AASHTO Wind

[carls88]

I'm a little confused by the last paragraph of AASHTO 3.8.1.2.1, which states "The total wind loading shall not be taken less than .... 0.30 klf on beam or girder spans".

Does this correspond to the base pressure (V=100mph) and should it be adjusted for higher wind velocities? Would this govern for a bridge with a 5'-0" tributary girder/barrier height (W=0.050ksf x 5ft = 0.25klf < 0.30klf)?

I'm particularly curious how this applies to PPI Practice Exam Question #16.

Good luck to everyone taking the exam this month. Less than three weeks to go ....

 

[Moose70]

0.30 klf is set as the minimum superstructure wind loading for beam/girder bridges and does not need to be adjusted for different base pressures. After computing your wind loading, you would check it against this minimum (i.e. in your example 0.30 klf would govern).

PPI Question #16 has a superstructure wind design pressure of 0.072 ksf and a 5' depth = 0.36 klf > 0.30 klf, so you would use 0.36 klf as your superstructure wind loading.

 

[carls88]

Moose - thanks for the quick and clear response.