PLAZA AT PPL CENTER Allentown, PA Economical Design Considerations for Steel Construction Amy S....

PLAZA AT PPL CENTERAllentown, PA

Economical

Design

Considerations

for Steel

Construction

Amy S. Graver - Structural Option Spring 2003 Senior Thesis

Plaza at PPL Center Amy S. Graver - Structural

PRESENTATION OUTLINE

Introduction

Economical Design Considerations

Moment Frame Comparisons

Braced Frame Design

Composite Floor Evaluation

Mechanical Re-Design

Conclusions

INTRODUCTION


Owner: Liberty Property Trust

Primary Tenant: PPL EnergyPlus

Architect and Landscape: Robert A. M. Stern Architects

Structural Engineers: Thornton-Tomasetti

MEP, Fire Protection: PPL Energy Services Mid-Atlantic, LCC

Construction Manager: L.F. Driscoll

Architect of Record: Kendall/Heaton Associates, Inc.

Civil Engineers: Pennoni Associates

Lighting Consultant: Quentin Thomas Associates, Inc.

INTRODUCTION

PROJECT TEAM


INTRODUCTION

LOCATION

LINDEN STREET LINDEN STREET

HAMILTON STREETHAMILTON STREET

PLAZA AT PPL CENTERTOWER AT

PPL CENTER

NORTH

BUILDINGPROPOSED

PARKING GARAGE

N.

EIG

HT

H S

TR

EE

T

N.

NIN

TH

ST

RE

ET

N.

TE

NT

H S

TR

EE

T


INTRODUCTION

BUILDING FACTS

Size

$29 million base building cost, $19 million tenant specific costs

256,000 sq. ft.

200,000 sq. ft. to be leased by PPL Corporation

Uses

8-story Multi-use Building

First Floor: Retail Space

Floors 2-6: Office Space for PPL EnergyPlus

Floors 7-8: Energy Securities Trading Floors


INTRODUCTION

BUILDING FACTS

Architecture

LEED Gold Certification

Central Atrium

Winter Gardens

and Roof Top Garden

Glass Façade with Strips of

Pre-cast Concrete Panels


FoundationPartial Basement w/ Poured Concrete Walls

Continuous Concrete Spread Footings

Gravity SystemComposite Steel Beams

Composite Deck

14’-20’ Stories

30’x42’ Bays

Typical Sizes

Beams: W18

Columns: W14

INTRODUCTION

STRUCTURE


INTRODUCTION

STRUCTURE

Lateral System

Moment Frame A

Moment Frames B/C

Moment Frame D

East-West: Moment FramesNorth-South: Braced FramesA

D

B

C



ECONOMY

Introduction



Braced Frame Design


Mechanical Implications

Conclusions


40 40

3533 33 33 33

30 29 30

25 26 25 27

22

20 19

15

10

5

01983 1988 1993 1998 1983 1988 1993 1998 1983 1988 1993 1998

Material Erection Labor Shop Labor

40 40

3533 33 33 33

30 29 30

25 26 25 27

22

20 19

15

10

5

01983 1988 1993 1998 1983 1988 1993 1998 1983 1988 1993 1998

Material Erection Labor Shop Labor

CONSIDERATIONS

ECONOMY

Low Seismic Design

Braced Frames

Partial Composite Construction

% o

f C

onst

ruct

ion C

ost

s

% o

f C

on

stru

ctio

n C

ost

s



MOMENT FRAME COMPARISONS

Introduction



Braced Frame Design



Conclusions


SEISMIC DESIGN

Allentown, PA

Not Considered a High Seismic Area

Seismic Design Category B

Under More Recent Codes

Seismic Can Control

Subject to Seismic Provisions when R>3



SEISMIC DESIGN

Ductility

Lower Base Shear with Increased Ductility

Response Modification Factor

To account for ductility of a system

Cs is indirectly proportional to R

Since V= CsW, a lower R-Factor corresponds to a higher base

shear



SEISMIC DESIGN

Applied Code: IBC 2000

References AISC Seismic Provisions & Supplement 1

Connections must be designed by Seismic Provisions if R>3

AISC Seismic Provisions for Structural Steel Buildings

Connections must be stronger than connected members

Classifies moment frames based on a rotation criteria



Connection Moment Capacity per AISC

Mp

Mp

1.1RyMp

Mu

Connection Moment Capacity per FEMA 350

1.1RyMp

1.1RyMp

1.1RyMp

Mu

Response Modification Factor

R=8

R=6

R=4

R=3

Four Types of Moment Frames

Special Moment Frames (SMF)

