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• To: seaint(--nospam--at)seaint.org
• From: Roger Turk <73527.1356(--nospam--at)compuserve.com>
• Date: Sun, 1 Aug 1999 00:23:17 -0400

```Ed,

The figures that I am referring to are in the 15th Edition of the AASHTO
Bridge Specs but should be the same or close to the 16th edition --- I don't

The lane load (Figure 3.7.6B) represents a train, or line, of trucks in a
lane, which consists of the "standard truck" (HS20-44, HS15-44, H20-44, or
H15-44 as shown in Figures 3.7.6A and 3.7.7A) preceded and followed by trucks
75 percent of the weight of the "standard truck."  See Appendix B.  (It used
to be that you had to consider the concentrated loads of each truck in the
simpler.)

Section 3.11.4.2 should be read as:

"For continuous spans:

or discontinuous so as to produce the maximum effect (shear, moment,
deflection, etc.).

b.  When the standard truck loading (Figure 3.7.6A or 3.7.7A) is used (an H
or HS truck) only one standard truck shall be placed on the structure so as
to produce the maximum effect (shear, moment, deflection, etc.)"

one or more lanes that represent the axle loads on one "standard truck" in

be continuous or discontinuous, plus one or two concentrated loads in each
loaded lane, and represents the effect of a line of trucks traveling in those
lanes.

For a simple span, the standard truck loading generally controls for spans
less than approx. 140 ft. (See Appendix A) and the variable spacing, V for HS
trucks, is kept at the minimum distance, 14 ft.  For continuous spans when
primarily for determining negative moments, so that one heavily loaded axle
is on one side of the support and the other heavily loaded axle is on the
other side.

Hope this helps.

A. Roger Turk, P.E.(Structural)
Tucson, Arizona

Ed Fasula wrote:

>>I just got the 16th Ed. AASHTO spec and I'm not clear what a lane load is
exactly.  3.7.1.1 states, "lane loads ... are equivalent to truck trains."