# Black Loaded Columns--State of the Art Review
## 2 Experimental Testing
### Building Columns  
In addition to bridges, interesting targets of terrorist attacks are buildings. By damaging the ground floor columns, the whole building loses stability, so in most of the new buildings, the ground floor columns are designed also considering the blast loads. Building columns differ from bridge columns in the magnitude of the axial loads. Moreover, the dimensions of building columns are significantly smaller, so most of the experiments conducted on building columns were in full or half-scale. [PERSON] et al. [11] tested two half-scale reinforced concrete columns and six Steel Fiber-Reinforced Concrete columns (SFRC) with steel fiber content from 0 to 1.5% by volume of concrete (non-seismic and seismic detailing) at shock tube. In the experiment, the axial load equal to 30% load capacity was applied using a hydraulic jack. According to their experiments, columns designed seismically (38 mm distance between transverse reinforcement) have smaller maximum displacements and can withstand larger blast loads. Moreover, SFRC columns with non-seismic detailing (75 mm distance between transverse reinforcement) showed smaller maximum displacements and no secondary blast fragments. \begin{table}
\begin{tabular}{c c c c c} \hline  & **Top** & **Bottom** & **Crack Patterns of Concrete** & **Deformation** \\ \hline CFST [7] & 1.2\({}^{\circ}\) & 3.8\({}^{\circ}\) & No available & Plastic \\  & 2.2\({}^{\circ}\) & 8.3\({}^{\circ}\) & Tension side & Plastic \\  & 4.9\({}^{\circ}\) & 17.0\({}^{\circ}\) & Opening of core concrete & On-set of fracture of column \\  & 18.7\({}^{\circ}\) & - & Blew away & Post-fracture of column \\ \hline RC MS [5] & - & 8.6–10.3\({}^{\circ}\) & Satisfactory ductile behavior & \\ \hline RC [2,36,39]\({}^{\star}\) & - & 1.3\({}^{\circ}\) & Slight to moderate damage & \\  & - & 2\({}^{\circ}\) & Moderate to heavy damage & \\  & - & 3\({}^{\circ}\) & Dose structural integrity & \\ \hline RC [40] & - & 2\({}^{\circ}\) & Minor damage & Onset of shear failure at base \\  & - & 4\({}^{\circ}\) & Collapse & Shear failure at base \\ \hline RC (UFC 3-340-02) [41] & & 2–5\({}^{\circ}\) & Moderate damage & \\  & 5–12\({}^{\circ}\) & Severe damage & \\ \hline RC (AISC 341) [42] & & 2.3\({}^{\circ}\) & Highly ductile & \\ \hline \end{tabular} \({}^{\star}\) Based on experimental testing of concrete beam elements in flexure.  
\end{table} 
Table 2: Maximum support rotations (blast at low height). Figure 7: Damage of UHPCC-FST columns after detonation of: (a) 1 kg; (b) 2 kg and (c) 3 kg of TNT [29]. Copyright permission obtained from authors. [PERSON] et al. [13] experimentally tested nine Ultra-High-Performance Fiber Reinforced Concrete (UHPFRC) columns designed with Compact Reinforced Composite (CRC). Tests were performed in a shock tube, and a hydraulic jack was used to input the axial load. The applied blast pressures varied from 69 kPa to 689 kPa. Dimensions of the cross-section were 152 mm \(\times\) 152 mm, and the free span of the column was 1980 mm. The results showed that the UHPFRC columns reduce secondary blast fragments. Increasing the proportion of fibers from 2% to 4% had a positive effect on the decrease in displacement, but a higher proportion of fibers did not result in improvements in blast behavior. [PERSON] et al. [12] experimentally blast tested three square columns and one circular column. The columns were made from steel tubes filled with concrete (CFST). Specimens were placed horizontally with a simple boundary condition at both ends. A pneumatic jack was used to input the axial load, shown in Figure 8. The entire length of the specimen was 2.5 m. In the experiment, an emulsion explosive, which has a TNT-equivalent of 0.7, was used. The maximum and residual column deformations are provided for blast loads utilizing 17.5 to 35 kg TNT equivalence at a standoff distance of 1.5 m. The concrete inside the steel tube reduced local deformations, and the energy was dissipated through the global response of the element. [PERSON] et al.