11.2 Explosion Test on UHPCC-FST Column
373
gradients as well as the preparation procedure can be referred from our previous
work (Ren et al. 2018a). The wet density, average quasi-static compressive strength,
elastic modulus and Poisson’s ratio of UHPCC are 2480 kg/m
3 , 141.5 MPa, 43.8 GPa
and 0.23, respectively.
11.2.2 Test Setup
Considering that the relative low axial compressive ratio (ratio of the axial force of
column to the product of the cross-section area of column and cylinder compressive
strength of core concrete) of the bridge columns, as well as the boundary constraints
have negligible effect on the local deformations of the specimens subjected to the
close-range explosions, in the present blast test, the UHPCC-FST columns were
placed horizontally and the axial force is not considered. Two steel components were
designed to support the column specimen away from the ground with a clear distance
of 100 mm, as shown in Fig. 11.3a. The diagram and photograph of the experimental
setup are shown in Fig. 11.3b and c, respectively. Four column specimens denoted
as C-1–C-4 have a clear span of 1900 mm between the two steel supports. TNT
explosive with the charge weight from 3 to 10 kg were placed in the mid-span and
100 mm above the top surface of the specimen. The cylindrical TNT explosive was
used in the blast test because it is a standard high explosive deemed chemically safe
and easy to cast, and it was initiated from the top by using the electric detonator. The
experimental details for each specimen are given in Table 11.2.
11.2.3 Test Results and Analyses
The four specimens after close-range explosion are presented in Fig. 11.4. Generally,
the four specimens are not heavily destroyed and the integrity of which are kept, i.e.,
the outer steel tubes were not cracked and the section of columns were not breached.
Column C-4 suffers more severe damage than the other three columns due to smaller
scaled standoff distance of explosive. Thus, the UHPCC-FST column can maintain
the majority of its axial bearing capacity and exhibit the excellent blast resistance
against the close-range explosions. It is observed that a local elliptical crater was
formed beneath the explosive, as shown in Fig. 11.5, the dimensions and depth of the
crater are denoted as D x , D y and D p , respectively. By comparing the blast induced
crater dimensions with the blast test data on normal CFST columns in Li et al.
(2018), the superiority of UHPCC-FST column against the near field explosion is also
validated qualitatively. It should be pointed out that, for the near range explosions,
the pressure transducer and the displacement sensor could be easily damaged by the
detonation wave and fire ball during the blast, thus only the residual deformations
373
gradients as well as the preparation procedure can be referred from our previous
work (Ren et al. 2018a). The wet density, average quasi-static compressive strength,
elastic modulus and Poisson’s ratio of UHPCC are 2480 kg/m
3 , 141.5 MPa, 43.8 GPa
and 0.23, respectively.
11.2.2 Test Setup
Considering that the relative low axial compressive ratio (ratio of the axial force of
column to the product of the cross-section area of column and cylinder compressive
strength of core concrete) of the bridge columns, as well as the boundary constraints
have negligible effect on the local deformations of the specimens subjected to the
close-range explosions, in the present blast test, the UHPCC-FST columns were
placed horizontally and the axial force is not considered. Two steel components were
designed to support the column specimen away from the ground with a clear distance
of 100 mm, as shown in Fig. 11.3a. The diagram and photograph of the experimental
setup are shown in Fig. 11.3b and c, respectively. Four column specimens denoted
as C-1–C-4 have a clear span of 1900 mm between the two steel supports. TNT
explosive with the charge weight from 3 to 10 kg were placed in the mid-span and
100 mm above the top surface of the specimen. The cylindrical TNT explosive was
used in the blast test because it is a standard high explosive deemed chemically safe
and easy to cast, and it was initiated from the top by using the electric detonator. The
experimental details for each specimen are given in Table 11.2.
11.2.3 Test Results and Analyses
The four specimens after close-range explosion are presented in Fig. 11.4. Generally,
the four specimens are not heavily destroyed and the integrity of which are kept, i.e.,
the outer steel tubes were not cracked and the section of columns were not breached.
Column C-4 suffers more severe damage than the other three columns due to smaller
scaled standoff distance of explosive. Thus, the UHPCC-FST column can maintain
the majority of its axial bearing capacity and exhibit the excellent blast resistance
against the close-range explosions. It is observed that a local elliptical crater was
formed beneath the explosive, as shown in Fig. 11.5, the dimensions and depth of the
crater are denoted as D x , D y and D p , respectively. By comparing the blast induced
crater dimensions with the blast test data on normal CFST columns in Li et al.
(2018), the superiority of UHPCC-FST column against the near field explosion is also
validated qualitatively. It should be pointed out that, for the near range explosions,
the pressure transducer and the displacement sensor could be easily damaged by the
detonation wave and fire ball during the blast, thus only the residual deformations