why is AASHTO ESAL 18-kips? 32 kips is maximum axle load for HS20-44?

[delagina]

I have a situation where I need to design a reinforced slab where HS20-44 loading will pass thru.
I will be designing it using 16kip (32kps/2) point loads on wheel location of slab.
is this ok?

how did aashto come up with 18-kip ESAL?

 

[cvg]

see chapter 2

https://www.utexas.edu/research/ctr/pdf_reports/0_1713_1.pdf

 

[mike20793]

I'd use the axle loads and calculate the live load distribution for the entire axle, similar to a slab bridge design.