Challenges for the Next Generation of Seismic Codes - Earthquake Engineering for Structural Design - page 525

qfactor

High

5.0

Medium

3.5

Reduced Reduced

2.0

0.0

Thrust Strike-slip Conver- Crust

gence fracture

Interplate Intraplate Intraslab

Figure 10.43 Proposed q factors in function of earthquake type

Consequently, reduced and medium values are proposed for the q factor. In case of
crustal intraplate, for convergence sources, where both thrust and strike-slip
earthquakes can occur, a medium reduction factor is proposed. For crust fracture
with 1-2 pulses and very short duration, a reduced q factor is proposed. Contrary, a
higher value for the reduction factor is proposed for intraslab earthquakes,
characterized by a large number of cycles and long duration. Consequently, the
design philosophy concerning strength and ductility must be different in function
of the earthquake type (Fig. 10.44).
It is desirable to design structures in such a way that they behave in a known
and predictable manner. Generally, the ultimate response can be as follows:
- Due to the reduced ductility and low q factor values (the case of thrust and

crust fracture earthquakes), the structure must develop a large strength. The
main design problem refers to the protection of structural members against
brittle fracture produced by the first or second cycle due to the effect of strain-
rate.