r - The Hong Kong Polytechnic University

Figure 11 Relationships between residual strain and impact energy for CFT specimens and CCFT specimens
with different layers of CFRP.
The transverse confinement is also expected to be very effective to improve the performance of concrete and
composite columns subjecting to lateral impacts, which are more often occurred in bridges and other
transportation facilities. In a collaboration project with University of Nebraska, concrete filled tubes were tested
using the large-capacity drop-weight testing equipment developed by the author’s team [Deng et al. 2011].
Several recent incidents around the worlds alerted the society of the threats posed by car bombs by terrorists.
One of the most effective ways to reduce the hazards by car bombs is to set bollards around the important
buildings to enlarge the distance between the point of potential explosion and the crucial buildings. Studies for
the bollards generally only stay in the software analysis phase. The author’s team recently established a field
laboratory of vehicular impact on structures and conducted truck collision tests of concrete filled tube (CFT)
bollards, as shown in Fig.12. The total weight of truck was 6.8 tons, with the speed of about 40 kph collision.
The truck was completely stopped by bollards, and the penetration distance was less than 1 m, in full
compliance with the U.S. standard SD-STD-02.01A under the K4 level. The research shows that concrete filled
tubular bollards system can play a good role in anti-car bomb project measures. Further studies are under way
on testing the effects of confinement on impact behaviour of CFT and RC columns.
CONCLUSIONS
Figure 12 Real field testing of truck collision on CFT bollards
Through the summary review of the development of the transversely confined structural columns, it is clearly
evident that the concept has evolved to a generic design concept for achieving superior performance in structural
columns. The transverse confinement can be applied using steel, reinforced concrete and fiber reinforced
plastics, etc. With transverse confinement, the mechanical behaviours including impact behaviours of structural
columns, such as reinforced concrete, steel or concrete filled tubular columns, etc. are shown to be greatly
improved.
-153-