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BUILDING CONSULTANTS

Building Science SpecialistsContract AdministratorsReserve Fund PlannersConsulting Engineers

Arbitech ADRArbitration, Mediation, Litigation Support for

Engineering and Construction Disputes

Gerald R. Genge, Gerald R. Genge, P.Eng., C.Eng., BDS, BSSO, C.Arb, Q.Med.P.Eng., C.Eng., BDS, BSSO, C.Arb, Q.Med.

MMAH SB-13MMAH SB-13WHY? …HOW? … WHAT NOW?WHY? …HOW? … WHAT NOW?

30 incidents of glass guard breakage in 30 incidents of glass guard breakage in 2010 - 2011 on 11 buildings in Toronto2010 - 2011 on 11 buildings in Toronto

Breakage was primarily guard panels using Breakage was primarily guard panels using tempered glasstempered glass

Earlier breaks were repaired without notice Earlier breaks were repaired without notice to the Cityto the City

Breakage became a public concern Breakage became a public concern resulting in:resulting in:

news reports (CBC, City, etc.)news reports (CBC, City, etc.) industry magazine articles industry magazine articles

(US Glass - October 2011)(US Glass - October 2011) CondoBusiness – November 2011CondoBusiness – November 2011

parody (22-Minutes)parody (22-Minutes)

Summer 2011 - News Summer 2011 - News Bulletin!Bulletin!

City of Toronto issues 9 (maybe more) City of Toronto issues 9 (maybe more) “Orders “Orders to Remedy Unsafe Building” to Remedy Unsafe Building” between December between December 2010 and August 2011. [now double that 2010 and August 2011. [now double that number]number]

Developers of new condos order to have Developers of new condos order to have engineering assessments and design for engineering assessments and design for remedial work.remedial work.

GRG engaged as “Peer Review Consultant” and GRG engaged as “Peer Review Consultant” and examined reports from Consultants on 6 examined reports from Consultants on 6 buildingsbuildings

Stakeholders became engaged in the issuesStakeholders became engaged in the issues Concerns about delayed constructionConcerns about delayed construction Various means of problem resolution Owners of Various means of problem resolution Owners of

existing buildings questioning public safetyexisting buildings questioning public safety Other issues started to arise regarding designOther issues started to arise regarding design

ActionAction

BALCONY SLAB

PO

ST

RAIL

GLASS PANEL

ANCHORAGE

FLY-BY GUARD

BY-PASS GUARD

SHATTERED GLASS PANEL

GLASS TO METAL CONTACT

DISENGAGED GLASS PANEL

GLASS TO GLASS CONTACT

INADEQUATE ANCHORAGE

Choices for Choices for MaterialsMaterialsDesign Design ConstructionConstruction

Influence CircleInfluence Circle Aesthetics Existing Standards Existing Regulatory

Requirements

Float glassFloat glass::

Float glass is a sheet of glass made by floating Float glass is a sheet of glass made by floating molten glass, at a temperature of approximately molten glass, at a temperature of approximately 1200°C, on a bed of molten metal.1200°C, on a bed of molten metal.

Basic float glass is not a safety glass and is not Basic float glass is not a safety glass and is not used for balcony guards because it tends to break used for balcony guards because it tends to break into large, jagged shards. However, it is the base into large, jagged shards. However, it is the base material that is further processed into tempered material that is further processed into tempered glass and laminated glass.glass and laminated glass.

Types of GlassTypes of Glass

Tempered glassTempered glass::Tempered safety glass is Tempered safety glass is float glass which is float glass which is reheated to a temperature reheated to a temperature of approximately 600°C of approximately 600°C and is subsequently and is subsequently cooled cooled rapidly rapidly by cold air creating by cold air creating high stresses in the surface high stresses in the surface as it contracts. Tempered as it contracts. Tempered safety glass is much safety glass is much stronger than base float stronger than base float glass. If broken, safety glass. If broken, safety glass tends to shatter into glass tends to shatter into small fragments. Tempered small fragments. Tempered glass cannot be cut, glass cannot be cut, ground, or drilled after it is ground, or drilled after it is tempered. tempered.


