Cantilevered Glass Guard 1

[SkiisAndBikes]

I have a client who would like a cantilevered glass guard around the 2nd floor level of their boathouse (10 to 12 ft. height above grade/water level). Guard would be 1070 mm (42in.) high, no posts, no top/bottom rails. I have been shown examples of similar type rails installed by the glass supplier.

The applicable design standard in Canada is CGSB 12.20, Structural Design of Glass For Buildings. This standard requires "Any free standing glass guard shall be capped by a rail which is continuous over two or more lights. The glass guard shall resist the factored design load after failure of alternate lights."

I am questioning why there are so many existing cantilevered glass guards without top rails when it seems to be required by the design standard, or is my interpretation incorrect? I would welcome any thoughts/suggestions from persons who may have experince with similar type guards.

 

[dik]

How is the CGSB doc tied into the NBC? or what is the reason for using that standard? is there an exception to using design requirement?

This can e posted in the Glass Engineering Forum, too.

Dik

 

[SkiisAndBikes]

Dik,

I was looking in Part 4 at clause 4.3.6.1 of the Ontario Building Code (OBC) "Design Basis for Glass - (1) Glass used in buildings shall be designed in conformance with CAN/CGSB12.20-M, "Structural Design of Glass for Buildings"

With the glass, I am in somewhat unfamiliar territory and any suggestions are welcome. I will wait a few days before posting in the Glass Engineering forum (of which I browsed before posting).

Thanks

 

[connectegr]

In the US this is becoming more popular. We have designed several using basic engineering principals and published glass properties.

http://www.FerrellEngineering.com

 

[dik]

Does CGSB have any exclusions or limitations on the applicability of the requirement?

I've done glazing design using principles and properties as connectegr has...

Dik

 

[csd72]

You could always put the rail on and leave it up to client discretion to take it off.

Just a thought.

 

[connectegr]

Traditionally, glass served only as the infill. The top rail was connected to the walls at the end or created a closed continuous rail. These required little design, as they were catalog items with specific installation instructions. But, the new architect preference is a glass only handrail, with only a shoe at the base. In the first cases we were involved in, we required that the glass rails be physically load tested. And they performed surprisingly well. As I mentioned earlier, we have now designed several projects using basic engineering. In addition to designing the shoe or base connection, we design the cantilever glass panel for flexural strength and deflection. Our primary references are the Glass Association of North America and IBC Section 1607.7 and 2407. We have used laminated fully-tempered glass and laminated heat strengthened glass.

http://www.FerrellEngineering.com

 

[keenaseng]

In Australia, frameless cantilever glass balustrades used to be used alot until the standards changed and top rails were required (happened as a result of impact smashing the glass whilst someone was leaning on it). The idea for the top rail was to provide a backup if a single glass panel fails - ie. top rail will span to panel on either side to stop someone instantly falling out.

Perhaps could consider a laminated or double glass system where the front sheet could be sacrificial to any impact (ie. break) and the second panel of the laminate could still structurally take any short term load? This would go along the same logic as the top rail, except you are using glass panel as backup instead of a top rail...?