Page 349 - Forensic Structural Engineering Handbook

10.36 CAUSES OF FAILURES

(a)
FIGURE 10.5 A West coast hotel. (a) Collapsed scaffolding. (From R. A. LaTona Simpson, Gumpertz &
Hager, Inc., San Francisco, CA and Civil Engineering, April 1998.)

weld metal was deposited on the outside surface of the pipe, but it was not fully fused to
the metal of the pipe wall. Metallurgical studies showed that the section at the point of the
break had been broken previously, and the bottom chord pipe had cracked around 75 percent
of its circumference. The weld that was intended to repair the putlog only covered the crack
and did little to reestablish the strength of the cross section. The metallurgical examination
also revealed that the repaired bottom chord location failed in a brittle manner (consistent
with the sound like a gunshot and the platform dropping a few inches while the loads trans-
ferred from the putlog bottom chord to the top chord), and that the top chord of the broken