13.3 Field Blast Test
443
13.3.3.2 Deflection-Time History
The deflection-time histories of each specimen are shown in Fig. 13.6, and the
maximum and residual deflections of test specimens are listed in Table 13.4, in which
the measuring data from sensors D1-D4 are denoted as D 1 -D 4 . Some displacement
sensors located at the mid-span of panels were dropped attributed to the intensive
vibrations of specimens under blast loadings, failing to obtain the maximum and/or
residual mid-span deflections. However, the residual mid-span deflections can be
measured manually after the explosions and denoted as ‘Mid-span’ in Table 13.4.
By comparisons of the deflection-time histories of present three NSC and three
UHPCC panels, it can be drawn that both the maximum and residual deflections
increase as the scaled distances of explosives decrease, indicating that the panels
suffer more severe flexural deformations when the scaled distances are reduced. It
is noted that UHPCC-2 was tested under a larger scaled distance than UHPCC-3 but
suffered a larger deflection response, the possible reason may lie in the fabrication
error of UHPCC-2 panel, e.g., the non-homogenous distribution of the fibers.
Compared with NSC specimens tested under the same scaled distances, UHPCC
panels exhibit higher blast resistance under explosions. For instance, the maximum
mid-span deflections of NSC-2 and UHPCC-1 are 43.48 mm and 27.86 mm, while
the corresponding residual deflections (average value of D 1 and D 4 ) are 15.56 mm
and 5.92 mm, respectively. The maximum and residual center deflection of UHPCC1 are 35.9% and 62.0% smaller than those of NSC-2, respectively. Also, it should be
noted that although UHPCC-2 exhibits relatively weak blast resistance among the
three UHPCC specimens, it still performs better than the control specimen NSC-3.
Furthermore, by comparisons of UHPCC specimens tested at smaller scaled distances
and NSC specimens tested at larger scaled distances, it also can be found that the
residual center deflection of UHPCC-1 and UHPCC-3 is 46.2% (5.08 mm) and 36.8%
(16.32 mm) smaller than that of NSC-1 and NSC-3, respectively. It indicates that even
subjected to more intensive blast loadings, UHPCC panels still show less damage
than NSC panels. Based on the above quantitative comparisons of the present test
data, we can draw the conclusion that UHPCC is a more outstanding concrete material
than NSC to resist the blast loadings, and the superiority of UHPCC becomes more
obvious as the scaled distance decreases.
13.3.3.3 Acceleration-Time History
For the NSC specimens, only one or two acceleration sensors were set to record
data, while all three acceleration sensors were arranged for the UHPCC specimens.
For UHPCC-3 specimen under the most intensive blast loadings among all tested
specimens attributed to the smallest scaled distance, the measuring data is not reliable since that the recorded signals far exceed the measuring range of sensors. The
experimentally recorded acceleration-time histories without filtering are shown in
Fig. 13.7, and the recording data from sensors A1-A3 are denoted as A 1 -A 3 , respectively. It indicates that the test panels oscillate violently under the explosive induced
443
13.3.3.2 Deflection-Time History
The deflection-time histories of each specimen are shown in Fig. 13.6, and the
maximum and residual deflections of test specimens are listed in Table 13.4, in which
the measuring data from sensors D1-D4 are denoted as D 1 -D 4 . Some displacement
sensors located at the mid-span of panels were dropped attributed to the intensive
vibrations of specimens under blast loadings, failing to obtain the maximum and/or
residual mid-span deflections. However, the residual mid-span deflections can be
measured manually after the explosions and denoted as ‘Mid-span’ in Table 13.4.
By comparisons of the deflection-time histories of present three NSC and three
UHPCC panels, it can be drawn that both the maximum and residual deflections
increase as the scaled distances of explosives decrease, indicating that the panels
suffer more severe flexural deformations when the scaled distances are reduced. It
is noted that UHPCC-2 was tested under a larger scaled distance than UHPCC-3 but
suffered a larger deflection response, the possible reason may lie in the fabrication
error of UHPCC-2 panel, e.g., the non-homogenous distribution of the fibers.
Compared with NSC specimens tested under the same scaled distances, UHPCC
panels exhibit higher blast resistance under explosions. For instance, the maximum
mid-span deflections of NSC-2 and UHPCC-1 are 43.48 mm and 27.86 mm, while
the corresponding residual deflections (average value of D 1 and D 4 ) are 15.56 mm
and 5.92 mm, respectively. The maximum and residual center deflection of UHPCC1 are 35.9% and 62.0% smaller than those of NSC-2, respectively. Also, it should be
noted that although UHPCC-2 exhibits relatively weak blast resistance among the
three UHPCC specimens, it still performs better than the control specimen NSC-3.
Furthermore, by comparisons of UHPCC specimens tested at smaller scaled distances
and NSC specimens tested at larger scaled distances, it also can be found that the
residual center deflection of UHPCC-1 and UHPCC-3 is 46.2% (5.08 mm) and 36.8%
(16.32 mm) smaller than that of NSC-1 and NSC-3, respectively. It indicates that even
subjected to more intensive blast loadings, UHPCC panels still show less damage
than NSC panels. Based on the above quantitative comparisons of the present test
data, we can draw the conclusion that UHPCC is a more outstanding concrete material
than NSC to resist the blast loadings, and the superiority of UHPCC becomes more
obvious as the scaled distance decreases.
13.3.3.3 Acceleration-Time History
For the NSC specimens, only one or two acceleration sensors were set to record
data, while all three acceleration sensors were arranged for the UHPCC specimens.
For UHPCC-3 specimen under the most intensive blast loadings among all tested
specimens attributed to the smallest scaled distance, the measuring data is not reliable since that the recorded signals far exceed the measuring range of sensors. The
experimentally recorded acceleration-time histories without filtering are shown in
Fig. 13.7, and the recording data from sensors A1-A3 are denoted as A 1 -A 3 , respectively. It indicates that the test panels oscillate violently under the explosive induced