“…Wang et al [27] propose an adaptive observer for structures whose design employs the Hilbert transform. Moreover, Dion et al [28] present an adaptive observer that estimates the natural frequencies of structures and that is based on the Optimized Spectral Kurtosis and the Extended Kalman Filter (EKF); this adaptive observer tracks and removes sinusoidal components, which pollute the acceleration measurements and come from engines in operation and from spurious harmonic components of the electric power supply. Finally, references [29][30][31] propose Sequential Monte Carlo (SMC) methods that are robust against measurement noise, have gained popularity due to their superiority over the EKF, can simultaneously estimate the state and parameters of buildings, and require a discrete-time model of this system; with the SMC methods, the state and parameter identification consist in the computation of a non-Gaussian probability density function pðx k ; θjD k Þ, where x k is the state, θ contains the parameters of the structure, and D k is a set that contains the measurements available up to time instant k. It is worth mentioning that most of the references consider the presence of measurement noise, but none of them take into account offsets in the acceleration measurements.…”