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SUMMARY:Dynamic Soil-Structure Interaction of Tunnels - Ulas  Cilingir\, C
 UED
DTSTART:20090515T153000Z
DTEND:20090515T163000Z
UID:TALK17753@talks.cam.ac.uk
CONTACT:Zelda Stuck
DESCRIPTION:Underground structures and tunnels in urban areas constitute a
 n important part of the transportation infrastructure. In seismic regions 
 these structures are under earthquake induced risks. By their nature\, the
 se structures extend through very long distances. Their geometry\, structu
 ral properties and also the surrounding medium may change throughout their
  alignment. An understanding of the effects of all these factors on the se
 ismic behavior of underground structures  is essential to cope with the pr
 oblems encountered after a possible earthquake event.\n\nEffects of the fl
 exibility\, embedment depth and input motion on the seismic behaviour of t
 he underground structures are not fully understood. Widely used design met
 hodologies often use simplifications and assumptions which do not represen
 t realistic site conditions and the nature of the dynamic loads applied on
  the tunnels. The effects of inertia and non-linearity of the surrounding 
 medium are often neglected. \nMore complex numerical methods exist\, but t
 heir predictions cannot be verified due to lack of experimental data.\n\nT
 his study is based on dynamic centrifuge experiments which were carried ou
 t on model tunnels with different shape\, flexibility and embedment depth.
  The emphasis is given on the effects of the upwards propagating transvers
 e shear waves in dry\, loose sand. Accelerations around the tunnel\, earth
  pressures on the lining were measured. Particle Image Velocimetry (PIV) a
 nalyses were carried out on the digital images recorded by a fast camera d
 uring the centrifuge flights. Complementary dynamic Finite Element (FE) an
 alyses were also conducted using general finite element code ABAQUS.\n\nAn
 alysis of the results revealed that the shape\, flexibility and the depth 
 of the tunnel have pronounced effects on the dynamic behaviour of the tunn
 els and effects the accelerations around the tunnel\, earth pressures and 
 the mode of deformation of the tunnel lining. It has been shown that the c
 urrent analytical methods fall short in explaining the complex nature of t
 he dynamic behaviour of the underground structures.\n\n
LOCATION:Engineering Department - LR6
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