BAE – STRUCTURAL OPTION
conclusion
breadth
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overview
introduction
DAVID GEIGER
DULLES TOWN CENTER BUILDING ONE
DULLES, VIRGINIA
SENIOR THESIS PRESENTATION
14 APRIL 2009
 Proposal Summary
DULLES, VIRGINIA
SENIOR THESIS 2009
 Building Overview
DULLES TOWN CENTER BUILDING ONE
 Goals
 Depth Study
• Structural System Redesign
 Breadth Study
• Cost Comparison
• Schedule Comparison
• 7th Floor Acoustics
 Conclusions
DAVID GEIGER – STRUCURAL OPTION
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overview
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INTRODUCTION
DULLES TOWN CENTER BUILDING ONE
• (7) Stories of office space above grade
• (1) Sub-grade floor
Houses building services and amenities
SENIOR THESIS 2009
 7 Story Commercial/Office Building
DULLES, VIRGINIA
 Square Footage: 202,110 gross floor area
 Site Area: 12.37 acres
 Project Duration
• Fall 2000 – Spring 2002
 Project Delivery Method
• Design-Bid-Build
DAVID GEIGER – STRUCURAL OPTION
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OVERVIEW
21000 Atlantic Boulevard
Dulles, Virginia 20101
 25 miles northwest of Washington, D.C.
 5 minutes from Dulles International Airport
introduction
DULLES, VIRGINIA
SENIOR THESIS 2009
Location:
DULLES TOWN CENTER BUILDING ONE
DAVID GEIGER – STRUCURAL OPTION
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OVERVIEW
SENIOR THESIS 2009
 Architect:
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 Structural Engineer:
 Civil Engineer:
 General Contractor:
KCF-SHG Inc.
DAVID GEIGER – STRUCURAL OPTION
introduction
overview
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DULLES, VIRGINIA
 Owner:
 MEP Engineer:
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DULLES TOWN CENTER BUILDING ONE
Project Team
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OVERVIEW
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7” one-way slab on post-tensioned beam system
F’c = 5000 psi
½” DIA. 7 wire, low-relaxation strand
48”x 17” post-tensioned beams
3-day curing time before post-tensioning
40’ spans
DULLES, VIRGINIA
SENIOR THESIS 2009
Existing Floor System
DULLES TOWN CENTER BUILDING ONE
Existing Columns
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Cast-in-place
24”x 24”
f’c = 5000 psi (Floors C-2)
f’c = 4000 psi (Floors 4-PH)
DAVID GEIGER – STRUCURAL OPTION
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OVERVIEW
SENIOR THESIS 2009
• Frames in east-west direction
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• Frames in north-south direction
DAVID GEIGER – STRUCURAL OPTION
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DULLES, VIRGINIA
 Ordinary reinforced concrete moment frames in both directions
• Post-tensioned beams
• Reinforced columns
• Slab drops
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DULLES TOWN CENTER BUILDING ONE
Existing Lateral System
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OVERVIEW
5” slab on grade reinforced with 6x6 – W2.0xW2.0 WWF
Strap beams ranging from 24”x 36” to 48”x 48”
24” foundation wall
Pile caps
Cast-in-place caissons with diameters ranging from 30” to 75”
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DULLES, VIRGINIA
South Elevation
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DULLES TOWN CENTER BUILDING ONE
DAVID GEIGER – STRUCURAL OPTION
introduction
overview
Existing Foundation
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OVERVIEW
DULLES TOWN CENTER BUILDING ONE
 To conduct a comparison between the existing concrete system and
a steel redesign to determine which building material resulted in
more benefits, both in regards to time and money
SENIOR THESIS 2009
Proposal Summary
DULLES, VIRGINIA
• Gravity System
o Composite metal deck system
• Lateral System
o Ordinary steel moment frames
• Foundation System
o Resist overturning
o Reduce number of caissons, if possible
DAVID GEIGER – STRUCURAL OPTION
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PROPOSAL
DULLES TOWN CENTER BUILDING ONE
Design Goals
 Respect the current column layout to maintain large spans and
open floor plans
 Limit total floor depth to preserve floor-to-ceiling heights of 9’
and prevent additional façade costs
SENIOR THESIS 2009
DULLES, VIRGINIA
 Establish a design that quickens construction and decreases total
project costs
 Preserve a suitable working environment within the 7th floor
office space
 Become more familiar with steel design and construction
DAVID GEIGER – STRUCURAL OPTION
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GOALS
 Composite metal deck
 Benefits
• Speed of steel construction
• No shoring
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DULLES, VIRGINIA
 Design governed by fire rating
 Drawbacks
• Maximum clear span of 17’
• Infill beam needed
• Larger slab depth
DAVID GEIGER – STRUCURAL OPTION
introduction
 Vulcraft Product Catalog
