Author: ​Anastasios G. Sextos

1. Anastasios Sextos
Aristotle University
Thessaloniki
University
of Bristol
Expert systems for advanced seismic FE
modelling of bridges and buildings using
OpenSees

2. Motivation VisionBuild-X Bridge-X Expert System
• “I know nothing but I want to
learn quickly”
• “Opensees does not have a
GUI!!. Give me another program”
• “I need to visualize pre- and
post-processing results”
Undergraduates / Postgraduates
• reduced AND uniform epistemic
uncertainty in FE modeling of structures
• the more user-friendly, the narrower the
dispersion of results
• a framework for driving our research
advancements into a single platform
Researchers
• steep learning curve
• build upon existing expertise in
the group and avoid repeating again
and again the same tutorials from
scratch
Advisors
The Opensees wishlist

3. Motivation VisionBuild-X Bridge-X Expert System
•A wizard-like process flow, restricting the user
from navigating freely through the software.
• Background automations that minimize the time
required for pre-processing by calling internal
element generators and completing missing data
• Expert suggestions at every step of the
simulation process for selecting the most
appropriate modeling approach for each sub-
component (column, beam or pier, abutment,
deck, foundation)
• State-of-the-art add-ons that call and execute
external Matlab scripts in the background.
•An ad-hoc developed 3D visualization engine for
reviewing the structural system while generating
the FE model or assessing the analysis results.
Aim: improve OpenSees efficiency and
reduce epistemic uncertainty

4. Motivation VisionBuild-X Bridge-X Expert System
Build-X: Program flow

5. Build-X: Program flow
Motivation VisionBuild-X Bridge-X Expert System

6. Build-X: Linear elastic, static & dynamic analysis
Motivation VisionBuild-X Bridge-X Expert System
www.youtube.com/user/asextos2

7. Build-X: nonlinear static analysis
Motivation VisionBuild-X Bridge-X Expert System
www.youtube.com/user/asextos2

8. Bridge-Wizard (Bridge-X ver 1.0): Program flow
Create new
project?
OPEN EXISTING
PROJECT
NEW PROJECT
YesNo
GENERAL
GEOMETRY DATA
BRIDGE CURVATURE
DATA
BRIDGE
ELEVATION
DATA
BRIDGE DECK
DATA
BRIDGE PIERS
DATA
BRIDGE
ABUTMENTS DATA
DECK – PIER
CONNECTION
DATA
TIME HISTORY
ANALYSIS DATA
BRIDGE WIZARD
No SSI / BOUNDARYInclude Ground
Yes
PEER NGA
dadabase
ISSARS
Motivation VisionBuild-X Bridge-X Expert System

9. Bridge-Wizard (Bridge-X ver 1.0)
Motivation VisionBuild-X Bridge-X Expert System

10. Suite for seismic assessment of bridges
Bridge-X
2.0
Selection &
Scaling of
earthquake
ground
motions
Frequency-
and intensity-
dependent
LPM for SSI
analysis
Spatially
variable
earthquake
ground
motion model
Release date: 1/1/2018
Motivation VisionBuild-X Bridge-X Expert System

11. 1. Selection of ground motion for minimum
structural variability
Motivation VisionBuild-X Bridge-X Expert System
Record
selection
criteria
Search
database Form
compatible
sets
Rank
eligible
sets
Run
dynamic
analysis
Measure
response
discrepancy
Structure-specific earthquake record selection process

12. Motivation VisionBuild-X Bridge-X Expert System

13. θjk(ω) = tan-1 (Im[γjk(ω)]/ Re[γjk(ω)])
Wave passage
Incoherency
Local site conditions
different earthquake motions
excite at each support
(in terms of
amplitude,
phase and
frequency content)
2.Generation of spatially variable ground motions

14. • m-variate,
• fully non-stationary,
• spectrum-compatible
known fully non-
stationary process
       2 2
, ,SC L C
jj j jj j jjS t a S t t S    
quasi-stationary
corrective process
   
 
 1 1
Im ,
2 , cos arctan
Re ,
m N
jr s
j jr s s rs
r s jr s
H t
f t H t t
H t

   
 
         
      

2.Generation of spatially variable ground motions
Motivation VisionBuild-X Bridge-X Expert System
• Cacciola, P., and Deodatis, G. (2011). “A method for generating fully non-stationary and spectrum-compatible
ground motion vector processes.” Soil Dynamics and Earthquake Engineering, Elsevier, 31(3), 351–360.
• Sextos, A. G., Pitilakis, K. D., and Kappos, A. J. (2003). “Inelastic dynamic analysis of RC bridges accounting
for spatial variability of ground motion, site effects and soil-structure interaction phenomena. Part 1:
Methodology and analytical tools.” Earthquake Engineering & Structural Dynamics, 32(4), 607–627.

