September 11, 2001, Chicago Tribune, Engineers shocked by towers’ collapse, by Blair Kamin, Tribune architecture critic, Published 12:18 PM CDT,
The World Trade Center, a symbol of American economic might, survived one terrorist attack in 1993. It was designed to withstand the impact of a jet, but both its towers collapsed this morning after planes rammed them.
The structural engineer who designed the towers said as recently as last week that their steel columns could remain standing if they were hit by a 707.
Les Robertson, the Trade Center’s structural engineer, spoke last week at a conference on tall buildings in Frankfurt, Germany. He was asked during a question-and-answer session what he had done to protect the twin towers from terrorist attacks, according to Joseph Burns, a principal at the Chicago firm of Thornton-Thomasetti Engineers.
Burns, who was present, said that Robertson said of the center, “I designed it for a 707 to smash into it.”
Burns, whose firm did the structural engineering for the Petronas Twin Towers in Malaysia -- the world’s tallest buildings -- said Robertson did not elaborate on the remark. Robertson could not be reached early today.
Completed in 1972 and 1973, the 110-story twin towers were the fifth and sixth tallest buildings in the world. One World Trade Center, finished in 1972, was briefly after its construction the world’s tallest building. The towers have been called “a monumental gate to New York and the United States.”
They withstood the 1993 attack, when a bomb-laden van exploded, killing six people and injuring more than 1,000.
Closely spaced steel columns that ringed their perimeter held up the World Trade Center towers. Chicago’s Aon Center (formerly the Amoco Building), completed in 1973, uses a similar support system, known to structural engineers as a “tube.”
Shocked by the building’s collapse, structural engineers pointed to fire as the likely cause of the structural failure.
“Fire melts steel,” Burns said. In addition, he said, the impact of the plane could have severely damaged the building’s sprinklers, allowing the fire to rage, despite fireproofing supposed to protect steel columns and beams.
“You never know in an explosion like that whether they (the sprinklers) get cut off,” Burns said.
Architects Minoru Yamasaki and Associates, in association with Emery Roth & Sons, designed the World Trade Center.
The structural engineers were the firm of Skilling, Helle, Chrstiansen, Robertson. The developer was The Port Authority of New York and New Jersey.
Today’s attack marked the second time that a plane has crashed into a New York City skyscraper, although the first incident was an accident.
In 1945, a B-25 flying at 200 miles per hour slammed into the 78th and 79th floors of the Empire State Building, gouging an 18-by-20-foot hole 913 feet above the streets of Manhattan. The pilot, Lt. Col. William F. Smith Jr., had been heading from New York’s LaGuardia Airport to Newark, N.J., when he became disoriented.
Fourteen people died in the crash and the fire that followed -- three people in the plane and 11 in what was then the world’s tallest building.
Like the World Trade Center, the Pentagon, which also was struck by a plane, provided a sizable and symbolic target.
The Pentagon is the world’s largest office building, with a total of 6.5 million square feet, serves as headquarters for the world’s most powerful military. Sears Tower, by comparison, has about 3.5 million square feet of office space.
September 11, 2001, Detroit Free Press, Yamasaki firm, designers of World Trade Center, somber as landmark falls, BY EMILIA ASKARI AND MATT HELMS, FREE PRESS STAFF WRITERS,
The mood was frantic and somber today at the Rochester Hills architectural firm that designed the World Trade Center buildings that collapsed in what appears to be a terrorist attack.
The towers that reshaped New York's skyline were designed by Minoru Yamasaki, a Troy-based architect who died in 1986. He was known for a passion for softening and humanizing the glass-house style of international architecture.
Officials at Minoru Yamasaki Associates said they were working with the FBI after the attack. A spokeswoman from the firm said a statement would be released within hours.
Employees were engaged in a discussion about terrorism and the World Trade Center, surrounded by drawings of the famous building. The 110-story building, which covers five acres, was completed in 1976 and cost $350 million.
Yamasaki's works in southeast Michigan include Wayne State University's McGregor Memorial Conference Center, the Reynolds Aluminum building in Southfield, Temple Beth El in Birmingham and the 30-story Michigan Consolidated Gas Co. building at Woodward and Jefferson in downtown Detroit.
The Seattle native moved to Detroit from New York in 1945 to become chief designer for the architectural firm Smith, Hinchman and Grylls Associates Inc. A few years later he established Minoru Yamasaki Associates, which made a name for itself designing buildings worldwide.
For more on the Yamasaki firm, email@example.com.
September 12, 2001, Los Angeles Daily News / Associated Press, A miracle of steel can't withstand powerful attack, by Sharon L. Crenson, Associated Press,
NEW YORK -- The image of the World Trade Center's 110-story twin towers crumbling seemed a scene of impossible destruction.
But the miraculous steel and concrete architecture that made them could not withstand the power of Tuesday's attack and ensuing fire. No building designed today could, said Masoud Sanayei, a civil engineering professor at Tufts University.
Experts in skyscraper construction said video of the collapse led them to believe the towers were perhaps weakened by the initial impact of the airplanes that hit them Tuesday, but that heat from the resulting fire was likely the most punishing blow.
Hyman Brown, a University of Colorado civil engineering professor and the Trade Center's construction manager, speculated that flames fueled by thousands of gallons of aviation fuel melted steel supports.
"This building would have stood had a plane or a force caused by a plane smashed into it," he said. "But steel melts, and 24,000 gallons of aviation fluid melted the steel. Nothing is designed or will be designed to withstand that fire."
Sanayei said the heat may have disconnected one of the towers' concrete floors from the tubular steel columns that ringed the buildings. If one or two floors collapsed, it would have created a pancake effect of one massive floor caving into the next.
"In my opinion, the fire weakened the connection between the floor system and the columns on the higher floors and caused a couple of the floors to collapse," Sanayei said. "The floors are very heavy, made of reinforced concrete, so when one hits the next, they cause a domino effect ... and it can go all the way down to the first floor."
Architect Minoru Yamasaki, who died in 1986, worked with engineers John Skilling and Leslie E. Robertson to design the fabled twin towers, once the world's tallest buildings.
In his 2000 book "Building Big," architect David MaCaulay described the towers' engineering as "a series of load-bearing exterior columns spaced 3 feet apart and tied together at every floor by a deep horizontal beam, creating a strong lattice of square tubing around each tower."
The core surrounding the elevators inside was much the same, with a giant lattice work of steel covered by poured concrete connecting the interior columns to the exterior ones. The design was free enough for each of the towers to hold 4 million square feet of space unencumbered by columns or load-bearing walls.
Sections of exterior wall were wrapped around the outside in 24- and 36-foot-high sections, creating a sort of patchwork so that not all the floor joints would meet walls at the same height, according to MaCaulay.
Both Brown and Saw-teen See, a managing partner in Robertson's engineering firm, said the twin towers were originally designed to sustain a direct hit by a large jetliner, but that such construction couldn't make them fire- or bombproof.
Brown said it appeared the attack was meticulously planned.
"If they did it lower in the building, the fire department could have gotten to it sooner. In its simplicity, it was brilliant."
He said that the two towers have staircases in all four corners of the buildings and were designed to be evacuated in an hour, but it appeared that since the planes crashed into the corners, escape was cut off for those on the floors above.
"I could never conceive of anybody being able to bring down those two buildings," Brown added.
Minoru Yamasaki Associates issued a statement Tuesday saying the firm was in contact with authorities and had offered assistance.
"We believe that any speculation regarding the specifics of these tragic events would be irresponsible," the statement said. "For obvious reasons, MYA has no further comment at this time."