1Prof. G G Schierle, PhD, FAIA

Design of Fabric StructuresSession T33, Thursday, 04/30, 2 3:30 PM

Design of Fabric Structures

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2Acknowledgements/Credits

This presentation includes book excerpts of

Structure and Design

http://www.universityreaders.com/titles/schierle/

Design of Fabric Structures

This program is registered with the AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to constitute approval, sponsorship or endorsement by the AIA of any method, product, service, enterprise or organization. The statements expressed by speakers, panelists, and other participants reflect their own views and do not necessarily reflect the views or positions of The American Institute of Architects or ofAIA components, or those of their respective officers, directors, members, employees, or other organizations, groups or individuals associated with them. Questions related to specific products and services may be addressed at the conclusion of this presentation.

3Learning Objectives

Evaluate appropriate uses of fabric structures, i.e., select appropriate fabric structure types, and select and specify proper fabric material

Design efficient fabric structures, design fabric structure details, and select and design proper fabric boundaries

Evaluate the cost of fabric structures, day-lighting of fabric structures, and the appropriateness of fabric structures for various loads

Design of Fabric Structures

Saddle shape Wave shape Arch shape Pont shape

4Anticlastic Stability

Two stressed strings stabilize a point in space

Two sets of strings form a stable surface

Without prestress, convex fiber gets slack, causing instability

Flat fiber deforms greatly under load, causing instability

Triangular panels are flat & unstable (AVOID)

Prestress Prestress (PS) effect on a stringF = force, P = load, = deflection 1 Without prestress top link resists all

Assume: = 12 With prestress = 1/2

Top link increase: F=PS+P/2Lower link decrease: F=PSP/2

3 Stress / strain diagram f/A without prestressB with prestressC Prestress reduced to PS = 0D Prestressed string after PS = 0

Cable nets need about 50% prestressFabric structures need about 30% prestresshttp://www-classes.usc.edu/architecture/structures/papers/GGS-Yin.pdf

5Minimal SurfaceCriteria: Minimum surface area Equal stress throughout Equal +- curvature at any point

Governing Equations (Schierle 1977*)*First published 1977 inJournal of Optimization Theory and Applications

F1/F2 = A/B

Y = F1(X/S1)K/F1+ X tan Y = F2(Z/S2)K/F2

K= F1+F2

Sm

all d

efle

ctio

n

P

rinci

pal c

urva

ture

Larg

e de

flect

ion

Stra

ight

gen

erat

ing

line

Fiber orientationGood Flawed

6Fabric Properties

8 to 20 kN/m46 to 114 lb/in

Permanent + mobileInternal + external

Flouro-polymer fabric

Coated or uncoated fabric*

40 to 100 kN/m228 to 571 lb/in

Permanent + mobileInternal + external

PTFE fabric(good qualities for sustainability)

Coated or uncoated fabric*

6 to 12 kN/m34 to 69 lb/in

PermanentInternal + external

Flouro-polymer foilETFE

Foil*

6 to 40 kN/m34 to 228 lb/in

Permanent internalTemporary external

PVC foilFoil

50 to 100 kN/m286 to 571 lb/in

Permanent Internal + external

Fine mesh fabricLaminated with PTFE film

Laminated fabric*

20 to 100 kN/m114 to 571 lb/in

PermanentInternal + external

Glass fiber fabricSilicone coating

Coated fabric

20 to 160 kN/m114 to 914 lb/in

PermanentInternal + external

Glass fiber fabric PTFE coating

Coated fabric*

40 to 200 kN/m228 to 1142 lb/in

Permanent + mobile Internal + external

Polyester fabric PVC coating

Coated fabric*

Tensile strengthCommon useMakeupType

* Self-cleaning

> 25 yearsUp to 90 %++++

> 25 years15 to 40 %++++

> 25 yearsUp to 96 %++++

15 to 20 yearsinternally

Up to 90 %+0

> 25 years35 to 55 %++++

> 20 years10 to 20 %++++

> 25 years4 to 22 %++++

15 to 20 years0 to 25 %++

DurabilityTranslucencyUV light resistance++ very good+ good

Fire rating++ incombustible+ low flammability0 none

Maximum spansAssuming: Live load LL = 20 psfSafety factor Sf = 4Span/sag ratio L/f = 10

