Benefits of Thinking Globally
Richard T. Frantz, P.E.
Engineering involvement with property losses demands an open technical mind that
can look at the bigger picture, sometimes beyond the scope of work initially requested
by the adjuster or insurance company. Engineering
law requires the professional engineer to protect "public health, safety, and welfare. "Sometimes
specific technical requests are made to a forensic engineering firm that lead to
much broader technical involvement in order to ensure compliance with engineering
law and the protection of the public. Is
it a benefit for an engineer to look at a broader picture when investigating a loss
event, even if the scope of work has been specified? Let's examine two examples.
Following a large hurricane, a request was made to determine the cause of brick
veneer damage on a large church structure.
Inspection of the building revealed that the structure was an irregularly-shaped
building, which is not uncommon for large church facilities. The hurricane event had produced strong, sustained winds for a short period
of time, resulting in leeward suction wind loads on the high brick veneer face of
the building. At first glance, there appeared
to have been lateral forces on the wall that pulled the brick away from the wall,
resulting in limited failure of the brick ties. Closer examination of the brick wall revealed a bulge in the brick at a mezzanine
level and not the entire height of the wall.
Subtle buckling of the roof and wall surfaces indicated that the shear walls that
resist lateral loads had not responded properly to the wind loads applied to the
building during the storm event. Inspection
of construction drawings revealed that the building framing was changed from a steel-framed
structure to a wood-framed structure to resist the applied wind loads. This was a significant structural modification and required different design
and construction methods. Further investigation
of the building and a structural analysis review determined that the building was
under-designed to handle the code-required design wind conditions. The structure had twisted, resulting in compromise to wood connections throughout
the structure. Even though the structure
had rebounded back to a visually stable condition, suggesting minor cosmetic damage,
the structural performance during the wind event led to condemnation of the structure
for public occupancy. Clearly, relatively
minor cosmetic symptoms can sometimes suggest major problems.
A request was also recently made to investigate the extent of damage to an industrial
concrete warehouse structure built in 1954.
A forklift driver ran his forklift into a concrete column and sheared the column
at the base. The heavy concrete roof sagged
under the weight and shifted the load to an adjacent column, resulting in load failure
to the adjacent column. Fortunately, the
structure appeared to stabilize and did not totally collapse. A contractor was called in by the owner to shore up the roof structure in
the damaged area. Pipe columns were designed
and installed under the beam that was supported by the failed concrete columns.
Several weeks after the accident and temporary repairs, a further inspection of
the structure was required to determine extent of damage. At the time of the initial inspection, the structure appeared to be stable,
and the owner insisted that the installed columns were designed by a professional
engineer. Several days after the initial
site inspection, the adjuster requested an investigation of the concrete that had
fallen from the ceiling. A more detailed
investigation of the "temporary repair" revealed that what was originally assumed
"stable" was under-designed and inadequate for supporting the heavy concrete roof
deck. The concrete deck continued to move,
resulting in further crack distress to the roof deck and other concrete columns. he owner, of course, wanted the structure
repaired and concrete columns installed under the roof deck so that much-needed
operation space could quickly be restored.
However, the structural conditions demanded more area to be cordoned off for occupant
safety.
Emergency shoring and wood cribbing was designed and installed to support a much
larger area of roof deck. The crack patterns
in the structure indicated extensive deformation of the roof deck and severe damage
to column joints and deck sections. In the
absence of material specifications and structural drawings, material testing revealed
that the structure was also deficient in the required concrete strength. Repair
to the observed distress alone would not bring the structure into compliance with
structural code requirements. Ultimately,
it was determined that replacement of a large section of the concrete roof deck
would be required.
Assumptions of adequate "temporary repair" or structural strength can result in
a false sense of security. Thus, an understanding
and review of all conditions when engaged on a site investigation should be made
by the investigating engineer and the scope of work for this effort relayed to the
client.
In summary, careful consideration of the technical qualification of the engineer
or engineering firm for a small or large property loss investigation is essential. A good forensic engineer should not only perform
a proper technical investigation, but also have the ability to think "globally"
on a loss, in order to protect the public, minimize client and owner risks, and
identify conditions beyond the obvious.
