The basics of post tensioned concrete design | how to design post-tensioning
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- เผยแพร่เมื่อ 24 ก.ค. 2024
- Post-tensioned slabs are common construction for commercial and high rise construction.
It is critical that all structural engineers understand post tensioned concrete design. within this video I will be covering the basics on post-tensioning design:
- How much post-tensioning should you have
- general design considerations
- minimum and maximum requirements for post-tensioning
- how to design an efficient post tensioned slab
- Sizing of post-tensioned slabs
Prestressed concrete and Post-tensioned concrete share the same benefits, by overcoming concrete greatest weakness.
This will hopefully help you to start to unlock the power of post-tensioning.
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Awesome video Brendan! There was a lot of new information there I had never come across previously or thought of. Cheers!
Him Tig K, thanks. Glad you found it helpful, hope it helps with your post-tension design. If there is anything else you would like me to cover let me know.
@@BrendanHasty I'm working in the industrial sector so not a lot of PT design, although I did one project to assess an existing PT slab on ground using RAM concept
Thanks for the great video. I don't do PT design but it's obviously a big part of modern structures that I want to make sure I have the basics understood.
Used this video as a re-cap, and I honestly think I learned more in this 15 minutes video than half my course at uni! Thanks again.
Good work Brendan. "Basics" but thorough and not off point. So good seeing structural engineers giving back. From a PT designer in Melbs.
Hi Kevin. Thanks for your Comments, hope you found it helpful. I tried to include all the key points most of the key design principles.
Great video about PT, plus bonus content of the pour joints!
thanks, glad you liked the video
Thank you Brendan. I just realised I have missed this video last week.
Can you please make a video on different types of structural joints ? How do we decide when to use temporary/permanent joints ?
Really appreciate your effort and time.
Glad you are finding them helpful. I can make a video on that, and thanks for letting me know what videos will be helpful.
Thank you Braden! We are learning from you.Glad to know you are from Austrelia.Waiting for more video.Regards.
Hi Bunbun, happy that you are learning from my videos. thanks for the support. my next video is on PT likely similar to this one but better.m
Thank you, very helpful points. I would recommend for any one that least experience with PT to watch this video.
Hi Cameron, glad that you found it helpful. Thanks for the support.
The PT master strikes again :) Bravo Brendan
Thanks, glad you linked it
As a PE in the states, it’s hard not to notice that 70 year old Seelye on your shelf. Keep it up!
Hi K A, it is a good book still and also looks good on the shelf. thanks for the encouragement.
Great video Brendan, the way you present it makes it easy to understand. More power to you.
Also, if I can request you to make a video on how to read structural drawings from scratch that can also include the P/T as well. At last, thank you so much for making this video and spreading the knowledge.
Cheers
Hi Anubhav, Happy you found the video helpful. I will see what i can do, I defentally think that reading drawings is really important. This is something that isnt covered at University, Or wasn't when I wasn't when i was at Uni.
@@BrendanHasty sir any lecture available on TH-cam for post tension concrete subject
Awesome video, very knowledgable.
Is there any chance you could make a video regarding slab joints preferably for suspended slabs? I.e., TMJ's, PMJ's, construction joints, etc. It would be good to also explore why TMJ's are located between in-situ walls and slabs.
Thank you.
Super helpful thank you
Thanks for the support
@brendan thank you for the very informative video. Could you please explain a bit more of the drape in cantilever? It's still unclear for me of how secondary effects work
When a beam deflects, it has a tension side and a compression side. The side deflecting needs to lengthen to allow the beam to deflect of you compress that side it will resist the deflection to some extent, the compress side still shrinks so it doesn't prevent the beam from deflecting.
Thank you
Great vedio...keep up
With the good contents....newly subscribed your channel and really admire your work.
👍
Hi Hatem Diab, thanks for your support. any topics you want me to cover let me know, hope to impress in future videos.
Awesome video Brendan
Are you able to cover permanent/temporary movement joints in future? I guess slab shrinkage in general and the absolute limit.
Some engineers believe if you have a high degree of crack control (loads of reo) you can get away with no pour joints/movement joints..?
Especially where there's two stiff elements such as cores apart in a slab, I've seen no joint introduced in between.
Hopefully you have time to cover this in future. Keep up the great videos
Thanks, Tony, hope to keep up the quality. yea permanent/temporary movement joints can be a topic on it own. I will put it into the list, it can be an interesting topic.
Very informative video, thanks B.H...Just wondering if you could help with info on approaching design strips for flat plates in RAM concept. Thank you.
Hi Emmanuel, I will be putting together a video on modelling tips. but the easy way to think about it if you were to check the design in a 2D design software like Rapt where would you put these strips, that is where you should put them.
Great video, but it'd be even better if you talked abit slower and extended your pauses slightly.
Thanks Ulysses, really appreciate the feedback and will be something I will work on. Any other feedback would be greatly appreciated. Also, happy you enjoyed my video.
Lessen the speed
What pauses ?
thank you really useful
Thanks for watching Kimmy
Thank you sir. easily understanding . Intangeble service sir 🙏.
Hi JK Nayak, glad that you found the video helpful
Hi, Mr Brendan. Will it work if i use 25T car hydraulic jack for T beam pretension that uses 5mm wires. Thank you.
