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TOTAL PRECAST SYSTEMSDESIGN GUIDE
2007/2008EDITION
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Glossary123
TABLE OF CONTENTS
Total Precast Systems Specification
Design Considerations
Purpose and Mission StatementThrough mutual education and understanding, we help grow one
anothers success.
As stated in our Partner of Choice Commitment, The Shockey Companies
are dedicated to serving as teachers and learners. It is in that spirit
that The Shockey Precast Group partnered with Hayes, Seay, Mattern &
Mattern, Inc. (HSMM) to create the 2007 Total Precast Systems Design
Guide. This unique reference document is structured to provide a broad
range of information about total precast systems as a viable construction
method, and to be ut ilized as a design guide by architects, owners, and
general contractors. It is provided with the understanding that this docu-
ment and the information contained herein should not be used without
first securing competent advice with respect to its suitability for any
general or specific application.
The 2007/2008 Shockey Total Precast Systems Design Guide includes
chapters on Features & Benefits, Building Envelope, Design Consider-
ations, Components & Connections, LEED, Case Studies, and Shockeys
load-bearing architectural guide specification.
We hope that this guide will give you a thorough understanding of the
capabilities and benefits of total precast systems; and that it serves as a
source of inspiration for your future designs.
Total precast systems represent the new direction of the construction
industry, especially as increased emphasis is placed on aggressive
schedules, leaner budgets, and structures that are aesthetically intrigu-
ing while being practical and functional.
The versatility, cost ef fectiveness, and flexibility of total precast make ita superior building system for a wide range of design applications. For
these reasons, The Shockey Precast Group is proud of its continued ef-
forts to advance the utilization of total precast systems.
The Shockey Companies and Hayes, Seay, Mattern & Mattern, Inc.
make no warranty, guarantee, or representation as to the accuracy or
sufficiency of the information provided herein, and neither assumes any
responsibility or liability regarding the use or misuse of such information.
TABLE OF CONTENTS
Introduction
Total Precast Systems Specification
Features and Benefits Historical Perspective
Typical TPS Applications Featured Applications Architectural Features
Design Considerations
Architectural Structural
MEP
Components & Connections
Typical Components Typical Connections Coordination with Other Trades
LEED Criteria Points Scoring Example
LEED Considerations
Recent Case Studies
Frederick County Public Safety Building Highmark Data Center Stoneleigh at Westfields Office Buildings
TPS Guide Specification
The Building Envelope
Total Precast Systems Design Gu
3
19
55
03 42 00
69
95
111
Eric Taylor Photography.
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Front cover photo:Stoneleigh at WestfieldsOffice Buildings
Left:Frederick County Public SafetyBuilding Erection, Stairs.
Below:The Frederick County Public
Safety Building showcases how the
successful marriage of structural precast
components with architectural precast
features creates the unique building
method known as total precast systems.
Contents page:Stoneleigh at
Westfields, Office Buildings I and II
Eric
TaylorPhotography.
The Shockey Precast Group
219 Stine Lane
Winchester, VA 22604
540-667-7700
www.shockeyprecast.com
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THE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM INTRODUCTION
INTRODUCTION
In this chapter, well explore the many benefits total precast systems offer to owners, ar-
chitects, and general contractors. Well also discuss the emergence of total precast from
an overall industry perspective, and its evolution as part of The Shockey Precast Groups
history.
Features and Benefits
Total precast systems seamless-
ly integrate the strength and
integrity of structural precast
with the visual style and aes-
thetics of architectural precast.
The result is a unique build-
ing method that offers both
common sense functionality
and almost unlimited designpossibilities. In both design
and construction, total precast
delivers significant benefits for
owners, architects, engineers,
and general contractors.
SPEED-TO-MARKETThe speed-to-market of
total precast means faster
delivery of the finished build-
ing, which can result in a
significant cost savings forthe owner. Speed-to-market
enables owners to begin
leasing office space sooner,
translating to a faster return
on investment for the owner.
FLEXIBILITY OF SPACE PLANNINGFrom a design perspective, the greatest advan-
tage of a total precast system is the versatility
and flexibility of space planning options. Total
precast delivers interior space unencumbered
by a multitude of columns, allowing for greater
freedom of design options. Using this system
the trend for larger open floor plates is accom-
modated quite easily. Typical total precast
column grid spacing is 50% greater or more
than other framing systems. Room layouts are
not encumbered by the structural elements. In
short, architects and designers will have greater
freedom to obtain the optimum office layout.
A crew of 11-12 workers can easily
erect 12-14 total precast
components per day per crew.
Quick erection times and smaller
crews are just two of the benefits
of total precast that contribute to
overall safer and cleaner jobsite.
Below: Typical example of how TotalPrecast System creates openness.
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THE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM4 INTRODUCTION
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THE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM INTRODUCTION
Frederick County Public Safety Building - Interior Space Planning Layout
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THE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM INTRODUCTION
Frederick County Public Safety Building - Interior Space Planning Layout
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THE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM8 INTRODUCTION
Erection of Stoneleigh at Westfields office building. Eric Taylor Photography.
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THE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM INTRODUCTION
CONSTRUCTION COSTSFor general contractors, total precast systems provide a safer, cleaner jobsite, faster access for
follow-on trades, and an overall shorter construction schedule. A shorter construction schedule
can greatly reduce the general contractors costs (General Conditions) of running the job, while
increasing the availability of GC crews for other projects. In this way, total precast systems actu-
ally provide economic benefit to the general contractor by freeing their resources to handle more
work.
Total precast construction allows more flexibility in the General Contractors schedule than otherconstruction methods, especially in the erection of precast. Precast can be erected at an aver-
age rate of 12 pieces per crane per day, and can be erected in weather conditions that would be
problematic for the full erection of steel components. Total precast systems also offer the benefit
of requiring less site space for erection materials. As a result, total precast systems are a more
flexible construction choice for projects with a small site footprint or limited site access.
CONSTRUCTION COSTS COMPARATIVE ANALYSIS FREDERICKCOUNTY PUBLIC SAFTEY BUILDINGThe following analysis presents the costs associated with construction of the Frederick County
Public Safety Building as a total precast structure compared with costs had the equivalent buildingbeen designed as a steel frame structure with architectural precast cladding, a cast-in-place structurewith architectural precast cladding, or a brick masonry bearing structure with architectural precastcladding. As referenced in the schedule below, the use of total precast systems effectively reducedthe overall general conditions by two (2) months.
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THE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM10 INTRODUCTION
The following graph clearly illustrates the cost advantages and savings available to owners
through the use of total precast systems versus more traditional construction methods such as
steel framing, brick masonry, or cast-in-place frame. In the case of the Frederick County Public
Safety Building, the total precast system was $278,000 less than the nearest competing system,
and two months faster than the nearest competing system.
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THE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM INTRODUCTION
Historical Perspective
TOTAL PRECAST SYSTEMSThe history of total precast systems is not so much defined by specific projects, but rather by the
evolution of markets in specific areas. Total precast systems have been around and utilized since
the beginning of the precast industry in the mid 1930s. However, precast manufacturers in specific
areas have embraced this construction concept and driven their market to relative levels of success
and application by their sheer desire to prove the value and worth of total precast systems, as well as
to satisfy their passion for constructing in this medium.
The Denver, Colorado precast community, in particular, has readily and openly embraced total
precast systems as a valuable and important construction method. Over a period of several decades,
with extensive marketing, engineering, and architectural design support, as well as mentoring and
research and development efforts, the concept of total precast systems became the construction
method of choice for many office developments in the Denver area. Two excellent examples are the
Denver Tech Center and Meridian Office Park. These projects both date back to the 1970s, and
make extensive use of total precast as an economical and aesthetic value-based system choice.
