discovery communications headquarters silver springs, md josh woolcock structural option...

Discovery CommunicationsHeadquartersSilver Springs, MD

Josh WoolcockStructural

Option

Architectural EngineeringPennsylvania State University

Outline

- Building Information

- Existing Conditions

- Structural Analysis

- Cost Analysis

- Schedule Analysis

- Office Lighting Design

- Conclusions

Pennsylvania State UniversityArchitectural Engineering

Josh WoolcockStructural Option

Project Team

Owner Discovery Communications Inc.

Architect SmithGroup Inc.

Engineers Structural – KTLH Engineering Civil – VIKA Inc. MEP – Flack & Kurtz

General Contractor Clark Construction



Building Overview

- Multipurpose Office Facility- two independent towers, of 7 and 10-stories

- 3 levels of underground parking

- 550,000 sqft. of open office space

- $52 Million overall cost

Layout & Function



Existing ConditionsMechanical

-Individual air-handling units on each floor

-Duct work for tenant build-out

- 3 centrifugal water chillers and roof cooling towers

- 3 gas-fired furnaces



Existing ConditionsLighting / Electrical

- Three 4,000A three-phase feeders for three switchboards, totaling 12,000A

- Lighting in office space reserved for tenant build-out



Existing ConditionsStructural

- CIP Concrete Structural System

- Two structurally independent towers

- 2-way cambered 9” structural slab with drop panels

-30’ x 30’ column grid

-Column sizes up to 36” x 48”



Structural Analysis

PurposeTo reduce the size of the columns within the office spaces to reduce concrete volume, increase floor space and promote aesthetics.

Reasons for Initial Size- Act as both lateral and gravity system- Building sway constraints- Large dead Loads

Possible Solutions- Separation of Lateral and Gravity Systems- Reduction of Gravity Loads

FocusNorth Tower: 10 Office Floors & Penthouse



Structural AnalysisInitial Considerations

-Loads calculated from IBC2000-Deflection Requirements

-H/400 for service wind loads-H/50 for service seismic loads-Respect to other tower: Contact at 8th Floor

-Building Geometry-Much longer than it is wide

-Secondary Considerations-Building Floor Plan and Impact-Impact on other building systems



Structural AnalysisFloor Slab Reduction

-ADOSS was used: Equivalent Frame Method

-Floor slab construction switched from 4000psi to 5000psi concrete

-Slab thickness reduced from 9” to 8”

-Drop panels remain 7.5”

-Slab Reinforcement increased from an average of 4.46psf to 4.89psf

-Maximum D+L deflection is 0.759”

-Slab weight was reduced by 11% or 11.25kip per column per floor



Structural AnalysisShear Walls

-4 preliminary locations for shear walls

-Locations do no hinder original floor plan

-Tests were performed to determine their lateral performance

-Use of 4 walls resulted in excess torsion

-2 shear walls were implemented and located to reduce torsion in building



Structural AnalysisShear Wall Design

-Walls Start at floor 1 and continue to main roof

-Walls span column-to-column

-Design changes at floors 1,3,5 & 7

-Maximum loads – Wind w/ Torsion & Factored

- 765.3 kip Shear

- 57269.81ft-kip Bending

-1909 kip Axial



Structural AnalysisShear Wall Design

-24” x 36” columns at ends

- Concrete strength

- 10000psi at Floor 1

- 8000psi at Floor 3

- 4000psi at floor 5

-Wall Reinforcement

- #5@18” Horz.

- #5@18” Vert.



Structural AnalysisShear Transfer

-Shear Walls stop at first floor

-Columns continue down to foundation

-No Bending in Slab

- Shear transferred from walls to floor slab then to retaining walls

- Lateral earth pressure resists shear and locks floor 1 in place



Structural AnalysisColumn Reduction

-All Columns within office spaces are 24” x 24”

