Direct Strength Prediction of Cold-Formed Steel Beam-Columns
Y. Shifferaw, B.W. SchaferReport to AISIFebruary 2012
Current Progress
Prelim. Formulation (dist. 1 of 2)
g
Prelim. Formulation (dist. 2 of 2)
Modeling• Nonlinear shell FE
models of imperfect CFS member
• End displacements over desired P, Mx, My
• Boundary conditions and lengths to isolate local and distortional buckling
• Preliminary models completed with success
P-Mmajor, distortional, C section
P-Mminor, distortional, C section
Local DSM vs minor axis strength bounds for C
-1.5 -1 -0.5 0 0.5 1 1.50
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Mz/Mz,y
P/P
yDSM vs Strength Bounds-362Cloc,minor
FE-LocDSM anchor pts
Yield
Loccr
DSM proposedInteraction
Potential!
Selecting industry relevant beam-columnsTrusses
Load combinationsD+LL D+0.75LL+0.75W D+LL+W
Fy (ksi) L- ft W Pa-lb Ma-ft.lb P- lb Mmax Interaction P M max Interaction P lb M max- lbin Interaction
DEVCO Lower level 600S162-54 50 9 15 psf 5098 1947 3088 lb 502lb-ft 0.887 2576lb 536lb-ft 0.727
ADTEK-Exterior bearing wall
600S200-54-3rd floor 50 11.5 22psf/29p/f 7093 2326.6 4000 479.4 0.81
600S250-68-2nd floor 50 10.42 22psf/29p/f 10711.2 3251.2 8300 393.6 0.92
600S250-97-1st floor 50 10.42 22psf/29p/f 17399.1 4801.3 12600 393.6 0.83
NUCON
1st Exterior End walls 550NF150-43 @16"
50 10 25.17psf 3.540kips 1.068ft-kips 2.383kips 0.418ft-kips 0.89
1st Exterior walls 550NF150-43 @2"
50 10 25.17psf 3.540kips 1.068ft-kips 1.840kips 0.629ft-kips 0.92
2nd Exterior walls 550NF150-43@2"
50 10.5 25.01psf 3.540kips 1.068ft-kips 1.280kips 0.689ft-kips 0.82
1st interior wall at unit AL-A 550NF150-
33@16"50 10 5psf 2.371k 0.751ftk 2.329k 0.083ft-kips 0.98
1st interior wall at unit AL-A 350NF150-
43@16"50 10 5psf 2.592k 0.588ftk 2.329k 0.083ft-kips 0.9
Selecting industry relevant beam-columnsFraming
Selecting efficient sections
Most efficient
Pn/A
Mn/A
• Identifying SSMA sections based on limit state
• Identifying SSMA sections based on limit state
Selecting Member length
TestingRelated recent testing:
Basic basis for our forthcoming testing…
Current Progress
Conclusion: work is modestly behind, but progress being made. Looking forward to providing More results, including testing results, at July meetings.