AASHTO LRFD Wheel Load and Lane Load

[bthen]

Does anybody know if AASHTO requires the standard design truck wheels, spaced 6 feet apart, to be placed symmetrically within the 10 feet wide design lane load width? In other words, can the whhels be at zero feet and 4 feet from the edge of the design lane rather than 2 feet and 2 feet? Please note that I am not talking about the 12 feet Lane width, but the 10 feet Design Lane Load width.

 

[msquared48]

Having seen some truck drivers and their lateral placement in the lanes, I would be conservative in your analysis.

Mike McCann
MMC Engineering

 

[kslee1000]

The AASHTO requires the wheel loads to be placed in a manner to produce the maximum stresses in the member under consideration. I don't recall the exact distance, but it allows the wheel be placed adjacent (not on) the curb, or fixed barrier. When more than 1 truck, there is minimum distance between adjacent wheels. Anyway, there is nothing wrong to be conservative in bridge design.

 

[PEinc]

If you are supposed to be designing for AASHTO, you should get a copy of the AASHTO bridge design manual. Your questions are answered in the manual.

 

[jrw501]

Both the design lanes and the 10 ft loaded width in each lane shall be positioned to produce extreme force effects. The design truck or tandem shall be positioned transversely such that the cent of any wheel load is not closer than:

For the design of the deck overhang - 1 ft from the face of curb or railing and

For the design of all other components - 2 ft from the edge of the design lane

From 3.6.1.3.1

 

[crossframe]

Within the 10' design lane, the wheels can be placed anywhere, so the closest you can get two adjacent wheels is 4' apart (one wheel from each design lane). In a line-girder analysis for an interior girder, this will usually produce the controlling live load effects.