Autodesk Robot Structural Analysis

[#1]

Please can someone help?

I have two members that are loaded similarly and one fails and the other does not, can someone tell me within the results attached why one is failing?

Many Thanks.

STEEL DESIGN

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CODE:

   BS-EN 1993-1:2005/NA:2008/AC:2009,  Eurocode 3: Design of steel structures.

ANALYSIS TYPE:

   Member Verification

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CODE GROUP:

MEMBER:

   63  Beam_63POINT:   1COORDINATE:   x = 0.75 L = 5.715 m

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LOADS:

Governing Load Case:

   17 1.2DL + 1.2LL + 1.2WL(S)  (1+2+3+4+5+14)*1

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MATERIAL:

S355  ( S355 )       fy = 355 MPa         

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　  SECTION PARAMETERS:  CHS 114.3x5

h=114.300 mm gM0=1 gM1=1

b=114.300 mm Ay=1094.986 mm2 Az=1094.986 mm2 Ax=1720.000 mm2

tw=5.000 mm Iy=2570000.000 mm4 Iz=2570000.000 mm4 Ix=5140000.000 mm4

tf=5.000 mm Wply=59774.117 mm3 Wplz=59774.117 mm3

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INTERNAL FORCES AND CAPACITIES:

N,Ed = -334.30 kN  My,Ed = 12 kN*m Mz,Ed = -2 kN*m Vy,Ed = -1.31 kN

Nt,Rd = 610.60 kN My,pl,Rd = 21 kN*m Mz,pl,Rd = 21 kN*m Vy,T,Rd = 136.02 kN

My,c,Rd = 21 kN*m Mz,c,Rd = 21 kN*m Vz,Ed = -5.76 kN

My,N,Rd = 14 kN*m Mz,N,Rd = 14 kN*m Vz,T,Rd = 136.02 kN

Tt,Ed = 7 kN*m

Class of section = 1

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　    LATERAL BUCKLING PARAMETERS:

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BUCKLING PARAMETERS:

      About Y axis:       About Z axis:

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VERIFICATION FORMULAS:

Section strength check:

N,Ed/Nt,Rd = 1 < 1   (6.2.3.(1))

(My,Ed/My,N,Rd)^ 2 + (Mz,Ed/Mz,N,Rd)^2 = 1 < 1   (6.2.9.1.(6))

Vy,Ed/Vy,T,Rd = 0 < 1   (6.2.6-7)

Vz,Ed/Vz,T,Rd = 0 < 1   (6.2.6-7)

Tau,ty,Ed/(fy/(sqrt(3)*gM0)) = 0 < 1   (6.2.6)

Tau,tz,Ed/(fy/(sqrt(3)*gM0)) = 0 < 1   (6.2.6)

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Section OK !!!

STEEL DESIGN

----------------------------------------------------------------------------------------------------------------------------------------

CODE:

   BS-EN 1993-1:2005/NA:2008/AC:2009,  Eurocode 3: Design of steel structures.

ANALYSIS TYPE:

   Member Verification

----------------------------------------------------------------------------------------------------------------------------------------

CODE GROUP:

MEMBER:

   64  Beam_64POINT:   1COORDINATE:   x = 0.75 L = 5.715 m

----------------------------------------------------------------------------------------------------------------------------------------

LOADS:

Governing Load Case:

   17 1.2DL + 1.2LL + 1.2WL(S)  (1+2+3+4+5+14)*1

----------------------------------------------------------------------------------------------------------------------------------------

MATERIAL:

S355  ( S355 )       fy = 355 MPa         

----------------------------------------------------------------------------------------------------------------------------------------

　  SECTION PARAMETERS:  CHS 114.3x5

h=114.300 mm gM0=1 gM1=1

b=114.300 mm Ay=1094.986 mm2 Az=1094.986 mm2 Ax=1720.000 mm2

tw=5.000 mm Iy=2570000.000 mm4 Iz=2570000.000 mm4 Ix=5140000.000 mm4

tf=5.000 mm Wply=59774.117 mm3 Wplz=59774.117 mm3

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INTERNAL FORCES AND CAPACITIES:

N,Ed = 308.06 kN  My,Ed = 17 kN*m Mz,Ed = -0 kN*m Vy,Ed = -0.25 kN

Nc,Rd = 610.60 kN My,pl,Rd = 21 kN*m Mz,pl,Rd = 21 kN*m Vy,T,Rd = 120.07 kN

Nb,Rd = 610.60 kN My,c,Rd = 21 kN*m Mz,c,Rd = 21 kN*m Vz,Ed = -8.49 kN

My,N,Rd = 15 kN*m Mz,N,Rd = 15 kN*m Vz,T,Rd = 120.07 kN

Tt,Ed = 9 kN*m

Class of section = 1

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　    LATERAL BUCKLING PARAMETERS:

----------------------------------------------------------------------------------------------------------------------------------------

BUCKLING PARAMETERS:

      About Y axis:       About Z axis:

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VERIFICATION FORMULAS:

Section strength check:

N,Ed/Nc,Rd = 1 < 1   (6.2.4.(1))

(My,Ed/My,N,Rd)^ 2 + (Mz,Ed/Mz,N,Rd)^2 = 1 > 1   (6.2.9.1.(6))

Vy,Ed/Vy,T,Rd = 0 < 1   (6.2.6-7)

Vz,Ed/Vz,T,Rd = 0 < 1   (6.2.6-7)

Tau,ty,Ed/(fy/(sqrt(3)*gM0)) = 0 < 1   (6.2.6)

Tau,tz,Ed/(fy/(sqrt(3)*gM0)) = 0 < 1   (6.2.6)

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Incorrect section !!!

[#2]

one is in tension, one is in compression?

[#3]

N,Ed/Nt,Rd = 1 < 1   (6.2.3.(1))

(My,Ed/My,N,Rd)^ 2 + (Mz,Ed/Mz,N,Rd)^2 = 1 < 1   (6.2.9.1.(6))

N,Ed/Nc,Rd = 1 < 1   (6.2.4.(1))

(My,Ed/My,N,Rd)^ 2 + (Mz,Ed/Mz,N,Rd)^2 = 1 > 1   (6.2.9.1.(6))

Please increase the precision of displaying the results. From the info you provided I assume it is sort of 0.999 < 1 for one of the bars and 1.001> 1 for the other.

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

[#4]

I have a question regarding a verification note.

Is it possible to have this: Tau,ty,Ed/(fy/(sqrt(3)*gM0)) = 1.41 > 1.00 (6.2.6)

All the efforts in the bar are very small.

[#5]

Torsion.