After the 950-ton pedestrian bridge collapse at Miami’s Florida International University Thursday, news reports are counting between six and seven fatalities so far and scores of injuries since the overpass walkway pancaked on the six-lane highway below.
The devastating scene soon after the collapse still speaks for itself. The bridge builders used accelerated bridge construction (ABC) techniques, an approach that has been spreading in heavy construction projects that are often hampered by hidebound procedures. But clearly, something went very wrong and is bound to put the builders’ ABC techniques and safety records under scrutiny.
From a safety perspective, college campuses rate as among the more difficult areas for construction projects and layout planning, for fairly simple reasons. Constructors have to work around tight spaces with cranes and heavy equipment, erect scaffolding and cordon off live construction zones and all the hazards they hold to accommodate the heavy foot-traffic of students and faculty nearby. It’s not unlike the challenge of building in New York city.
According to reports from bystanders and news outlets, the walkway had not opened to pedestrian traffic after its completion this past Saturday.
Miami New Times reports that two of the biggest firms that built the pedestrian bridge “have recently been accused of unsafe practices. In one of those cases, another bridge project toppled onto workers.”
The Miami Herald’s report looks at accelerated bridge construction and puts the innovative approach into some context:
The unfinished pedestrian overpass that toppled onto the Tamiami Trail on Thursday was being built under a relatively novel approach called accelerated bridge construction — a fast, tested method that carries some risks if not rigorously carried out.
Until it’s fully secured, a quick-build structure is unstable and requires the utmost precision as construction continues. Properly shoring up the bridge can take weeks, a period during which even small mistakes can compound and cause a partial or total collapse, said Amjad Aref, a researcher at University at Buffalo’s Institute of Bridge Engineering.
As CBSLocal reported on March 10, the builders used ABC techniques to reduce risks to workers, commuters and pedestrians, while preventing traffic jams in the area.
The move was the largest pedestrian bridge move via Self-Propelled Modular Transportation, in U.S. history.
The National Transportation Safety Board (NTSB) is looking into the accident, as are the Occupational Safety and Health Administration (OSHA) and engineering groups of many disciplines (structural, civil, for example) to figure out what went so horribly wrong.
At the very least, the investigation is bound to result in some changes in ABC procedures if it turns out speed or pressure to rush testing may have overwhelmed structural tests of the bridge’s integrity during the critical phases of swinging the key load bearing sections into place. WBZ’s footage below is from soon after the collapse Thursday:
— WBZ | CBS Boston News (@wbz) March 15, 2018