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AAABBB1 質点線形系 振動解析
Numerical Analysis Method for a Mass with Linear-System in 1-D
x y
c k
m
m x
y k
c
Linear Vibration System
spring-dashpot-mass system spring mass
dashpot
structure system
-1質点系 振動 数学的厳密解(Mathematical Exact Solution)
- 応答 数値解法(Numerical Solutions) : 直接積分法(Direct Integration Method)
- 地震応答ス ク ル Earthquake Response Spectrum
運動方程式:
t c x t kx t f t m y t
x
m
(1.1)貫性力:相対加速度 + 減衰制振力:相対速度 + 復元力:相対変 外力 Inertia force viscous force recover force
釣合い式:
0
m x t y t c x t kx t
(1.2)貫性力:絶対加速度 + 減衰制振力:相対速度 + 復元力:相対変 0
m
: mass [kg]k
: spring coefficient [kg/sec2]c
: viscous damping coefficient [kg/sec] t
f
: external force applied to the mass t
y
:f t
is replaced with acceleration of the ceiling and the ground m y t
according to D'Alembert’s law. t
x
,x t
,x t
: relative acceleration[m/sec2], velocity[m/sec], and displacement[m] with respect to the ceiling or the ground, respectively t y t
x
: absolute displacement t
x
m
: inertia forceG G G
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AAABBB1. Mathematical Exact Solutions: Analytical results
1.1. 自由振動
F ree Vibration:
t 0
f
,y t 0
(1.3)Linear and homogeneous differential equation solution = general solution
t x t
x
g (1.4)Characteristic Equation using differential operator
0
2
22
g o g
g
Dx x
x
D
(1.5)D
: differential operator with respect to time differential (D d dt
):x
g Dx
g and x
g D
2x
g.m
c
2
,m
k
o2
(1.6)
: viscosity normalized by mass[1/sec]
o: referential angular frequency[1/sec] / natural circle frequencym
k
T f
o o
o
2
2
1
(1.7)T
o: referential vibration period[sec] / natural periodf
o: referential vibration frequency[1/sec] / natural frequency
o
gg
x
Dx
2
2 (1.8)Vibration mode of the system clearly depends on the relative magnitude of viscous damping:
mk
c
mk
c
mk
c
o o o
2
0
2
0
2
0
2 2 2 2 2 2
vibr ation
damped
over
vibr ation
damped
cr itically
vibr ation
damped
nor mally
:
c
cr 2 mk
(1.9)G G G
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AAABBB a) Normally damped vibrationparameters
mk
c
c
cr 2
, (2.10) i
D
, (2.11)2 2
2
o
, (2.12)period
2
2
1
1
1
2
2
h
T
h
T
oO
(2.13)motions
t
A
B
t
B
A
e
t
x
t
A
B
t
B
A
e
t
x
t
B
t
A
e
t
x
g g
g g
t g
g g g
g t g
g g
t g
sin
2
cos
2
sin
cos
sin
cos
2 2 2
2
(2.14)initial conditions
g g g
g g
B
A
x
A
x
0
0
(2.15)therefore,
0
0
0
g g
g
g g
x
x
B
x
A
(2.16)complex descriptions
t
i
i
C
al
t
x
t
i
i
C
al
t
x
t
i
C
al
t
x
g g
g g
g g
exp
Re
exp
Re
exp
Re
2
(2.17)damping
Viscous damping coefficient
c
mk
c
cr 2
(2.18)Viscosity normalized by mass
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AAABBBm
c
2
, (2.19)Logarithmic damping factor
1
ln
n n
a
D a
(2.20)Damping factor
o
cr
mk
c
c
h c
2
(2.21)
21
1
ln 2
ln
h
T h
T
t
x
t
x
a
D a
n n
(2.22)0 1 2 3 4 5
-2
-1
0
1
2
t(s)
x( t)
h=0
h=0.005
h=0.01
h=0.05
h=0.1
自由減衰振動
0 1 2 3 4 5
-2 -1 0 1 2
t(s)
x(t)
x
11
'
x
x
2x
3x
42
'
x x
3'
4
'
x
'
T
t
1t
2G G G
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AAABBB 固有周期実測値(observed value of fundamental natural period)structure 中 層 H≧45m 高層 H 45m
S
T
1=0.061 N[階]T
1=0.079 N[階]SRC, RC
T
1=0.054 N[階]T
1=0.053 N[階]減衰定数実測値(observed value of damping factor) 鉄骨構造(Steel structure):
h
