Practical Examples employing the International Building...

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

22

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