Advances in Seismic Design Methodologies - Earthquake Engineering for Structural Design - page 424

424 Earthquake Engineering for Structural Design

structure experiences a loss in stiffness. Using the push-over analysis, a characteristic
non-linear force-displacement relationship can be determined. There are two different
approaches in push-over analysis: traditional and adaptive (modal) procedures.
Traditional push-over procedure. The analysis can be described as applying lateral
loads in invariant pattern (pattern remain constant during the increasing loads) (Fig.
9.25a), which approximately represents the relative inertial forces generated at each
floor level and pushing the structure under monotonically increasing lateral loads.
Basically, a push-over analysis is a series of incremental static analysis carried out to
develop the capacity curve of the building from the elastic until the collapse state (Fig.
9.25b).This procedure provides a shear versus displacement relationship and indicates
the inelastic limit as well as lateral capacity of the structure until collapse under this
constant pattern loads. So, the load distribution for the push-over analysis, in function
of the presumed main vibration modes and ground motions, plays a crucial role in this
procedure. Generally, constant, triangular or parabolic distributions are the most used
patterns.

Loaddistribution Control node

TriangularConstant Base shear

(a)

Figure 9.25 (continues)