UFC 4-023-03
25 January 2005
C-2.5
Member Sizes.
Members were designed using the most severe design requirements for any
member in a group. For example, 1st floor spandrels and 5th floor spandrels are both
20 in x 24 in concrete members. See Table C-1 for preliminary design member sizes
and reinforcement of the lateral-resisting system.
Table C-1 Reinforced Concrete Member Sizes and Reinforcement
Member Group
Dimensions Bottom Reinf.
Top Reinf.
B = 24 in
1.76 in2
2.4 in2
Spandrels
D = 20 in
B = 24 in
1.76 in2
2.4 in2
Interior Beams
D = 20 in
B = 30 in
2.42 in2
4.48 in2
Girders
D = 20 in
B = 30 in
2.2 in2
3.25 in2
Spandrel-Girders
D = 20 in
8 in2
Bottom Columns
20 in x 20 in
6.32 in2
Top Columns
20 in x 20 in
*In SAP, reinforcement used for design can be defined in the
section properties under the reinforcement overrides for ductile
beams.
C-3
TIE FORCE CHECK.
After designing the reinforced concrete moment frame building, tie forces are
calculated to ensure progressive collapse requirements are met. The concrete structure
designed in step 1 easily meets tie force requirements (See Table C-2 for tie forces and
member comparisons).
For the example structure:
Ft
=
lesser of (4.5+0.9no) or 13.5 kips; if no = 5, Ft = 9 kips
lr
=
25 ft
ls
=
12 ft
s
=
25 ft (internal ties on column lines)
D
=
SW + SDL; SW = 54 psf, SDL = 35 psf
D
=
89 psf
L
=
50 psf
Atrib
625 sf
=
C-4
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