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Light Pole Failure

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Two light pole failures in the last three years ... doesn't sound like many,
but the failure mechanism is of some concern.

Central California - 75 mph design wind speed
Some strong winds occurred several months back (40-50 mph gusts)
(Poles did not fail/drop during those storms)

30' tall poles with light standard (about 3 years old)
5" square steel tubes, 1/8" thickness (material spec - not sure)
12" +/- x 1" thick square base plate w/ 4 anchor bolts
The base plates have 5" square holes such that the tube slides within the
base plate thickness
Fillet welds - all around (3/16" or 1/4"? +/-) at top of base plate to tube
AND at bottom edge of tube to 5" square slotted edge of base plate.

Failure has occurred in the steel tube just above the fillet weld between
the top of base plate and the tube section.

Would be interested to hear some opinions or from those who may have
experience with similar failures.

You can also contact me personally at shiner(--nospam--at)

Steven T. Hiner, SE

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