From: Jim Kestner <jkestner(--nospam--at)somervilleinc.com>
Date: Mon, 17 Apr 2000 11:29:42 -0500
Westergaard produced a number of useful graphs for determining moments
produced by concentrated loads for the Bureau of Public Roads in the
30's. Included is positive moments in both directions for simple and
fixed spans as well as overlapping effects for multiple loads and
negative moments produced by a concentrated load near an interior
Spangler produced a study that gave a methodology for determining the
effective width for shear.
I believe the information in AASHTO is based on Westergaard's work. I
find that these original works are extremely useful (and easy to apply)
for the engineer who designs buildings, since they are not in terms of H
and HS loadings and contact areas.
I recommend that you obtain copies from your local library.
The articles are as follows:
Computation of Stresses in Bridge Slabs Due to Wheel Loads by H. M.
Westergaard, March 1930, Vol. 11, No. 1, Public Roads
The Distribution of Shearing Stresses in Concrete Floor Slabs Under
Concentrated Loads by M. G. Spangler, April 22, 1936, Bulletin 126, Iowa
Engineering Experiment Station
Jim Kestner, P.E.
Green Bay, Wi.