Load Rating Distribution Factor and Methodology

[boz9999]

Everyone,

I need help with a load rating.

Please see the attached picture for the girder configuration. Essentially its two bridges, with the right bridge constructed in 1993 with 9 pre stressed unit (PSU, precast solid) girders and the left side was constructed in 2005 with 11 girders. Each side is post tensioned independently so that all units act as one with no median.

I am modeling this with AASHTOWare.

My questions are as follows:

1) If the exterior beam has a different width then the interior and both are less than 60"

and

2) If the exterior width is less than 60" but the interior width is greater than 60":

Which Distribution Factor method should be used,

The Lever Rule or the AASHTO Approximate Method 4.4.2

Any help would be greatly appreciated. ANYTHING!!

Thanks in advance.

 

[mike20793]

I think it's the Lever Rule Method, but I would try both and see which causes the larger load on the girder of interest. Are you load rating for a permit vehicle or just the typical HL-93 loads? If it's a permit vehicle, can you require that they stay within the interior lanes as to not affect the most vulnerable part of the bridge? What methodology was used to design the bridge, LFD or LRFD?