13.2 Review of the Existing Work
435
verified by comparisons with the test reported by Kuznetsov et al. (2006). CONWEP
(Hyde 1993) is an implementation of the empirical blast models of Kingery and
Bulmash (Kingery and Bulmash, 1984; TM5-855-1 1986), which was originally
incorporated into in DYNA by Randers-Pehrson and Bannister (Randers-Pehrson
and Bannister 1997). In LS-DYNA (LSTC, 2007), CONWEP method is adopted
to predict the blast induced overpressure through the keywords *Load_Blast or
*Load_Blast_Enhanced. Foglar et al. (2017) numerically clarified the contribution
of basalt mesh incorporated into UHPC panel under explosions, in which the uncoupled *Load_Blast_Enhanced function and Continuous Surface Cap model (Schwer
and Murray 1994) were employed to model blast loadings and UHPC, respectively.
Li et al. (2015a) conducted the numerical simulations of reinforced UHPC panels
under free field air explosions, in which the blast loading was predicted by using
the built-in *Load_Blast function, and the Elastic-Plastic Hydrodynamics model
(Hallquist, 2006) without considering the strain rate effect of UHPC was validated.
The *Load_Blast/*Load_Blast_Enhanced function and K&C model were employed
by Mao et al. (2014, 2015) and Lin (2018) to reproduce the free air blast test on
plain and reinforced UHPC panels, respectively. The strain rate effects of UHPC in
tension and compression were incorporated, and the parameters controlling the softening behavior of UHPC was calibrated to fit a pre-designed stress-strain relationship
(Mao et al. 2014, 2015) and the experimental uniaxial stress-strain relationships (Lin
2018), respectively. It was proved that K&C model can well describe the dynamic
behavior of UHPC under blast loadings after careful calibrations of its constitutive
model parameters.
13.3 Field Blast Test
13.3.1 Specimen
A total of six test specimens are fabricated in the current test, including three reinforced NSC panels and three reinforced UHPCC panels, which are referred as NSC
panels and UHPCC panels hereinafter, respectively. The geometrical dimensions
and the reinforcement of test panels are schematically shown in Fig. 13.1, in which
two layers of 10 mm diameter mesh reinforcements with 100 mm spacing in major
bending plane and 200 mm spacing in the minor bending plane were placed, and
the yield strength of rebars is 480 MPa. UHPCC panels are prefabricated by mixing
the Chinese standard Graded 52.5 P.II type Portland cement, silica fume, ultra-fine
mineral admixture which consists of fly ash and ultra-fine slag, the natural river sand
with a maximal diameter of 2.5 mm, polycarboxylic type high-range-water-reducer
(HRWR) and 2% (volume fraction) straight brass-coated steel fiber. The mixture
proportions are shown in Table 13.1. Based on Chinese standard (GB/T 50081-2002
2003), the compressive strength and splitting tensile strength of NSC specimens are
30.4 MPa and 3.36 MPa, respectively. Correspondingly, the compressive strength
435
verified by comparisons with the test reported by Kuznetsov et al. (2006). CONWEP
(Hyde 1993) is an implementation of the empirical blast models of Kingery and
Bulmash (Kingery and Bulmash, 1984; TM5-855-1 1986), which was originally
incorporated into in DYNA by Randers-Pehrson and Bannister (Randers-Pehrson
and Bannister 1997). In LS-DYNA (LSTC, 2007), CONWEP method is adopted
to predict the blast induced overpressure through the keywords *Load_Blast or
*Load_Blast_Enhanced. Foglar et al. (2017) numerically clarified the contribution
of basalt mesh incorporated into UHPC panel under explosions, in which the uncoupled *Load_Blast_Enhanced function and Continuous Surface Cap model (Schwer
and Murray 1994) were employed to model blast loadings and UHPC, respectively.
Li et al. (2015a) conducted the numerical simulations of reinforced UHPC panels
under free field air explosions, in which the blast loading was predicted by using
the built-in *Load_Blast function, and the Elastic-Plastic Hydrodynamics model
(Hallquist, 2006) without considering the strain rate effect of UHPC was validated.
The *Load_Blast/*Load_Blast_Enhanced function and K&C model were employed
by Mao et al. (2014, 2015) and Lin (2018) to reproduce the free air blast test on
plain and reinforced UHPC panels, respectively. The strain rate effects of UHPC in
tension and compression were incorporated, and the parameters controlling the softening behavior of UHPC was calibrated to fit a pre-designed stress-strain relationship
(Mao et al. 2014, 2015) and the experimental uniaxial stress-strain relationships (Lin
2018), respectively. It was proved that K&C model can well describe the dynamic
behavior of UHPC under blast loadings after careful calibrations of its constitutive
model parameters.
13.3 Field Blast Test
13.3.1 Specimen
A total of six test specimens are fabricated in the current test, including three reinforced NSC panels and three reinforced UHPCC panels, which are referred as NSC
panels and UHPCC panels hereinafter, respectively. The geometrical dimensions
and the reinforcement of test panels are schematically shown in Fig. 13.1, in which
two layers of 10 mm diameter mesh reinforcements with 100 mm spacing in major
bending plane and 200 mm spacing in the minor bending plane were placed, and
the yield strength of rebars is 480 MPa. UHPCC panels are prefabricated by mixing
the Chinese standard Graded 52.5 P.II type Portland cement, silica fume, ultra-fine
mineral admixture which consists of fly ash and ultra-fine slag, the natural river sand
with a maximal diameter of 2.5 mm, polycarboxylic type high-range-water-reducer
(HRWR) and 2% (volume fraction) straight brass-coated steel fiber. The mixture
proportions are shown in Table 13.1. Based on Chinese standard (GB/T 50081-2002
2003), the compressive strength and splitting tensile strength of NSC specimens are
30.4 MPa and 3.36 MPa, respectively. Correspondingly, the compressive strength