skylight

1
Facade TecNotes Series
 skylight

© Enclos Corp 2009 | www.enclos.com | 888.234.2966 | curtainwall@enclos.com

 Contents

Executive Summary 1

Introduction to Enclos Technology 3

Service and Technology 4

Structural Glass Facades and Enclosures 6

Vocabulary of Transparency 8

Research and Development 10

Case Studies

51 Louisiana 12

Station Place 18

Strength of Geometry 22

San Jose Civic Center 24

Casting Process 28

Shure Headquarters 30

Orlando International Airport 34

Las Vegas US Courthouse 36

NYU Kimmel 38

86th Street Canopy 42

Metropolitan Museum of Art 41

Deloitte Building 42

Marriott Canopy 44

Glass Umbrella 46
Enclos can provide complete
turnkey solutions to your most
challenging facade require-
ments, regardless of size, com-
plexity, product or building pro-
gram considerations. We are
highly experienced in the var-
ied special conditions involving
commercial construction, rang-
ing from design through site
installation, and including both
BIM and LEED qualifications.
 Skylight

Executive Summary

Glass in overhead applications brings conflicting attributes of natural light and other emerging technology hold the
special opportunities and equally special solar heat gain. Passive design consid- promise of turning building skins into
considerations. Among its predominant erations include siting and orientation energy producers — facade system
exterior wall applications, Enclos has of the glass structure, as well as other power plants. Smart materials and con-
produced a great many novel, fully- factors related to the solar geometry of trol systems can integrate the skylight or
glazed overhead structures: skylights the skylight or glass roof design. Interior glass roof with other building systems.
and glass roofs. The focus has been on or exterior louver and shading systems Enclos can assist in the effective analy-
expressive structural systems and long can be incorporated into the design to sis of these many variables with respect
span applications. The opportunity to reduce glare and direct solar penetration to any specific application.
flood interior spaces with natural light at key times of the day.
not only enlivens the enclosed space, The backbone of any custom skylight or
but the increased daylight levels can Glass technology presents another set glass roof system, however, will be the
lead to significant reductions in energy of variables to consider. Glass makeup structural system developed to support
consumption from artificial lighting and can be a powerful ally in the control the facade enclosure, and that is the fo-
the reduction of the accompanying heat- of unwanted solar heat gain. Thin- cus of this document. We have included
ing loads. film glass coatings, such as the now select examples of the many projects
ubiquitous low-e coatings, can improve we have been involved with over the
The solar heat gain resulting from a the thermal performance of glass quite years involving the use of glass in over-
large horizontal glass exposure can significantly. Glass body tints, PVB in- head applications, glass constructs with
easily offset any gain in energy effi- terlayers, and ceramic frits applied to a a unique and singular attribute: skylight.
ciency from daylighting, however. It is glass surface can all be used separately
important to understand and explore in combination to fine tune glass perfor-
the active and passive tools at the mance to a specific application. Building
designers disposal to balance the often integrated photovoltaic systems and

Enclos Corp - 1
Introduction to Enclos
Technology

Enclos is expert in the design, engi-

neering, fabrication, assembly and
erection of custom curtainwall systems
and structural glass facades, providing
complete design/build services to the
construction marketplace.

We specialize in innovative architecture

and challenging building projects. No
project is too large, no building site too
difficult for our seasoned operations
teams. Our work experience includes
many projects with specialized materi-
als, complex geometry, and innova-
tive structural and mechanical system
designs. Enclos curtainwall and facade The integration of glass and structure is Managing the project delivery process
systems incorporate state-of-the-art a predominant attribute of this expres- is the core strength of Enclos, some-
materials and performance. sive building form, often employed to thing at which we excel beyond all our
maximize transparency in large public competition. This capability provides us
The attributes most appreciated by our spaces. Enclos has played a leadership consistent control over the vital require-
clients however are our site manage- role in the development and application ments of schedule, quality and cost,
ment capabilities and our track record of of this cutting-edge technology, includ- and allows us to consistently deliver
meeting demanding project schedules. ing a range of structure types: top quality economically and on time.
This capability is the basis for our many
• cable nets long term relationships with developers,
• cable trusses general contractors and architects.
• long-span truss systems
• grid shells Each new project undertaken by Enclos
• spaceframes is treated as unique, and a custom
• all-glass structures delivery strategy is developed in direct
response to the singular set of consid-
Our glazing systems include point-fixed erations presented by the project. This
types in both bolted and clamped ver- custom strategy however, is developed
sions, as well as framed system types, through a uniform process unique to
all custom designed in response to Enclos that embraces the spectrum of
specific project requirements. For more activities from preconstruction through
information see the section titled, Struc- design, engineering, procurement,
tural Glass Facades and Enclosures. fabrication, assembly, and erection. This
process, developed and refined through
the successful completion of hundreds
of remarkably diverse facade and cur-
tainwall installations, serves to mitigate
the inherent risk of a challenging build-
ing project by enhancing the predictabil-
ity of performance, schedule and cost.

Enclos Corp - 3
Service and Technology

Design and Engineering Project Managment

Managing the project delivery process

is the core strength of Enclos, some-
thing at which we excel beyond all our
competition. This capability provides us
consistent control over the vital require-
ments of schedule, quality and cost,
and allows us to consistently deliver
top quality economically and on time.
This capability is the basis for our many
long term relationships with developers,
general contractors and architects.

Each new project undertaken by Enclos

is treated as unique, and a custom
delivery strategy is developed in direct
response to the singular set of consid- The foundation of a successful facade Project management is an empowered
erations presented by the project. This or curtainwall project is innovative sys- function at Enclos Corp, and key to
custom strategy is developed through a tem design and engineering. Our D&E our success. Personnel skilled and
uniform process unique to Enclos that group develops custom solutions to experienced in project management are
embraces the spectrum of activities each new project, derived from a robust vital to the success of any construction
from preconstruction through design, framework of Enclos technology and project. Our project management teams
engineering, procurement, fabrication, know-how. Design considerations range lead design development, production
assembly, and erection. This process, from the aesthetic and performance engineering, fabrication and assembly,
developed and refined through the requirements determined in collabora- and field operations, bridging these
successful completion of hundreds of tion with the architect, to the fabrication various activities to form an organized,
remarkably diverse facade and curtain- and installation requirements that must unified continuum of project develop-
wall installations, serves to mitigate the be anticipated by the system design to ment throughout the design and build
inherent risk of a challenging building assure a successful project completion. process. Enclos project management
project by enhancing the predictability personnel receive extensive training and
of performance, schedule and cost. An in-house team of engineers, archi- years of on-the-job experience before
tects and designers over 100 strong being appointed to the position and en-
comprise the Design and Engineering trusted with the responsibility of running
Group at Enclos Corp, representing a their own projects.
unique talent pool that has consistently
delivered innovative, effective and el- Our people understand the critical
egant solutions to the most demanding importance to a building project of
building facade requirements. Autocad, on-time, on-budget performance, a fact
Inventor, Revit, Space Gass, Strand which our past clients can best attest
7, FloVENT CFD, are among the many to. We will happily provide you with such
tools that comprise our design devel- references.
opment process. Building Information
Modeling (BIM) is another service we
provide our clients.

4 - Skylight
Fabrication Quality Assurance Site Operations

Curtainwall fabrication and assembly is Design or material supply problems Enclos has been awarded many of its
a critically important part of the project surfacing in manufacturing are a frus- projects over its competitors because
development process. Enclos Corp trating and costly annoyance; design or of its reputation for performance on the
maintains dedicated manufacturing manufacturing problems surfacing on building site.
operations in key geographic locations the building site are a disaster. There
capable of providing fabrication services is far too much at stake in the build- Everyone involved in the construction
for the most complex designs and the ing process to settle for anything less process knows the critical importance
most challenging project schedules. Our than top quality and the programs that of the building site, the playing-field for
facilities incorporate state-of-the-art consistently deliver it. Effective qual- the contracting teams. This is where
equipment and processes for curtainwall ity programs garner the participation the myriad complexities of a construc-
unit fabrication and assembly. In addi- of everyone in the organization from tion project converge and coalesce into
tion, to provide adequate capacity for top to bottom while reaching through- architecture. The building site must be
the fluctuating demands typical of the out the web of company operations a particular focus for systems such as
building marketplace, we have devel- and activities. We have developed and the building skin where a large part of
oped a network of outside fabrication refined our quality assurance and quality the process takes place off site; design,
sources, all of whom have been rigor- control programs over the span of many engineering, fabrication and assembly
ously trained and qualified in all aspects years and hundreds of diverse proj- all precede the delivery of material to
of Enclos systems materials, fabrication ect experiences, another way that our the site and the commencement of field
and assembly, and all of whom have deep experience works for you. These installation. Yet the site is where all must
successfully provided services on prior programs are robust and all embrac- come together. These preceding activi-
Enclos projects. ing, ranging from management systems ties must be accomplished with a keen
and procedures to the minutia of in-line eye to the site, anticipating unique site-
quality verification processes. In addi- specific requirements and developing
tion, we develop a specific quality plan effective installation strategy to assure
for each new project based on an analy- an efficient and effective performance.
sis that identifies and accounts for any
unique aspect of the project whether it Field operations are a core strength of
be material type, location, site condi- Enclos Corp, and the attribute for which
tion, performance requirement or design we are most widely recognized by the
detail. building community.

