Many such cases when contractors underestimate form pressure from wet concrete.

Concrete is 2.5 times denser than water.

Concrete works well in compression, but has little tension capacity.

The hollow section provided enough area of concrete to resist the maximum compression loads.

By using a hollow pier section, the Key Bridge engineers reduced the weight of the column legs by about 50%. 5/9

The Francis Scott Key Bridge fell after the MV DALI lost power and struck a channel pier.

The pier column was hollow.

In this 🧵 details about the reinforced concrete pier design of the Key Bridge. 1/9

Do not ever straighten rebar like this.

I cannot emphasize how bad this is for structural integrity of reinforced concrete structures.