Over the next several decades, the use of total precast
systems steadily gained acceptance and popularity in
projects across the nation. While it seemingly took
years to build these markets and prove the worth of
total precast, the loss of specific people or companies
significantly curtailed the use of this construction
method in the local markets. Total precast is not
a system that can be built simply to promote the medium. Successful advancement within the
construction industry is dependent upon a passionate and dedicated presence in the local precast
community, both within precast companies as well as individuals.
Today, total precast systems have gained widespread recognition for their versatility and economy.
Total precast systems represent the future of construction as a building method that offers unpar-
alleled value, cost and schedule savings, and flexibility in aesthetic presentation.
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THE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM12 INTRODUCTION
THE SHOCKEY STORYIn 1896, Howard Shockey
opened a wagon-repair and
general contracting business
in Winchester, Virginia. His
reputation for quality con-
struction and do-it-right-the-
first-time attitude quickly put
him in demand for custom
home building. Today, many
of the homes he built at the
turn of the century still stand;monuments to his legacy
of hard work, integrity, and
dedication. Howard passed
that legacy to his sons, and in the 1930s, Jim Shockey joined his father in the business.
He was later followed by his brother Ralph. In 1947, the company became known as
Howard Shockey and Sons.
In 1943, Jim Shockey teamed up with his friend Jim Crider to create the first rural
ready-mixed concrete business west of the Blue Ridge Mountains. Known as Crider &
Shockey, the company that started as the concrete division of Howard Shockey and Sons
grew to include ten plants; and became a leader in furnishing ready-mixed concrete to
the northern Shenandoah Valley region.
With the birth of the precast/prestressed concrete industry in North America, the
Shockey family was quick to recognize the numerous benefits of precast concrete, and
by 1955, had opened a small manufacturing facility for prestressed concrete as a division
of Crider & Shockey. One year later, Shockey Brothers, Inc. became the third Shockey
operating company. Now known as The Shockey Precast Group, the company special-
izes in structural, architectural, and total precast systems; and serves its customers in
the Mid-Atlantic region from two manufacturing facilities in Winchester and Fredericks-
burg, Virginia.
Crider & Shockey company truck.
Shockey Precast Group casting yard.
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THE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM INTRODUCTION
The Winchester Medical Center Parking Structure is an excellent example of how the Shockey PrecastGroup seamlessly blends functionality with pleasing aesthetics.
Fairfax Judicial Center ParkingStructure, Fairfax, VA
STRUCTURAL PRECAST SYSTEMS
Parking StructuresParking structures have always been the cornerstone of The Shockey Precast Groups structural
business. To date, weve completed more than 300 parking structures throughout the Mid-
Atlantic region. With an endless variety of finishes and features such as architectural thin-brick,
our precast parking structures satisfy both the owners desire for functionality and the designers
aesthetic vision. Some of The Shockey Precast Groups noteworthy parking structure projects
include the Calvert St. parking structure in Annapolis, Maryland, Shady Grove Metro Station in
Rockville, Maryland, The Winchester Medical Center parking structure in Winchester, VA andFairfax Judicial Center parking structure in Fairfax, VA.
Calvert St. Parking Structure,
Annapolis, MD
Shady Grove Metro Station,Rockville, MD
Largo Metro Station,Rockville, MD
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THE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM14 INTRODUCTION
Shady Grove Metro Station Parking Structure, Rockville, Maryland
Eric
TaylorPhotography.
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THE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM16 INTRODUCTION
TOTAL PRECAST SYSTEMSThrough the years, the development of the precast industry evolved from purely structural applica-
tions such as bridges and parking structures to architectural features such as precast cladding appro-
priate for office buildings. As the almost-limitless design possibilities of architectural precast were
realized in the construction industry, architectural precast systems
became a means for designers to bring their architectural visions
to life. The natural marriage of structural capability with archi-
tectural features and finishes created the unique system known
as total precast. For The Shockey Precast Group, specializationin this building method flowed naturally from its expertise and
experience in structural and architectural precast systems.
SHOCKEY TPS HISTORYIn 1983, The Shockey Precast Group constructed the Tracor
office building in Northern Virginia. The project was significant
because it signaled Shockeys entrance into the total precast sys-
tems industry. With the success of Tracor, industrial warehouse
total precast projects such as Hershey Foods warehouse and Echo-
star Communications followed. For almost 25 years, the Shockey
Precast Group has been the Partner of Choice on numerous totalprecast projects, including most recently the 2006 PCI Design
Award-winning Highmark Data Center in Harrisburg, Pennsylva-
nia, Stoneleigh at Westfields Office Buildings I and II in Chan-
tilly, VA; Frederick County Public Safety Building in Winchester,
VA, and Commonwealth OCX Data Center.
The Tracor office building was SPGs first total precast project.
Tracor office building erection
Tracor office building
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THE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM INTRODUCTION
Fredrick County Public Safety Building, Winchester, VA
Echostar Communications uplink facility
Highmark Data Center, Harrisburg, PA
Stoneleigh at Westfields, Chantilly, VA
Eric
TaylorPhotography.
Eric
TaylorPhotography.
Stoneleigh erection
Fredrick County Public Safety Building erection
Highmark Data Center erection
Echostar Communications
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THE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM18 INTRODUCTION
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THE BUILDING ENVELOPETHE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM
THE BUILDING ENVELOPE
This chapter will provide a glimpse of the wide array of design
possibilities offered through total precast. Featured projects
will explore a sampling of building geometries, while Archi-
tectural Features references the palette of finishes and articula-
tions that can be combined to satisfy even the most demanding
designer.
Typical Total Precast SystemsApplications:
Public Safety Building Mission Critical Data Center Class A Office Building Typical Mixed-Use Retail
Total precast systems offer a myriad of structural design pos-
sibilities. Far more than the stereotypical gray box, the
versatility of total precast lends itself well to a diverse range of
design options. Following is a sampling of the total precast
system possibilities available with Shockey. These designs do
not represent the full extent of our capabilities, but illustrate
the flexibility of total precast in building geometry.
Stoneleigh at Westfields Office Building One erection, 2006
Stoneleigh at Westfields project wall panelRooftop view of completed Stoneleigh at Westfields Office BuildingsOne and Two
Eric
TaylorPhotography,2006
Eric
TaylorPhotography,2
006
Eric
TaylorPhotog
raphy,2006
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20 THE BUILDING ENVELOPE THE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM
Featured ApplicationsPUBLIC SAFETY BUILDINGThis 61,500 SF county government building
was constructed to house the Sheriff and Fire
and Rescue Departments. It was designed to
also include space for the Emergency Commu-
nications Center and Emergency Operations
Center. A total of 287 precast components
were used in the erection of this building,
including 105 double tees, 10 columns, 6 stair
modules, 32 cornice pieces, 118 wall panels,10 beams, and 6 flat slabs. The most challeng-
ing engineering design encountered for this
project involved the analysis and design of
two (2) precast header beams for the interior
stair core. In order to accommodate bearing
for stair risers, flat slabs, and double tees, the
cross-sectional geometry of these members
changes several times along the length of the
pieces; requiring rigorous analysis and detailing
of reinforcement.Erection, phase 3.
Erection starts.
Erection complete.
Eric
TaylorPhotography.
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THE BUILDING ENVELOPETHE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM
Government Public Safety Building - Typical Office Roof Framing Plan
Roof plan showing double tee layout framing with center line column and beam bearing.