15. • m-variate,
• fully non-stationary,
• spectrum-compatible
known fully non-
stationary process
       2 2
, ,SC L C
jj j jj j jjS t a S t t S    
quasi-stationary
corrective process
   
 
 1 1
Im ,
2 , cos arctan
Re ,
m N
jr s
j jr s s rs
r s jr s
H t
f t H t t
H t

   
 
         
      

2.Generation of spatially variable ground motions
Motivation VisionBuild-X Bridge-X Expert System
• Cacciola, P., and Deodatis, G. (2011). “A method for generating fully non-stationary and spectrum-compatible
ground motion vector processes.” Soil Dynamics and Earthquake Engineering, Elsevier, 31(3), 351–360.
• Sextos, A. G., Pitilakis, K. D., and Kappos, A. J. (2003). “Inelastic dynamic analysis of RC bridges accounting
for spatial variability of ground motion, site effects and soil-structure interaction phenomena. Part 1:
Methodology and analytical tools.” Earthquake Engineering & Structural Dynamics, 32(4), 607–627.

16. 2.Generation of spatially variable ground motions
Motivation VisionBuild-X Bridge-X Expert System

17. 2.Generation of spatially variable ground motions
Motivation VisionBuild-X Bridge-X Expert System
Sample function
(1/20)
Mean spectra
(from 20
sample functions)

18. 3.Soil-foundation-structure interaction
Motivation VisionBuild-X Bridge-X Expert System
 Questionable accuracy
 Intensity or frequency
independent approximation
 limited to the most
common scenarios
Analytical solution of
the PDE equations
Truncated simulation
through FEM
Simplified closed form
approximations
 Computationally
expensive
Khatibinia et al (2015)
Kwon et al (2008)
Seismic Reliability-Based Design Optimization:
Reliability of the seismic risk assessment:

19. 3.Soil-foundation-structure interaction
Length: 850m (left branch), 640 (right branch)
Deck: continuous, box-shaped, prestressed concrete
Curvature: 450m radius (the larger curved bridge in Greece)
Number of spans: 10
Maximum pier height: 30m
Construction method: Incremental launching
Foundation: piles
Sextos, Taskari (2017)
Motivation VisionBuild-X Bridge-X Expert System

20. 3.Soil-foundation-structure interaction
Motivation VisionBuild-X Bridge-X Expert System

21. 3.Soil-foundation-structure interaction
Motivation VisionBuild-X Bridge-X Expert System
Lesgidis, N. D., Kwon, O.-S., and Sextos, A. G. (2015). ”
Earthquake Engineering & Structural Dynamics,
44(13), 2137–2156.

22. 3.Soil-foundation-structure interaction
Motivation VisionBuild-X Bridge-X Expert System
Lesgidis, N. D., Sextos, A. G., and Kwon, O.-S. (2016). “Influence of frequency-dependent soil-structure
interaction on the fragility of R/C bridges.” Earthquake Engineering & Structural Dynamics.

23. 3.Soil-foundation-structure interaction
Motivation VisionBuild-X Bridge-X Expert System

24. 3.Soil-foundation-structure interaction
Motivation VisionBuild-X Bridge-X Expert System

25. 3. Effect of SSI frequency dependence on fragility
Motivation VisionBuild-X Bridge-X Expert System
Mean absolute % error in fragility estimates
with shear wave velocity and the mean frequency of excitation

26. Software downloads
Motivation VisionBuild-X Bridge-X Expert System
www.asextos.net/software
www.youtube.com/user/asextos2
Version 2.0: Nicos Psyrras
Version 1.0: Dionisios Panagiotopoulos,
Nicos Gantsidis and Nicos Lesgidis
Academic Advisor: A. Sextos
Developers
Build-X
Version 1.0: Nicos Lesgidis
Academic Advisor: A. Sextos
Bridge Wizard