Seminar in Minho University, Guimarães, Portugal
Hybrid Simulations: Theory and
Applications in Earthquake Engineering
Khalid M. Mosalam, Professor
Director of nees@berkeley
Structural Engineering, Mechanics, and Materials
Department of Civil and Environmental Engineering
University of California, Berkeley
1
Acknowledgements
Dr. Selim Günay, UCB
Dr. Shakhzod Takhirov, UCB
Mr. Mohamed Moustafa, UCB
Mr. Ahmed Bakhaty, UCB
Mr. Eric Fujisaki, PG&E
Sponsors:
• California Institute for Energy and Environment (CIEE)
• US-DoE
• PG&E
• National Science Foundation (NSF) [PEER; NEES]
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
2
Introduction
10th
15 sites
http://nees.org
http://nees.berkeley.edu
All our presentation from Oct. 1-4, 2012 will be made available in this site
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
3
http://nees.berkeley.edu
Introduction
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
4
Introduction
Seattle, WA
Portland, Oregon
Stanford, CA
Kassel, Germany
Ankara, Turkey
Buffalo, NY
Groznii, Russia
Kyoto, Japan
Davis, CA
Taipei, Taiwan
UCB, CA
nees@berkeley
PEER & CEE
Bolder, CO
Guimarães,
Portugal
Port au Prince, Haiti
Santiago, Chile
Atlanta, Georgia
Casablanca, Morocco
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
5
Mini-Symposium on Hybrid Simulation:
Theory and Applications [Tomorrow]
1. Hybrid simulation fundamentals [3.0 hours]
1. Substructuring
2. Integration methods
3. Simulation errors
2. Hybrid simulation applications [2.5 hours]
1.
2.
3.
4.
Introduction to OpenSees
Introduction to OpenFresco
Application I: Hybrid simulation of structural insulated panels
Application II: Real-time hybrid simulation of high voltage electric disconnect
switches
3. Seismic testing of lifelines related to the electric grid [1.5 hours]
1. Shaking table and static tests and finite element simulations of high voltage
electric disconnect switches
2. Fragility tests of concrete duct-banks for high voltage distribution lines
4. Use of advanced monitoring (e.g. Laser scanning in Haiti) and
measurement systems in structural testing [1.0 hour]
We would like your feedback via the electronic form set especially for this workshop on the link below:
https://peercenter.wufoo.com/forms/hybrid-simulation-workshop-evaluation-portugal/
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
6
Short Course on Probabilistic Performance-based
Earthquake Engineering (PBEE) [Oct. 3-4]
Pacific Earthquake
Engineering Research
(PEER) Center Mission




Courtesy of Prof.
S. Mahin

Advance and apply PBEE tools to
meet the needs of various
stakeholders
Problem-focused, multidisciplinary research built upon
foundation of engineering and
scientific fundamentals
Close partnerships with
government, industry and
engineering professionals
Strong national and global
research collaborations
Commitment to education at all
levels
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
7
Short Course on Probabilistic Performance-based
Earthquake Engineering (PBEE) [Oct. 3-4]
1. PBEE assessment methods [2.0 hours]
1.
2.
Conditional probability approaches such as PEER and SAC/FEMA formulations
Unconditional probabilistic approach
1.
2.
Optimization-based methods
Non-optimization-based methods
1.
2.
3.
4.
5.
Hazard analysis
Structural analysis
Damage analysis
Loss analysis
Combination of analyses
2. PBEE design methods [2.0 hours]
3. PEER PBEE formulation [4.0 hours]
4. Application 1: Evaluation of the effect of unreinforced masonry infill wall on
reinforced concrete frames with probabilistic PBEE [1.0 hour]
5. Application 2: Evaluation of the seismic response of structural insulated panels with
probabilistic PBEE [1.0 hours]
6. Application 3: PEER PBEE assessment of a shear-wall building located on the
University of California, Berkeley campus [1.0 hours]
7. Future extension to multi-objective performance-based sustainable design [0.5 hour]
8. Recapitulation [0.5 hour]
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
8
Seminar in Minho University, Guimarães, Portugal
Hybrid Simulations: Theory and
Applications in Earthquake Engineering
Khalid M. Mosalam, Professor
Director of nees@berkeley
Structural Engineering, Mechanics, and Materials
Department of Civil and Environmental Engineering
University of California, Berkeley
9
Outline
1. Motivation
2. Theory
a)
b)
c)
d)
e)
f)
Background
Substructuring
Integration Methods
Simulation Errors
Geographically Distributed HS
Real-time HS
3. Application I: HS of Structural Insulated Panels (SIPs)
4. Application II: RTHS of Electrical Insulator Posts on a
Smart Shaking Table
5. Future Directions
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
10
Acceleration [g]
Motivation
6
6
4
4
2
2
0
0
-2
-2
-4
Acceleration [g]
-4
Top of support structure: Real-time HS
-6
6
4
4
2
2
0
0
-2
-2
Top of support structure:
Conventional shaking table
-6
0
10
20
30
Time [sec]
40
Top of insulator: Real-time HS
-6
6
-4
$
$$$
-4
Top of insulator: Conventional shaking table
-6
50
0
10
20
30
Time [sec]
40
50
We will see this again today and in tomorrow’s HS workshop!
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
11
Motivation
Qualitative justification of Hybrid Simulation with an
Optimization Technique
Accuracy
Shaking table
HS
Static
Test cost
Hypothetical
Pareto-front
We will discuss this further during the PBEE course on 3-4 October!
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
12
Theory: Background


Physical models of structural resistance
Computer models of structural damping and inertia
m a + c v + k d = -m ag
m a + c v + R = -m ag
m a + m ag + c v = -R
c
f(t)
cv
kd
ma
m
m: mass
k: spring constant
c: damping coefficient
k
d
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
f(t)=-mag
13
Theory: Background
m1
m2
m3
Need to assemble:
a) Restoring forces (Geometric stiffness may be considered, R  R  K G d )
b) Damping forces from physical dampers
c) Inertia forces from the mass of the physical specimens
Desired
d(t) +
-
Error in
current
position
Physical
model,
e.g. 3dof
Force
value
Dynamics of
the system
Current
position
d(t)
Feedback
dynamics
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
14
Theory: Background




By definition, a hybrid model is sub-structured
Multiple sub-structures can be used
Many analytical sub-structures (Soft models)
Many physical sub-structures (Hard model)
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
15
Theory: Background

Testing infrastructure must enable:
1. Simulation of individual sub-structures
2. Integration of equations of motion
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
16
Theory: Background

Advantages:
1. Physical model resistance of sub-structures whose computer
models are not good enough.
2. Model the inertia forces (and damping, and second-order
effects) in the computer.