=2%鉄骨鉄筋コン 構造(Steel reinforced concrete structure):
h
=3% 鉄筋コン 構造(Reinforced concrete structure):h
=5% 土:h
=0~25%Here, if h<< 1, we can obtain,
1
h
,D 2 h
(2.23)Consequently, we can estimate value of h by measuring D,
1
h
,
2
h D
(2.24)G G G
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AAABBB b) Critical damped vibrationparameters
mk
c
c
cr 2
, (2.25)
D
, (2.26)2
0
2
2
o , (2.27)period
T 2
(2.28)motions
t
B
B
A
e
t
x
t
B
B
A
e
t
x
t
B
A
e
t
x
g g
g t g
g g
g t g
g g t g
3 2
2
2
2
(2.29)initial conditions
g g g
g g
B
A
x
A
x
0
0
(2.30)therefore,
0
0
0
g g
g
g g
x
x
B
x
A
(2.31)c) Over damped vibration
parameters
mk
c
c
cr 2
, (2.32)
D
, (2.33)
2 2
2
o
, (2.34)period
1
1
1
2
2
2
2
h
T
h
T
o
O
(2.35)G G G
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AAABBBmotions
t
A
B
t
B
A
e
t
x
t
A
B
t
B
A
e
t
x
t
B
t
A
e
t
x
g g
g g
t g
g g g
g t g
g g
t g
sinh
2
cosh
2
sinh
cosh
sinh
cosh
2 2 2
2
(2.36)
initial conditions
g g g
g g
B
A
x
A
x
0
0
(2.37)therefore,
0
0
0
g g
g
g g
x
x
B
x
A
(2.38)-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 3
0 2 4 6 8 10
過減衰
減衰振動
臨界減衰
An example for vibration behaviours with different h : normally damped, critical damped and over damped vibrations
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AAABBB* Euler’s formula
e
ixe
ix
x
2
cos 1
,x e
ix e
ix
2
sin 1
x i x nx i nx
e
inx cos sin
n cos sin
* mechanical vibration system and electric circuit system
m x
k
c
spring
dashpot
spring-dashpot-mass system
electric circuit system
C
R L
f
m v cv k vdt
f
x
v
Idt
RI C
I
L
e 1
q e
I
* mechanical vibration system and a control system in control engineering: PID control
K e dt
e T
dt K
K de
T
S
pI p p
D c
1
Derivation control + Proportion control + Integration control PID
S
c: control signale
: error = target value – current valueG G G
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AAABBB 非線形解法 (Non-linear analysis of vibration by numerical method)直接積分法(Direct Integration Method) 非線形運動方程式 数値積分 方法
差分法- 時間領域 数値積分
- Newmark β法: 実用的に最も用いら
t t x t t x t t x t t x t t
x
2 22
1
(2.39) t t x t t x t t x t t
x 1
(2.40)Newmark β法 特別 呼 名
手法
線形加速度法(Linear Acceleration Method) 0.5 1/6 中点加速度法(Constant Average Acceleration Method) 0.5 1/4
- Wilson θ法
t t x t t x t t x t t x t t x t
x
6
2
1
2 2(2.41)
t t x t t x t t x t t x t
x
2
(2.42)各種数値積分法 安定条件(stability condition of numerical integration)
手法 数値積分 安定条件 無条件安定条件
(unconditionally Stable)
Newmark β法
1 4
2
o
t
0.5 1 4
Wilson θ法
1 . 37
中央差分法
2
t
し
o モ ル 最も大きい 振動数G G G
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AAABBB- 直接積分法
) 運動方程式 離散化
t h x t x t y t
x
2
2
(2.43)
t t t
t t
t t
t t t
t t
t t
y
B
y
B
x
A
x
A
x
y
B
y
B
x
A
x
A
x
22 21
22 21
12 11
12
11 (2.44)
22 21
12 11
A
A
A
A A
,
22 21
12 11
B
B
B
B B
(2.45)
t t
t t
t t
t t t
y
B y
x
A x
x
x
(2.46)t t t t t
t t
t
h x x y
x
2
2 (2.47)t t t
t
h x x y
x
2
2
(2.48)t t t t t
t t
t
h x x y
x
2
2 (2.49)Taylor Expansion
2
2 2
x t
t
x
x
x
tt
t
t
t
(2.50)t
x
x
x
tt
t
t1
(2.51)Taylor Expansion
t t f t t f t
1f
t t
2 t t
(2.52)
2
2 2
t t
f
t
f
t
t
f
t
t
f
t t
2 t t
(2.53)) 代数方程式を計算
(1) Newmark β法 挿方式
t t tt
x x
x
21
, x
t1 1 2 x
t 2 x
tt (2.54)
1 2 x 2 x 2 t
2t
x
x
x
tt
t
t
t
tt
(2.55) x x t
x
x
tt
t 1
t
tt
(2.56) A ?
