Page 328 - Forensic Structural Engineering Handbook

TEMPORARY STRUCTURES IN CONSTRUCTION 10.17

leaving questions hanging in the air, 12 cases of temporary structure failures are described
here very briefly. It is pointed out that the conclusions offered are those that have been
formulated and/or published by one or more investigators, and appear to have “carried the
day.” Different investigators may come to different conclusions for the same event from the
same data, and even trials by jury can come to surprising decisions.
Some of these cases were publicized catastrophes with tragic fatalities, others were
obscure events known only to those involved. They were selected for inclusion here to
illustrate the kinds of errors, omissions, and goofs that can cause temporary structure fail-
ures. Four of the cases were summarized from reports of investigations by NIST (formerly
NBS) and OSHA; two from the records of the Worker’s Compensation Board of British
Columbia; two were contributed by individuals; and four came from the author’s job files
of his own forensic consulting practice.
A reader with particular interest in reading case histories will find a number of con-
struction failures discussed in the recently published book that is a collection of forensic
case studies. 9
It is noted once again that reciting the highlights of failures and the summaries of con-
clusions of their investigations in rudimentary fashion may be meaningless, and may even
be misleading, without the reader being given all of the details, and without the reporter
himself or herself having been involved in the case. It is also noted that the causes of fail-
ures stated in these case histories may not have been agreed upon by all the investigators.
In some failures, there is no consensus even years or decades later. Nearly all failures lead
to disputes, nearly all disputes lead to claims and forensic investigations, and nearly all
forensic investigations lead to differences in the conclusions of the opposing parties.
Recitation of case histories are usually based on one investigator’s opinion, and are written
so as to lead up to or justify that conclusion—without rebuttal or challenge. So, be careful
with what you “learn” from a failure.

Case History 1: Riley Road Interchange Falsework
Three spans of an elevated highway, the Riley Road Interchange Ramp C (also known as
the Cline Avenue Bridge) in East Chicago, Indiana, failed during its construction on April
15, 1982. The entire 180 ft of one span, and 160 ft and 135 ft, respectively, of two adjoin-
ing 180-ft spans, collapsed, killing 13 and injuring 18 workers. On the day of the collapse,
workers had been casting concrete in one of the spans. The failure occurred before post-
tensioning of the cast-in-place concrete superstructure when all the construction loads were
still carried by the falsework/shoring.
At the request of OSHA, NBS conducted an investigation to determine the most proba-
ble cause of the collapse. NBS researchers concluded that the collapse most likely was trig-
gered by the cracking of a concrete pad under a leg of one of the shoring towers which were
to support the ramp during construction. This initial failure occurred because the pads did
not have an adequate margin of safety to support the loads.
The initial failure of the pads caused additional tower components to fail, leading to the
collapse of the support system as well as major segments of the partially completed ramp.
The support tower location where the collapse most likely began was pinpointed by NBS
engineers, who also reported the most likely sequence of failure.
Three other deficiencies were identified that did not trigger the collapse but contributed
directly to it:
• Specified wedges that were to have been placed between steel crossbeams and stringer
beams at the top of the support system (or falsework) to compensate for the slope of the
roadway were omitted, thus increasing the load on critical pads.