Disadvantages:
1. Substructures are connected and interact at their boundaries.
2. Specimens have inertia and damping, too.
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
17
Theory: Background
m pp
m
 cp
m pc  a p  c pp
  

mcc   ac   ccp
c pc  v p   R p 
m pp
      

ccc   vc   Rc 
 mcp
m pc  a pg 
 
mcc   acg 
Subscript c  computed sub-structure
Subscript p  physical sub-structure

Restoring forces can be assembled

Also the following can be assembled:
1.
Damping forces from physical dampers
2.
Inertia forces from the mass of the physical specimens
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
18
Theory: Background

Damping and inertia:
1.
Explicit consideration of physical dampers and physical masses, based on measured
velocities and accelerations.
2.
DOF condensation must be performed carefully.
3.
Coordinate transformations must be propagated to velocities and accelerations.

Second-order effects:
Geometric stiffness may be assembled into the resistance:
R  R  KG d
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
19
Theory: Background
Interface between Sub-Structures
 Equilibrium and compatibility must be satisfied
 Deformations and forces
1. Displacement (relatively easy)
2. Rotation (very difficult)
 Opportunity to do:
DOF condensation
 Coordinate transformations
Physical to computational DOF’s: dp=Tdc
 Geometry corrections
Actuator movements
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
20
Theory: Background
Distributed Hybrid Simulation
T. Yang, B. Stojadinovic, & J. Moehle
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
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Theory: Background
Pan, P., Tomofuji, H., Wang, T., Nakashima, M., Ohsaki, M., & Mosalam, K.M., “Development of
Peer-to-Peer (P2P) Internet Online Hybrid Test System,” EESD, 35: 867-890, 2006.
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
22
Theory: Background
Computed or
measured
reactions
Pan, P., Tomofuji, H., Wang, T., Nakashima, M., Ohsaki, M., & Mosalam, K.M., “Development of
Peer-to-Peer (P2P) Internet Online Hybrid Test System,” EESD, 35: 867-890, 2006.
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
23
Theory: Background
Pan, P., Tomofuji, H., Wang, T., Nakashima, M.,
Ohsaki, M., & Mosalam, K.M., “Development of
Peer-to-Peer (P2P) Internet Online Hybrid Test
System,” EESD, 35: 867-890, 2006.
Proxy Server: a computer system acts as an intermediary for
requests from clients seeking resources from other servers.
TCP/IP: Transmission Control Protocol and Internet Protocol,
networking communications protocols for the Internet.
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
24
Theory: Substructuring
m2
u2
Analytical
substructure
(-)
m1
u1
Experimental
substructure
Computed Measured
 m1
0

0   u1   c11




m 2  u 2  c 21
c12   u 1   f a  f e 
 m1 

    u g




c 22  u 2   f a 
m 2 
 Nature of the problem requires substructuring
 Presence of experimental substructures requires the use of special integration methods
 Presence of a transfer system introduces simulation errors
 Rate dependent materials require real-time hybrid simulation (RTHS)
 Making use of multiple labs extends the method to geographically distributed testing
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
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Theory: Substructuring
 Dermitzakis and Mahin (1985)
 Nakashima, Kaminosono, Ishida, and Ando (1990)
 Schneider and Roeder (1994)
 Nakashima and Masaoka (1999)
 Mosqueda, Cortes-Delgado, Wang, and Nakashima (2010)
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
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Theory: Substructuring
CASE 1: CANTILEVER COLUMN with MASS [No MASS
MOMENT of INERTIA or ANALYTICAL SUBSTRUCTURE]
m1
u1
m1
u1
Red : Experimental
Blue: Analytical
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
27
Theory: Substructuring
CASE 2: CANTILEVER COLUMN with MASS and MASS
MOMENT of INERTIA [No ANALYTICAL SUBSTRUCTURE]
u2
u2
u1
m1, Im1
u1
m1, Im1
Red : Experimental
Blue: Analytical
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
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Theory: Substructuring
CASE 3: TWO COLUMNS without
ANALYTICAL SUBSTRUCTURE
m2
u2
m2
u2
m1
u1
m1
u1
Red : Experimental
Blue: Analytical
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
29
Theory: Substructuring
CASE 4: TWO COLUMNS with an EXPERIMENTAL
and an ANALYTICAL SUBSTRUCTURE
u4
m2
u2
u4
m2
u2
u3
u3
m1
u1
m1
u1
Red : Experimental
Blue: Analytical
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
30
Theory: Substructuring
CASE 4-1: TWO COLUMNS with an EXPERIMENTAL
and an ANALYTICAL SUBSTRUCTURE
m2
u2
u3
u3
m1
m2
u2 - u 1
u1
m1
Red : Experimental
Blue: Analytical
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
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Theory: Substructuring
CASE 4-2: TWO COLUMNS with an EXPERIMENTAL
and an ANALYTICAL SUBSTRUCTURE
m2
Spring with a lateral
force-deformation
relationship
m1
u2
u1
m2
u2 - u 1
m1
Spring with a lateral
force-deformation
relationship
Red : Experimental
Blue: Analytical
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
32
Theory: Substructuring
CASE 5: PORTAL FRAME with one of the COLUMNS and
BEAM as ANALYTICAL SUBSTRUCTURE
m1
u2
u1
m1
u2
u1
Red : Experimental
Blue: Analytical
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
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Theory: Substructuring
CASE 6: MULTI-BAY MULTI-STORY FRAME with
ANALYTICAL SUBSTRUCTURING
m2
m1
u2
u1
Red : Experimental
Blue: Analytical
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
34
Theory: Substructuring
CASE 6: MULTI-BAY MULTI-STORY FRAME with
ANALYTICAL SUBSTRUCTURING
m2
u2
m1
u1
Red : Experimental
Blue: Analytical
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
35
Theory: Substructuring
CASE 6-1: MULTI-BAY MULTI-STORY FRAME with
ANALYTICAL SUBSTRUCTURING
m2
m1
u4
u3
u2
u1
Red : Experimental
Blue: Analytical
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
36
Theory: Substructuring
CASE 6-1: MULTI-BAY MULTI-STORY FRAME with
ANALYTICAL SUBSTRUCTURING
m2
m1
u4
u3
u2
u1
Red : Experimental
Blue: Analytical
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
37
Theory: Integration Methods
A straightforward integration application: Explicit Newmark Integration
m2
u2
m1
u1
Analytical
substructure
0   u1   c11 c12   u 1   f a  f e 
 m1 




