Prestressing, Post-Tensioning, Pre-Tensioning

Prestressing, post-tensioning, pre-tensioning concrete
By Michael Ermann
For more, visit www.amberbook.com
Animation By Taylor Kuehm

[@hashtagvizag]

simple, neat and clear

[@Azadfekr]

Thank you Sir! Finally someone explained these in a simple way.

[@pillowmallow]

Kronk, is that you?! Just kidding. Great video!

[@simonforget280]

I believe the image at 2:55 is the walkway between both sides of the Orange line at the Bonaventure Station of the Métro de Montréal. I suspect that post tensioning was used for all stations of the Métro de Montréal, as per the Place Ville Marie project a few years before (Place Ville Marie is build almost on top of the Bonaventure Station). An example of concrete pretensioning is the Stade olympique de Montréal (Montréal Olympic Stadium). Most of the large parts were precast.

[@josantana01]

Great vid 👍🏼

[@wilson3360]

These videos are super awesome! I have so many questions. Who are you? How do you know all this stuff? Do you teach at Virginia tech? What do u teach? Have u written any books? How van I learn more about you. And more importantly please keep putting these videos out they are amazing!

[@kthjjk169]

THANK YOU VERY MUCH!!!

[@khalidalnajjar1558]

This is amazing .. why does it end all of a sudden is this like an online curse ?

[@bharathiraj.l.t1120]

super explanation clearly understandable

[@daniildimitrov7117]

Cool dude , cool

[@AleksandarGrozdanoski]

Why are comments disabled for the "How electricity works. . . . animated" video? And first and foremost why is the video cut...?

[@volchonokilliR]

I wonder which one is more expensive overall for some project - pre-tensioned concrete or post-tensioned... Even though I can imagine transportation of pre-tensioned concrete to be an issue, the amount of on-site work required for post-tensioning looks pretty big

[@martinpoulsen6564]

Fabrication in a controlled environment is always easier, and as a lot of parts in a structure are usually alike, you can use the same forms for several castings, with no to minor changes in setup in between. Sometimes that is simply not possible. There can be a multitude of reasons to build or not to build in situ, which can depend on infrastructure to, around and on site, availability - is there a great distance to travel from nearest provider, either for prefab or in situ building. How is the time frame? Is there a need for several contractors doing their work through the same time period? For a sealed structure the on site post tensioning method will almost always be of the highest strength, as you have no physical boundaries inside the structure, which means you can have uninterrupted rebar/cables and a continuous concrete pour, making it one unit, where prefab has to be joined, leaving joints. These wil create weaknesses in the structure, regardless if a crack should occur beside or in the joint. getting uninterrupted reinforcement is also problematic, as parts usually will be connected with bolts initially, and then have the joints sealed with either concrete or a flexible sealant. So deciding which way to go usually includes a lot of different considerations, as for instance, how big a truck will be able to reach the site? Does the structure need the full integrity of post tensioning, or will less do? Are there a lot of uniform sections, or is everything unique everywhere? Is it a smaller scale project, not involving a lot of people, materials etc., Is time a key factor (more important than money, in the sense that the finished result might be very profitable, and delays will be costly beyond any single components)

[@martinpoulsen6564]

...another very important aspect of prefab is that it can be commenced simultaneously with the ground work, so the up to month long set and curing times are not in the way of progress in the build. For very large sites, it can shorten the build time many times over, and also accommodate several suppliers, and again increase intensity, where an in situ build is restricted of the on site progression. One step will have to be completed before the next can begin. For skyscrapers and bridge pylons, there usually is no exception. They have to be as strong as can be, and so are cast in one continuous pour.

[@volchonokilliR]

@@martinpoulsen6564 Thank you for such a detailed answer! Point about post-tensioning method being of the higher end strength result is very good and informative. It's great how nowadays we can learn so much from reading KZbin comments under videos about specific topics

[@martinpoulsen6564]

@@volchonokilliR You are welcome. Just to clarify - post tensioning within the structure is not necessarily stronger than pretensioning. It is the joining of parts that make out the weakness, so if you can do something off site pretensioned in a controlled environment, that is a stand alone object, it might still be preferable over post tensioning, provided preparations are adequate. There will be a smaller margin of error, as liquid concrete will compensate for unevenness in the substrate... not so when it is set and hardened.

[@ujjwalkpatel]

3:39 , how do you know that tensioning will create only hogging shape, not the sagging shape?

[@AJ-jp1kd]

location of the tendon

[@donprefontaine3237]

You disabled comments in your "How electricity works. . . . animated" video so I am providing them here. At 7:18 you said the positive end has more electrons: not true. The negative end is the current source and the positive end is the current void - there are fewer electrons. The electrons at the negative end are greatly attracted to the positive end which effectively contains electron holes. The electrons move towards the holes to achieve neutrality. The greater the attraction, the greater the voltage. The greater the flow rate, the greater the current. This is electron current. Engineering describes this action but in reverse: the holes move towards the electrons which is what they call hole current. Do they really? Of course, not. But it does allow them to use positive numbers in calculations which simplifies formulae substantially. Today, we call hole current, conventional current. So... to review: the negative end contains more electrons than the positive end. Please consider adding a text block to correct the misinformation. Reference: Basic Electronics, 4th Edition, by Grob. ISBN: 0-07-024923-7. Thank you.

[@ophello]

Stop making me hit pause. Just do your video!