HS25 Impact Loading 1

[msquared48]

Question on the required 22.5 Kip (for moment) point load for HS25...

Does impact loading have to be added to this per AASHTO? I don't have a current copy and can find no reference to this. If so, I would expect 30%.

Designing steel grate for a vault lid and it comes into play here.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[bridgebuster]

yes, it's applied to the uniform and the concentrated load. Don't have an AASHTO in front of me but I can look for the citation next week.

 

[msquared48]

Thanks BB. If you could post that reference early next week, I would really appreciate it.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[bridgebuster]

no problem Mike

 

[bridgebuster]

AASHTO Standard Specs (17th & final ed.) Section 3.8.1 states that impact will be applied to the highway loading. The highway loading is defined in 3.7.6, which is the truck or equivalent lane load.

 

[bpstruct]

Are you sure you can use the standard specs on this project? I think fhwa requires use of lrfd provisions of AASHTO if there is any federal funding involved...could be wrong though, and it may not apply to this type of work anyway. The lrfd provisions for impact have increased to 33%, but it is applied only to the truck load. Live load provisions have changed too. The point loads were removed and you now apply both the truck load and the lane load concurrently.

 

[bridgebuster]

HS25 implies Standard Specs, whereas LRFD would be HL-93.

 

[msquared48]

Thanks again BB. If I could give you a second star, I would.

It's one of those situations where the supplier says that he has done it this way for years with no problems, if you know what I mean. The documented references will help immensely.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[bridgebuster]

Thanks for star Mike. I know what you mean. I had a similar experience some years ago dealing with a staircase designer/manufacturer.