chapter 3 rigid pavement - DOT On-Line Publications - Department ...

PURPOSE
This paper summarizes data concerning la:erai whee! Cis:;;j~,om azb
Tresents condusions based on that data. It aiso examines the advantages of ex:er.d?~
!or w:dened) portland cement concrete (KC) pavernent slabs in :erms of +,e!r e+c:
on stress, strain, detlection, and KC pavement deterioration.
B.ACKGROZ;‘ND
Early road widths were only 15 fi (3.6 mf, wide enough to handle +,e i.exlan&
of horse-drawn vehicles. Following the discovery of the internai combustion eng:ne
and the development of motorized vehicles, traffic steadilv increased. Tze wtd:,? or
roadways increased to 16 ft (4.9 m), and then to 18 ft (5.3 ‘m). Bv the late 1925’s.
primary paved roadways were needed and the construction of lb ti (3.0 m) lar,es :X
it [6.1 m] roadway) were standard practice. Today, conventional designs use I2 t’:
(3.7 m) lanes as standard practice.
PAST STUDIES AND COMMENTS ON THE DATA
The lateral location of traffic in the travel lane is the criteria to determine that
a 12-h (3.7 III) channeiized lane is wide enough to withstand the re+tive loads of
heavy truck traffic, and there have been several studies to determine the lateral truck
wheel distribution in the pavement lane. These studies were generally initiated for
design and safety concerns. There recently has been consideration of PCC Tavement
stresses and deflections and their connection with lateral wheel loads and shouider
encroachments. The studies’attempt to detexmine the lateral wheei distribution and
evaluate the damage done by differing transverse loads to help designers in building
an adequate pavement structure. To summarize the information on lateral whee!
distribution and the probability of pavement edge and shoulder encroachment, the
results from a number of studies on lateral wheel path trtific distribution are
highlighted in the following text
The first study on lateral wheel distribution was completed by Taragin oi the
Federal Highway Administration in 1958.“’ This data, which is sti!l used in both
current PCC and asphalt concrete (AC) pavement design, showed that the highest
frequency of travel and mean travel path distance occurred at little more than 2 !t
(0.61 m> from the right pavement edge. The findings stated that an average oi 2.3
percent of the mainline truck traffic encroached up to 12 in (305 mm) on the outside
shoulder of the test section. The findings aiso stated that about 4 percent of the
overall traffic drove cioser to the edge than 12 in (305 mm). Taragin’s study was
completed on 124 (3.7 m) pavement lanes with unpaved shoulders.
The applicability of these results for current conditions can be questioned.
There is some thought that the unpaved shoulders in the study may have been an
3.8.5