Ruling No.: 20-15-1566
Application No.: B-2020-08
BUILDING CODE COMMISSION
IN THE MATTER OF Subsection 24(1) of the Building Code Act, S.O. 1992, c. 23, as amended.
AND IN THE MATTER OF Sentence 1.2.1.1.(1) of Division A, Sentences 4.1.3.2.(1) and (2), Table 4.1.3.2.A, Article 4.1.5.14., and Sentence 4.3.6.1.(1) of Division B, and Clause 2.1.1.1.(1)(b) of Division C of Regulation 332/12, as amended, (the “Building Code”).
AND IN THE MATTER OF an application by Keith B. Oster, for the resolution of a dispute with Frank Bidin, Chief Building Official, to determine whether the alternative solution proposed for the design of glass guards installed without a top rail, in a four storey, Group D major occupancy building, provides sufficiency of compliance with Sentence 1.2.1.1.(1) of Division A, Sentences 4.1.3.2.(1) and (2), Table 4.1.3.2.A, Article 4.1.5.14., and Sentence 4.3.6.1.(1) of Division B, and Clause 2.1.1.1.(1)(b) of Division C of the Building Code at 100 Citigate Drive, Ottawa, Ontario.
APPLICANT Keith B. Oster
Tal-CO Building Innovations Ltd
Ottawa, Ontario
RESPONDENT Frank Bidin
Chief Building Official
City of Ottawa
Ottawa, Ontario
PANEL Stephen Wong
Rick Mori
Andrew Steen
PLACE via telephone conference
DATE OF HEARING August 11, 2020
DATE OF RULING August 11, 2020
APPEARANCES Keith B. Oster
Tal-CO Building Innovations Ltd
Ottawa, Ontario
The Applicant
Brian Van Bussel
Associate
Entuitive Corporation
Toronto, Ontario
Agent for the Applicant
Kevin Wheaton
Building Engineer
City of Ottawa,
Ottawa, Ontario
Designate for the Respondent
Richard Ashe
Manager, Permit Approvals
City of Ottawa
Ottawa, Ontario
Designate for the Respondent
RULING
1. Particulars of Dispute
The Applicant has received an Order to Comply under the Building Code Act, 1992, to remedy certain alleged deficiencies at the building located at 100 Citigate Drive, Ottawa, Ontario.
The subject building is a new four storey, Group D major occupancy building. The Applicant submitted that the building area (with Test Facility included) is 2,392 m2 while the Respondent submitted the building area is 1815 m2. The building is comprised of non-combustible construction. It is equipped with a sprinkler system, standpipe and hose system, and fire alarm system.
Multiple free-standing glass guards were installed in the subject building. Free-standing glass guards are required to be capped by a rail which is continuous over two or more panels, as per CAN/CGSB-12.20-M, “Structural Design of Glass for Buildings”, which is adopted by reference in the Building Code. The guards in question were installed without a top rail.
The construction in dispute centers on whether the alternative solution proposed for the design of glass guards installed without a top rail in the subject building provides sufficiency of compliance with Sentence 1.2.1.1.(1) of Division A, Sentences 4.1.3.2.(1) and (2), Table 4.1.3.2.A, Article 4.1.5.14., and Sentence 4.3.6.1.(1) of Division B, and Clause 2.1.1.1.(1)(b) of Division C of the Building Code (“the Code”).
At the outset of the hearing, the Commission advised the parties that as per its mandate outlined in Section 24(1) of the Building Code Act, the Commission may only determine disputes concerning sufficiency of compliance with the technical requirements of the Building Code. As such, the Commission advised that Clause 2.1.1.1.(1)(b) of Division C of the Building Code, which was raised by the parties as a matter in dispute, is an administrative provision of the Building Code and not a technical provision, and therefore, is not within the jurisdiction of the Commission to determine. Upon agreement by the parties, this provision of the Code was removed from the dispute before the Commission.
