What are the differences between pre-stressed, pre-tensioned and post-tensioned concrete? In the fields of applying and possibilities of their usage individually.
In addition to that general query about the general perspectives; what are the pros and cons of applying each? or in other words what are the possible purposes of post-tensioning or pre-stressed concrete. Are there limitations, advantages and/or disadvantages of applying each of these techniques?
Another question could be what will happen if a post-tensioned member, will play the role of a compressed-member(let's say in a cyclic loading condition), and the load exceeds it's pretension primary condition?
Om Prakash Chhangani
Thank you for sharing your insight.
Actually this is a question of Material Science eg , concrete and Strength of materials ie
tensile strength .
Prestressing is a technique in which member is provided force in such a way to introduce reverse stresses opposite to what will develope when structure is subjected to actual load. In this way we can increase the load carrying capacity of structures.
Pretensioning is a method in which tendons are stressed and passed through the members mould at given profile.Concrete is poured in the mould and allowed to hardened and tendons are cut from both the ends of the element thereby the force is transferred to member.
Whereas, post tensioning is a method wherein ducts are left in the concrete element and tendons are post tensioned against the concrete member after its hardening by passing tendons through the duct and anchoring them as per various practices. Post tensioned member may be bonded or unbonded.
Thank you Dr Om Prakash Chhangani for the answer and helpful definitions.
Dear
I agree with Dr. Om Prakash, Pree stress means applying external tensile stress to the tendons in the form before pouring the concrete, after specified curing period the external tensile stress is released and the concrete unite will exhibit a slight concave down appearance indicating preestressing. on the other hand, post tensioned concrete means applying external tensile stress on the tendons after curing of concrete unite.
I would appreciate dear Professor Saad Sarsam for the answer. May you please also help me to find my other doubt asked at the end, i.e.:
Another question could be what will happen if a post-tensioned member, will play the role of a compressed-member(let's say in a cyclic loading condition), and the load exceeds it's pretension primary condition?
Dear
Prestressed or post tensioned concrete members are usually beam, girders or slab unites. All of them are designed to experience and resist tensile stresses.
Dear professor Saad Sarsam . I do agree with the mentioned examples of usage; however, we may consider it in a special case-study, that will be inevitably induced to cyclic loading procedure, i.e. foundation of the wind turbines.
Pre-stressed concrete has shown good behaviour in case of fatigue and cyclic loading as the stresses are not varying vis-a-vis reinforced concrete member wherein due to load stresses will reach permissible values and will be theoretically zero for no loads. or will be less due to Dead Load only.
I suggest you read book by Edward Nawy on Prestressed concrete
Thank you very much dear professor Om Prakash Chhangani , for all the complementary and perfect and helpful comments and also for the recommended book. I have started to study "Prestressed Concrete, Analysis and Design, by Antoine E. Naaman". Surely I will start to study the mentioned book by Edward Nawy too.
You may also read the legendary book by T Y Lin considered as father of the subject in US though Naaman book is equally good.
Pre-tensioned and post-tensioned concrete are types of prestressed concrete, i.e. the concrete members are stressed prior to imposed loads being applied. For pre-tensioned members, the steel strands are tensioned before the concrete is cast. For post-tensioned members the steel strands are tensioned after the concrete has hardened.
Try a Google search for the pros and cons of both systems.
The usage of Pretension and Posttension depends on the application. For example, pretensioning is preferred for applications like railway sleepers, etc. Depending on the application you can fix the method. However, in terms of loss of prestress, posttensioning results in less prestress loss than that of pre-tensioning. You may refer to NPTEL website for more information on prestress and losses of prestress. Hope this helps.
https://nptel.ac.in/courses/105106117/8
As mentioned earlier by other experts, please refer to TY Lin for better clarity.
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