-4 different column designs

-Concrete Strengths

- 8000psi Floor 1

- 6000psi Floor 3

- 4000psi Floor 5

- 4000psi Floor 7



Structural AnalysisFinal Lateral System

- North-South Direction

- Combination of Shear walls and Moment Frames

- Contribution via stiffness analysis

- 66.8% Shear walls at floor 10

- 90.1% Shear walls at floor 5

- 96.3% Shear walls at Floor 1

- East-West Direction

-Moment Frames



Structural AnalysisLateral System Performance

- North-South Direction



-East-West Direction

LATERAL DISPLACEMENTS - NS DIRECTION

F1 S1 S2 F14Roof 1.04 1.25 1.3 1.66

8 0.78 0.93 0.96 1.23Roof -0.54 1.14 1.47 3.6

8 -0.4 0.84 1.09 2.66Roof 1.4 1.39 1.38 1.37

8 1.04 1.03 1.02 1.01Roof -0.46 1.27 1.61 3.43

8 -0.34 0.94 1.19 2.54Seismic w/ Torsion

Load Condition LocationDiflection

Wind

Wind w/ Torsion

Sesimic

LATERAL DISPLACEMENTS - EW DIRECTION

F-A F-B F-C F-D F-ERoof 2.09 2.15 2.27 2.40 2.52

8 1.53 1.57 1.66 1.75 1.84Roof 1.56 1.76 2.07 2.70 3.18

8 1.14 1.28 1.51 1.97 2.32Roof 4.34 4.42 4.58 4.90 5.14

8 3.17 3.23 3.34 3.58 3.75Roof 3.55 3.84 4.33 5.33 6.08

8 2.59 2.80 3.16 3.89 4.44Seismic w/ Torsion

Load Condition LocationDiflection

Wind

Wind w/ Torsion

Sesimic

Notes:

Max Wind = 2.66”

Max Seismic = 2.54”

Notes:

Max Wind = 2.32”

Max Seismic = 4.44”

Structural AnalysisConclusions



-Reduction in floor slab produced a 11% decrease in slab dead load on columns

-Implementation of Shear Walls reduced bending stresses in columns due to lateral forces

-Column size was reduced to 24”x24” throughout the office spaces

- Placement of Shear Walls did not adversely affect building floor plan or mechanical and fire protection services

Cost AnalysisInitial Considerations

- Detailed Estimate performed on both original and new structural systems

- Costs Estimated using RSMeans 2001

- Bare Costs : Overhead and Profit not included



Purpose Determine cost implications of new structural systems

EXISTING SYSTEM

Work Item U/M Quantity Cost $ / Unit Total Cost $

Total Concrete cy 2765.44000 psi cy 2012.9 65 $130,838.506000 psi cy 752.5 78.85 $59,334.638000 psi cy 0 128.2 $0.00

Reinforcing ton 188.5 935.75 $176,388.88Concrete Placement cy 2765.4 20.83 $57,603.28Formwork sqft 112000 3.92 $439,040.00

Total $863,205.28

Cost AnalysisColumns

REDESIGNED SYSTEM


Total Concrete cy 1555.54000 psi cy 977.3 65 $63,524.506000 psi cy 254.1 78.85 $20,035.798000 psi cy 324.1 128.2 $41,549.62

Reinforcing ton 215.46 935.75 $201,616.70Concrete Placement cy 1555.5 23.08 $35,900.94Formwork sqft 84000 4.09 $343,560.00

Total $706,187.54

Notes:

- 43.8% Reduction in volume (1210cy)

- 25% Reduction in formwork (28000sqft)

- 14.3% increase in reinforcement

- Cost Savings of $157,017.74



EXISTING SYSTEM


Total Concrete cy 11340.34000 psi cy 11340.3 65 $737,119.505000 psi cy 0 69.35 $0.00

Reinforcing ton 927 897.75 $832,214.25Concrete Placement cy 11340.3 13.25 $150,258.98Formwork sqft 408250 3.74 $1,526,855.00

Total $3,246,447.73

Cost AnalysisFloor Slab

Notes:

- 1” reduction in slab thickness

- 11.1% Reduction in volume (1260cy)

- 7.2% increase in reinforcement

- Increased Cost of $5,493.33

REDESIGNED SYSTEM


Total Concrete cy 10080.24000 psi cy 0 65 $0.005000 psi cy 10080.3 69.35 $699,068.81

Reinforcing ton 994.1 897.75 $892,453.28Concrete Placement cy 10080.3 13.25 $133,563.98Formwork sqft 408250 3.74 $1,526,855.00

Total $3,251,941.06



Cost AnalysisShear Walls

REDESIGNED SYSTEM


Total Concrete cy 291.334000 psi cy 165.22 65 $10,739.308000 psi cy 54.44 78.85 $4,292.5910000 psi cy 71.67 179.89 $12,892.72

Reinforcing ton 12.6 831.25 $10,473.75Concrete Placement cy 333.33 13.92 $4,639.95Formwork sqft 14683.2 2.63 $38,616.82

Total $81,655.13

Notes:

-291.33cy of additional concrete

-14,683.2 sqft of formwork

-12.6 ton of additional reinforcement

-Approximately $81,700 in additional cost



Cost AnalysisConclusions

Notes:

-2178.67 cy reduction in concrete

-14,366 sqft reduction in formwork

-106.66 ton increase in reinforcement

-Cost savings of nearly $70,000.00



REDESIGNED SYSTEM

Systems Total Cost $

Floor Slabs $5,493.33Shear Walls $81,655.13Columns -$157,017.74

Cost Difference -$69,869.28

Schedule AnalysisInitial Considerations



- Possible construction sequence for the original and new system

- Based on a 2 week floor to floor construction time

- Production number calculated from 2001 edition of RSMeans

- Slab pours would be made every 2 days to facilitate construction of both towers simultaneously