Photo source PPG Education Centre

Heat strengthened Heat strengthened glassglass::

Heat strengthened glass Heat strengthened glass is like tempered glass but is like tempered glass but it is allowed to it is allowed to cool more cool more slowly slowly which reduces the which reduces the stress in the surface of the stress in the surface of the glass. Heat Strengthened glass. Heat Strengthened glass is about twice as glass is about twice as strong as base float glass. strong as base float glass. If broken, heat If broken, heat strengthened glass tends strengthened glass tends to shatter into shards. to shatter into shards.


Photo source PPG Education Centre

Heat soaked tempered glassHeat soaked tempered glass::Heat soaked tempered glass is tempered glass Heat soaked tempered glass is tempered glass that has been treated in a chamber by raising that has been treated in a chamber by raising the temperature to approximately 290 C for 2 the temperature to approximately 290 C for 2 hours to accelerate the expansion of NiS hours to accelerate the expansion of NiS inclusions. This causes glass containing NiS inclusions. This causes glass containing NiS inclusions to break in the heat soak chamber. inclusions to break in the heat soak chamber. The heat soaking process is not 100 percent The heat soaking process is not 100 percent effective and increases the cost of the glazing. effective and increases the cost of the glazing. European Standard EN 14179 is the most European Standard EN 14179 is the most common standard used to specify heat soaking common standard used to specify heat soaking of glass.of glass.


Potential collateral consequences of heat Potential collateral consequences of heat soaking tempered glasssoaking tempered glass:: DamageDamage to adjacent test lites should a break occur to adjacent test lites should a break occur during the test.during the test. Effect on induced stresses Effect on induced stresses that may alter its break-that may alter its break-safe characteristics.safe characteristics. Stable inclusions Stable inclusions that would have not caused field that would have not caused field breakage breakage begin the phase transformation begin the phase transformation during the during the heat soak test, but do not break and then the phase heat soak test, but do not break and then the phase change continues later in the field and causes change continues later in the field and causes breakage.breakage.


Laminated glassLaminated glass::

Laminated glass is a combination of two or more Laminated glass is a combination of two or more glass sheets laminated to one or more layers of glass sheets laminated to one or more layers of plastic film under high temperature and pressure. plastic film under high temperature and pressure. In case of breakage, laminated glass does not In case of breakage, laminated glass does not shatter into small pieces. It will break, but the shatter into small pieces. It will break, but the glass pieces remain bonded to the film.glass pieces remain bonded to the film.


OBC 2006 directly references Canadian Glass OBC 2006 directly references Canadian Glass Standard CAN/CGSB-12.1-MStandard CAN/CGSB-12.1-M9090 for for Tempered Tempered or Laminated Safety Glass or Laminated Safety Glass in connection with:in connection with:

Transparent doors and panels [3.3.1.18.(2)]Transparent doors and panels [3.3.1.18.(2)] Revolving doors [3.4.6.14.(1) and (3)]Revolving doors [3.4.6.14.(1) and (3)] Standards Applicable to Environmental Separators or Standards Applicable to Environmental Separators or

assemblies exposed to the exterior [Table 5.10.1.1.]assemblies exposed to the exterior [Table 5.10.1.1.] Glass doors and sidelights [9.6.6.2.(2)]Glass doors and sidelights [9.6.6.2.(2)] Glass used in windows and skylight [9.6.6.2.(1)]Glass used in windows and skylight [9.6.6.2.(1)] Glass in guards [9.8.8.7.(1)] Glass in guards [9.8.8.7.(1)] including balconies per including balconies per

9.8.8.1.(1)9.8.8.1.(1)

Safety Glass and the Safety Glass and the CodeCode

OBC 2006 references Canadian Glass OBC 2006 references Canadian Glass Standard Standard CAN/CGSB-12.1-M90 for CAN/CGSB-12.1-M90 for Tempered or Laminated Safety GlassTempered or Laminated Safety Glass by by reference to reference to CAN.CGSB-12.20-M89 CAN.CGSB-12.20-M89 Structural Design of Glass for Buildings Structural Design of Glass for Buildings

Design Basis for Glass [4.3.6.1 (1)]Design Basis for Glass [4.3.6.1 (1)] Structural Design of Glass [9.7.3.2.(1)]Structural Design of Glass [9.7.3.2.(1)]

……furtherfurther CAN/CGSB-12.20-MCAN/CGSB-12.20-M8989 2.1.1 “Applicable 2.1.1 “Applicable

