AE Senior Thesis 2009 U.S. Pharmacopeia Headquarters Consolidation Rockville, MD

AE Senior Thesis 2009

U.S. Pharmacopeia Headquarters Consolidation

Rockville, MD

Analysis and Design of a Mild ReinforcedOne way slab with Post Tensioned Beams

Jeffrey L. Rothermel Jr.The Pennsylvania State University

Department of Architectural EngineeringStructural Option

Discussion Topics

• Background Information

• Existing Structure

• Design Goals

• Project Stages and Process

• Structural Design

• Mechanical Ductwork Redesign

AE Senior Thesis 2009|U.S. Pharmacopeia Headquarters|Jeffrey L. Rothermel Jr.|Structural Option

U.S. Pharmacopeia Headquarters


• Owner: U.S. Pharmacopeia• Architect: Hellmuth, Obata + Kassabaum (HOK)• Structural: Cagley & Associates Inc.• MEP: R.G. Vanderweil Engineers• Construction: DPR Construction Inc.

• 6 stories - 91’• 191,000 ft2 of new office and lab space• New 19,000 ft2 conference center• Houses chemical and biological labs• $69 million

U.S. Pharmacopeia Headquarters


• Showcase laboratory spaces• Large open office plans• Kitchenettes for employees at every floor• Curtain wall, metal paneling, and beige split face CMU• Conical auditorium with curtain wall skin• Enclosed outdoor plaza space

Existing Conditions


• Two way mild reinforced concrete flat slab with drop panels

• 22’x22’ column grid

• 14’ floor-to-floor heights (Typ.)

• Reinforced concrete moment frames

• Steel framed conference center

• Truncated, conical concrete auditorium

Photo courtesy of HOK Inc.

Photo courtesy of HOK Inc.Photo courtesy of HOK Inc.

Design Goals


• Lower floor-to-floor heights from 14’ to 13’

• Increase column grid from 22’ to 44’

• Eliminate moment frames

• Reduce ductwork sizes

• Maintain existing ceiling height

Design Stages


• Investigate 3 alternatives

• Choose optimum system

• Design chosen floor system

• Design matching lateral system

• Resize ductwork mains


Possible Solutions

Staggered Steel Truss systemTaken From AISC Design Guide 14: Staggered Steel Truss Framing

Two way post tensioned slab

One way slab with post tensioned beams


Structural Depth DesignDesign Process

1. Lay out beams2. Design slab system3. Design post tensioned beams

1. Size2. Tendon quantity3. Drape

4. Column check5. Design shear walls

1. Shear reinforcement2. Flexural reinforcement3. Coupling beams


One way slab with PT beam design

New Beam Layout


One way slab with PT beam designSlab Design

• One way reinforcing

• 7” slab typ.

• 7-1/2” slab at 250 psf loading

• #5 bars T&B

• #5@ 24” for shrinkage and temperature parallel to beams



Designed with RAM Conceptper ACI 318-02

• Spans extended to 44’• Shallow wide beams • Existing column size kept (24”x24”)• F’

c = 6000 psi• Class T Transitional• T-Beam properties• #6 Bottom at ρmin= 0.004• #5 Top with no minimum reinforcement• 0.6f’

ci compression limit (18.4.1(a))• 7.5√f’

c ≤ft ≤ 12√f’c tensile stress limit (18.3.3)


One way slab with PT beam designDesign Process

1. Size the beams2. Add tendons3. Check stresses4. Adjust profile5. Schedule



• Interior beams typically 48”x14”

• Edge beams typically 30”,32”x14”

• 40-60 tendons interior typically

• 30-40 tendons in edge typically



Transfer Girders

• 16-30” deep at transfers• 48-56” wide at transfers• Same depth as existing transfers• 20-50% more post tensioning



