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 district.

"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 building."

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.

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