Revised description of seismic action in the next Eurocode 8

Pierre Labbé
Ecole Spéciale des Travaux Publics, Cachan, France

The purpose of this theme lecture is to present main changes introduced by CEN-TC250-SC8 concerning seismic action in the next revision of Eurocode 8, consisting principally of:

  • introducing the concept of seismic action class in place of seismicity level;
  • anchoring the standard spectrum by its plateau value, Salpha, and its value at 1 s vibration period, Sbeta, instead of the PGA;
  • introducing, in an informative annex, two European hazard maps, one for Salpha, and one for Sbeta, both defined for 475 years return period, based on the ESHM20 hazard model;
  • revising the site categorization by making it controlled by bed rock depth in addition to shear wave velocity;
  • introducing new site amplification factors based on this site categorisation and dependent on input motion level;
  • introducing a new spatial model of the seismic action for bridges;
  • providing miscellaneous specifications on conventional values of magnitude and strong motion duration, dependence of spectra to damping, modal combination rules.