2. Provisions of the Building Code in Dispute
Division A, Sentence 1.2.1.1.(1) Compliance with Division B
(1) Compliance with Division B shall be achieved,
(a) by complying with the applicable acceptable solutions in Division B, or (See Appendix A.)
(b) by using alternative solutions that will achieve the level of performance required by the applicable acceptable solutions in respect of the objectives and functional statements attributed to the applicable acceptable solutions in MMAH Supplementary Standard SA-1, “Objectives and Functional Statements Attributed to the Acceptable Solutions”. (See Appendix A.)
Division B, Article 4.1.3.2. Strength and Stability
(1) A building and its structural components shall be designed to have sufficient strength and stability so that the factored resistance, ΦR, is greater than or equal to the effect of factored loads, which shall be determined in accordance with Sentence (2).
(2) Except as provided in Sentence (3), the effect of factored loads for a building or structural component shall be determined in accordance with the requirements of this Article and the following load combination cases, the applicable combination being that which results in the most critical effect:
(a) for load cases without crane loads, the load combinations listed in Table 4.1.3.2.A., and
(b) for load cases with crane loads, the load combinations listed in Table 4.1.3.2.B.
(See Appendix A.)
Division B, Table 4.1.3.2.A Load Combinations without Crane Loads for Ultimate Limit States
Forming Part of Sentences 4.1.3.2.(2) and (5) to (10)
Case
Load Combination(1)
Principal Loads
Principal Loads
1
1.4D(2)
2
(1.25D(3) or 0.9D(4)) +1.5L(5)
1.0S(6) or 0.4W
3
(1.25D(3) or 0.9D(4)) +1.5S
1.0L(6)(7) or 0.4W
4
(1.25D(3) or 0.9D(4)) +1.4W
0.5L(7) or 0.5S
5
1.0D(4) + 1.0E(8)
0.5L(6)(7) + 0.25S(6)
Division B, Article 4.1.5.14. Loads on Guards (See Appendix A.)
(1) The minimum specified horizontal load applied outward at the minimum required height of every required guard shall be,
(a) 3.0 kN/m for open viewing stands without fixed seats and for means of egress in grandstands, stadia, bleachers and arenas,
(b) a concentrated load of 1.0 kN applied at any point for access ways to equipment platforms, contiguous stairs and similar areas where the gathering of many people is improbable, and
(c) 0.75 kN/m or a concentrated load of 1.0 kN applied at any point, whichever governs for locations other than those described in Clauses (a) and (b).
(2) Individual elements within the guard, including solid panels and pickets, shall be designed for a load of 0.5 kN applied over an area of 100 mm by 100 mm located at any point in the element or elements so as to produce the most critical effect.
(3) The loads required in Sentence (2) need not be considered to act simultaneously with the loads provided for in Sentences (1) and (4).
(4) The minimum specified load applied vertically at the top of every required guard shall be 1.5 kN/m and need not be considered to act simultaneously with the horizontal load provided for in Sentence (1).
(5) For loads on handrails, refer to Sentence 3.4.6.5.(12).
Division B, 4.3.6.1. Design Basis for Glass
(1) Glass used in buildings shall be designed in conformance with,
(a) CAN/CGSB-12.20-M, “Structural Design of Glass for Buildings”, using an adjustment factor on the wind load, W, of not less than 0.75, or
(b) ASTM E1300, “Determining Load Resistance of Glass in Buildings”, using an adjustment factor on the wind load, W, of not less than 1.0.
(See Appendix A.)
3. Applicant’s Position
The Agent for the Applicant explained that the new 4 storey building was designed to include interior glass guards for the central atrium floor openings, located at the 2nd, 3rd and 4th floors. The glass guards are required to comply with the structural design requirements of Part 4 of the Code.
The Agent submitted that the guards were designed to be located at the edge of the openings with glass panels anchored at the floor level acting as cantilevered guards and that there was no top rail on the guards. The Agent submitted that the guards were approved as part of the building permit process but were subsequently not accepted during inspections.