m  u g
m 2  u 2  c 21 c 22  u 2   f a 
 2
m1
0

Experimental
substructure
m

u
c
u
f
p
  c u  f  p
mu
 0
1. Determine the initial values of response variables: u 0 , u 0 , u
2. Calculate the effective mass: m eff  m  Δt γ c
Δt: integration time step, : integration parameter
3. For each time step i; 1 ≤ i ≤ N, N: total number of steps
 i-1
a. Compute the displacement: u i  u i-1  Δt  u i-1  Δt 2 2  u
b1. Compute the force f a ,i corresponding to the displacement u 2,i  u 1,i from the constitutive


relationship of the analytical spring
b2. Apply the displacement u 1,i to the experimental spring and measure the corresponding force f e,i
b3. Determine f i from f e,i and f a ,i by using the equation for f in Eq. 3
~  u  Δt 1  γ u

c. Compute the predicted velocity: u
i
i-1
i-1
~
d. Compute the effective force: p eff  p i  f i  c u
i
 i  p eff
e. Compute the acceleration by solving the linear system of equations: m eff u
~  Δt γ u
 i
f. Compute the velocity: u i  u
i
g. Increment i and go to step a
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
38
Theory: Integration Methods
The most common integration for pure numerical case: Implicit Newmark
Not suitable for hybrid simulation
 Nonuniform displacement increments: velocity and acceleration oscillations within the step
F
F
ti+1
ti
A B
k=1
ti+1
B
k=2
ti
A
δ
δ
 Displacement overshoot: artificial unloading
k=1
F
F
ti+1
ti
A B
ti+1 B
ti
δ
A
k=2
δ
 Iterations may not converge !
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
39
Theory: Integration Methods
The most common integration for pure numerical case: Implicit Newmark
HS compatible alternatives:
 Implicit Newmark Integration with Fixed Number of Iterations
 Uniform displacement increments
 Number of iterations constant  No convergence problems
 Number of iterations should be determined with prior analyses
 Very suitable for slow hybrid simulation with restricted use in real-time hybrid simulation
 Alpha-Operator Splitting (OS) Method
 Tangential stiffness matrix not required
 Iterations are not required (one predictor & one corrector)  No convergence problems
 Computationally efficient
 Numerical damping present
 Very suitable for slow and real-time hybrid simulation for softening systems
 Explicit Newmark Integration
 Initial and tangential stiffness matrices not required
 Iterations are not required  No convergence problems
 Computationally very efficient
 No numerical damping
 Conditionally stable
 Very suitable for slow and real-time hybrid simulation when stability criterion is met
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
40
Theory: Simulation Errors
ERROR SOURCES
 Errors due to Structural Modeling
 Errors due to Numerical Methods
Errors due to
numerical solution
nature of HS
 Experimental Errors: 1) Random or 2) Systematic
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
41
Theory: Simulation Errors
Random errors:
 No distinguishable pattern & generally no specific physical effects are anticipated
 Random electrical noise in wires and electronic systems
 Random rounding-off or truncation in the A/D conversion of electrical signals
 Random noise in measured forces is problematic  excites spurious response in higher modes
Systematic errors:
 Measurement errors (Errors in load cells & displacement transducers of actuators)
 Calibration
 Friction or slippage (gaps) in the attachments
 A/D and D/A conversion (Digital controllers & digital transducers for improved accuracy)
 Hybrid simulation technique (ramp and hold, continuous, real-time)
 Servo-hydraulic closed control loop
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
42
Theory: Simulation Errors
Errors due to HS technique (Systematic)
Ramp and Hold Method
Measure Forces
Disp.
Hold
Computation
duration
Ramp
Hold
Ramp
Computation
duration
Time
 Force relaxation during hold phase
 Discontinuity in velocity
 Not applicable in real-time HS
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
43
Theory: Simulation Errors
Errors due to HS technique (Systematic)
Continuous Testing (Predictor-Corrector Algorithms)
Disp.
Correct
Predict
Ramp
Hold
Computation duration
Time
 Continuous movement of actuators
 Preferred HS technique
 Indispensable for real-time HS and geographically distributed HS
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
44
Theory: Simulation Errors
Control loop errors (Systematic)
 Actuator dynamics
 Servo-valve
 Hydraulic power-supply
 Control-loop dynamics
 Inherent lag in the displacement response
 PIDF gains
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
45
Theory: Simulation Errors
Control loop errors (Systematic)
•
•
Integration: Command displacement & measured force
True behavior: Measured displacement & measured force
Restoring
Force
Restoring
Force
Overshooting
Increased
Damping
Measured
force
Displacement
Displacement
Command Overshoot
Restoring
Force
Undershooting or delay
Negative
Damping
&
Instability
Displacement
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
46
Theory: Simulation Errors
Control loop errors (Systematic)
•
•
Integration: Command displacement & measured force
True behavior: Measured displacement & measured force
Restoring
Force
higher mode
Cumulative errors increase with ωΔt
(Shing and Mahin, 1983)
ΔF (higher mode)
lower mode
ΔF (lower mode)
Displacement
Undershoot Command
• Integration methods which introduce numerical damping to suppress the excitation of higher
modes can be used to overcome the effects of these errors
• Adaptive minimal control synthesis (MCS) algorithm which provides adaptive gain settings
