# Re: Balanced Moment vs PT Moment

• To: <seaint(--nospam--at)seaint.org>
• Subject: Re: Balanced Moment vs PT Moment
• From: Gil Brock <gil(--nospam--at)raptsoftware.com>
• Date: Wed, 01 Jun 2005 09:59:53 +1000
Will,

Forget about the word "balanced". It is the PT moment. It does not matter what the shape of the tendon profile is, the PT moment at any point along the member is the prestress force multiplied by the tendon eccentricity at that point.

If you have an in-determinant member, there will be secondary prestress moments induced by restraints to the bending induced by the basic PT moment which add to the basic PT moment to give the total prestress moment.

At 06:37 AM 1/06/2005, you wrote:
Is the "balanced moment" always equal to the moment from the post tensioning?

In other words, if I have beam with a straight tendon at a constant eccentricity of 6" and a force of 150 kips, the moment from the post tensioning is a constant 75 ft*kips. Would it be correct to also call this the "balanced moment"?  Even though this is not a parabolic profile?

Or, if the same beam has a parabolic tendon profile, but the tendon is eccentrically placed at each end. Would the balanced moment at the beam midspan be the sum of the (eccentric end moment + the moment from the drape), or would it be just the moment from the drape?

I am not sure what the definition of "balanced moment" is supposed to be for beams with tendons that are eccentrically placed at the ends.

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Regards  Gil Brock
Prestressed Concrete Design Consultants Pty. Ltd. (ABN 84 003 163 586)
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