‘Not to code:’ Cracked beams at Transbay Terminal preventable, official says

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SAN FRANCISCO — The two beams that cracked at the Salesforce
Transit Center were not built to code, and the cracks could have
been prevented, the head of the agency that operates the center
said Thursday.

In the first time the agency has assigned blame for the
center’s problems, Mark Zabaneh, executive director of the
Transbay Joint Powers Authority, said companies contracted to
construct the center failed to meet building code requirements.

“It’s a failure of quality control in the construction
process,” Zabaneh said. “That’s why we are reviewing the rest
of the building to make sure we don’t have any other
incidents.”

The gleaming, $2.2 billion bus depot and eventual train station
closed in September, just six weeks after opening, when workers
installing ceiling panels happened to notice a large crack in a
structural steel beam. A subsequent inspection revealed the second
crack, both of which are in a section of the building that spans
Fremont Street. Bus riders have been using the temporary terminal
at Howard and Main streets since the discovery  of the cracks.

Although repairs are already underway and expected to be
completed by June, a date for reopening the center won’t be set
until an independent peer review panel can determine whether there
are similar construction problems in other areas of the building,
said Christine Falvey, a spokeswoman for the Transbay Joint Powers
Authority, the public agency in charge of building and maintaining
the building.

There were two main factors that led to the beams failing: the
quality of the steel used, and cracks that formed in the steel
while the beams were being built, said Robert Vecchio, the
president of New York-based LPI, Inc., which performed a series of
tests on samples from the steel to figure out why it cracked.

The American-made steel, which is four inches thick, was tough
on the outside but soft in the center, he said, making it more
susceptible to cracking.

The same steel was used in a different set of beams above First
Street, but those beams didn’t crack even though they have the
same design and bear the same amount of weight as beams above
Fremont Street, he said. What differed between the two was the way
the beams were built.

The First Street beams were constructed first, said Ron
Alameida, director of project management for the authority, but
quality control Inspectors refused to accept them,  because they
lacked
weld access holes
— a critical element used in welding to
ensure the welds can be completed without any defects. So crews
then cut the holes with torches after the beam was welded together,
he said. The second time around, on Fremont Street, crews instead
cut the access holes in first and then welded the beam together,
Alameida said.

“Ironically the sequence on First Street was to address an
issue of noncompliance,” he said. “The corrected work on
Fremont Street is actually what saved (the beams on) First
Street.”

That’s because on Fremont Street, when workers used a torch to
cut the hole in the beam, tiny cracks formed. They should have
first ground out the holes to make them smooth, eliminating any
cracks. That was not done,  Zabaneh said.

“It’s a concern from our part that (the grinding) was not
done,” he said. “The code requires welding access holes to be
ground, and these were not ground.”

That is important, Zabaneth said, because those micro cracks can
grow larger, especially when more heat is applied to the steel.

That is exactly what happened in this case, Vecchio said. After
the access holes were finished, the beams were welded together.
Welding takes place at very high temperatures, and that added heat
caused the tiny cracks that were already present in the steel to
grow larger in size, he said.

It’s unclear though, why
multiple layers of oversight
didn’t identify the lack of
grinding as an issue, Zabaneh said. Herrick Corporation, a
well-respected steel fabrication company based in Stockton, did the
welding work and had their own quality control measures in place,
he said. Then, Skanska USA, which was in charge of steel
procurement, and Webcor-Obayashi, the general contractor, all
performed their own quality control inspections.

The authority also hired Inspection Services, Inc. to do a final
inspection of the work. None of those layers of inspection
identified the lack of grinding as an issue, even though it is
visible to the eye and required in the code, Zabaneh said.

He added, however, that the project team and outside experts see
this as an isolated incident.

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Other experts noted that lack of grinding and the way the beams
were built were not the only factors that produced cracks in the
beams. The center’s one-of-a-kind design, coupled withe the
materials used, also played a role, said Michael Engelhardt, a
professor of structural engineering at the University of Texas and
the chairman of the independent peer review panel.

“Certainly, the access holes played a role and the order in
which they were placed played a role,” he said. “But it’s
difficult to point at one item without looking at the whole package
of items because they all happened together.”

Source: FS – All – Real Estate News 1
‘Not to code:’ Cracked beams at Transbay Terminal preventable, official says