Good video mate. I have always found one-way PT relatively simple with the use of RAPT but am at a loss with how to use it for 2-way application. Not all firms have access to RAM Concept as its quite expensive. PTD from inducta is available but feedback I here is that it can be quite cumbersome. Would a video on the use of RAPT to design a 2-way PT slab be possible?
Hi Anthony, Rapt is amazing I can do a video on this there are several way this can be done.
A great video!!
A quick question regarding the P/A stress. Does AS3600 have a minimum and maximum value for this?
Hi Harrison, thanks.
AS3600 does have a maximum P/A based around the strength at transfer(when you stress the tendons) which is around 3-4. However, when you start to exceed 3MPa you start to have shortening issue with the slab.
As for minimum P/A's there isn't really a minimum the lower your P/A the more reinforcement you require for crack control, the required crack control is specified in CL9.5.3.4, which is related to the service requirements.
Glad you liked the video, and if there is anything you would like me to cover in the future let me know.
I did my master thesis on a new design method of prestressed concrete structures trough equivalent load method. Prestressing is bae😍
Thanks for sharing, also appreciated the support
@@BrendanHasty you are doing great job Sir.
Is it still efficient to use load balancing method?
Hi Kindly which book do you recommend for PT Slab design?
Does deck level at middle of girder is also increased because while doing post tensioning the girder forms camber in middle portion(Hogging).So should we increase the deck depth as girder is lifted up in middle?? What is the correct process?
How does truncating of tenons work? Say if we were to cut an opening in a PT slab. What additional bracing is required for this to occur?
Hi Stephen, truncation is like a dead end anchoring the tendon. You need to truncate the tendon prior to cutting the slab. You will also need to assess the slab if the new void causes issues.
good video, but still you need to say something tendon arrangement in banded/ distribution, as far i know in australia bonded tendon uses instead of unbonded where undonded use in USA. it will be more useful if you show us a simple example of post tension slab design in australian standard.
Hi Roy Jack, you are correct we only used bonded tendons in Australia, I can put a video together show a simple post-tensioned design to Australian standards.
Elongation and chair height calculation software names please
Awsome. Helped me a lot. Can you please make one PT slab design example in Ram or any software? Keep going.
Hi Deepak, I am glade that it has helped you, will deffentaly go into some design tips on rapt and ram.
@@BrendanHasty thank you
Could you plz let know what's the min span required for post tensioning to be a viable option. Can it be done over a 5 ft span beam
minimum PT is about 6 meters which is around 20 ft
At 10:34 in the video your application of "K" is interesting. I use a similar concept for mild reinforced concrete. Me being in the US I would like to know the units in those terms so I could do a conversion to the units I work with and see how it compares. I assume since you are talking about PT that the bending moment is at service load level.
Hi Bill welcome, thanks for all your support and comments it is greatly appreciated. The moment are ultimate loads, k = M/ B D^2 so you just need to maintain your units if moment are Nmm B- Is width in mm and D - is depth in mm. It is a modification of M/Z (Z-section modulus)that leads to an easy number to aim for, so I would guess there should be a similar relationship. Let me know your findings.
@@BrendanHasty I just found your video and it is very useful to me that just involve in PT design. I have do some research on this K=M/BD2, but I can't find any reference talking about this, saying K=3 or 5. Can u please elaborate more on this matter. 😀
@@BrendanHasty i was wondering if fcu is missing ....k = M/ fcu.B.D^2
@@chilotberassagarsamo2340the 5 value is for ta concrete grade of 40mpa
sorry should have noted that, so if you have a different concrete grade it is just 5*(ratio change)
The term Centroidal axis should be used in PT calculation. Neutral axis is dependent on the load applied
Thanks for the correction.
Is it natural if you are using post tensioning that your floor experiencing vibration?
If not designed correctly it is easy to make a post tensioned Slab bouncy by adding too much post tensioning, not really wrong structurally just doesn't meet service conditions
Amazing videos Brendan. But please talk a bit slower for non native speakers.
Hi Osama, thanks for stopping by and your free back. This is something I will work on, Glad you found the video informative and hope to produce better videos in the future.
The other concern is regarding the lack of anti-seismic design and construction for post-tensioned high-rise buildings in Australia, according to NCC and all relevant Australian Standards, anti-seismic design and construction are not compulsory just due to the perception that Australia is not riddled with earthquakes like our neighbor New Zealand. However, the truth is Australia is not an earthquake-free-country. For example, the deadly 1989 New Castle earthquake is a sad disaster, that has exposed the truth.
Hi Xero, Seismic design is the past have been poorly defined in Australian Standards. However this has changes with the revision to AS3600-2018 making the requirement more specific and requiring diaphragm to be design as a non-ductile structure. I agree that Australia does not have enough records to know potential risk for earthquakes many cities may be sitting on major fault lines.
As both a structural engineer and a licensed builder, I have to point out that currently, most builders in Australia are to be blamed for their horrible workmanships on post-tensioned concrete structures. To be specific, most Class-2 buildings are constructed with horrible workmanships by these dodgy builders.
There are dodgy builders, this has risen due to Design and Construct contracts. Everyone is chasing the cheapest price.
Very informative, but please slow down - you are talking extremely fast and it's hard to keep up. Thanks!