Government Public Safety Building - 3D Building line view
Modeling perspective showing precast panelization along frontage view. Double Tee roof and
floor framing, interior supporting beam line with exterior load bearing wall panels.
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22 THE BUILDING ENVELOPE THE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM
Government Public Safety Building - Elevation on Grid A, South Side
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THE BUILDING ENVELOPETHE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM
MISSION CRITICAL DATA CENTER
This 317,000 SF industrial-use data center was constructed for a private corporate owner. Atotal of 1,366 precast components were utilized in the construction, including double tees, in-
verted T-beams, wall panels, stairs, insulated walls, and screen walls. The mission-critical nature
of this building required that it be designed Seismic performance category C basic wind
speed of 162 MPH, with a mechanical room floor live load of 150 PSF, and emergency generator
rooms live load of 225 PSF.
Mission Critical Data Center - Typical Office Floor Framing Plan
Floor plan illustrating double tee floor, beam, column and perimeter wall panel member placement.
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Mission Critical Data Center - East Elevation Along grid A
Building cross section showing double tee, beam and column framing members.
Mission Critical Data Center - West Exterior Along Grid G
Elevation of wall panel layout and placement- (match line indicates building continuation).
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THE BUILDING ENVELOPETHE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM
HIGHMARK DATA CENTERThis 82,000 SF, two-level precast building was constructed to house the offices and computers
for Highmark Blue Shield of Camp Hill, PA. The building was designed for a 150-psf live load
plus 70 psf roof loads, and to withstand wind bursts of up to 110 MPH. The exterior of the
building is a combination of multiple-depth sand blasted R-16 insulated precast wall panels and
laid-up brick. 16 screen walls enclose an open courtyard around external mechanical equip-
ment. Precast played an important role in the Leadership in Energy & Environmental Design
(LEED) of the building. Use of slag in the precast concrete mix design provided 20% use of
Mission Critical Data Center - Building Cross Section Along Grid 2 (top) and Building
Cross Section Along Grid 4 (bottom)
Building cross section showing double tee, beam and column framing members.
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26 THE BUILDING ENVELOPE THE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM
recycled materials. The structures design allows for future expansion of the facility. The
structure was erected in only 5 weeks, enabling the General Contractor to compress his overall
schedule to meet the Owners move-in requirements.
Highmark Data Center - First Floor Framing Plan
Floor framing plan illustrating double tee floor, beam, column and perimeter wall panel member
placement. Area in layout shown as highlighted in small 3D reference model at lower right.
Below left: Highmark WestElevation. Below right: Wallalong column line 1.
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THE BUILDING ENVELOPETHE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM
Highmark Data Center - Second Floor Framing Plan
Floor framing plan illustrating double tee floor, beam, column and perimeter wall panel member
placement. Area in layout shown as highlighted in small 3D reference model at lower right.
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28 THE BUILDING ENVELOPE THE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM
Highmark Data Center - Roof Floor Framing Plan
Floor framing plan illustrating double tee floor, beam, column and perimeter wall panel member
placement. Area in layout shown as highlighted in small 3D reference model at lower right.
Below right: Typical roof/floor framing plan. Below left:Typical inverted tee beam-to-column connection.
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THE BUILDING ENVELOPETHE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM
Highmark Data Center- North Elevation
Building Elevation of wall panel layout and placement.
Highmark Data Center- East West Elevation. (Top)East Elevation along line F. (Bottom)West Elevation Along Line R.
Building Elevation of wall panel layout and placement.
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THE BUILDING ENVELOPETHE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM
CLASS A OFFICE BUILDINGThis project consisted of two 221,000 SF mirror-image office buildings and a single elevated
level, 59,000 SF precast parking garage constructed for an insurance company. Approximately
464 precast components were utilized for each office building, including columns, spandrels, 12
x 26 x 2 flange double tees, stair walls, elevator walls, and stairs. Approximately 195 precast
components were utilized for the parking structure, including columns, spandrels, stair walls,
stairs, shear walls, and 12 x 30 x 4 flange double tees. This represents The Shockey Precast
Groups most recently completed total precast office building project.
Class A Office Building - Typical Office Floor Framing Plan
Floor framing layout showing placement and span integrating three stairwell-elevator areas.
Note center beam bearing line permitting long span column free areas.
Eric
TaylorPhotography.
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32 THE BUILDING ENVELOPE THE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM
Class A Office Building - West Elevation on Grid C
Class A Office Building - East Elevation on Grid A
Stoneleigh at Westfields EastElevation.
Eric
T
aylorPhotography.
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34 THE BUILDING ENVELOPE THE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM
Mixed Use Retail - First Floor Framing Plan
Mixed Use Retail - East Elevation On Grid F
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Mixed Use Retail - West Elevation On Grid F
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36 THE BUILDING ENVELOPE THE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM
Architectural FeaturesFinal design of the faade is an iterative process that begins with the sampling process and ends
with mock-ups.
SAMPLING PROCESS12 x 12 samples are an effective means for realizing the architects concepts into a production
standard. Samples can include one or more colors, finishes, or different materials (such as brick or
stone) cast into the precast. The varieties available are almost endless. These samples establish the
basis for beginning the mock-up process and are the catalyst for other exterior selections such as
glazing, window and door framing, and other exterior design features.
Initial precast selections may be made using the Precast Concrete Institute (PCI) Architectural
Color & Texture Guide, available through your Shockey Precast Group Sales representative. This
Color & Texture Guide presents the vast array of colors, textures, and finishes available with precast
concrete, and establishes a baseline guide for actual samples. Production samples may be obtainedfrom a local PCI-certified producer. Selecting a sample from a producer close to the project site
will demonstrate to the designer the range of available materials, as well as specific production ca-
pabilities and finish qualities. Locally produced precast may be more cost effective due to reduced
material shipping costs both for the raw materials and final delivery to the site.
After the project is awarded
to the general contractor, a
submittal sample should be
obtained from the precast sub-
contractor. Like the produc-
tion sample mentioned above,
obtaining this sample from the
precaster awarded the project
is critical due to variations in individual plant preferences, differences in techniques, and sources
of materials in the various plants, even within the same region. It should be noted that it may be
difficult to obtain an exact match to the original production sample. Slight variations may exist in
color, aggregate, or texture from the original sample. If specified, the architect may request multiple
submittal samples to evaluate the final sample selection. Obtaining an approved sample here is
important as this will become the standard that the full scale panel mock-up will be judged against.
Mock-ups
Sample (4 x 4 or larger) mock-ups will be developed from the approved submittal sample toshow the potential variations that may occur in a larger field of exposure, and taking into account
actual design profiles. The mock-up process must be started early enough in the construction
of the project to allow for the procurement of long lead time items such as thin brick and form
liners, as well as time for precasting to obtain an approved mock-up.
Total precast project mock-ups should specifically be targeted to show the potential variations
that may occur in high-profile or dual-purpose panels where the consolidation methods may vary
due to panel function (cold pour vs. monolithic pour - see page 38). The type of applied finish
to these articulations should be taken into account during this process in order to establish uni-
formity. Slight variations from the submittal sample may be expected but should be evaluated at
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THE BUILDING ENVELOPETHE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM
this phase to maintain the overall aesthetic quality. Creating mock-ups of all the precast shapes
and configurations required on a project is usually not feasible, so key or highly visible elements
should be selected by both the architect and precast manufacturer to finalize the finish selection.
Plant visits during the casting process to view first form casts should be an integral part of the
process to ensure that the established criteria is maintained, as well as to view additional shapes
not represented during the early mock-up phase.