The Agent submitted that an alternative solution was prepared to address the structural design of the ‘as-built’ guards but was not accepted by the municipality.
The Agent stated that the glass guards were designed by a structural engineer to support the required loads as specified in the Code. He indicated that the Code specifies that the design for glass in buildings is required to comply with CAN/CGSB-12.20-M, “Structural Design of Glass in Building”. This standard has specific requirements including the provision of a continuous metal rail located on the top of the glass guard. The Agent stated that as per Clause 1.2.1.1.(1)(b) of Division A of the Building Code, alternative solutions are permitted, and that alternative solutions are equivalent to acceptable solutions in Division B when alternative solutions achieve the level of performance required in respect of the objectives and functional statements attributed to the alternative solutions in MMAH Supplementary Standard SA-1, “Objectives and Functional Statements Attributed to the Acceptable Solutions”.
The Agent submitted that the glass guards have been designed to meet the loading requirements of Article 4.1.5.14. Loads on Guards and Article 4.3.6.1. Design Basis for Guards, meeting the objective and functional statements associated with these Articles of the Code.
The Agent argued that in the proposed alternative solution, the cantilevered glass guards laminated with a stiff interlayer meet the performance required by the Code, as the guards will exhibit obvious cracking of the glass but will remain in place, if they are subjected to loads in excess of the specified design loads.
The Agent stated that CAN/CGSB-12.20-M, as referenced by Division B Sentence 4.3.6.1.(1) of the Code, was written in 1989 with the assumption that typical single lite glass balustrades were used. In such case, the Agent argued that a top rail would be required to provide for redundancy in the event of glass breakage where the top rail will provide continuity across the opening created by the missing glass panel, allowing load transfer to the adjacent panels.
The Agent submitted that although the standard has since been withdrawn, it is still referenced in the Code. He indicated that there is a new glass standard, CSA A500-16 Building Guards, which represents industry best practices and accounts for advances in glass fabrication and design. He noted that this standard does not require a top rail for laminated glass balustrades with a stiff interlayer, although it has not been adopted by the Code.
The Agent submitted that as a result of approximately 30 glass failures in Toronto between 2010 and 2011, the Ministry of Municipal Affairs and Housing (MMAH) established an expert panel to make recommendations to address the breakage of glass and risk to persons nearby. As a result, the Code was amended in 2014 to require glass guards to comply with MMAH Supplementary Standard SB-13, “Glass in Guards”. The Agent stated that the panel had noted that the breakage primarily occurred in tempered glass. The Agent submitted that this standard contains prescriptive requirements for the location of glass guards with respect to the distance inward and outward from the edge of the floor, depending on the type of glass and treatment of the glass. He maintained that this standard specified that laminated glass is to be designed, fabricated and installed so that in the event of failure, the glass does not dislodge from the supporting frame.
The Agent maintained that in this case, a laminated glass guard, selected for its strength and superior post-breakage performance, has been installed. The Agent stated that laminated glass has a lower probability of breakage than monolithic lites since surface flaws are less likely to occur at the same location in multiple lites. The Agent contended that the stiff interlayer provides redundancy and retention which goes above and beyond the requirements in CAN/CGSB-12.20-M.
The Agent indicated that in the event of failure, the laminated glass may break, but will remain in place in the supporting frame due to the presence of a stiff interlayer holding the glass panels together and preventing it from falling down to lower levels.
The Agent submitted that the installed cantilevered glass guards have the following structural characteristics to meet the performance level required by the Code:
CAN/CGSB-12.20-M requires an importance factor commensurate with the proposed breakage rate to be greater than 1.00. In the most severe condition, the single lite resistance calculates to have an importance factor of 1.013, while the most common glass configuration of the guard calculates to have an importance factor of 1.077
The subject cantilevered glass guard is laminated with a stiff interlayer and will remain in place and retain partial stiffness even after cracking, while providing a visual indication to all building occupants that the guard is damaged. The failure mode of tempered glass is to shatter into multiple pieces leaving a gap in the guard.
