MMAH SB-13 WHY? HOW? WHAT NOW?

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1 MMAH SB-13 WHY? HOW? WHAT NOW? Gerald R. Genge, P.Eng., C.Eng., BDS, BSSO, C.Arb, Q.Med. Building Science Specialists Contract Administrators Reserve Fund Planners Consulting Engineers BUILDING CONSULTANTS Arbi tech ADR Arbitration, Mediation, Litigation Support for Engineering and Construction Disputes

2 Summer News Bulletin! 30 incidents of glass guard breakage in on 11 buildings in Toronto Breakage was primarily guard panels using tempered glass Earlier breaks were repaired without notice to the City Breakage became a public concern resulting in: news reports (CBC, City, etc.) industry magazine articles (US Glass - October 2011) CondoBusiness November 2011 parody (22-Minutes)

3 Action City of Toronto issues 9 (maybe more) Orders to Remedy Unsafe Building between December 2010 and August [now double that number] Developers of new condos order to have engineering assessments and design for remedial work. GRG engaged as Peer Review Consultant and examined reports from Consultants on 6 buildings Stakeholders became engaged in the issues Concerns about delayed construction Various means of problem resolution Owners of existing buildings questioning public safety Other issues started to arise regarding design

4 IL A R POST GLASS PANEL BALCONY SLAB

5 FLY-BY GUARD BY-PASS GUARD ANCHORAGE

6 SHATTERED GLASS PANEL

7 GLASS TO METAL CONTACT

8 DISENGAGED GLASS PANEL

9 GLASS TO GLASS CONTACT

10 INADEQUATE ANCHORAGE

11 Influence Circle Aesthetics Existing Standards Existing Regulatory Requirements Choices for Materials Design Construction

12 Types of Glass Float glass: Float glass is a sheet of glass made by floating molten glass, at a temperature of approximately 1200 C, on a bed of molten metal. Basic float glass is not a safety glass and is not used for balcony guards because it tends to break into large, jagged shards. However, it is the base material that is further processed into tempered glass and laminated glass.

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

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

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

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

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

18 Safety Glass and the Code OBC 2006 directly references Canadian Glass Standard CAN/CGSB-12.1-M90 for Tempered or Laminated Safety Glass in connection with: Transparent doors and panels [ (2)] Revolving doors [ (1) and (3)] Standards Applicable to Environmental Separators or assemblies exposed to the exterior [Table ] Glass doors and sidelights [ (2)] Glass used in windows and skylight [ (1)] Glass in guards [ (1)] including balconies per (1)

19 Safety Glass and Design and OBC 2006 references Canadian Glass Standard CAN/CGSB-12.1-M90 for Tempered or Laminated Safety Glass by reference to CAN.CGSB M89 Structural Design of Glass for Buildings Design Basis for Glass [ (1)] Structural Design of Glass [ (1)] further CAN/CGSB M Applicable Publications references CAN/CGSB-12.1-M90

20 Tempered Glass - Canada CAN/CGSB-12.1-M90 for Tempered or Laminated Safety Glass includes test procedures to establish if the glass conforms to safety requirements. Soft Impact-type tests require a 45.4 (100 lb) bag of lead shot be swung through an 1220 mm (4 ft) arc. The written primarily for: glazed exterior/interior passageway doors, storm (combination) doors, patio doors, shower and bathtub doors and their enclosures (extract from the CGSB 12.1 statement of purpose) It doesn t mention Balcony Guard Panels The standards do not require the glass not break.

