Bridge Rating

[a7x1984]

The state I work in is performing a comprehensive structures load rating. The Policy and Procedure Manual outlines the basic guidelines for how they want things to be done. They specifically are mandating that LFR to be performed on all bridges that were designed with either LFD or WSD. Only bridges designed with LRFD will be rated with LRFR. I have been told the reason is conservatism.

I don't buy it, as it is not always clear which way the ratings will swing due to a change in the rating methodology. I have a feeling it is all about what they have been comfortable with. Can anybody suggest some rationale that would defend their actions?

Thanks!

In Russia building design you!

 

[Ron]

Why would you not consider rating based on actual loading and measured response. Much more accurate than analytical guesswork.

 

[a7x1984]

They sort of are. They have amassed a collection of the most typical legal and permit trucks, varying from dump trucks to AT cranes (design trucks included as well). I was not involved with that part, but I think that the Office of Structures collaborated with Hauling Permits to get some of this semi-empirical data.

The purpose of the rating procedure is to rate all of these 'typical' trucks AND to simultaneously provide an analysis model for every bridge so the soon-to-come super load "automated" system can analyze all of the various permit trucks in a jiffy.

In Russia building design you!