as the test specimen properties change can be used instead of PID control algorithm
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
47
Theory: Simulation Errors
Control loop errors (Systematic)
Error Identification: Free vibration
Stage 1: Push the hybrid structure, generally in the first mode, to
a displacement within the linear range
Stage 2: Run the free vibration hybrid simulation test from the
displaced configuration
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
48
Theory: Simulation Errors
Control loop errors (Systematic)
Error Identification: Free vibration
Computed displacement [in.]
No error
Overshoot
Undershoot
or lag
Pushover
Free Vibration
Time [sec]
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
49
Theory: Geographically Distributed HS
Lab 1 in The Americas
Lab 3 in Europe
Lab 2 in Asia
Lab 4 in Australia
Pan, P., Tomofuji, H., Wang, T., Nakashima, M., Ohsaki, M., & Mosalam, K.M., “Development of Peerto-Peer (P2P) Internet Online Hybrid Test System,” EESD, 35: 867-890, 2006.
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
50
Theory: Real-time HS
 Requirement for real time: Loading rate = computed velocity
 Slow HS sufficient for most cases when rate effects are not important
 Real-time HS essential for rate-dependent materials and devices, e.g.
viscous dampers or triple friction pendulum isolators
 RTHS classified into two groups:
 RTHS conducted in a discrete actuator configuration
 RTHS conducted in a shaking table configuration (Application II)
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
51
Application I: HS of Structural
Insulated Panels (SIPs)
Motivation for Hybrid Simulation
 Structural Insulated Panels (SIPs) are composite panels for energy efficient
construction
 Composed of an energy-efficient core placed in between facing materials
 Their application in seismically hazardous regions is limited due to
somewhat unacceptable performance as demonstrated by cyclic testing
 Limited number of tests with more realistic dynamic loading regimes
 Hybrid simulation is ideal to test SIPs with a variety of structural
configurations and ground motion excitations
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
52
Application I: HS of Structural
Insulated Panels (SIPs)
Test Setup
Loading Steel Tube
Actuator
Reconfigurable
Reaction Wall
Specimen
Support beam
Gravity Loading
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
53
Application I: HS of Structural
Insulated Panels (SIPs)
Test
Setup
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
54
Application I: HS of Structural
Insulated Panels (SIPs)
7/16”
OSB Skins
(~11 mm)
3-5/8” EPS
Insulating Foam
(~92 mm)
Test Specimen
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
55
Application I: HS of Structural
Insulated Panels (SIPs)
Test Setup
and
Specimen
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
56
Application I: HS of Structural
Insulated Panels (SIPs)
Tube
sliding
Instrumentation
Top gap opening
Top
vertical
sliding
Bottom gap opening
Bottom
vertical
sliding
Left Uplift
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
Right
Uplift
57
Application I: HS of Structural
Insulated Panels (SIPs)
Test Matrix
Specimen Protocol Gravity Nail spacing [in]
Remarks
S1
CUREE
No
6
Conventional wood panel
S2
CUREE
No
6
-
S3
CUREE
Yes
6
-
S4
HS
Yes
6
Near-fault pulse-type GM
S5
HS
Yes
3
Near-fault pulse-type GM
S6
CUREE
Yes
3
-
S7
HS
Yes
3
S8
HS
Yes
3
Long duration, harmonic GM
Near-fault GM; 3 stories computational
substructure
Investigate the effects of:
 Lateral loading: CUREE protocol vs HS
 Type of ground motion (Pulse type vs Long duration, harmonic)
 Presence of an analytical substructure
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
58
Application I: HS of Structural
Insulated Panels (SIPs)
c
Hybrid
Simulation
m
Specimens S4, S5, S7
Specimen
m (kip-sec2/in)
ξ
k (kip/in)
c (kip-sec/in)
T (sec)
S4
0.0325
0.05
18
0.0076
0.27
S5
0.0325
0.05
32
0.0102
0.20
S7
0.0325
0.05
32
0.0102
0.20
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
59
Application I: HS of Structural
Insulated Panels (SIPs)
Hybrid
Simulation
m
m
Specimen S8
m
u4
c=αm
c=αm
u3
c=αm
Analytical
DOF
u2
u1
m
c=αm
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
Experimental
DOF
60
Application I: HS of Structural
Insulated Panels (SIPs)
Hybrid Simulation: Numerical Integration
 Explicit Newmark Integration with γ=0.5
 Does not require iterations
 Does not require knowledge of initial experimental stiffness
Specimen
m
k
T (sec)
dt (sec)
dt/T
S4
0.0325
18
0.27
0.0050
0.0180 ≤ 1/π
S5
0.0325
32
0.20
0.0050
0.0250 ≤ 1/π
S7
0.0325
32
0.20
0.0125
0.0625 ≤ 1/π
S8
-
-
T4=0.10
0.0050
0.0500 ≤ 1/π
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
61
Application I: HS of Structural
Insulated Panels (SIPs)
Hybrid Simulation: Ground Motions
Los Gatos, Loma Prieta, 1989
Vinadel Mar, Chile, 1985
0
0
-0.4
-0.5
-0.8
0
10
20
30
Vel (in/sec)
20
0
25
75
100
0
-10
-10
0
10
20
PGV = 11.9 in/s
10
0
30
-20
0
25
50
75
100
5
5
PGD = 3.87 in
PGD = 4.53 in
0
-5
50
20
PGV = 20.0 in/s
10
-20
PGA = 0.54 g
0.5
0
0
10
20
Time (sec)
30
-5
0
25
50
75
Time (sec)
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
Long duration, harmonic GM
PGA = 0.61 g
0.4
Disp (in/sec)
Near fault, pulse-type GM
Acc (g)
0.8
100
62
Application I: HS of Structural
Insulated Panels (SIPs)
Test Results: Global Parameters
10
10
Full-History
Envelope
6
6
4
4
2
0
-4
-4
-6
-6
-3
-2
-1
0
1
2
Displacement [inch]
Initial stiffness =fi /di
Force capacity = fc
Ductility =du/dy
Hysteretic energy =  fdx
3
4
5
dc, fc
di, fi
du, 0.75fc
dp, fp
0
-2
-4
dy, fy
2
-2
-8
-5