Fabric breaking strength Max. span600 pli (lb/in) ~ 60 ft800 pli (lb/in) ~ 80 ft

200 pli800 pli150 pli600 pli100 pli400 pli

Design stressTensile strengthDesign stress (tensile strength / 4)

Costs Type Cost / sq. ftPrefab PVC $15 to $20Custom PVC $30 to $60PTFE Teflon-coated fiberglass $60 to $180Note: costs exclude foundations

7RL

RR

H

H

TR

TL

W= w L

w

h

RL

RR

L/2L

f

f H

Symmetric suspensionHorizontal reaction H = w L2/(8f)Vertical reaction R = w L/2Max fabric tension T = 1.35 w L

Asymmetric suspensionVector methodTotal load W = w LFabric tensions TR TLHorizontal reaction HVertical reactions RL RR

w

Design / AnalysisRadial loadEdge cable tension T = R p

Lateral LoadSeismic (not critical)V = Cs WV = seismic base shearCs = Seismic coefficient W = mass (dead load)Example (V / ft2, Cs = 0.2, w = 1 psf)V = 0.2 x1 V = 0.2 psf

LDG: Lateral Design Graph Sample: 100 x 50 x 20

Wind (critical)Velocity 90 mph (most USA) 150 mph (Golf coast)Gust factors (G= 0.85 for rigid structures)G ~ 1.5 for fabric structuresExample (V per ft2, p = 20 psf ~ 90 mph)V = p G = 20 x 1.5 V = 30 psf

8Acoustics Thin fabric provides little sound insulation Micro-perforated foils absorb sound(suspended under structural fabric)

Form may be used to control acoustics Anticlastic forms disperse sound Synclastic forms focus sound

LightingDaylight sunny days ~75000 luxDaylight overcast ~25000 lux10% translucent fabric ~2500 - 7500 luxTypical office lighting ~1000 lux

ThermalWhile fabric has low R-valuesThermal reflection is very good

Surf

ace

cond

ition

sP

oint

sha

pe A

rch

shap

e

Wav

e sh

ape

Sad

dle

shap

e

Edge

con

ditio

nsE

dge

beam

Edg

e ar

ch

Edg

e ca

ble

9Edge Conditions

Edge Cable (tension)

Edge Arch (compression)

Edge Beam (bending)

UCB Canopy

Stage canopy

Edge

Cab

le

tens

ion

10

Raleigh Arena North Carolina (1953)Architect: Novicki and DeitrickEngineer: Severud Elstad Krueger

Edge arch / cable roof

EFL portable classroom (1968)Architect: G G SchierleEngineer: Nick Forell

Edge arch / anticlastic Fabric

Sony Center BerlinArchitect: Helmut JahnEngineer: Ove Arup

Edge ring / radial cables and fabric

Edge

Arc

h / R

ing

co

mpr

essi

on

Horticultural CenterGallaway Gardens, GeorgiaBy ODC

Dining Pavilion Saddlebrook FloridaBy Helios Industries

Note:Edge beams facilitate assemblies

Edge

Bea

m

bend

ing

11

Saddle shapes Wave shapes

Surf

ace

cond

ition

s

Arch shapes

Stay

ed

Mas

ts

D

ish

Rin

g

P

unct

ure

Pro

pped

Mas

ts

E

ye

Loo

p

R

adia

l Point shapes

12

Saddle shapes

Courtesy USA Shade

Expo 64 LausanneArchitect: Saugey / SchierleEngineer: Froidevaux et Weber

26 restaurant pavilions: Featured Swiss regional cuisines Symbolizing sailing and mountains

13

R=100

L=120

f=12

A A

B

BSection B-B

Design example

Assume:

Wind pressure p = 30 psf

Allowable fabric stress Fa= 200 pli

Available canvass stress Fa= 50 pli

Wind load (normal to fabric)

T = p R = (30)(100) T = 3000 #

Fabric stress per inch

f = 3000/12 f = 250 pli

Fabric NOT OK 250 > 200 > 50

Cable net was required

Assume: Same allowable stressGravity load w = 20 psfGraphic method

Total LoadW = w L = 20 (120) W = 2400 #Horizontal reaction H = 3000 #Vertical reaction RL= 2400 #Fabric tension T = 3720 #Fabric stress (#/in)f = 3720#/12 f = 310 pliGravity load not OK 310>200>50Cable net was required

