Interpretation of Real-Time Hybrid Simulation as Neutral and Retarded Delay Systems for Its Stability Analysis

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Stability of real time hybrid simulation (RTHS) has attracted considerable attention since actuator delay would deviate experiment results or even destabilize the real-time test. Previous studies have extensively investigated stability of RTHS for linear systems, while stability of RTHS for nonlinear system remains unclear. This study introduces the Takagi-Sugeno (T-S) method to describe the nonlinear behavior in a piecewise linear way, then investigates the stability of nonlinear system with time delay through the Lyapunov-Krasovskii (L-K) theory.Such approach successfully solves the stability problem of RTHS with coupled bilinear-hysteresis substructure and actuator delay, and proposes a stability criterion in the form of linear matrix inequality (LMI). It proves that the stability of RTHS is determined by the most unfavorable state of nonlinear system. In the SDOF case with stiffness softening, the initial elastic state is the most unfavorable; while for the MDOF case with multiple delays, the stability is determined by the overlap part of stable region of each nonlinear state. The computational simulation and experimental results show that the difference between linear-and nonlinear hysteretic system with time delay is that when instability occurs, latter could remain energy balanced since the time-delay energy is dissipated by hysteresis behavior, while energy accumulates in the former leading to unbounded responses. The proposed approach provides a potential tool for experimental design of RTHS before the test, the time-delay control during the test and error evaluation after the test.

Section: Test Resultsmentioning

confidence: 99%

Section: Lmi Stability Criterionmentioning

confidence: 99%

Section: Lmi Stability Criterionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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confidence: 99%

See 3 more Smart Citations

Stability analysis of real time hybrid simulation under coupled actuator delay and nonlinear behavior

Huang

Chen

et al. 2022

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Integrating real‐time hybrid simulation with multi‐fidelity Monte Carlo predictor for seismic fragility assessment

Gao,

Chen,

Peng

et al. 2023

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Seismic fragility evaluates the performance of a structure regarding to its capability to withstand earthquake loads by describing the exceedance probability for selected engineering demand parameters. High‐fidelity (HF) models are essential for simulation‐based techniques to obtain accurate fragility assessment in the presence of uncertainties. Dynamic structural behavior however is often difficult to replicate realistically through numerical simulation, especially when parts of the structure are difficult for accurate modeling due to their inherent complex nonlinearity. This study presents the integration of real‐time hybrid simulation (RTHS) with multi‐fidelity Monte Carlo (MFMC) predictor for seismic fragility analysis. RTHS combines physical testing of experimental substructures and numerical modeling of analytical substructures thus presenting a cyber‐physical alternative for HF seismic performance evaluation. The MFMC predictor provides an optimized allocation algorithm that makes full use of data from both HF and low‐fidelity (LF) models to achieve unbiased estimation for response quantities of interests. Experimentally expensive HF data from RTHS is thus integrated with computationally cheap simulation of LF numerical models through MFMC to facilitate seismic fragility analysis. A two‐story steel moment resisting frame (MRF) with self‐centering viscous dampers (SC‐VDs) is utilized to demonstrate the effectiveness and efficiency of the proposed method. Computational simulation is first performed to numerically verify the feasibility of the proposed method for the MRF subjected to non‐stationary stochastic ground motions. RTHS is then conducted experimentally as HF model and integrated with linear elastic LF models through MFMC for fragility analysis of the MRF equipped with SC‐VDs. Both computational and experimental analysis demonstrate that the proposed method provides a promising technique for seismic fragility assessment especially when accurate modeling is not available due to complex structural behavior.

A real‐time hybrid simulation framework for reliability‐based design optimization of structures subjected to pulse‐like ground motions

Peng,

Guo,

Chen

et al. 2024

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Reliability‐based design optimization (RBDO) traditionally relies primarily on high‐fidelity and computationally expensive simulations to search for and evaluate design solutions. However, significant disparities could emerge for complex nonlinear behavior that are challenging for numerical modeling. In contrast to mitigating the impact of inaccurate numerical modeling through optimization algorithms, laboratory experiments realistically capture the complex nonlinear behavior of structures or their components. Real‐time hybrid simulation (RTHS) is widely considered as an efficient and cost‐effective technique for integrating numerical modeling with experimental testing for structural response evaluation. This study proposes an innovative framework that utilizes RTHS for the performance assessment of candidate designs to enable RBDO of structures subjected to pulse‐like ground motions. RTHS tests are conducted to physically evaluate structural responses through realistically replicating complex nonlinear behavior of experimental substructures. This study introduces a novel penalty function‐based efficient global optimization (P‐EGO) method to minimize the required number of laboratory tests through surrogating the response quantities of interest derived from RTHS. The proposed framework is experimentally evaluated for design optimization of a two‐story four‐bay steel moment‐resisting frame with self‐centering viscous dampers subjected to pulse‐like ground motions. The results demonstrate innovative application of RTHS in dynamic optimal design to account for uncertainties. It offers an effective and efficient alternative for traditional RBDO through pure computational simulation, particularly when structural components pose challenges for numerical modeling.