1. KNOWLEDGE BASE REQUIRED:
STEEL DESIGN REVIEW (UNBRACED LENGTH)
KNOWLEDGE BASE REQUIRED:
STRENGTH OF MATERIALS
TIMBER DESIGN
SOIL MECHANICS
STEEL DESIGN

2. LECTURE #4(CONT) BASIC SOIL MECHANICS REVIEW: LATERAL STRESSES:
30.7KN/m2
17.7KN/m2

3. STEEL DESIGN REVIEW BASIC SOIL MECHANICS REVIEW: LATERAL FORCE:
R= =138.43KN
30.7KN/m2
107.45KN
138.43KN
30.98KN
1.62m
17.7KN/m2

4. LECTURE #4(CONT) BASIC STEEL DESIGN REVIEW:
Review of AISC Construction Manual (cont):
Compact vs. Non- Compact
Compact Beam are rolled beam that can achieve
the plastic moment.

5. LECTURE #4(CONT) BASIC STEEL DESIGN REVIEW: Recall l, lc, and lu
if l is the given length between lateral supports
then,
lc>l use Fb=.66Fy (assuming compact section)
lu>l>lc use Fb=.60Fy
l>lu use the charts of allowable moments in beams
(p to 2-212) where Cb=1
Note: Cb is the bending coefficient dependent upon
moment gradient (F1.3)
Cb=1
when the bending moment at any point within
an unbraced length is larger than that at both
ends of this length
when frames are braced against joint translation.
when considering a conservative value for cantilever

6. LECTURE #5 BASIC STEEL DESIGN REVIEW: Given:
Select a beam of Fy=36ksi steel subjected to a
bending moment of 125 kip-ft., having its compression
flange braced at 6 ft. intervals.
Solution:
Assume compact section, Fb=0.66Fy=23.8ksi
1. Maximum Bending Moment Given in Problem
2. Sx(reqd)=M/Fb=(125x12)/23.8=63 cu.in.
3. Nearest Tabulated Value
W16x
W12x
Since W16x40 is bold face, it is the lightest
suitable section that will serve for that yield strength.

7. LECTURE #5 BASIC STEEL DESIGN REVIEW: Given:
Select a beam of Fy=36ksi steel subjected to a
bending moment of 125 kip-ft., having its compression
flange braced at 6 ft. intervals.
Solution contd:
4. A check of the F’y column shows a dash, indicating
that F’y is greater than 65 ksi. Therefore, the shape
is compact.
5. From the table, Lc=7.4 ft. >6.0 ft. so the bracing is
adequate and the assumed allowable stress of .66Fy
is correct. Use W16x40