criteria for primary elements that exhibit this
beams and columns in reinforced concrete frames are
behavior are typically within the elastic or plastic
typical
examples
of
force-controlled
elements.
ranges, depending on the performance level.
Acceptance criteria for primary and secondary
Acceptance criteria for secondary elements can be
components exhibiting this behavior are always
within any of the ranges.
Primary component
within the elastic range.
actions exhibiting this behavior are considered
deformation-controlled if the plastic range is
(d) Figure 6-2 shows an idealized
sufficiently large (b $ 2a); otherwise, they are
force versus deformation curve that is used
considered force-controlled.
Structural steel and
throughout this procedure to specify acceptance
reinforced concrete members in flexural response are
criteria for deformation-controlled components and
typical examples of deformation-controlled elements.
element actions for any of the four basic types of
Secondary
component
actions
exhibiting
this
materials. Linear response is depicted between point
behavior are typically considered to be deformation-
A (unloaded component) and an effective yield point
controlled.
B.
The slope from B to C is typically a small
percentage (0 to 10 percent) of the elastic slope, and
(b)
The
Type
2
curve
is
is included to represent phenomena such as strain
representative of semi-ductile behavior.
It is
hardening. C has an ordinate that represents the
characterized by an elastic range and a plastic range,
strength of the component, and an abscissa value
followed by a rapid and complete loss of strength if
equal to the deformation at which significant
the
behavior
is
categorized
as
deformation-
strength degradation begins (line CD). Beyond point
controlled.
Otherwise it is categorized as force-
D, the component responds with substantially
controlled.
A reinforced concrete wall in shear
reduced strength to point E. At deformations greater
response is a typical example of a deformation-
than point E, the component strength is essentially
zero. In Figure 6-1, QCE is the expected strength of a
controlled element with semi-ductile behavior.
Acceptance criteria for primary and secondary
component or element at the deformation level under
components exhibiting this behavior will be within
consideration for deformation-controlled actions.
the elastic or plastic ranges, depending on the
Expected strength is defined as the mean value of
performance level.
resistance at the deformation level anticipated, and
includes phenomena such as strain hardening and
plastic section development. QCL is the lower-bound
(c)
The
Type
3
curve
is
representative of a brittle or non-ductile behavior. It
strength of a component or element at the
is characterized by an elastic range, followed by a
deformation level under consideration for force-
rapid and complete loss of strength.
Component
controlled actions.
Lower-bound strength is
actions resulting in this behavior are always
typically established by the lower five percentile of
yield, buckling, or brittle failure strength. QCE and
categorized as force-controlled. Shear critical (i.e.,
QCL are further defined in Paragraph 6-3a(3).
shear capacity is attained prior to flexural capacity)
6-5
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