Enclosed by strip windows and precast-concrete spandrel panels, the stepped portions of the building also feature vegetated rooftop terraces at most levels of each wing.
were overcome by installing a battered
pile system, which meant that the considerable axial strength and stiffness of each
battered pile were used to full advantage.
While battering piles added to the cost of
the project, other, more economical lateral
load paths, for example, the use of passive
pressure against the pile caps, were determined to be insufficient or unreliable because of the dramatically varying subgrade
conditions at this site.
The design team made extensive use of
building information modeling software
systems for exchanging information on
this project. The designers provided conventional drawings for the contract documents and used the Revit software system—developed by Autodesk, Inc., of San
Rafael, California—to generate three-dimensional models for coordination only.
Designed and constructed over the period from 2008 to 2011, the MSC is a visually dramatic addition to the University
Park campus. Even more dramatic, however, are the relatively hidden features of this
new facility: the specially reinforced micropiles that addressed the extremely variable
subgrade conditions; the heavy floor framing that achieved floor vibration criteria ap-
propriate for a world-class research facility; and the extremely
rigorous vibration control measures that made it possible to
successfully locate the quiet labs beneath the gateway garden,
which is bridged by the signature cantilevered corner. Both
visible and hidden design features work together in the service
of cutting-edge research. CE
large-diameter reinforcing bars. A typical micropile system on
this project can develop a service-level load of 300 kips in compression. Here 7 in. diameter pipe with a heavy wall casing and
a yield strength of 80 ksi is used in combination with 75 ksi no.
18 central rebar and grout with a strength of 5 ksi.
© JEREMY BITTERMAN, COURTESY OF RAFAEL VIÑOLY ARCHITECTS
Unfortunately, micropiles in this type of application have
little skin friction until the bond zone is reached. This means
that a member with a small cross section under very high
compression forces will be highly strained over the unbonded
length, leading to significant axial shortening and contributing to foundation settlement. Micropiles also have very little resistance to transverse loads. Thus,
shortening from axial strain posed a
challenge because the micropiles that
were located just 3 ft apart as part of a
common three-pile cap arrangement
varied by as much as 128 ft in length.
This would have resulted in a 1. 1 in. differential shortening condition if no other
action had been taken. Thus, where necessary, the longer piles were stiffened by
such methods as telescoping a second
casing with a slightly smaller diameter
within the standard casing, by grouting the annulus and using no. 28 rebar
instead of no. 18, or by implementing
For lateral loads, the low transverse
strength and stiffness of the micropiles
Akbar Tamboli, P.E., F.ASCE, is a principal in the Newark, New
Jersey, office of Thornton Tomasetti, Inc.; Leonard M. Joseph, P.E.,
S.E., is a principal in the firm’s Los Angeles office; Kaushik Dutta is
an associate in the Mumbai, India, office; and Umakant Vadnere,
P.E., is a vice president in the Newark office.
PROJECT CREDITS Owner:
Pennsylvania State University Architect: Rafael Viñoly Architects, New York City
Structural engineer: Thornton Tomasetti, Inc., New York City Acoustics
and vibration: Papadimos Group, San
Francisco Mechanical systems: Flack +
Kurtz (now WSP Flack + Kurtz), New
York City Electromagnetic induction
consultant: Vita Tech Electromagnetics, Fredericksburg, Virginia Landscape
architect: Dewberry, Atlanta
Construction manager: Whiting-Turner
Contracting Company, Baltimore Steel
fabricator/erector: Kinsley Manufacturing, York, Pennsylvania
SEPTEMBER 2012 Civil Engineering