結(jié)構(gòu)動(dòng)力學(xué)大連理工土木水利學(xué)院

院DalianUniversityof第I單自由第2－3工程抗震InstituteofEarthquakeEngineering院§2-1基本動(dòng)力體系的kcmkcmkcmDaliankcmDalianUniversityof工程抗震InstituteofEarthquakeEngineering

2014-12-01 院DalianUniversityofmcc工程抗震InstituteofEarthquakeEngineering

2014-12-01 院體系質(zhì)量 彈性特性（剛度或柔度）k能量耗散機(jī)制或阻 DalianUniversityof每個(gè)特性都假設(shè)集結(jié)于DalianUniversityof研究單自由度體系的自由振動(dòng)重要性在塔、單層廠房1、它代表了許多實(shí)際塔、單層廠房InstituteofEarthquakeEngineering2014-12- 2、它是分析多自由度InstituteofEarthquakeEngineering2014-12- 工程抗院v(t院v(tkmp(tcv(t受力Fsmp(tv(t受力Fsmp(tF(tdDalianUniversityof

2014-12-01 院

FsFdDalianUniversityof粘滯（或粘性）阻尼（ViscousDalianUniversityofRcdv(t)外力（External

InstituteofEarthquakeInstituteofEarthquakeEngineering2014-12- 院FFsFdp(t)kv(t)cv(t)p(t)DalianDalianUniversityof單自由度系統(tǒng)的運(yùn)動(dòng)方程（Equationof工程抗震InstituteofEarthquakeEngineering

2014-12-01 院DalianUniversityDalianUniversityof由于δv的任意性，且不等工程抗震InstituteofEarthquakeEngineering

2014-12-01 院DalianUniversityofFFs(t)Fs(t)vv(t)v(t)工程抗震InstituteofEarthquakeEngineering

2014-12-01 院

Fs(t)kv(t)kst動(dòng)力平衡DalianUniversityofcv(t)kv(t)kstp(tDalianUniversityof去掉靜力平衡Δst與時(shí)間無(wú)工程抗震InstituteofEarthquakeEngineering

2014-12-01 院院DalianUniversityDalianUniversityofInstituteofEarthquakeEngineering2014-12- 性、彈性、InstituteofEarthquakeEngineering2014-12- 性、彈性、小變形的情工程抗院k2ck2f(t)v(t)v(t)vtgItfs(t)/

fD

fs(t)/DalianUniversityoffI(tDalianUniversityof

(t)

(t)阻尼力和彈性力只與相對(duì)

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DalianUniversityof DalianUniversityof地面運(yùn)動(dòng)一般測(cè)量的是加速度，此時(shí)需要 加速度積分得地面運(yùn)動(dòng)的速度和位InstituteofEarthquakeInstituteofEarthquakeEngineering2014-12- 院§院DalianUniversityDalianUniversityof

自由Particular自由振

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v(t)齊線性方程，通解取工程抗震InstituteofEarthquakeEngineering

2014-12-01 院

RealGGRG

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2014-12-01 院院kcsms2k/m2

DalianUniversityof方DalianUniversityof相對(duì)于k和m的

2

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2014-12-01 v(t)GeitG12v(t)(G1v(t)GeitG12院(G2RiG2I)(cos院v(t)(G1RG2R)cost(G1IG2I)sinti[(G1IG2I)cost(G1RG2R)sint]自由振動(dòng)必須是實(shí)的，虛部項(xiàng)必DalianUniversityofG1RG2RGRG1IG2DalianUniversityofA2GR;B

v(t)2GRcost2GIsint2Gcos(tAcostBsinv(t) iG)eit iG 常微分方程中有如下定G

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相位

程的解 院Dalian院DalianUniversityof

v(t)2GRcost2GIsint2Gcos(tAcostB iGI

iGI v(0)A2G;v(0)B v(t)v(0)costv(0)sin

v(t)cos(tv(0)2v(0)2[tan1BA

工程抗震InstituteofEarthquakeEngineering

2014-12-01 院

v(t)cos(t[

tan1DalianUniversityoff;T2 自振周期或固有周期（NaturalPeriodof工程抗震InstituteofEarthquakeEngineering

2014-12-01 院院2css2m

sc(c(c)22臨界c2m

低阻

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c/cc2222

超阻

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2014-12-01 院c2mccs1s2c2mccs1s2初始條件v(0)

個(gè)相同的實(shí)

G1和G2均為實(shí)G2v(0)DalianUniversityofDalianUniversityof

G v(t)[v(0)(v(0)

