Rebar versus strand comparison 2

[maddog67]

I was hoping someone could give me some information regarding the posssibility of substituting 16mm rebar in
a cantilever with 9.3mm strand . I am told that it is possible , in this application of a hollowcore slab , but I was hoping for some other opinions . To achieve similar properties to that of rebar , would the strand have to be prestressed ? Any help would be welcome

 

[dik]

If I understand correctly, you want to substitute strand for reinforcing.

Assuming that the strand is at least stronger than the rebar, you should be able to substitute equal areas for equal areas. You have to concern yourself with concrete bond to the strand and be comfortable that this is OK. If you are trying to use strand that has a much higher yield than rebar, then you might want to consider using high strength dywidag bars or something similar. Problem sith strand is that it is often high strength, ie. has a lot of 'spring' to it and it often has a 'built-in' curvature that may be difficult to straighten.

Dik

 

[rapt]

maddog67

If you are substituting each 16mm rebar with 1 9.3 mm strand, yes it would have to be prestressed.

If you want to do a straight substitution without prestressing you would have to substitute an equivalent area. Also, strand has very bad bond properties compared to deformed bars. You would also have to look at this.

You cannot generate the full breaking strength of strand if it is simply used as untensioned reinforcement so you cannot substitute it on the basis of equivalent yield force. In fact, even as prestressed strand, you normally cannot generate the full breaking stress of the strand, normally only about 95%. But as unstressed you will only generate about 30-40% maximum. A strain compatibility analysis is required to determine how much stress you can generate in the strand in both cases.

So, no you cannot substitute it, you can redesign it using strand but a full redesign is needed.