CitiCorp Center Building Structural Analysis
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Transcript of CitiCorp Center Building Structural Analysis
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Jonathan Hopkins & Shawn Johnson
IDEA 3: Structural Precedent Analysis
RWU SAAHP
Arch 435 Fall 2011
Prof. Mete Turan
TA Katie Kanakos
A Case Study of
CitiGroup Center
New York, New York
The Open Ground Plane
In An Urbanizing World
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CitiGroup Center
601 Lexington Ave, MidTown, New York City
Architect: Hugh Stubbins Jr.
Engineer: William J. Messurier
Design Feature: Steel Frame Skyscraper without
Columns at Corners
IDEA 3 Precedent Analysis
-Theoretical Framework-
-Precedent Information-
-Structural Analysis-
-Design Solution-
-Conclusions-
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Theoretical Framework
- The number of cities with population above one million has already risen from six to 19 in the
past 40 years, and will continue to rise1
- By 2030 [the number of people living in towns and cities] will swell to almost 5 billion2
___________________________________________________________________________________________________________1Yeang, Ken. The Tall Building Typology and Cities Reinventing the Skyscraper (Academy Press, 2002) pgs. 33-552UNFPA. Urbanization: A Majority in Cities Linking Population, Poverty and Development (UNDESA, 2005)
Urbanized Population (2006)
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Theoretical Framework
- The presence of trees and grass has also been associated with reduced crime rates, possibly
because residents of a well landscaped building spend more time outside, allowing them to get
to know one another and develop a sense of community.3
- Humans living in landscapes that lack trees or other natural features undergo patterns of
social, psychological and physical breakdown4
___________________________________________________________________________________________________________3Davis, Dave. Developing a Sense of Community Designs and Codes that Reduce Crime around Mulitfamily
Housing (Local Government Commission) p. 3
4Staff. Science Suggests Access To Nature Is Essential To Human Health Science Daily (February 17, 2009)
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CitiGroup Center, New York
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Precedent Information5
- CitiGroup Office Building Conceptualized in early 1970s
- The site, across from CitiGroup HeadQuarters at 54th Street and Lexington Avenue, was
occupied by St. Peters Church
- A deal was struck to build the office tower while retaining the churchs location
- This circumstance prevented conventional structuring of the office tower with corner columns
- Stubbins and LeMessurier Proposed a 59-story building supported by enormous chevrons, each
carrying and distributing the load of 6-8 stories to a central reinforced concrete column
- The building is lifted off the ground 9-story by centrally located columns
_______________________________________________________________________________________________________________________________________________________________________________________________________________________
5Morgenstern, Joe. The Fifty-Nine Story Crisis The New Yorker (May 29, 1995)
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Assemblies & Construction
- Designed with Welded Joints
- Structured for the 55-year Wind Storm
- Calculations done with Perpendicular Wind
Loads
- Construction began in 1974
- The building was constructed outward from
the core in 6-8 story sections
- The structure is a steel frame
- Floor Plates are structured with reinforced
concrete
- Corners cantilever 70 feet beyond columns
- Aluminum and glass exterior cladding
- 7th Tallest building in New York City at 915
feet with 59 floors
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Crisis of 1978
- Construction Completed in 1977
- Contractors switched out welded joints with
bolted joints
- The Building deals with 45 degree angle wind
loads
- The Hurricane of 78 was a 100-year wind
storm
- Recalculations of loads revealed severe
structural deficiencies
- 2-inch steel plates were welded to each joint
on the building to counteract the shearing
forces on the bolted connections
- There were serious uncertainties about the
structural integrity of the building during the
storm
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Structural AnalysisGravity Load Analysis
- 1000 Kip vertical loads acting downward
on each 6-8 story section
- In the frames the [gravity] load is
transferred from the minor columns to the
mast column by diagonals at eight-story
intervals6
- The chevrons concentrate the loads to the
center, thus freeing up the corners, which
cantilever beyond the central columns 72
feet
_________________________________________________6Smith, Bryan Stafford and Alex Coull. Use of
Large Scale Bracing Tall Building Structures:
Analysis and Design (John Wiley & Sons, Inc. 1991)
p. 127 Compression Tension Moment
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Structural AnalysisWind Load Analysis
- Wind Shear is collected by the core over
eight-story-height regions and transferred to
the braced outer frames at the base of each
tier
- At the base of the tower the entire shear is
transferred back to the core and hence to the
ground
- Wind moment is carried mainly by the mast
columns and legs in the faces normal to the
wind, and partly by the core7
__________________________________________________________________________________________________________
7Ibid.Deflection
dx = 6.591 in
20 kip Horizontal Load
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Structural AnalysisCombined Load Analysis
- Since the diagonals carry a significant part
of the gravity loading, the structure may be
classified as either a space truss or a braced
frame8
- CitiGroup Building is a relatively light-weight
frame that is effected by lateral wind loads,
which is compensated for with a mass damper
(the first skyscraper to use one)
- The Brace frame is obstructive to facade
elements like windows
____________________________________________________________________________________________________________
8Ibid. MultiFrame Model
Shear
Moment
Axial
Tuned Mass Damper
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Alternative proposalSuspended, Reinforced Core Structure
Characteristics:
- Large, Reinforced Central Core
- Horizontal Cantilevers at Roof Level
- Floor Slabs Suspended from Hangers
- Open Concourse Level
- The Hangers, because they are in tension
and consequently can be of high strength
steel, have a minimum sized section...9
Advantages:
- More Open Ground Plane
- Shorter Cantilever
- Freed Facade
- Reduced Deflection 5.635 vs 6.591
__________________________________________________________________________________________________________
9Smith, Bryan Stafford and Alex Coull. Structural
Form Tall Building Structures: Analysis and Design
(John Wiley & Sons, Inc. 1991) p. 5010 Ibid.11 Schodek, Daniel L. and Martin Bechthold. Structural
Systems: Design for Lateral Loadings Structures
(Pearson Education, Inc. 2008) p. 546Model Moment
Suspended Frame10
Suspended Frame11
Shear Diagram
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Conclusions
CitiGroup Building, New York
- Inventive Solution to Existing Condition on a
Site
- Innovative Implementation of New Technology
- Inadequate Lateral Load Calculations that did
not account for 45 degree angle winds
- Poor Construction Administration Oversight
- Poorly Secured Joints
- Braced Frame Restricts the Facade
Alternative Suspended Frame Solution
- Frees up the Facade
- Opens up the Ground Plane
- Reduced Deflection
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Works Cited
Davis, Dave. Designs and Codes that Reduce Crime around Mulitfamily Housing (Local Government Commission)
Morgenstern, Joe. The New Yorker (May 29, 1995)
Schodek, Daniel L. and Martin Bechthold. Structures (Pearson Education, Inc. 2008)
Science Daily (February 17, 2009)
Smith, Bryan Stafford and Alex Coull. Tall Building Structures: Analysis and Design (John Wiley & Sons, Inc.
1991)
UNFPA. Linking Population, Poverty and Development (UNDESA, 2005)
Yeang, Ken. Reinventing the Skyscraper (Academy Press, 2002)