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| The
Hearst Tower included many unique challenges
for both fabrication and erection of the
structural steel frame. The “nodes” connecting
the diagrid columns pictured to the immediate
left were made of 10” plate, milled on all
sides to exacting tolerances. |
| An
example of the plate preheating necessary
to insure welding quality is shown in the
photographs included here. Connections to
the diagrid columns and moment connections
to the floor beams were fabricated to tighter
tolerances than required by the AISC Code
of Standard Practice, allowing the diamond-shaped
framework to properly support the curtain
wall system. |
| Plumbness
and elevation of the diagrid framing was
checked every four floors in the field,
confirming that Cives Steel Company and
Cornell Erectors achieved ± 0” to ½” from
theoretical location in all directions.
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| The
challenges of the erector framing the nodes
and diagrid columns are readily apparent
in these photographs. |
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| The
diagrid framing started at the 10th floor. It was
supported by 42” square “mega columns” and “mega
braces,” which provided the majestic open structure
from the 3rd to the 10th floors. Installation required
two cranes, lifting 100’ long pieces weighing as
much as 70 tons. The intersection of the mega braces
and mega columns at the 3rd floor required fabrication
of “Y” nodes. These nodes were critical to the structure,
delivering most of the tower loads to the framing
below. Fabricated with 2” and 3” plates, the Y nodes
were complex, highly-welded assemblies requiring
skilled workmen in the shop to complete. Pictures
of the erection of the mega columns, braces, and
Y nodes are provided here. |
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| Hearst
Connection Design |
| In
the process of converting this
innovative structure from lines
on the page to steel in the
air, Cives Engineering Corporation
faced many challenges. |
| A
safe transfer of the required
loads had to be provided for
the diagrid system. This involved
the analysis of over 15,000
pages of design loads provided
to Cives by the Engineer of
Record. Tension, compression,
shear, and moments, all had
to be accommodated in connections
that would allow for a safe
and quick erection. Despite
the vast number of loading conditions,
a single “standard” connection
configuration was provided at
all nodes. |
| The
77 year old façade also presented
many unusual problems. Not only
was the newly-erected steel
required to interface with existing
steel, but it was also, in many
instances, required to do so
while resisting blast loads
that could result from possible
terrorist attacks. The most
obvious choice would have been
to field-weld all of the connections
subjected to blast loads. However,
this would have represented
an unacceptable increased cost
to the project, so Cives employed
heavy, one-sided connections
to resist the inordinately high
loads. |
| The
7th floor skylights represented
a different challenge. Instead
of battling extremely high loads,
the concern was maintaining
a clean and aesthetically-pleasing
look to the tubular construction.
Once again, Cives developed
an inventive “concealed-bolt
arrangement” that was more cost
effective and architecturally
desirable than the originally-proposed
connection. |
| These
examples represent only a small
sampling of the connections
required to turn the Hearst
Tower dream into reality. Over
500 typical designs were produced
as templates for the remaining
connections. As with all Cives
projects, the requirements of
the architect and engineer were
coalesced with the strength
of the fabricator and erector
to produce a structure that
was both safe and economical. |
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| Northern
Division |
| 8
Church Street |
| Gouverneur,
New York 13642 |
(315)
287-2200 |
(315)
287-4569 (Fax) |
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