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2. Composite Sections and Steel Beam Design
Architecture 324
Structures II
Composite Sections and Steel Beam Design
Steel Beam Selection - ASD
Composite Sections
Analysis Method
PvB
University of Michigan, TCAUP Structures II Slide 2/21

3. Steel W-sections for beams and columns
Standard section shapes:
W – wide flange
S – american standard beam
C – american standard channel
L – angle
WT or ST – structural T
Pipe
Structural Tubing
GSI
Source: University of Michigan, Department of Architecture
University of Michigan, TCAUP Structures II Slide 3/21

4. Steel W-sections for beams and columns
Closer to square
Thicker web & flange
Beams:
Deeper sections
Flange thicker than web
Source: University of Michigan, Department of Architecture
GSI
Source: University of Michigan, Department of Architecture
University of Michigan, TCAUP Structures II Slide 4/21

5. Steel W-sections for beams and columns
Closer to square
Thicker web & flange
Beams:
Deeper sections
Flange thicker than web
CC#
Attribution-Share Alike 2.0 Generic
Attribution.
gregor y
CC:BY-SA Gregor_y (flickr)
University of Michigan, TCAUP Structures II Slide 5/21

6. Steel Beams by ASD Yield Stress Values Allowable Flexure Stress
A36 Carbon Steel Fy = 36 ksi
A992 High Strength Fy = 50 ksi
Allowable Flexure Stress
Fb = 0.66 Fy • = Lc
Compact Section
Braced against LTB (l <Lc)
Fb = 0.60 Fy ° = Lu
Compact or Not
Lc < l < Lu
Fb < 0.60 Fy
LTB failure mode (l >Lu)
Allowable Shear Stress
Fv = 0.40 Fy
fv=V/(twd)
[1] Manual of Steel Construction Allowable Stress Design, 9th ed. 1989
AISC ISBN p
Source: AISC, Manual of Steel Construction Allowable Stress Design, 9th ed. 1989
University of Michigan, TCAUP Structures II Slide 6/21

7. Section Modulus Table Calculate Required Moment
Assume Allowable Stress
Fb = 0.66Fy = 24 ksi (A36)
Fb = 0.60Fy = 21.6 ksi (A36)
Using the flexure equation,
set fb=Fb and solve for S
Choose a section based on S from the table (D-35 and D-36)
Bold faced sections are lighter
F’y is the stress up to which the section is compact (•• is ok for all grades of Fy)
[2] Structural Principles, I. Engel ISBN
P. 354
Source: Structural Principles, I. Engel 1984
University of Michigan, TCAUP Structures II Slide 7/21