Load Balancing Load Balancing (% DL)Span 1 2 3 4 5 6 7

Floor Col Line First A 73 87 81 73 69 72

B 78 97 92 71 76 91 C 80 95 94 74 80 67 D 75

77 67 100 83

E 72 75 64 97 85 F 78 94 90 72 76 93 G 91 87 88 86 69 72 77

Second A 76 90 83 75 70 74

B 91 110 99 76 69 69 C 86 110 94 72 66 65 D 67

88 69 89 95

E 69 85 64 92 99 F 97 88 98 79 73 74 G 76 95 95 93 60 77 83

Third A 71 87 83 76 71 78

B 73 72 77 70 64 76 C 77 95 82 75 70 81 D 50

72 70 110 81

E 68 70 65 110 80 F 93 87 74 66 64 74 G 99 100 78 82 39 69 93

Fourth B -2 90 88 85 76 73 75 C 38 110 91 90 85 85 32 D 16 78

65 64 100 69

E 16 75 64 60 100 75 F 40 64 86 74 70 64 75 G 67 87 95 86 100 88 81

Penthouse B -57 65 82 93 78 110 80 C 19 82 98 100 90 89 88 D 34 86

95 61 100 45

E 27 95 93 59 100 42 F 62 89 96 92 89 96 100 G 58 90 100 93 84 100 78

• Balance % of dead load• Target balance 60-90%

• Target met in most beams• A few beams overbalanced• Some underbalanced


One way slab with PT beam designExisting Column Properties• Checked using PCA Column• Moments from RAM Concept at column

• Interior columns sufficient• Exterior columns require increased rebar

• Required for increased moment• 8#9 12#9


Shear Wall Design

Existing reinforced concrete moment frames


Shear Wall Design


Shear Wall Design

Taken From ASCE 7-05

Load Determination

• Method 2 per ASCE 7-05

• 4 wind cases investigated

• Seismic loads using Equivalent Lateral Force Method

• 18” trial thickness

• 1.6W vs. 1.0E


Shear Wall DesignShear reinforcement as required per Sec. 11.9

• Each wall/segment designed for shear and flexure separately

• Minimum shear reinforcing used• None needed for shear strength

• #4s H,V @18” Typ.

• Moment controlled reinforcing designs

• #8s Vert. for flexure


Shear Wall DesignDeflections in SAP

• 8” Membrane• Self mass included• 24” mesh• Full I values for all members• F’

c = 3000 psi

• Wind limitation H/400• Seismic limitation 0.02hxn


Shear Wall DesignCoupled shear wall design

SAP • Member self weight included• 8” Membrane• Coupling beams extend into wall face

• 2’ Rigid end offset• 48” deep beams

• Coupling beams as deep beams per Sec. 21.9.7• Designed per Sec. 10.7• Shear reinforcement per Sec. 11.7


Mechanical Ductwork design

Design Goals

• Keep loss under .25” WC/100’

• Keep fpm flow under 2500 in mains over occupied spaces

• Reduce height and increase width


First Floor

Mechanical Ductwork Redesign


Mechanical Ductwork Redesign

• Vertical mains shrunk 8-20” per side

• Maximum horizontal run that travels under beams is 20”

• Minimum ceiling height is 8’10”

• Average ceiling height can be +10’6”


Façade SavingsFloor sf curtain wall sf split face CMU sf metal panel

4th 758 - -3rd 758 - 562nd 204 604 561st 204 604 56

Total 1924 1208 168$/sf 65.65 62.72 34.04

Savings $4,309.92 $3,933.80 $1,158.72Total Savings $9,402.44

Cost of New DuctworkTotal Weight x 1.15* x Cost (installed) ($/lb) = Total Cost

42,263.2 x 1.15 x 6.79 = $330,012

Cost of Existing DuctworkTotal Weight x 1.15* x Cost (installed) ($/lb) = Total Cost

53,749.2 x 1.15 x 6.79 = $419,700 Savings From Changes $89,688 *15% added for brackets and supports

Some Quick Costs• Savings on façade and ductwork• More expense on structure


Project Summary

• Post tensioned beam system provides optimal performance

• Wide shallow beams incorporate desired attributes into floors

• 48”x14” for most interior beams and 30”x14” for most exterior

• 8” shear walls designed for moment

• Mechanical ductwork redesigned to obtain project goals

• Savings on façade and mechanical ducts, more cost in structure

• All goals reasonably attained


Questions/Comments

AE Senior Thesis 2009 U.S. Pharmacopeia Headquarters Consolidation Rockville, MD

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Transcript of AE Senior Thesis 2009 U.S. Pharmacopeia Headquarters Consolidation Rockville, MD