floor response spectra for ultimate and serviceability ...db.nzsee.org.nz/2009/pres23.pdf · gns...
TRANSCRIPT
Floor Response Spectra for Ultimate and
Serviceability Limit States of Earthquakes
SR Uma (Presenting Author) John Zhao
Andrew King
GNS Science
Outline
• Acceleration demand on Non-structural components
• Under two limit states:
- Ultimate limit state (ULS)
- Serviceability limit state (SLS)
• Adequacy of NZ standard provisions
- in NZS 1170.5 / NZS 4219
Does the force design for ULS always take
care of forces in SLS conditions?
GNS Science
New Zealand - Gisborne Earthquake, Dec 2007
(M 6.6)
Failure of suspended
components
< 50% of Design earthquake
GNS Science
What demand is on NSC?
Period of component
F1
F2
F3
F4
PGA
PFA2
PFA1
PFA3
PFA4
PFA
Acceleration history Response spectra
G
GNS Science
Period of component
Sac/P
FA
Design approach
Floor Height
Coefficient
(FHC)
Component
Amplification Factor
(CAF)
PFA i / PGA
PFA1
PGA
PFA2
PFA3
PFA4
GNS Science
Parameters for design provisions
Floor Height Coefficients Component Amplification factor
0
0.2
0.4
0.6
0.8
1
0 1 2 3 4
Floor Height Coefficient
h/H
Low -rise
High-rise
(NZS)
0
0.2
0.4
0.6
0.8
1
0 1 2 3 4
Floor Height Coefficient
h/H
(IBC)
0
0.5
1
1.5
2
2.5
3
0 1 2 3
Component Period, Tp
Am
plifica
tio
n fa
cto
r,C
i(T
p)
0
0.5
1
1.5
2
2.5
3
0 1 2 3
Component Period, (Tp /TB)
Am
plifica
tio
n fa
cto
r,C
i(T
p)
(NEHRP)
0p p Hi i pC T C C C T
Basic design force (NZS)
GNS Science
NZS Provisions with International Standards
• Maximum limit on design coefficient
– NZS: 3.6 Wp
– IBC: 1.6 SDsIp Wp
• Performance factors or Reduction factor
– NZS: 0.45 to 0.85
– IBC: 0.08 to 1.0
GNS Science
RECORD
NAME
COMP. STATION NAME EARTHQUAKE NAME MW R (KM)
500 year return period (Ultimate Limit State)
ARC2 EW Arcelik 1999 Kocaeli, Turkey 7.3 14
DUZ2 270 Duzce 1999 Kocaeli, Turkey 7.3 15
ELC2 270 El Centro 1940 El Centro 7.0 7
LAU1 NS La Union 1985 Michoacan 8.1 121
LUC1 260 Lucern 1992 Landers 7.3 2
K0392 NS HKD085 2003-09-26 Japan 8.3 45
TAB2 NS Tabas 1978 Tabas, Iran 7.4 2
50 year return period (Serviceability Limit State)
A-IV1/2 90/360 Wildlife Liquef. Array 1987 Superstition Hills 6.2 18
B-BRA1/2 225/315 Brawley Airport 1987 Superstition Hills 5.8 17
B-LAD1/2 180/270 Bishop - LADWP 1986 Chalfant Valley 5.8 23
H-PTS1/2 225/315 Parachute Test Site 1979 Imperial Valley 6.5 12
Earthquake record components
• Deaggregation analyses
• Scaled to the design spectrum• Wellington, Shallow soil site
GNS Science
Building model
P-Delta
column• Plastic hinges
3 storey and 10 storey (with a roof) buildings, Ductility = 6
Two dimensional Models
SAP 2000
Nonlinear link elements (Takeda) at plastic hinges
Modal Periods: 3 storey building – 1.1s and 0.35s
10 storey building - 2.3s and 0.75s
1
3
2
R
GNS Science
3 storey 10 storey
Floor height coefficient, HiC
0
1
2
3
4
0.0 1.0 2.0 3.0 4.0 5.0
PFA/C(0)
Flo
or
leve
l
ULS
ULS-84
SLS
SLS-84
NZS
RC30
1
2
3
4
5
6
7
8
9
10
11
0.0 1.0 2.0 3.0 4.0 5.0
PFA/C(0)
Flo
or
leve
l
ULS
ULS-84
SLS
SLS-84
NZS
RC10
PFA (Analysis)
(i) Constant up the height
(ii) << Code provisions
Reasons
• High frequency components filtered
• De-amplification due to non-linear behaviour
• Code provisions – maximum responses
ULS : 0.4g
SLS : 0.2g
NZS NZS
GNS Science
Component amplification - ULS
3 Storey Building 10 Storey Building
0.0
1.0
2.0
3.0
4.0
5.0
6.0
0.0 0.5 1.0 1.5 2.0
Tp/TB1
Sac/C
(0)
1st
4th
7th
10th
NZS
NZS-inel
RC10
ULS
0.0
1.0
2.0
3.0
4.0
5.0
6.0
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Tp/TB1
Sac/C
(0)
1st
2nd
3rd
Roof
NZS
NZS-inel
RC3
ULS
Design envelopes for:
(1) Non- ductile components
(2) Ductile fixing and braced to the structure – “performance factor”, Cph is used
0.45 < Cph < 0.85
conservative conservative
NZS_NonDuctile
NZS_Ductile
NZS_NonDuctile
NZS_Ductile
GNS Science
Component amplification - SLS
(Lower
storeys)
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Tp/TB1
Sac/C
(0)
3rd
3rd-84th
Roof
Roof-84th
NZS
RC3
SLS
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Tp/TB1
Sac/C
(0)
1st
1st-84th
2nd
2nd-84th
NZS
RC3
SLS
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
0.0 0.5 1.0 1.5 2.0
Tp/TB1
Sac/C
(0)
1st
1st-84th
NZS-1st
RC10
SLS
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
0.0 0.5 1.0 1.5 2.0
Tp/TB1
Sac/C
(0)
7th
7th-84th
10th
10th-84th
NZS
RC10
SLS
• “Resonance effect” at modal periods
• Design envelopes with performance factors =1
(Upper
storeys)
3 storey 10 storey
NZSNZS
NZS
NZS
GNS Science
Acceleration demand for Low-rise building
Short period components Long period components
ULS
SLS
0P P Hi i PC T C C C T
NZ Standard
Overall coefficient
√√
? ?
