Free-Vibration Tests on Slender Cylinders

The objective of these tests was to estimate the modulus of elasticity of slender plain-concrete cylinders from free-vibration tests.

Four plain-concrete cylinders of nominal length 80 in and 40 in were cast. The cross section shape was circular with a diameter of 2 in. The aspect ratios (L/r) of the cylinders were 80 and 40. The mix proportions and materials used for the cylinders were the same of the flat-plate test structure. The as-built lengths of the 2-in diameter specimens were 77-3/4 in, and 38-1/4 in. The specimens were not cured.

The slender cylinders were supported on two roller supports. The distance from the edge of the cylinders to the centerline of the supports (overhang) was varied. The specimens were tapped using a small steel hammer with a mass of 1 lb. An accelerometer was installed at near the tip for the tests with overhangs and at midspan when the overhang length was zero. The tests were done 28 days after casting.

Sixty-four 6x12 cylinders were cast with the slender cylinders to measure the compressive strength and modulus of elasticity at different days after casting (3, 7, 14, and 28). The 6x12 cylinders were separated in two groups. The cylinders of the first group were not cured and in the second the cylinders were cured using wet burlap for 10 days.