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Summary In this paper, real‐time hybrid simulations (RTHSs) and shaking table tests (STTs) are described to assess the feasibility of using recycled rubber fibre‐reinforced bearings (FRBs) as base isolators of low‐cost buildings in developing countries. The RTHSs were run to predict the behaviour of a prototype‐scaled building under dynamic loading prior to carrying out STTs on the same structural model. Real‐time tests addressed a lack of knowledge regarding the seismic behaviour of FRBs as isolators for low‐rise buildings. They also underlined the feasibility of the shaking table experimental tests and addressed all the safety concerns. In this work, the outcomes of the two different testing procedures were compared. As result, the need to adopt STTs to validate base isolation technologies is questioned and, from the comparison, the advantages and limits of the two testing procedures are presented. Moreover, the acquired knowledge on the dynamic behaviour of recycled rubber bearings validates their use as isolators for seismic risk mitigation in earthquake‐prone regions of the world. Briefly, the objectives of this work can be listed as follows: (i) to provide validation of a newly constructed RTHS testing apparatus at the Department of Industrial Engineering of the University of Naples Federico II, Italy, (ii) to evaluate the effectiveness of recycled rubber FRBs as a low‐cost base isolation system for low‐rise structures against severe seismic events through dynamic testing and (iii) to compare, through tests on the same physical component, the RTHS and shaking table testing techniques. Copyright © 2014 John Wiley & Sons, Ltd.

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Summary The unscented Kalman filter (UKF) is often used for nonlinear system identification in civil engineering; nevertheless, the application of the UKF to highly nonlinear structures could not provide accurate results. In this paper, an improvement of the UKF algorithm has been adopted. This methodology can consider state constraints, and it can estimate the measurement noise covariance matrix. The results obtained adopting a modified UKF have been compared to the ones obtained using the UKF for parameter estimation of a single degree of freedom nonlinear hysteretic system. The second part of this work shows results of an experimental activity on a base‐isolated prototype structure. Both numerical and experimental results underline that the adopted algorithm produces better state estimation and parameter identification than the UKF, being capable of taking into account parameter boundaries. The adopted algorithm is more robust than the standard UKF in the case of measuring noise variation.

This paper presents an activity concerning the modelling and control of a system adopted to perform shear tests on seismic isolators. The test rig consists of a hydraulic actuation system that drives a sliding table mounted on linear bearings. The system is characterized by non-linearities such as hydraulic proportional valve dead zone and frictions. A non-linear model is derived and then employed for parameter identification procedure. The test rig needs a suitable controller able to guarantee the desired table displacement in presence of unknown reaction force of the device under test. The proposed approach consists of a feedforward control integrated with a feedback one. The feedforward control law takes the form of a non-linear inverse model of the system. In this way, it is possible to obtain the desired target without affecting the stability of the test rig. The feedback control has the function to compensate for tracking error due to the model uncertainties and the unknown isolator reaction force. Therefore, the feedback control is not required to compensate for the large non-linearities: in this manner, it is possible to obtain good tracking results without the increasing of the feedback control gain that would change the stability properties of the plant. Numerical simulations have been performed in order to evaluate the goodness of the designed control with and without the specimen under test. Experimental tests show that the controlled system simulations are able to predict the controller performance. The experimental results also confirm that the performance of the proposed controller fully satisfy the standards concerning the testing procedure of seismic isolators.

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