Analysis of reinforced concrete floor slabs for storm shelters

On-grade concrete floor slabs are very important structural components of above ground storm shelters. A structurally sound floor slab is required to ensure sufficient support for the shelter during an extreme wind event.

In this research an analytical approach has been followed to understand the flexural behavior of the floor slab during an F5-tornado. The slab is assumed to support a storm shelter (8’x 4’x 8’ and 8’x 8’x 8’) that is subjected to wind having 250 mph 3-sec gust ground level wind speed. ALGOR finite element analysis package was used to model the concrete floor slab and simulate the required field conditions. Moment-carrying capacity of uncracked reinforced concrete slab and its reserve flexural strength after cracking were used to monitor the stress levels in the slab. Based on this analysis, design provisions (slab thickness and steel reinforcement) are suggested for the selected slab-shelter configurations. Also, the slab material at the slab-shelter connection was checked for strength against the maximum pullout force transferred by the anchor bolt. It can be concluded that this analytical procedure provides a useful tool in designing floor slabs for storm shelters.