Page 203 - Forensic Structural Engineering Handbook

THE ENGINEERING INVESTIGATION PROCESS 6.5

and the failure investigation. Risks that may be appropriate during rescue operations are
typically unjustified during data collection for a failure investigation. It is a serious mis-
take to get engineers or construction workers hurt, or worse, attempting to collect evidence
under dangerous conditions for later forensic structural investigation.
If the engineer is not called in to investigate until some time after a problem first
becomes apparent, an assessment of the real risks must be made. Is a collapse really likely
if the structure has been standing for a considerable period of time showing some minor
signs of distress? Have the loads changed? Has the structural capacity decreased?
Often an engineer is not called in to investigate a structural failure until long after the
event. The site has been cleared and rebuilding or repair has been undertaken. Data is often
lost or hidden, increasing the difficulty in coming to reasonable certainty in the cause.

SCOPE OF INVESTIGATION

The Importance of Why
A failure investigation must answer the question, “Why did the structure fail?” While this
might seem trivial, it is critical. The engineer should never attempt remedial measures until
he or she is certain of the technical cause(s) of failure.
In addition, it is foolish to opine on who is at fault in the process that led to failure, if
one is not certain of how the failure occurred. An engineer should not accept an investiga-
tion assignment that does not include in its scope the question of why the structure failed.
Be wary of the clients who state, “We don’t need to know why the structure failed, we just
need to know that we did not cause it.”
An engineer needs to perform a thorough investigation before reaching any conclusions.
The core purpose of a structural failure investigation is to determine why the demand on
the structure exceeded the capacity of the structure, or vice versa, why the capacity did not
meet the demand.

Client Needs
Engineers are typically engaged on behalf of interested parties to investigate structural fail-
ures. Some of these parties are listed in Table 6.1.
It is important to understand that each of these clients has different needs with respect
to any structural failure investigation and the engineer must take care to determine an
appropriate scope for each investigation. Engineers can provide expert advice in failure
analysis, causation, loss mitigation, remediation, and litigation support.
Most of the standard-form agreements used by architects and engineers in the construc-
tion industry are intended for new constructed projects or renovations. Therefore, these

TABLE 6.1 Common Clients of the Forensic Investigator

Owners Tenants
Developers Attorneys
Public and government agencies Insurance companies
Plaintiffs in litigation (injured parties) Materials manufacturers
Defendants in litigation (parties involved with the Designers
design, construction, maintenance, or operation) Contractors