Dynamic Behavior of Concrete: Experimental Aspects - Dynamic Behavior of Concrete and Seismic Engineering - page 5

reaction of the sample, arises because we need to find the optimal position of the
measuring point at the middle of the bar. On the other hand, considering the bar as
one-dimensional does not allow us to place the strain gauge too near an end. A
typical recording for a concrete sample compression test is shown in Figure 1.2.

Figure 1.2. Compression test on a concrete sample (40 mm diameter
aluminum bars): basic waves

Next, the waves have to be carried to the contacts between the sample and the
bar. Then we can calculate the stresses and displacements (by integrating the
velocities, which are directly accessible) on the corresponding faces.

The particulate velocities at the input and output faces can be written
respectively as:

ª º Vt () c

H

() t H () t

¬ ¼

e r

[1.3]

Vt () c t

H

()

s