It is distressing to see multi-storey buildings in Gaza collapsing after one missile strike. It is more distressing to know that many of our brothers and sisters in humanity are buried under that rubble. Structural Engineers must now consider the impact loads of military missile strikes in their designs.
A building will not likely survive repeated bomb explosions, but we should have two design aims. The first is that a multi-storey building should not collapse after the first missile strike, assuming that the first missile strike is to eliminate enemy targets near external walls.
If the intent is to destroy the building, then the first strike should give occupants enough time to escape while the decision to order another strike is implemented. The time for occupants to evacuate a building is based on the floor area, exit locations and number of stories. Therefore, the second strike can be timed to allow occupants to safely escape – otherwise the intent is evidently murder.
The second design aim is that a collapsed multi-storey building should not trap occupants inside, and should allow rescuers access to save injured persons.
ACHIEVING THE DESIGN AIMS
To achieve the first design aim, the exterior columns and walls supporting the floors should be designed as sacrificial. Therefore, a building should be designed to remain standing if all external columns and walls are destroyed. This can be done by ensuring that the entire building can be supported by internal columns and walls.
To achieve the second design aim, floors should be supported by beams connected to columns or walls. The bottom of the beams should be at least 600 mm (2 ft) below the bottom of the slab. At the mid-span of each beam at the bottom of the slab, there should be a 600 mm (2 ft) wide and 460 mm (18”) deep manhole in the beam.
Once the columns or walls have been destroyed and the building has collapsed, persons may be able to crawl around the 600 mm (2 ft) space and through the manholes in the beams to escape. Rescuers may also use these manholes in each beam to rescue injured persons.
The additional cost of building in this manner should be minimal, but the benefits are significant, especially for buildings that may collapse by other means, for example: earthquakes, fires, or accidental impacts.
All multi-storey buildings to be rebuilt in Gaza and any country that may be vulnerable to war and/or earthquakes, should consider this design suggestion to limit unnecessary deaths.