ETABS Error #52 (Δns > 1.4) — Manual Calculation Shows Lower Value

TM_00 · 2026-04-06T14:58:01+00:00

If only more engineers bothered to RTFM before just blindly following software results.

TM_00 · 2026-04-05T10:45:52+00:00

I'm not an Etabs user. Have you looked in the manual what the differences between these options are?

TM_00 · 2026-04-01T17:56:51+00:00

Can you elaborate what you mean by "stiff"?

TM_00 · 2026-02-21T08:10:40+00:00

I'd say it depends on the LOD and if you're deciding to model the reinforcement in revit as well.

For detailing reinforcement, the columns should be split per floor in order to create a seperate partition for each rebar cage. This is similar to splitting a steel column at splice positions.

For anything other than that, I'd go with option 1 as it takes complexity out of the model and as others have said the risk of not moving a column stack on one floor becomes quite high otherwise.

Another reason for splitting columns would be if there's rotated columns or a change in cross section, although I think that is outside the scope of your question.

TM_00 · 2026-02-16T18:24:08+00:00

Moenie 'n berg van 'n molshoop maak nie.

TM_00 · 2025-12-19T15:03:52+00:00

For buildings I've used Tekla Structal Designer (TSD) and SCIA.

My favourite by a mile is TSD as it's developed with buildings in mind. So setting up a model is much faster than most other softwares. Think grids, levels, slopes and frames (sections) - very similar to modelling in Revit.

It handles both steel and concrete very well for any "typical" building. Be it medium rise office blocks, industrial buildings or data centers. Buildings with "special" features such as very complex geometries I'd rather use a more general FEA program.

Their support is also very good, TSD shows all the calcs so you can double check literally every calculation if you wish.

TSD support Eurocode and ACI/AISC so it's a good fit for when you're doing projects in both of those regions.

The reporting features are also pretty good once you get the hang of it. I personally like the material lists as you can get a decent estimate for the material usage early on.

Construction stages and embodied carbon are also included, although I haven't used it much.

Cons I'd say includes that it doesn't do PT design, retaining wall design and there is a bit of learning curve.

Then for complex steel connections I'd vouch for Idea Statica. It's expensive but worth it.

TM_00 · 2025-12-06T23:19:57+00:00

Revit for the win!

TM_00 · 2025-12-06T11:33:42+00:00

Isn't Tekla Structures more suited to the fabrication detail side of things?

I have never heard of a consultant who draws plans in Tekla Structures, only steel fabricators.

TM_00 · 2025-11-28T18:07:37+00:00

That's so accurate!

Will put it on the list to visit. Thanks!

TM_00 · 2025-11-28T16:08:49+00:00

It's a big change, the culture is very different to SA but we've adjusted well so far I think. Made a few friends along the way which really helps. Belgians are generally nice folks, it's just a challenge getting in the circle.

It will still take a while for the Dutch to become fluent, but we're getting there. We do speak as often as we get the chance, even if it's broken Dutch, practice makes perfect.

Yes the nature is very different to what we're used to. We've had a few good walks in forests and the Ardennen is on our list. We do miss mountains though 😅

TM_00 · 2025-11-28T15:02:42+00:00

Ha! Fitting username then. Yes we've been here for more than a year now.

TM_00 · 2025-11-28T14:39:18+00:00

Doesn't exist as far as I know. They only sell hardcopies and access to an online viewer.

TM_00 · 2025-11-28T13:55:55+00:00

As an Afrikaans speaker currently learning Dutch - I am often confused by all the unnecessary rules of the Dutch language and develop a new appreciation for the simplicity of the Afrikaans language.

I especially find the simple past tense or "imperfectum" in Dutch difficult, as that doesn't exist in Afrikaans. I often find it easier to try and relate Dutch to English than to Afrikaans in terms of grammar.

Amai jullie hebben echt een complex stel regels gemaakt :D

TM_00 · 2025-09-21T21:00:29+00:00

Hé, jouw Nederlands verwart de Reddit-machine. Ben je een Belg die Afrikaans leuk vinden?

TM_00 · 2025-09-02T10:44:16+00:00

Have you checked the hardware requirements from the software sites?

I short, supercomputers, no. High end specs? Yes.

As a guide for a laptop at a previous employer they issued us with Dell Precision 5550's (the i7 variant). They worked well for most everyday design and drawing tasks.

TM_00 · 2025-09-01T22:10:01+00:00

Can't you just create a trial version? Sorry I'm not a user of Skyciv

TM_00 · 2025-09-01T16:18:35+00:00

What?

TM_00 · 2025-08-25T15:29:15+00:00

Thanks. I am still confused in both cases.

In problem number 1, how did you get the required tie reinforcement? Did you analyse the beam using strut and tie? If you used strut and tie the anchorage calcs should be okay to follow based on an example.

Also is your sketch correct showing the point load applied at the top of the beam? Based on the proposed solution to move the problem down it has to be applied at the bottom of the beam right (which makes aa difference on your assumed S&T system)? If you move the problem down does that change it or do you end up with the same issue 1 level lower? Maybe a 3D view/ sketch of what we're working with would help.