Intermediate Moment Frames (IMF )

Ordinary Moment Frames (OMF)

Steel Systems not Detailed for Seismic Resistance

Required Rotation

θ=0.4 radians

θ=0.2 radians

None

None

DESIGN STATEMENT



Comparison

SMF

IMF

OMF

R=3

DESIGN STATEMENT


Dec

reas

ing

R-F

acto

r

Incr

easi

ng B

ase

She

ar

Less

Str

inge

nt D

etai

ling

Larg

er M

embe

rs

Sm

alle

r C

onne

ctio

ns

Mor

e E

cono

mic

al

Fas

ter

Con

stru

ctio

n

Differences Results


Connection Design

FEMA 350: rotation criteria

SMF & IMF

LRFD Manual: strength design

OMF & R=3

Web-Bolted, Flange-Bolted Connections

Approved for Seismic Use

Tested by Federal Emergency

Management Agency (FEMA)

Meets Rotation Requirements

for SMF and IMF

CONNECTIONS



Included Costs

Material Costs

Fabrication Labor

Erection Labor

Excluded Costs

Quality Inspection

Special Fabrication Procedures

COST COMPARISON



R=3SMF

Actual LoadsDesign Capacity of Members

Strong Column, Weak Beam

Smaller Members

CONNECTION COMPARISON


Moment Frame A

W18x60 W24x62

W14

x74

W14

x99

Deeper Beams

Heavier Columns


Costs Time

System R-Factor Materials Labor Fabrication Erection

Existing: SMF 8 $189,392 $85,224 1208 hrs. 467 hrs.

Most Economical 3 $237,117 $14,918 117 hrs. 484 hrs.

Savings -$47,724 $70,306 1091hrs. -17hrs

COMPARISON


$22,500 1070hrs.


1000 hrs. of Fabrication TimeCost of Stiffeners

Saves 3 weeks

Critical Path

Added Float

Start Later

ErectionRemains on Critical Path

Dependent on Sitework

and Foundation

SCHEDULE EFFECTS


3 weeks



BRACED FRAME ANALYSIS

Introduction



Braced Frame Design



Conclusions


Results of the Moment Frame Comparison

Low Seismic is More Economical

Connections Drive Cost

Try Braced Frames in East-West Direction

Eliminates 410 Moment Connections

Works Within the Proposed Floor Plan

DESIGN STATEMENT

BRACED FRAME DESIGN


Chevron Braced

Adequate for Proposed Openings

14’ Minimum Floor-to-floor Height

Accommodates a Double Door

Tenant Fitout

Rooms along

column grids

30-year lease

Try Braced Frames

ARCHITECTURE

BRACED FRAME DESIGN


FLOOR PLANS

BRACED FRAME DESIGN

Existing Moment Frames

Proposed Braced Frames


DESIGN

BRACED FRAME DESIGN

Seismic is the Governing Lateral Force for Members

Concentric Braced Frame

R=3

V=1182K

Typical Sizes

W14 Columns and Braces to Match North-South Direction

W24x68 Beams


COST COMPARISON

BRACED FRAME DESIGN

Included Costs

Moment frame members now sized for gravity only

Additional cost of connections above a typical shear connection

System Total Costs

Moment Frames (R=3) $300,861

Braced Frames $226,636

Savings $74,225


Additional Time Savings

Fabrication

Not on the critical path

Adds 3 weeks of float

Erection

On the critical path

Project Completion: 3 weeks earlier

SCHEDULE

BRACED FRAME DESIGN

Project Complete: April 30, 2003

Project Complete: April 12, 2003

Time Savings

Fabrication Erection

3 weeks 3 weeks



COMPOSITE FLOOR EVALUATION

Introduction



Braced Frame Design



Conclusions


Cost of 1 Shear Stud = 10lbs. of Steel

$0.50 Material Cost

$1.50 Labor Cost

Try Partial Composite

Is a heavier beam with fewer shear studs more economical?

