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Designing with Glass
Aluminum andStainless Steel
Presented by: Tom Castle, S.E.
Ficcadenti Waggoner & Castle
Walnut Creek, CA
SEAONC 12/14/11
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Designing with Glass Aluminum
and Stainless Steel
Presentation is an overview of the subject withconcentration on the building industry
Many designs are done by manufacturers or on adesign-build basis with specialty engineers
Having a basic knowledge is important to know
what is possible and how the specifications for thedesign should be completed
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2009 IBC or 2010 CBC
Chapter 14 – Exterior Walls
1403.3 – Design walls to resist load per Chapter 16
1405 – Wall Coverings including glass, stone and masonry
veneer requirementsChapter 16- Structural Design
1604.3 – Serviceability limits for wall deflections
Deflections based upon 70% of Component and Cladding Loads
L/175 for Aluminum mullions supporting glass edges for each
light or L/60 total1607.7.1 Handrails and Guardrail loading
Chapter 24 – Glass and Glazing
2407 – Glass in Handrails and Guards
ASTM C 1036 – Standard Specification for Flat Glass
Glass –Building Code
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Glass
How does glass behave?
•Glass has shown an almost perfect elastic, isotropic behavior andexhibits brittle fracture.
•It does not yield plastically, which is why local stress concentrations arenot redistributed like most building materials.
•The tensile strength of glass is dependant upon mechanical flaws at thesurface.
•Glass fails when the tensile stress at the tip of one flaw reaches acritical value.
•Compressive strength is irrelevant for almost all structural applications
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GlassGlass Processing
Annealed Glass:This is standard float glass. This is weakest and typically
breaks into large fragments.
Tempered glass (heat treatment):This process creates a favorable residual stress field with
tension on the interior and compression on the surface. This type hasthe highest structural capacity. Residual strength is lowest and breaks
into small fragments.
Heat Strengthened Glass:This is between the two above. It has residual compression
stresses at a lower level them fully tempered, but produces largerfragments upon failure allowing for some post failure capacity.
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Glass
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Glass
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Glass
Heat Soaking:
There is a small risk of spontaneous failure in tempered glass within afew years of production. This is caused by nickel sulfide inclusions inthe glass. Heat soaking process is used to reduce the risk of this failurein the field by causing the failure in the soaking process thus eliminatingthe flawed pieces.
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Glass
Laminated Glass:
•This is two or more panes bonded togetherby some transparent plastic interlayer.
•This process allows for significantimprovement in post breakage behavior.
•Most common interlayer is polyvinyl butyral(PVB)
•The larger the fragmentation of the glassthe larger the post breakage capacity.
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Glass
Design Methods:
•For common geometries and loadingconditions hand calculations based upontables and graphs are usually sufficient for
determining stresses and deflections
•Finite element analysis is typicallyconducted for more complex geometry
•Meshes are denser at discontinuities orbolt holes•Fixing points must be accuratelymodeled in terms of rotational stiffness•Contact with metal is avoided andachieved by using liner, gasket orbushing. Models should only allow forcompression at contact surfaces
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Glass
Design Methods:
•For common geometries and loadingconditions hand calculations based upontables and graphs are usually sufficient for
determining stresses and deflections
ASTM E1300 has tables and graphs:
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GlassDesign Methods: ASTM E1300 has values for allowable stresses in types of glass for 3 secondduration loads based upon probabilities of breakage.Probability of 8 lites per 1000 is typically used for vertical glazing.Probabilities down to 1 lite per 1000 can be used in critical applications or
overhead applications.
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GlassDesign Methods:Glass strength is time dependant. ASTM E1300 gives Load Duration Factors
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GlassDesign Methods:
Structural Silicone Sealants
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GlassDesign Methods:
Structural Silicone Sealants – Values can be tested or 20 psi as a rule of thumb
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GlassDesign Methods:Point Supported Glass: General rule of thumb is bearing load of 4,000 lbs/per inch ofglass thickness actual design values may be based upon FEM or testing.
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Glass
Design Methods:
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2009 IBC or 2010 CBC
Chapter 20 – Aluminum
Refers to Aluminum Design Manual for Design and Chapter 16for Loads
Aluminum –Building Code
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Aluminum
ADM utilized either ASD or LRFD design methods.
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Aluminum
Aluminum is typically alloyed with other metals toachieve desired properties. Each alloy is
designated by a four digit series.
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Aluminum
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Aluminum
6061 Aluminum is a common type used in
building industry. It has a yield stress of 36 KSI
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Aluminum
ADM has industry standard shape properties
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Aluminum
ADM has formulas for different shapes andloadings to determine allowable stresses.
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Aluminum
Welding significantly reduces the permittedstresses in the material.
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2009 IBC or 2010 CBC
Chapter 22- Steel
2210 – Cold Formed Steel refer to AISI Design Manuals
ASCE8-02 for Cold Formed Stainless Steel – Not referenced
Where is Stainless in the code?
Stainless –Building Code
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Stainless
Stainless is not like Structural Steel• Anisotropy – Not the same properties in longitudinal and
transverse not tension and compression•Nonlinear stress strain – Gradual Yielding•Low proportional limits – Affect buckling behavior•Pronounced response to cold working
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Stainless
Cold Formed Stainless Steel can be designed using ASCE 8-02
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Stainless•No American Building Code Manual (otherthan cold formed – ASCE 8)
•Not referenced in IBC
•Use engineering judgment and AISC as abasis knowing its limitations
•Some European Codes are available formore complex analysis
•Usually used in simple applications andconservative analysis is sufficient
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Stainless
Types of Stainless Steel TypicallyUsed:
There are many types of stainless with variedproperties.
Most typically ASTM 304 or 316 are used inbuilding construction. 316 is more corrosionresistant than 304 and typically is also moreexpensive. Both have typical yield stresses in therange of 42 KSI.
The steels of type ASTM 304, 316, 304L, and 316Lhave very good weldability.
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Designing with Glass Aluminumand Stainless Steel
Corrosion Issues:
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Designing with Glass Aluminumand Stainless Steel
Corrosion Issues:
Fasteners in Aluminum should be Cadmium, Zinc,Chromium or Tin plated. Stainless fasteners arealso acceptable.
Aluminum will corrode if embedded or touchingconcrete with calcium chloride. If the aluminum is
coated and chlorides are not present then nocorrosion.
Mild steel fasteners should not be used to connectstainless members.
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Designing with Glass Aluminumand Stainless Steel
Seismic Issues (drift accommodation):
ASCE13.5.3: Exterior Nonstructural WallElements and Connections
ASCE 13.5.9: Glass in Glazed Curtain Walls,Glazed Storefronts and Glazed Partitions
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Designing with Glass Aluminumand Stainless Steel
Seismic Issues: ASCE 13.5.3
Dp
Interstory
Total
Joint atHead ofWindow
FloorBeyond
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Designing with Glass Aluminumand Stainless Steel
Seismic Issues: ASCE 13.5.3Dfallout >= 1.25 I Dp
Exceptions:
Glass with Sufficient Clearance to its frame such thatphysical contact between the glass and frame will notoccur at 1.25 Dp
Fully tempered monolithic glass no more than 10 feetabove a walking surface
Annealed or heat treated laminated glass that iscaptured mechanically by a wall system glazing pocket
Dfallout is determined in accordance with AAMA 501.6 or byengineering analysis
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Designing with Glass Aluminumand Stainless Steel
Seismic Issues: ASCE 13.5.9
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