Post Tension Newbie 3

[bevo98]

Hi folks,

I'm doing some post tension design for the first time and I have a question about something that a coworker mentioned to me. According to our notes and specs, we basically provide the effective tensile load required for the beam to operate. Losses, anchorages and other items are for the manufacturer to check and design. In addition to the PT design, I have been instructed to design the beam to include enough mild steel (bonded) for a special condition which includes the dead load and 25% of the live load. This will allow the beam to act like a regular (non-PT) beam and support itself if something should happen to the cables. I have searched through the codes, but have not yet found a reference to this requirement. Could someone please let me know if you are familiar with this stipulation? I am having to add a lot of mild steel and I believe I will need to do some additional calcs to make sure the beam is still acceptable. Thanks in advance for any help or advice you can offer.

 

[VoyageofDiscovery]

Hi bevo98,

I have not heard of such a method when designing post-tensioned. Post-tensioning, prestresses a beam and no amount of mild reinforcing for a given depth of beam can measure up to such a post-tensioned capacity.

I don't know what industry you are in, but from my experience I have had to design all my prestressed or cast-in-place post-tensioned members.

Regards

VOD

 

[Taro]

The 100% dead + 25% live requirement was a modification to ACI-318 by the Uniform Building Code. See 1997 UBC Section 1918.9.2.2. It is not required by the International Building Code.

 

[bevo98]

BAM!!!

Now that's some good information.

Thanks Taro

 

[VoyageofDiscovery]

My p-t background is in bridges, my apologies for not being helpful.

Regards

VOD

 

[JAE]

VOD - nothing to apologize about - Eng-Tips runs on enthusiasm and participation. Appreciate all your posts.

 

[VoyageofDiscovery]

Thanks.

VOD