On 29-Apr-2005, "J. Clarke" wrote:

Concrete for example
doesn't flex noticeably before it breaks so by your reasoning concrete
should never be used as a building material.

Concrete is a perfect example of the problem and one where overdesign is
a problem. Too much steel reinforcement in a small beam compared to less
steel in a deeper beam - the lightly reinforced beam will fail slowly with
the ductile steel failing in tension. The overbuilt beam with too much
steel will fail suddenly and in a brittle manner by failure of the concrete
in compression.

When dealing with wooden beams, making the beam stronger than called for is
not going to result in sudden failure with no warning unless the original
design would also fail suddenly with no warning at a lighter load.

The lighter beam would bend considerably before failure. The heavy beam
can carry a significant overload and can cause it's supports to fail without
warning. You can't look at a building by considering its components individually.
You have to look at the entire structure as a system.

I would like you to quote the statute which makes it a criminal offense to
build something stronger than is required.

If an engineer or architect is responsible for the design of a building,
they are required to ensure that it does not fail in a manner that does not
give warning (i.e it must fail in a ductile manner). If the design of one
component results in an unexpected failure, whether from over- or underdesign,
this results in professional liability. Maybe not the Code of Hammurabi, but
there are still legal consequences - such as criminal negligence causing death.

Mike