Monitoring and Identification of Vibration Frequencies on a Portion of México City Metro Line 12

Abstract

The use of recursive subspace-based identification methods is analyzed in the estimation of the most significant vibration frequencies along an elevated railroad segment of México City Metro Line 12 using ambient vibration measurements recorded from 2012, when the line was opened, to 2018. Due to the railroad characteristics, the use of high-order models and the systematic tuning of the methods are required to achieve low uncertainty in frequency estimation. A frequency history is generated using these high-order models in order to check for variations along the seven years where important events took place: two low- and one high-intensity earthquakes, paving, and construction of sidewalks and planters around the sensor station. Results are consistent for all methods under analysis in the identified frequencies, suggesting that the system has preserved its structural health. To produce independent results, spectral analysis was performed showing that the associated frequency history is again consistent with that generated with recursive subspace-based identification methods. Overall, results indicate that these subspace methods are suitable for frequency monitoring in the studied system offering, in the case of recursive N4SID, important advantages in terms of low computational cost, real-time implementation, and smaller uncertainty.

The Tracking of Modal Parameters for a Reinforced Concrete Building During Low-Medium Intensity Earthquakes

“…The recurrent algorithms in the literature, for the identification of MIMO systems are the Multivariable Output Error State Space (MOESP) [11] and the numerical algorithm for Subspace State Space System IDentification (N4SID) [12]. Many works can be found in which above algorithms have been successfully used for dynamic identification of full-scale case studies during seismic events [13,14,15,16]. The first step in using the subspace identification algorithms is to write the dynamical system in the state space, through a state equation (Eq.…”

Structural monitoring of a curve portion of an elevated railroad including the effects of the 19 September 2017 earthquake

“…The N4SID method was tuned similarly; order models from 60 to 100 with an increase of ten were identified to later remove the spurious modes. At the end, average frequency and damping values were calculated recursively in 1-s intervals (Garcı´a-Illescas et al, 2019).…”

“…Because of the system characteristics and the limited signals, one input one output, stable eigenvalues were observed in high-order models. Order models from 60 to 100, intervals of ten, were identified; as the order model increases, the accuracy in the identified model is improved (García-Illescas et al, 2019). A common problem by using subspace identification methods is the presence of spurious modes that appear either by noise sources or by nonlinearities in the system (Marchesiello et al, 2016).…”

Improving the performance of tuned mass dampers by considering geometric nonlinear effects in an integrated identification-control approach

“…These parameters can be classified as structural parameters, vibration signals, energy, and structural responses [14]. Numerous studies have been conducted on different methods of identification and health monitoring which can be divided into offline [15][16][17][18] and online [19][20][21][22] methods from one point of view. The virtual synchronization method (VSM) is an innovative approach within online system identification that allows for real-time identification of the structure's unknown parameters through the formation of a virtual system that emulates the actual structure.…”