# Black Loaded Columns--State of the Art Review
## 2 Experimental Testing
### Bridge Columns
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Author** & **Year** & **Structural Element** & **Experiment Type** & **Material** & **Scale** \\ \hline [PERSON] et al. (2019) & 2017 & Building column & Field & UHPC + HSRC & 1:1 \\ [PERSON] et al. (2016) & 2017 & Bridge column & Field & CFDST & 1:4 \\ [PERSON] et al. (2018) & 2018 & Column & Field & RC & 1:1 \\ [PERSON] et al. (2018) & 2019 & Column & Field & RC & 1:1 \\ [PERSON] et al. (2019) & 2020 & Bridge column & Field & UHPC-FST & 1:4 \\ [PERSON] et al. (2019) & 2020 & Column & Shock tube & RC and RC + CFRP & 1:2 \\ [PERSON] and [PERSON] (2019) & 2020 & Building column & Filed & RC, RC + GFRP & 1:2 \\ \hline \hline \end{tabular} Note. CFCSC—Concrete-Filled Circular Steel Columns, CFST—Concrete-Filled Steel Tube, RC—Reinforored Concrete, SJ—Steel Jacket, MS—Modified Steel Jacket, FRP—Fiber-Reinforored Plastic, SFRC—Steel Fiber-Reinforced Concrete, UHPRRC—Ultra-High Performance Fiber Reinforced Concrete, HRSC—High Strength Reinforced Concrete, CFBT—Concrete-Filled Double-Skin Tubes, UHPC—Ultra-High Performance Concrete, SPRR—Steel Fiber Reinforced Polymer, UHPRR—Ultra-High-Performance Fiber-Reinforced Concrete, CFTT-Concrete-Filled Fiber-Reinforced Polymer (FRP) tube, RPC-FST—Reactive Powder Concrete Filled Steel Tubular, HSRC—High Strength Reinforced Concrete, S. s.—small scale, GFRP—Glass Fiber Reinforced Polymer.  
\end{table} 
Table 1: \(Cont.\)and buckling [7]. [PERSON] and [PERSON] [9], in their work, presented experimental and analytical investigations of seismically ductile RC columns and non-ductile RC columns retrofitted with steel jackets. The charge was set to a height of 0.25 m which corresponds to the actual height of 1 m (car bomb), and at this height, the column experienced the maximum deflection. All columns failed in direct shear at the base, but RC columns with steel jackets did not experience any structural damage, and the RC column experienced spalling of concrete at the bottom. Compared to the CFST columns, these columns did not exhibit a ductile behavior. [PERSON] et al. [8] conducted an experiment in two phases. In the first phase, they tested eight small-scale columns where they first changed the standoff distance and then the amount of explosive charge while the scaled distance was kept fixed. In the second phase, they tested 16 columns in half scale (1:2), where 10 of them were set at a small standoff to observe the mode of failure (flexure or shear) like in [4], and the remaining six were to sustain local damage (spall and breach patterns). In all samples, concrete strength, clear cover, concrete class, and reinforcement grade were unchanged. Boundary conditions for tested columns were assumed to be pinned at the top and fixed at the bottom. The test setup did not include axial load because low levels of axial loads provide greater capacity to the column, and without axial load, tests are on the conservative side. Five experimental observations and guidelines for the design of blast-loaded columns are provided in [4; 8; 35]:  
1. Using protective fences and barriers for vehicles to increase the standoff distance;
2. The circular cross-section can maintain a lower pressure of up to 1/3 concerning a square cross-section of the same dimensions, so the second guideline is to use circular columns, and also, the pressure reducing factors on the circular column were proposed by [PERSON] et al. [2], [PERSON] et al. [36], and [PERSON] et al. [7], respectively, as 0.80, 0.75, and 0.45;
3. Increase in the reinforcement in the column, as this increases the shear capacity, ductility, and confinement of the concrete;
4. Use of continuous reinforcement because discrete hoops can be extracted during a blast load;
5. Placing longitudinal splices away from the charge if they cannot be completely avoided. They also proposed three design categories (A, B, C) that depend on the scaled distance and require a different approach to designing, i.e., gravity, seismic, blast.