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SUMMARY:Earthquake engineering of nonstandard concrete structures: from th
 e assessment of spatial variability of earthquake signals to numerical mod
 elling of structural response
DTSTART:20161216T121500
DTEND:20161216T131500
DTSTAMP:20260503T144620Z
UID:5899d0b473049064a78040aaf6bf55d810325752d6a4fa06d5e08077
CATEGORIES:Conferences - Seminars
DESCRIPTION:Prof. Dr Frédéric Dufour\, Professor at 3SR laboratory and V
 ice President for research of Grenoble Institute of Technology\, Grenoble\
 , France\n\nOver the last 30 to 40 years\, modern design codes have been d
 eveloped worldwide to increase the safety of civil engineering structures 
 against an earthquake. For practical/economic reasons they mainly focus on
  classical structures to be built with restrictive hypothesis to allow sim
 ple engineering analysis. However\, historical monuments and large structu
 res for energy production (dams\, nuclear power plants) need a specific at
 tention of the scientific community.\nLarge structures for energy producti
 on have a huge interfacial surface with the ground. Therefore\, the hypoth
 esis of having a homogeneous loading must be questioned. Several  sensor 
 networks have been set in the world to analyze the amplitude and phase cha
 nges in space due to complex wave propagation in the underground. More rec
 ently\, a dam has been instrumented with about 20 velocimeters to measure 
 the spatial variability both under ambient noise and seismic events. The e
 ffect of topography on the phase and amplitude heterogeneities is analyzed
  with the help of spectral element models. The objective is to better iden
 tify the real loading felt by large structures and to identify whether the
  spatial variability is more or less critical for the structural safety.\n
 Besides\, for ancient/historical structures classical engineering methods 
 are not valid. Thus\, one needs to use modern finite element codes to asse
 ss the earthquake safety of such structures. Dynamic analyses have the pot
 ential to evaluate accurately local information (damage\, crack opening\, 
 rebar yielding\, etc.) although the computational time may be a drawback. 
 Therefore\, simplified numerical methods may be used for specific structur
 es. For instance\, the number of degrees of freedom of the model can large
 ly be reduced by applying beam kinematic for some structural elements. Thi
 s yields to the development of multifiber beam finite elements. Recently w
 arping has been added to those models to account for shear deformation in 
 the damage of concrete and yielding of rebars.\nFinally\, for the purpose 
 of a probabilistic risk analysis in engineering design\, one must rely on 
 an efficient intensity measure to estimate the structural response. For in
 stance\, the well-known PGA accounts only for the signal measure without t
 aking into account the modal analysis of the structure. Thus\, it cannot b
 e reliable for any structures since it does not account for resonance. Bes
 ides\, by definition the spectral acceleration (SPa) is the best intensity
  measure for a single degree of freedom system with a linear behavior. How
 ever\, real structures may undergo nonlinear behavior under intense earthq
 uake. Recently\, a new intensity measure has been developed accounting for
  the fundamental frequency of the structure and arbitrarily its reduction 
 upon structural damage. This IM called ASA40 has been proved to be simple 
 and efficient\, although in some specific case a time-frequency analysis r
 emain necessary to evaluate structural damage.\n\nBio : Prof. Frédéric D
 ufour obtained his PhD from the University of Nantes and Ecole Centrale of
  Nantes in 2002. He is now professor at Grenoble Institute of Technology i
 n the 3SR laboratory and Vice President for Research of the Grenoble Insti
 tute of Technology. He is the head of the PERENITI Chair funded by EDF on 
 the reliability of large structures. His research interests comprise the n
 umerical modelling of complex fluids and the modelling of concrete structu
 res with non-local approaches. Prof Dufour is the co-author of about 30 pe
 er review journal papers with a h-index of 12 and 400 citations.
LOCATION:GCA331 http://plan.epfl.ch/?lang=fr&room=GCA331
STATUS:CONFIRMED
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