To check adequacy of a section, the program checks the demand/capacity (D/C) ratios
at
a
predefined
number
of
stations
for
each
design
load
combination.
It
calculates
the
envelope
of
the
D/C
ratios.
It
also
checks
the
other
requirements
on a
pass
or
fail
basis.
If
the
capacity
ratio
remains
less
than
or
equal
to
the
D/C
ratio
limit,
which
is
a number
close
to
1.0,
and
if
the
section
passes
all
the
special
requirements,
the
section
is
considered
to
be
adequate,
else
the
section
is
considered
to
be
failed.
The
D/C
ratio
limit
is
taken
as
0.95
by
default.
However,
this
value
can
be
overwritten
in
the
Preferences
(see
Chapter
3).
To choose (design) the optional section from a predefined list, the program first
orders the list of sections in increasing order of weight per unit length. Then it
starts checking each section from the ordered list, starting with the one with
least weight. The procedure of checking each section in this list is exactly the
same as described in the preceding paragraph. The program will evaluate each
section in the list until it finds the least weight section that passes the code
checks. If no section in the list is acceptable, the program will use the heaviest
section but flag it as being overstressed.
To check adequacy of an individual section, the user must assign the section
using the Assign menu. In that case, both the analysis and design sections will
be changed.
To choose the optimal section, the user must first define a list of steel sections,
the Auto Select sections list. The user must next assign this list, in the same
manner as any other section assignment, to the frame members to be optimized.
The
program
will
use
the
median
section
by
weight
when
doing
the
initial
analysis.
Check
the
program
Help
for
more
information
about
defining
and
assigning
Auto
Select
Section
lists.
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