LATERAL-TORSIONAL BUCKLING

LATERAL-TORSIONAL BUCKLING

Lu > LcLu = L = unbraced length

Lc = unbraced length limit for compact

Allowable bending stress in tension = 0.6 FyAllowable bending stress in compression

Fb = 0.6 Fy

Fb = (eqn 506-6)

Fb = (eqn 506-7)

(506-6 or 506-7) & 506-8 Higher Fb = Fb

Sample:

FEMs

Final Ms

Span AB

Span BC

Using W24 and A-36 steel, determine the lightest section for the prismatic beam.

a. Assume full lateral support

b. Assume that the lateral supports are at the vertical supports only.

From steel handbook:

EMBED Equation.3 For span ABLu = 10.5 m > Lc = 2.9032 m

EMBED Equation.3

(506-7)

(506-8)

Span BC

L = 12 m

64.861 MPa < 125.93 MPa

Use Fb = 64.861 MPa

Assignment # 2

Determine the lightest section with lateral supports at 1/3 point.

FEMs

Final Ms:

Span AB:

Span BC:

W24103

Segment 1:

Design M = 298.75 kN-m, L = 3.5 m,

Segment 2:

Design M = 301.70 kN-m, L = 3.5 m,

Segment 3:

Design M = 573.75 kN-m, L = 3.5 m,

Segment 4:

Design M = 573.75 kN-m, L = 4 m,

Segment 5:

Design M = 306.68 kN-m, L = 4 m,

Segment 6:

Design M = 613.13 kN-m, L = 4 m,

Quiz # 2

1. Determine the lightest section for the rafters using A-50 steel. Assume full lateral supports.

FEMs:

Final moments:

2. Determine the maximum uniform load w that the beam can carry using A-36 steel. The lateral supports are as shown below.

FEMs:

Final moments:

Span AB:

Span BC:

Panel AD

Panel DB

Panel BE

Panel EC

EMBED Equation.3

EMBED Equation.3

Single curvature

Reverse curvature

Double curvature

L1

L2

L33

EMBED Equation.3

EMBED Equation.3

EMBED Equation.3

w

x

VA

EMBED Equation.3

h

EMBED Equation.3

200

1.5I

1.5I

I

I

200

200

200

200

100

100

2.3 m

4 m

1.6

1.6

1.7

1.7

1.8

1.8

200

1.5I

I

200

200

100

2.3 m

4 m

1.6

1.7

1.8

A

B

C

100

200

200

A

B

C

4 m

EMBED Equation.3 m

_1223314922.unknown

_1223321812.unknown

_1223323938.unknown

_1223366142.unknown

_1223366429.unknown

_1223366758.unknown

_1223366936.unknown

_1223367084.unknown

_1223367124.unknown

_1223366950.unknown

_1223366852.unknown

_1223366727.unknown

_1223366269.unknown

_1223366278.unknown

_1223366201.unknown

_1223324991.unknown

_1223365526.unknown

_1223365791.unknown

_1223365970.unknown

_1223365372.unknown

_1223324392.unknown

_1223324975.unknown

_1223324227.unknown

_1223323562.unknown

_1223323917.unknown

_1223323927.unknown

_1223323682.unknown

_1223322894.unknown

_1223323403.unknown

_1223322393.unknown

_1223316444.unknown

_1223317223.unknown

_1223317245.unknown

_1223317477.unknown

_1223321249.unknown

_1223317233.unknown

_1223316769.unknown

_1223316992.unknown

_1223316747.unknown

_1223316513.unknown

_1223316588.unknown

_1223315848.unknown

_1223316100.unknown

_1223316293.unknown

_1223316024.unknown

_1223315724.unknown

_1223315780.unknown

_1223314932.unknown

_1215345790.unknown

_1215346503.unknown

_1223309006.unknown

_1223309214.unknown

_1223309544.unknown

_1223309123.unknown

_1215346548.unknown

_1215346678.unknown

_1215346515.unknown

_1215345958.unknown

_1215346113.unknown

_1215346491.unknown

_1215346078.unknown

_1215345805.unknown

_1215345881.unknown

_1215345798.unknown

_1215343985.unknown

_1215345124.unknown

_1215345565.unknown

_1215345595.unknown

_1215345554.unknown

_1215345337.unknown

_1215344623.unknown

_1215344805.unknown

_1215344221.unknown

_1215344451.unknown

_1215341366.unknown

_1215343083.unknown

_1215343792.unknown

_1215343886.unknown

_1215343562.unknown

_1215343654.unknown

_1215341800.unknown

_1215342778.unknown

_1215341726.unknown

_1215341250.unknown

_1215341291.unknown

_1215341125.unknown