DESIGN STATEMENT

COMPOSITE CONSTRUCTION


FLOOR PLANS


Floors 2-6

Existing: 100% Composite Re-design: 90% Composite

W18x35 [48]

W18x35 [44]


FLOOR PLANS


Floors 1, 7-8

Existing: 100% Composite Re-design: 40% Composite

W18x40 [48]

W21x44 [24]


Floors 100% Cost Partial Cost Savings

2-6 W18x35 [48] $94,800 W18x35 [44] $92,640

1, 7-8 W18x40[48] $55,100 W21x44 [24] $51,970$5,290

COMPARISON


Total Building Savings $5,290



MECHANICAL RE-DESIGN

Introduction



Braced Frame Design



Conclusions


Composite Beam Comparison

W18 to W21

3” decrease in usable ceiling plenum

Original Design

28”x12” SA duct below beams

Air Flow Rate = 2500CFM

Air Velocity = 1150FPM

Static Pressure Drop = 0.1in.w.g.

DESIGN STATEMENT

MECHANICAL EFFECTS


Initial Size Problems

9” duct height is required to maintain existing plenum

To supply 2500CFM at 0.1in.w.g.,

42”x9” required

Does not meet the 4-to-1 width-to-height ratio

RE-DESIGN

MECHANICAL EFFECTS


SOLUTION

MECHANICAL EFFECTS

Design

2500CFM First 16’

1900CFM Past Branch

Results

Turning Vanes in Elbow

4-to-1 Ratio past

Branch

Maintains Design

Criteria

34”x9” 42”x9”

600CFM VAV Box



MECHANICAL RE-DESIGN

Introduction



Braced Frame Design



Conclusions


Cost SavingsMoment Frames with R=3 . . . $22,000

Braced Frames . . . . . . . . . . . $100,000

Composite Construction . . . . . $5,300

Time SavingsMoment Frames with R=3 . . . Fabrication: 3 weeks

Braced Frames . . . . . . . . . . . Fabrication: 6 weeks

. . . . . . . . . . . Erection: 3 weeks

ECONOMY

CONCLUSIONS


Braced Frames are Most Economical Lateral System

Feasible with architectural layout

$100,000 cost savings

Project Completion: 3 weeks earlier

Deeper, Heavier Beams with Less Composite Action

Increases floor depth

Ceiling plenum height retained with shallower duct

RECOMMENDATIONS

CONCLUSIONS


ACKNOWLEDGMENTS

CONCLUSIONS

Pennoni Associates: Civil Engineer

Frank Adams, P.E., AIA

Jeff Ott, P.E.

Ed Sander, P.E.

The Adams Division

Thornton-Tomasetti: Structural Engineer

Hi Sun Choi, P.E.

L.F. Driscoll: Construction Manager

Ed Jackowski

Stewart-Amos Steel

Curt Zeigler

A huge thank you to everyone one who answered questions, provided information and offered support… your time and efforts are greatly appreciated.

AE Faculty

Dr. Hanagan, P.E.

Walt Schneider, P.E.

Professor Parfitt, P.E.

Jonathan Dougherty

AE Class of 2003

Rebecca Mittel

Melissa Rosol

My Family and Friends

Last but certainly not least…


QUESTIONS

CONCLUSIONS

?


Section d Composite S/A Duct Air Volume Friction Velocity

(in.) (%) (in.) (CFM) (per 100') (FPM)

W18x40 17.9 100 28x12 2500 0.10 1250

W21x44 20.7 40 36x9 2500 0.13 1300

RESULTS

MECHANICAL EFFECTS

Higher Air Velocity to Maintain Air Flow Rate

Increased noise through diffusers

Not a large enough increase to impact occupants

Duct meets industry standard for 4-to-1 ratio

PLAZA AT PPL CENTER Allentown, PA Economical Design Considerations for Steel Construction Amy S....

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