Constraint minimum variance unbiased estimator is improvised for simultaneous input and parameter estimation of the Bouc-Wen hysteretic system of a full-scale bridge pier. The essential structural properties in this case (i.e., bounded input and bounded output) are incorporated in the form of constraint conditions along with degradation and pinching effects. To demonstrate the efficiency of this algorithm, two different types of sigma points generation schemes (viz., unscented transformed points and cubature quadrature points) are presented here. First, the algorithm is validated using simulated response obtained from a single-bay single-storey reinforced concrete frame, whose hysteretic parameters are obtained by minimizing the error between the model and experimentally observed load-deformation characteristics. The rationale behind the use of experimentally observed hysteresis in simulation is to replicate the actual structure so that the realistic material behaviour is maintained. Once the algorithm is validated, its performance is further demonstrated using experimental results of a full-scale bridge pier, which is the main objective of this study. The numerical results presented in this paper clearly show the robustness of the proposed algorithm using unscented sigma points, which can identify both hysteretic properties and input excitation with sufficient level of accuracy.
This study quantifies the influence of strong ground motion duration (SGMD) of aftershocks on the cumulative damage caused to a RC frame structure. Understanding the effect of ground motion duration on cumulative damage and failure mechanisms will bring us one step closer to preventing future earthquake-induced collapses and can also aid in improving Building code. In order to study the effects of Duration, the other time-frequency characteristics i.e. amplitude and frequency content are kept similar. A realistic nonlinear numerical structure is modelled in SAP2000 in order to incorporate cyclic deterioration of strength and stiffness. Two sets of data are considered i.e. longer duration (>40sec) and shorter duration (<25 sec) and for each set of data cumulative damage are calculated using modified Park and Ang Damage Index. It is seen that in general longer duration data sequence causes more damage than shorter duration sequences because of longer cycles of loading.
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