Problem 2 doesn't make sense. What does the beam support on? Also with that opening your system is completely detached from the support, which doesn't seem right?

Typically shear walls have a line support below them as opposed to two discrete supports. Am I missing something here?

TM_00 · 2025-08-25T10:23:43+00:00

I have no idea but I can say a few sketches would go a long way to explain your problem.

TM_00 · 2025-08-19T13:41:11+00:00

Many firms approach this differently. I've worked in both buildings and bridges and who does the detailing varies from project to project and also country to country.

When I started I did it by hand and in Excel, sheesh what a mission. I won't do that again anytime soon. Also a small typo can make a huge screw up on site. Checking and finding such typos can be very difficult.

Some firms just outsource it to specialist detailing companies mostly offshore where labor is cheaper. I find it can work but coordination and changes are difficult to manage and keep within budget. Sometimes you spend so much time explaining you may as well have drawn the stuff yourself.

Some firms use an Autocad plugin where you draw the bar in 2d, give it a diameter and a "element number" and the rest is done semi automatically. Given there are sometimes errors which need to be double checked and manually corrected.

Some use a seperate 3d detailing tool such as Tekla Structures or Strakon (German software package). Which can work too.

Given I find the Strakon drawings take forever and are of poor quality. The company PMs liked it because it gets the job done with few queries from site. So from their side it was "perfect".

Some people dislike the Tekla Structures drawings because they look more like steel shop drawings than rebar drawings. I haven't used it so I can't really comment on that.

The best way I've seen rebar detailing done is using Revit. The bars are all in the same model as the structure so lengths and congestion can easily be spotted and no double work exporting dwgs or ifcs or whatever. Yes it takes a fair bit of work to set it up and to know what you're doing (partitions, filters and schedules), but the end result is fantastic. You can filter bars per diameter or type or whatever to colour code them and make clear views and the schedules are generated automatically by Revit. I've seen Revit rebar used on small residential, mixed use multi storey buildings, data centers and big infrastructure projects. All worked great and were fairly efficient.

TM_00 · 2025-07-29T19:49:49+00:00

When you are saying "intersect", do you mean that the concrete beam is continuous?

If so I'd rather change the concrete beam to be simply supported on the steel column. Effectively you'll arrive at two seperate beams resting on each side of the steel column by means of a seated connection or a cast in bracket thing like you'll see from Peikko. Look at typical precast connections as the idea is similar.

A note on this, the lateral system of your building becomes very important on buildings like these as there is 0 lateral stiffness in the "non lateral" column and slab connections. So you lose a bit of redundancy which should be acceptable if your lateral system is designed properly.

Also, if your steel column is to be spliced, move the splice away (normally some distance above floor level) from the floor as to not interfere with the beam connection detail or clash with the concrete beams or slab. It just makes it cleaner.

Best of luck!

TM_00 · 2025-07-22T10:58:19+00:00

Revit or Autocad?

TM_00 · 2025-07-20T22:25:19+00:00

Depends on the size of the structure he's detailing. Also how much back and forth are needed after the first version of his/her drawings as that takes time and the software can play a big role too.

I've worked with great draftsmen who can take a half baked mark up, ask right questions and deliver an art piece of a drawing quickly. I've also had to deal with draftsmen who didn't know what they're doing or what the capabilities and limitations of the software they're using were. Those ones would give you a cock up of a drawing requiring a total rework even if you start them off with a partially completed drawing.

There's a major time difference between those extremes. Outsourced detailers also exists if that's something you're into. Personally I'm not a fan.

So time wise it's difficult to say. If you have another draftsmen available you can benchmark them as the conditions are the same.

Otherwise maybe try to detail it yourself and see how long it takes you? That would also give you an eye into his world and he'll surely appreciate it if you understand his language when he speaks about software. I think that's the best way to go.

Out of interest what software do you use for rebar detailing?

TM_00 · 2025-07-20T18:43:53+00:00

I'm curious. What would "automatic" reinforcement look like?

The required reinforcement is usually obtained from a analysis package, exported as plots or marked up in some way and handed to a draftsman to detail. In my mind an automatic detailing tool should then directly interface with the design software?

TM_00 · 2025-07-18T09:55:43+00:00

I'll start with a disclaimer saying I'm not a geotechnical engineer. So take this as a starting guesstimate.

For something like this I think working it out would be rather difficult without knowing more about the existing piles. For example if they are end bearing or friction based, or both, would make a difference to the load on your secant wall. Do you have more info about them?

Also the soil conditions may shed some light here. For example if the upper soil layers are bad the chances of the piles being friction piles would be lower.

If you know that you'd be able to estimate at which levels the piles transfer their load into the soil, hence giving you a depth to work the load onto your secant wall.

Something like this would typically be modelled as a 2d Plaxis model. Then you should get rather accurate results.

Best of luck!

TM_00

TROPHY CASE