Enclos Corp - 5
Structural Glass
Facades and Enclosures

Cable Nets Cable Trusses

A new facade technology has emerged

over the past three decades driven by
the pursuit of transparency in architec-
ture among leading international build-
ing designers.

This new technology has evolved

primarily in long-span applications of
approximately 20 feet and over, and can
be categorized by the various structural
systems employed as support. New
glazing systems are also a part of this
emergent technology, with the vari-
ous point-fixed systems finding most
frequent use.
Frei Otto developed and popularized Another minimalist structural system
Recognizing the importance of struc- cable nets as a structural system in the is that of cable trusses. While cable
tural glass facade technology, Enclos 1960s and 70s. Architect Helmut Jahn trusses can vary widely in both truss
took action to acquire the technology with engineering firm Schlaich Berger- design and configuration with vertical,
and expertise required to play a leader- mann applied the technology in a most overhead, vaulted and domed forms
ship role in implementing and further innovative manner as a flat cable net easily achieved, the trusses themselves
developing this innovative technology supported glass facade for the Kempin- are most often characterized by spread-
in the US marketplace. As a result, we ski Hotel in Munich, circa 1992, fueling er strut elements representing the only
are now providing complete in-house widespread interest in this structural compression members in the struc-
services for both the curtainwall and form in glass facade applications. tural system. As with cable nets, these
structural glass facade areas of the systems rely on the pre-tensioning of
building skin, all as a single-source Cable nets represent the ultimate in truss elements to provide stability, and
package backed by the deep technical elegant minimalist structural systems thus benefit significantly from the early
and financial resources of a national and can provide optimum transparency involvement of the facade design/build
specialty contractor. when the effect of a sheer glass mem- team.
brane is desired. The glass is supported
Characteristics of structural glass fa- by a net geometry of pre-tensioned
cade technology include: highly crafted cables. Designs can be flat, or the net
and exposed structural systems with can be pulled into double-curvature. A
long-spanning capacity, integration clamping component locks the cables
of structure and form, simultaneous together at their vertices and fixes the
dematerialization and celebration of glass to the net. Large pre-stress loads
structure, complex geometries, exten- in the net structures require the early
sive use of tensile elements, specialized involvement of the facade design/build
materials and processes, an integration team with the building engineer.
of structure and cladding system, and
a complex array of design variables
ranging from facade transparency to
thermal performance and bomb blast
considerations.

6 - Skylight
Grid Shells Glass Fin Systems All-Glass Systems

Grid Shell structural systems are This is the earliest form of structural Glass facades are comprised of a glass
another means to minimize the visual glass facade dating back to the 1950s system supported by some form of
mass of structure. Configurations can and the French Hahn system used at structural system (except glass fin-
be vaulted, domed and double-curved. the Maison de la Radio in Paris in 1953. supported walls in which the glass is
Systems can be welded, bolt-up, Here 2-story glass plates were suspend- hung and braced laterally with fins). As
or some combination of each. Grid ed and laterally stiffened by the use of the pursuit of transparency is a frequent
shell structures with integrated cable glass fins set perpendicular to the plates reason for the use of structural glass
bracing can produce a highly efficient at the vertical joints between them. This facade technology, point-fixed (frame-
structure with a refined aesthetic. technology was popularized by the Willis less) glass systems are most often
Cable pre-tensioning may be required Faber & Dumas Building, Ipswich, Eng- integrated into the facade design. These
on such systems. Grid shells can be land circa 1972. In this curving facade can be systems where the glass is
used in vertical and overhead appli- designed by Foster Associates, multiple perforated and bolted or non-perforated
cations, as well as to form complete plates of reflective glass are suspended and clamped. Such systems typically
building enclosures. to provide one of the first examples of provide optimum transparency and de-
an entire building facade in frameless sign elegance. However, the structural
glass. This project inspired a diffusion of systems employed in structural glass
glass fin technology in numerous appli- facades can easily be designed to ac-
cations throughout Europe and America commodate any type of glass system. In
starting in the 1970s and continuing some applications framed systems can
today. Glass fin-supported facades still provide certain practical or economical
represent one of the most transparent advantage.
forms of structural glass facades and an
economical solution especially at lower Enclos is capable of developing and
spans. providing any type of custom glazing
system for structural glass facade ap-
Enclos provides custom fin-supported plications.
facade designs for any application.

Enclos Corp - 7
A Vocabulary of
Transparency;
Castings, Cables and
Machined Fittings

Cables

In addition to the glass and structural

systems that comprise structural glass
facade technology are the components
that in turn comprise these systems,
components quite unlike those typically
used in exterior wall systems. The use
of tensile elements in the form of steel
cables and rods is a primary design
strategy to dematerialize the structure
and enhance the transparency of a
facade design. Compression elements
are frequently minimized or eliminated,
and where present are crafted from cast
and machined components in an elegant
expression of exposed structure. The
fittings and components that tie these Bridge builder and engineer John A.
structural members together are simi- Roebling first manufactured wire rope in
larly crafted. An entirely different set of America in the 1840’s. These materi-
material and process considerations als ultimately found their way into the
come into play. vernacular of architecture through such
stunning works as Mathew Nowicki’s
The Enclos design team has mastered Dorton Arena of 1952 and the Ingalls
these materials and processes as a Rink at Yale University of 1958 designed
necessary prerequisite to their ap- by Eero Saarinen. Structural glass
propriate application in component facade technology has embraced these
design. We can develop and provide tensile materials as a means to mini-
custom designs of remarkable diversity mize the structural profile of the support
in response to your particular project system. Wire rope composition, material
needs. Where appropriate, we can also type, finish, and end terminations are all
source off-the-shelf components from a important considerations in specifying
variety of suppliers, all carefully qualified these materials, which are available from
to Enclos Corp standards and subject a relatively limited number of manufac-
to our uncompromising quality assur- turers and specialty fabricators. Enclos
ance program. All this, from concept Corp has put many of these manufac-
design through installation, as part of a turers through its rigorous qualification
single-source package from the largest process, resulting in several exceptional
national specialist in structural glass vendor/partners that have successfully
facade technology. provided materials on various structural
glass facade projects that we have com-
pleted in recent years.

8 - Skylight
Rods Castings Machined Components

The use of steel rods as a substitute for Casting is an ancient process with a In many respects, structural glass
cable in the design of structural glass longtime role in the construction indus- facade technology is more closely akin
facades was a practice borrowed from try, including the naming of a “cast- to the automotive industry than it is to
the yacht racing industry, and popular- iron architecture” during the industrial conventional construction. Spider fit-
ized in the Louvre Pyramid designed by revolution resulting from a dramatic tings are about as far from the brick as
IM Pei. The rods are most commonly increase in the availability of low cost a building component can be. Structural
fabricated from ASTM A316 stainless cast materials. Castings were much glass facades are highly engineered
steel because of the material’s combina- later used to spectacular affect in the structures built to very high tolerances.
tion of strength and corrosion resis- gerberettes and other components for There is also an important visual aspect
tance. In high load applications or when the Center Pompidou by architects Rog- to the components because of their
super thin profiles are desired, there are ers and Piano. The casting of structural use in exposed structural systems.
other higher strength stainless options. components however, demands a high Despite a widespread pursuit of facade
The rod terminations are often custom level expertise in both the design and transparency, many designers choose
designed and can be quite refined, with fabrication process. Cast nodes for the to express this exposed structure in
the intent of minimizing or eliminat- space frame structure on the Javits dramatic fashion, sometimes even at the
ing any exposed threads, turnbuckle Convention Center in New York were expense of ultimate transparency. These
or other tensioning mechanism. Rod famously discovered during construc- factors and considerations make the
fabrication typically involves slipping tion to contain cracks, requiring the use of machined components a frequent
the end fittings over the rod and upset- disassembly of nearly half the structure and effective choice. We design custom
ting the rod ends through a process and a project delay of nearly two years. components or specify off-the-shelf
called cold-heading. Alternately, equally While most of the castings utilized in parts as appropriate, and source both
elegant threaded fittings have also been structural glass facades are glass-fixing from our network of vendor/partners.
developed. Depending upon the design components of stainless steel, such as
of the structure, cable systems can have the “spider” fittings that attaché point-
significant advantages over rod sys- fixed glass to the supporting structure,
tems, particularly with respect to cost. many options exist in both material and
However, some feel that the refined process depending upon the component
appearance of a rod system is worth a size, design and application.
premium cost.

