320
10 Residual Axial Capacity of UHPCC-FST Column Under …
Nassirnia et al. 2016), can confine the core concrete and prevent the spalling damage
of concrete under blast loading. Ultra-high performance cementitious composite
(UHPCC) is a relatively new cement-based composite with prominent mechanical
properties (both static and dynamic), low shrinkage and excellent durability. It is
a promising construction material for protective structures (e.g., military fortifications, civil defense shelters, nuclear containments) to resist intensive impact and
blast loadings. A CFST column infilled with UHPCC can take advantage of the high
compressive strength and ductility of the core concrete which can delay or prevent
the buckling of the steel tubes under close-in range and even contact detonations.
Ultra-high performance cementitious composite filled steel tube (UHPCC-FST) has
been widely applied as the load bearing members for long-span bridges, which are
the potential bomb explosion attack targets in terrorism activities.
This chapter aims to perform the experimental and numerical studies on the
residual axial capacity of UHPCC-FST columns under contact explosion (Wang
et al. 2020a, b). Firstly, five UHPCC-FST cylinder columns are fabricated with
the column height, outer diameter and core concrete compressive strength being
2000 mm, 203 mm and 131.5 MPa, respectively. Secondly, three of which are tested
under contact explosion with the TNT charge weights of 1, 2 and 3 kg, in which the
impact craters are formed and the integrity of the columns is maintained under 1 kg
and 2 kg TNT explosions, while the outer steel tube is seriously ruptured and the core
UHPCC is fully crushed for 3 kg TNT explosion. Then, the original axial capacity of
intact columns and the residual axial capacity of blast-damaged columns are evaluated though the axial compression tests, and the relationships between the axial load
and axial/lateral displacement are derived. It indicates that, (i) both the intact and
blast-damaged columns under axial compression show diagonal shear failure, and
the local bulging of steel tube is induced due to the low confinement of steel tube and
high compressive strength of UHPCC; (ii) the quantitative dependence of column
damage index on the charge weight is determined.
Furthermore, by utilizing the multi-material Arbitrary Lagrange-Euler (ALE)
algorithm, Fluid–Structure Interaction (FSI) method, the restart input data method
and element erosion algorithm implemented in the finite element (FE) code LSDYNA, the numerical simulations corresponding to the above contact charge explosion and the following axial compression tests are carried out. The damage and
failure modes of UHPCC-FST columns are reproduced and validated by comparing
with the experimental data. Finally, the related parametric influences, e.g., thickness
and strength of steel tube, compressive strength of core concrete and column diameter, on the local blast formed crater depth, the post-blast residual axial load bearing
capacity, as well as the corresponding damage index of UHPCC-FST column under
contact detonation are discussed. The influential degree of above parameters on the
residual axial capacity of UHPCC-FST columns under contact explosion is clarified. The present work can provide helpful references for evaluating the post-blast
performance as well as the design of UHPCC-FST column under contact explosion.
10 Residual Axial Capacity of UHPCC-FST Column Under …
Nassirnia et al. 2016), can confine the core concrete and prevent the spalling damage
of concrete under blast loading. Ultra-high performance cementitious composite
(UHPCC) is a relatively new cement-based composite with prominent mechanical
properties (both static and dynamic), low shrinkage and excellent durability. It is
a promising construction material for protective structures (e.g., military fortifications, civil defense shelters, nuclear containments) to resist intensive impact and
blast loadings. A CFST column infilled with UHPCC can take advantage of the high
compressive strength and ductility of the core concrete which can delay or prevent
the buckling of the steel tubes under close-in range and even contact detonations.
Ultra-high performance cementitious composite filled steel tube (UHPCC-FST) has
been widely applied as the load bearing members for long-span bridges, which are
the potential bomb explosion attack targets in terrorism activities.
This chapter aims to perform the experimental and numerical studies on the
residual axial capacity of UHPCC-FST columns under contact explosion (Wang
et al. 2020a, b). Firstly, five UHPCC-FST cylinder columns are fabricated with
the column height, outer diameter and core concrete compressive strength being
2000 mm, 203 mm and 131.5 MPa, respectively. Secondly, three of which are tested
under contact explosion with the TNT charge weights of 1, 2 and 3 kg, in which the
impact craters are formed and the integrity of the columns is maintained under 1 kg
and 2 kg TNT explosions, while the outer steel tube is seriously ruptured and the core
UHPCC is fully crushed for 3 kg TNT explosion. Then, the original axial capacity of
intact columns and the residual axial capacity of blast-damaged columns are evaluated though the axial compression tests, and the relationships between the axial load
and axial/lateral displacement are derived. It indicates that, (i) both the intact and
blast-damaged columns under axial compression show diagonal shear failure, and
the local bulging of steel tube is induced due to the low confinement of steel tube and
high compressive strength of UHPCC; (ii) the quantitative dependence of column
damage index on the charge weight is determined.
Furthermore, by utilizing the multi-material Arbitrary Lagrange-Euler (ALE)
algorithm, Fluid–Structure Interaction (FSI) method, the restart input data method
and element erosion algorithm implemented in the finite element (FE) code LSDYNA, the numerical simulations corresponding to the above contact charge explosion and the following axial compression tests are carried out. The damage and
failure modes of UHPCC-FST columns are reproduced and validated by comparing
with the experimental data. Finally, the related parametric influences, e.g., thickness
and strength of steel tube, compressive strength of core concrete and column diameter, on the local blast formed crater depth, the post-blast residual axial load bearing
capacity, as well as the corresponding damage index of UHPCC-FST column under
contact detonation are discussed. The influential degree of above parameters on the
residual axial capacity of UHPCC-FST columns under contact explosion is clarified. The present work can provide helpful references for evaluating the post-blast
performance as well as the design of UHPCC-FST column under contact explosion.