Deflections for Shoring for Historical Brick Wall Facade 1

[msquared48]

Got a project where I have to design a temporary steel shoring truss for an existing two story brick wall that is to be saved. The existing structure is to be demolished and a new building built that will incorporate the original brick wall facade.

My question is, as it is temporary shoring for a histiorical element, what deflection limitations would you use for the lateral design forces parallel to and orthoginal to the wall?

10' first story height, 8 foot second, with a four foot parapet. The wall will be temporarilly shored for vertical loads in the window openings with wood studs.

L/600?
L/1000?
Something else since it is a Historic Structural element?



Mike McCann
MMC Engineering

 

[dik]

Mike:

When I did the facade shoring for the Cornwall Centre in Regina, I used l/900 as a criteria... there were no guidelines at the time. Minimum would be l/720 as typical for stud supported masonry walls.

Dik

 

[JAE]

"Historical" brick? If it is truly old, historical brick it will probably have a much higher lime content in the mortar and thus be a much more ductile masonry wall system than modern day masonry. With that, the concept of L/600 probably doesn't apply as readily as it does to today's more rigid, brittle brick.

If you don't know the mortar, ductility, etc. of the wall then better to play it safe and goe with L/600 or such. But it probably has a higher tolerance for movement than you think.

 

[msquared48]

Well, it's seen three earthquakes in the last 62 years over 6.4 and it is still standing. What can I say?

Perhaps that's why it's "historical".

Then again, could it be the fact that that kind of "Architecture" is "history"?

I need to visit the site next week. If I get a chance, I'll post a picture of the facade - for what it's worth.

Mike McCann
MMC Engineering

 

[paddingtongreen]

The deflection of the truss may not be the main deflection problem. The method and sequence of transferring the load from the existing support matters more. Temporary trusses usually must be outside of the envelope of both the existing and future supports and practicality calls for two trusses, one inside and one outside, with short beams between.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[msquared48]

Yep. That's the setup.

Mike McCann
MMC Engineering

 

[SLTA]

Mike, the folks at Robert Silman Associates in NYC did that exact thing with Sage Hall at Cornell, while I was there. Maybe they'd be willing to chat about what they used. That whole crowd is into historic preservation, so I bet it would be quite a discussion.

 

[msquared48]

Since this is a temporary structure, does anyone see any code problems with classifying this as either a three directional space frame, or a three directional braced frame to simplify the connections?

Mike McCann
MMC Engineering