Enclos Corp - 9
Research &
Development

Thermal Performance

Enclos Corp is known for provid-

ing technically superior exterior wall
systems at competitive prices, and in
fact this is one of our core commitments
to our clients. We achieve this through
a progressive ongoing program of re-
search and development. This program
has resulted in continuous refinements
to our core systems, as well as yield-
ing new system designs with improved
performance attributes. The bulk of the
current R&D program falls within the fol-
lowing categories:

Security design and blast-resistant fa-

cade technology is a particular expertise Rising energy costs and the energy per-
of Enclos, demonstrated by a portfolio formance of the nation’s buildings have
of completed projects meeting the become predominant concerns. While
most demanding security requirements, the thermal performance of a curtainwall
including many federal courthouse building skin is primarily dictated by the
projects. Security Design remains an thermal properties of the glass makeup
ongoing focus of our R&D program. or panel cladding material, Enclos has
focused its R&D effort on the perfor-
Our security and blast-resistant technol- mance of the framing system to both
ogy is discussed in the pages immedi- determine behavior and identify oppor-
ately following. tunities for improvement. The result has
been thermal enhancements to existing
systems as well as the development of
premium systems with improved thermal
performance.

In addition, our project work includes

innovative dual-skin facades and cavity
wall systems featuring the state-of-
the-art in energy performance. We
have in-house mechanical engineering
capability and computational fluid dy-
namic analytical technology to assist in
the design of these advanced wall and
enclosure systems.

10 - Skylight
Acoustical Performance New System Development Testing and Prototyping

We have recently crossed an important Enclos facade and curtainwall systems Testing is a key component of any R&D
threshold in the evolution of civiliza- are of known and proven performance, program. Testing activities as part of the
tion. For the first time in history, the having been tried and tested in numer- Enclos program have involved explosive
majority of earth’s people reside within ous mockups and hundreds of custom testing on blast-resistant designs, struc-
our urban cities. This is reflected in the building applications over many years. tural testing to hurricane wind loads,
increasing density of these urban areas They have consistently conformed to re- acoustical and thermal testing, and
and evidenced by the many residential quired specifications for water penetra- many others. In addition, most of our
tower projects which have sprung up in tion and air infiltration, as well as other custom curtainwall designs for particular
cities around the world. Along with the demanding specification requirements. building projects require some program
increasing density has come escalat- of mockup testing, and we have per-
ing noise pollution. These factors However, increasing urban density, ris- formed many dozens of such tests over
have combined to produce a growing ing fuel costs, and concerns over rapid the years.
concern among developers, architects climate change are resulting in escalat-
and building occupants regarding ing demands on the performance of the Enclos Corp has its own dedicated in-
the acoustical performance of urban building skin. Anticipating this trend, house test facility augmented by several
habitats. Enclos has been hard at work develop- major certified testing facilities across
ing new facade and curtainwall systems the nation. The later facilities are used
In recognition of this, Enclos launched with improved behavior in all key areas when special capabilities are needed
an R&D initiative intended to identify the of performance. We are confident that and independent confirmation of perfor-
key variables in the acoustical perfor- we can and will continue to provide mance is a requirement.
mance of its facade and curtainwall technically superior systems at competi-
systems. The program involved testing tive prices.
inter-story as well as outside-to-inside
acoustical behavior, and has resulted
in refinements to basic systems as well
as new premium curtainwall framing
systems with superior acoustical perfor-
mance.

Enclos Corp - 11
51 Louisiana
Washington, DC

owner Dweck Properties

architect Rogers Stirk Harbour +
Partners / HKS
gc Clark Construction Group
facade consultant Curtainwall Design
Consulting
completion 2009
program 10-story glass enclosed atrium
building type office
facade design/build program for entire
atrium enclosure
description a 10-story glass enclosed
atrium with exposed structure creates a
dramatic public space and ties 2 adja-
cent office buildings together

1
51 Louisiana and 300 New Jersey Av- atrium structure, supports a trapezoidal
enue is a state-of-the-art office building flying roof of glass, and carries exposed
project in Washington, D.C., located just HVAC and other building system com-
one block from the U.S. Capitol. The ponents. Multiple levels of skybridges
project includes the construction of a tie the complex together. As all structure
new glass-enclosed office building that and systems are exposed, the highest
will serve as an extension of two exist- level of craftsmanship was required for
ing office buildings, all connected by the every aspect of the project. The project
new centerpiece atrium. is the first office building by London-
based Rogers Stirk Harbour + Partners
Enclos was responsible for the chal- and Pritzker Prize winning Principal
lenging facade program that encloses Richard Rogers.
the new 10-story atrium space. A yellow
tree-like steel construct provides the

12 - Skylight
 1 The vertical wall is 90’ tall by 40’ wide
2 Stainless steel tension rods tie back to
primary structure to stabilize the wall
structure
3,4 The yellow truss supports the skylight roof
2

LEED Silver certification is expected for the

project, and its sustainable features include
a green roof and treatment of water from
the atrium in the existing building’s storm-
water processing system.
4

Enclos Corp - 13
51 Louisiana
Washington, DC

The wall that forms the entry to the new row design covering 12,500 square
complex climbs vertically over 90 feet feet in plan area. The glass module is
and then slopes back nearly 14 feet approximately 4 feet by 12 feet and
to join the glass roof. The entire wall incorporates a full perimeter supported
is hung from above, with a series of insulated-laminated glass panel with a
suspended horizontal trusses providing ceramic frit and low-e coating.
the minimal structure. Point fixings tie
the glass to the trusses at the end of The glass enclosure actually ties
2-foot truss armatures. Spring connec- together three separate buildings of 1 top of wall detail at slope
tions at the base and sides of the wall different construction and constructed 2 wall/skylight transition
accommodate movement under design during different time periods when 3 skylight plan with wind load map
loading. building practices and code require- 4 top of wall truss detail
ments varied. The result is considerably 5 3d model view
6-8 interior photos
The skylight is a low ridge and fur- different movement behavior between

14 - Skylight
 5

them during design loading. Of course, commodate these movements with an commodate it. Spring mechanisms were
even identical buildings will not move in efficient and minimal structure. A high designed into the structural system that
phase when subject to identical loading level of transparency combined with a allows the structure to absorb relatively
conditions. The Enclos team built a 3-D minimal but expressive structure was high deflections and relative build-
digital model of the glass enclosure particularly important in the design of ing movement without inducing high
and surrounding buildings as a tool for the glass wall. compressive stresses into the structural
studying the relative building movement. components. A network of stainless
The intent was to develop a design for Rather than designing to limit move- steel rods are used to stabilize the top
the roof and wall that could fully ac- ment, the structure is designed to ac- of the wall.

6 7 8

Enclos Corp - 15
 Clark Construction, with 40 subcontrac-
tors and an average of 200 site workers
each day, constructed the project over
51 Louisiana a 3-year period. Space was very limited
on the dense urban site, and office
Washington, DC buildings immediately adjacent to the
site were operational throughout con-
struction. An Enclos project manage-
ment and site operations team worked
closely with Clark and other subcontrac-
tors to assure optimum site logistics and
minimal disruption to nearby building
occupants.

Key to the success of the complex

installation of the glass enclosure was
a system for the glass wall and sky-
light that embraced the requirements
for installation in its veried design. The
skylight roof system, for example, was
constructed in fully glazed subassem-
blies off-site. The skylight system was
designed with a split-beam structural
element running in the primary spanning
direction. Ladder frames were assem-
bled under factory-controlled condi-
tions into 12-foot wide sections up to
48 feet in length. The finished sections
were stacked on flatbed semi-trailers
and shipped to the site on a just-in-time

1 2 3

basis to minimize site inventory and

storage space. The sections were lifted
from the trailer by an overhead crane
and set and bolted into position. Crane
setting positions were carefully mapped
and their availability coordinated with
the other trades.

The off-site concentration of the assem-

bly work and detailed installation logis-
tics planning improved product quality,
speeded assembly and installation, and
minimized disruption to this challenging
building site.

