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Hybrid Simulation of Structural Collapse

Hybrid Simulation of Structural Collapse. Andreas Schellenberg , Tony Yang, Stephen Mahin and Boza Stojadinovic. Department of Civil and Environmental Engineering University of California, Berkeley. Motivation. Outline of Presentation.

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Hybrid Simulation of Structural Collapse

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  1. Hybrid Simulation of Structural Collapse Andreas Schellenberg, Tony Yang, Stephen Mahin and Boza Stojadinovic Department of Civil and Environmental Engineering University of California, Berkeley

  2. Motivation

  3. Outline of Presentation • Hybrid Simulation and OpenFresco middleware • Second-Order Effects and Structural Collapse • Implementation in OpenSees and OpenFresco • Structural Collapse of Portal-Frame • Summary and Conclusions

  4. Advantages: Loading (RHS) is defined analytically Dynamic testing of full-scale specimens withfewer restrictions on size, weight and strength Quasi-static testing equipment sufficient Geographically distributed for testingexceeding the capacity of one lab Incorporate geometric nonlinearities into analytical portion of hybrid model Hybrid Simulation • Dynamic Loading: • Seismic • Wind • Blast/Impact • Wave • Traffic • Static Loading: • Gravity • Prestress analytical model of structural energy dissipation and inertia physical model of structural resistance analytically add nonlinear geometric effects to measured resisting forces

  5. Hybrid Simulation • Model the well understood parts of a structure in a finite element program on one or more computers, including nonlinearity, multi-support excitation and soil-structure interaction • Leave the construction and testing of the highly nonlinear and/or numerically hard to model parts of the structure in one or more laboratories • Can be considered as a conventional finite element analysis where physical models of some portions of the structure are embedded in the numerical model

  6. Proper numerical model uncertain NUMERICAL ELEMENT 1 NUMERICAL ELEMENT 3 NUMERICAL ELEMENT 2 ? Implementation Strategy • Embed test specimen(s) in an existing computational framework of users choice ADMINISTRATIVE FUNCTIONS RECORDERS COMMUNICATION Typical features of an analysis framework NODAL GEOMETRY BOUNDARY CONDITIONS MASS AND DAMPING PROPERTIES LOADING ELEMENT TYPES AND LOCATIONS SOLUTION METHODS ELEMENT PROPERTIES STATE DETERMINATION

  7. NUMERICAL ELEMENT 1 NUMERICAL ELEMENT 2 OpenFresco OpenFresco LABORATORY CONTROLLERS AND DAQS Laboratory Implementation Strategy • Embed test specimen(s) in an existing computational framework of users choice ADMINISTRATIVE FUNCTIONS RECORDERS COMMUNICATION Typical features of an analysis framework NODAL GEOMETRY BOUNDARY CONDITIONS MASS AND DAMPING PROPERTIES LOADING ELEMENT TYPES AND LOCATIONS SOLUTION METHODS ELEMENT PROPERTIES Define element as an “Experimental Element” STATE DETERMINATION EXPERIMENTAL ELEMENT 1

  8. Simulation of Structural Collapse • On shaking tables, simulation of collapse is dangerous and expensive • In hybrid simulations • Gravity loads and resulting geometric nonlinearities can be modeled analytically • Therefore, no complex active or passive gravity load setups are necessary • Actuator movements will limit displacements during collapse (safety) • 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

  9. Second-Order Effects • Definition: effect of loads on the deformed geometry (satisfy equilibrium in deformed configuration) • P-Δ: change of global geometry (structural level) • P-δ: change of member geometry (element level) • P-M, P-V interaction (section level) also local buckling

  10. Implementation in a Hybrid Model • Physical portion of the model: • Test material and cross-section level response • Analytical portion of the model: • Apply the gravity and/or prestress loads • Provide the geometric transformations such that the second-order effects due to axial loads are accounted for • Model the rest of the structure

  11. Geometric Transformations

  12. Structural Collapse of Portal Frame • Crd-Trans: P-Delta, Corotational • ExpElements: EEBeamColumn2d • ExpSetups: ESOneActuator • ExpControl: ECxPCtarget • SACNF01: pga = 0.906g • Properties of Model: • NDOF = 8(2 with mass) • Period: T1 = 0.49 sec • Damping: ζ1 = 0.05 • P = 50% of φPn

  13. OpenSees/OpenFresco Details OpenSees Finite Element Model OpenFresco Middleware xPC-Target real-time Predictor-Corrector MTS 493 real-time Controller Physical Specimen in μNEES Lab

  14. Hybrid Simulations Without Gravity Load With Gravity Load

  15. Response Comparison: Global Level

  16. Response Comparison: Actuator Level

  17. Conclusions • 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 components • Shortcomings: • Interaction of axial force and element resistance at the local level is not yet accounted for (local buckling, P-M interaction) • Rate effects are not accounted for

  18. Questions?Thank you! http://openfresco.neesforge.nees.org The development of OpenFresco has been sponsored in parts by the National Science Foundation through grants from the NEES Consortium, Inc.

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