In a comprehensive design approach, it should be recognized that damage to structures and facilities may result from different seismic effects. These effects can be classified as ‘Direct’ and ‘Indirect’ (or Consequential) as follows: Direct Effects:
- Ground failures (or instabilities due to ground failures)
Surface faulting surface or fault rupture)
Vibration of soil (or effects of seismic waves)
Ground cracking
Liquefaction
Ground lurching
Differential settlement
Lateral spreading
Landslides - Vibrations transmitted from the ground to the structure.
Indirect Effects (or Consequential Phenomena): (3) Tsunamis
(4) Seiches
(5) Landslides
(6) Floods
(7) Fires In Reference 3, most of these types of damage are defined. The seismic effect or damage that usually concerns the structural engineer, and which is taken into account by code seismic-resistant design provisions, is the vibration of the structure in response to ground shaking at its foundation. Although damage due to other effects may exceed that due to vibration, procedures for gauging the probability of these effects and for coping with them are outside the scope of the structural engineering discipline and so are usually not included in seismic-resistant codes. Nonetheless, the structural engineer should be aware of the different seismic hazards and should advise the client of potential damage involved in locating structures at certain sites. Thus the first step in the design procedure of a future structure should be the analysis of the suitability of the site selected with proper consideration for the potential of any one of the above types of damage. |