16 - Skylight
4

5 6 7

1 trough skylight detail

2 ridge skylight detail
3 skylight detail with wall bracing rods
4 skylight plan with crane lift mapping
5 wall detail at portal frame
6 wall detail at edge
7 spring at portal frame
8 detail drawing of spring at entry portal
frame 8

Enclos Corp - 17
Station Place
Securities &
Exchange Commission
Washington, D.C.

developer Second Street Holdings LLC,

Louis Dreyfus Property Group Inc
architect Kevin Roche John Dinkeloo &
Associates
gc Tompkins Builders
completion 2004
program lobby wall: 90 feet high and 60
feet wide; skylight: 55 feet long and 60
feet wide
building type government
structure double curve anticlastic cable
net made of 20 mm cables clamped via
stainless steel cast nodes. Supported by
the perimeter concrete structure and an
intermediate steel delta truss
glass face glass—Viracon, 1 1⁄4 inch to-
tal thickness, five-foot by five-foot panel
size insulating glass consists of 1⁄4
inch heat-strengthened clear glass with
low-emissivity coating on the second
surface, a shading coefficient of 0.43,
winter U-value of 0.48 and summer
U-value of 0.55; 1⁄2 inch air space and
silver spacer bar; inner panel consists
of 1⁄2 inch laminated glass consisting of
3⁄16 inch clear heat-strengthened glass,
1⁄16 inch polyvinyl butyl and 1⁄4 inch
clear heat strengthened glass.
1
skylight— 15⁄16 inch total thickness
Glass-clad cable-net structures are fast columns at the top of the wall and pro-
consisting of: 1⁄4 inch clear tempered
evolving in the United States as one of vides support at the intersection of the
glass with low-e coating on the second
the dominant forms of high-transparen- wall and skylight. The truss also acts as
surface, a shading coefficient of 0.33, a
cy facade technology. a load transfer and stabilizing element
winter U-value of 0.29 and a summer U-
for the adjacent building towers. The
value of 0.29; ceramic frit on the second
The lobby area of SEC is enclosed with wall net comprises 15 rows of hori-
surface, with Viracon Pattern 5005 and
a cable-net supported 60-by-90-foot zontal cables and 12 rows of vertical
frit color V912-LF (white); 1⁄2 inch air
glass wall and a 60-by-60-foot skylight. cables and the skylight net comprises
space and silver spacer bar; 1⁄2 inch
The combined surface area is approxi- 12 longitudinal and 10 transverse
laminated glass consisting of 1⁄4 inch
mately 9,000 square feet. The structure cables. The vertical cables of the net
clear tempered glass, 1⁄16 inch PVB and
comprises 28-millimeter stainless steel wall align with the longitudinal cables of
1⁄4 inch clear tempered glass for the
cables and clamp fittings or nodes. A the skylight.
inner panels.
60-foot-long double curved triangular
truss spans the two concrete super

18 - Skylight
The vertical and horizontal cables are
clamped at their intersections with
custom stainless steel node assemblies,
which in turn receive the hardware by
which the glass is fixed to the net. The
slight radius the wall structure follows
in plan provides the curvature in the
horizontal direction. Opposing curvature
in the vertical direction is provided by
embedded cable connections within the
concrete super columns. The opposing
curvatures give the cable net its saddle
shaped surface and stability.

In practice, cable-net structures are re-

markably resilient and forgiving as they
are designed to move. They can deform
many times the deflection criteria of
conventional steel or aluminum struc-
tures without permanent deformation or
2
failure. Deflections in the flat nets can
equal 2 feet under wind load in a 100
foot span. Contrary to being a problem,
this allows them the flexibility to best
withstand the extraordinary loadings
resulting from seismic events or bomb
blasts. As with all emergent building
technology, cable nets number among
the highest priced facades in the mar-
ketplace, due largely to development
costs. However, the systems are rela-
tively material-efficient and very simple,
and market pricing drops rapidly. In
efficiently designed structures, with the
dissemination of assembly and installa-
tion know-how, look for cable-net tech-
nology to become competitive in price,
resulting in widespread application.

1 90 x 60 foot entry wall

2 Interior view of the skylight from the
lobby
3 Top view of the skylight
4 Isometric view of the cable net wall
and skylight
4

Enclos Corp - 19
 Node detail

Station Place
Securities &
Exchange Commission
Washington, D.C.

Enclos has developed various glass

systems for application on its cable net
designs, including point-fixed drilled
and non-drilled systems and panel- Glazing Frame
ized systems. For the SEC net, Enclos
has developed an innovative unitized
glass-framing system that can be bolted
directly to a modified cable-net node as-
sembly. The system avoids the premium
cost associated with point-fixed glass
systems and allows for competitive
domestic glass supply.

The anticlastic geometry will result in a

major mitigation in the deflection of the
cable nets. However, this feature results
in a warped surface that cannot be eas-
ily clad with the planar glass.

Double curved glass is expansive and

impractical for insulated glass and cold
bends have limitation on the glass size
and the preload warpage.

Analysis of relative amount of warp in glass panels; left geometry hyperbolic paraboloid; middle geometry hybrid; right geometry torus.

20 - Skylight
 In this project Enclos first optimized the
cable-net geometry to achieve minimum
distortion while maintaining enough
curvature to control the skylight and wall
deflections.

The result is a hybrid geometry extract-

ed from the surface of a torus.

The remaining warp is then concealed

in the interstitial space of the thin alumi-
num frame.

Installation Sequence
1 In order to achieve the proper shape 5
in the double-curved nets, the clamps
must be accurately positioned on the
net, and the tensioning of the net must
be accomplished with all cables, vertical
and horizontal, simultaneously. This re-
quires rigorous methodology frequently
involving sophisticated hydraulic jacking
gear. Enclos utilizes special survey
techniques to map the position of each
node. Compensating adjustments in
the tensioning of the net can then be
computed and implemented. The trick,
then, with the cable-net structures is in
the tension: first, determining appropri-
ate theoretical cable pre-tensions with
2 respect to boundary conditions, so as 6
to yield the most efficient shape of the
net. The following Sequence was used
at SEC:

1 assemble the net the factory and

attach cables and nodes in a the hori-
zontal position allowing compensation
for final tensioning
2 pretention the net using perimeter hy-
draulic jacks attached to a temporary
space frame with similar stiffness as
the actual structure
3 adjust the nodes to their final position
3 7
using accurate laser measurements
and clamp the node with the required
torque values
4 wrap the cables and nodes in plastic
covering and de-tension the net and
roll the net around a spool
5 transport the spool to the to the site
6 erect the supporting structure includ-
ing the delta truss and assemble the
perimeter jacking system at the sup-
port locations
7 drape the net and attach to the perim-
eter jacking system and the delta truss
8 tension the net to the final position
utilizing all of the jacks simultaneously
and check node locations; install glass
4 8

Enclos Corp - 21
Strength of Geometry

Performance yields form The general approach initiates by as-

signing an initial approximate shape for
Developing the geometry for a curved the geometry which assigns the grid
cable net structure is much a part of the size and the boundary curves. Usually
art of this technology. The geometry for this initial shape is flat. Then a preten-
a project like SEC is a critical issue, as tion force or force density (force / unit
cable net behavior is extremely sensitive length) is assigned to the cables. Then
to relatively minor changes in bound- the an iterative nonlinear approach is
ary support locations and pre-tension used to converge to the final position.
forces. The final shape of the net must
be determined as a function of perfor- If the assigned force in the two direc-
mance. tions is specified to be the same and
constant the resulting geometry is a
The goal is to control deflections, opti- minimum surface.
mize stress distribution, and minimize
pre-tension requirements and resulting In-service analysis
reaction loads to the boundary struc-
tures. Subtle adjustments in the shape Upon completion of the form finding the
of the net can significantly decrease super imposed loads are applied to the
required cable pre-tensions as well as cable net. The vector loads are applied
the forces in the cables under load. In at the nodal points and the net deflec-
addition, a coordinated manipulation of tions and cable forces are computed.
the net geometry can consolidate the
variation in glass panel sizes required to Because cable movements are relatively
glaze the net. large, the applied loads cannot be as-
Hyperbolic-Paraboloid Geometry sumed to remain in the same point of
Without this design coordination it is application. Further more it is possible
possible that a different size may be that some cable elements will be relaxed
required for each grid panel of the net. (void of any tension) in certain load
This will significantly increase cost both combinations. These constraints require
with respect to the glass itself as well as a non-linear approach to the solution of
with its handling and installation. Poor Form-finding analysis incorporating both the geo-
net geometry can also result in unnec- metrical and material effects.
essarily excessive warping in the glass The first step in the design of double
cladding, as discussed previously. curve cable nets is the process of find- The main factor in controlling the forces
ing the equilibrium position of the net and deflections of the cable nets is the
The unique geometry developed for the under pretension forces. The preten- sag ratio. The curve following shows the
SEC project provided two significant sion geometry is a function of a number sensitivity of the peal deflection in as a
advantages: it eliminated any permanent of parameters, including the boundary function of sag ratio (prescribed bound-
warp in the individual glass panels, and condition profiles, maximum reaction ary curvature / boundary length).
it allowed for each row of glass to be allowed at these boundaries, the maxi-
repeated rather than each panel being a mum allowable deflection during service
different size and shape. loads, and the cladding constraints im-
posed by the planar nature of the glass.

