Calculating deformations due to Creep
Calculating deformations due to Creep
(OP)
Hi guys,
I posted a similar thread in the precast/prestressed forum but it doesn't seem to be getting any replies.
Basically I have a prestressed concrete bridge girder that hogs 30mm (1.25") at transfer. The concrete strength at transfer is 40MPa (5800 psi).
What I want to calculate is the hog after 28 days, assuming the girder sits in the stressing yard for this time. When calculating deformations due to creep and shrinkage, should I reduce the Young's modulus to account for these two phenomena. Or is there another model that is generally accepted throughout the industry, if so, can someone please provide me with a reference paper/text. I think I may need to account for some concrete strength gain and pretension losses when calculating the deformations at 28 days.
I posted a similar thread in the precast/prestressed forum but it doesn't seem to be getting any replies.
Basically I have a prestressed concrete bridge girder that hogs 30mm (1.25") at transfer. The concrete strength at transfer is 40MPa (5800 psi).
What I want to calculate is the hog after 28 days, assuming the girder sits in the stressing yard for this time. When calculating deformations due to creep and shrinkage, should I reduce the Young's modulus to account for these two phenomena. Or is there another model that is generally accepted throughout the industry, if so, can someone please provide me with a reference paper/text. I think I may need to account for some concrete strength gain and pretension losses when calculating the deformations at 28 days.





RE: Calculating deformations due to Creep
I think the data in RAPT can be adjusted to do this for you.
RE: Calculating deformations due to Creep
The 28 day hog should be around 1.6 x transfer hog.
RE: Calculating deformations due to Creep
RE: Calculating deformations due to Creep
Can you please be more specific on how to alter the data so I can calculate the hog at 28 days.
RE: Calculating deformations due to Creep
Mike McCann
MMC Engineering
RE: Calculating deformations due to Creep
RE: Calculating deformations due to Creep
RE: Calculating deformations due to Creep
I have been using the term "hog" referring to the upward deflection due to prestress.
RE: Calculating deformations due to Creep
Sorry,
I have not been monitoring Engtips for the last 6 weeks as I have not had good internet access available while travelling.
Why don't you email your questions to me directly trather than through the forum?
RE: Calculating deformations due to Creep
RE: Calculating deformations due to Creep
Thanks for the help by the way. We sent the design out late last year. I still would like some reference material on the topic for my own eductation.