10.8 Parametric Study
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contact detonation, the core concrete can be effectively confined although the slight
spalling damage may occur, thus the higher residual axial capacity of the column
will be achieved. Besides, for the explosion scenario, the generated blast wave would
engulf the column instantaneously. Although increasing the core concrete diameter
would improve both the original and residual axial capacity of the column, more blast
energy would be absorbed by the core concrete due to the less blast wave diffraction
of the lager sectional column, which may cause more extensive damage of the core
concrete in the vicinity of detonation point.
10.9 Summary
In this Chapter, aiming to assess the performance of UHPCC-FST bridge column
against the potential terroristic contact explosions, the residual axial capacity
of UHPCC-FST columns under contact explosion is studied experimentally and
numerically. The main works and conclusions are as follows:
(1) Considering the prototype of UHPCC-FST bridge columns with the diameter of
800 mm under the suitcase or vehicle bombs attacks, five 1/4 scaled UHPCCFST cylinder columns were fabricated, with the average cubic compressive
strength and direct tensile strength of UHPCC being 131.5 and 9 MPa. Three
UHPCC-FST columns were tested under contact explosion with the TNT
charge weights of 1 kg, 2 kg and 3 kg, respectively. The localized craters
were formed and the integrity of the columns was maintained under 1 and 2 kg
TNT explosions (corresponding to the prototype of 64 and 128 kg). The blast
energy can be fully absorbed by the steel tube and the core UHPCC. The outer
steel tube was seriously ruptured and the core UHPCC was fully crushed for
3 kg TNT explosion (corresponding to the prototype of 192 kg).
(2) The axial compression test was further carried out for both the intact and
blast-damaged UHPCC-FST columns, and the relationship between the axial
load and axial/lateral displacement was derived. Both the intact and blastdamaged columns exhibited the diagonal shear failure mode induced by the
shear dilatation of core UHPCC and the bulging of steel tube. The shear failure
plane occurred at the location of the blast induced crater, and the corresponding
angles between the failure plane and the longitudinal axis were in the range
of 24°–29°. The axial capacity of intact column predicted by EUROCODE4 agreed well with the present test data, and the Chinese standard GB50936
was suggested to improve for UHPCC-FST. The quantitative dependence of
column damage index on the charge weight was experimentally determined.
(3) The present established numerical model can reproduce the dynamic behavior
of the UHPCC-FST column under low-yield TNT charge contact detonation
very well in terms of damaged pattern and crater dimension. However, due to
the adopted erosion technique for the steel tube material, the fracturing behavior
of which in the C-3 column under 3 kg TNT contact detonation cannot be fully
363
contact detonation, the core concrete can be effectively confined although the slight
spalling damage may occur, thus the higher residual axial capacity of the column
will be achieved. Besides, for the explosion scenario, the generated blast wave would
engulf the column instantaneously. Although increasing the core concrete diameter
would improve both the original and residual axial capacity of the column, more blast
energy would be absorbed by the core concrete due to the less blast wave diffraction
of the lager sectional column, which may cause more extensive damage of the core
concrete in the vicinity of detonation point.
10.9 Summary
In this Chapter, aiming to assess the performance of UHPCC-FST bridge column
against the potential terroristic contact explosions, the residual axial capacity
of UHPCC-FST columns under contact explosion is studied experimentally and
numerically. The main works and conclusions are as follows:
(1) Considering the prototype of UHPCC-FST bridge columns with the diameter of
800 mm under the suitcase or vehicle bombs attacks, five 1/4 scaled UHPCCFST cylinder columns were fabricated, with the average cubic compressive
strength and direct tensile strength of UHPCC being 131.5 and 9 MPa. Three
UHPCC-FST columns were tested under contact explosion with the TNT
charge weights of 1 kg, 2 kg and 3 kg, respectively. The localized craters
were formed and the integrity of the columns was maintained under 1 and 2 kg
TNT explosions (corresponding to the prototype of 64 and 128 kg). The blast
energy can be fully absorbed by the steel tube and the core UHPCC. The outer
steel tube was seriously ruptured and the core UHPCC was fully crushed for
3 kg TNT explosion (corresponding to the prototype of 192 kg).
(2) The axial compression test was further carried out for both the intact and
blast-damaged UHPCC-FST columns, and the relationship between the axial
load and axial/lateral displacement was derived. Both the intact and blastdamaged columns exhibited the diagonal shear failure mode induced by the
shear dilatation of core UHPCC and the bulging of steel tube. The shear failure
plane occurred at the location of the blast induced crater, and the corresponding
angles between the failure plane and the longitudinal axis were in the range
of 24°–29°. The axial capacity of intact column predicted by EUROCODE4 agreed well with the present test data, and the Chinese standard GB50936
was suggested to improve for UHPCC-FST. The quantitative dependence of
column damage index on the charge weight was experimentally determined.
(3) The present established numerical model can reproduce the dynamic behavior
of the UHPCC-FST column under low-yield TNT charge contact detonation
very well in terms of damaged pattern and crater dimension. However, due to
the adopted erosion technique for the steel tube material, the fracturing behavior
of which in the C-3 column under 3 kg TNT contact detonation cannot be fully