√ ?- Conservative - Marginal/
Unconservative
1
2
3
4
0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0
Cp (Tp)
Flo
or
leve
l
Med 84th NZS
RC3
SM
ULS
1
2
3
4
0.0 5.0 10.0 15.0
Cp (Tp)
Flo
or
leve
l
Med 84th NZS
RC3
SM
SLS
1
2
3
4
0 5 10 15 20 25 30 35
Cp (Tp)
Flo
or
leve
l
Med 84th NZS
RC3
FM
ULS
1
2
3
4
0.0 5.0 10.0 15.0
Cp (Tp)
Flo
or
leve
l
Med 84th NZS
RC3
FM
SLS
NZS NZS
NZS
NZS
GNS Science
Long period components Short period components
ULS
SLS
0P P Hi i PC T C C C TOverall coefficient
?
√
NZ Standard√ ?- Conservative - Marginal/
Unconservative
Acceleration demand for High-rise building
1
2
3
4
5
6
7
8
9
10
11
0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0
Cp (Tp)
Flo
or
leve
l
Med 84th NZS
RC10
SM
ULS
1
2
3
4
5
6
7
8
9
10
11
0.0 5.0 10.0 15.0
Cp (Tp)
Flo
or
leve
l
Med 84th NZS
RC10
SM
SLS
√
√
1
2
3
4
5
6
7
8
9
10
11
0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0
Cp (Tp)
Flo
or
leve
l
Med 84th NZS
RC10
FM
ULS
1
2
3
4
5
6
7
8
9
10
11
0.0 5.0 10.0 15.0
Cp (Tp)
Flo
or
leve
l
Med 84th NZS
RC10
FM
SLS
NZSNZS
NZS
NZS
GNS Science
Low cycle fatigue at high frequency?
Response of a component with a natural period of 0.36s
-15
-10
-5
0
5
10
15
0 5 10 15 20 25 30Time (s)
Tota
l accele
ration (
m/s
2)
Component damp ratio 5%
Response of a component with a natural period of 0.36s
-25
-20
-15
-10
-5
0
5
10
15
20
25
0 5 10 15 20 25 30
Time (s)
Tota
l accele
ration (
m/s
2) Component damp ratio 2%
5 % damping 2 % damping
(Serviceability limit state earthquake at 2nd floor of 3 storey building)
Damage accumulation due to low cycle fatigue?
Reduced damping ratio at SLS
Design acceleration Design accelerationNZS
NZS
NZS
NZS
GNS Science
Practical implications on components at SLS
Rigid mounted (Tp < 0.06s) Braced to the structure Vibration isolated
• Non ductile
• Overly conservative design
in ULS
• “ductile” performance
expected
• lesser damping at SLS
• Low cycle fatigue
• knowledge on (Tp/TB)
appears to be essential
to avoid “Resonance
effect” at least for low-
rise buildings with
TB < 0.75
GNS Science
NZS design provisions
Component Period, Tp LS Low-rise High-rise
ShortULS
SLS
LongULS
SLS
√
?
?
√√
?
?- Conservative - Unconservative
√ √
√
GNS Science
Conclusions
• Constant Peak Floor Acceleration up the height except the roof
– Quite different from the current provisions
– Is current provisions overly conservative for very rigid components, i.e.
Tp closer to zero
• “Resonance effect” more pronounced in SLS
– not represented in NZ design standards
• Spectral amplification exceeds the design envelope
– At building periods
– More in SLS earthquakes
• Adequacy of design standards for overall Cp (Tp)
– Likely to exceed the standard’s provisions in SLS conditions
– Adequate in ULS conditions
GNS Science
Does the force design for ULS always take
care of forces in SLS conditions?
Not Always…
GNS Science
Thank you!
GNS Science
Earthquake loss
• Losses due to
– Structural Damage
– Non-structural components/ contents Damage
• Study of NSC – important component of PBEE
Typical investments in building construction (after E. Miranda)
GNS Science
Response of flexible components in tall
buildings
• Flexible components – such as spring mounted
components – or very flexible and lightly
damped components – vibration associated with
the resonance of these flexible systems with the
harmonic vibration of buildings, particularly tall
buildings, can be catastrophic and special
design is required – NZS 1170.5 commentary