The structural engineer who won acclaim for his postmortem probe of the 2001 collapse of the World Trade Center towers told a Philadelphia jury Wednesday the deadly 2013 Center City building collapse was "an entirely preventable accident."

Had demolition not resumed the morning of June 5, 2013, testified Najib Abboud, "no lives needed to be lost. Up to that morning this tragedy was preventable."

That morning, as an excavator picked at the remains of the vacant Hoagie City building, an unbraced three- to four-story brick wall toppled and destroyed the adjacent Salvation Army thrift store at 22nd and Market Streets.

Six people died in the collapse and 13 were injured; one of the injured died 23 days later.

Abboud, 54, a principal in the New York structural engineering firm Weidlinger Associates, who specializes in investigating why buildings fail and collapse, appeared uncomfortable as he gave his opinion in response to questions from Robert J. Mongeluzzi, one of the plaintiffs lawyers.

Not without reason. Abboud was called as a witness on the ninth day of testimony put on by the legal team for New York real estate speculator Richard Basciano and his STB Investments.

Basciano and STB owned several buildings in the 2100 block of Market Street that were being razed for what Basciano hoped would be a major residential-commercial complex.

Now, Basciano and STB are defendants in a Philadelphia Common Pleas Court jury trial of consolidated lawsuits filed on behalf of collapse victims.

Abboud was the latest in a series of expert witnesses - architects, engineers, demolition experts, and more - whose testimony the jury will weigh in deciding which, if any, of the defendants should be held liable in the Center City collapse.

Questioned by Peter A. Greiner, a lawyer for Basciano and STB, Abboud countered earlier testimony by plaintiffs' experts that the Hoagie City demolition was so slipshod it was a public danger as early as May 15.

Abboud, however, said his own computer modeling of the building collapse showed that the building - and the unbraced wall - could have withstood sustained 40 mph winds until demolition started on June 5.

"It would not have collapsed barring some significant external force being applied," Abboud testified.

That force, contend lawyers for Basciano and the Salvation Army, was Sean Benschop, operator of the 36,000-pound excavator working on the building.

Basciano's lawyers have argued that he is being blamed for the acts of incompetent demolition workers recommended to him by Center City architect Plato A. Marinakos Jr., who was hired by STB to monitor demolition.

Questioned by Greiner, Abboud said his expertise as a structural engineer did not permit him to opine about the soundness of the demolition method.

And Abboud did not specifically blame Benschop. He said only that demolition work that morning caused the remaining internal structure to collapse and the force pushed over the wall.

Mongeluzzi, however, posed a hypothetical question: What would Abboud, as a licensed professional structural engineer, have done had he been on the scene before demolition began on June 5, 2013?

Abboud tried to avoid answering until finally, over Greiner's objects, Judge M. Teresa Sarmina told him to answer.

"My recommendation would be to evacuate the site and call L&I [the city Department of Licenses & Inspections]," Abboud replied, calling it a "life-safety issue."

Abboud returns to the witness stand when the trial resumes Thursday.

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