8
Force [kip]
Force [kip]
8
envelope
-8
-5
dn, fn
-4
-3
-2
-1
0
1
2
Displacement [inch]
3
4
5
 Positive peak displacement = dp
 Negative peak displacement = dn
 Residual displacement
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
63
Application I: HS of Structural
Insulated Panels (SIPs)
Test Results: Peaks of local responses
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
64
Application I: HS of Structural
Insulated Panels (SIPs)
HS Results: Effect of Lateral Loading (S6 vs S7)
Cyclic Testing with CUREE
Protocol for Ordinary GM (S6)
Hybrid Simulation with Long
Duration, Harmonic GM (S7)
Vinadel Mar, Chile, 1985
0
00.5
5
Acc (g)
4
2
0
-0-0.5
-0
1
Vel (in/sec)
0
-1
-2
25
50
75
100
0
- -10
- -20
-4
5
0
500
1000
1500
2000
Time [sec]
2500
3000
3500
Nail spacing: 3”
PGV = 11.9 in/s
10
-3
-5
0
20
Disp (in/sec)
Displacement [inch]
3
PGA = 0.54 g
0
25
50
75
100
PGD = 3.87 in
0
-5
0
25
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
50
75
Time (sec)
100
65
Application I: HS of Structural
Insulated Panels (SIPs)
HS Results: Effect of Lateral Loading (S6 vs S7)
20
15
Force [kips]
10
5
Specimen
S6
S7
0
Initial Stiffness [kip/in]
32.7
33.2
-5
Force Capacity [kip]
16.2
15.5
Ductility
4.8
3.4
Hysteretic Energy [kip-in]
309.9
1077.8
-10
S6 (CUREE)
S7 (HS)
-15
-20
-6
-3
0
3
Displacement [inch]
Specimen
6
Peak Disp. (+)
S6
4.7
S7
3.3
Peak Disp. (-)
-4.7
-4.2
Residual Disp.
0.0
0.3
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
66
Application I: HS of Structural
Insulated Panels (SIPs)
HS Results: Effect of Ground Motion Type (S5 vs S7)
Hybrid Simulation with
Pulse-Type GM (S5)
Hybrid Simulation with Long
Duration, Harmonic GM (S7)
Los Gatos, Loma Prieta, 1989
Vinadel Mar, Chile, 1985
Acc (g)
0.8
PGA = 0.61 g
0.4
0
0
-0.4
-0.5
-0.8
0
10
20
30
0
Vel (in/sec)
20
0
0
-10
-10
0
10
20
-20
30
0
25
75
100
50
75
100
5
PGD = 3.87 in
PGD = 4.53 in
0
-5
50
PGV = 11.9 in/s
10
5
Disp (in/sec)
25
20
PGV = 20.0 in/s
10
-20
PGA = 0.54 g
0.5
0
0
10
20
Time (sec)
30
Nail spacing: 3”
-5
0
25
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
50
75
Time (sec)
100
67
Application I: HS of Structural
Insulated Panels (SIPs)
HS Results: Effect of Ground Motion Type (S5 vs S7)
20
Force [kips]
15
10
Specimen
S5
S7
5
Initial Stiffness [kip/in]
35.5
33.2
0
Force Capacity [kip]
15.6
15.5
-5
Ductility
3.7
3.4
Hysteretic Energy [kip-in]
363.1
1077.8
-10
S5 (Pulse-type)
S7 (Harmonic)
-15
-20
-6
-3
0
3
Displacement [inch]
Specimen
6
DE
MCE
1.5MCE
Peak Disp. (+)
S5
1.3
S7
1.1
S5
3.5
S7
2.2
S5
5.8
S7
3.3
Peak Disp. (-)
-1.0
-1.0
-3.2
-2.0
-
-4.2
Residual Disp.
0.1
0.0
0.8
0.0
-
0.3
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
68
Application I: HS of Structural
Insulated Panels (SIPs)
HS Results: Effect of Ground Motion Type (S5 vs S7)
20
15
Force [kips]
10
Specimen
5
DE
MCE
1.5MCE
0
Peak Disp. (+)
S5
1.3
-5
Peak Disp. (-)
-1.0
-1.0
-3.2
-2.0
-
-4.2
-10
Residual Disp.
0.1
0.0
0.8
0.0
-
0.3
-20
-6
-3
Specimen
MCE
S5
3.5
S7
2.2
S5
5.8
S7
3.3
S5 (Pulse-type)
S7 (Harmonic)
-15
DE
S7
1.1
S5
S7
S5
S7
0
3
Displacement [inch]
Bottom ver.
sliding
0.26
0.23
0.63
0.45
Bottom gap
opening
0.02
0.02
0.05
0.03
6
Top ver.
sliding
0.27
0.21
0.64
0.43
Top gap
opening
0.03
0.02
0.09
0.04
Uplift
right
0.08
0.15
0.14
0.53
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
Uplift
left
0.07
0.04
0.12
0.09
Tube
sliding
0.18
0.02
0.19
0.06
69
Application I: HS of Structural
Insulated Panels (SIPs)
HS Results: Effect of Analytical Substructuring (S5 vs S8)
Hybrid Simulation with no
Analytical Substructure (S5)
Hybrid Simulation with
Analytical Substructure (S8)
Pulse-Type GM
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
70
Application I: HS of Structural
Insulated Panels (SIPs)
HS Results: Effect of Analytical Substructuring (S5 vs S8)
6
S5 (No analytical substructure)
S8 (Analytical substructure)
20
15
Force [kips]
10
Specimen
S5
S8
Initial Stiffness [kip/in]
35.5
38.3
Force Capacity [kip]
15.6
16.0
Ductility
3.7
4.0
5
0
-5
-10
Specimen
-15
-20
-6
-3
Specimen
DE
MCE
S5
S8
S5
S8
0
3
Displacement [inch]
Bottom ver.
sliding
0.26
0.37
0.63
0.65
Bottom gap
opening
0.02
0.03
0.05
0.03
6
DE
MCE
Peak Disp. (+)
S5
1.3
S8
1.2
S5
3.5
S8
2.4
Peak Disp. (-)
-1.0
-1.7
-3.2
-3.1
Residual Disp.
0.1
0.0
0.8
0.4
Top ver.
sliding
0.27
0.37
0.64
0.55
Top gap
opening
0.03
0.04
0.09
0.05
Uplift
right
0.08
0.09
0.14
0.16
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
Uplift
left
0.07
0.11
0.12
0.27
Tube
sliding
0.18
0.13
0.19
0.14
71
Application I: HS of Structural
Insulated Panels (SIPs)
Concluding Remarks
 HS provides the force-deformation envelope that can also be obtained from a
cyclic test. But it also provides response values, where the cyclic test would
require complimentary analytical simulations for these values.
 HS with harmonic ground motion provides a slightly more degraded postyield response than the CUREE protocol due to the large number of cycles
demanded by the harmonic ground motion.
 Based on global and local displacements, near-fault pulse-type GM is more
critical & damaging for SIPs compared to long duration GM with many cycles.
 Although the global and local responses of SIPs with and without analytical
substructuring are not dramatically different, there is a need for analytical
substructuring for a more realistic dynamic representation.
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
72
Application II: RTHS of Electrical Insulator
Posts on a Smart Shaking Table
: Primary power lines
: Secondary power lines
* Courtesy of Wikipedia
Disconnect switches are
key components of
power transmission and
distribution systems.
1. Primary power lines
2. Ground wire
3. Overhead lines
4. Transformer
5. Disconnect switch
6. Circuit breaker
7. Current transformer
8. Lightning arrester
9. Main transformer
10. Control building
11. Security fence
12. Secondary power lines
Major elements of an electrical substation (distribution substation shown)
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
73
Application II: RTHS of Electrical Insulator Posts
on a Smart Shaking Table
1. Disconnect switches: Key components of power transmission & distribution
systems to control flow of electricity between substation equipment & to isolate
them for maintenance.
2. Seismic qualification tests in typical field installation according to IEEE 693
(Recommended Practices for Seismic Design of Substations) requirements.