In cases where the faade has critical performance criteria such as blast protection, resistance to
high wind-driven rain infiltration, or aesthetics, the architect may specify and owner may autho-rize an additional expenditure for full-scale mock-up of a portion of the building exterior. This
type of mock-up will usually incorporate all of the major building components such as windows,
caulking, and other enclosure elements. In other circumstances where the performance criteria is
more aesthetic, the mock up will serve to verify the overall design intent and remove any uncer-
tainties the architect or owner may have regarding the sample. This additional approval step may
then lead to design modifications which could improve both the project appearance and perfor-
mance. Sufficient time should be built into the project schedule to do the appropriate testing,
incorporate changes, and obtain final approvals before final production begins.
The mock-up is an invaluable tool for verifying overall design intent and for establishing final finishes.
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38 THE BUILDING ENVELOPE THE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM
Cold Pours vs. Monolithic PoursCold pours are required when precast either abuts another piece of precast in the same plane
(parallel) or has a return exceeding approximately one foot (depending on the mix design) in
order to ensure a finish that will match the control sample (cast face down in form). When cold
pours are required it is highly recommended that a quirk be incorporated in the design to ensure
the best aesthetic corner finish.
Mono pours should only be used in situations where the adjacent precast is either perpendicular
to the return, does not abut any other precast or is required for structural reasons. Since thereturn leg is cast vertically the migration of air during vibration, distribution of aggregates due to
gravity and air voids do not allow for the same consolidation and appearance achieved when pre-
cast is cast flat. In most cases this requires a post pour treatment to the vertically cast surfaces to
bring them to an acceptable aesthetic level as long as they do not directly abut a parallel precast
panel that was cast face down.
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Cold Pour Quirk - cold pour line is not visible on any exposed finish areas.
Detailed Section Through 90 degree Corner Cold Pour
Cold PoursThe reason that quirked corners are highly recommended to that of a 90 degree corners is due
to the aesthetic end result based on the fabrication process. When cold pours are required the
break of between pours is made in the corner to hide the transition. For 90 degree corners this
creates a sharp corner during the fabrication process. The coarse aggregate (which helps provide
the required strength) cannot flow into the sharp corner during the casting process. This allows a
slurry mix of fine aggregates and cement paste to get through, creating the following two issues:
1. The extreme corner tends to have a color and appearance slightly different from the mainbody of the panel.
2. Due to the lack of coarse aggregates in the sharp edge, there is a higher probability of
chipping and spalling of the outermost surface when standing the first pour up on edge.
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Step by Step Details on the Cold Pour Process
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Thin Brick VeneerOne finish option to consider in the total precast system is thin brick veneer. This system can
eliminate many of the drawbacks to conventional brick, which is typically field labor intensive,
weather sensitive, and time consuming. Conventional brick is also subject to water infiltration.
These limitations can be overcome when the desired aesthetic application of brick is married
with precast to create a thin brick veneer. Nearly all colors, textures, and finishes available in
hand-laid brick can also befound in thin brick veneers.
When the pleasing visual
appearance of traditional
clay products is combined
with the economy, versatil-
ity, and strength of precast, it
provides numerous benefits
to construction utilizing total
precast.
Incorporation of thin brick
into precast allows for strin-gent quality control methods
to be implemented in a plant
environment. Concrete batch-
ing systems and the curing
environment are more tightly
controlled, and utilizing clay-
faced products in this method
has the advantage of reducing
efflorescence, which is generally
caused by water infiltration.Typical column cover
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In order to successfully marry these two products, the strict modular requirements of
plant-cast precast are incorporated into the dimensionally loose tolerances of traditional
hand-laid brick. Four main thin brick (TBX) suppliers support the dimensional controls
required by PCI found in thin brick Type TBX of ASTM C1088. These manufacturers
provide almost all of the styles, sizes and features available in traditional brick, including,
but not limited to brick corners, edge corners, and three-sided corners, which provide the
look and feel of hand-laid brick.
Thin brick is designed specifically to create an integral bond between the brick veneer
and precast units. This occurs during fabrication of the clay modules by scoring and/
or creating dovetail slots on the rear to increase the bond capacity in both shear and ten-
sion. The bricks are secured into the form through the use of a rubber liner, plastic liner,
or snap liner. Each type of liner has its own unique benefits, and the decision to use a
particular liner or combination of liners is based on specific applications.
Brick veneer panels typically receive an acid rinse after being removed from the form.
The acid rinse removes surface laitance from casting, and etches the precast jointsbetween the brick, exposing the sand to mimic hand-laid brick mortar. Although
thin brick is placed and cast in the concrete, it will retain some of the desirable mild
imperfections found in hand-laid brick, and should be held to the same tolerance and
standards outlined by the Brick Institute of America.
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Brick Bond Types and Joint Treatments for Thin Brick
Almost any bond type and joint treatment that is available with hand-laid brick is available in the
thin brick system including specialty and custom bond types. Clarity in designating the exact
bond type desired is needed since some of the pattern types have slight variations of interpreta-
tion from region to region. Examples of some of the typical bond types available are noted below
and are available with both a tooled joint and raked joint:
Thin Brick Application
Depending on the color or type of thin brick selected, the appropriate liner best suited for that
particular brick is utilized (i.e. elastomeric, plastic or snap grid). Once the full delivery of bricks
are at the precast plant, they then need to be mixed throughout the shipments to insure that the
desired variations in brick are evenly dispersed over the brick fields. Each brick is hand laid into
the form to ensure a snug fit to insure a good seal around its perimeter. Once this is complete
they are now ready for the back-up facing mix which will provide the simulated grout joint color.
Flemish Bond 1/3 Running Bond Running Bond
Stepped 1/3 Running Bond Herringbone Offset Weave
Soldier CourseBasket Weave
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ArticulationsArticulations express the design intent of the architect while adding life to the precast fa-
ade and establishing the unique character of the building. They provide visual interest
for both close up and distant viewing. Flexibility and design freedom are the hallmarks
of precast faade design. A key advantage for the designer is that precast can be formed
to achieve almost any imaginable design and shape. No other building component sys-
tem can rival this flexibility. Applied finishes should always be considered when design-
ing articulations in order to achieve the maximum aesthetic benefits of precast.
Applied finishes are surface treatments that are for the most part achieved after the
precast panel has been cast and stripped from the form. This is done through a variety
of techniques used to break or disrupt the outer paste layer of the precast surface and
expose at various degrees either the fine or coarse aggregates utilized within the mix.
Although specialized tools and equipment are used in this process, it still requires the
specialized skills and eye of the precast finishing artisan to maintain a consistent pleasing
final finish.
Common precast articulations
include the following shapes and
designs:
Lintels
Bull nose Cornice
Reveals
False joints
Medallions
Fins
Projections
Recesses
Quirks
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The use of precastarticulations can
greatly enhance abuildings individualstyle and character.
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Articulations are often incorporated into building designs to create a striking or dramatic faade.
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Mix DesignsMix design represents the proportions of cement, water, pigments, admixtures, fine and coarse
aggregates. These base components comprise the initial sample selection. In a total precast sys-
tem, a variety of mix designs may be utilized based on specific precast performance requirements.
The requirements will vary depending on whether the precast component is structural or purely
architectural in nature.
Depending upon project design requirements, mix design proportions can be adjusted to meet
project requirements averaging, but not limited to 5,000 -- 7,000 psi. This range far exceeds
the 3,000 psi capabilities and performance of traditional cast-in-place concrete. Breakthroughs
such as self consolidating concrete (SCC) have significantly expanded precasts ability to meet
the demands of even the most challenging designs. Advances in chemical technologies have
also made it possible to incorporate specific materials, such as corrosion inhibitors, into the mix
design when structures are placed in extremely harsh environments such as coastal areas.
