Page 202 - Forensic Structural Engineering Handbook

6.4 ENGINEERING RESPONSE TO FAILURES

Not Collapsed but Failing
Structures that have not collapsed but are showing significant signs of distress or other per-
formance issues should be investigated for the factors that increase load or decrease their
structural capacity. The intent is to identify potential key failure mechanisms and possible
remediation methods to prevent further decrease in performance or load-carrying capacity.
A decision needs to be made as to whether the performance issues will continue to evolve
over time in a negative fashion or whether they are essentially at rest. Has the structure
reached a new state of stable equilibrium in its current deformed position?
If the structure’s load-carrying capacity is intact, other performance issues, e.g., cracking
and excess deflections or vibrations, can be addressed to ensure the serviceability or useful
lifespan of the structure.
Guidelines and methods of evaluating the structural conditions and existing or potential
structural problems of buildings are addressed in Refs. 1, 2, and 3.

EMERGENCY RESPONSE VERSUS FORENSIC
INVESTIGATION

The initial steps in a structural failure investigation depend on when the engineer becomes
involved. The initial call can come immediately after a collapse or some weeks or months
after a problem is first noticed.
The first question to ask is, “Is this an emergency?” Has a structural collapse just
occurred or is one likely to occur immediately? Forensic investigations must wait until the
structure has been stabilized and the danger of additional collapse has been reduced
(Fig. 6.4). In addition, rescue and recovery operations will always take precedence over
a forensic investigation. The risks associated with working on or near structures that
have failed must always be actively addressed throughout both the emergency response

FIGURE 6.4 Risks associated with working in collapse areas must be carefully assessed
throughout an emergency response or failure investigation.