Interview help - post tension design using hand calculations 5

In the UK you will need to be familiar with the Concrete Society Technical Report No. 43: Post-tensioned concrete floors.

Thanks mate.. any particular questions you can think of?

Not meaning to judge but it seems like you're applying for a job you're not currently qualified for. While you can certainly learn on the job and study outside of work, do you feel you're able to take on the responsibilities they'll be needing from you?

I'd learn about jacking procedures, transfer design stages, and prestressing losses; to name a few problems they may ask. Some other aspects might be various steps in checking capacity or whether the member remains uncracked. I'm familiar with the US codes so I can't help with any specifics beyond just generalizations.

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

At an job interview (many decades ago when I had about 3 or 4 years of grad experience) with a PT company in their design branch/office, I recall being asked by their chief engineer to discuss the steps to design a PT flat slab (nothing too difficult: selection of slab thickness, check punching shear, select load to balance, flexure, deflection etc), and then hand calculate the 'balanced load' for a given tendon drape and prestress force for an internal span of a beam. I had done 2 or so courses of undergrad prestressed concrete subjects at uni so they questions were not really a big deal.

I got the job, but I will say that it was "balls to the wall" upon starting on the first day. Thrown some interesting, multiple, fast-paced projects in the first week!

Not wanting to turn you off - but if you do go past the interview phase and land the job, I am going to assume it will be fast-paced from the get-go. If you don't have the fundamental basic understanding of PT, they may not be willing to slow down and train/mentor you.

Design software has (unfortunately?) changed a few things over the years, on what you can 'get away with' on assumed-knowledge.

Did you take a class at uni on prestressed concrete?

Are you in AU or the UK?

Thanks Ingenuity, i was working in the UK, i just moved to Aus and post tension jobs seem to be very hot here.
I understand the risks of a new job, but i can either sit at home dreaming about an ideal job Or work hard and make use of a given opportunity. Hopefully i should be able to manage will try to study what you have mentioned..
any particular study material u propose other than TR43 (Concrete Society Technical Report No. 43: Post-tensioned concrete floors)?

sparta7963,

Since you are currently in AU I would grab a copy of one or both of the following AU underdrad text books on prestressed concrete:


Available from most uni bookshops.

Even if you get an older 2nd-hand copy of Warner/Faulkes book (late 80's or early 90's edition I think), that has some good practical design info that will be an advantage to you at minimal cost.

The second text does a better treatment of the theoretical aspects of prestressed concrete (especially creep, shrinkage, deflection etc), but the first text has some good info for practical design of slabs and beams: step-by-step procedures and design examples.

And forget about UNbonded PT - AU is all bonded/grouted PT.

All the very best to you.

Also - if you want a heads-up on PT software in AU - most (all?) consulting companies in AU (and beyond) use RAPT ( and if you go to their website I think there is a trial download where you can take it for a spin. The author and owner of RAPT visits here at Eng-Tips frequently, so hopefully he will chip in too.

In your first post you said you were in the UK but now you are saying you are in Australia? If you are in Australia then TR43 is not in wide use although it is still worthwhile to read through.

The RAPT manual is a good resource (all 740 pages of it!). There is good discussion on preliminary sizing, load balancing and level of prestress in the beginning of the "Theory" section.

Sorry, I am with TehMightyEngineer on this one. if you have absolutely no idea on how to do PT design, bluffing them into thinking you do is not the way to go in my opinion. If they know what they are doing, they will pick it very quickly and then you have no chance.

If you really understand concrete design, convince them of that. The step up to PT design is not that large if you understand engineering, structures and concrete design (and I mean understand, not just know how to design an RC slab using software). By all means read the books to get started, but I would be honest. They will not expect many people coming from Europe to have much building PT experience.

thanks for the honest reply guys. I have around 5 years of experience in reinforced concrete and steel structures and i have mostly done multi-storey residential buildings, some industrial buildings and warehouse structures. I am not very experienced with PT design but however the job requirement is not very high i guess, more like they are expecting a candidate with 1-3 years of experience.

From what I have seen in my job hunting, australian companies don't consider or value your experience outside australia (that what the ALL the job recruitment consultants told me and the salary offered for that position was between AUD$60000 - $70000). So i am guessing its more of a junior level position.

I feel that the obligations of the employer and candidate here are as follows:

Employer: vet you to ensure that they're getting what they need.

Candidate: chase down your dreams with as much courage and tenacity as you can muster.

If I could somehow convince NASA to hire me to train for the next manned space flight, would I give it a go? Darn right.

Must the next prime minister have previous experience being prime minister? Of course not. Many jobs are learned on the job. Meaningful personal growth usually requires reaching a little.

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.

TR43 would seem to be the best place to start. If you google VSL + post-tensioned concrete, you'll find a number of free - and relatively short - design brief documents. If you've got a bit a time to prepare, I'd recommend TY Lin's text. It's reasonably short and great for the fundamentals. It also has a number of simple examples.

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.

Isn't it all just P/A plus or minus Mc/I, and knowing at what times certain stresses apply? (Consider this an interview level response).

my 2c, don't over-sell yourself, but it's really good to show you've done some prep work ...
"I haven't done any PT projects, but I have reviewed some technical references ..."

I'd be interested in when to use PT beams, and why (are they used in those situations).

another day in paradise, or is paradise one day closer ?

I haven't read through the other replies (other than noting you've gotten some good technical advice) so pardon me if this has been said before but: whatever you do, be darn sure they understand what you can and can't do. It's one thing for them to quiz you or whatever.....but make clear: "Hey, however I did on the quiz, this is my first time at bat with post-tension design."

You just want them aware of your experience level......especially if they want you to come in and immediately stamp stuff (you may not be comfortable with that).

One of the best jobs I ever had was when I told the guy in the interview: "Your ad asked for [this or that skill]....here are some of those skills I have: [ ], and here are some I don't have: [ ]."

WARose said:

and immediately stamp stuff

Click to expand...

That won't be an issue - there is no PE/SE stamping in AU, per se.

Stamping/sealing is a somewhat unique North American "restrictive trade practice".

rb1957 said:

I'd be interested in when to use PT beams, and why (are they used in those situations).

Click to expand...

Is that you asking, rb?

If so: Typically, PT (and prestressing generally) is used to 1) accommodate larger spans at 2) less structural depth than non-prestressed members, with 3) superior deflection control due to the active 'actions' of eccentricity/curvature of the prestressing tendons, and 4) less cracking due to the effective P/A. Also good for fatigue resistance too - more appropriate for bridges than buildings.

+1 for the RAPT manual. Great reference, but it doesn't cover it all. Do some research on load balancing and Hall's graphical method.

Coming more from the practical perspective, I highly recommend downloading the material available from the Post Tensioning Institute of Australia.

[URL unfurl="true"]http://www.ptia.org.au/Downloads.aspx[/url]

In particular the 'Practical Prestress Detailing' guide. I've attached it for anyone too lazy to click the link.

And don't EVER do this!