practical examples employing the international building...
TRANSCRIPT
Carlo Lai
Francesca Bozzoni Mirko CoriglianoElisa ZuccoloLaura Scandella
Practical Examples employing thePractical Examples employing theInternational Building Code (IBC) regulations andInternational Building Code (IBC) regulations and
the New Seismic Hazard Maps for the Eastern Caribbean the New Seismic Hazard Maps for the Eastern Caribbean
Walter Salazar
Richard RobertsonLloyd LynchJoan Latchman
June 2011
www.uwiseismic.comwww.uwiseismic.com
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Practical Examples• Get the design response spectra and the
seismic coefficients Cs for the following sites at rock conditions:
1) Scarborough -Tobago (Building – 20 stories)
2) Indian River – Dominica (Bridge – 30 m multi-span intermediate columns with height H = 15 m)
33
Design spectral acceleration parameters IBC – ASCE 7_05
• SDS = 2/3*Fa * Ss
• SD1 = 2/3*Fv * S1
Fa and Fv: depends on soil conditionsFor rock site conditions – CLASS B It Corresponds to a shear wave velocity Vs = 760 m/s:
Fa = 1.0 and Fv = 1.0
Spectral acceleration for 1.0 s
Obtained in the Seismic
Hazard maps
Spectral acceleration for 0.2 s
44
To
Ts
SDS
SD1
1DaSST
=
ELASTIC DESIGN RESPONSE SPECTRUM
COMPATILE WITH THE IBC
EXAMPLE 1: Scarborough -Tobago
Building – 20 stories
55
66
1.85 g
77
0.375 g
88
• Reading from the maps
0.4 0.6 1.23* 0.4 0.6 0.492 18.450.04a DS
o
T TS S TT
= + = + = +
1 0.250.2 0.2* 0.041.23
Do
DS
ST sS
= = =
T : the fundamental period of the structure in “s”
1
1.850.375
SS gS g
=
= 1
(2 / 3)*1.85 1.23(2 / 3)*0.375 0.25
DS
D
S g gS g g
= == =
99
1 0.25 0.201.23
DS
DS
ST sS
= = =
1 0.25DaS gST T
= =
1.23a DSS S g= = Flat spectral response
Period to which begin the exponential decay
Spectral exponential decay
1010
The Seismic Coefficient Cs
Fundamental Period:
T = 2.0 s (after dynamic analysis)
SA = 0.13g (elastic spectral acceleration)
Reduction factor R= 8.0 considering ductility and
overstrength
Seismic design coefficient:
Cs = SA/R=0.13g/8=0.016g
1 0.25DaS gST T
= =
1.23a DSS S g= =
0.20s
0.04s
0.492 18.45aS T= +
0.13 g
1111
SAP MODEL FOR THE 20 STORY BUILDING
EXAMPLE 2: MULTI SPAN BRIDGE
INDIAN RIVER - DOMINICA
1212
1313
MULTI SPAN BRIDGEINDIAN RIVER - DOMINICA
1414
Indian River Indian River1.55g 0.47g
1515
• Reading from the maps
0.4 0.6 1.03* 0.4 0.6 0.41 10.30.06a DS
o
T TS S TT
= + = + = +
1 0.310.2 0.2* 0.061.03
Do
DS
ST sS
= = =
T : the fundamental period of the structure in “s”
1
1.550.47
SS gS g
=
= 1
(2 / 3)*1.55 1.03(2 / 3)*0.47 0.31
DS
D
S g gS g g
= == =
1616
1 0.31 0.301.03
DS
DS
ST sS
= = =
1 0.31DaS gST T
= =
1.03a DSS S g= = Flat spectral response
Period to which begin the exponential decay
Spectral exponential decay
1717
Cs = SA/R =0.42g/8=0.053g
The Seismic Coefficient Cs
Design of a column
Fundamental Period (after dynamic analysis):
T = 0.75 s (H=15 m and 30 m span)
SA = 0.42g (elastic spectral acceleration))
Reduction factor R= 8.0
Considering ductility and overstrength
1 0.31DaS gST T
= =
1.03a DSS S g= =
0.30s
0.06s
0.41 10.3aS T= +
0.42 g