Civil Engineering Reference
In-Depth Information
d
, is determined in the
solution process. The dotted curve in Figure 3.24(b) also represents the yielding of the tension
steel.
Figure 3.24(b) shows that the ultimate rotation
Equation (3.153) can be calculated as soon as the depth ratio,
a
/
φ
u
d
decreases rapidly with increasing axial
compression,
N
n
/
drops to unity at the balanced point. In earthquake
design, therefore, columns are not designed to develop flexural hinges or to dissipate energy.
Flexural hinges should always be designed to occur in the beams of a frame, rather than in the
columns. This so-called strong columns-weak beams concept of frame design is fundamental
to the earthquake design of reinforced concrete structures.
N
o
. The ductility ratio
µ