Publications” references CAN/CGSB-12.1-M90Publications” references CAN/CGSB-12.1-M90

Safety Glass and Safety Glass and DesignDesign…and…and

CAN/CGSB-12.1-M90 for Tempered or Laminated CAN/CGSB-12.1-M90 for Tempered or Laminated Safety Glass includes test procedures to establish Safety Glass includes test procedures to establish if the glass conforms to “safety” requirements. if the glass conforms to “safety” requirements. Soft Impact-type tests require a 45.4 (100 lb) bag of lead Soft Impact-type tests require a 45.4 (100 lb) bag of lead shot be swung through an 1220 mm (4 ft) arc.shot be swung through an 1220 mm (4 ft) arc.

The written primarily for:The written primarily for: glazed exterior/interior passageway doors, storm glazed exterior/interior passageway doors, storm

(combination) doors, patio doors, shower and (combination) doors, patio doors, shower and bathtub doors and their enclosures bathtub doors and their enclosures ((extract from the CGSB 12.1 statement of purposeextract from the CGSB 12.1 statement of purpose))

It doesn’t mention Balcony Guard PanelsIt doesn’t mention Balcony Guard Panels The standards do not require the glass not break. The standards do not require the glass not break.

Tempered Glass - Tempered Glass - CanadaCanada

Glass doesn’t breakGlass doesn’t break

oror The 10 largest particles collected The 10 largest particles collected

within 5 min. of impact ≤ the mass of within 5 min. of impact ≤ the mass of 6500 mm6500 mm 2 2 (about 3 in. x 3 in.) (about 3 in. x 3 in.) of the of the original specimen original specimen

Tempered Glass – Test Tempered Glass – Test FailureFailure

Similar to the CGSB material Standards in Similar to the CGSB material Standards in USA Glass must meet ASTM C1048-04 USA Glass must meet ASTM C1048-04 Standard Specification for Heat-Treated Standard Specification for Heat-Treated Glass Kind HS, Kind FT Coated and Glass Kind HS, Kind FT Coated and Uncoated Kind FT (Fully Tempered)Uncoated Kind FT (Fully Tempered). .

ASTM C1048-04 references ANSI Z97.1 ASTM C1048-04 references ANSI Z97.1 2004 which has (basically) the same test. 2004 which has (basically) the same test.

No Prohibition on tempered glass breakageNo Prohibition on tempered glass breakage

Tempered Glass - USATempered Glass - USA

If tempered glass meets the requirements of If tempered glass meets the requirements of CAN/CGBS 12.1 M90 orCAN/CGBS 12.1 M90 orANSI Z97.1 2004ANSI Z97.1 2004

It is acceptable according to the 2006 Building It is acceptable according to the 2006 Building CodeCode

Acceptable GlassAcceptable Glass

But what about But what about Spontaneous Spontaneous Breakage?Breakage?

Principally caused by Nickel Sulphide (NiS) Principally caused by Nickel Sulphide (NiS) inclusionsinclusions

Not a new problem – goes back to 1940sNot a new problem – goes back to 1940s NiS is an abbreviation (not a chemical term) NiS is an abbreviation (not a chemical term)

Cause of Spontaneous Cause of Spontaneous Breakage?Breakage?

NickelNickel may be in: may be in: raw materials, raw materials, contamination from handling and storage, contamination from handling and storage, contamination from the fire brick in the contamination from the fire brick in the

furnaces. furnaces. SulfurSulfur is added to help eliminate bubbles is added to help eliminate bubbles

in a glass.in a glass.

A single gram of nickel can contaminate A single gram of nickel can contaminate thousands of tonnes of glass. thousands of tonnes of glass.

Where dose Where dose NiNiSS come come from?from?

Forms at different temperatures into Forms at different temperatures into different “phases”.different “phases”.

At higher temperatures, NiS forms an “At higher temperatures, NiS forms an “alphaalpha” ” phase and, at lower temperature, it forms a phase and, at lower temperature, it forms a slightly larger “slightly larger “betabeta” phase particle. ” phase particle.

Tempering glass can trap NiS in the “alpha” Tempering glass can trap NiS in the “alpha” phase. phase.

