Archaeological discoveries

What makes Anderson shelters a strong structure?

Anderson shelters derived their strength primarily from their corrugated sheet metal design and the soil covering that surrounded them. Here are the critical factors that contributed to their structural integrity:

1. Corrugated Sheet Metal:

- Anderson shelters were constructed using curved, corrugated sheet metal.

- The corrugations created a series of arches, increasing the shelter's resistance to collapse even under significant pressure.

- The arch-like shape distributed the weight of the soil covering more evenly, preventing it from concentrating at a single point and causing a cave-in.

2. Soil Covering:

- Anderson shelters were designed to be covered with at least three feet of earth on all sides.

- The weight of the soil provided compression strength to the shelter, essentially compacting the structure and stabilizing it against external forces.

- In the event of a blast or falling debris, the soil covering further cushioned the impact, absorbing much of the force and shielding the occupants inside.

3. Rounded End Walls:

- Anderson shelters had rounded end walls made of brick or concrete, creating strong anchors connecting the curved metal shell to the ground.

- These end walls acted as buttresses, resisting the sideways movement of the shelter under pressure.

4. Internal Support Structures:

- In some Anderson shelters, additional support structures were incorporated to enhance their strength. These included timber joists, steel girders, or reinforced concrete posts.

- These internal supports helped counteract the external pressures and keep the structure intact.

5. Reinforcements Near Openings:

- Particular attention was given to the entrances and ventilation holes in Anderson shelters. These areas were susceptible to weakening the overall structure.

- To address this, reinforced concrete surrounds or additional metal bracing were often used to support and strengthen these points of entry.

Overall, the combined strength of the corrugated sheet metal, substantial soil covering, rounded end walls, internal supports, and reinforcements created a resilient structure that could withstand bomb blasts and falling debris during the air raids