The dynamic behavior of Submerged Floating Tunnels (SFTs or Archimedes Bridges) has caught the interest of this research group, in the past decade, with reference to different sources of excitation, namely earthquakes, sea waves and currents. Both structural and excitation models have been developed to the aim of capturing the essential features of the dynamic behavior of the SFTs under complex excitation mechanisms, i.e. 3D multiple-support seismic excitation or vortex induced vibration. With reference to seismic actions, special attention has been devoted, in recent times, to some aspects of structural and excitation models; first of all, it had been noted, in previous studies, that anchoring bars which are normally located at the tunnel ends usually undergo large stress concentration due to the oscillations of the tunnel in the transversal plane. These stresses can largely exceed the yield value: this aspect, if properly controlled, can be regarded as an option for dissipating part of the energy transferred to the structure by the seismic motion. In this light, inelastic behavior of the anchoring elements, which are slender bars with hollow section in the proposed design approach, has been recently introduced in the dynamical modeling of the SFT, allowing for a detailed study of the inelastic deformations imposed by extreme seismic actions. As a second improvement in the modeling approach, the hydrodynamic pressure due to the water-transmitted seismic vibration from the seabed (named as seaquake) is introduced in addition to the to the motion of the structural supports. The hydrodynamic excitation is derived from the velocity potential deduced from wave equation. Morison equation is then adopted to simulate the seaquake force on the moving tunnel body. The first results show how the seaquake mechanism can lead to a significant increase in the internal forces both in the tunnel and in the anchor bars, the effectiveness of the control system in the mitigation of dangerous structural responses and highlight the need of further investigations.

THE NON-LINEAR DYNAMIC RESPONSE OF SUBMERGED FLOATING TUNNELS TO EARTHQUAKE AND SEAQUAKE EXCITATION

PEROTTI, FEDERICO;SHI, CHUNXIA;DOMANESCHI, MARCO;MARTINELLI, LUCA
2013-01-01

Abstract

The dynamic behavior of Submerged Floating Tunnels (SFTs or Archimedes Bridges) has caught the interest of this research group, in the past decade, with reference to different sources of excitation, namely earthquakes, sea waves and currents. Both structural and excitation models have been developed to the aim of capturing the essential features of the dynamic behavior of the SFTs under complex excitation mechanisms, i.e. 3D multiple-support seismic excitation or vortex induced vibration. With reference to seismic actions, special attention has been devoted, in recent times, to some aspects of structural and excitation models; first of all, it had been noted, in previous studies, that anchoring bars which are normally located at the tunnel ends usually undergo large stress concentration due to the oscillations of the tunnel in the transversal plane. These stresses can largely exceed the yield value: this aspect, if properly controlled, can be regarded as an option for dissipating part of the energy transferred to the structure by the seismic motion. In this light, inelastic behavior of the anchoring elements, which are slender bars with hollow section in the proposed design approach, has been recently introduced in the dynamical modeling of the SFT, allowing for a detailed study of the inelastic deformations imposed by extreme seismic actions. As a second improvement in the modeling approach, the hydrodynamic pressure due to the water-transmitted seismic vibration from the seabed (named as seaquake) is introduced in addition to the to the motion of the structural supports. The hydrodynamic excitation is derived from the velocity potential deduced from wave equation. Morison equation is then adopted to simulate the seaquake force on the moving tunnel body. The first results show how the seaquake mechanism can lead to a significant increase in the internal forces both in the tunnel and in the anchor bars, the effectiveness of the control system in the mitigation of dangerous structural responses and highlight the need of further investigations.
2013
Strait Crossings 2013 Proceedings - STATENS VEGVESENS RAPPORTER Nr. 231
offshore structures; submerged floating tunnels; nonlinear behavior; multiple-support seismic excitation; hydrodynamic excitation (seaquake)
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11311/757642
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