22 - Skylight
 Effect of sag ratio (ratio of prescribed
boundary curvature to the boundary span)
on the deflection of double curve cable wall
and maximum cable forces.

Wall deflection as a function of wind speed

for conventional glass walls , flat cable
nets and double curve cable nets.

Enclos Corp - 23
San Jose Civic Center

owner City of San Jose

architect Richard Meier & Partners
Architects
gc Turner Construction Company /
Devcon Construction
facade consultant Curtainwall Design
Consulting
completion 2005
program 18-story tower, freestanding
10-story dome-capped rotunda, 100 ft
dome; 550,000 sqft total
building type civic
facade design/assist and design/build
program included cable truss system
with point-fixed glass for rotunda and
dome at 21,000 sqft; tower facade is
custom metal and glass unitized cur-
tainwall system with louvers, sunshades
and operable windows
dome structure comprised of 12 bays,
each 26 feet wide spanning between
AESS structural steel arched beams
rising to a height of 108 feet; exte-
rior stainless steel cable truss system
spanning between arched steel beams,
with stainless steel spreaders as sole
compression element
glass point-fixed system with custom
spider to provide adequate movement to
accommodate requirements of California
Building Code; rotunda glass is point-
fixed and perforated at the corners,
tempered and laminated, with a high
performance low-e coating; large panels
required in the barrel area approximately
10 feet high by 6 feet wide, comprised
of 3/8-.060-3/8 inch glass and laminate;
smaller dome panels are 3/8-.060-1/4
inch; rotunda glass imported from spe-
cialty Spanish glass fabricator Cricursa

24 - Skylight
testing extensive mockup testing of
dome glass system: including seismic,
water and air infiltration
installation strategy cable truss system
required pre-tensioning to forces rang-
ing up to 22,000 lbs; a detailed installa-
tion method statement was developed
to facilitate assembly and installation;
hydraulic equipment was used to
achieve prestress forces

Richard Meier & Partners Architects

is well known for uncompromisingly
modernist designs: formal and monu-
mental with light-filled spaces, and
sweeping expanses of metal, stone and
glass. Enclos has collaborated with
Meier on many past projects, including
the sprawling Getty Center art complex
in Los Angeles. The San Jose Civic
Center includes a slim 18-story metal
and glass tower housing City Hall, a
3-story council wing, and features an
adjacent public plaza dominated by a
free-standing dome topping a 10-story
glass rotunda.

At 100 feet, the rotunda’s diameter sur-

passes that of the U.S. Capitol building,
and it is virtually all glass. The transpar-
ency and openness are intended to re-
flect the democratic form of government
in which the United States prides itself.

Enclos Corp provided pre-bid services

to the architect. Michael Palladino,
partner with Richard Meier and lead
architect on the San Jose project, laid
out the program for the dome. The
dome capped rotunda heralded an old
tradition of such building form in public
buildings, but he wanted to combine
this aspect with the use of state-of-the-
art technology, “beyond any skylight
ever built.” Palladino wanted to “take
the next step in dome design” with a
highly transparent all glass structure,
using a filigree tension based support
system. The decision was made to bid
the tower curtainwall and the rotunda as
a single design/build facade package.
With Enclos providing design-assist ser-
vices, a concept was represented in the
architect’s drawings and a performance

Enclos Corp - 25
 quired in one direction only. Compound dating the large inelastic building drifts
curved glass to provide true curvature required by the new California Building
to the dome surface was considered, Code in areas of high seismic activity.
San Jose Civic Center but ultimately rejected for budgetary Conventional point-fixed systems can
reasons, so the dome surface is faceted be inadequate in these applications,
with flat panel shapes hung from the thus Enclos developed a new sys-
cable trusses. The rotunda enclosure is tem involving a custom spider design
unusual in its use of an exterior struc- capable of providing for large in-plane
tural system to support the glass. Stain- movement. The system allows for up to
less steel cable trusses span horizon- 3 inches of in-plane movement at each
tally between structural steel columns in fixing. A custom spider component was
the rotunda and the arched beams that required to accommodate this move-
form the dome. The sole compression ment. Enclos developed a custom spi-
elements in the system are the stainless der that is investment cast of a special
steel spreaders that, along with ap- heat-treated stainless steel alloy with
proximately 2.5 miles of stainless steel mechanical properties well beyond the
specification was included in the project cable, comprise the trusses. Spider-type 316 stainless alloy typical to conven-
tender documents. Enclos was ultimate- fittings attach to the inside end of the tional spider fittings.
ly the successful tender for curtainwall spreaders, providing the point fixings
contractor. that secure the glass. An extensive testing and mockup pro-
gram was undertaken for the spiders
Curved glass is used in the lower barrel Arguably the most challenging design and dome structure. Additional informa-
of the rotunda, with simple curvature re- aspect of this project was accommo- tion is available upon request.

An extensive testing and mockup program

was undertaken for the spiders and
dome structure. Additional information
is available on request.
1

26 - Skylight
 2

1 Exploded view of the skylight dome

2 Diagram of typical cable truss
3,4 Inelastic seismic movement of the
spider during mockup testing
5 Glass movement during a seismic
event

5 4

Enclos Corp - 27
Casting Process for 1 2
Spider Fittings
The investment casting process is a
8 7
complex, multi-step process. The basic
steps are illustrated here.

28 - Skylight
 1 Wax injection
Wax replicas of the desired castings
are produced by injection molding.
these replicas are called patterns.
2 Assembly
The patterns are attached to a central
wax stick, called a sprue, to form a
casting cluster or assembly.
3 4 3 Shell building
The shell is built by immersing the
assembly in a liquid ceramic slurry and
then into a bed of extremely fine sand.
6 5 up to eight layers may be applied in
this manner.
4 Dewax
Once the ceramic is dry, the wax is
melted out, creating a negative impres-
sion of the assembly within the shell.
5 Casting
In the conventional process, the shell
is filled with molten metal by gravity
pouring. as the metal cools, the parts
and gates, sprue and pouring cup
become one solid casting.
6 Cut-off
The parts are cut away from the central
sprue using a high speed friction saw.
7 Knockout
When the metal has cooled and solidi-
fied, the ceramic shell is broken off by
vibration or water blasting.
8 Finished castings
After minor finishing operations, the
metal castings—identical to the origi-
nal wax patterns—are complete.

Enclos Corp - 29
 owner CenterPoint Properties glass exterior low-iron insulated lami-
nated with custom frit for roof glass,
architect Murphy/Jahn
insulated glass with low-e coating for
Shure Corporate engineer Peller & Associates glass fin walls, laminated glass fins, all
gc Harbour Contractors, Inc. glass point-fixed non-perforated, sup-
Headquarters plied by Eckelt; interior glass low-iron
completion 2000
Chicago tempered monolithic
program 7-story; 65,000 sqft description this building rises like a
building type office jewel box above its neighbors in a Chi-
cago suburb
facade design/build program including
custom vaulted glass roof and glass fin
wall of over 30,000 sqft; interior glass
elevator enclosure, handrail, stairs,
wash basins, ceilings

30 - Skylight
In granting an AIA Design Excellence
Award (Chicago, 2005), jurors agreed
that this building is at the leading edge
of design and technology, in the best
Chicago tradition. The seven-story box
is overlaid with triangular screens that
form loggias to the street and serve as
projection screens for the company’s
logo. The exterior wall is a single-shell,
insulating glass facade between the
slab edges. Concrete ceilings are ex-
posed, with mechanical systems placed
beneath raised floors. The interior is
organized around a full-height atrium
with three glass elevators and topped
by an innovative glass roof. At the top
two levels the atrium connects to a
two-story light-flooded showroom for the
company’s products.
2 3

1 View of glass roof and handrails, with

glass elevator core and wall beyond.
2 Glass roof at intersection of vertical fin
wall.
3 Retainer plates hold the 7’ x 5’ glass
panels at four locations along the
perimeter.
4 Section drawing showing roof truss
design.
5 A four-way armature at the cross sec-
tion of cable trusses and glass fins
supports the glass panels.