All of these considerations are taken into account during the formulation of final mix designs.
For architecturally exposed precast surfaces, it is highly recommended that the final finish be
achieved by utilizing only white cement. Gray cement has a higher percentage of variation dur-
ing its manufacturing process that, even when mixed with white cement, can create objectionable
changes in color or shade throughout the fabrication process. However, the use of gray cementin non-exposed areas is a key element in making precast an economically viable solution.
The designer should note that increases in cost can result from changes to a mix design. A
number of factors may influence the cost increase. In general, local aggregates are preferable
because they are less expensive. Gray cement is also more cost effective than white cement;
however, it has more variations than white cement. This can be a critical consideration when
trying to match color. In terms of pigments, earth colors such as buff and brown are typically
less expensive than red and orange. Special colors, such as blue and green, are the most costly.
The quantity of pigments will also impact cost, as will factors such as corrosion inhibitors, and
changes to aggregate quantities to meet finish requirements. When specifying particular finishes,
it is important for the designer to consider the overall cost increases associated with changes to
established mix designs. The following pages include examples of the mix designs used on Fred-erick County Public Safety Building.
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Architectural Features
COLOR, TEXTURES AND APPLIED FINISHESThe use of color and textures in precast concrete gives the designer incomparable freedom.
Through a variety of aggregates, choice of matrix colors, varying depths of exposure, and finish-
ing techniques, precast can meet almost any color, form or texture that may be specified by the
designer. Additionally, the beauty of natural aggregates is greatly accentuated when the ag-
gregates are fused with the color and texture benefits of precast. Exposed smooth form finisheswithout any applied finishes are not recommended. The resulting variations in appearance due to
form release agents, air voids, minor irregularities between form treatments and its susceptibility
to crazing all will result in a less than favorable final aesthetic appearance.
ColorIt is recommended that color selections be done in the same or similar lighting conditions as the
in-place conditions. Interior-use precast should be viewed under incandescent or fluorescent
lighting. In order to maintain matrix color uniformity, white cement should always be used (as
noted in the mix design process) along with color pigments conforming to ASTM C979. Even
when the desired matrix color is gray, the use of white cement and gray pigment is still highly
recommended.
Reliance of color based solely on natural aggregates will carry with it the same variations inherent
in nature. When reviewing cost in selections, it is important to consider the source of aggregate
if deep exposure is required (local sources are almost always more cost-effective); and to realize
that matrix colors such as blue and green are higher cost selections.
Capitol Finance Building, Richmond, Virginia
Frederick County PublicSafety Building
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articulation and configuration of the units. Final selection of the finish gradation should be made
during the mock-up phase and should include recommendations from the manufacturer. Variation
of applied finishes within the individual units can be used to enhance the overall appearance of the
building. This can be a more cost-effective means of emphasizing and accentuating key compo-
nents or areas of the facade than the use of multiple mixes. When multiple applied finishes are part
of the design, the same logic regarding profile changes and/or reveal work should be applied similar
to that of multiple mixes to ensure clean breaks.
Acid Etch FinishAcid etching is a process that dissolves the surface ce-
ment matrix to expose the sand and, to a lesser percent,
the course aggregate. Acid etching is typically used to
achieve a light- to- medium-light exposure. The end
result is similar to that of natural products such as sand-
stone or limestone. The etching process leaves a sugar-
cube appearance which is enhanced by direct sunlight.
The decision to incorporate an acid etch finish must be
made prior to or during the mix design process since
only acid-resistant siliceous aggregates (granite, quartz,
etc.) should be used. Carbonate aggregate such asdolomite and limestone, suitable for sandblasting mixes,
will dissolve or discolor through the acid-etching process
due to their calcium content. Complementary aggregate
(fine and coarse) and cement pigments should always
be chosen when an acid etch finish is selected. Design-
ers should avoid large expanses of precast without reveal work or profile changes to mask any of
the slight variations that may occur through the veining exposure of the natural sand. It is recom-
mended that expanses of unbroken precast be no larger than 4 ft x 6 ft. If an acid etch wash is to be
used on deep profile panels, these should be fabricated during the mock-up phase.
Acid etching is the crucial second step process when the building faade will include clay products
such as thin brick veneers. This process not only helps remove some of the surface latent on the
brick during the manufacturing process, but also exposes the sand between the thin brick joints to
mimic that of hand-laid brick mortar. It is also used as a safe finish around the brick veneer for in-
corporated precast features such as lintels, sills, bands, and projections that have all been integrated
within the same precast unit.
Sand Blasted Finish
Sand blast is the generic term used for the abrasive blast-
ing process. Varying gradations of blast material are used
to chip away the precast surface. Selection of a particular
gradation is dependent upon the desired depth of finish.
Sand blasting allows the designer the full range of depthsobtainable in precast (light to heavy). On final exposed
surfaces, brush blasting should be avoided because of
its inability to uniformly remove all the surface laitance,
and because it will leave the same negative effects noted
above for smooth form finishes. Light blasting provides
a similar appearance to that found in natural limestone
without the sugar cube appearance created by acid
etching. In contrast to acid etching, blasting tends to be
better suited to muting or camouflaging minor varia-
tions that occur in the manufacturing process.
Example of an acid etch finish
Example of a sand blasted finish
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This is especially true when addressing deep profile articulations. Deeper blasts have an increased
ability to ensure uniformity. However, once blasting exceeds the light level of finish and texture,
the end result is more dependent on the natural elements of the mix (aggregates). Complementary
aggregates and matrix should always be considered when specifying deeper levels of exposure. A
deeper blast can mimic other natural materials such as flamed granite, and create interesting plays
of light through its texture.
Blasting can also be a more economical means of achieving multiple variations within the same unit
rather than incorporating multiple mix designs. Blasting creates multiple variations by exposingdiffering levels of the coarse aggregate in pre-defined areas on each panel. The overall desired effect
of texture is also influenced by the type and selection of coarse aggregate in relation to the psi of the
matrix. Softer aggregates will become concave during the blasting process, while harder aggregates
will become convex, depending upon the depth of exposure.
Since the final aesthetic of sandblasting is determined mainly through the exposure of aggregates,
final depth decisions should not be made until a minimum of a 4 x 4 mock-up has been reviewed.
It is highly recommended that final depth decisions be made at the precast facility so that depth
and gradation changes can be made at the facility to allow the owner or designer to be an active
controlling participant in the process.
Exposed AggregateThis process is achieved by chemically retarding the
matrix, which provides a non-abrasive method of expos-
ing the natural beauty of the coarse aggregates. Unlike
the sand blasting process, the chemical retarder does
not mute or damage the coarse aggregates. The chemi-
cal retarder is applied to the mold surface, which delays
the cement paste from setting up. After stripping the
panel, the retarded outer surface layer of cement paste
is removed with a high-pressure washer. A variety of
depths, from shallow to deep, can be achieved depend-
ing on the type of retarder used. As with other finishes,
variations of exposure within the same unit can be
achieved with chemical retarders; however, a clear reveal
or profile change is a must for the transition points to
prevent bleeding of exposure. The choice of aggregate
size is essential when choosing depth to ensure excessive
aggregate loss bald spots do not occur. If the owner or
designers vision is to enhance the bright, natural colors of the aggregates, then chemical retarders
should be used. It is recommended that contrasting matrix and aggregate be avoided to prevent a
patchy appearance.
