New issue of FIREHOUSE (March 2009) has article by Vincent Dunn, retired FDNY deputy
chief and author of "COLLAPSE OF BURNING BUILDINGS". Dunn goes into detail concerning collapse of WTC 7 - points out fireproofing on steel work - columns coated
with 7/8" (22 mm) of spray on fire proofing, 1/2" (13mm) on floor trusses and 3/8" (10mm) on underside of floor decking. First visible fire was spotted just after noon at least 10 floors were heavily involved (7, 8, 9,10, 11, 13, 22, 29, 30 IIRC). Dunn explains that
heat of fires on 13 caused the truss supporting to expand and pull away from floor deck
and dislodge the structural support column. One more thing was that the steel work
was painted with primer paint which affected adhesion of the sprayed on fireproofing
Only subscribers to FIREHOUSE can read the article now - in 2 months will be posted to archives so anyone can read.
Very informative