Enclos Corp - 31
Shure Corporate
Headquarters
Chicago

Design/build and engineer-of-record

services were provided for a portion of
the project, including a highly innovative
glass roof and glass fin walls totaling
over 30,000 square feet. Custom roof
trusses were fabricated and rigged
in factory, then installed on the roof
using a rolling gantry. The roof struc-
tural system incorporates a laminated
glass beam element and intermittent
cable trusses to lighten the structural 1
profile. Roof cladding glass is insulated
laminated panels with an offset ceramic
frit on two interior surfaces. The Enclos
design team developed an innovative
point-fixing system utilizing a “pinch-
plate” or clamping spider assembly that
eliminated the need for drilling holes in
the glass, thus providing considerable
savings to the project. Low-iron glass
was used throughout to further enhance
transparency.

Laminated glass fins provide wind load

resistance to the vertical facades, and
integrate the primary entry portals into
the building. A major component of the
scope on this project was interior design
that included floor, ceiling and handrail
glass. The cores for the glass elevators
are enclosed in glass surrounds, and 2
even the elegant fritted glass counter
tops in the lavatories were provided as
part of a comprehensive design/build
program.

3 4

32 - Skylight
Brain Power vs Crane Power

The building site is a primary cost

center in all building projects. Advanced
facade technology concentrates labor
in the factory, providing higher qual-
ity and lower cost. The prefabricated
and pre-finished systems must still be
assembled and erected on the build-
ing site. This fundamental activity must
be anticipated and designed for during
facade design development.

One of the more significant site costs

is typically the equipment expense as-
sociated with the use of a crane to lift
components into place. The crane and
operator costs can be significant on
facade projects with constrained site
conditions, which is frequently the case.
5
The rectangular plan of this glass sky-
light lent itself to an installation method
facilitated by a simple gantry crane
mounted on rails parallel to the longitu-
dinal axis of the skylight.

The gantry was designed along with

the skylight roof and fabricated by the
truss fabricator. Instead of a large crane
through out the installation process, a
small crane was required for only a few
days to lift the gantry and materials to
the roof, and to remove the gantry on
completion the installation. This strategy
provided significant savings to the
owner and made possible the accom-
modation of an accelerated delivery
schedule.

1 Exploded rendering of componentized

spider assembly.
2 Finite element solid modeling was
used to perform stress analysis of the
armatures supporting the glass panels
3 Vertical facade with glass fin support.
4 Glass fins can be used to support
skylights also.
5 A custom gantry was designed and
fabricated to facilitate erection.
6 Roof glass installation in process.
7 Illustrations from the Crystal Palace,
1851 by Joseph Paxton: a source of
inspiration for the installation of the
glass roof.

Enclos Corp - 33
Orlando
International
Airport: Airside 2

1
developer Greater Orlando Aviation
Authority
architect HOK
structural engineer Walter P. Moore
gc Clark Construction Group
completion 2000
program 3-storys; 305,000 sqft
building type airport
facade a centralized glass skylight and
custom glass fin wall create a highly
transparent hub
glass insulated, point fixed
description three dramatic tension truss
skylight systems act as the focal point
of Florida’s busiest airport

The HOK aviation design team wanted into the compression members of the
to modernize an existing hub design cable trusses.
strategy for the new Airside 2 Termi-
nal at Orlando International Airport. A The Airport General Tram enclosure
conventional heavy steel truss backer makes use of the ASI Vanderbilt LS
structure supporting boxy aluminum system, the long span version of this el-
framed skylights and curtain wall egant and highly economical glass wall
systems was to be avoided. Modifica- structural system comprised of steel
tions to the building shell involved the tension trusses and integrated glazing
application of cutting edge design and system. In this custom application the
building technology. trusses were curved to provide a radius
section to the glass wall enclosure.
At the hub itself, lightweight stainless
steel cable trusses support 3 ellipti- There is lightness to the resulting enclo-
cal long-span skylights. The skylight sure enhanced by the effect of transpar-
system utilizes an integrated cladding ency achieved with the tension based
strategy comprised of insulated, point- structural systems, and the systems
supported glass with stainless steel detail and use of material are compli-
fittings and hardware that tie directly mentary to the contextual aeronautical

34 - Skylight
3
technology. The architect’s design
goals were thus achieved. However, the
advantages of advanced building tech-
nology do not end with the aesthetic;
the building team provided the owner
with extended warranties covering the
long-term performance of the enclosure
systems and materials.

4
1 skylight plan
2 skylight showing cable trusses span-
ning between perimeter fabricated
steel trusses
3 glass fin spanning between cable
trusses
4,5 hydraulic jacking system for tensioning
cable trusses
6 glass fin and spider attachment detail
7 typical glass truss drawing
5

6 7

Enclos Corp - 35
Lloyd D. George United
States Courthouse
Las Vegas

owner General Services Administration

architect Dworsky Associates
engineer Martin & Peltyn
gc JA Jones Construction Company 1
facade consultant Curtainwall The Lloyd D. George Federal District The 450,000 square foot L-shaped
Design Consulting / Gordon H. Smith Courthouse is the home for the district facility incorporates a complex facade
Corporation court in Las Vegas, and was the first program. Ceiling heights of 22 feet
federal building built to comply with required long-spanning cladding materi-
blast consultant Hinman Consulting
post-Oklahoma City blast-resistance re- als. Precast wall panels measuring 22
Engineers / Weidlinger Associates
quirements. Following the events of the feet by 10 feet clad much of the exterior.
completion 2002 Oklahoma City Bombing in 1995 and the A dramatic steel and aluminum canopy
program 8-stories; 456,000 sqft attacks upon the World Trade Center in projecting from the top of the building
2001, the federal government mandated shadows the plaza, where a three-story
building type government / federal
an increase in building structure security rotunda serves as the public lobby.
courthouse
measures that have since become in-
facade design/build services for a dustry standards. A 60-foot diameter cable truss support-
complex program of facade elements in- ed glass dome caps the rotunda, also
cluding precast panels, louvered sunroof The innovative systems developed by provided by Enclos in compliance with
panels, aluminum sunscreen panels, Enclos for this project were the first in challenging bomb-blast requirements.
column covers, flat and curved roof the country to be subjected to full-scale The walls facing the plaza are of glass
spandrels, sill panels and a glass-clad testing to verify performance under curtainwall inset into precast frames
cable truss dome blast loading. All systems surpassed the with an integrated louvered sunscreen.
newly created blast security criteria.

2 3

36 - Skylight
1 The facade designs for this courthouse
were the first in the country to be
tested to blast performance criteria,
with testing performed at White Sands
Missile Base.
2 The dome caps the entry lobby of the
courthouse.
3 Stainless steel struts are wrapped dur-
ing installation to protect finish.
4 Articulating spider custom designed
to accommodate the performance
requirements of this dome.
5 3-D rendering of dome with section
diagram at truss.

4
Advanced structural silicone and lami- maintain fundamental integrity and act
nated glass were combined in inventive to mitigate the risk of injury in the event
ways to meet the blast requirements. of an attack.
Testing took place at the Department of
Defense’s Large Blast Thermal Simulator Weidlinger Associates conducted the
in White Sands, New Mexico. blast engineering.

Results showed that in the event of an

explosion the curtain wall panels would

Enclos Corp - 37
Helen and Martin
Kimmel Center NYU
Manhattan

1
owner New York University Seven custom beam elements float in a Facing Washington Square Park at
architect Kevin Roche John Dinkeloo & sea of tension, suspended and stabi- Greenwich Village, the Kimmel Cen-
Associates lized in a net of stainless steel tension ter includes a 1,000 seat theater, the
elements. The tension structure is clad largest performing arts facility south of
engineer Dewhurst Macfarlane and with laminated point-fixed glass creating 42nd Street, and a 600 seat auditorium.
Partners, in association with Goldreich an effective transparency of gem qual- Student club lounges, conference and
Engineering, PC ity. Upon entering the foyer of the New catering hall, music practice space and
gc LF Driscoll Helen and Martin Kimmel Center for Uni- offices complete the building program.
versity Life at NYU, visitors are greeted
completion 2001
by an unusual tensegrity structure creat-
program entry lobby ing the entrance enclosure. The vaulted
enclosure reaches an extraordinary level
building type education
of transparency and dematerialization
glass laminated point-fixed with the primary roof beams seemingly
description the Helen and Martin Kim- floating in mid air. The canopy structure
mel Center is NYU’s center of activity required pre-stressing of the cables to
for its diverse campus of over 50,000 achieve its structural integrity.
students

2 4

38 - Skylight
5 6

1 The tensegrity structure forms the

entry enclosure to the university.
2-4 Point-fixed laminated glass attaches to
spider fittings on the glass beams.
5 Stainless steel anchors for the cable 7
assemblies during installation.
6 Cable and beam assemblies during
prestressing operations.
7 Typical cable truss section.
8 Integration of load transfer plate at
beam end.
9 Glass attachment detail at outside and
inside corner of cable truss.

