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12 Experimental Study on the Residual Seismic Resistance of UHPCC …
It is found that the fracture of C-12 column occurred at the position of blast
induced crater, while the rupture of steel tube occurred near the bottom of
column base for C-11 specimen. It can be concluded that when the loading
direction was perpendicular to the crater, the residual seismic resistance of the
post-blast specimen was significantly reduced by the contact detonation.
(v) C-13 specimen was the post-blast column after 2 kg TNT contact detonation.
In the cyclic loading test, the loading direction for C-13 specimen was perpendicular to the crater, which was identical with C-12 column. When the lateral
displacement reached 140 mm, the plastic hinge occurred at the crater, not at
the bottom of the column. At the negative loading phase of the 1st cycle of
= 160 mm, one transverse crack occurred in the cratering position with
the height of 250 mm from the top surface of column base. At the negative
loading phase of the 2nd cycle of = 160 mm, the second transverse crack
developed at the height of 175 mm with the lateral load dropping to 76% of
the negative peak load. Up to the negative loading phase of the 3rd cycle of
= 160 mm, the lateral load-carrying capacity of the column decreased to 38%
of the peak load, and hence the test is stopped. During the test, two horizontal
cracks subsequently developed at the crater to weaken the loading, and hence
the lateral load-carrying capacity of C-13 column did not decrease rapidly.
Since C-13 column sustained two more cycles at the lateral displacement of
160 mm compared to that of C-12 specimen, it exhibited more severe damage.
However, it does not mean that the seismic performance of C-13 is superior to
that of C-12, because under the same displacement condition, the resistance
of C-12 is greater than that of C-13.
(vi) C-14 specimen was the post-blast column after 3 kg TNT contact detonation.
The loading direction for C-13 specimen was perpendicular to the face of
the crater, which was the same as that of C-12 and C-13 specimens. It is
observed that when the lateral displacement reached 100 mm, the plastic
hinge developed at the crater. At the negative loading phase of the 2nd cycle
of = 120 mm, an obvious transverse crack occurred in the area of the
crater at the height of 250 mm. Meanwhile, the lateral load-carrying capacity
quickly dropped to zero, indicating the specimen was suffered total failure.
Therefore, with increasing the charge weight, the residual seismic resistance
of the post-blast column deteriorated continuously as expected.
Based on above experimental observations of specimens under lateral cyclic
loading, it can be concluded that,
(i) II-1, II-2 and C-11 specimens exhibited the bending failure mode under the
lateral cyclic loading. The critical section (or the weakest section) of the column
was near the bottom of column where the plastic hinge continually developed. It
is observed that before the failure of the column, the steel tube firstly exhibited
dilated buckling at the plastic hinge under the cyclic loading. With elevating
the loading level, the steel tube at the plastic hinge tended to suffer brittle
fracture, where one major transverse crack developed near the bottom of the
column. The heights of plastic hinge were about 50 mm for both II-1 and II-2
12 Experimental Study on the Residual Seismic Resistance of UHPCC …
It is found that the fracture of C-12 column occurred at the position of blast
induced crater, while the rupture of steel tube occurred near the bottom of
column base for C-11 specimen. It can be concluded that when the loading
direction was perpendicular to the crater, the residual seismic resistance of the
post-blast specimen was significantly reduced by the contact detonation.
(v) C-13 specimen was the post-blast column after 2 kg TNT contact detonation.
In the cyclic loading test, the loading direction for C-13 specimen was perpendicular to the crater, which was identical with C-12 column. When the lateral
displacement reached 140 mm, the plastic hinge occurred at the crater, not at
the bottom of the column. At the negative loading phase of the 1st cycle of
= 160 mm, one transverse crack occurred in the cratering position with
the height of 250 mm from the top surface of column base. At the negative
loading phase of the 2nd cycle of = 160 mm, the second transverse crack
developed at the height of 175 mm with the lateral load dropping to 76% of
the negative peak load. Up to the negative loading phase of the 3rd cycle of
= 160 mm, the lateral load-carrying capacity of the column decreased to 38%
of the peak load, and hence the test is stopped. During the test, two horizontal
cracks subsequently developed at the crater to weaken the loading, and hence
the lateral load-carrying capacity of C-13 column did not decrease rapidly.
Since C-13 column sustained two more cycles at the lateral displacement of
160 mm compared to that of C-12 specimen, it exhibited more severe damage.
However, it does not mean that the seismic performance of C-13 is superior to
that of C-12, because under the same displacement condition, the resistance
of C-12 is greater than that of C-13.
(vi) C-14 specimen was the post-blast column after 3 kg TNT contact detonation.
The loading direction for C-13 specimen was perpendicular to the face of
the crater, which was the same as that of C-12 and C-13 specimens. It is
observed that when the lateral displacement reached 100 mm, the plastic
hinge developed at the crater. At the negative loading phase of the 2nd cycle
of = 120 mm, an obvious transverse crack occurred in the area of the
crater at the height of 250 mm. Meanwhile, the lateral load-carrying capacity
quickly dropped to zero, indicating the specimen was suffered total failure.
Therefore, with increasing the charge weight, the residual seismic resistance
of the post-blast column deteriorated continuously as expected.
Based on above experimental observations of specimens under lateral cyclic
loading, it can be concluded that,
(i) II-1, II-2 and C-11 specimens exhibited the bending failure mode under the
lateral cyclic loading. The critical section (or the weakest section) of the column
was near the bottom of column where the plastic hinge continually developed. It
is observed that before the failure of the column, the steel tube firstly exhibited
dilated buckling at the plastic hinge under the cyclic loading. With elevating
the loading level, the steel tube at the plastic hinge tended to suffer brittle
fracture, where one major transverse crack developed near the bottom of the
column. The heights of plastic hinge were about 50 mm for both II-1 and II-2