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VOLUMETRIC TRANSPARENCY:Application of an Improved Double Glass

Facade System to Cowgill Hall, Blacksburg

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Lu Wang

Blacksburg, VirginiaAugust 21st, 2002

Thesis submitted to the faculty of theVirginia Polytechnic Institute & StateUniversity in partial fulfillment of therequirements for the degree of

Master of Architecture

Professor William Galloway

Professor James Jones

Professor Hunter Pittman

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Abstract

The initial idea for this thesis involved thedesign of an addition to Cowgill Hall on theVirginia Tech Campus in Blacksburg, Virginia.This addition, to be constructed with anenvelope comprised primarily of glass, wouldbe located on the south side of Cowgill Hall,adjacent to Cowgill Plaza. The all-glass boxwould add a transparent volume to the existingbuilding, diminishing the barrier betweeninside and outside. The project would alsoenergize the existing plaza by connecting theactivity inside to outside and providing thedynamic reflection of a glass facade. CowgillHall would also be given new life by providinga new shared vertical space for dynamiccommunication and light. Potential problemsassociated with the all-glass box include highheat loss or gain, glare and noise control. Adouble envelope system of construction wasexplored as a means of solving some of theseproblems and an endeavor on literature review,technical research and design improvement ofdouble glass facade was also made.

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Table of Content

Space

Transition

Structure

Site

Ecology

Conclusion

Idea Development 8Solution 10Truss System 12Column Clip 14Spider &Suspension 16Glass meets Ground 18Glass meets Roof 20Glass meets Existing Corner 22Floor Plan Rearrangement 24Interior 26Outdoor 27

Definition of double glass facade 30Case Study of Double Glass Facade 31A closer look at double glass facades, physical characteristics 37

Understand Cost Efficient Potential 43A closer look at double glass facades, glass property research 42

Key Parameters of Double Glass Façade Properties 44Computational Fluid Dynamic 45

Application in Cowgill 50CFD - Conclusion 48

Volume + Transparency 6

CFD - Model 46

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Challenges 7

Reference 53Acknowledgment 54Vita 55

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SiteVolume + Transparency

Site Plan

NORTH

1. Cowgill Hall2. Cowgill Plaza3. Burruss Hall

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SiteChallenges

1. How is the additionconnected to the existingstructure?

2. What architecturaltransitions are necessarybetween the new volume andthe existing surroundings?

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StructureIdea Development

Structural elegance and Lightness are the primary goals of the atrium addition to achieve volumetric transpar-ency. Several optional structural systems were studied by asking: How are the primary structure, secondarystructure and skin as a whole related and what role does each element play toward the goals?

1. Suspension Structural Sys-tem:A suspension structural sys-tem is very light and elegant.It will also provide the possi-bility of suspending the floor,which creates spatial benefitsby offering usable area at theupper level without intrusivestructure at the lower level ofthe atrium space. However, asteel truss may obstruct andoccupy additional space onthe plaza, which may make thefacade too obtrusive in theplaza. Considering the existingBurchard Hall underneath theplaza, the construction pro-cess would be difficult, and thefoundations may not be easilyaccomplished.

2. Truss Structure with Mul-lion System:A truss structure may not beas light as a suspension struc-ture, but it is an easier con-struction method, with fewerconflicts with the existing un-derground structure. A mul-lion system can also easilyconnect the structure and theglass skin. However, the steeltruss does not belong to thelanguage of the plaza and thesurrounding buildings, whichare glass and concrete orstone. A mullion system mayalso block up to 30% of thefacade, causing loss of trans-parency.

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3. Truss Structure with trusssuspension system:Instead of using a mullionsystem, a truss as a second-ary structural system may beused, which can reduce themass of the secondary struc-ture, thus enhancing trans-parency. However, in thiscase, the depth of the steeltruss system, plus the sec-ondary truss suspension sys-tem, becomes a problem interms of spatial efficiencybecause it consumes a rela-tively large portion of the theatrium space.

StructureIdea Development

The final solution uses asteel column and beam plusa secondary truss system,which has the best balanceof lightness and minimumspace usage. The structureis inside, so the facade has aplanar appearance to theplaza.

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StructureSolution Steel Column + Truss Suspension System + Spider + Prefabricated Double Glass Unit

Steel columnstructure-The first elementin the hierarchy ofthe structuralsystem.

Truss suspensionsystem-The secondaryelement in thehierarchy of thestructural system,transferring loadfrom the spiders tothe columns.

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Spider-The third elementin the hierarchy ofthe structure,attaching the glassto the truss system.

Prefabricated doubleglass unit-The fourth elementin the hierarchy ofthe structure,attached to thespider, providingthe enclosure of theatrium.

StructureSolutionSteel Column + Truss Suspension System + Spider + Prefabricated Double Glass Unit

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StructureTruss System

A truss system is a very lightsecondary system to support thespiders and glass skin. But it hasto have a certain distancebetween the two members of thetruss to hold the horizontal load.In order to save space, the trusssystem must be tightlyintegrated with the columns, sothey overlap each other in planrather than occurring assuccessive layers in the steeltruss structure + secondary trusssystem alternative discussedearlier.

Every truss unit is composed oftwo pieces of single steel rod.One member primarily resistspositive pressure on the glassskin, while the other primarilyresists negative pressure.

Truss system Plan

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Typical trussunit on thesouth facingfacade

StructureTruss System

The dimension of the trussunit on the east and westfacing facades are half thatof the south-facing facade.Therefore its profile variesfrom the typical truss uniton the south facing facade.

Truss unit onthe east andwest facing

facade

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StructureColumn Clip

Condition 1

Condition 3

Column clips are used to connect thecolumn and the truss. They are designedto receive the two members of the truss,and grasp the column at the same time.Due to different locations of thecolumns and different truss types, thecolumn clips need to have threedifferent configurations.

Condition 2