Nickel SulphideNickel Sulphide

Anywhere from a few months to a few Anywhere from a few months to a few years, NiS converts to the beta phaseyears, NiS converts to the beta phase


Beta particle is 2% to 4% larger than the alpha phase particle, it tries to expand causing microcracks at the edge of the particle.

If the glass is recovered the If the glass is recovered the characteristic “Double D” characteristic “Double D” pattern of breakage about a pattern of breakage about a NiS impurity may be seenNiS impurity may be seen


NOTE: If a glass panel includes NOTE: If a glass panel includes NiS impurities, it doesn’t mean NiS impurities, it doesn’t mean that the glass is doomed to break. that the glass is doomed to break.

The impurity size, location, and The impurity size, location, and other stresses: e.g. from wind other stresses: e.g. from wind load, and hard body impact all load, and hard body impact all contribute to possible glass contribute to possible glass suddenly shattering. suddenly shattering.

Building and Construction Authority Building and Construction Authority ((BCA) issued a communication Jan 10, BCA) issued a communication Jan 10, 2011 to 2011 to “Address Spontaneous “Address Spontaneous Shattering…..”Shattering…..”

July 1, 2011 - Tempered Glass no July 1, 2011 - Tempered Glass no longer permitted for use as a part or longer permitted for use as a part or whole of a safety barrier. Laminated whole of a safety barrier. Laminated glass must be used. glass must be used.

Tempered Glass - Tempered Glass - SingaporeSingapore

Spontaneous glass breakage has not been Spontaneous glass breakage has not been considered an issue in Vancouver, considered an issue in Vancouver, Calgary, Ottawa, New York City, or Calgary, Ottawa, New York City, or Boston.Boston.

Spontaneous glass breakage was a Spontaneous glass breakage was a recognized problem in Singapore and was recognized problem in Singapore and was resolved by requiring laminated glass in resolved by requiring laminated glass in balcony guard panels.balcony guard panels.

Design for guard loads based on the Design for guard loads based on the International Building Code (IBC) coming International Building Code (IBC) coming into use in U.S. jurisdictions calls for a into use in U.S. jurisdictions calls for a “Factor of Safety of 4”“Factor of Safety of 4”

Other Jurisdictions… Other Jurisdictions…

Vary depending on:Vary depending on: How glass is incorporated into the How glass is incorporated into the

guard designguard design Where glass is on the buildingWhere glass is on the building What “traffic” or “occupancy” is belowWhat “traffic” or “occupancy” is below

Regulatory gap between design for Regulatory gap between design for the guard and consequences of the guard and consequences of something falling from the building something falling from the building

Consequences and Consequences and RisksRisks

Variety of Variety of opinionopinion Acceptable breakage ranges from frequency of Acceptable breakage ranges from frequency of

1:100 to 1:10,000 panels. 1:100 to 1:10,000 panels. GRG settled on 2/1000 as a threshold for a single GRG settled on 2/1000 as a threshold for a single

building supply of tempered panels. building supply of tempered panels.

Variety of Variety of consequences and risksconsequences and risks

Acceptable Breakage Acceptable Breakage RatesRates

Canadian / USA standards do not address Canadian / USA standards do not address risk despite an apparent the risk despite an apparent the public public imperative that:imperative that:

Glass guard panels should only be used in a Glass guard panels should only be used in a manner that provides no risk of injury or damage manner that provides no risk of injury or damage on shattering.on shattering.

Why? ….Why? ….The cost for 100% safety may be prohibitive or may The cost for 100% safety may be prohibitive or may eliminate glass guards. eliminate glass guards.

…….so …. What about existing buildings?.so …. What about existing buildings?

What is the acceptable What is the acceptable riskrisk

Reduced risk over timeReduced risk over time

So what do we do with So what do we do with all this information?all this information?

The Panel’s mandate was to make recommendations on whether and how the Building Code may be amended to address the problem of the breakage of balcony glass and its risk to persons nearby. It was not the mandate of the Panel to make findings of fault or assign blame.

The Panel included approximately 25 individuals with representatives from all key stakeholder organizations. Stakeholder interests represented on the panel included: engineering consultants; building code consultants; developers and contractors; professional designers; municipal building departments; the insurance sector (Tarion Warranty Corporation and the insurance provider for Architects); codes and standards (National Building Code and the Canadian Standards Association).

