The American Concrete Institute has released a paper which investigates the vulnerability of conventionally designed reinforced concrete (RC) columns against vehicle impacts.
Low-Elevation Impact Tests of Axially Loaded Reinforced Concrete Columns says structures are conventionally designed to resist dead and live loads. However, there is a risk of structural members being subjected to impact loads due to unexpected events, accidents or intentional attacks. Also, street-level columns of buildings and columns in parking spaces can potentially be exposed to high-intensity dynamic loads caused by vehicular impacts. Furthermore, most of these columns are not designed to resist these effects.
For the study, a special drop-weight setup was established to simulate the vehicle collision impact in the performed tests. Four fullscale axially loaded RC members were tested under drop-weight test setups to represent low-elevation transverse impact loads on the specimens.
ACI says: “The performance of RC columns under static and impact loading conditions (applied by increased magnitude of impact energy) was examined and the changes in their structural performances were evaluated.”
The mode of failure was observed to be transformed from pure flexure in static tests into a more brittle character dominated by shear under impact loading conditions.
“Consequently, conventionally designed RC columns were found highly shear-deficient against vehicular impacts; therefore, they should be designed with a certain safety margin to have reserve shear and deformation capacities to eliminate their vulnerability,” ACI adds.
Based on the results, dynamic response ratio recommended for shear-critical RC members can be used in the design of street-level columns against vehicular impact.
This paper was written by Tuba Gurbuz, Alper Ilki, David P. Thambiratnam and Nimal Perera.
