Length of rebar to recover from old bridges for tensile testing

[kww2008]

I came across reports of previous tensile testings which used rebar lengths of approximately 3 feet (0.914m). Any idea why such long lengths were used since the gauge lengths of the extensometer were much shorter? I suspect it has something to do with elongation and wonder if someone can shed some light on this. Furthermore, if one has to recover bars from an existing bridge for testing, one would like to keep the bar length to a minimum.

 

[concretemasonry]

What are the nationally accepted standards for sampling and testing?

Representative sample based of the effects of the locations and exposure? Bridges go through a lot of highly variable loading and weather conditions and situations.

The results are needed for determining the performance of the structure itself and determine the reliable structural strength and not just to make testing easier or faster.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[bridgebuster]

This is from A370


A9.3.1 Test Specimen—Specimens for tension tests shall be long enough to provide for an 8-in. (200-mm) gauge length, a
distance of at least two bar diameters between each gauge mark and the grips, plus sufficient additional length to fill the grips completely leaving some excess length protruding beyond each grip.

 

[ImminentCollapse]

We've had tensile testing performed on rebar we got out of a 4" diameter concrete core, I don't recall the short length being an issue. Talk to your test company to see what they can do.