Form Liners
Form liners offer the designer a wide array of possibilities in terms of shapes, patterns, textures,and designs. The liner material used is dependent upon the desired effect and the number as cast
required (from metal, plastic, foam, plaster, wood or elastomeric). Any combination of applied
finishes can be utilized in conjunction with form liners. They can be implemented either as the
main aesthetic feature or as a highlight, medallion, or logo. Advances in form liner technologies
have created a design palette limited only by the imagination. When vast areas of precast will
utilize form liners, limitations of liner sizes should be incorporated with reveal work to prevent
liner butt joints. Form liners provide the highest degree of texture and will enhance the play of
light and shadows, creating a changing appearance of the faade throughout the day. Key place-
ment of night illumination can also complement the effects of the liner.
Example of exposed aggregate finish
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Form liners are a key component when implementing a thin brick veneer. The three main types
of brick liners (elastomeric, plastic grids, and snaps) each have their own positive attributes, de-
pending on project design and panel configuration. The selection of a liner should be made with
the guidance of the precast manufacturer. When a designer chooses to utilize a form liner, it is
important that the designer recognize the lead time required with form liners. Lead time will
vary by type of liner or pattern selected. Liners requiring unique artwork will require additional
time for the artisan to create the master mold.
Form liner lead times can range from between 4 to 8 weeks. When elastomeric liners are used
in conjunction with thin brick, a sample run of the actual brick being used is required in order
obtain the correct fit. The first 100 bricks from a run are measured and the form liner is based
on the average brick size. Not only does the form liner lead time need to be taken into account,
the lead time required on the brick must be considered as well. Brick manufacturing will usually
fabricate the lighter shades in the beginning of the month and the darker shades at the end (or
vice versa). Depending on the time of the month and the type and color of the brick selected, it
will normally run approximately four weeks minimum (depending on the backlog of the particu-
lar color selected) until the first run of bricks are delivered.
A custom form liner was usedby The Shockey Precast Groupto fabricate these precastmedallions for the PhiladelphiaCriminal Justice Center.
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DESIGN CONSIDERATIONS
Through this chapter, youll gain a better understanding of the architectural, structural, and
MEP design considerations that must be taken into account when specifying total precast sys-
tems. Chapter 3 will address topics such as thermal performance, fire ratings, floor vibrations,
penetration coordination, and load criteria.
Architectural
BUILDING THERMAL PERFOMANCE
How is insulation applied?There are several ways to insulate a precast concrete building. As with other types of construc-
tion, methods vary in type and complexity. When a finished wall is required, metal studs can be
installed independent of precast panels, allowing for flexibility of installation of other features
within the walls. Typically, a one-inch air gap is provided between the concrete panel and the
metal stud to form a thermal break from the exterior concrete panel. Batt insulation is then
installed within the studs to the appropriate thickness required to achieve the desired R-Value orthermal resistance. Gypsum wallboard (GWB) can then be applied to the interior surface of the
wall to produce the finished side of the wall.
In unfinished areas, such as mechanical spaces, stick pins can be applied to the concrete panels
with the batt insulation attached directly on the interior of the precast. Although this approach
does not provide for the air gap as achieved with the metal studs, it also eliminates the cost of the
metal studs, which produce a thermal break at each stud.
Insulated sandwich precast panels offer quick installation, since the insulation is installed in the
panels during the manufacturing process; however, thermal breaks occur at the edges of the pan-
Eric
TaylorPhotography.
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els where the solid concrete forms a
bridge to the interior of the build-
ing. Typically, furring and GWB is
still required on the interior of the
panel to achieve a finished appear-
ance. The furring also accommo-
dates electrical and telecommunica-
tion devices that would otherwise
have to be cast into the panels.
How is thermal integritymaintained?One of the key benefits of a concrete
structure is its thermal mass. Ther-
mal mass is the ability of a material
to absorb heat. When used as an exterior skin, a high-density material like concrete requires a
large amount of heat energy to change its temperature. High thermal mass materials act as thermal
sponges, absorbing heat during the day in summer and cooling the building by storing heat from
the sun over the surface of the building, rather than allowing it to flow into the building. This
cycle reverses at night when heat is released back out into the atmosphere. Thermal mass isnot a substitute for insulation, since the heat it stores is generally re-radiated to the exterior
of the building, but also may be radiated to the interior. The function of the insulation is
to form a barrier that stops heat flowing into or out of the building. When used in the right
combination, these two elements, along with a building design that captures solar light and
heat energy, can improve the thermal performance of the buildings and lower the overall
energy requirements.
A concrete masonry unit (CMU) has less mass than a solid concrete panel. Air bubbles
within the units provide insulation value; however, they are less dense and allow moisture
into the building. CMU blocks are produced with cores and webs within the blocks, which
allow thermal breaks at each web connection. Typically, rigid insulation is applied to the
exterior of the CMU to provide the thermal integrity of the wall, eliminating the advan-tages of the thermal mass principal.
How is the integrity of moisture barrier maintained?Since concrete is inherently dense, it helps prevent water infiltration into a facility, and
eliminates the need for additional moisture proofing materials required with other veneer
systems. CMU is porous, and requires the installation of damp proofing or waterproofing
when it is used. Flashings must also be installed at openings such as windows and doors
to compensate for the possibility of water infiltration into the facility.
Controlling relative humidity can reduce vapor migration. It is typically caused from the
affinity for water molecules to be present on the surface of most common concrete build-
ing materials. This molecular film is proportionate to the relative humidity of the spacewhere the panel is located. A major contributor of relative humidity within the space is
the HVAC system and its proper operation. If the relative humidity is controlled, the
sweating problem is alleviated.
Acoustic DampeningSound transmission loss (STC) defines the ability of a barrier to reduce the intensity of
airborne sound. Precast concrete walls, floors, and roofs do not usually require additional
treatments in order to provide adequate sound insulation. Greater sound insulation can
be attained by attaching additional layers of building materials such as gypsum board.
Impact insulation class (IIC) is measured in terms of Hertz, and examples of impact
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DESIGN CONSIDERATIONSTHE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM
a. Department of the Army. Structures to Resist the Effects of Accidental Explosions, Army TM
5-1300, Navy NAVFAC P-397, AFR 88-2. Washington, D.C., Departments of the Army, Navy
and Air Force. (1990)
b. Department of Energy. A Manual for the Prediction of Blast and Fragment Loading on Struc-
tures, DOE/TIC 11268. Washington, D.C., Headquarters, U.S. Department of Energy. (1992)
c. Department of the Army. Security Engineering, TM 5-853 and Air Force AFMAN 32-1071,
Volumes 1, 2, 3 and 4. Washington, D.C. Departments of the Army and Air Force. (1994)
d. Department of the Army. Fundamentals of Protective Design for Conventional Weapons, TM
5-855-1. Washington, D.C. Department of the Army. (1986)e. Naval Facilities Engineering Service Center, Guidebook on Protection Against Terrorist Vehicle
Bombs. (May 1998)
Certain structures have blast requirements to reduce the impact on the structure as a result of deto-
nated explosives typically car bombs and other terrorist attacks. These types of explosions result
in dynamic pressures applied to the structure. These explosions typically have much higher pres-
sures and shorter durations than wind or seismic loading. Minimizing impact on the structure due
to such attacks can help minimize the impact on the structures ability to be operational, maintain
immediate occupancy, ensure life safety and and mitigate the potential for progressive collapse.
The two main components of calculating blast pressure are the charge weight (pounds of TNT or
alternative explosive) and the standoff distance (distance between structure and detonated explo-sive). Minimizing dynamic pressures on structure due to blast can be achieved by increasing the
standoff distance through the use of perimeter security -- bollards, fencing, landscaped berms, or
anti-ram walls and/or decreasing charge weight.
