Historical PCI multipliers

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Historical PCI multipliers

Hello,

How does PGSuper accommodate use of the historical PCI multipliers? This method uses different multipliers for the deflection due to component weight (1.85) at erection and the deflection due to prestress (1.80) at erection. PGSuper deflection multipliers inputs do not distinguish between the two and simply provides an "Erection Camber" input. Thanks,

-Conner

Pickings
You are correct. PGSuper's

You are correct. PGSuper's multiplier value at erection is a single value applied to both dead load and prestress deflection, so you cannot precisely apply the PCI multiplier method. However, the difference between 1.80 and 1.85 is about 2.75%. Which is small considering:

Referring to the excellent article presenting the original development of the method at https://www.pci.org/PCI_Docs/Design_Resources/Guides_and_manuals/referen... , I would consider that the author goes out of his way to present the inherent inaccuracies of the method and camber prediction in general. My favorite quote is: "It is even of questionable value to program these equations for a computer, except as an exercise in computer programming". Pretty strong words, but I understand that we must provide something.

That said, a likely good approximation would be to use a value of 1.82 in PGSuper for erection camber since prestressing deflection is typically larger than the girder dead load deflection. This should get you well within 2% of the "correct" value. Sorry for the bad news, but codifying the PCI multipliers was not a requirement in the development of PGSuper's camber multiplier feature.

Best regards,

Richard Pickings, P.E.
BridgeSight Inc.

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