2mω是系統(tǒng)不出現(xiàn)振蕩的最工程抗震InstituteofEarthquakeEngineering

2014-12-01 超臨界院DalianUniversityof

c/cc2s22

工程抗震InstituteofEarthquakeEngineering

2014-12-01 院v(t)c c

v(t)(G GeiwDtc cs

為使反應(yīng)是實(shí)的，G1和G2必須為共軛D1阻尼體系的自D1阻尼體系的自振頻采用三角函數(shù) v(t)(AcoswtBsinw DalianUniversityofv(t)(w AsinwtwBcoswt)et(AcoswtBsinwt)et DalianUniversityofv(0)

Bv(0)Dv(t)(v(0)coswtv(0)v(0)sinw D工程抗震InstituteofEarthquakeEngineering

2014-12-01 院v(t)(v(0)coswtv(0)v(0)sinw Dv(t)cos(t D

[[]2D ;

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2014-12-01 院t,tt,t2/v(t)cos(Dt)e相鄰兩個(gè)正波峰的比：

/

e2DalianUniversityofDalianUniversityof11

ln

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2!取前兩

由此可見(jiàn)，對(duì)于粘滯阻尼自

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2014-12-01 院阻尼院1lnvn/ 1近似

DalianUniversityof這種測(cè)定阻尼系數(shù)的方法稱(chēng)為自振衰減法(FreeDalianUniversityof工程抗震InstituteofEarthquakeEngineering

2014-12-01 院

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2014-12-01 院m求自振頻m

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KK3EI工程抗震InstituteofEarthquakeEngineering

2014-12-01 院kkalDalianUniversityofml2kaDalianUniversityofm工程抗震InstituteofEarthquakeEngineering

2014-12-01 院1DalianUniversityofU DalianUniversityof2

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T1(mM)v2工程抗震InstituteofEarthquakeEngineering

2014-12-01 院2-DalianUniversityDalianUniversityof

第2工程抗震InstituteofEarthquakeEngineering

2014-12-01 院無(wú)阻尼自由振動(dòng)v(t2GRcost2GIsint2Gcos(tAcostBsinDalianUniversityofDalianUniversityof臨界阻

v(t)(GRiGI k/m2c2m

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c c 超阻

11

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2014-12-01 院

v(t 0 0

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2014-12-01 院 v(t)AcostBsintCsin系數(shù)A和B通過(guò)初始條件確定。對(duì)于由靜止開(kāi)始的運(yùn)動(dòng)

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2014-12-01 院v(t) 1院v(t) 112(sintDalianUniversityofDalianUniversityof工程抗震InstituteofEarthquakeEngineering

2014-12-01 院p(t)院Cp0 1 2Cp0 1 2v(t)v0sintvcost

costcost

22/2/DalianUniversityof工程抗震InstituteofEarthquakeEngineering

2014-12-01 院院22/2/DalianUniversityof工程抗震InstituteofEarthquakeDalianUniversityof

2014-12-01 院v(院v(t)v0sintvcost0costcost 非常小，但不等于

ε為一非常小的v(t)

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2014-12-01 院v院v(t)v0sintvcost0costcost率sintsinDalianUniversityof因?yàn)樽詈笠粋€(gè)等式中的ε非常小，所以函數(shù)sinεt變化緩慢，它的周期等于2π/ε，該值很大。因此，上式可以視為周期為2π/?，可變振幅等于p0/(2mε?)sinεt的振動(dòng)，這種振動(dòng)按下圖所DalianUniversityof工程抗震InstituteofEarthquakeEngineering

2014-12-01 院v(院v(t)sintvcostP 0 m(22costcost 20

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2014-12-01 院DalianUniversityof工程抗震InstituteofEarthquakeEngineeringDalianUniversityof

2014-12-01 院DalianUniversityof工程抗院DalianUniversityof

2014-12-01 11Dalian11DalianUniversityof

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2014-12-01 D D院DalianUniversityof院DalianUniversityof

2014-12-01 院0 0m

用待定系數(shù)法求該微分方程DalianUniversityofvp(t)A1costA2DalianUniversityof (t)A2costA2sin A2costA2sint2AsintAcost

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2014-12-01 ((21A2A)21t(A221A)sin22t0msin院DalianUniversityofDalianUniversityof

22A2A A22A2

m2224222

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2014-12-01 院vp(t)sintA212A212 DalianUniversityof相位tg相位

2 1工程抗震InstituteofEarthquakeEngineering

2014-12-01 院方院方程的通

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2014-12-01 院v(t)sint(12)2(2

[(12)sint2DalianUniversityofDalianUniversityofk

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2014-12-01 院D [(12)2(2)2]1/2p0/DalianUniversityof工程抗震InstituteofEarthquakeDalianUniversityof