The building manager will take actions to prevent building occupants from leaning on the damaged glass guard including:
o advising staff to immediately report any damage to glass,
o posting a warning notice to avoid persons leaning on the glass guard,
o installing a pre-engineered steel temporary top cap, which will meet the alternative load path requirements of CAN/CGSB-12.20-M, and
o replacing the guard.
In response to the Commission’s questions, the Agent confirmed that the design of the glass guards included various standards not referenced by the Code.
In response to Commission questions regarding Sentence 4.1.3.2.(1) of Division B of the Code, which requires structural members to be designed such that the factored resistance is equal to or greater than the effect of the factored loads, the Agent advised that the calculations used for the alternative solution included reduced loading. The Agent explained that the use of reduced loading for the calculations was based on their opinion that a breakage in the glass guard would be a “rare event”. The Agent argued that, per their submitted document titled “Glass Guard Alternative Solution Revision 01”, National Building Code of Canada Commentary (NBCC) refers to an approach to reduce the “load factor for all variable live loads” in considering “the stability of an entire structure in a rare event”, and contended that the same approach can be followed for the design of the glass guards.
In response to the Commission’s questions concerning Sentence 4.1.5.14.(4) of Division B of the Code regarding loads applied vertically at the top of every required guard, the Agent agreed that this requirement would be applicable to the subject guards. The Agent indicated that the proposed alternative solution did not address specified loads applied vertically at the top of the guard as required by Sentence 4.1.5.14.(4) of the Code.
In summary, the Agent maintained that the installed laminated cantilevered glass guards without a top rail will provide an acceptable level of safety to the occupants of the building, as they have been designed for the required loads as per the Code. The Agent explained that the glass guard’s failure mode will enable it to remain in place with readily evident cracks. Further, the Agent maintained that calculations prove that the guard with the interior lite shattered is able to resist the loading prescribed by the Code with an importance factor that exceeds what is required by CAN/CGSB-12.20-M. The Agent concluded that any risk is further mitigated by the action plan by the building managers to immediately notify responsible persons of a damaged guard, post a warning notice, and install a prefabricated temporary top cap that will meet post-breakage requirements of CAN/CGSB-12.20-M until it is replaced.
4. Respondent’s Position
The Designate for the Respondent submitted that the free-standing (cantilevered) glass guards installed at the subject building are point fixed glass guards that are located beyond the floor edge. The glass guards are supported by a continuous shoe and are located less than 50 mm from the floor edge. He explained that all glass is fully tempered and none of the glass guards are capped by a continuous rail.
The Designate submitted that the glass guards do not comply with the requirements for strength and stability as per Sentences 4.1.3.2.(1) and (2), and Table 4.1.3.2.A. of the Code, nor do they comply with the Code’s restrictions on the type of glass to be used in guards, as per MMAH Supplementary Standard SB-13, Glass in Guards.
The Designate submitted that based on their proximity to the floor edge, MMAH Supplementary Standard SB-13 requires all glass balustrades to be heat-strengthened laminated glass. In this case, all the glass guards are constructed of fully tempered laminated glass and therefore, the glass guards do not comply with SB-13.
The Designate submitted that the Applicant’s alternative solution, along with previous correspondence, claim that compliance with CSA A500-16, which allows laminated glass guards that are not capped by a continuous rail, and compliance with the International Building Code would also achieve compliance with requirements of the Code. However, the Designate explained that compliance claims have been based on applying selective and favourable requirements from these standards and therefore, compliance cannot be achieved on this basis. Further, the Designate maintained that the Ottawa Building Code Services reviewed additional standards related to structural glass design and the subject guards were found not to comply with any of those standards.
The Designate submitted that the Applicant’s claims that the design of the guards is based on modern structural glass design methods and standards. The Designate submitted that modern structural glass design requires fail-safe design and redundancy for fall-through protection. CAN/CGSB-12.20-M embodies fail-safe design and redundancy for fall-through protection and further, this standard remains current with modern structural glass design. Because these criteria have not been met, the Designate submitted that the alternative solution does not comply with this standard.