Typical field installation of vertical‐break 500‐kV disconnect 3‐phase switch
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
74
Application II: RTHS of Electrical Insulator
Posts on a Smart Shaking Table
Motivation for Hybrid Simulation
Ertaishan Substation (220kV) Destruction, Yingxiu Town
Wenchuan Earthquake, May 12, 2008 [Q. Xie, Tongji Univ.]
EQ damage to 500 kV
vertical disconnect switch
[E. Fujisaki, PG&E]
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
75
Application II: RTHS of Electrical Insulator
Posts on a Smart Shaking Table
Motivation for Hybrid Simulation
500 kV switch
230 kV switch
IEEE693 requires seismic qualification of disconnect switches by shaking table tests 
A disconnect switch & its support structure should be mounted to a shaking table & tested
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
76
Application II: RTHS of Electrical Insulator Posts
on a Smart Shaking Table
Several tested configurations
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
77
Application II: RTHS of Electrical Insulator Posts
on a Smart Shaking Table
500-kV switch testing
Support structure identification tests (stiffness & frequency) with two typical installation:
a) Leveling bolts, no grout
b) Leveling bolts with space packed with grout
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
78
Application II: RTHS of Electrical Insulator Posts
on a Smart Shaking Table
Sub-structuring tests w/o support structure in different configurations
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
79
Application II: RTHS of Electrical Insulator Posts
on a Smart Shaking Table
Test w/ support structure
B
Vertical Disp. [in.]
Horizontal Disp. [in.]
A
Y
Z X
B
Test w/o support
structure
A
5
A: Trans. in Y dir.
0
-5
0
10
20
30
40
50
60
B: Rot. @ X dir.
0.5
0
-0.5
0
10
20
30
Time [sec]
40
50
60
Time [sec.]
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
80
Application II: RTHS of Electrical Insulator Posts
on a Smart Shaking Table
Y-direction Input
(Signal A only)
Jaw Insulator Bottom Strain [strain]
Strain at Jaw Insulator Bottom East Side - Open/Open Conf.
300
w/o support
w/ support
200
100
0
-100
-200
-300
0
10
20
30
Time [sec]
300
200
200
100
0
-100
A
0
-100
-200
-300
-300
0
200
East SG#2 [ strain]
60
100
-200
-200
50
Strains at Jaw Insulator Bottom w/ support structure
300
West SG#4 [ strain]
West SG#4 [ strain]
Strains at Jaw Insulator Bottom w/o support structure
40
WEST
SG#4
-200
EAST
SG#2
0
200
East SG#2 [ strain]
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
81
Application II: RTHS of Electrical Insulator Posts
on a Smart Shaking Table
Y-direction + Rotation Input
(Signals A + B)
Jaw Insulator Bottom Strain [strain]
Strain at Jaw Insulator Bottom East Side - Open/Open Conf.
300
w/o support
w/ support
200
100
0
-100
-200
-300
0
10
20
30
Time [sec]
300
200
200
100
0
-100
60
B
A
100
0
-100
-200
-200
-300
-300
-200
0
200
East SG#2 [ strain]
50
Strains at Jaw Insulator Bottom w/ support structure
300
West SG#4 [ strain]
West SG#4 [ strain]
Strains at Jaw Insulator Bottom w/o support structure
40
WEST
SG#4
EAST
SG#2
-200
0
200
East SG#2 [ strain]
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
82
Application II: RTHS of Electrical Insulator
Posts on a Smart Shaking Table
Motivation for Hybrid Simulation
 Hybrid simulation: a cost effective and efficient alternative to the
conventional shaking table testing of the disconnect switches
 Requirement for real-time: Rate-dependency of some types of insulator
posts, e.g. polymer composite insulators, mandates use of RTHS
 Requirement for a shaking table configuration: Distributed mass of insulator
posts prevents practical use of actuators at discrete locations along the
height & requires RTHS conducted on shaking table configurations.
 A RTHS system is developed for testing insulator posts of high
voltage disconnect switches on a “smart” shaking table
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
83
Application II: RTHS of Electrical Insulator Posts
on a Smart Shaking Table
Jaw
Post
Braced
frame
support
structure
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
84
Application II: RTHS of Electrical Insulator Posts
on a Smart Shaking Table
Insulator
post
Disconnect
switch
Insulator
post
Disconnect
switch
2D Support
structure
3D Support
structure
For benefits of HS: Support structures  computational substructures
& insulator posts  physical substructures
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
85
Application II: RTHS of Electrical Insulator Posts
on a Smart Shaking Table
A method of
analysis where a
structure is split
into physical and
numerical
substructures
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
86
Application II: RTHS of Electrical Insulator Posts
on a Smart Shaking Table
RTHS: Real Time
Dynamic
Actuator &
Load Cell
Physical Insulator Substructure
(assumed 1D)
Hybrid simulation
Movable platform
Fixed tracks Calculated support structure response applied to movable platform
Force feedback
Displacement command
Dynamic DOF Computational Substructure
Earthquake motion
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
87
Application II: RTHS of Electrical Insulator Posts
on a Smart Shaking Table
Comparison RTHS vs. Shaking Table tests
VS.
RTHS test
(UC Berkeley, 2011)
Full switch shaking table test
(PEER, 2008)
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
88
Application II: RTHS of Electrical Insulator
Posts on a Smart Shaking Table
Real-time Hybrid Simulation System
m, c
F, u
k=F/u
c
k
ug
m
m, k, & c: mass, spring, & damping constant for SDOF system representing support frame
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
89
Application II: RTHS of Electrical Insulator
Posts on a Smart Shaking Table
Real-time Hybrid Simulation System
ma  cv  ku  f  mug
f
c
k
ug
m
Force f includes inertia & damping forces acting on the insulator since HS is conducted in real time
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
90
Application II: RTHS of Electrical Insulator
Posts on a Smart Shaking Table
Real-time Hybrid Simulation System
Insulator
DAQ & Computational platform
(DSP)
Controller
Uniaxial shaking
table
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
91
Application II: RTHS of Electrical Insulator
Posts on a Smart Shaking Table
Real-time Hybrid Simulation System
Computational Algorithm: Explicit Newmark Integration
Initialize u 0 , u 0 , u0 , meff  m  Δt  γ  c, i  1
1) ~
u i  u i-1  Δt  1  γ  ui-1