depth
proposal
 Chapter 4, ASCE 7-05
DULLES TOWN CENTER BUILDING ONE
SENIOR THESIS 2009
Floor System
goals
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DEPTH
 Infill beams
 Benefits
• Can span 40’
• Lighter than concrete
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DULLES, VIRGINIA
 Design governed by ΔLL
 Drawbacks
• Larger beam depth
• Needs fireproofing
 In order to keep floor-to-ceiling
heights at 9’, need to camber
DAVID GEIGER – STRUCURAL OPTION
introduction
 13th Ed. AISC Steel Manual
depth
proposal
 Chapter 4, ASCE 7-05
DULLES TOWN CENTER BUILDING ONE
SENIOR THESIS 2009
Floor System
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DEPTH
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DULLES, VIRGINIA
 Reduces overall cost of infill beams
compared to no camber
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DULLES TOWN CENTER BUILDING ONE
Typical floor layout of cambered beams
DAVID GEIGER – STRUCURAL OPTION
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Camber
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DEPTH
DULLES TOWN CENTER BUILDING ONE
 Ordinary steel moment frames in both the east-west
and north-south directions
 Beam to column connections are fixed by providing
flange welds
 Benefits
• Lighter framing
• Better in tension
• Can span the necessary 40’
 Drawbacks
• Beam depth
• Expensive connections
SENIOR THESIS 2009
Lateral System
DULLES, VIRGINIA
DAVID GEIGER – STRUCURAL OPTION
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DEPTH
 Wind
• ASCE 7-05, Chapter 6
o Method 2
o Serviceability controlled strength
in east-west direction
DULLES, VIRGINIA
SENIOR THESIS 2009
Lateral System Design Loads
DULLES TOWN CENTER BUILDING ONE
DAVID GEIGER – STRUCURAL OPTION
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DEPTH
 Seismic
• ASCE 7-05, Chapter 12
o Equivalent Lateral Force Procedure
o Controls strength in north-south direction
DULLES, VIRGINIA
SENIOR THESIS 2009
Lateral System Design Loads
DULLES TOWN CENTER BUILDING ONE
DAVID GEIGER – STRUCURAL OPTION
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DEPTH
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Lateral System Layout
 North-South
introduction
SENIOR THESIS 2009
 East-West
DAVID GEIGER – STRUCURAL OPTION
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DEPTH
DULLES TOWN CENTER BUILDING ONE
DULLES, VIRGINIA
DULLES TOWN CENTER BUILDING ONE
Lateral System Design Loads
 Inherent Torsion
• Mt = V(e)
 Accidental
• Mt,a = V (e + .05L)
SENIOR THESIS 2009
DULLES, VIRGINIA
 Minimal effects due to symmetry
• Maximum shear caused by torsion less than 1 kip per frame
DAVID GEIGER – STRUCURAL OPTION
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DEPTH
DULLES TOWN CENTER BUILDING ONE
 Preliminary hand calculations
• Design loads from ASCE 7-05 procedures
• Portal Frame Analysis for Moments
o Exterior, façade-supporting beam
• deflection of L/500 controlled
• used conjugate beam method
o Column, interior
• Table 6-1, AISC Steel Manual
• Interaction equation
• Iteration until OK
SENIOR THESIS 2009
Lateral System Member Design
DULLES, VIRGINIA
DAVID GEIGER – STRUCURAL OPTION
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DEPTH
DULLES TOWN CENTER BUILDING ONE
 RAM Analysis
• Design loads from ASCE 7-05
o Beams
• drift controlled design
• repetition of members
o Column
• used Eq. H1-1a, interaction equation
• drift controlled design
• repetition of members
SENIOR THESIS 2009
Lateral System Member Design
DULLES, VIRGINIA
DAVID GEIGER – STRUCURAL OPTION
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DEPTH
DULLES TOWN CENTER BUILDING ONE
Serviceability
 Wind
• h/400
• h/500 for members supporting precast or curtain wall façade
SENIOR THESIS 2009
DULLES, VIRGINIA
 Seismic
• .020hsx
• amplification factor
o δx = (Cd x δxe)/I
 Drifts taken from RAM using ASCE 7-05 lateral loads
 Serviceability controls design in the east-west direction only
DAVID GEIGER – STRUCURAL OPTION
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DEPTH
Floor Depth
DULLES, VIRGINIA
 Due to serviceability standards, beams as large as W18x130’s
were needed for typical floor framing
SENIOR THESIS 2009
introduction
DULLES TOWN CENTER BUILDING ONE
 Preserving ceiling-to-floor height of 9’ not achieved,
must use 8’-8”
DAVID GEIGER – STRUCURAL OPTION
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DEPTH
 Overturning moment calculated in both directions
introduction
DULLES, VIRGINIA
SENIOR THESIS 2009
Foundation
DULLES TOWN CENTER BUILDING ONE
 North-south direction good
by inspection
 East-west direction checked
for overturning
• .9D + 1.6W
 Mresisting > Moverturning
DAVID GEIGER – STRUCURAL OPTION
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DEPTH
 Intermediate caissons removed
 84 C.Y. of concrete saved
 Loads on caissons checked using cantilever method
and compared to existing loads on plans
