Special Reports

Constructors to analyze collapse of store in Joplin tornado

With pieces of its damaged roof draped over debris, Home Depot in Joplin, Mo., lay in ruins after an EF-5 tornado swept through the city’s central core on May 22.
With pieces of its damaged roof draped over debris, Home Depot in Joplin, Mo., lay in ruins after an EF-5 tornado swept through the city’s central core on May 22. The Kansas City Star

A construction industry group is investigating the May 22 collapse of the Home Depot store in Joplin, Mo., in light of issues The Kansas City Star raised recently about the tornado-related failure.

“We want the public to know we take this very seriously,” said Jeffrey Needham, a Lenexa structural engineer who is heading the investigation for the Tilt-Up Concrete Association.

The association researches and promotes tilt-up wall construction, in which concrete walls are poured on the ground and then lifted upright with cranes. The walls are held upright by critical connections to a relatively lightweight roof system.

The technique was used in hundreds of Home Depot stores — including the one in Joplin — and has been used in thousands of other buildings nationwide.

The Star reported June 26 that some engineers and tornado experts are concerned about how such big-box stores stand up against tornadoes. The Star also said some engineers have specific concerns about tilt-up wall buildings such as the Joplin Home Depot store, where seven people died when one of the building’s walls fell on them.

The Home Depot store, which met local building codes, was one of 8,500 structures destroyed during Joplin’s EF-5 tornado on May 22.

Needham said The Star’s article was unfairly critical of the tilt-up construction method and left an inaccurate impression that the technique is inherently dangerous.

But in describing the association’s investigation, Needham said: “This is a very serious effort, and we hope to gain a deep understanding of what happened to the (Home Depot) structure that could possibly lead to suggestions for improvements in building codes.”

He said that Home Depot officials will be asked to cooperate in the investigation and that the results of the study will be made available to the engineering and construction community. Home Depot officials said they had heard from the association but had no further comment at this time.

A spokesman for the chain repeated that their engineers “fundamentally disagree” with engineers who take issue with the tilt-up wall technique. In The Star’s report, some of those critics say that under high winds, the roof can be compromised and the panels in tilt-up wall buildings can fall like dominoes.

Needham stressed that tilt-up construction is no different than other construction methods used in big-box stores.

“The basic structural performance of a big-box building, whether it is made of tilt-up walls, precast concrete walls or concrete blocks, is fundamentally the same,” he said.

“The pivotal point is that if you lose the roof deck, the walls fall over.”

He said the association’s investigation will look closely at such things as the building’s roof-to-wall connections, its concrete walls, its steel components and its roof. He said his committee will verify that a structural analysis of the Joplin Home Depot design was completed during construction, as required.

Needham said he does not believe at this point that the Home Depot failure was a result of the use of the tilt-up technique, based on what he’s seen in photos of the collapse. He said those images indicate to him that the failure of the roof system was key and that similar roof systems are used in many big-box stores.

While the investigation will focus on the Joplin Home Depot, he said, the committee of engineers studying the collapse will also look at the partial failures of other nearby buildings, including a Walmart store.

A separate, independent investigation of non-residential building failures in Joplin will get under way soon by the Structural Engineers Association of Kansas and Missouri.

“We are in the beginning stages of forming a committee, separate from the Tilt-Up Association,” said Steve Ashton, the group’s president.