The Designate submitted that the Applicant’s position is that the redundant strength equal to half the specified live load is sufficient. The Designate noted that the redundant strength of a laminated structural glass assembly is its capacity with one glass ply broken. Fail-safe design of glass guards requires redundant strength of at least 1.5L. The Designate argued that the Applicant has determined that the glass guards have redundant strength of only half the specified live load (0.5L). The Designate maintained that no reference or standard suggests that redundant strength of half the specified live load is safe. Given the shortfall of redundant strength, moderate live loads may lead to progressive failure, collapse and fall-through. Further, failure mode of fully tempered laminated glass balustrades without redundant strength can occur without warning of collapse.
The Designate submitted that the Applicant’s position that a stiff interlayer ensures redundant strength is based upon promotional literature from the manufacturer. However, none of the referenced literature demonstrates redundant strength of glass balustrades. The literature provided demonstrates that some small measure of residual strength can be expected when all glass plies are broken. However, the Designate argued that residual strength is not the same as redundancy.
The Designate explained that the Applicant’s position is that the safety factor and the importance factor for glass breakage provided are adequate. The Designate indicated that to ensure an acceptable level of safety without fail-safe design and redundancy, the importance factor for glass breakage must be greater than 1.0 at ultimate limit state. The Designate submitted that the importance factor determined by the Applicant is much less than that would be required. Further, the Designate argued that the safety factor determined by the Applicant is based on an incorrect interpretation of resistance factor for glass which is stated clearly in CAN/CGSB-12.20-M to be 1.0.
The Designate stated that it is the Applicant’s position that the subject guards provide an acceptable level of safety. The Designate submitted that because the glass guards are not of a fail-safe design and do not possess redundant strength, failure and fall-through are 400 times more likely than the acceptable solution provided in the Code. The Designate maintained that probability of failure and fall-through could have been addressed by applying an importance factor of 2.7. In this case, the Designate submitted the importance factor provided is much lower than what would be required.
The Designate submitted that the factored stress of the balustrades according to the Applicant’s analysis, far exceeds the factored resistance. The Designate indicated that with one ply broken, the guards cannot resist the factored design load (1.5L at ultimate limit state) as required.
The Designate submitted that the Applicant has not presented an alternative means for the type of glass used to comply with MMAH Supplementary Standard SB-13 Glass in Guards. To comply with this standard, the Designate indicated that all balustrades would have to be removed, and the glass plies, if possible, would have to be separated, annealed, and re-tempered.
The Designate submitted that the Ottawa Building Code Services has asked the designer to confirm the resistance of the guards to vertical loads. As with all loads, the guards must resist the factored vertical load, 1.5L with one glass ply broken. The Designate submitted that to date the Applicant has not addressed this matter.
The Designate submitted that in previous correspondence with the Applicant, they had discussed mandatory test requirements for the alternative solution proposed by the Applicant’s engineer. A program of tests for static load resistance was previously proposed by the Applicant but those tests were not carried out.
In summary, the Designate submitted that the as-installed free-standing glass guards without a top rail do not comply with the Code. The Designate indicated that as the free-standing glass guards are not capped by a continuous top rail, contrary to the requirements of CAN/CGSB-12.20-M, an alternative solution was submitted and reviewed. The Designate maintained that an analysis of the alternative solution application confirms that the glass guards do not achieve the level of performance required by the Code, modern structural glass design methods, and all glass design standards referenced by the Applicant. The Designate explained that all the glass guards have been constructed using fully tempered laminated glass, which is contrary to the requirements of MMAH Supplementary Standard SB-13 and that the alternative solution does not address this issue. Further, the Designate maintained that there are no special circumstances in the subject building that would justify a performance level less than what is required by the Code.