2014-12-01 院tg

1 DalianUniversityof工程抗震InstituteofEarthquakeEngineeringDalianUniversityof

2014-12- 院P0[(1院P0[(12)2(2)2ktg1DalianUniversityof

2014-12-01 院DalianUniversityof工程抗院DalianUniversityof

2014-12-01 Determine院

2DalianUniversityofThuswiththedataofDalianUniversityoftg(22)tg15(27.92162)

227.9Thesameresult(withinengineeringaccuracy)isgivenbythedataofthesecondtestInstituteofEarthquakeEngineering2014-12- ThesameresultsInstituteofEarthquakeEngineering2014-12- 工程抗院

D [(12)2(2)2]1/2R(t)

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21

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2014-12- 院DalianUniversityof工程抗震院DalianUniversityof

2014-12-01 院DalianUniversityof院DalianUniversityof

2014-12-01 院§院?InstituteofEarthquakeEngineering2014-12-InstituteofEarthquakeEngineering2014-12- DalianUniversityof工程抗院

輸(t)輸(t)ggAP0 1k(12)2(2P1

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在β<0.6，ξ＝0.7時(shí)，放倍數(shù)接近常量。儀器反應(yīng)入幅值成正比。這種儀器作為低頻加速度院

vg(t)vg02 t)2 g0D2v g0DalianUniversityofDalianUniversityof工程抗震InstituteofEarthquakeEngineering

2014-12-01 院這里只介紹簡(jiǎn)單的DalianUniversityofDalianUniversityof基礎(chǔ)產(chǎn)生的InstituteofEarthquakeInstituteofEarthquakeEngineering2014-12- 院m p(t)p0DalianUniversityDalianUniversityof

彈性

穩(wěn)態(tài)相對(duì)位v(t)p0DsintkfS(t)kv(t)p0DsintfD(t)cv(t)

p0Dcostk

2p0Dcost總反力幅

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p1(2)21(2)21(2)2支撐系統(tǒng)的傳導(dǎo)比 TRfmax(t)/1(2)2工程抗震InstituteofEarthquakeEngineering

2014-12-01 k2ck2代入基底的運(yùn)動(dòng)vg0k 2p0單自由度隔振體系(支座擾動(dòng)vg(t)vg0

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vt(t)

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傳導(dǎo)比TR

g(t)/ g1(21(2 工程抗震InstituteofEarthquakeEngineering

2014-12-01 院Dalian院DalianUniversityof當(dāng)頻率較高時(shí)，傳導(dǎo)比要較低頻時(shí)低很多，因此，使系高頻運(yùn)動(dòng)是有利的工程抗震InstituteofEarthquakeEngineering

2014-12-01 院隔振率 IE1 If

TRTRD1(2D[(12)2(2)2

Ifβ=

隔振體系只有在β>21/2時(shí)才有DalianUniversityof對(duì)于小阻尼情 DalianUniversityofIE22/2 22IE/1IE2 2/22m/k2W/kg / 21 21工程抗震InstituteofEarthquakeEngineering

2014-12-01 院院 21

隔振體系越柔越 DalianUniversityof工程抗震InstituteofEarthquakeDalianUniversityof

2014-12-01 例題3-例題3-院DalianUniversityofDeflectionssometimesdevelopinconcretebridgegirdersduetocreep,andifthebridgeconsistsofalongseriesofidenticalspans,thesedeformationswillcauseaharmonicexcitationinavehicletravelingoverthebridgeatconstantspeed.院DalianUniversityofInstituteofEarthquakeEngineering2014-12- is40percentofFigureE31showsahighlyidealizedmodelofthistypeofsystem,inwhichthevehicleweightis4000lb[1814kg]anditsspringstiffnessisdefinedbyatestwhichshowedthatadding100lb[45.36kg]causedadeflectionof0.08in[0.203cm].Thebridgeprofileisrepresentedbyasinecurvehavingawavelength(girderspan)of40ft[12.2m]anda(single)amplitudeof1.2in[3.05cm].FromthesedataitisdesiredtopredictthesteadystateverticalmotionsinthecarInstituteofEarthquakeEngineering2014-12- is40percentof工程抗院穩(wěn)態(tài)響vt(t)院穩(wěn)態(tài)響vt(t)vg12Dsint2DalianUniversityof

2014-12-01 院傳導(dǎo)隔振率TR80/500IE10.16f彈簧剛kW/4stDalianUniversityof工程抗震InstituteofEarthquakeDalianUniversityof

2014-12-01 院第2章曾用自由振動(dòng)衰減法計(jì)算結(jié)構(gòu)的阻取自然對(duì)

lnvn/

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2

阻尼耗

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)dtm2與22 成正工