AASHTO Load Group History

[crossframe]

Does anyone know where I can find information, history and commentary about the AASHTO Load Groups? Specifically, I'm looking for background, rationale, and individual loads and situations each load group was intended to model.

 

[bridgebuster]

The earliest AASHTO actually, it's AASHO) I could find in the office is the 1953 edition. The load combinations are the same as the current Standard Specs with the excecption of LFD, which didn't exist at the time.

Many of the provisions from the original AASHO were adopted from the railroad codes and they remained ever since.

 

[crossframe]

We don't have any early AASHO manuals here. I guess we're doomed to repeat the past.

We have some recent additions to our office, and this came up as a "Why do you use the Load Group IX Gamma, Beta, Allowable Overstress factors for the Construction Load case?" question. We agreed that it would be beneficial if we could locate some sort of documentation or commentary of the rationale behind the load cases.

 

[SoeSoe]

"Structures shall be proportioned for the following loads and forces:
a) Dead Load.
b) Live load.
c) Impact or dynamic effect of the live load.
d) Lateral forces.
e) Other forces, when they exist as follows: Longitudinal force, centrifugal force, and thermal forces.

Members shall be proportioned for the combination of loads and forces producing the maximum total stress, except as otherwise provided herein. Upon the stress sheets a diagram of the assumed live loads ahll be shown and the stresses due to the various loads shall be shown separately."

The H10 is a steam roller. It was discovered that the bridges must be able to carry the loads of the equipment that builds the roads. Before this a uniform load was used and most bridges were built by surveyors and railroad men.

Why are so many engineers that aren't?