ACI 318-99 1

[kronosconcrete]

I'm curious how many out there understand like me that post tensioning is the future of concrete. The increased spans up to slab thickness X 45 and resultant lighter weight seems to make this a no brainer.
I wonder how much implementation is held back by lack of knowledge with the new Code requirements. Working with two sets of moments from load and secondary post tensioning makes for a lot more steps. There are also simplicities. It seems to me that the extra analysis would make computer modeling more difficult, if not unfeasible. Maybe this is completely wrong.
If one wanted to implement post tensioning technique into residential construction, how difficult would it be to find competent engineering design. My experience has shown that most structural engineers will result to a massive overkill with little effort made to understand and implement Code requirements.
For experienced concrete engineers, is this Code stuff easy or difficult. Just curious. Thanks.

 

[ishvaaag]

I think the whole thing about proper consideration of PT is complicate. What maybe easy are some subsets of the technology. PT amounts to the controlled input of inner stresses in the more variegated way, and this itself is a challenge to proper modelization. In the same way that happens with prestressed-precast parts, the use of the more popular soultions is practical yet uses to come in the form of simple structures, some of them enteering a variable of discontinuity very uncomely to the life of any built structure.

In some cases, and except for the complete and expert teams some effects, as important as the likelihood of calculable and less calculable prestress loss may go unattended. When used for important structures it raises the knowledge entry, so must be and is, because one then has to properly deal with variation of stress along time and temperature, with impredictable creep and shrinkage, which if you misconsider may lead to some stunning things. Even in major bridge structures built by cantilever loss of stress in the weakly joined centers has caused the loss of the bridge, and assuredly the designs were made by what the owners were thinking were competent teams. So all these things and many more that one might continue quoting is what make something complicate: you have a lot of things to consider, and your array of tools is usually incomplete or even if it is complete does not describe properly what you are to tackle.

Hence, the generalization of these technologies will be in accord with the generalization of knowledge and design tools that provide understandable and complete solutions for the particular problems they are targeted for.