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/M

z,y

P/P

yDSM vs Strength Bounds-362C

loc,minor

FE-Loc

DSM anchor pts

Yield

Loccr

DSM proposed

Interaction

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.