8 9

Enclos Corp - 39
 Davis Brody Bond was designing a
22-story luxury residential building
located in Manhattan’s Upper East Side
86 Street Canopy neighborhood. The intent was to con-
vey a contemporary, elegant image yet
Manhattan
compliment its more traditional neigh-
bor, and the building’s design featured a
canopy that was entirely unconventional
yet very sophisticated.

At the entrance, — so thin and clean

that passerbys might not even give it a
second glance — is a glass canopy that
cantilevers approximately 20 feet from a
steep pipe in the rear. What makes this 5
developer The Related Companies Inc. 10-foot wide canopy entirely unique is
its lack of steel structure. Instead, the
architect Davis Brody glass beams act as the structural sup-
completion 1997 port carrying most of the load.

building type residential

ASI acted as the design/builder for this
glass laminated, point fixed unique but state of the art structure.
description with an all glass cantilever
canopy at the entrance, the structure
uses a multi-layer glass beam system to
resist the induced stress 1 the canopy cantilevers 20 ft from the
building with no metal support
2 connection detail of glass beam leafs
3 the entire structure was test assem-
bled off-site
5

40 - Skylight
Metropolitan
Museum of Arts
Manhattan

owner City of New York

architect Kevin Roche John Dinkeloo
and Associates
completion 2006
program 2-stories; 30,000 sqft expan-
sion
building type cultural
description A two story atrium with
glass enclosed skylight is the cen-
terpiece for the museum’s Greek and
Roman displays

The Leon Levy and Shelby White Court-

yard doubles the height of the Greek
and Roman Galleries by adding a two-
story structure with historically themed
columns and glass skylight roof. A three
phase renovation doubled facility space
to 60,000 square feet for exhibitions.
The Met Museum now has on perma-
nent display over 90% of their ancient
Greek and Roman collection — half of
which had previously been in storage
— bringing their active display total to
more than 35,000 pieces dating back as
far as 312 A.D.

The architectural expansion feature is a

custom vaulted skylight with a unique
and minimal structure design. The
skylight floods the museum exhibition
space with natural lighting. The pri-
mary structure is a series of rolled steel
arches fabricated to AESS standards.
A secondary aluminum system spans
along and between the arches to sup-
port the glass. The aluminum system
incorporates and integrated gutter. The
system features concealed bolted con-
nections. Glass panels are insulated-
laminated with a low-e coating.

Enclos Corp - 41
Deloitte Building
Costa Mesa

developer Segerstrom
architect Murphy / Jahn
gc Matt Construction
completion 1997
program 15,000 sqft skylight
building type commercial
facade a centralized glass skylight and
custom glass wall create a highly trans-
parent entrance
glass insulated, low-e coating, 70%
ceramic frit, point-fixed
description three dramatic tension truss
skylight systems act as the focal point
of the building entrance
1

1 Vault structure with two lentricular

super cables running along the width
of the vault to resist lateral loads and a
series of king post trusses across the
vault to carry the vertical loads
2 Entrance at base of vault reveals sys-
tem transparency.
3 Cable truss system encloses vault
sides.
4-6 Glass attachment, footing, and cable
connection details.
7 Isometric view of the vaulted structure
and shade wings.
8 Vault and side wall intersection.
2 3

42 - Skylight
4 5 6
These adjacent structures in Costa
Mesa were developed during the 1970’s,
originally as the Imperial Bank Tower. A
late 1990’s renovation included tie-
ing the structures together by utilizing
state-of-the-art facade technologies
to modernize the buildings. The new
glass lobby connects the tower with
the neighboring building to the south,
providing entrances from the east and
west. The overhead and vertical glazed
surfaces on the vaulted structure are
70% opaque fritted glass with low-e
coating, producing a highly transparent
building skin capable of mitigating solar
heat gain.

The lobby enclosure is 120 feet (36.6m)

by 32.5 feet (9.9m) in plan, and located
between a multiple story tower to the
north and a single story building to the
south. Glass panels are supported by 7
structural steel beams and cable truss-
es. Perforations in the glass accom-
modate a bolted connection capable of
up to 5 degrees rotation relative to glass
plane.

Glass fixing is accomplished with

a stainless steel spider component
providing up to 0.3 inches (8mm) per
glass joint shear deflection under wind
or seismic loading. Glass panels are
tempered and laminated, and sealed
with a butt-glazed silicone joint between
the panels. The roof glass has a dark
frit pattern with low-e properties. Glass
complies with the intent of UBC 1994
chapter 24, “Glass and Glazing”. Single
panel deflection is limited to span/50.

Enclos Corp - 43
Marriott Canopy
Manhattan

1
owner Marriott International
The challenge of implementing a sical masonry forms of the existing
architect Perkins Eastman Architects modern entrance canopy on an older facade, to provide a striking and distinc-
completion 2000 building was to balance the historical tive entranceway to the 35-story tower
charm of the original 1920s facade with at Lexington Avenue. The hotel recently
program canopy entrance to a 35-story the contemporary aesthetic desired by completed a $24 million renovation, and
early 20th century tower the architect and owner. The minimal- the new canopy welcomes guests to
building type hospitality ist canopy design was developed as a the Marriott’s 629 rooms and 17 suites.
study in contrast, the ultramodern steel The hotel hosts a variety of NYC events
facade design/build custom steel and
and glass against the arched neoclas- in its 21,000 square foot event space,
glass cable-supported canopy

1 the entrance canopy supports dramatic

architectural lighting
2 plan and elevation drawings
3 the entire structure was test assem-
bled off-site
4 the custom catenary cable fittings be-
ing assembled
5,6 stainless steel machined fittings
7 view of the canopy from the sidewalk

44 - Skylight
3 4
convenient because of its close proxim- structure. The suspended frame sup- to dramatic effect during the evening
ity to Central Park, Rockefeller Center, ports a glass “shell” that is comprised hours.
Broadway theaters and 5th Avenue’s of laminated glass panels that appear to
retail district. The hotel is readily ac- float between the Corinthian columns of Interfacing a new cable-supported
cessible from Grand Central and Penn the existing building. Suspended beam structure with an existing building with
Stations, the subway, and NYC’s three elements incorporate a glass fin at their a masonry facade is an art form rooted
major aviation hubs. outboard tip in a finger-nail like fashion in fine craftsmanship. The installation of
to further minimize the structural profile. the structure required scaffolding over
The inspiration for the canopy derived the entire sidewalk and entrance area to
from the remarkable iron and glass can- The steel structure was fabricated and the hotel to create a work platform for
opies of late 19th Century Paris. Enclos test assembled off-site to assure fit-up the Enclos installation crew. Penetra-
designers worked closely with the ar- in the field, where a narrow window for tions were carefully cut through the
chitect to develop a concept that would canopy installation allowed no room for masonry facade to reach to steel struc-
meet the aesthetic and pragmatic goals error. Custom stainless steel cable and ture concealed within. Anchor assem-
of this project. The primary structure fittings were used throughout. The tem- blies were designed to facilitate quick
is a fabricated and painted steel frame pered and laminated glass panels are and easy assembly of the structural
with a novel support system of upper tied to the structure by stainless steel components. The canopy was ultimately
and lower stainless steel catenary ca- point fixings. Architectural lighting is completed on schedule and with only
bles that tie back to the existing building supported from the structure and used minimal disruption to hotel operations.

