SUMMARYHybrid simulations that combine numerical computations and physical experiment represent an effective method of evaluating the dynamic response of structures. However, it is sometimes impossible to take all the uncertain or nonlinear parts of the structure as the physical substructure. Thus, the modeling errors of the numerical part can raise concerns. One method of solving this problem is to update the numerical model by estimating its parameters from experimental data online. In this paper, an online model updating method for the hybrid simulation of frame structures is proposed to reduce the errors of nonlinear modeling of numerical substructures. To obtain acceptable accuracy with acceptable extra computation efforts as a result of model parameter estimation, the sectional constitutive model is adopted, therein considering axial-force and bending-moment coupling; moreover, the unscented Kalman filter is used for parameter estimation of the sectional model. The effectiveness of the sectional model updating with the unscented Kalman filter is validated via numerical analyses and actual hybrid tests on a full-scale steel frame structure, with one column as the experimental substructure loaded by three actuators to guarantee the consistency of the boundary conditions.
Summary Online model updating in hybrid simulation (HS) can represent an effective technique to reduce modeling errors of parts numerically simulated, that is, numerical substructures, especially when only a few critical components of a large system can be tested, that is, physical substructures. As a result, in an enhanced HS with online model updating, parameters of constitutive relationship can be identified based on experimental data provided by physical substructures and updated in numerical substructures. This paper proposes a novel method to identify constitutive parameters of concrete laws with unscented Kalman filter (UKF). In order to implement UKF, parts of the source codes of the OpenSEES software were modified to compute estimated measurements. Prior to experimental HS, a parametric study of UKF constitutive law parameters was conducted. As a result, the effectiveness of the UKF combined with OpenSEES was validated through numerical simulations, a monotonic loading test on a concrete column and real‐time HSs of a reinforced concrete frame run with both standard and model‐updating techniques based on UKF.
Summary Hybrid simulation is a powerful and cost‐effective simulation technique to evaluate structural dynamic performance. However, it is sometimes rather difficult to guarantee all the boundaries on the physical substructures, especially when the boundary conditions are very complex, due to limited laboratory resources. Lacking of boundary conditions is bound to change the stress state of the structure and eventually result in an inaccurate evaluation of structural performance. A model updating‐based online numerical simulation method is proposed in this paper to tackle the problem of incomplete boundary conditions. In the proposed method, 2 sets of finite element models with the same constitutive model are set up for the overall analysis of the whole structure and the constitutive model parameter estimation of the physical substructure, respectively. The boundary conditions are naturally satisfied because the response is calculated from the overall structural model, and the accuracy is improved as the material constitutive parameters are updated. The effectiveness of the proposed method is validated via numerical simulations and actual hybrid tests on a RC frame structure, and the results show that the negative effect of incomplete boundary conditions is almost eliminated and the accuracy of hybrid simulation is very much improved.
Hybrid (numerical/physical) simulation (HS) with both numerical (NS) and physical substructures (PS) is proposed to investigate the seismic behavior of a complex reinforced concrete (RC) rigid frame bridge with tall piers characterized by thin-wall hollow sections. The HS primarily intends to increase the knowledge on the seismic performance of RC tall piers with thin-walled hollow sections. In order to reduce modeling errors of parts numerically simulated, i.e. NSs, we propose a novel hybrid simulation with online updating (UHS) of concrete constitutive parameters provided by PS data. In particular, the unscented Kalman filter (UKF) embedded in the OpenSees software is proposed for parameter identification. The online updating UHS with this identification method is numerically validated on a one-bay one-story frame. Then, applications of UHS are applied to a RC bridge. Results show that the proposed parameter identification and the relevant HS with online updating exhibit both a favorable performance and robustness with respect to standard techniques (SHS) without model updating. With regard to the seismic response of the simulated bridge, both the damage evolution and the failure modes of the PS are presented. Though both flexural and shear behavior characterize PS failure, an unfavorable shear failure was followed by stirrup fracture.
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