Blast Mitigation

Protection of assets such as buildings, pipelines, transmission towers and substations etc. has become an important part of any city, municipality, county or country. ADI has the capability to design protection systems against blast loading. An example blast problem and the solution (e.g. up armoring of vehicle floors) are shown in Figs. 8 and 9 where a 1.2 m x 1.2 m panel is subjected to a TNT blast at a standoff distance of 0.4 m. Simply by varying the shape of the panel while maintaining the overall weight constant, the maximum displacement of the panel, the maximum plastic strain, and the momentum of the panel can be decreased by as much as 80% when compared to the conventional flat panel design.


Fig. 8: Schematic diagram of blast loading


Fig. 9(a). One possible solution 

Flat Place

Double Bulge Sine Curved Plate

Double Bulge Sine Curved Plate

Double Bulge Cubic-Bezier Curved Plate
Fig. 9(b) Alternate solutions

 

Blast mitigation solutions for buildings can be generated at various levels. An existing building can be strengthened first by upgrading the strength of the columns followed by a careful examination of connections such as wall-to-wall, wall-to-floor, column-slab, etc. Composite materials provide the best energy absorbing and shielding properties. For example, confinement of columns is essential to improving the blast-resistant capacity and this can be achieved by wrapping the columns with aramic fibers, or through section enlargement using reinforced concrete or composite jackets. Column caps, drop panels and similar concepts can be used to lessen the dynamic effect of blasts by strengthening the shear and bending resistance of the building components. A systematic study is necessary in order to arrive at a cost-effective solution.


FE Half-Model

Principal Stress Plot

Blast Pressure vs Time Data
Fig. 10 Blast mitigation using off-the-shelf materials

 

The range of innovative solutions for new buildings is more varied. These include placing the buidings with as large a standoff distance as possible, using more advanced composites such as steel-reinforced polymers (SRP) and fiber reinforced polymers (FRP), shielding a building using cast-in-place or pre-cast exterior walls, appropriate placement of blast curtains etc. While conventional thinking may dictate that heavier and stiffer buildings do better, reality is that careful placement of material can reduce the dynamic response significantly.