Preliminary Analysis: The Cincinnati Horseshoe Casino Floor Collapse

An Engineer's Perspective on What Went Wrong

Although operations have resumed at the downtown Cincinnati construction site where a second-floor collapse injured more than a dozen workers, questions about both cause and culpability linger.

On the morning of Jan. 27 at the Horseshoe Casino job site, a steel beam supporting the second floor of the structure buckled while concrete was being poured. As a 60-by 60-foot section toppled downward, 13 construction personnel suffered fairly minor injuries, including cuts, bruises, and broken bones, for which they received treatment at a local hospital. One of those workers remains in “serious condition.”

In the ensuing days, the city of Cincinnati and Messer Construction Co. have been fielding a battery of questions amid speculation about the integrity of building practices and safety protocols at the site of the $400 million project.

The official cause of the structural failure—and thus any implied negligence or potential wrongdoing—remains open to conjecture until official reports are issued, pending a full investigation by Occupational Safety & Health Administration (OSHA).

What is known, however, is that construction managers at the Horseshoe Casino job site employed the use of temporary connections, which Amit Ghosh, chief building inspector, described as “a standard building method used today.”

During a meeting with the members of Cincinnati Council’s Sub-Committee on Transportation and Infrastructure, Ghosh explained “the collapse brought changes [to] the construction process,” adding that construction managers have “proposed to make all connections permanent” moving forward to ensure the safety of all parties involved.

“Our project design and safety teams have reviewed all aspects of the construction, safety and inspection protocols, and we are implementing additional procedures to prevent this from happening again,” said Tom Keckeis, Messer president and CEO.

Indeed, certain “additional”  precautions are already discernible at the site, including a second full-time safety manager overseeing the project, and demolition of the collapsed floor, which began on Friday, Feb. 3.

A Nuts-and-Bolts Guide

 

This incident occurred less than a month after a similar Cleveland casino accident. At present, reports are chalking this up to mere coincidence, as developers insist the cases are not linked.  

What follows is Charles C. Roberts’ assessment of what might have caused the failure, based on photographs and information received from various sources. Roberts is a regular contributor to Claims Magazine and is the president of C. Roberts Consulting Engineers Inc., which provides professional engineering services in accident reconstruction, failure analysis, fire causation, explosion analysis, and biomechanics.

Please note this is an initial failure analysis based on Roberts' expertise and in no way constitutes a definitive answer as to the cause of the structural failure. An official determination will be made available when OSHA completes its investigation. For more in-depth coverage of the insurance implications, especially as they pertain to workers’ compensation claims and coverage under standard CGL, stay tuned for commentary from Diana Reitz in the forthcoming March issue of Claims Magazine.

For Roberts' step-by-step examination, click "next."

Our First Look

When a steel beam supporting the casino’s second floor failed as concrete was being poured, the collapsed section formed a “V” (as evident in the image below).

Both OSHA and site developers are proceeding with investigations. The generic deformations and displacement of structural members shown here do yield some clues as to what went wrong.

While loading to the floor increased during the pouring of concrete, the floor collapsed as shown in the preceding photo. The large support beam, a significant structural member, is on the ground, while floor decking is still attached to adjacent beams. There has been discussion that the floor connection to the support beams failed, causing the collapse, but this does not explain how the large support beam ended up on the ground.

Preliminarily, it appears that the floor support beam failed, pulling down the adjacent floor decking in a manner shown in the diagram below. There is ongoing debate about the number and placement of bolts at the time of collapse.

This end view of the large support beam connection shows what appears to be a failed angle connection (arrow) at the second from the top bolt holes. The angle connection points to ductile failure (elongated bolt holes) that would be consistent with only two bolts having been installed in the connection.

Pictured here is the location of the beam connection with the column. A bolt-related failure often leaves the bolts in the original hole. Other photos released to the press suggest that in this case, there may have been only two bolts holding the beam in place. There are twenty bolt holes at the connection area.

 

Moreover, additional photos released by local news sources depict a neighboring column with bolts inserted in the holes, but missing the nuts on several of the bolts. This tends to limit the structural integrity of the connection, especially the moment transmitting capacity.

The connections are designed to have bolts and nuts installed to the proper torque. There are additional views of structural members without the full complement of bolts installed at connections. It should be noted that without completing the bolt installation, structural integrity will be significantly diminished. A bolt in one of the press photos is deforming downward, suggesting that the dead load of the beam is overloading the bolt or that the bolt is not at a proper torque (loose). It appears that the remaining 4 bolts and nuts on this side of the connection are missing.

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