Finite element analysis of storm shelters subjected to blast loads

The storm shelter designs presented by FEMA 320, Taking Shelter from the Storm: Building a Safe Room Inside Your House, and FEMA 361, Design and Construction Guidance for Community Shelters, were developed to protect people from the potentially disastrous effect of extreme winds. In these publications, a number of prescriptive designs are presented for small residential and community storm shelters. These shelters are designed to withstand wind-induced pressures associated with 250 mph ground level wind speeds generated by worst-case tornadoes. Designs were developed and tested on the basis of debris impact resistance. Experimental studies conducted on a full scale storm shelter revealed that storm shelters built according to FEMA 320 prescriptive designs can withstand wind-induced overpressures much higher than the design values assumed for worst-case tornadoes. This finding suggests that these shelters might withstand loads associated with low-level explosion pressures.

The storm shelters were analyzed using the finite element method; the same analytical tools were used to analyze the shelters against blast loads. 3D dynamic and static analyses using the ALGOR finite element software package were used to perform this study.

The goals of this research were: studying and applying blast loads on civilian structures; studying the behavior and response of different storm shelters under the effects of blast loads; and studying the differences between the analytical results of the static and dynamic analyses of structures subjected to blast loads. An important objective was to determine the ability of storm shelters to withstand the effects of explosions of various magnitudes at specified distances from the shelters.