On the front page...
Multi-level parking garage 9, a six-story structure
with room for 936 vehicles, is due to open in September after a
construction delay prompted by the collapse of a section of parking
deck, which killed a worker at the facility last Nov. 29. A review
of the incident, conducted by the Occupational Safety and Health
Administration, is due soon, but the evidence indicates that there
were no design or construction flaws in the project; human error
was almost certainly the cause of the fatality.
"We got a quality project (from lead contractor Coakley Williams Construction Inc.)," said
Leonard Taylor, director of the Office of Research Facilities, "but we just had an awful disaster."
Allyn Kilsheimer, an expert structural engineer called to the
scene by Coakley Williams
just hours after a 30-ton section of pre-cast concrete fell on
construction worker Ronal Alvarado Gochez, rated the MLP-9 project
a “10 — most that I see are 1’s...We have proven
to ourselves that there was not a design flaw. In fact, this project
was designed better than what codes require. There are more things
right with it than any garage I’ve seen built.”
The new garage, located just west of Bldg. 10, had been on schedule
for completion by this spring when workmen returned from a 4-day
Thanksgiving holiday weekend to resume work on the morning of Nov.
29. According to Kilsheimer, president of K.C.E. Structural Engineers,
Gochez had been operating a bottle jack — not much different
from the kind of jack used to change a spare tire — when
the accident occurred.
"The man who died was jacking a tee (T-shaped section of flooring)
to make it level for his partner to weld. It turns out he may have
been jacking two floors instead of one. The tee rolled off its
bearing and landed on him...We're 95-100 percent sure that the
collapse was an unfortunate construction accident."
Kilsheimer said he has investigated 12 collapses in the past 4
years, and that "all but one has been an accident (versus a structural
flaw). I've done 50 or more (collapse investigations) all told,
and every one [that was not terrorist-related] has occurred during
construction, except one." He emphasized that "the construction
process [for pre-cast garages] is substantially more dangerous
than the finished structure. The riskiest period is during construction.
You have to be very careful before reaching the finish line — it's
unstable until all the parts are put together."
There was a second collapse on Nov. 29, later in the evening,
due to instability brought on by the first collapse, but no one
was injured. Project Officer Rozario "Tony" Francis of ORF said
construction of MLP-9 resumed on Feb. 3, after the accident site
was fully examined and debris was removed. He said the garage will
be built to the original specifications, with no change in size
or scope due to the accident. "All elements went back to the original
design because there was nothing wrong with the original design."
NIH hired an independent structural engineer, Norm Scott of Consulting
Engineers Group, to provide overall quality assurance on the investigation,
Francis said. "Cagley & Associates, the design engineer, provided
unique and valuable oversight," noted Kilsheimer. "Although the
circumstances were terrible, it was a pleasure to have [Scott]
working with us. He did a great job under really bad circumstances."
MLP-9, which was designed after 9/11, has a number of features
that make it unusual, Francis explained. The first floor is designed
to handle a progressive collapse of floors above, which might occur
if a small bomb were detonated in the facility. That feature was
inadvertently tested by the Nov. 29 accident, and passed the test.
Second, the garage has a huge basement vault that may eventually
house mechanical systems for Bldg. 10, should they be needed. The
vault and a utility tunnel comprise some 40,500 square feet for
housing emergency generators for electricity, transformers, chilled
water, heat exchangers, vacuum pumps, fuel tank storage and other
building support systems.
The concrete slab forming the roof of the vault, and the first
floor of parking, is 15 inches thick, said Frank Malits, vice president
of Cagley & Associates, a structural engineering firm. Seven or
8 inches is the normal thickness. Even the parking decks themselves
exceed the specifications for supporting load, said Francis.
He enumerated other MLP-9 virtues: the lighting system was designed
for low impact on neighbors, the four elevator towers (two at the
northwest corner, two at the southwest) are see-through and glass-enclosed
for safety, and there is first-floor space reserved both for people
with disabilities and for visitors to the Clinical Center's blood
bank. Even the garage's red-brick facade was a requirement, since
the structure is located within NIH's "historic" architectural
"We are confident that Coakley Williams exceeded our RFP (request
for proposals) requirements," said Francis. "As the design progressed,
there was peer review on both NIH's side and externally. Even before
construction, there were pre-fabrication meetings, site visits,
we oversaw the castings (of concrete and steel). We went through
the whole 9 yards."
Concluded ORF's Taylor, "This job was carefully and properly designed
by the Coakley team. We've had good quality assurance throughout
the project and the erection procedures have been properly scrutinized." In
the wake of the accident, he continued, NIH has done the proper
forensic engineering and all specifications have been re-validated. "We
have as much confidence as you can have about the quality of this
Addressing some NIH'ers' concerns about vibrations and rainwater
leaks in MLP-10, another pre-cast concrete garage located just
east of Bldg. 31, Taylor assured that the structure is secure,
stable and doing what it was designed to do.
Vibrations in the floor are a normal feature of long-span structures
such as parking garages and bridges, Taylor said. "In every instance
where you have long spans and heavy, rolling loads, you get vibrations.
That's not unusual."
Kilsheimer, who spent virtually 4 entire days onsite after the
accident, and another 2 weeks in the field, said he's satisfied
that the post-accident analysis has been carefully and comprehensively
done. He predicted that OSHA, which currently has no regulations
in place governing how pre-cast structures are built, will likely
revisit the topic in the future.