HS20 & Federal max axle weight

[LearnerN]

I've been trying to determine the correct weight of wheel point loads that would be reflective of normal traffic loads. Per HS20-44, my understanding is that the max axle weight is 32,000lb. However, per the Federal Motor Carrier Safety Administration, Section 658.17(c), the max gross weight on any one axle is 20,000lb.

(1) Are HS20-44 loads ONLY for bridges? Or are they also for roads/pavement?

(2) How can this discrepancy (between HS20-44 loads and the federal max gross weight on one axle) be resolved? Should normal traffic loads be no more than 20,000lb on one axle?

Please also point me to some good resources in your responses. Thanks for your help!

 

[tumbleleaves]

HS loads are mainly for bridges, and other structural elements like traffic covers, etc. Not for pavement design.

HS20-44 loading was invented in 1944 as a good structural model for the many different models of trucks on the road in 1944.

Max single axle load is usually 20 kips, but is based on the axle spacing. For instance a dual-tandem axle (two axles spaced 4 ft are limited to about 17 kips each, unless you have another axle which is also spaced closely to the dual tandem axle.

You should really speak to someone in government that is involved with issuing the extra-legal permits. This will give you a better feel for what is actually occurring on the roads. Permits are issued for things like wide loads, as well as heavy axle weights.

Also the way a structure is analyzed is different for design and for load rating. This is commonly referred to as inventory and operating.

All these differing ways of doing things is how the design vehicle is reckoned with actual service. There is a whole specialty field out there it's called "bridge engineering".

I hate the word "notional", what is wrong with these people writing the new code? Unnecessary complexity.