Cervenka Consulting Forums — prestressed hollowcore

Re: prestressed hollowcore

null@example.com (dpryl) — Tue, 14 Dec 2010 11:17:19 +0000

Hello, zero stress at the ends sounds like NOT having perfect bond... anyway, the easiest way to get this is to define the bond properties and apply a constant temperature.

Re: prestressed hollowcore

null@example.com (melted) — Mon, 13 Dec 2010 21:52:30 +0000

Hello

The stress in the wires is zero at the ends of the slab and it increases over the transmission length to the initial pre stress. My question is how can I model this?

Thank you for your patience

Re: prestressed hollowcore

null@example.com (dpryl) — Mon, 13 Dec 2010 12:41:08 +0000

Hello, I am not sure if I understand the question?
To display the resulting stress in the wires, just display 1D results and select the stresses (X direction) for display.
To calculate the right amout of "thermal" strain to be applied, just divide the stress with the reinforcement elastic modulus (of course, if you have to consider prestress losses due to shrinkage, and do not wish to apply shrinkage as a separate load, youhave to reduce the calculated pre-stressing strain to reflect the losses).

Re: prestressed hollowcore

null@example.com (melted) — Sat, 11 Dec 2010 18:56:42 +0000

Hello
Thank you for the help. and Iâ€™m wondering how the thermal stress distribution on the prestressed wires is.

Thank you

Re: prestressed hollowcore

null@example.com (dpryl) — Mon, 06 Dec 2010 08:48:39 +0000

Hello, in this case, applying initial strain to the reinforcement is the best way. In ATENA Engineering 3D (unlike ATENA Science-GiD), initial strain can not be defined directly for reinforcement bars. I recommend the following "trick": apply cooling (i.e., negative relative temperature) to the prestressed wires. Set the thermal expasion ratio and the temperature to get the right amount of prestressing in each wire.

Re: prestressed hollowcore

null@example.com (melted) — Fri, 03 Dec 2010 22:13:12 +0000

Itâ€™s the first one( pre-tensioned bars/wires - concrete cast over wires fixed outside) .
The slab made on long-line casting beds which can be 200 m long then it cuts according to the project.
In my case 6 m long .
Iâ€™m using ATENA 3D VERISON 4.2.5.3252

THANK YOU

Re: prestressed hollowcore

null@example.com (dpryl) — Fri, 03 Dec 2010 08:43:00 +0000

Hello,
from your question it is not clear if you have
a) pre-tensioned bars/wires - concrete cast over wires fixed outside, as used, e.g., for railway sleepers
b) post-tensioned cables - cables drawn through ducts, then tensioned, then either
ba) only kept fixed at ends or
bb) bonded by injecting concrete or some adhesive
c) some other situation

To be able to give concrete advice, we need to know which ATENA module you are using for the modelling - ATENA Engineering 2D, Engineering 3D, or ATENA Science/GiD (or at least which of them you have and can choose)?

prestressed hollowcore

null@example.com (melted) — Thu, 02 Dec 2010 22:42:45 +0000

Hello,

I am trying to model prestressed hollow core slab . To my understanding the prestress stress distributed equally throughout the reinforcement when itâ€™s loaded for the first time.
Iâ€™m wondering how I can model the pre stress near the beginning and the end of the slab where the stress is not constant.(when it increase or decrease )

Between the concrete and reinforcement I have perfect bond .

Thanking you