MMAH Expert PanelMMAH Expert Panel

Amendment to OBC 2006 Division BAmendment to OBC 2006 Division B

3.1.20. Glass in Guards3.1.20. Glass in Guards3.1.20.1 Glass3.1.20.1 Glass

(1)(1) Except as provided in Article 3.3.4.7., glass Except as provided in Article 3.3.4.7., glass in guards shall conform to Supplementary in guards shall conform to Supplementary Standard SB-13Standard SB-13

Sentence 3.3.4.7.(1) … is revoked and Sentence 3.3.4.7.(1) … is revoked and substituted assubstituted as

(1)(1) Stairs, handrails and interior guards within a Stairs, handrails and interior guards within a dwelling unit shall conform to the dwelling unit shall conform to the appropriate requirements in Section 9.8appropriate requirements in Section 9.8

MMAH SB-13 MMAH SB-13

MMAH SB 13 effective July 1, 2012MMAH SB 13 effective July 1, 2012


4.1.5.1. Glass in Guards4.1.5.1. Glass in Guards3.1.20.1 Glass3.1.20.1 Glass

(1)(1) Except as provided in Article 3.3.4.7., glass Except as provided in Article 3.3.4.7., glass in guards shall conform to Supplementary in guards shall conform to Supplementary Standard SB-13Standard SB-13

Sentence 3.3.4.7.(1) … is revoked and Sentence 3.3.4.7.(1) … is revoked and substituted assubstituted as

(1)(1) Stairs, handrails and interior guards within a Stairs, handrails and interior guards within a dwelling unit shall conform to the dwelling unit shall conform to the appropriate requirements in Section 9.8appropriate requirements in Section 9.8


Two methods are employed to establish load. Two methods are employed to establish load.

1.1.CalculationCalculation of the wind load according to the procedure of the wind load according to the procedure given in Part 4 of Division B of the Building Code. given in Part 4 of Division B of the Building Code. This could This could result in a very conservative combined wind and guard loadresult in a very conservative combined wind and guard load. .

2.2.Estimates using a wind tunnel studyEstimates using a wind tunnel study. Wind tunnel results . Wind tunnel results could provide lower wind load for the overall structure and could provide lower wind load for the overall structure and extreme wind loading at the building edges. extreme wind loading at the building edges.

3.3.There are a arguments from other jurisdictions that support There are a arguments from other jurisdictions that support the practice of employing guard and wind loads the practice of employing guard and wind loads independently. independently.

The panel agreed that, due to the divergent views amongst The panel agreed that, due to the divergent views amongst designers on consideration of guard and wind loads, designers on consideration of guard and wind loads, clarification of the Building Code requirements is necessaryclarification of the Building Code requirements is necessary. .

What about wind? …What about wind? …

Part 4 Design Requirements [ref 4.1.1.3. (1)]Part 4 Design Requirements [ref 4.1.1.3. (1)]BuildingsBuildings and their and their structural members structural members and and connections, including formwork and connections, including formwork and falsework shall be designed to have falsework shall be designed to have sufficient structural capacity and structural sufficient structural capacity and structural integrity to safely and effectively resist all integrity to safely and effectively resist all loads, effects of loads and influences that loads, effects of loads and influences that may reasonably be expected, having regard may reasonably be expected, having regard to the expected service life of to the expected service life of buildingsbuildings, and , and shall in any case satisfy the requirements of shall in any case satisfy the requirements of this section. this section.

Structural DesignStructural Design

Part 4 Specified Loads and EffectsPart 4 Specified Loads and Effects Table 4.1.2.1.A lists the loads applicable Table 4.1.2.1.A lists the loads applicable

including:including: (D) dead(D) dead (E) earthquake(E) earthquake (H) permanent(H) permanent (L) live(L) live (P) prestress effects(P) prestress effects (S) variable snow, ice, and rain(S) variable snow, ice, and rain (T) effects of temperature, shrinkage, moisture, creep, (T) effects of temperature, shrinkage, moisture, creep,

etc.etc. (W) wind (W) wind {{as specified in subsection 4.1.7}as specified in subsection 4.1.7}

