LRPC High Tensile PC Strands

Sounds like a homework assignment.

yes sure this is..........share if you have some idea about it.

The main idea I have is that you should do your own research. It is all part of the process of learning. If you have specific questions about some aspect of the subject, then ask...I expect CR4 members would be pleased to help. But don't expect CR4 to do your work for you. CR4 is not a homework cheat site.

nice to listen from you.just tell me what is pre-stressed concrete?and how the use of strands inside it is responsible for the long life of structure?

I cannot begin to tell you all of the ramifications of pre-stressed concrete in one short message. You ask "what is pre-stressed concrete"? The answer to that may be found on hundreds if not thousands of sites on the internet. You should learn to use google.

The primary difference between pre-stressed and conventionally reinforced concrete is that, in the case of pre-stressed, the reinforcement is elongated prior to load application whereas conventional reinforcement is simply waiting for something to cause it to stretch.

There are two types of pre-stressing, namely pre-tensioning and post-tensioning. In pre-tensioning, cables are stretched between fixed ends and concrete is cast around the cables. When the concrete is strong enough, the tension is released, the members removed from the forms and then shipped to the jobsite. This would be the case for single tees, double tees or hollow core slabs.

In post-tensioned members, the cables are placed in ducts. Concrete, supported by formwork, is poured around the cables and, after the concrete has gained sufficient strength, the cables are tensioned by jacks and tied off at each end so that they maintain most of their tension prior to service loads being applied. This would be the case for post-tensioned slabs and beams.

So far as the "long life of the structure" is concerned, pre-stressed concrete cannot claim any particular advantage over conventionally reinforced concrete. As a matter of fact, if the structure is post-tensioned and the ducts are ungrouted, the post-tensioning strands are subject to corrosion if water should accidentally find its way into the duct. They are also subject to stress corrosion.

If long life is important, and I am sure it is, the post-tensioning cables should be grouted, creating a bonded system. In my location, unbonded systems have caused so many problems that financiers for new construction are asking for engineers to certify that there are no prestressing strands on site before they will commit their money to the project.

Prestressing is an excellent system, but there have been so many mistakes made in the past that many people have been discouraged from using it. It all takes time, I guess.

I was in need of that Bruce.........so please tell me calculation of the load given(or how much extension is needed) to the strand at the time of pre-tensioning or post-tensioning.