Purpose Analyze construction time and sequencing of new structural

system via floor to floor erection time

Schedule AnalysisProduction



- Production capacity-1 crew can erect 3 columns / day-1 crew can erect 1 shear wall / 2 days

CREW PRODUCTIONCrew Task Unit QuantityC-7 Slab Concrete cy 110

Column Concrete cy 70Shear Wall Concret cy 90

4 Rodmen Slab Rebar ton 3Column Rebar ton 2.3Shear Wall Rebar ton 3

C-2 Slab Forms sf 560C-1 Columns Forms sf 240

Shear Walls Forms sf 790

Schedule AnalysisOriginal System



-Columns- 2 Form crews- 1 Rebar crew- 1 Concrete crew

-Elevated Slab-4 Form Crews-3 Rebar Crews-2 Concrete Crews

-70 Columns in 10 days-2.3 crews needed

Schedule AnalysisNew System



-Columns / Shear Wall- 3 Form crews- 1 Rebar crew- 1 Concrete crew

-Elevated Slab-4 Form Crews-3 Rebar Crews-2 Concrete Crews

-70 Columns & 2 Shear Walls in 10 days-Equivalent to 82 Columns

-2.73 crews needed

Schedule AnalysisConclusions



- Both systems require same crews for elevated slab work

- New structural system requires 1 additional crew for columns / shear walls

Office LightingInitial Considerations

-Ceiling height is approximately 11’-8”

-No finished ceiling

-Exposed underside of concrete slab

-Exposed Mechanical 18” Deep

-Spaces used primarily used for office work

-Requires Approximately 50fc or 500lx on the work plane

-Best choice for these requirements is an indirect lighting system



Purpose Design a general lighting system for the open office spaces

Office LightingDesign



-Due to exposed mechanical systems and no finished ceiling, indirect lighting would not work well

-Decision to incorporate reflector panels was made

-Provide ideal surface for reflected light

-Hang 24” from ceiling

-Able to provide access to exposed mechanical and fire protection services

Office LightingResults



-Model was created using Lightscape

-Peerless LDX030452 was selected

- Uses (3) 32W T8 lamps

- Input Wattage of 113W

-Produced approximately 510lx on work plane

-Power density of 0.715 W/sqft

Office LightingRenderings



Conclusions & Recommendations



- Floor slabs were reduced from 9” to 8” resulting in an 11% reduction in dead load

- Implementation of shear walls reduced bending stresses in columns

- Column size reduced to 24”x24”

-43.8% reduction in volume

-2200 sqft of additional floor space

- New design results in a savings of $70,000

- No change in floor cycle time

- Lighting design provides an efficient and aesthetic pleasing system for the general office spaces

Acknowledgements



Thank You to the following….- Discovery Communications Inc.

- Clark Construction Inc. with special consideration to

Ray Sowers

George Conard

Ken Alexander

- The entire AE Faculty with special consideration to

Dr. Lewis Geschwindner

Dr. Thomas Boothby

Dr. Linda Hanagan

- My Family

- My Friends in and out of Architectural Engineering

Questions



- Silver Springs, MD

- Intersections of Georgia Avenue and Colesville Road

- Approximately 8 miles from downtown Washington D.C.



Location

Building Overview

- Multipurpose Office Facility- two independent towers, of 7 and 10-stories- 3 levels of underground parking- 550,000 sqft. of open office space- $52 Million overall cost

Layout & Function

Architecture- Aluminum and Glass curtain wall system-12-story glass atrium connects the two building- Rooftop Terrace and Garden



Structural AnalysisShear Walls

- No impact on existing mechanical and Fire Protection Services



Structural Analysis3D Analysis



LATERAL DISPLACEMENTS - 3D MODEL

X Y X Y X Y X Y

Roof 0.186 -0.775 0.186 -1.967 -0.172 -0.775 -0.172 -1.967

8 0.168 -0.764 0.186 -1.865 -0.162 -0.765 -0.162 -1.865

Roof 4.94 0.23 4.94 -0.163 2.82 0.23 2.82 -0.163

8 3.644 0.214 3.644 -0.155 2.594 0.214 2.594 -0.155

Diflection (in)

NE NW SE SW

Seismic w/ Torsion EW

Load Condition Location

Wind w/ Torsion NS

Direction

Breadth Aspects

Lateral System Cost Analysis Determine cost implications of new structural systems

Lateral System Schedule Analysis Analyze construction time and sequencing of new structural

system via floor to floor erection time



Office Lighting Design Design a general lighting system for the open office spaces

discovery communications headquarters silver springs, md josh woolcock structural option...

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