TM 5-809-1/AFM 88-3, Chap. 15
e. Allowable deflection for JFC pavement. The
allowable deflections determined from figure 5-18.
elastic deflection that JFC floor slabs experience
Deflections need not be checked for axle loads less
must be limited to prevent overstressing of the foun-
than 25 kips. If the computed deflection is less than
dation material and thus premature failure of the
the allowable deflection, the thickness meets allow-
pavement. Curves are provided (fig 5-17) for the
able deflection criteria and is acceptable. If the
computation of the vertical elastic deflection that a
computed deflection is larger than the allowable de-
slab will experience when loaded. Use of the curves
flection, the thickness must be increased or a new
requires three different inputs: slab thickness, sub-
design initiated with a different value for either R or
grade modulus, and gross weight of the design ve-
k . The process must be repeated until a thickness
hicle. The slab thickness is that which is determined
based upon the limiting stress criterion will also
from paragraph 5-9d above. The computed vertical
have a computed deflection equal to or less than the
elastic deflection is then compared with appropriate
allowable value.
5-29
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