Glass Canopy (Seismic Loading)

[StrucPEng]

I am in the process of designing a point supported glass canopy in a high seismic area. The canopy support structure has been designed by others and the seismic design parameters used to design the steel support have been provided. My question is does anyone know of some good reference material (if it exists) for seismic loading on glass? In terms of a canopy, I am thinking the glass would be subject to mostly in-plane shear forces but would like other opinions.

Thanks

 

[NorthCivil]

There is no step by step engineering design guide for this situation. find some roughly relevant standards, make some assumptions, add a factor of safety, and away we go

 

[robyengIT]

in Italy we have this (but in Italian language). Free download :

https://www.cnr.it/it/node/2630

 

[glass99]

The usual thing in the US is we use the component (Fp) loads on glass as defined in ASCE 07. If you are looking at the glass itself, you generally use an R of 1.0 bc it has no ductility, though that is arguably conservative.

 

[StrucPEng]

Thanks, that makes sense, I am reading through section 13 of ASCE7 and the process seems to be reasonable.

 

[Agent666]

I'd think in most cases the glazing either has sufficient clearances to accommodate the seismic movements within the normal glazing setup or they are providing a separate seismic frame. Usually round these parts you tell them how much movement their frames need to take and they do the rest ensuring the glazing has sufficient isolation/clearances so that it doesn't take any in plane loads from the primary structure.

Seismic load on the glass only comes from its own self weight times whatever your seismic acceleration is at the level where its connected.

 

[StrucPEng]

That is usually how I tend to look at it for most seismic loads on glazing, as long as it can accommodate the movement it is generally ok. This situation is a bit different from what I have determined since it is point supported glass. Ultimately I am going with the seismic shear force as it relates to the anchors and support points not so much the glass panel itself (that load is relatively small compared to the wind loading). Chapter 13 of ASCE 7 has been pretty good in helping determine the loading so thanks for the help pointing to that.

 

[Agent666]

The holes they put in the glass even with 'spider' type connections are still over-sized to a degree to accommodate some relative movement/skewing/tolerance of the supporting points around the perimeter for in-plane loading. It might depend on the actual system being employed, but I've seen rubber type washers going into them that probably offer some limited ability to twist/slide/move/pivot without unduly loading or restraining the glass for in-plane loading. Given the size of the panels they might only need to accommodate a small proportion of the total drift which may be able to be handled by the connection to the glass or the connection components itself.

Often the facade guys have there own engineering guys on board, as complex facades often require specialist design, and structural considerations is only one piece of their pie. I would bet that they would be more than happy to help to a point with what can/cannot be achieved with their systems if it means they are in the running as a contender for securing the final job.