Post Tension Slab Design Software 1

[mck26]

We are currently evaluating two software programs for P-T slab structure design: ADAPT Builder and RAM Concept (we already have the rest of the RAM structural suite). Does anyone have any comments//concerns/suggestions between these two software programs?

 

[SethGuthrie]

Of course I am partial (I work for Bentley), but the integration between RAM Structural System and Concept is very tight and a lot of our users have success using the two together.
We also offer a thing called the Structural Enterprise license which gives you access to all Ram and STAAD products and a few more for one low cost.
Good luck.

 

[CURVEB]

I have experience with both and have been using Adapt Builder quite a bit lately. I haven't used Concept too much, but here's what I know:
- Adapt ONLY does concrete. If you use mixed steel, wood, or masonry then RAM Structural System/Concept is probably a better option.
- The design output for Adapt leaves a little to be desired. I recall RAM citing the specific code reference that they use to calculate your required reinforcement. Adapt does not do it at this time - they just list the controlling load combination. I think they make up for this by publishing very good technical documents about the calculations they are running.
- Adapt doesn't currently have built-in wall openings which can be frustrating. RAM does have this capability.
- Adapt's licensing is much more straight-forward than Bentley IMO unless things have changed recently.
- I personally like Bentley's output reports from RAM better than Adapts. Easier to read and verify.
- Bentley reports COM and COR in their frame module. It also has more tools for reporting/viewing lateral drifts. This can be really helpful for verifying your model.
- Adapt currently has a little more flexibility for creating load cases and combinations, however it does not automatically generate load combinations the way RAM does.
- REVIT seems to export to Adapt a little bit better. It seems that that Adapt is very forgiving with modeling inaccuracies, but Bentley has also gotten better at this over the past few years.

 

[JoshPlumSE]

I won't throw my two cents into the ring, because I don't think I can offer an real insight...

But, I'm curious what separates a good PT program from a mediocre or poor one. I'm also curious how SAFE compares to these other two.

 

[ahypek]

I much prefer CSI software (SAFE) to Bentley products. It's not that I have an issue with the results and output from RAM Concept it's just the same issue I have with every piece of software from Bentley.....horrific interface and clumsy spatial controls/drawing tools.

 

[ajk1]

Having used only ADAPT (not ADAPT BUILDER) occasionally over the past 20 years, I cannot comment on how it compares with other software, but I can say that the version of ADAPT I have used over the years is not user-friendly and the user's manual is not very helpful. This leads to difficulty especially when using it only occasionally. ADAPT is endlessly revising it and each new revision costs a lot of money. I am currently trying to use ADAPT to check existing p.t. beams and have to input the existing rebar into an ADAPT window that displays only 5 lines at a time! The means of defining the end of the rebar is unusual and awkward. I am betting this was not written by a structural engineer experienced in design and detailing or reinforced concrete. If your eyesight is not the greatest, you will have difficulty reading the tiny spidery lettering on many of the ADAPT input screens, as I do. I could go on and on...

I am not enamored with ADAPT and looking for other p.t. software. It is very interesting that there is other software out there. Thanks for the post.

 

[KootK]

ConcePT has been my go to for a while simply because I think that it's the fastest for model setup by far. SAFE is good analytically but I've always found their drawing tools to be clumsy. I haven't used ADapt beyond their simple 2D versions. I understand that they now have a package that will look at more than one floor at a time with regard to multi story shrinkage effects. That's appealing analytically if perhaps a little unwieldy production wise.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[rapt]

ajk1

If you are looking at a Modern 2D PT program (RC also) to look at beams and slabs, RAPT is the solution.

But it will cost you too. At least it is already there, not "coming".

 

[chamokinawan]

ADAPT Building might be overkill if you're using RAM as well. ADAPT PT will be most useful. We did a concrete parking structure and ordered ADAPT Building and would've been better off with the cheaper ADAPT PT, because that's all we really needed since we used RAM Structural for lateral. If you're not doing anything crazy then I would recommend ADAPT PT.

 

[calvinandhobbes10]

Prefer RAM Concept for its integration of column/wall reactions.

Honestly this preference is based on a program I can most quickly size concrete from (LT deflection and punching shear for slabs, etc), and most quickly absorb design changes such as column grid adjustments, openings, etc. I'm used to Concept and its mediocre interface (I find all to be clumsy) so I go with that. All will leave something to be desired in LT deflection calcs (as does current engineering theory), but from what I know all will work to industry standards.

 

[Trenno]

+1 for both RAM Concept and RAPT. When used in conjunction, your design should be tip top.

 

[rapt]

calvinandhobbes10

I will disagree with you on current engineering theory on long term deflection calculations. The implementations of the theory in some software are often lacking to non-existent, but that is not the theory's fault. And design code simplifications are woeful, but that is because they are simplifications. many programs simply use uncracked short term deflections, some use factored cracked short term deflections. A few try to do it properly and allow for loading stages, cracking, tension stiffening, creep and shrinkage.

If you are doing RC design, the best calculation in lieu of a full long term analysis is short term uncracked * 6.

For PT there is no best guess, even though some software bases deflection results on a guess!

If you want the latest theory get Gilbert and Ranzi's book on long term effects in concrete.

Any software that uses long term multipliers like "2" with a compression reinforcement factor is effectively useless for RC design and does not apply at all for PT design.

One area that causes problems for me with deflection design is the extra deflection caused by redistribution in yield line design, which no one accounts for. But again that is not a theory problem. Design methods such as banded/distributed flat slabs rely on yield line solutions even though designers treat it as a normal flexural design. And it requires a lot of redistribution to make it work.

