topic Re: Steel design to Eurocode - issue with SLS verification in Robot Structural Analysis Forum

Steel design to Eurocode - issue with SLS verification

rokas_varanauskas — Fri, 15 Dec 2023 08:47:40 GMT

In Robot Version 2024 with Hotfix 1 installed, I have found the issue with SLS verification in steel design to Eurocode.

See screenshot below:

Steel check was done with ULS combinations and only one live load case for the purpose of showing this bug.

As can be seen from the screenshot, Case 3 is a live load case, defined as Category C under load types, however in SLS verification this is treated as total load combination to check L/250. What I would expect to see is L/250 to have zero and instantaneous load check to have deflection of 3.47mm and verified against L/360 limit. I don't have access to older Robot versions anymore, but I'm pretty sure you could run SLS verification from primary load cases as well as combinations in the previous versions with no issues.

If case 3 is used on SLS combination with dead loads then verification is done correctly where for L/360 check all permanent loads are ignored and only live loads used.

It's looks like 2024 version has multiple "minor" issues, which is a concern to me as a designer.

Re: Steel design to Eurocode - issue with SLS verification

CaioSaporito — Fri, 15 Dec 2023 16:20:12 GMT

Hi @rokas_varanauskas.

Have you checked the limit of deflection in code parameters?

I mean, have you marked total loads or live loads in code parameters?

Best regards,

Caio

Re: Steel design to Eurocode - issue with SLS verification

rokas_varanauskas — Fri, 15 Dec 2023 16:21:44 GMT

Yes, all necessary boxes ticked.

Re: Steel design to Eurocode - issue with SLS verification

rokas_varanauskas — Mon, 15 Jan 2024 09:19:11 GMT

The same as above issue is observed with column SLS verification! All combinations were created using Automatic code combinations module with manual selection of cases. All combinations for SLS were set as SLS:CHR as per below:

For bar no 143 the following SLS deflection limits are set:

with the design verification output provided below showing that columns fail in vy direction with displacement of 25.87mm vs limit of 16.61mm.

I've done manual verification of above checks and found that in both cases dead load deflections are included in overall SLS deflection check even though only variable loads should be considered.

There's not much in Robot manual about how deflections are verified and what combinations are required, but I'm certain that Robot used to take out dead loads from combinations and only run SLS check against variable actions which is still does for beams as demonstrated below:

@okapawal @Stephane.kapetanovic

Re: Steel design to Eurocode - issue with SLS verification

Stephane.kapetanovic — Mon, 15 Jan 2024 09:38:27 GMT

hi @rokas_varanauskas

I apologize, but I am not interested in discussing this topic.

If you observe that the self-weight should not be considered for a customized deformation criterion, create combinations without including the permanent cases.

In the case of horizontal criteria, the self-weight must often be taken into consideration.

Exclusion of permanent loads from the criterion is applicable only to the live criterion. Therefore, please ensure to verify that the justifications align with this requirement

Best Regards

Re: Steel design to Eurocode - issue with SLS verification

rokas_varanauskas — Mon, 15 Jan 2024 11:29:01 GMT

not sure where my previous response disappeared but I'll try again.

I appreciate your response @Stephane.kapetanovic but I do not agree with your position.

Under Eurocode 3 deflections are to be verified under variable loads as per below:

For beams, robot does verify total load deflection (DL+LL) and live load deflection (LL) from the same SLS:CHR combination. Since under EC3 requirements column displacement should be verified under variable loads, same as for beams, dead loads should be excluded from SLS:CHR combination.

I do agree that in some instances dead loads need to be considered for SLS verification of columns, but I would do this as a separate exercise.

Can you please provide how Robot is doing SLS verification under EC3 member design as this section is not included in Robot help, see below:

Re: Steel design to Eurocode - issue with SLS verification

Stephane.kapetanovic — Mon, 15 Jan 2024 11:45:41 GMT

As explained, you need to get in touch with the development team. The inner workings of the program must be explained by Autodesk. As far as transverse stiffness and horizontal deformation criteria are concerned, it does not seem to have been so positive, especially since you have to check the adequacy your self compared to the BS. Kind regards.

Re: Steel design to Eurocode - issue with SLS verification

rokas_varanauskas — Mon, 15 Jan 2024 11:48:03 GMT

apologies if incorrectly addressed - I was under impression that you are part of Autodesk.

Re: Steel design to Eurocode - issue with SLS verification

rokas_varanauskas — Mon, 15 Jan 2024 13:14:36 GMT

@Krzysztof_Wasik can you please advise on who should be able to help with above issue? Thanks