Abstract
This paper presents a simplified model using coupled Bernoulli and shear beams supported by Winkler-type springs for system identification of tunnels subjected to earthquake-induced ground motions. The model formulation is introduced and closed-form solutions to the modal characteristic equation and mode shapes are derived. The latter are verified against the results of numerical models. Then, the system identification algorithm is presented, showcasing its ability to recover model parameters when recorded acceleration time histories along the tunnel are compromised by noise and sensor locations are varied. The presented framework can be used to initially and, simply, recover tunnel response when monitoring data is available, or to plan for monitoring campaigns in newly constructed or existing tunnels.
Highlights
Underground structures are less susceptible to earthquake-induced damage as displacements and total accelerations increase per the free surface (Towhata, 2008)
Deployment of structural health monitoring systems (SHMS) can be beneficial in terms of enhancing the seismic resilience of tunnels for the following reasons (Ogie et al, 2017): (a) they allow for assessment of accelerations, displacements and strains in tunnel linings in real time, ensuring that the desired performance levels under serviceability conditions and in the aftermath of extreme seismic events are met; (b) they facilitate implementation of adaptive management by learning from the response observed in previous occurrences of disruptive seismic excitations; and (c) they can help to take timely action to protect roadway users from life threatening conditions
The vertical component of two ground motions were selected to excite the model at its base: the Hulverstone Drive Pumping Station (HDPS) record, obtained within the city of Christchurch, during its 2011 Mw 6.2 earthquake, and the CHY080 record obtained during the 1999 Mw 7.6 Chi-Chi Taiwan earthquake mainshock
Summary
Underground structures are less susceptible to earthquake-induced damage as displacements and total accelerations increase per the free surface (Towhata, 2008) Due to their significant construction cost, tunnels may become bottlenecks in transportation routes in case their functionality is even slightly impaired by these events, leading to large downtime, direct and indirect losses. Detailed numerical models (Hatzigeorgiou and Beskos, 2010; Wu and Gao, 2013; Yu et al, 2016a) can be used for this purpose, but convergence to finding a proper solution can be time consuming (if not impossible) due to the large number of parameters involved Another approach to parametric system identification is the use of simplified models. Applying the above boundary conditions to Equation (7) defines the following system of equations in matrix form:
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