2) u i  u i-1  Δt  u i-1  Δt 2 2  ui-1
3) Apply u i & Measure f i
4) peff   m ug i  k u i  f  c ~
u i
5) ui  peff meff  m table 
6) u i  ~
u i  Δt  γ  ui
One simulation step completed in one milisecond!
7) Set i  i  1
8) Go to Step 1
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
92
Application II: RTHS of Electrical Insulator
Posts on a Smart Shaking Table
Real-time Hybrid Simulation System
Implementation of Computational Algorithm
Digital signal processor (DSP) I/O module of Pacific Instruments (PI) DAQ system
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
93
Application II: RTHS of Electrical Insulator
Posts on a Smart Shaking Table
Real-time Hybrid Simulation System
PIDF
Feed-forward error compensation
Add the error to the command
1.2
1
Command
Feedback
1
0.6
0.4
0.4
Error (e) [inch]
Displacement(inch)
0.6
0.2
0
-0.2
-0.4
0.2
0
-0.2
e = 0.0174v
-0.4
-0.6
-0.6
-0.8
e = 0.042v+0.513
-0.8
-1
-1.2
10
e=0.042v-0.513
0.8
0.8
10.2
10.4
10.6
Time(sec)
10.8
11
-1
-40
-30
-20
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
-10
0
10
20
Velocity (v) [inch/sec]
30
40
94
Application II: RTHS of Electrical Insulator
Posts on a Smart Shaking Table
Real-time Hybrid Simulation System
Feed-forward error compensation
1.2
Command
Feedback
0.8
0.8
0.6
0.6
0.4
0.2
0
-0.2
-0.4
0.4
0.2
0
-0.2
-0.4
-0.6
-0.6
-0.8
-0.8
-1
-1
-1.2
10
10.2
10.4
10.6
Time(sec)
No correction
10.8
Command
Feedback
1
Displacement(inch)
Displacement(inch)
1
11
10
10.2
10.4
10.6
Time(sec)
10.8
11
Feed-forward error correction
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
95
Application II: RTHS of Electrical Insulator
Posts on a Smart Shaking Table
Real-time Hybrid Simulation Framework
Verification of algorithm implementation and measurements
Analytical Substructure
Test #
Stiffness, k,
[kip/in]
Mass, m,
slug
Period,
T=2π(m/k)0.5,
sec
Damping ratio
Excitation
Scale
1
4.4
150
0.37
1%
15%
2
4.4
150
0.37
1%
20%
3
4.4
150
0.37
1%
25%
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
Application II: RTHS of Electrical Insulator
Posts on a Smart Shaking Table
Real-time Hybrid Simulation System
Verification of algorithm implementation and measurements
25% scale
2
0
F
Displacement [inch]
-2
2
Scale
10%
20%
…
Disp.
1 in.
2 in.
20% scale *25/20
0
-2
2
15% scale *25/15
d
0
-2
0
10
20
30
Time [sec]
40
50
60
c
k
m
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
97
Application II: RTHS of Electrical Insulator Posts
on a Smart Shaking Table
300
Comparison RTHS vs.
Shaking Table tests
A c c eleration [g]
HS Test
100
0
-100
100
0
-100
-200
-200
-300
-300
0
-200
0
200
SG#3 [ strain]
-200
0
200
SG#16 [ strain]
-5
0
A c c eleration [g]
PEER test
200
SG#17 [ strain]
SG#4 [strain]
200
Accelerations at top
Strains at bottom
5
300
HS test
10
20
30
Time [sec]
40
50
SG#3
60
Strains measured at
insulator bottom
SG#4
PEER test
5
0
Acceleration measured
at insulator top
-5
0
10
20
30
Time [sec]
40
50
60
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
98
Application II: RTHS of Electrical Insulator Posts
on a Smart Shaking Table
6
HS Test
Disp. [inch]
4
Comparison RTHS vs.
Shaking Table tests
2
0
-2
-4
Total and Relative
Displacements at top
-6
0
10
20
30
Time [sec]
40
50
60
PEER Test
4
HS Test
2
Disp. [inch]
Rel. Disp. [inch]
6
0
2
0
-2
-4
-2
-6
0
10
20
30
Time [sec]
40
50
60
0
10
20
30
Time [sec]
40
50
60
2
HS Test
PEER Test
4
Disp. [inch]
Rel. Disp. [inch]
6
PEER Test
0
-2
2
0
-2
-4
0
10
20
30
Time [sec]
40
Relative Displacements
50
60
-6
9
10
11
12
13
14
15
Time [sec]
16
17
18
19
20
Total Displacements
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
99
Application II: RTHS of Electrical Insulator
Posts on a Smart Shaking Table
Real-time Hybrid Simulation System
Comparison with conventional shaking table tests
Acceleration [g]
Accelerations at Insulator Top
6
6
4
4
2
2
0
0
-2
-2
-4
Acceleration [g]
-4
Top of support structure: Real-time HS
-6
6
4
4
2
2
0
0
-2
-2
Top of support structure:
Conventional shaking table
-6
0
10
20
30
Time [sec]
40
Top of insulator: Real-time HS
-6
6
-4
$
$$$
-4
Top of insulator: Conventional shaking table
-6
50
0
10
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
20
30
Time [sec]
40
50
100
Application II: RTHS of Electrical Insulator
Posts on a Smart Shaking Table
Real-time Hybrid Simulation System
Comparison with conventional shaking table tests
Strains at Insulator Bottom
$
Strain [strain]
400
200
0
-200
West: Real-time HS
East: Real-time HS
-400
$$$
Strain [strain]
400
200
0
-200
-400
East: Conventional shaking table
West: Conventional shaking table
0
10
20
30
Time [sec]
40
50
0
10
20
30
Time [sec]
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
40
50
101
Application II: RTHS of Electrical Insulator
Posts on a Smart Shaking Table
Real-time Hybrid Simulation System
Comparison with conventional shaking table tests
Relative displacement of insulator top w.r.t. top of support structure
3
2
1
Real-time hybrid simulation
$
Displacement [inch]
0
-1
-2
-3
3
2
1
Conventional shaking table
$$$
0
-1
-2
-3
0
5
10
15
20
25
Time [sec]
30
35
40
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
45
50
102
Application II: RTHS of Electrical Insulator
Posts on a Smart Shaking Table
Parametric Study
Polymer
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
Porcelain
103
Application II: RTHS of Electrical Insulator
Posts on a Smart Shaking Table
Parametric Study
 13 support structure stiffness, k, values between
2.2 kips/in and 60 kips/in
 3 damping ratios for support structure: ξ= 1%, 3% , 5%
 Tests with 10%-scale IEEE motion to ensure linear insulator behavior
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
104
Application II: RTHS of Electrical Insulator
Posts on a Smart Shaking Table
Parametric Study: Natural Frequencies
k [kip/in]
fss [Hz]
fss / fins (polymer)
60.0
10.0
1.6
55.0
9.6
1.6
50.0
9.2
1.5
44.0
8.6
1.4
40.0
8.2
1.3
35.0
7.7
1.2
30.0
7.1
1.1
22.0
6.1
1.0
16.0
5.2
0.8
11.0
4.3
0.7
7.0
3.4
0.6
4.4
2.7
0.4
2.2
1.9
0.3
fss / fins (porcelain)
2.0
1.9
1.8
1.7
1.6
1.5
1.4
1.2
1.0
0.8
0.7
0.5
0.4
f ss  1 / 2 k m
m = 150 slug
16
25
Polymer
14
Spectral Acceleration SA [g]
f = 6.20 Hz
f = 5.13 Hz
Porcelain
20
12
10
15
8
10
6
4
5
2
0
0
2
4
6
Frequency [Hz]
8
10
0
0
0
2
4
6
Frequency [Hz]
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
8
10
105
Application II: RTHS of Electrical Insulator
Posts on a Smart Shaking Table
Parametric Study: Effect of Insulator Type
Failure strains from
fragility tests:
Polymer  4800 μstrain
Porcelain  1130 μstrain
Peak strain / Failure strain (DCR)
0.1
Polymer
Porcelain
0.08
0.06
0.04
0.02
0
0
0
1
1
2
3
4
5
6
7
8
2
3
4
5
6
7
8
9
Support structure uncoupled frequency fss [Hz]
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
9
10
10
11
11
106
Application II: RTHS of Electrical Insulator
Posts on a Smart Shaking Table
Parametric Study: Effect of Support Structure
Ratio of uncoupled frequencies fss / fins
80
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
1% Damping
3% Damping
5% Damping
70
0.07
0.06
60
Peak strain [ strain]
0.05
50
0.04
40
0.03
30
0.02
20
0.01
10
0
Peak strain / Failure strain
Strains:
Porcelain
Insulator
0
1
2
3
4
5
6
7
8
9
Support structure uncoupled frequency fss [Hz]
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
10
0
11
107
Application II: RTHS of Electrical Insulator
Posts on a Smart Shaking Table
Parametric Study: Effect of Support Structure
Displacements:
Porcelain
Insulator
Ratio of uncoupled frequencies fss / fins
2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
Relative displacement of
insulator w.r.t. ground
1.75
Displacement [in.]
1.5
1.25
1
0.75
0.5
1% damping
3% damping
5% damping
0.25
0
0
1
2
3
4
5
6
7
8
9
Analytical substructure uncoupled frequency fss
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
10
11
108
Application II: RTHS of Electrical Insulator
Posts on a Smart Shaking Table
Parametric Study: Effect of Support Structure
Ratio of uncoupled frequencies fss / fins
450
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0.09
1% Damping
5% Damping
400
0.08
Peak strain [ strain]
350
0.07
300
0.06
250
0.05
200
0.04
150
0.03
100
0.02
50
0.01
0
0
1
2
3
4
5
6
7
8
9
Analytical substructure uncoupled frequency fss [Hz]
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
10
Peak strain / Failure strain
Strains:
Polymer
Insulator
0
11
109
Application II: RTHS of Electrical Insulator
Posts on a Smart Shaking Table
Parametric Study: Effect of Support Structure
Insulator top wrt ground [in.]
Displacements:
Polymer
Insulator
Ratio of uncoupled frequencies fss / fins
1.5
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
Relative displacement of
insulator w.r.t. ground
1.25
1% damping
3% damping
5% damping
1
0.75
0.5
0.25
0
0
1
2
3
4
5
6
7
8
9
Analytical substructure uncoupled frequency fss
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
10
11
110
Application II: RTHS of Electrical Insulator
Posts on a Smart Shaking Table
Concluding Remarks
 Good match of the results with a benchmark shaking table test is a strong
verification of HS
 Economically and time efficiently conducted 78 RTHS tests and results
regarding the design of disconnect switches related to the selection of both
the insulators and support structures are a proof of the usefulness of HS
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
111
Future Directions
 Direct consideration of transfer system and analytical-experimental
boundary in the HS solution
control
applied
  Ru, u  Fa t   Fc t 
Governing PDE : M u
Boundary Conditions : G(u, u )  0


