Alternative Support Systems for Cantilever - National Transportation ...

accurate strength prediction when the average 28-day compressive strength of the concrete
cylinders was obtained.
By using Equation 3-7, the torsional breakout strength for the assembly was determined to
be 249 kip-ft for the torsion test apparatus. Similarly, by using Equation 3-10, the torsional side-
face blowout strength for the assembly was determined to be 390 kip-ft. See Figure 4-1 for the
expected breakout configuration of the torsional test assembly. The expected torsional breakout
and side-face blowout strengths of the torsional and flexural test assembly were calculated
similarly using Equations 3-7 and 3-10. The expected torsional breakout strength of the torsion
and flexure test assembly was 348 kip-ft while the expected torsional side-face blowout strength
of the second test assembly was 523 kip-ft.
By using Equations 3-13 and 3-14, the flexural breakout and side-face blowout strengths
could be determined. Equation 3-13 determined a flexural breakout strength of 218 kip-ft.
Equation 3-14 determined a flexural side-face blowout strength of 337 kip-ft. Of concern in the
combined torsion and flexure test was the potential interaction between torsional and flexural
breakout due to overlap in the breakout surfaces (Figure 4-9). A linear interaction diagram
between torsion and flexural strengths was produced to predict a testing failure load (See Figure
4-10). Because of the test arrangement, a 1 kip applied load would produce 9 kip-ft of torsional
moment and 8 kip-ft of flexural moment. Therefore if a completely linear interaction occurred
then the maximum flexural moment would be 128 kip-ft and the maximum torsional moment
would be 144 kip-ft.
4.2.2 Welded Stiffener Plates Design
The starting point for the design of the welded stiffener plates was to determine their width
and thickness. It was determined that a 1”x1” plate would be approximately equivalent to an
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