L=120

f=12

A A

B

B

h=40

HRL

f RL=2400#

H=3000#

W= 2400#T=3720#

w = 20 psf

14

15

Wave shapes

Computer model

San Diego Convention CenterArchitect: Arthur EricksonEngineer: Horst BergerFabric design: Horst Berger

Concrete pylons at 60 supportridge, valley, and guy cables thatspan 300 between pylons

Translucent Teflon coated fiber glass fabric provides daylight

Ridge cables support gravity loadValley cables support wind upliftGuy cables support : Flying buttresses

1Denver AirportArchitect: FentressPhoto: David Benbennick

Denver AirportPhoto: David Benbennick

17

Sony Center BerlinArchitect: Helmut JahnEngineer: Ove Arup

Truss compression ring 335

Flying buttress mast supports

top tension ring

Radial guy cables support mast

Radial roof cables hold fabric

Translucent fabric

Arch shapes

18

Study model

EFL portable classroom (1968)Architect: G G SchierleEngineer: Nick ForellSize: 30x40First twin fabric with thermal insulation

Theater pavilion Armonk (1968)Architect: G G SchierleEngineer: Nick ForellSize 60x80 - capacity 600Longest span fabric roof 1968 fabric tensile strength 720 pli

Skating Rink MunichArchitect: AckermannEngineer: Schlaich / BergermannPrismatic arch truss supports translucent PVC fabric on wood slats and cable net

Arch truss detail

19

Point ShapesSt

ayed

M

asts

Dis

h

R

ing

Punc

ture

Pro

pped

M

asts

Eye

L

oop

Rad

ial

Hudson River Park PavilionNew York, NYCourtesy USA Shade

Sea-World Pavilion VallejoArchitect: G G SchierleEngineer: ASI, Advanced Structures Inc

20

Fabr

ic p

atte

rn s

eam

Twin

fabr

ic @

hig

h st

ress

Pre

stre

ss tu

rnbu

ckle

Web

bing

hol

ds fa

bric

Fabric corner Ground anchor

Twin fabric @ high stress

Mast topDet

ails

Erection

Color lighting

Layout

Erection

21

German Pavilion Expo 67 MontrealArchitect: Gutbrod & OttoEngineer: Leonhardt & Andrae

Translucent fabric for naturallighting suspended from cablenet on 3-D adjustable hangers.Prefab panels assembled onsite with lacing.

Balance Forces

Unbalanced

Balanced

22

Stretch fabric design / testing model

Design ProcessStretch Fabric models

Stretch fabric models for form-finding and testing

Design ProcessComputer Aided Form-finding Analysis Pattern design

Computer modelComputer model

Load shape dotted lines

CAD patterns by triangulation

23

OptimizationEdge & surface curvature(Schierle, 1971)

Usual optimum L/f = 10L = spanf = sag L

f

Watts Towers Cultural Center (2002)Architect: Ado / SchierleEngineer: ASI

Removable fabric and cable truss

24

Stadium Oldenburg GermanyArchitect: Kulla, Herr und Partner Engineer: Schlaich Bergermann

Anticlastic fabric panels suspended from cantilever cable trusses

25

Grid Shell Mainz, GermanyArchitect: Mutschler / Otto Engineer: Ove ArupGrid shell of 50 cm square, 50 mmtwin slats form rhomboids in space; covered with translucent fabric.

Form-finding model

Millennium Dome LondonArchitect: Richard RogersEngineer: Buro Happold

26

anticlasticfabric

Cur

ved

wal

l to

resi

st w

ind

27

Speaker

Prof G G Schierle, PhD, FAIAUSC - School of ArchitectureLos Angeles, CA 90089-0291

T 213-740-4590F 213-740-8888schierle@usc.eduhttp://www.usc.edu/structures

Prof G G Schierle, PhD, FAIAUSC - School of ArchitectureLos Angeles, CA 90089-0291

T 213-740-4590F 213-740-8888schierle@usc.eduhttp://www.usc.edu/structures

http://www.universityreaders.com/titles/schierle/

thank youthank you