The exterior skin (precast & glazing) should be designed to prevent the blast wave from entering
the building. Ideally, the exterior skin will behave elastically and absorb energy transferring loading
into the structural diaphragm. Cladding a total precast structure with architectural precast concrete
or building redundancies within the structural members can assist in blast resistance design. Ad-
ditionally, spanning exterior skin floor-to-floor will allow loading to transfer through the structural
diaphragm. Exposed structural columns or transferring dynamic loading using connections from
the exterior skin directly into the columns should be avoided wherever possible.
The structural diaphragm to resist blast loading can be comprised of interior shear walls, moment
frame spliced columns, or a hybridization of the two. The glazing manufacturer will also have to
consider blast resistance for such projects.
Whenever possible, the building should be oriented to minimize faade exposure to blast. Exam-
ple: Here is the same C-shaped structure oriented in two separate fashions. Option (2)
provides less faade exposure.
It is critical that the precaster, window manufacturer, and blast engineer be involved in early design
and development activities since determining the materials utilized for faade plays a large role in
the performance of the structure.
Identifying relative capacities of faade elements in conjunction with building performance level /
blast criteria helps to determine structural support elements.
Progressive Collapse
Designing for progressive collapse can be defined as the evaluation of a local failure from an
element distributed into other elements resulting in the collapse of a structure or a significant
part of the structure. The United Facilities Criteria (UFC) has published Design of Buildings
to Resist Progressive Collapse, which can be found at: http://www.wbdg.org/ccb/DOD/UFC/
ufc_4_023_03.pdf.Blast resistance diagrams -Option 1 and Option 2
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EMBED
CONSIDERATIONS
The coordination of embed locations between the
Precast Manufacturer and the Engineer of Record
is very important to ensure a smooth and uninter-
rupted project completion. The Engineer of Record
typically provides the design reactions and embed
plate footprint for the Precast Manufacturer. Items
requiring embeds include canopy structures, eleva-
tor rail mounts, stairwell railing mounts, piping and
equipment mounts, as well as any other items tied
into the precast structure. Aesthetics must also be
considered so that embeds can be hidden or made
inconspicuous.
Richmond Convention Center
Connection embed, Frederick County Public
Safety Building
UnistrutHandrail embed in stairs.
Handrail embed in stairs.
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SPECIAL CONDITIONS
Raised Floors:Access raised floors are used frequently to facilitate HVAC servicing and communications,
and electrical runs below office areas and computer rooms. Precast floor systems can easily be
adapted to raised floor systems and can be designed for this additional floor load. Variances
between floor levels can be accomplished with additional floor topping or other special detailing.
Following is an example of a typical raised floor.
Microwave towers/antennae:Concentrated loads from this type of equipment can vary substantially. Input from the manufac-
turer early in a project can be valuable information to incorporate into the precast design. Tower
frames and antenna racks should more effectively be placed over column or tee stem locations toavoid issues with slab punching shear.
Vibrations:Floor vibrations can cause perceptibility problems with building occupants and should be consid-
ered on all projects, particularly those with longer spans. Vibrations are particularly prevalent in
parking garages. Precast floor construction is inherently stiffer than some other types of construc-
tion and can be designed to mitigate vibration characteristics. A building can be perfectly sound
structurally, but if the floors vibrate excessively when groups of people walk by, those sitting still
could notice the vibration and become uncomfortable. In order to make the occupants feel at ease
in the building, the floor must be designed to be stiff enough to not flex objectionably when a mov-
ing load passes.
How stiff is stiff enough?The Precast Concrete Institute (PCI) has established guidelines regarding
the amount of stiffness necessary to negate the possibility of objectionable vibrations. Calculations
are performed based upon the size and length of the floor member, along with its loading. Based
on this calculation, a minimum natural frequency required for vibration prevention is calculated. A
floor member is then designed that has a natural frequency higher than the calculated minimum.
In addition to selecting a double tee with a natural frequency greater than the calculated minimum,
it is also recommended that the vibration frequency be kept above 3 Hz if possible. Since humans
have difficulty detecting vibrations higher than 3 Hz, any vibrations above that frequency become
essentially imperceptible.
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64 DESIGN CONSIDERATIONS THE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM
The ideal strategy is to avoid objectionable vibrations. If vibrations are unavoidable, then the goal
is to make all vibrations imperceptible. The Shockey Precast Group routinely spans 50 feet with
our double tees in office buildings and stores. We not only exceed the minimum values required,
but also exceed the 3 Hz recommendation as well.
Operable Partitions:Operable or hanging partitions present unique
structural challenges, but with early coordina-
tion, these challenges can be easily consideredduring the design process. It is important to
receive input from the partition manufacturer
as early as possible to obtain partition loads and
preferred structural support systems. Specific
deflection criteria should also be obtained early,
to facilitate the design of precast in the areas
where operable partitions will be used.
MEP equipment/piping:Large hanging or equipment loads should be provided to the precast manufacturer as early as
possible for incorporation into the design. When carefully coordinated, embeds may be pro-
vided to support special framing for this equipment
Heavy Office Equipment:High density filing or storage systems, computer server rooms containing multiple fully loaded
equipment rack and other areas containing special equipment can place tremendous loads on the
structural system. Typically, structural load requirements for these types of office equipment may
range between 100 to 300 psf (pounds per square foot). Equipment locations and areas of poten-
tial heavy load concentration, such as the carriage wheel rails beneath high density filing systems,
must be identified as early as possible in the design phase. Coordination with the structural precast
fabricator is imperative in order to accommodate these loads in the precast member design.
Large Openings:The flexibility of precast allows for the ac-
commodation of large openings. Embedded
concrete connections can be used to facilitate
attachment of windows and curtain walls.
Unlike steel construction, large window wall
openings typically do not require supplemental
steel framing above and below the window to
provide support. Substantial savings can be
gained by the elimination of miscellaneous steel
framing; however, careful detailing with the inte-
rior finishes is recommended to assure a proper
appearance within the space.
Expansion Joints/Building Movement:Concrete does not expand and contract thermally as much as steel, but jointing between concrete
materials and other building materials must be carefully detailed during design. Particular care
should be considered at junctions between structural and non-structural elements and also between
dissimilar materials such as concrete and masonry or steel. Thermal, structural, and moisture re-
lated movements can all cause cracking and should be addressed early by the manufacturer and de-
signer. Typically, metal studs and gypsum wall board are used to frame the interior spaces so these
can be separated from the precast panels to keep each system independent. This allows the window
system to be detailed with a flexible joint material to allow the material to move independently.
Interior partition details.
Punched windows detail.
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DESIGN CONSIDERATIONSTHE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM
Access to Connections:Sequencing of erection of precast members
should carefully consider access to connec-
tions. When concrete panels are tied-back to
steel construction, field issues can arise if the
General Contractor cannot perform the con-
nection work.
Stairs:Modular precast stairs serve to simplify the
stair erection process on building projects.
The overall project schedule can be expedited
through the inclusion of modular precast stairs
because there is then no need for a separate stair
framing subcontractor or concrete filled pans.
Stair attachments can easily be made in the field
and hidden from view from the public. Special
care should be considered when stairs are on the
exterior walls to account for the thickness of any
interior wall insulation. Connection details should be concealed or filled to allow the precast panels
to serve as the finish wall inside these spaces.
