topic Re: AS4100 clause 8.4.2.2 in Robot Structural Analysis Forum

AS4100 clause 8.4.2.2

Anonymous — Fri, 18 May 2012 15:53:54 GMT

Artur,

The formula for Mi in clause 8.4.2.2. (in plane capacity)

Mi = Ms(1- N*/phiNc)

I believe Robot correctly calculates Miy (using the value of phiNcy), but when calculating Miz it INCORRECTLY uses Ncy as well, instead of Ncz.

Please can you confirm this?

tony

Re: AS4100 clause 8.4.2.2

Artur.Kosakowski — Mon, 21 May 2012 06:35:35 GMT

Tony,

Could you send me some test model that illustrates this situation and indicate what you think is wrong please? It would be much easier for me as AS4100 is not the code I'm familiar with. Thank you.

Re: AS4100 clause 8.4.2.2

Anonymous — Mon, 21 May 2012 07:14:04 GMT

Attached.

Also, please check clause 8.4.2.2. Ke for this clause should be set at no greater than 1.0 to calculate Nc, Robot instead uses Ke as defined (i.e. 1.2, 2.2 etc)

Cheers,

Re: AS4100 clause 8.4.2.2

Artur.Kosakowski — Mon, 21 May 2012 10:47:44 GMT

Tony,

1. ke value from 8.2.2.2

What is currently done: Robot takes(if entered manually) or caculates (based on stiffness of elements from the top and bottom nodes) value of ke in the buckling check part as decribed in 4.6.3. This value can be below 1 (braced frame) or above 1 (sway frame). Then this ke value is compared with ke=1 and the larger value is used for Nc calculations

What I think should be done is: Robot takes(if entered manually) or caculates (based on stiffness of elements from the top and bottom nodes) value of ke in the buckling check part as decribed in 4.6.3. This value can be below 1 (braced frame) or above 1 (sway frame). Then this ke value is compared with ke=1 and the smaller value is used for Nc calculations

Am I correct?

2. Miz INCORRECTLY uses Ncy as well, instead of Ncz

I think that Ncz (not Ncy) is (corerctly) used. Are you able to create the test model where you can see this issue?

Re: AS4100 clause 8.4.2.2

Anonymous — Mon, 21 May 2012 11:12:05 GMT

Artur,

For point 1;

Yes you are correct. Ke should be 1.0 or less than 1.0, - as long as............... In pure compression, N*/phiNc < 1.0 with Ke set as the actual value calculated in 4.6.3.

For Point 2:

Sorry, the model I sent you had the column broken into two parts. It should be 8m long. Anyway, for the 8m long column, the results below show that Robot is using the wrong NC for calculation of phiMiz

Cheers,

Tony

Re: AS4100 clause 8.4.2.2

Artur.Kosakowski — Mon, 21 May 2012 11:42:32 GMT

Tony,

Please send me the file you used to generated the calculation report from your last answer. Trying to edit the previous file I'm getting different values. Thank you.

Re: AS4100 clause 8.4.2.2

Anonymous — Mon, 21 May 2012 11:58:06 GMT