load cases

Friends,

another question about the cases loads...

for the restrains, moments and displacements always should use this case:
W+P+T+U (OPE)

but, for the code, is the same to realize the analysis whit native loads and combinations loads:

L5= W+P (SUS)
L6= W+P+U (OCC)
L7= L6-L5 (only for construction case)
L8= L5+L7 (OCC)

for the analysis code, L6 = L8???

thanks.

Read the posts (and follow the links) in this thread.

ok, already been this topic and the animation in the tutorial, but

what do the C2 do in this step??
always I should construct 'construction case L7' (in ALG) for the OCC load (L8) for compare to code with SCA o ABS, for what?????

also, I think that need know what is the diference between ALG, ESC and ABS. The 'help' in C2 is not enough for me.

thanks

-a.e.-

The FEA solution begins with [K]{x} = {f}, where [K] and {f} are constructed from the input and the software solves for {x}. {x} is the “displacement vector”. Once these displacements are known, the forces and moments acting on each element can be determined. From these forces and moments the Code rules are applied and stresses are obtained.

The displacements and forces (and moments) of an Algebraic case and a Scalar case are equivalent. However, there could be a variation at the stress level between these two methods – since in an Algebraic combination the stresses are computed (from the forces and moments) while for a Scalar combination the stresses are simply added.

For example:
Load Case 1: Bending stress = 100 psi, due to X-moment
Load Case 2: Bending stress = 100 psi, due to Z-moment

Algebraic (vectorial) sum = sqrt(100*100 + 100*100) = 144 psi

Scalar sum = 100 + 100 = 200 psi
Scalar would typically be used to sum (SUS + OCC) code stresses.

Absolute simple combines the “absolute value” of the terms. So displacements are the “absolute” sum of the displacements in the load case. Forces are not computed from the displacements, but rather are the “absolute” sum of the forces in the load case. Stresses are not computed from the forces, but rather are the “absolute” sum of the stresses in the load case.

Richards,

in this cases:
L3=W+T+P (OPE)
L6=W+T+P+U (OPE)

the sum is ALG or SCA?

thanks for responses

-a.e.-

Neither, these are "basic load cases" which combine "load primatives". The load vector {f} (in [K]{x} = {f}) includes the effects of all of the specified primatives.

This is why we try to make a distinction between "basic load cases" and "combination load cases". Basic load cases consist of primatives that for the load vector {f}. Combination cases are combinations of basic cases, and here is where the combination options/methods come into play.