On 12/1/13 7:55 AM, Ken wrote:
I am curious. All this talk about concrete strength, rebar, etc.
Is anyone aware of a tower base failure due to strength of the
concrete or lack of rebar? (Except for damage from a lightning
strike.) From what I hear, the vast majority of tower failures are
20-30' above the base. Base failures? Are they really an issue?
I think it's more that there are a whole lot of towers out there, and
there's no systematic reporting of failures. Everything is anecdote.
You generally don't hear about foundation failures in houses either,
unless there's some sort of litigation on a large scale (e.g. an entire
tract that has foundations without rebar).
As I mentioned, 40 years ago, little was said about base concrete,
rebar, etc. OTOH, 40 years ago, 60' was a big tower. Maybe that's
part of the issue.
Everything in the building trades has gotten more rigorous. Engineering
has gotten better, expectations of city building departments have gone up.
Look at all the changes for seismic and wind related design. 40 years
ago, bolting the house to the foundation wasn't standard practice, and
there's plenty of "soft first story" buildings in Los Angeles that would
never be built today.
There is another scary aspect to this attention. So far, municipalities
tried to regulate towers out of existence because of aesthetic concerns.
PRB-1 did away with that. However, a potentially more effective
approach to do away with towers is to start raising safety issues.
How many hams in suburban areas with 100x100 ft lots could *prove* that
their tower, should it fail, would fall entirely within their lot and
not cause any damage to the house?
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