Expert systems for advanced FE modelling of bridges and buildings using OpenSees

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

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

•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

Build-X: Program flow

Build-X: Linear elastic, static & dynamic analysis
www.youtube.com/user/asextos2

Build-X: nonlinear static analysis

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

Bridge-Wizard (Bridge-X ver 1.0)

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

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

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

• 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

   
 
         
      

• 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.

Sample function
(1/20)
Mean spectra
(from 20
sample functions)

3.Soil-foundation-structure interaction
 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:

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)

Lesgidis, N. D., Kwon, O.-S., and Sextos, A. G. (2015). ”
Earthquake Engineering & Structural Dynamics,
44(13), 2137–2156.

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.

3. Effect of SSI frequency dependence on fragility
Mean absolute % error in fragility estimates
with shear wave velocity and the mean frequency of excitation

Software downloads
www.asextos.net/software
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

Expert systems for advanced FE modelling of bridges and buildings using OpenSees

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Expert systems for advanced FE modelling of bridges and buildings using OpenSees