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22 Tempered Glass Test Failure Glass doesn t break or The 10 largest particles collected within 5 min. of impact the mass of 6500 mm 2 (about 3 in. x 3 in.) of the original specimen

23 Tempered Glass - USA Similar to the CGSB material Standards in USA Glass must meet ASTM C Standard Specification for Heat-Treated Glass Kind HS, Kind FT Coated and Uncoated Kind FT (Fully Tempered). ASTM C references ANSI Z which has (basically) the same test. No Prohibition on tempered glass breakage

24 Acceptable Glass If tempered glass meets the requirements of CAN/CGBS 12.1 M90 or ANSI Z It is acceptable according to the 2006 Building Code

25 But what about Spontaneous Breakage?

26 Cause of Spontaneous Breakage? Principally caused by Nickel Sulphide (NiS) inclusions Not a new problem goes back to 1940s NiS is an abbreviation (not a chemical term)

27 Where dose NiS come from? Nickel may be in: raw materials, contamination from handling and storage, contamination from the fire brick in the furnaces. Sulfur is added to help eliminate bubbles in a glass. A single gram of nickel can contaminate thousands of tonnes of glass.

28 Nickel Sulphide Forms at different temperatures into different phases. At higher temperatures, NiS forms an alpha phase and, at lower temperature, it forms a slightly larger beta phase particle. Tempering glass can trap NiS in the alpha phase.

29 Nickel Sulphide Anywhere from a few months to a few years, 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.

30 Nickel Sulphide If the glass is recovered the If the glass is recovered the characteristic Double D pattern of breakage about a NiS impurity may be seen NOTE: If a glass panel includes NiS impurities, it doesn t mean that the glass is doomed to break. The impurity size, location, and other stresses: e.g. from wind load, and hard body impact all contribute to possible glass suddenly shattering.

31 Tempered Glass - Singapore Building and Construction Authority (BCA) issued a communication Jan 10, 2011 to Address Spontaneous Shattering.. July 1, Tempered Glass no longer permitted for use as a part or whole of a safety barrier. Laminated glass must be used.

32 Other Jurisdictions Spontaneous glass breakage has not been considered an issue in Vancouver, Calgary, Ottawa, New York City, or Boston. Spontaneous glass breakage was a recognized problem in Singapore and was resolved by requiring laminated glass in balcony guard panels. Design for guard loads based on the International Building Code (IBC) coming into use in U.S. jurisdictions calls for a Factor of Safety of 4

33 Consequences and Risks Vary depending on: How glass is incorporated into the guard design Where glass is on the building What traffic or occupancy is below Regulatory gap between design for the guard and consequences of something falling from the building

34 Acceptable Breakage Rates Variety of opinion Acceptable breakage ranges from frequency of 1:100 to 1:10,000 panels. GRG settled on 2/1000 as a threshold for a single building supply of tempered panels. Variety of consequences and risks

35 What is the acceptable risk Canadian / USA standards do not address risk despite an apparent the public imperative that: Glass guard panels should only be used in a manner that provides no risk of injury or damage on shattering. Why?. The cost for 100% safety may be prohibitive or may eliminate glass guards..so. What about existing buildings?

36 Reduced risk over time

37 So what do we do with all this information?

38 MMAH Expert Panel 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).

39 MMAH SB-13 Amendment to OBC 2006 Division B Glass in Guards Glass (1) Except as provided in Article , glass in guards shall conform to Supplementary Standard SB-13 Sentence (1) is revoked and substituted as (1) Stairs, handrails and interior guards within a dwelling unit shall conform to the appropriate requirements in Section 9.8

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

41 MMAH SB Glass in Guards Glass (1) Except as provided in Article , glass in guards shall conform to Supplementary Standard SB-13 Sentence (1) is revoked and substituted as (1) Stairs, handrails and interior guards within a dwelling unit shall conform to the appropriate requirements in Section 9.8

42 What about wind? Two methods are employed to establish load. Calculation of the wind load according to the procedure given in Part 4 of Division B of the Building Code. This could result in a very conservative combined wind and guard load. 1. Estimates using a wind tunnel study. Wind tunnel results could provide lower wind load for the overall structure and extreme wind loading at the building edges. 2. There are a arguments from other jurisdictions that support the practice of employing guard and wind loads independently. 3. The panel agreed that, due to the divergent views amongst designers on consideration of guard and wind loads, clarification of the Building Code requirements is necessary.

