distribution of wheel loads on wood deck over steel stringer

[blueskygc]

Hi,

I'm trying to rate a simple span wood deck over steel stringer bridge. If I have 8x8 nominal decking with 2" wear on the wheel line. Would you use S/4.5 (4" thick) or S/5.25 (6" or more thick)for wheel load distribution per AASHTO table 3.23.1?

thanks,
tim

 

[bridgebuster]

I would use S/5.25 and reduce the section properties to account for the as-is condition.

 

[blueskygc]

I used S/5.25 initially, and the review engineer suggested that I should use the actual deck thickness at the wheel line to determine the distribution. Do you have any justification for using S/5.25, as S/4.5 will give me a more conservative number.

thanks...

 

[bridgebuster]

Perhaps I misread. If you have 8" original thickness and 2" inches of wear, you still have 6" and S/5.25 is OK. There's nothing wrong with being conservative. However, will being arbitrarily conservative create any unnecessary problems?

For example, will the lower rating from S/4.5 affect a certain type of vehicle that regularly uses the bridge?