B ?
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AAABBB(2) Wilson θ法 外挿方式
時間
t
~t t
成立 運動方程式 時間t t
( 1
) も成立t t t t t
t t
t
h x x y
x
2
2 , 1
(2.57)
t t t
t t
t t t t
t
y
y
y
x
x
x
1
1
(2.58)
t
x
x
x
x
x t
x
t
x
x
x
t t t
t t
t t t
t t t
2
1 2
2
3
1 3
2
(2.59)
In the case of
=1,
t
x
x
x
x
x t
x
t
x
x
x
t t t
t t
t t t
t t t
2
1
2
1
2
3
1
3
2
2(2.60)
= Linear Acceleration Method (
=0.5,
=1/6)G G G
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AAABBB - 地震応答ス ク ル Earthquake Response Spectrum相対 変 応答ス (Displacement Response Spectrum):
x
相対 速度応答ス (Velocity Response Spectrum) :
x
絶対 加速度応答ス (Acceleration Response Spectrum) :
x y
h T
S
d,
: 最大相対変 応答値(Displacement Response Spectrum) h T
S
v,
: 最大相対速度応答値(Velocity Response Spectrum) h T
S
a,
: 最大絶対加速度応答値(Acceleration Response Spectrum)Plots of maximum response values again selected parameters of the system or of forcing function (earthquake considered) are called ‘response spectra’.
For one-degree system, the natural period (or frequency) is the characteristic that determined its response to a given forcing function
⇒ ratio of maximum dynamic stress in a structure to the corresponding static stress
Calculation results of response for each of systems
one-degree systems with different natural periods (frequency)
input force (earthquake)
Maximum response values of systems
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AAABBBv v
d
S
S T
S 2
1
≒
: 最大相対変 応答値(Displacement Response Spectrum)v
v
S
S
: 最大相対速度応答値(Velocity Response Spectrum)v v
a
S
S T
S ≒ 2
: 最大絶対加速度応答値(Acceleration Response Spectrum)(2.61)
Sa vs period
Sv vs period
SD vs period
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AAABBB- 3重応答ス ク ル Tripartite response spectrum
T
S
S
T
S
S
d v
a v
log
2
log
log
log
log
2
log
log
log
(2.62)
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AAABBB- 応答ス ク ル response spectrum について
フ エ ス 地震波そ も 周波数特性 応答ス 構造物 1 質点
減衰系 含 地震動 全体像
モ 解析 modal analysis
加速度応答ス ク ル:地震力 ス シア係数(base shear coefficient) 動的震度 地震力
maxmax
m x y
Q
(2.63)ス シア係数(base shear coefficient)、動的震度
g
T
h
S
g
y
x
W
C Q
max
max
a,
(2.64)静的震度: 静的耐震設計
k
hW
k
Q
max
h
(2.65)速度応答ス ク ル:地震動 構造物 与え 最大 エネ
最大 みエネ (strain energy):
max 22
1 k x
(2.66)単 質量あ 最大エネ :
2 2 max 2
max
2
1
2
1
2
1
S
vx
m x
k
(2.67)(maximum energy per unit mass)
ス 強度(Spectral intensity):
I
h
2.5S
vh T dT
1 .
0
( , )
(2.68)変位応答ス ク ル: み 大 さ~応力 大 さ 最大 断力:
max
max
k x
Q
(2.69) x y
maxkx
maxm
(2.70)G G G
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AAABBB ---[Recommended text]
William Weaver, Jr., Stephen P. Timoshenko, Donovan H. Young; Vibration problems in engineering, 5th edition(?), Wiley Interscience.