Blast response of portable buildings in petrochemical facilities

An Office Container was tested for 1250+ lbs ANFO charge (1000 lbs of TNT equivalent charge) at 110 ft standoff distance. The damage observed in the container during the test was in the "Low Response Range". The damage of non-structural components (e.g. conduit pipes, light fixtures, HVAC units and interior wall sheating) was minor. No damage was observed for the inside occupant. The test and analyses showed that the container will experience less damage for the design load (5 psi, 150 ms free field). Blast load design specifications of 5 psi refer to long duration (150 msec) free-field pressures and this does not mean that container could not withstand higher reflected pressures. Front and end-walls were exposed to peak reflected pressures of approximately 20 psi (short duration blast) with minimal or no damage. Doors opened at the time of maximum negative net pressures, that is, between 87-90 milliseconds. Net peak pressures of +3.8 and -2 psi were seen at the back wall exposing door latches to an approximate net suction peak force in excess of 3100 pounds. Blast load estimations proved to match reasonably well with measured pressures. Estimated permanent sliding displacement of the container compared well with actual acceleration-derived displacements and passive-measured displacements, that is, between 0.6 - 0.75 inches. Tipping was found to be negligible.