Engineering Know-How: Lessons from Earthquakes and Rules for Seismic Design - Dynamic Behavior of Concrete and Seismic Engineering - page 340

states ( SLS ) that are concerned with the normal operation of the structure and its
elements, people's comfort and the appearance of the construction.
Calculation is far from the only design element in seismic situations, where
general design layouts are essential elements too.
Material fatigue - which will not be dealt with in this chapter - must also be
taken into account when designing construction works subject to important and
repeated dynamic loads, such as railway bridges and seaside works.
9.3.3.2. Application of Eurocode 8 (Part 1)
To be compliant with the Eurocode objectives defined in section 9.3.2, the
following limit states must be checked:
- ultimate limit states: verifying these involves non-collapse and other kinds of
structural failure that might endanger human lives;
- damage limitation states : these are associated with the appearance of damage
and correspond to conditions under the structure is not able to fulfill its duties any
more, while remaining stable.
A feature common to anti-seismic design standards is that verifications required
for specified levels are enough to demonstrate the strength of the construction work
with regard to all seismic events on intermediate levels. The methods do not
necessarily directly apply to intermediate levels. Forgetting this can lead to
erroneous interpretations.
9.3.3.3. Verifications
We need to verify that the structure has enough strength and ductility at the
ultimate limit state, and do this by taking second order effects into account. The
verification can be achieved by introducing acceptable incursion limits into the post-
elastic state. A technique for predicting post-elastic behavior involves applying a
dividing coefficient, called the behavior coefficient (sections 9.4.3.3 and 9.5),
determined by the overall behavior characteristics of the structure and constitutive
material, to the seismic actions calculated from a linear elastic hypothesis. The more
ductile the structure is and the better controlled its behavior, the higher the value of
this coefficient. Application involves dimensioning structures for strength values
lower than elastic.
We also need to verify the joint openings between two adjacent buildings or
between two blocks of a same building to ensure they are sufficient to avoid shocks.