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# RE: BRIDGE DESIGN: Questions re Live Load Distribution Factors inAASHTO-LRFD

• To: "'seaoc(--nospam--at)seaoc.org'" <seaoc(--nospam--at)seaoc.org>
• Subject: RE: BRIDGE DESIGN: Questions re Live Load Distribution Factors inAASHTO-LRFD
• From: Bill Polhemus <polhemus(--nospam--at)insync.net>
• Date: Mon, 15 Jun 1998 11:24:27 -0500

```-----Original Message-----
From:	Powers, Tony [SMTP:tpowers(--nospam--at)hdrinc.com]
Sent:	Wednesday, June 10, 1998 7:53 PM

Variable Spacing:	A good approximation of moments and shears for
non-parallel girders can be achieved by varying the distribution factors
along the length of the girder.

[Bill Polhemus]

This will be pretty difficult, though, since we're using a P.C. program to design the prestressed girders.  I suppose we could enter a distribution factor of 1.0 in the program, obtain the moments/shears, and then use a spreadsheet to multiply by the varying distribution factors at discrete points.

But this would significantly add to the complexity of what is normally a simple procedure.

Curvature:	Moments and shears in girders of curved bridges vary
significantly (higher on the outside girders), lower on the inside girders,
and near the average at the center.  The only way that I am aware to
approximate the affects of curvature is the "V-load" method.

[Bill Polhemus]

V-Load is great for steel.  However, we're doin' concrete for most of these bridges (and using the Standard Specification [i.e. ASD] for the trapezoidal steel box girder bridges).