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Hybrid Simulation of Structural Collapse

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Hybrid Simulation of Structural Collapse Andreas Schellenberg, Tony Yang and Bozidar Stojadinovic University of California, Berkeley Ken Elwood University of British ... – PowerPoint PPT presentation

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Title: Hybrid Simulation of Structural Collapse


1
Hybrid Simulationof Structural Collapse
  • Andreas Schellenberg, Tony Yang and Bozidar
    Stojadinovic
  • University of California, Berkeley
  • Ken Elwood
  • University of British Columbia

2
Hybrid Simulation
  • Hybrid simulation is an experimentally based
    testing method for investigating the response of
    a structure to dynamic excitation using a hybrid
    model
  • A hybrid model is an assemblage of one or more
    physical and one or more numerical, consistently
    scaled, partitions of a structure
  • The equations of motion of a hybrid model under
    dynamic excitation are solved during a hybrid
    simulation test

3
Response Simulation with Second-Order Effects
  • Dynamic loading excites a structure
  • Inertia
  • Energy dissipation (damping)
  • Resistance
  • Second order effects are included in the
    resistance of the structure
  • However, they may be simulated in the computer

4
Outline of Talk
  1. Second-Order Effects and Structural Collapse
  2. Implementation in OpenSees and OpenFresco
  3. Structural Collapse of Portal-Frame Example
  4. Summary and Conclusions

5
Second-Order Effects
  • Definition effect of loads on the
    deformed geometry
  • P-D change of global geometry
  • P-d change of member geometry
  • P-MM interaction (section level) also local
    buckling

6
Simulation to Structural Collapse
  • Second order effects are essential for simulating
    collapse of structures that displace
    substantially
  • Typically civil structures are tested using
    shaking tables
  • However, structural collapse is difficult and
    expensive to investigate using shaking table
    tests

7
Advantages of using Hybrid Simulation
  • Gravity loads and resulting geometric
    nonlinearities are modeled analytically
  • Therefore, no complex active or passive gravity
    load setups are necessary
  • Actuator movements will limit displacements
  • Thus, there is no need to protect expensive test
    equipment from specimen impact
  • Only critical, collapse-sensitive elements of a
    structure need to be physically modeled

8
Corotational Formulation (2D)
9
Implementation in a Hybrid Model
  • Provide the geometric transformations such that
    the effect of axial loads is accounted for in the
    computer part of the hybrid model
  • Physical part of the model
  • Model material and cross-section level response
  • Computer part of the model
  • Model the second-order effect of axial load
  • Provide the rest of the structure

10
Implementation at nees_at_berkeley
  • Using
  • OpenSees to provide the nonlinear geometric
    transformation facilities
  • OpenFresco to provide the hybrid simulation
    framework
  • OpenSees Navigator to graphically build the
    model, run the test and post-process the hybrid
    simulation results

11
Geometric Transformations
Experimental BeamColumn
Global System
Basic System A (simply supported beam)
Basic System B (cantilever beam)
geometric transformation in OpenSees (Linear,
PDelta, Corotational)
12
OpenFresco Components
local deployment
FE-Software
OpenFresco
interfaces to the FE-Software, stores data and
facilitates distributed testing
Experimental Site
transforms between the experimental element
degrees of freedom and the actuator degrees of
freedom (linear vs. non-linear transformations)
Experimental Setup
interfaces to the different control and data
acquisition systems in the laboratories
Experimental Control
Control System in Laboratory
13
OpenFresco Components
network deployment
FE-Software
OpenFresco
NTCPExpSite
ShadowExpSite
NTCPExpSite
ShadowExpSite
Exp.Setup
Exp.Setup
TCP/IP
TCP/IP
NTCP
NTCP
OpenFresco
OpenFresco
NTCP Server
NTCP Server
ActorExpSite
ActorExpSite
Exp.Setup
Control Plugin with transformation
Control Plugin without tranformation
Exp.Control
Exp.Control
Control System in Laboratory
Control System in Laboratory
Control System in Laboratory
Control System in Laboratory
14
OpenSees Navigator User Interface
15
OpenSees Navigator User Interface
16
OpenSees Navigator User Interface
17
Example Portal Frame Test
  • Properties of Model
  • num. DOF 8 (2 with mass)
  • Period T1 0.291 sec
  • Damping z1 0.02
  • P 50 of fPn
  • Crd-Trans P-Delta, Corotational
  • ExpElements EEBeamColumn2d
  • ExpSetups ESOneActuator
  • ExpControl ECxPCtarget
  • SACNF01 pga 0.755g

18
Response Animation w/o Gravity Load
19
Response Animation with Gravity Load
20
Response Comparison Global Level
21
Response Comparison Element Level
22
Findings
  • Benefits
  • Second-order effects can be simulated without
    applying the axial force on the physical specimen
  • The specimens and test setups are less expensive
  • The physical setups are protected from falling
    structural elements
  • Shortcomings
  • Interaction of axial force and element resistance
    at the local level is not accounted for properly
    (local buckling, P-MM interaction)
  • Rate effects are not accounted for

23
Conclusions
  • Second-order effects can be effectively simulated
    using a hybrid model
  • The effect of axial load can be modeled in the
    computer using appropriate geometric
    transformations
  • Collapse of structural systems due to
    second-order effects can, thus, be simulated
  • OpenSees and OpenFresco implementation has been
    successfully demonstrated

24
Future Work
  • Conduct large-scale simulations
  • Conduct simulations where the axial load will be
    physically applied on the specimen

25
Download OpenSees Navigator
http//peer.berkeley.edu/OpenSeesNavigator
26
Thank you!
  • Development and operation of the nees_at_berkeley
    equipment site is sponsored by NSF
  • Special thanks to Dr. Eiji Kohama for all the
    help with the portal frame tests
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