5. Commission Ruling
It is the decision of the Building Code Commission that the alternative solution proposed for the design of glass guards installed without a top rail, in a four storey, Group D major occupancy building, does not provide sufficiency of compliance with Sentence 1.2.1.1.(1) of Division A, Sentences 4.1.3.2.(1) and (2), Table 4.1.3.2.A, Article 4.1.5.14., and Sentence 4.3.6.1.(1) of Division B of the Building Code at 100 Citigate Drive, Ottawa, Ontario.
- Reasons
i) Article 1.2.1.1.(1) of Division A of the Building Code permits the use of an alternative solution to achieve compliance with the acceptable solutions set out in Division B as long as the alternative solution achieves the level of performance required by the applicable acceptable solutions in respect of the objectives and functional statements attributed to the applicable acceptable solution.
Based on the evidence and arguments submitted by the parties, the Commission heard that the Applicant chose to use an alternative solution approach to achieve compliance with the acceptable solutions set out in Division B.
It is the Commission’s opinion that the parties were not disputing whether an alternative solution approach could be used, but rather whether the proposed alternative solution achieves the level of performance required by the acceptable solutions set out in Sentences 4.1.3.2.(1) and (2), Table 4.1.3.2.A, Article 4.1.5.14., and Sentence 4.3.6.1.(1) of Division B of the Building Code.
ii) Sentences 4.1.3.2.(1) and (2) of Division B of the Building Code requires structural members to be designed to have sufficient strength and stability so that the factored resistance is equal to or greater than the effect of the factored loads, and the effect of factored loads are to be determined by following load combinations which result in the most critical effect. For load cases without crane loads, the load combinations listed in Table 4.1.3.2.A. are to be followed. CAN/CGSB-12.20-M “Structural Design of Glass for Buildings” provides detailed method for calculations of the factored resistance as well as the factored loads.
The Commission heard evidence and testimony that the calculations in the alternative solution were performed with reduction in loading which deviates from requirements of the Code. The use of reduced loading for the calculations was based on the Applicant’s opinion that a breakage in the glass guard would be a “rare event”.
It is the Commission’s opinion that the analysis, which was based on reduced loading for a ”rare event”, does not provide sufficiency of compliance with Sentences 4.1.3.2.(1) and (2) and table 4.1.3.2.A. of Division B of the Building Code.
iii) Regarding loads on guards, Sentence 4.1.5.14.(4) of Division B of the Building Code states: “The minimum specified load applied vertically at the top of every required guard shall be 1.5 kN/m and need not be considered to act simultaneously with the horizontal load provided for in Sentence (1)”.
The Commission heard that the parties agree that this Sentence is applicable in this case. The ability of the free-standing guard to meet this requirement was not demonstrated.
Based on the evidence presented, the proposed alternative solution, having not satisfactorily addressed specified loads applied vertically at the top of the free-standing guards, does not achieve sufficiency of compliance with Sentence 4.1.5.14.(4).
iv) Sentence 4.3.6.1.(1) of Division B of the Building Code requires that glass used in buildings be designed in conformance with:
(a) CAN/CGSB-12.20-M, “Structural Design of Glass for Buildings”, using an adjustment factor on the wind load, W, of not less than 0.75, or
(b) ASTM E1300, “Determining Load Resistance of Glass in Buildings”, using an adjustment factor on the wind load, W, of not less than 1.0.
The Commission notes that the glass used in the as-installed free-standing guards is also required to meet the requirements of MMAH Supplementary Standard SB-13, Glass in Guards.
It is the Commission's opinion that the as-built free-standing guards, without the continuous top rail, do not meet the requirements set out in CAN/CGSB-12.20-M. The Commission is also of the opinion that the top rail, as required by this standard, provides a margin of safety for catastrophic failure of a free-standing glass guard, for which an equivalent degree of safety was not demonstrated.
Dated at the City of Toronto this 11th day in the month of August in the year 2020 for application number B-2020-08.
Stephen Wong, Chair
Rick Mori
Andrew Steen```