 

[calvinandhobbes10]

Rapt---sure, theory of LT deflection is becoming more robust and inclusive each year, far beyond the reach of codes. Lots of solid resources out there. This is a topic I'm very interested in, have considerable experience with, and I appreciate your comment.

However the precision of LT deflection predictions (my primary experience is with flat plates) varies widely due to the multitude of variables and unknowns---age of concrete, placement, atmosphere and curing, stripping/stressing schedule, etc etc. (Construction sites, not controlled research labs.) Throw in the variability of finish/partition sensitivity (the most likely problem) and it becomes very challenging to channel the best theory and research towards an appropriate standard of care.

I listened to a RAM Concept webinar last year---don't have a link unfortunately---that suggested the statistical correlation of theory-based LT elevated slab deflection to measured values is something like 60% confidence level. They used this as the poll question to illustrate the wide variation in observed performance. This is consistent with my experience of LT deflection problems---some (many) underdesigned flat plates work fine, some (mildly) overdesigned ones can still have issues. It often comes down to the finishes, partition head details, and of course occupant sensitivity.

For RC I have used 4 * initial cracked dead-load (also understand 6*D+L) as a rule-of-thumb. I usually discount the initial self-weight deflection (forms stripped) with the ACI L/480 critical LT deflection limit.


In regard to OP question, either software product will have a guide for LT deflection, and despite the many limitations as rapt has noted (it will be evident as you walk through the guide), I recommend using it as ONE method of evaluation. Compare it to go-bys, run it by peers, etc. For other design needs (reinforcing, punching shear, moment diagrams, etc) all three programs can do this well. Your challenge will be applying it to eccentric-bay layouts that are so common, so I say learn an interface and stick with it. If you have RAM already, you may be able to bargain a deal in the licensing fee.

 

[SethGuthrie]

The webinar link calvinandhobbes10 was mentioning.

http://pages.info.bentley.com/event...ventGUID=bc0fe89f-0c19-4101-9011-cd3af420cfa8

for anyone who is interested.

 

[IDS]

A bit off-topic, but an important point following on from the comments of calvinandhobbes10:

It seems to me that the real elephant on the beam in deflection calculations is the effect of differential temperature, which no-one seems to talk about much, but has an effect of the same order of magnitude as shrinkage and creep, and has a huge degree of variation, depending on the location and orientation of the surfaces with maximum tensile stress.

In the Australian codes, allowing for temperature effects is specifically mentioned in crack control provisions, but there is no mention of the effect on the cracking moment in the deflection provisions. As far as I know there are no specific requirements for allowing for differential temperature when calculating the cracking moment in other international codes either. It is also rarely mentioned in research reports, or design examples. Given the magnitude of the effect, this all seems very strange to me.

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/

 

[rapt]

IDS,

The code says Temperature effects should be considered. So designers can include them in the calculations for cracking etc if they want to. Simplified code rules can never allow for something like this. The effect would normally only be on roof slabs.

calvinandhobbes10
Yes, there are a lot of variables. So if you want to get really detailed you need to investigate a lot of different load conditions, construction sequence, variations in material properties (Ec of concrete could vary by +-20 or 30% for a start) etc.

But the methodology is there if you want to go to those extremes.

I had one case where a consultant measured the deflections in the same panel on every floor of a 30 story building after about 30 years. Deflections varied from about 55 to 85mm on different floors. Average was 67mm. RAPT fluked it with 66mm! But the point is with one calculation using average properties and loading conditions you will get the average deflection. Real deflection could be +-20%. You cannot expect better from an average calculation. But it is better to know that you are within +_20% than not know where you are which is the are with simplified code methods, especially L/D checks but also long term magnifiers..

Same for crack control. We are only ever calculating an average crack width, not the real crack width or the maximum.

 

[IDS]

The code says Temperature effects should be considered. So designers can include them in the calculations for cracking etc if they want to. Simplified code rules can never allow for something like this. The effect would normally only be on roof slabs.

It doesn't say anything about temperature in relation to calculation of deflections:

8.5.2 Beam deflection by refined calculation
The calculation of the deflection of a beam by refined calculation shall make allowance for
the following:
(a) Cracking and tension stiffening.
(b) Shrinkage and creep properties of the concrete.
(c) Expected load history.
(d) Expected construction procedure.
(e) Deflection of formwork or settlement of props during construction, particularly when
the beam formwork is supported on suspended floors or beams below.

Any element that is exposed to direct sun is potentially affected, which is a lot more than just roof slabs, especially when non-building structures are included. Even in multi-story buildings there will be many elements exposed to direct sun during construction, which is all it takes to substantially reduce the cracking moment.

In my opinion differential temperature is one of the main reasons for the large range in actual deflections, and is just as significant as variations in shrinkage and creep, quite possibly more so. It should be included in the list of things to consider in a "refined calculation", as item (b) or (c).

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/

 

[rapt]

Doug,

Why does temperature differential need to be nominated specifically. It has an effect on cracking as do other loads, restraints and a lot of other things. So it is covered by (a).

Maybe the fact that engineers do not consider it is another matter. But most do not consider the effects of restraints to shortening and a lot of other effects either. That is not the codes fault. It is not a design manual or a text book.

You would be amazed at the number of designers who still do not think they need to consider restraint to shortening by metal decking. Or differential shrinkage due to the presence of metal decking on one face of the slab. In PT slabs, it causes significant increase in deflections.

I Australia, for RC members, the extra cracking will be at the bottom at mid-span for members that are nominally uncracked at service loads. This is covered in AS3600 by the Ieff <= .6 Ig rule.

For PT members, there is normally extra cracking at the bottom at supports, but this will not affect deflections as it is in compression under full loading for deflections. We still recommend using the Ieff limit for PT members for effects such as this and external restraint, unless the designer is going to do the full calculations to justify using a higher value of Ieff.