Explosion effects on structures have been an area of research over the last decades. This is mainly due to the fact that structures all over the world are increasingly being exposed to the threat of premeditated explosive attacks, accidental explosions and other forms of explosion related failures. The magnitude of blast loads produced by most explosions are significantly higher than the design loads for conventional structural design.Consequently, this has increased awareness of building owners, government departments as well as design professionals to the vulnerabilities and survivability of structures to blast loading as global terrorist attacks continue at an increasing rate. Although significant amount of work is continuing on the effects of explosions on infrastructure (systems), especially in the USA, experimental work involving live explosive testing is limited. Moreover experimental testing of reinforced concrete columns to blast loading within the close-in range with scaled distance (z) less than 1.0 m/kg 1/3 is scant. This is likely because of the unreliable accuracy and low survivability of most instrumentation in this range. An experimental program was therefore designed to investigate the effects of near-field explosions on reinforced concrete columns with different transverse reinforcement detailing and at different scaled distances (z = 0.22 m/kg 1/3 , z = 0.54 m/kg 1/3 , and z = 0.86 m/kg 1/3 ). The columns were built in the Structures Laboratory at Carleton University, while the live explosive testing was carried out in an open field arena at the Canadian Forces Base (CFB) Petawawa, Ontario.Analysis of the experimental results showed that, the response of the reinforced concrete columns, irrespective of the column type (Conventional, Seismic or Prestressed) failed at ii the scaled distance of 0.22 m/kg 1/3 . As the scaled distance increases, the severity of damage is less. At the higher scaled distance of 0.86 m/kg 1/3 , the response for all columns was relatively the same. The effects of transverse detailing and lap splices was very much pronounced in tests with scaled distance z = 0.22 m/kg 1/3 . Conventional columns severed into two pieces, while seismic column did not. Prestressed columns performed better compared to conventional columns, at scaled distance of z = 0.22 m/kg 1/3 . However, in tests with scaled distances z = 0.54 m/kg 1/3 , the prestressed column suffered severe damage relative to conventional columns.iii

Explosion effects on structures have been an area of active research over the past decades. This is due to the increasing number of terrorists’ action against infrastructures. Although significant amount of work is continuing on the effects of explosions on infrastructures, experimental work involving live explosion testing is limited. Moreover, experimental testing of reinforced concrete (RC) columns subjected to near-field explosions is scant. This paper presents results of an experimental program designed to investigate the effects of near-field explosions on RC columns with different tie spacing and at different scaled distances. The results show that the response of columns is strongly dependent on scaled distance. As the scaled distance increased the severity of damage reduced; seismic columns showed better response. The effect of axial loading was also observed to increase the level of damage on reinforced concrete columns at the axial load level and blast loads considered in the test program.