ndustry, including the Mitsubishi
Steel and Arms Works, the Mitsubishi-Urakami Ordnance Works (Torpedo
Works), and numerous factories, factory training schools, and other
industrial establishments, with a minimum destruction of dwellings and
consequently, a minimum amount of casualties. Had the bomb been
dropped farther south, the Mitsubishi-Urakami Ordnance Works would not
have been so severely damaged, but the main business and residential
districts of Nagasaki would have sustained much greater damage
casualties.

Calculations show that the structural steel and reinforced concrete
frames which survived the blast fairly close to X could not have
withstood the estimated peak pressures developed against the total
areas presented by the sides and roof of the buildings. The survival
of these frames is explained by the fact that they were not actually
required to withstand the peak pressure because the windows were
quickly knocked out and roof and siding stripped off thereby reducing
total area and relieving the pressure. While this saved the building
frame, it permitted severe damage to building interior and contents,
and injuries to the building occupants. Buildings without large panel
openings through which the pressure could dissipate were completely
crushed, even when their frames were as strong as those which survived.

The damage sustained by reinforced concrete buildings depended both on
the proximity to X and the type and strength of the reinforced concrete
construction. Some of the buildings with reinforced concrete frames
also had reinforced concrete walls, ceilings, and partitions, while
others had brick or concrete tile walls covered either with plaster or
ornamental stone, with partitions of metal, glass, and plaster. With
the exception of the Nagasaki Medical School and Hospital group, which
was designed to withstand earthquakes and was therefore of heavier
construction than most American structures, most of the reinforced
concrete structures could be classified only as fair, with concrete of
low strength and density, with many of the columns, beams, and slabs
underdesigned and improperly reinforced. These facts account for some
of the structural failures which occured.

In general, the atomic bomb explosion damaged all windows and ripped
out, bent, or twisted most of the steel window or door sashes, ripped
doors from hinges, damaged all suspended wood, metal, and plaster
ceilings. The blast concus