• Live load reduction
• 1.2D + 1.6W + L + .5Lr
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1
2
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Foundation
DAVID GEIGER – STRUCURAL OPTION
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DULLES, VIRGINIA
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DULLES TOWN CENTER BUILDING ONE
DEPTH
 Existing Concrete System
• R.S. Means
• Multiple crews used for forming and post-tensioning
• Construction zones: 5
• Column construction per floor: 30 days
• Slab and beam construction per floor: 10 days
• Post-tensioning per floor: 25 days
• Total construction time: 258 days
DULLES, VIRGINIA
SENIOR THESIS 2009
Schedule Analysis
DULLES TOWN CENTER BUILDING ONE
DAVID GEIGER – STRUCURAL OPTION
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BREADTH
 Steel Redesign
• R.S. Means
• Single crews used
• Construction zones: 3
• Framing construction per floor: 15 days
• Deck and detailing: 45 days
• SOD preparation and placement: 18 days
• Total construction time: 96 days
DULLES, VIRGINIA
SENIOR THESIS 2009
Schedule Analysis
DULLES TOWN CENTER BUILDING ONE
DAVID GEIGER – STRUCURAL OPTION
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overview
proposal
goals
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BREADTH
Cost Analysis
 Existing System
• R.S. Means
DULLES, VIRGINIA
SENIOR THESIS 2009
introduction
DULLES TOWN CENTER BUILDING ONE
conclusion
 Overall estimated savings of approximately $1.8 million
 Moment connection costs not included
DAVID GEIGER – STRUCURAL OPTION
 Steel Redesign
• R.S. Means
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BREADTH
DULLES, VIRGINIA
SENIOR THESIS 2009
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DULLES TOWN CENTER BUILDING ONE
Breadth Comparison
 Cost and Schedule comparison
conclusion
breadth
*
* Moment connection costs not included
DAVID GEIGER – STRUCURAL OPTION
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BREADTH
DULLES, VIRGINIA
Acoustic Study
 Checked for sound infiltration in the 7th floor office space due to the
reduction in depth of the floor slab
SENIOR THESIS 2009
introduction
DULLES TOWN CENTER BUILDING ONE
Existing PH Floor
Existing Roof
DAVID GEIGER – STRUCURAL OPTION
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BREADTH
DULLES, VIRGINIA
SENIOR THESIS 2009
introduction
DULLES TOWN CENTER BUILDING ONE
Acoustics Study
Redesigned Roof
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 Result: No sound penetration found in either case
DAVID GEIGER – STRUCURAL OPTION
Redesigned PH Floor
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BREADTH
Were goals met?
 Respect the current column layout to maintain large spans and
open floor plans
 Limit total floor depth to prevent additional façade costs and
preserve floor-to-ceiling heights of 9’
 Establish a design that quickens construction and decreases total
project costs
conclusion
breadth
depth
proposal
YES
SENIOR THESIS 2009
DULLES, VIRGINIA
YES/NO
YES
 Preserve a suitable working environment within the 7th floor
office space
YES
 To become more familiar with steel design
YES
DAVID GEIGER – STRUCURAL OPTION
introduction
DULLES TOWN CENTER BUILDING ONE
goals
overview
CONCLUSION
 Schedule Analysis
• reduced schedule by an estimated 162 days
• benefits owner with sooner building opening
 Cost Analysis
• Material costs went up, but overall costs went down
• Estimated an approximate savings of $1.8 million
conclusion
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proposal
 Gravity/Lateral system redesign
• Applicable to DTC One
• Minimal change to architecture
 Acoustic Analysis
• No new sound penetration caused by the thinner slab
 Redesign of DTC One in steel is feasible
SENIOR THESIS 2009
Recommendation
DULLES, VIRGINIA
DAVID GEIGER – STRUCURAL OPTION
introduction
DULLES TOWN CENTER BUILDING ONE
goals
overview
CONCLUSION
depth
Industry Professionals:
Michael Sladki – Cates Engineering, Ltd.
Walter Rabe – Schanbel Engineering, LLC
Colleagues:
Dr. Linda Hanagan – Penn State University
Benjamin Follett – The Bat Cave
Jeremy McGrath – The Bat Cave
And a special thanks to my family and friends for all of their love and support.
SENIOR THESIS 2009
Owner Representatives:
Frank Gambino – Lerner Enterprises, Inc.
Kelly Burnette – Lerner Enterprises, Inc.
DAVID GEIGER – STRUCURAL OPTION
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DULLES, VIRGINIA
I would like to thank the following people for assisting me in this thesis research
process:
Advisor:
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DULLES TOWN CENTER BUILDING ONE
Acknowledgements
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CONCLUSION
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introduction
SENIOR THESIS 2009
Questions?
DAVID GEIGER – STRUCURAL OPTION
conclusion
CONCLUSION
DULLES TOWN CENTER BUILDING ONE
DULLES, VIRGINIA