DISCONNECTED Separation of slabs from the wall have raised questions about how needed ties were made. (Photo by Richard Korman for ENR)

Missing or improperly made connections between the collapsed floor slabs and a stranded wall that eerily remained standing over debris have become another focus of the probe into the Oct. 30 collapse of a section of an Atlantic City, N.J., casino garage that killed four workers, ENR has learned.

Few project participants or observers would speak on the record. The shear wall at the Tropicana resort has subsequently been demolished because of concern it would collapse but sources familiar with the investigation say its pieces have been carefully examined and stored.

The collapse occurred during concrete placement on the eighth level of the garage’s end section. Missing connections would partly explain why the wall remained standing, with some structural mesh hanging from it and forms still attached at its top level. That kind of deficiency also could have contributed to instability that, along with other possible mistakes in building the garage bay such as inadequate shoring or too little cure time for concrete, opened the way for the collapse, sources say.

The folded slabs still hinged at one end have become signature images of the accident, but investigators also are examining the place where the floors and wall separated. "Something terrible happened at the one line," where the floors and wall pulled apart, says one source.

The project was being constructed with the widely used filigree wideslab method, in which precast forms combine with cast-in-place concrete to create a composite structure. The method saves time and money, say proponents.

Stephen DeSimone, principal of the garage’s structural designer, DeSimone Consulting Engineers, New York City, says the floor-to-wall connection was properly designed. "There’s rebar indicated on my drawings" tying the two elements together, he says. "It’s too early to speculate whether it’s put in or not."

But others involved in the project claim that rebar tying the floor slabs to the wall, or dowels projecting from the wall that would have connected to the floors, appeared to be missing in preliminary reviews of the accident scene.

"A lot of people see that there isn’t any [rebar] there and wonder whether it is a cause of collapse and whether it has become a point of contention," says one source. Poor shoring and other factors at the site may have provided the trigger, while slab-to-wall connections played a secondary role. "Did it exacerbate things? It may well have," he says.

Source: Mid-State Filigree System; Boca Evaluation Services

Another contractor who worked on the project claims that no significant rebar ties the wall to the floors. "The wall worked, but there was no connection to the floors," he says.

Missing or inadequate floor-to-wall connections fit the emerging picture of the project as it rushed to meet a March 2004 opening date. The 2,400-car garage was a key part of the $245-million Tropicana expansion, the biggest project in Atlantic City in a decade. The pressure to move faster was felt all over the site, people on the project say, and patience and materials often were in short supply. The big rush came after the heavy winter weather subsided. "The past months were very intense," says one contractor.

Exactly what changes or decisions were made in the field by the contractor’s staff and what design details and shop drawings were created and reviewed by members of the project team remain unclear. "We’re not making any statements," says an employee who answered the phone at Fabi Construction Co., Egg Harbor Township, N.J. The project’s main concrete contractor, Keating Building Corp., Philadelphia, has also declined to comment on the possible cause and has cautioned against speculation.

Interest in the shoring was boosted by workers who reported seeing shoring poles bowed or bent. An executive with a shoring subcontractor engaged on the project, Peri Formwork Systems Inc., Baltimore, says his company was not involved with the part of the building that failed. "We were not shoring the area that collapsed," says Harvey Evans, Peri’s chief executive officer. "Fabi used its own equipment under the filigreed wideslabs." He declined further comment and Fabi officials couldn’t be reached.

Concerns about whether shoring was involved have been elevated by accounts of an accident that occurred on part of the project almost one year before the disaster. In October 2002, three workers fell 30 ft when a concrete section in a walkway across the street from the garage broke apart. Eugene McDermott, executive vice president of Mid-State Filigree Systems Inc., Cranbury, N.J., claims the mishap was caused by a missing line of shoring. Mid-State Filigree supplied the precast pieces to the Tropicana project, including the garage.

The U.S. Occupational Safety and Health Administration proposed fines against Fabi and Keating in connection with last year’s accident. Penalties concerned a lack of fall protection. Fabi’s proposed fine of $8,375 has subsequently been reduced to $3,375, according to OSHA records. Along with shoring, a series of problems involving connections and responsibility for details now appears to be behind the recent collapse.