Roof Drains:One thing to consider when design-
ing any structure is how the roof will
drain. This can be accomplished in a
number of ways. The use of internal
roof drains is a common practice;
however, this can lead to roof leaks or
pipe leaks within the space. A better
solution is to slope the structure to
the rear of the building and allowsheet flow to scuppers that can direct
the rain water to downspouts strate-
gically placed on the exterior face of
the building. However, when using
this technique, one must always be
aware of clear height requirements
within the building, since the entire
slope of the roof is towards one
direction, making a deeper cut in
the rear of the building. Careful
coordination is required with the
exterior panels to assure that thescuppers line up with the top of the
roof and overflow scuppers are placed
correctly. Another consideration is
the clearance requirements for the
downspouts below grade and above
the footings.
Post-Completion ModificationsThere is flexibility in the removal of portions of the double-tee flanges to facilitate MEP pen-
etrations to enable intercommunicating stairs or other changing building uses.
Top to bottom: HVAC, con-duits, window coordination,and stairs.
Rooftop screenwall
Access to connections detail.
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66 DESIGN CONSIDERATIONS THE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM
MEP
COORDINATION OF PENETRATIONS
During design of the mechanical system, careful consideration must be given to the placement
of mechanical equipment and the location of ductwork and piping penetrations. Placement of
large equipment on the roof should also be given special consideration during the design process.
Placement of packaged rooftop air handling units is
probably the most critical item to consider during the
design of the facility. Centrally locating the air handling
units in the middle of the area to be served allows for
the shortest and most economical HVAC ductwork
runs. Placement of the packaged air handling units
should be closely coordinated with the precast system
utilized for the roof construction. The location and size
of supply and return air openings vary between manu-
facturers. Some are in close proximity to one another,
while others have a greater distance between them.
Some are parallel, while others are at right angles toeach other. The size of the required supply or return
duct opening may limit the capacity of the rooftop
unit, if the duct size can not be accommodated in the
roof slab.
Physical sizes and
weights of units vary
with the conditioning
tonnage of the unit.
Unit weights vary
from around 1,000lbsto over 17,000lbs for
the largest air han-
dling units. A prop-
erly designed precast
roofing system can
easily carry this load
while also allowing for
the proper sized holes
to allow the ductwork
to pass through.
ASHRAE 90.1 andInternational Energy
Code. The Shockey
Precast Group meets
the requirements in
90 % of the United
States with precast
wall panels with 2
insulation having a
minimum R-value of
9.5 hft2F/Btu.
Example of penetration in double tee.
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DESIGN CONSIDERATIONSTHE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM
Design for Economy
There are several areas that have the potential to significantly increase precast production and
erection costs. By being aware of these areas, and by considering the guidelines outlined below,
the architect and owner can design a building that is both striking and economical.
COMPONENT SIZE AND GEOMETRY
When designing for economy, the designer should be aware of component size and geometry.
It is generally more economical to use a lesser number of large pieces than a greater number of
smaller pieces. A lesser number of large pieces equals less total set-up time to produce the mate-
rial, fewer trips required to ship the material to the job site, and fewer operations to erect the
material. All of these save time, labor, and money.
In addition to size, the geometry of the pieces can play a large role in cost savings. Pieces that are
shaped to serve multiple functions can reduce the overall piece count, which saves money. An
example would be a shear wall that has a corbel built into the wall to carry a beam (as opposed to
a column standing beside the wall and the column supports the beam). By using the wall with a
corbel, the column can be eliminated, which then eliminates the work of designing, producing,
shipping, and erecting the column. The result is a substantial savings.
DUAL-USE COMPONENTS AND ARCHITECTURAL FEATURES
Dual-use components as they relate to total precast structures can be defined as structural com-
ponents that have architectural features.
Architectural features are created using a variety of shapes, colors, textures, and applied finishes.
When selecting accent reveals or rustication lines, it is important to tie them in to the chosen
joint size. Triangular reveals are to be avoided where possible because they are difficult to affix to
the forms. Instead, a trapezoidal reveal will provide a flat nailing surface to the form builders and
help minimize possible nail-hole irregularities. Be sure to include reveals between any and all col-
or breaks - when two separate architectural mixes are utilized within the same panel, it is strongly
recommended that designers include a reveal between the two mixes to provide the casting crew
a distinct stopping point and to help reduce color bleed. This will help ensure an unwavering
and smooth break line as illustrated in the figure below. When choosing reveal sizes also consider
limiting depth to 3/4. Deep reveals decrease the effective section of the panel, thereby reducing
panel strength and increasing the chance for panel cracking. Additionally, in dual-use compo-
nents, deep reveals may hinder the optimal reinforcing and or strand configuration.
Color #1
Color #2
Trapezoidal
Reveal
Caulk with
backer rod
Panel Joint Reveal
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68 DESIGN CONSIDERATIONS THE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM
Facial projections can add a unique accent to your building project. Because these features are
cast with panels bottom-in-form (exposed architectural finished face towards the ground), a
minimum draft dimension is necessary in order to strip panels out of the form. Without proper
draft, suction forces generated between the concrete and the form may cause the pieces to bind
up during stripping and possibly damage the piece and or the forms. To ensure this does not
occur, Shockey recommends a minimum draft of 1:6 on facial projections as noted on the sketch
below. It should also be kept in mind that facial projections tend to increase production costs,
since forms need to be built-up to accommodate the features.
Loops for stripping
MODULARITY
When designing for economy, it is important for the designer to understand that significant
changes to profiles and other architectural features such as reveals will adversely affect the project
schedule in terms of design, drawing, and forming changes. In addition to minimizing variations
in profile changes or architectural features, the designer should also consider minimizing changes
in panel heights and widths as too much variation in panel sizes will increase total piece-count
and add substantially to production and shipping costs, as well as add time to the overall pro-
duction schedule. Finally, the designer should attempt to match interior component sizes with
exterior component sizes. For example, if using 12 double tees, dont design for 30 exterior
bays. Maintaining consistency and a relative degree of simplicity will result in a structure that is
truly designed for economy.
Forms built up to create
facial projections
Facial projection
Panel in final
erected positionPanel as cast
Minimum draft
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COMPONENTS & CONNECTIONSTHE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM
COMPONENTS AND CONNECTIONS
In this chapter we will examine typical precast components utilized in total precast systems, and
gain a better understanding of the unique connection considerations that must be taken into
account when building with precast. This section will highlight the various components and
connections used in construction of the Frederick County Public Safety Building, as well as their
interaction with other building materials. Ideally, this chapter will give you a clearer picture of
the relationship between precast components and the surrounding construction elements.
Insulated Wall Panel to Double TeeConnection of a double tee with cast in place topping to an insulated wall panel. Connection
types, and styles of embeds vary as conditions require. This is detail is usually at the roof
condition.
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70 COMPONENTS & CONNECTIONS THE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM
Insulated Wall Panel to L-Beam
Connection of a double tee to an inverted tee-beam to an insulated wall panel. Connection types,
and styles of embeds vary as conditions require. This detail illustrates conditions at the roof condi-
tion. Similar condition can occur at the floor. This condition could allow for building addition-
expansion by removing and or possibly relocating the wall panel at a future date.
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Roll Restraint Corbel
Variation of a roll restraint corbel these types of connections are hidden from view because they
normally occur above the finished ceiling line where AC/MECH/PLUMB occur.
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Rectangular Beam to Column
Dap of rectangular beam permits reduced floor to floor height requirements.
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Double Tee Flange to Flat Slab w/2 Offset
This detail illustrates the flexibility needed when the floor system must depress in portions of a
double tee floor area in order to accommodate depress systems.
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COMPONENTS & CONNECTIONSTHE SHOCKEY PRECAST GROUP, WINCHESTER, VA WWW.SHOCKEYPRECAST.COM
Wall to Column
This plan view at the corner of a structure shows how a column accommodates the assembly of
load bearing beam, doubl