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« Last post by **David Hughes ** on* February 20, 2020, 07:53:31 AM* »
Hi,

I am trying to follow how HyperSizer is calculating the Discrete Stiffened Panel loads for technique 2 so as I can understand the limitations. Apologies for the long message, but I have a few questions:

1) When creating the segments there is an option to create a stringer or frame segment. What’s the difference?

2) After upgrading to v8.0.47 I noticed that there is a new DSM backdoor option:

"Modify technique 2 beam fea moments to account for stiffener height"

What does this mean? Is it something related to bar offsets, or is it the moment correction for Cruciform sections, or is it something else?

3) V8 now incorporates the integral cruciform concept into the native environment, however there is no specific documentation. Is it the same as the method/equations used for the Metal Grid Stiffened Plugin?

4) Within the FEA Loads tab why are the tension and compression tables empty?

5) Within the FEA Loads document, section 4 gives the equations for the N-sigma methods. Do similar equations apply for BAR elements using length instead of area? Also, I cannot match the standard deviation values. Is the equation missing an n term (where n=number of elems) or is it something else?

SD = (Sum((Ni - Navg)^2*Ai)/(((n-1)/n)*Sum(Ai)))^0.5

6) Within the FEA Loads document for Discretely Stiffened Panels I believe the transformation equations are incorrect (eq. 1 to 3):

Nxy = -Fx*cos(q)*sin(q) + Fy*cos(q)*sin(q) + Fxy(cos^2(q)-sin^2(q))

Similar for Mxy

Qxx = +Vx*cos(q)+Vy*sin(q)

Qyy = -Vx*sin(q)+Vy*cos(q)

7) For the Discretely Stiffened Panel’s transverse shear summation (eq. 41), I’ve found cases when the skin load relieves the total. I haven’t noticed this for Nx,seg and I’m still working on Mx,seg. I believe the full Qx,seq equation is:

Qx,seg = (V1 + sign(V1)*(Qxx,L*wL/2+Qxx,R*wR/2)))/(1/2*(wL+wR))

Where: V1 = if |V1,t|>|V1,c| then V1,t else V1,c

Similarly for Qxx,L and Qxx,R

Test case;

wL/2 = 100 wR/2 = 100

Qxx,t,L = 0.5 Qxx,t,R = 6.0

Qxx,c,L = -1.0 Qxx,c,R = -3.0

V1,t = 200

V1,c = -500

V1 = -500

Qxx,L = -1.0

Qxx,R = 6.0

Qx,seg = (-500 - (-1.0*100 + 6.0*100))/200 = (-500+100-600)/200 = -5N/mm

Note that the LH Skin is relieving the load.

Kind Regards,

David