earthquake engineering
DESCRIPTION
Earthquake Engineering. “8.9 Quake Strikes Japan—Nation’s worst in 140 years”. Airport, Sendai, Japan. Fukushima- Daichi nuclear power plant. Earthquakes Past and Present. Sendai, Japan (8.9 magnitude). historical Seismicity Map. http://earthquake.usgs.gov/eqcenter/recenteqsww/. - PowerPoint PPT PresentationTRANSCRIPT
Earthquake Engineering
“8.9 Quake Strikes Japan—Nation’s worst in 140 years”
Fukushima-Daichi nuclear power plant
Airport, Sendai, Japan
Earthquakes Past and PresentSENDAI, JAPAN (8.9 MAGNITUDE) HISTORICAL SEISMICITY
MAP
http://earthquake.usgs.gov/eqcenter/recenteqsww/ http://earthquake.usgs.gov/earthquakes/world/seismicity_maps/world.pdf
A pan-global issue….
http://www.mapsofworld.com/world-major-earthquake.htm
Some Major Earthquakes, Past and Present
•Christchurch, NZ 2011
•Talca, Chile 2010
•Port-au-Prince, Haiti, 2010
•Guandong, China, 2008
•Fukuoka, Japan, 2005
•Izmit, Turkey, 1999
•Northridge, CA, 1994
•Mexico City, 1985
Why bother?
Sendai Japan Earthquake 2011Amazing engineering: Buildings Sway Without Collapsing
Different BuildingsDifferent model parameters
The Fundamental QuestionsCan we predict how different
buildings will respond to an earthquake?
How can we use this information to engineer a safe structure
Tabas, Iran 1978 Earthquake
0 5 10 15 20 25 30 35-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
Time (s)
Acc
el. (
units
of g
)
Tabas 1978 Ground Acceleration (Fault Normal)
Acceleration record is messy. No way to integrate Duhamel’s integral. No worries, computers to the rescue!
Relative motion of building and ground
Impulse Response FunctionMeasured Acceleration/USGS data
0 5 10 15 20 25 30 35-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
Time (s)
z(t)
Tabas 1978: Relative Displacement: o = 1
0 5 10 15 20 25 30 35-0.01
-0.005
0
0.005
0.01
0.015
Time (s)
z(t)
Tabas 1978: Relative Displacement: o = 10
0 5 10 15 20 25 30 35-0.06
-0.04
-0.02
0
0.02
0.04
0.06
Tabas 1978: Relative Displacement: o = 3
Time (s)
z(t)
0 5 10 15 20 25 30 35-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
Time (s)
Acc
el. (
units
of g
)
Tabas 1978 Ground Acceleration (Fault Normal)
z = 0.05 is assumed
marks |z|max
If we found |z|max for a continuous range of o, we’d get the Spectral Displacement(Displacement Spectrum)
Gro
und
acce
lera
tion
(uni
ts o
f g)
Z(t)
met
ers
Z(t)
met
ers
Z(t)
met
ers
Spectra For El Centro Ground MotionAveraged SpectraTo Many (88) Earthquakes
Figure Credits: L A Chopra, Dynamics of Structures, Chap 6Right: G. Housner “Strong Ground Motion” in Earthquake Engineering, R Wiegel, editor.
Natural Period (sec)
Displacement
Acceleration
Velocity
Tripartite Representation
SD = spectral displacementSV = spectral velocitySA = spectral acceleration
SA /o = SV = oSD
Housner Spectrum
Spectrum for one earthquake Spectrum averaged over 88 earthquakes
Housner spectrum for z = 0.05
Seattle Monorail Seattle, WA is a beautiful
city, but is prone to large earthquakes. The monorail on the bridge has previously been measured to have a natural period of 2 s. Damping is assumed to be 2%. During an earthquake, is the trolley likely to derail? Use the Housner spectrum to find out!
Picture from: http://bcostin.wordpress.com/2008/02/25/seattle-worlds-fair-1962-postcards/seattle-monorail/
Beach House You are hired as an
architectural engineer to build a California dream house on a hillside. The structure can be idealized as shown (on chalkboard). The frame is built out of concrete (E = 30x109 Pa). The support columns have a cross section of 10 inches squared. Assume damping is 5%. Determine the base shear in each column, which is more likely to fail?
What we need to guard againstBUCKLING SMASHING/POUNDING
Base Isolation Configuration
Figure credit: Michael D. Symans, PhD Rensselaer Polytechnic Institute: http://www.nibs.org/client/assets/files/bssc/Topic15-7-SeismicIsolation.pdf
Reduced Shearing in Superstructure.CONVENTIONAL BUILDING
BASE-ISOLATED BUILDING
Figure credit: Michael D. Symans, PhD Rensselaer Polytechnic Institute: http://www.nibs.org/client/assets/files/bssc/Topic15-7-SeismicIsolation.pdf
Lead-Rubber Bearing
Figure credit:s Michael D. Symans, Rensselaer Polytechnic Institute: http://c.ymcdn.com/sites/www.nibs.org/resource/resmgr/BSSC/Topic15-7-SeismicIsolation.pdf
Shear Modulus
E ~ 0.5 – 1.0 MPa
LRB decreases keff and o
Reduces shearing in columns…………but increases displacement
LRB Isolation in Action
Rubber Base Isolators
Lead Rubber Bearing (LRB) in Action
UCSD testing facility LBRs in Japan
How do we model what we just saw?
Displacement , u
Frictional Pendulum System
Image credit: http://www.asee.org/documents/sections/pacific-southwest/2008/Porbaha_Ali_et_al%20Base%20isolation.pdf
Concept of Frictional Pendulum
Image credits: http://www.asee.org/documents/sections/pacific-southwest/2008/Porbaha_Ali_et_al%20Base%20isolation.pdfhttp://nees.buffalo.edu/docs/dec304/FP-DC%20Report-DEMO.pdf; laconservancy.org
Frictional Pendulum
Pendulum Period:T
Restoring/Recentering Force Frictional Force
The quantitative model
Restoring/Recentering Force Frictional Force
Force vs. Displacement Hysteresis Loop