Set of DifferentialAlgebraic Equations (DAE)
PID Control : H Fc , u, u ,  udt  0
 Solution affected more from the errors as
# of DOF increases
 Need to reduce the computation duration
(parallel computing)
[OpenSees-SP, OpenSees-MP]
C omp u ta tion T ime pe r T ime Step [ms ]
 HS of analytical substructures with large #
of DOF:
40
35
30
MATLAB
Old OpenSees
New OpenSees
FORTRAN
25
20
15
450
DOF
10
5
0
0
1000
2000
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
3000 4000
# of DOF
5000
6000
7000
112
Future Directions
Acceleraation [g]
Optimize design of support structure to improve the switch seismic response
1
0
-1
0
0.5
1
1.5
2
2.5
Time [sec]
3
3.5
4
4.5
?
Computational or
experimental
Acceleraation [g]
Accelerations at Insulator Top
1
0
-1
0
0.5
1
1.5
2
2.5
Time [sec]
3
3.5
4
4.5
Accelerations at Switch Base (Ground Motion)
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
113
Future Directions
Displacement (inches)
 Need for a mixed control as a combination of acceleration control for
higher frequencies and displacement control for lower frequencies in
RTHS on smart shaking table configurations
2
Cmd
fbk
Feedback
1
0
-1
Command
-2
0
5
10
15
20
25
Time (sec)
30
35
40
45
4
Measured
Target
Measured
Sa (g)
3
2
1
Target
0
0
0.5
1
1.5
period (sec)
2
2.5
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
3
114
Future Directions
 Need for a mixed control as a combination of acceleration control for
higher frequencies and displacement control for lower frequencies in
RTHS on smart shaking table configurations
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
115
Future Directions
 Need for a mixed control as a combination of acceleration control for
higher frequencies and displacement control for lower frequencies in
RTHS on smart shaking table configurations
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
116
Thank You!
Questions? Comments?
Seminar on Recent Advances & Directions in Earthquake Eng., Minho Univ., Portugal, Oct. 2012
117