Engineering Know-How: Lessons from Earthquakes and Rules for Seismic Design - Dynamic Behavior of Concrete and Seismic Engineering - page 331

Figure 9.6. Rupture of a column due to buckling
In Figure 9.6, failure has occurred because of the instability of the column:
combined bending and extra normal forces due to the vertical component of an
earthquake have crushed the concrete.
Figure 9.7 shows a silo after being subjected to a high horizontal acceleration.
Plastic hinges appeared at both ends of the columns, where the bending moments
were highest. In this case, the behavior of both hinges is quite different, due to
reinforcement differences. In the lower area, regular and tightly spaced frames have
confined the concrete within a “cage”, allowing strong plastic rotation (obvious in
the photograph) and holding the longitudinal reinforcements together, preserving the
limit moment during cycles. It should also be noted that the frames were well-
anchored, and consequently did not get torn down by the increased confinement
pressure.
In the upper part of this plate, the existence of smooth construction joints,
together with insufficient longitudinal reinforcements joining the section, generated
failure even before the plastic hinge had been able to form.