Generally,rational boundary scope of local artiifcil baoundary is smaller than that of Society of America.1968,58(1):367—398 6 Wang Yigong,Yang Youfa.The second development of ANSYS for sinigifcant one. the seismic response f siote.Earthquake Engineering and engineering vibration,2004,24(2):42—145(in Chinese) 7 Shen Jumin,Zhou Xiynan.Anti—seismic engineering.Beijing.Chia nArchitecture and Building Press,2000.254(in Chinese) 8 W01f J P.1 ̄nlllnic soil・structure Interaction.New J删Hall inc,1985,275 (2)Diferent dynamic boundaries have diferent effect on the relibiality of calculation results.The types of signiifcant boundaries(free,fix or simple)have no effect on the relibiality of calculation results.All the results th signiifcant boundary are accurate numeric results.But viscous and viscous—spring local artfciil aoundarbies have some precision loss,and the loss of viscous boundary is a little greater than that of viscous— spring boundary. :Prentice・ 9 Liu Pujun.The analysis of dynamic interaction betwen the base of stone dam and soil under seismic condiiton.Chongqing Institute of Communication,2003.58(in Chinese) 10 Tao Mingxing.The analysis of dynamic interaction betwen soil and subs ̄cture wih FEM.X/tbei University of Technology,2004,35 (3)If hig}I precision nd alow cost are required, signiifcant simple boundary is a g00d choice,but its rational boundary scope should be determined by tril acalculations.If he costt saving is at the fistr place in・ stead of precision requirement,viscous-spring ounda-b y irs recommended.The rational boundary of viscous・ (in Chinese) II The professional standard compilation group of people's republic of Chia.Specinfication for Seismic Design of Hydramie Strutures (SL203 97).Beijing:China Waterpower Press,1997 12 ANSYS Inc.Theory Reference 13 Niu Zhirong,Li Hong,Mu Jinchun。eta a1.Composite foundation treatment and its engineering application.Beijing:Chia Constnrue— spring boundary can take faifly small without losing d鲫Material Press,2000,453----454(in Chinee)s 14 Qian Jiahuan,Yin Zongzhe.The principle and calculation of soil engineering.Beijing:Chia Watnerpower Press,1994;402(in Chi— nese) 15 Lysmer J。KuhlemeyerRL.Finite dynamicmodelforinfinitemedia. much of precision.Viscous—spring boundary has good stbiality and can be well introduced by existing lrge ascale commercil FEM praograms,so it is a good local dynamic boundary model in dynamic FEM at present. Pro ASCE EM4,1969;(8):859 16 Decks A J。Randolph M F.Axisymmetric time・domain transmitting Boundaries.Journal of Engineering Mechanics,1994。-/20(1): 维普资讯 http://www.cqvip.com 3810 科学技术与工 程 7卷 25—42 Lysmer J,Waas G.Shear waves in plnae infinite structures.Joumal l7 Ang H S,Newmark N M.Development of a transmitting boundary for ofthe Engineering Mechanics ASCE,1972,98(1):85一lo5 numerical wave motion calculation.Report 2631,Defense Atomic 21 LI Peizhen,Lu Xilin.Numerical analysis of tall buildings consider- Support Agency,1972,1 ing dynamic soil—structure interaction.Earthquake Engineering and 18 Clayton R,Engquist B.Absorbing boundary conditions for ac oustic Engineering Vilb'ration,2004,24(3):l3O—l38(in Chinese) and elastic wave equations.Bull Seism Soc Amer,1977;67 Lu Aizhong,Jinag Binsong,Long Chunan.Study on range of mesh (6):1529 about ifnite element for baek analysis of sisplacement.China Civil 19 Engquist B,Majda A.Absorbing boundary conditions for numerical Engineering Journal,1999,32(1):26—3O(in Chinese) solution of wave.Mathematics of Computation,1977;3 1(9):629 Analysis of Dynamic Boundary Model Effects on Soil-structure Nonlinear Dynamic System Numerical Calculation WU Yi.FANG Ying—guang (Architecture and Civil Engineering College,South China University of Technology,Guangzhou 510640,China) [Abstract]The efects of various dynamic boundary models,such as free boundary,fix boundary,simple boundary.viscous local artiifcila boundary and Viscous唱pring local aaiifcila boundary with diferent paI砌leters on the numerical calculation of soil—structure nonlinear dynamic interaction system ware analyzed in this paper.The ef- J  。・ ifcieney and resource consumption of various dynamic boundary models and the reliability of numerical results were laso discussed.Researches show that diferent dynamic boundary models have great effect on rational base calcula‘ tion range;free,fix and simple dynamic boundary model can get same results under their own rational base calcula‘ tion range;viscous and viscous—spring local dynamic artiifcila boundary model may lose some precision,but sitll have enough reliability,and the smaller base calculation range is allowed without exceeding engineering precision limit,SO they can save a lot of computer resource and calculation cost. [Key words] nonlinear dynamic interaction artiifcila boundary condiiton libaility 

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