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

44 Structural Design Part 4 Specified Loads and Effects Table A lists the loads applicable including: (D) dead (E) earthquake (H) permanent (L) live (P) prestress effects (S) variable snow, ice, and rain (T) effects of temperature, shrinkage, moisture, creep, etc. (W) wind {as specified in subsection 4.1.7}

45 Wind Load Design Wind Load (1) the specified external pressure or suction due to wind on part or all of a surface of a building can be calculated using the following formula: p = IwqCeCgCp Where: Iw: importance factor [Table ]. q = 1/50 wind pressure [e.g. for Toronto 0.52 kn] Ce: exposure factor based on height in open city terrain [(h/10)0.2], [ (5)(a)], and Cg: gust factor [2.5] [ (6)(b)] Cp: unknown but may be a net pressure factor (Cpnet)

46 Design Loads on Guard Panels Guard (Live) Load: [ref ] Loads on Guards Design Load => 0.5 kn (over 100 mm x 100 mm area to produce the most critical effect) [ (2)] Issues No test procedure or pass/fail criteria is referenced Is this an impact load? Is it a sustained load? What allowable deformation, permanent set, or cracking? What is the failure criteria? Is it even a test criteria or just design parameter? How does it relate to the CGSB 12.1 soft impact load?

47 Load Combinations Strength and Stability a building and its structural components shall be designed to have sufficient strength and stability so that the factored resistance is greater or equal to the effect of the factored loads. (1) the effect of factored loads shall be determined in accordance with the load combination cases listed in Table (2) Case 4 from [0.5LL + 1.4W] would most commonly apply but designers also need to check Case 2 [1.5LL + 0.4W].

48 Wind Load Design conflicting Requirements Recall that Table A states: (W) wind {as specified in subsection 4.1.7} But is entirely applicable?

49 What s the Math? Wind Load + Live Load + Combination Loads [OBC ] for a 40-storey building in Toronto with 1 m x 1 m glass panels reasonably long balconies yields: Approx. 4.3 kn/m2.. Or about 1,000 lb on that panel Seems a little excessive

50 Design for Glass The design of glass is also specifically referenced in (1). Glass used in buildings shall be designed in conformance with CAN/CGSB M(89), Structural Design of Glass for Buildings. CAN/CGSB includes: (D) dead (L) live load including snow, rain, hydrostatic pressure, use and occupancy, inertia loads including impact (Q) live load due to wind, stack effect and earthquake or altitude (T) effects of temperature, shrinkage, moisture, creep, etc.

51 Design for Glass CAN/CGSB also contains load factors: [L= live load] αl = 1.25, [Q = wind load] αq = 1.5, [T = temperature effects] αt = 1.25,. And reduction factor (ψ) for load combinations that reflects the improbability of maxima of different load effects occurring simultaneously, and shall be taken as follows: When only one of L,Q, and T acts, ψ = 1.00 When two of L,Q, and T act, ψ = 0.70 When all of L,Q, and T act, ψ = 0.60

52 What s the Math? = αdd + Iw ψ [αll + αqq + αtt ] How Are Gusts, Exposure, Geometry. included in Q (W)? Load factors are not the same as that given in the 2006 Building Code (and could result in different factored loads). Thus, there is an inherent conflict in the two references in the building code that requires resolution...lots of work to do to reconcile the design of glass in the code and standards

53 Where does that lead us? MMAH SB 13 dealt with spontaneous glass breakage in balcony guards By-pass Guards Near edge mounted Guards Slab mounted Guards MMAH did not clarify wind load requirements and live load requirements related to Guard panels. MMAH did not resolve conflicts between OBC and CGSB glass design for guard panels

54 The next step. CSA Standard A500 for Building Guards is in the works. Consensus standards process using expertise from the industry Can be referenced by designers and the Building Code. Currently on 4th draft of an evolving standard. Hopes to address building guards of various materials and provide recommended maintenance guidelines.

55 Requires research. It is necessary to conduct specialized testing for development of the appropriate formula for wind load: p = Iwq Ce [CgCpnet] What is actual net load on the guard? How does it vary at different locations on the building?

56 Requires research. How does the net wind load on guards vary at different locations on the building?

57 ??? Questions and Discussion????