5 6 7

Enclos Corp - 45
The Glass Umbrella
Culver City, CA

architect Eric Owen Moss

glass fabricator California Glass
Bending
description 17 glass panels, each
unique, each slumped to a highly vari-
able double-curvature, point supported
from a tubular frame by custom fixings;
the glass panel edges overlap in plan;
glass cascades over an exterior stairway
intended to act as a mini-ampitheater.
structure custom welded, painted steel
pipe frame
glass point-fixed clamped with ad-
justable mount; 304 stainless with 80
durometer neoprene pads; 3/8 inch an-
nealed laminated with .060 PVB

The Glass Umbrella canopy is a small nate, cut, transport and install.
experimental art project. It is comprised
of 17 unique glass panels cascading The 17 panels were mapped and mod-
over an exterior stairway in a small of- eled per the architect’s specifications.
fice building, accessible only through Stress analysis revealed the distribu-
a locked interior door. It is prominently tion of forces through each panel and
visible from the exterior of the building, verified adequacy. A molding technique
and intended as a feature element of the was conceptualized and steel molds
architecture. The path to implementation designed to facilitate the slumping pro-
of this innovative structure traversed a cess. Unavoidable inaccuracies in the
landscape of questions: how to design, slumping process created the require-
fabricate and install something never ment for a clamping device capable of a
attempted before, and how to define, wide range of adjustability.
describe, quantify, analyze, mold, lami-

46 - Skylight
Bending the Rules deep, double-curved surfaces. Even
in the plastic state glass remains
By all accounts, the Glass Umbrella relatively stiff. Single curvature bends
marks the first time large sheets of are easy. The double-curvature forms
float glass have been subject to such act to further stiffen the glass locally
extreme curvature. (Frank Gehry used as a function of the geometry, and the
similar but less extreme bent glass in material resists slumping in certain
a vertical orientation on the interior of areas. It was impossible to predict the
the Conde Naste project, in the same exact deformations attainable through
approximate timeframe.) However, to this slumping process. It was thus im-
regard the project as high-tech, as in the possible to predict the exact footprint
application of cutting-edge technology, or edge profile resulting in the slumped
would be a gross misunderstanding of panels. For this reason, the glass
the story of the Glass Umbrella, which, was initially cut oversized, slumped,
like many such innovative architectural laminated, and finally the edges were
designs, is much more a tale of high- trimmed to get as close as possible to
craft than high-tech. the desired footprint.

Prior to our involvement, the design- In the slumping process, the mold sur-
ers identified an interested fabricator, a face was covered with fiberglass blan-
local family-owned second generation kets. Two identical oversized pieces
operation specializing in glass bending. of glass were then balanced upon the
They were introduced to us as a pos- mold surfaces, one atop the other. The
sible fabrication source and displayed molds were rolled into the furnace, the
both an understanding of the glass doors closed, and the furnace fired,
requirements and optimism that the generating a temperature that carried
panels could indeed be fabricated. Their the glass through the transition zone
initial concern was with the molds, as and into the plastic state.
each of the 17 required a unique mold
of complex geometry. We developed Parameters based upon empirical ex-
an egg crate approach that allowed perimentation were developed, allow-
us to map a section curve of the glass ing us to approximate the magnitude
surface and translate that into a draw- of possible slumping. When these were
ing that could easily be flame cut from overlaid against the required shapes,
steel plate. Plates fabricated from the many areas were identified where the
incremental x and y sections were curvature exceeded these parameters,
simply slotted together and tack welded especially with the 3/8 inch composite
to create a stable mold base with the glass panels. The architect was quite
required surface. 17 unique molds were insistent upon attaining the curvatures
constructed in this manner. The glass as originally designed with the hair
was to be heated and slumped over blower. We thus made extraordinary
these molds. efforts to achieve these curvatures as
closely as possible, experimenting with
Glass slumping is not a high tolerance variables of te mperature and time,
process, especially when attempting and whatever technique we could

Enclos Corp - 47
 identify that might improve the process. panel subjected to heat and pressure,
In many instances this required extreme bonding the PVB to the adjacent glass
measures, including pushing on the hot surfaces. The process requires approxi-
The Glass Umbrella glass with long rods inserted through mately 4 hours at 280°F (138°C) within
small openings in the furnace sides in an autoclave to provide the required
Culver City, CA an attempt to force it into conformance pressure and facilitate the bond. The
with the mold surface. The next step primary advantages of laminated glass
in the process was laminating. Glass involve the redundancy provided by the
laminating technology derived from re- composite panel comprised of multiple
search conducted by the glass industry glass ply, and include safety and secu-
in the 1930’s with the primary intent of rity. When one glass ply of a laminated
providing a safer product for automotive panel breaks, the panel remains intact.
glass. Decades of development have Most laminated glass is 2-ply, however
resulted in a laminating technology for multiple ply are possible and are finding
architectural glass that finds exten- increasing application in structural ap-
sive use in the building arts today. The plications, as in stair treads, landings,
most typical practice involves the use and even stringers, as well as beam and
of polyvinyl butyral (PVB) in thin sheet column components. Laminated glass
form. The PVB is sandwiched between also provides enhanced performance
panes of glass, and the composite in extreme loading events, such as

48 - Skylight
blast and high-impact loads. Laminates
intended for extreme loading applica-
tions will sometimes include an inner ply
of polycarbonate. In addition, laminated
glass is an effective sound dampening
material and is finding increasing ap-
plication for its acoustic properties. An
important consideration for the Glass
Umbrella project was that the glass pan-
els could be trimmed to their final profile
as a final fabrication step, something
not possible with heat-treated glass.

As with the slumping process, never be-

fore had the lamination of such dramati-
cally shaped glass been attempted. The
slumping process sometimes resulted in
differences between the two pieces of
glass laid atop the mold in the areas of
the most extreme curvature. If the dif-

Enclos Corp - 49
 ferences were great enough they would
result in a bubble in the laminate where
the PVB was unable to bridge the gap
The Glass Umbrella between the panels and would adhere
only to one side. Lesser differences
Culver City, CA simply resulted in some magnitude of
residual stresses as discussed above.

trimming and edge treatment

If a panel made it this far without

bubbles or breaking, it was time to
trim the piece to provide the desired
edge-profile. Our designers devised a
technique for transferring the perimeter
profile to the undulating glass surface.
The surfaces were then scored on both
sides and broken away to reveal the
new edge. Another area of experimen-
tation was with the edge treatment.
Cut glass edges are usually treated to
provide safety in handling the glass, as
the raw cut edges are extremely sharp.
The treatment is usually some form of
grinding process, whether done on a
CNC machine or by hand. In our case
it was by hand; even if we had access
to a CNC type machine it could never
have accommodated the wild edge
geometries of the Umbrella panels. The

slumping marking

50 - Skylight
problem is that the grinding process
can generate small cracks at the edges
that weaken the panel. Under stress,
it is from these microscopic edge
defects that the crack will propagate.
We ultimately took to polishing the
edges, a process which removes many
of the cracks rendering the glass panel
stronger, but this was a tedious and time
consuming process that further added
to the increasing burdens of glass fab-
rication.

the bionic arms

The fixing of the glass panels turned

out to be very near as challenging as
the making of the panels themselves.
As seventy-three panels were made to
provide the final 17, so were 3 variations
of the fixing system prototyped before
arriving at a workable solution. There
were several problematic conditions to
be accommodated by the fixing system.
There was a small overlap between the
panels, with an upper panel shingling
its lower neighbor. The fixing system
somehow had to bridge from the struc-
tural support below, through, or around
the glass panel immediately above,

cutting bagging laminating

Enclos Corp - 51
 and to the adjacent panel atop the first,
while providing for the exceedingly large
variations in entry angles due to the
The Glass Umbrella poor tolerances of the slumped glass.
Culver City, CA Much of our work is rooted in the study
of natural form. Here, an articulated
arm was conceived to reach from the
steel pipe support and cradle the panel
edges, rather like the palm support of
a hand with fingers folding around the
edge and over the top to restrain the
glass from uplift. It was a complex prob-
lem requiring many design iterations. We
learned from hard experience the critical
requirement of mockups when develop-
ing such a unique system. The first two
mockups were great successes in dem-
onstrating to us just how to assure the
breaking of the glass panels, how easy
it was to break them by inducing just
small local moment forces into the area
of support. These mockups informed the
development of a design that provided
full rotation at the connection point,
minimizing or eliminating any moment
transfer into the glass. But by this time
we had broken a number of panels and
accumulated quite a number of stain-
less steel plate components of various

52 - Skylight
configurations, all destined for the scrap
heap and a recycled future.

Installation

Glass installation is most often facili-

tated by suction cups attached to some
type of crane as discussed above.
We had a small crane at the site for
this purpose, but as in the factory, the
suction cups would not serve. Instead,
our riggers had to devise a byzantine
cat’s cradle of nylon straps that would
hold the glass in something near to its
installed position in the structure, as the
panels were too heavy to manhandle
in place. Each piece of glass had to be
treated differently, finding its unique
point of balance, providing enough sup-
port so as not to overstress the glass lo-
cally. Most of the panels had to be held
in position by the crane until the clamps
could be fixed.

Enclos Corp - 53
Enclos Press Inter-Story Acoustical Evaluation of
Publications Unitized Curtainwall Systems - 2008

Analysis and Design of Spandrel and

Shadowbox Panels in Unitized Curtain
Walls - 2009

Enclos: Collective Works - 2009

Facade TecNotes Series:

1 Skylight

2 Double Skin

3 Architecturally Exposed Structural

Steel (AESS)

4 Airports

5 Healthcare

6 BIM and the Building Facade

7 Cable Nets

8 Security

9 LEED Skins
 enclos e corp
@ Enclos Corp 2009 I www.enclos.com I 888.234.2966 I curtainwall@enclos.com