Lightweight Concrete for High Strength - Expanded Shale & Clay

A.8.8 Deatherage, Burdette and Chew, 1989
Deatherage et al. conducted experimental testing on 20 AASHTO Type I girders with
varying strand diameters and spacings. Their conclusions were that 0.6-inch diameter strand
should be allowed and that strand spacing of 1.75 inches should be allowed for ½-inch diameter
strand. Equation A.9 was suggested for the calculation of transfer length for ½-inch, ½-inch
special and 9 / 16 -inch diameter prestressing strand. Equation A.9 was conservative and acceptable
for use on 0.6-inch strand, but further research was recommended.
l
t
=
f
si
3
d
b
( A.9)
A.8.9 Russell, 1992
Russell performed an extensive series of testing of rectangular, scale model AASHTOtype
and full-sized Texas Type C cross sections as part of a PhD Thesis under the supervision of
Dr. Ned Burns. The specimens were all prestressed with ½-inch or 0.6-inch strand spaced at 2
inches, except for three rectangular sections that were prestressed with 0.6-inch strand spaced at
2.25 inches. In many of the specimens, strands were debonded to various distances from the
girder ends. Russell concluded that larger cross sections had shorter transfer lengths, larger
strand diameters required longer transfer lengths, strand spacing greater than 2 inches for 0.6-
inch strand was not required, debonded strands had transfer lengths similar to fully bonded,
strands and confining reinforcement did not affect transfer length. Russell suggested Equation
A.10 for predicting transfer length.
where
f se =
l
t
=
effective prestressing stress after losses (psi)
f
se
2
d
b
( A.10)
A-13