Structural DesignStructural Design

• 4.1.7 Wind Load4.1.7 Wind Load

4.1.7.1.(1) the specified external pressure or suction 4.1.7.1.(1) the specified external pressure or suction due to wind on part or all of a surface of a building due to wind on part or all of a surface of a building can be calculated using the following formula:can be calculated using the following formula:

p = Ip = IwwqCeCgCpqCeCgCp

Where:Where:• IwIw: : importance factorimportance factor [Table 4.1.7.1]. [Table 4.1.7.1].• qq = 1/50 = 1/50 wind pressurewind pressure [e.g. for Toronto 0.52 kN] [e.g. for Toronto 0.52 kN]• CeCe: : exposure factor exposure factor based on height in “open” city based on height in “open” city

terrain [(h/10)terrain [(h/10)0.20.2], [4.1.7.1.(5)(a)], and], [4.1.7.1.(5)(a)], and• CgCg: : gust factor gust factor [2.5] [4.1.7.1.(6)(b)] [2.5] [4.1.7.1.(6)(b)] • CpCp: unknown : unknown but may be a net pressure factor but may be a net pressure factor (Cpnet)(Cpnet)

4.1.7 - Wind Load 4.1.7 - Wind Load DesignDesign

• Guard (Live) LoadGuard (Live) Load: : [ref 4.1.5.15] Loads on Guards[ref 4.1.5.15] Loads on Guards Design Load Design Load => 0.5 kN (over 100 mm x 100 mm area => 0.5 kN (over 100 mm x 100 mm area

to produce the most critical effect)to produce the most critical effect) [4.1.5.15.(2)] [4.1.5.15.(2)] IssuesIssues

No test procedure or pass/fail criteria is referencedNo test procedure or pass/fail criteria is referenced Is this an impact load?Is this an impact load? Is it a sustained load?Is it a sustained load? What allowable deformation, permanent set, or What allowable deformation, permanent set, or

cracking?cracking? What is the failure criteria? What is the failure criteria? Is it even a “test” criteria or just design parameter?Is it even a “test” criteria or just design parameter? How does it relate to the CGSB 12.1 soft impact load?How does it relate to the CGSB 12.1 soft impact load?

Design Loads on Guard Design Loads on Guard PanelsPanels

4.1.3.2. Strength and Stability4.1.3.2. Strength and Stability

(1)(1)a building and its a building and its structural componentsstructural components shall be shall be designed to have sufficient strength and stability designed to have sufficient strength and stability so that the factored resistance is greater or equal so that the factored resistance is greater or equal to the effect of the factored loads.to the effect of the factored loads.

(2)(2) the effect of factored loads … shall be the effect of factored loads … shall be determined in accordance with the load determined in accordance with the load combination cases listed in Table 4.1.3.2.combination cases listed in Table 4.1.3.2.

– Case 4 from [0.5LL + 1.4W] would most Case 4 from [0.5LL + 1.4W] would most commonly apply but designers also need to commonly apply but designers also need to

– check Case 2 [1.5LL + 0.4W].check Case 2 [1.5LL + 0.4W].

Load Combinations Load Combinations

Recall that Table 4.1.2.1.A states: Recall that Table 4.1.2.1.A states: (W) wind (W) wind {as specified in subsection 4.1.7}{as specified in subsection 4.1.7} But … is 4.1.7 entirely applicable? But … is 4.1.7 entirely applicable?

Wind Load Design Wind Load Design conflicting Requirements conflicting Requirements

Wind Load + Live Load + Combination Wind Load + Live Load + Combination Loads Loads [OBC 2006 4.1.7. + 4.1.3.2. + 4.1.5.15] for a [OBC 2006 4.1.7. + 4.1.3.2. + 4.1.5.15] for a 40-storey building in Toronto with 1 m x 1 m 40-storey building in Toronto with 1 m x 1 m glass panels reasonably long balconies glass panels reasonably long balconies yields:yields:

Approx. 4.3 kN/mApprox. 4.3 kN/m2 2 … …

.. Or about 1,000 lb on that panel.. Or about 1,000 lb on that panel

Seems a little excessive…Seems a little excessive…

What’s the Math? What’s the Math?

The The design of glass is also specifically referenced design of glass is also specifically referenced in 4.3.6.1(1). in 4.3.6.1(1). ““Glass used in buildings shall be designed in Glass used in buildings shall be designed in

conformance with conformance with CAN/CGSB-12.20-M(89), CAN/CGSB-12.20-M(89), “Structural “Structural Design of Glass for Buildings”. Design of Glass for Buildings”.

