thermal effects on modulus of elasticty of strand 1

[spagetti]

It may be all in my head but, over the couple of years I have been stressing at a precast plant, I have noticed that the same bed (self-stressing),strand quantity and location, strand jack, (actual) kps value at the strand jack during stessing operations, and for all intensive purposes reletively equal modulus of elasticity between strand reels. leaving only ambient temperature as a variable, the elongation on hot days can run to the high end of the elongation tolerance while cold winter days it will run to the low end of the tolerance. we calibrate our strand jacks every 6 months as required.
Givin that modulus of elasticty at the manufacturer level, is calculated under controlled conditions, at what temperature difference is there, if any, a calculatable change on ME for the end user.
If there is a measurable difference and I am stressing to within 75% of yeild, is it possible to over yeild the strand (when more than 80% of yeild is considered over yeilding).
Especially in conditions where, tensioning is done with a 10 deg. ambient temp. and conrete being placed at 85 to 90 deg. on an abuttment form at 75% of yeild.

 

[JAE]

Here's a table I found. Not sure if it answers your question:

http://www.engineeringtoolbox.com/young-modulus-d_773.html

 

[civilperson]

When calculating the elongation for the strand, temperature should be included. A 400 foot bed will vary 1 1/4 " for a fifty degree temperature change. The Modulus will be accurate for the range of temperatures encountered in ambient air.

 

[spagetti]

JAE , thanks for the link it should get me the information I am looking for. if not I will keep looking.

Civliperson, thanks but I am not calculating elongation. I am looking for what deviation in ambient temperatures causes a measurable change to the modulus of the strand.