DC Loads from PGSuper to XBRate

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DC Loads from PGSuper to XBRate

I have a 3 span prestressed concrete bridge with 5 girder lines. The bridge has no skew. The end abutments are expansion piers, while intermediate abutments are integral after deck is cast. I'm load rating the girders and intermediate crossbeams.

I'm trying to verify the DC reactions exported from PGSuper into XBRate, but my hand calcs don't agree with the numbers shown in XBRate. As an example, I look at the reaction from girder line B at Pier 2. The attached image shows 'Loading Details' from Girder B Span 1 and 2 on the right half of screen and 'Loading Details' for Pier 2 on the left half of screen. I've verified the Girder B uniform loads listed for Girder, Sidewalk, Traffic Barrier, Main Slab, and Haunch are being calculated correctly (no DC user loads are applied); the sum of these unit loads is 2.781 kip/ft (referred to as w below). Note that in the PGSuper 'Connections' tab, I've ignored the weight of diaphragms, as XBRate appears to account for these under 'Cross Beam Dead Load'.
Girder B in Span 1 is 107.208'; Girder B in Span 2 is 102.417' - so the average span length is 104.813' (referred to as L below).

The reaction from girder line B at Pier 2 should be given by 1.14 x w x L (see AISC Steel Construction Manual Table 3-23, Case 42). This equates to 332.29 kips. However, XBRate is showing a reaction of 58.05 kips.

Another point of confusion - when I change the pier from 'integral after deck is cast' to 'integral before deck is cast' the reaction shown in XBRate jumps from 58.05 kips to 217.62 kips. The loads under 'Lower Cross Beam' in XBRate remain the same for both cases. It seems to me that the reaction the crossbeam sees should be the same for both of these cases.

Am I overlooking something? PGSuper model and Loading reports attached.


Rick Brice
DC Loads from PGSuper to XBRate

As you have pointed out, the DC pier reactions from PGSuper are not properly applied into XBRate. We will get this fixed ASAP and hopefully publish an update next week.

As a work around, you can export your pier model from PGSuper to XBRate and analyze it independently from the bridge model. You can correct the DC loads in the XBRate model.

Be careful not to use the 1.14wL for the dead load reactions from the simple span elements. This is the dead load reaction for a continuous beam. The girder, diaphragms, and deck dead load are simple span elements. The barriers and live loads are applied to the continuous span. Additionally, your load rating setting in PGSuper is to use the governing of simple span and continuous span reactions (Envelope mode) for pier reactions.

Rick - Thanks for checking on

Rick - Thanks for checking on this. We'll use the work around you've suggested until you have a chance to update the software.


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