CAN/CGSB-12.20 includes:CAN/CGSB-12.20 includes: (D) dead(D) dead (L) live load including snow, rain, hydrostatic pressure, use (L) live load including snow, rain, hydrostatic pressure, use

and occupancy, inertia loads including impactand occupancy, inertia loads including impact (Q) live load due to wind, stack effect and earthquake or (Q) live load due to wind, stack effect and earthquake or

altitudealtitude (T) effects of temperature, shrinkage, moisture, creep, etc.(T) effects of temperature, shrinkage, moisture, creep, etc.

Design for GlassDesign for Glass

CAN/CGSB-12.20 also contains load factors: CAN/CGSB-12.20 also contains load factors: [L= live load] [L= live load] ααLL = 1.25, = 1.25, [Q = wind load] [Q = wind load] ααQQ = 1.5, = 1.5, [T = temperature effects][T = temperature effects] ααTT = 1.25,. = 1.25,.

And… reduction factor (ψ) for load combinations And… reduction factor (ψ) for load combinations that “that “reflects the improbability of maxima of reflects the improbability of maxima of different load effects occurring simultaneously, different load effects occurring simultaneously, and shall be taken as follows:and shall be taken as follows:”” When only one of L,Q, and T acts, ψ = 1.00 When only one of L,Q, and T acts, ψ = 1.00 When two of L,Q, and T act, ψ = 0.70When two of L,Q, and T act, ψ = 0.70 When all When all of L,Q, and T act, ψ = 0.60of L,Q, and T act, ψ = 0.60

Design for GlassDesign for Glass

= α= αDDD + Iw ψ [αD + Iw ψ [αLLL + αL + αqqQ + αQ + αTTT ]T ]• How Are Gusts, Exposure, Geometry…. included in Q (W)…? How Are Gusts, Exposure, Geometry…. included in Q (W)…?

Load factors are not the same as that given Load factors are not the same as that given in the 2006 Building Code in the 2006 Building Code (and could result in different factored loads)(and could result in different factored loads). .

Thus, there is an inherent conflict in the Thus, there is an inherent conflict in the two references in the building code that two references in the building code that requires resolution. requires resolution.

……..Lots of work to do to reconcile the ..Lots of work to do to reconcile the design of glass in the code and standardsdesign of glass in the code and standards

What’s the Math? What’s the Math?

MMAH SB 13 dealt with spontaneous MMAH SB 13 dealt with spontaneous glass breakage in balcony guardsglass breakage in balcony guards

By-pass GuardsBy-pass Guards Near edge mounted GuardsNear edge mounted Guards Slab mounted GuardsSlab mounted Guards

MMAH did not clarify wind load MMAH did not clarify wind load requirements and live load requirements requirements and live load requirements related to Guard panels.related to Guard panels.

MMAH did not resolve conflicts between MMAH did not resolve conflicts between OBC and CGSB glass design for guard OBC and CGSB glass design for guard panelspanels

Where does that lead Where does that lead us? us?

CSA Standard A500 for Building Guards CSA Standard A500 for Building Guards is in the works. is in the works.

Consensus standards process using Consensus standards process using expertise from the industry expertise from the industry

Can be referenced by designers and the Can be referenced by designers and the Building Code.Building Code.

Currently on 4Currently on 4thth draft of an evolving draft of an evolving standard. standard.

Hopes to address building guards of Hopes to address building guards of various materials and provide various materials and provide recommended maintenance guidelines.recommended maintenance guidelines.

The next step….The next step….

It is necessary to conduct It is necessary to conduct specialized testing for specialized testing for development of the development of the appropriate formula for appropriate formula for wind load:wind load:

p = Ip = Iwwq Ce [CgCpq Ce [CgCpnetnet]]

What is actual net load on What is actual net load on the guard?the guard?How does it vary at different How does it vary at different locations on the building?locations on the building?

Requires research….Requires research….

How does the How does the netnet wind load on wind load on guards vary at guards vary at different locations different locations on the building?on the building?

Requires research….Requires research….

???

Questions and Discussion????Questions and Discussion????

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