Tilt-up walls on 1960's building leaning out

[EngineerofSteel]

I have a package to bid on repairs to wood trusses on three wharehouses.

A previous engineer designed repairs to the trusses. I generally like what he did. But, I noted that he did not address a lack of lateral bracing on the trusses.

My main concerns are these:

1. One of the buildings has two concrete tilt-up walls leaning out. The contractor tells me, "These cannot be fixed and will remain that way." How can these be repaired? My job is only to design repairs for the wood trusses. If I do this, and the walls fail three years from now (unlikely), what is my liability? Should I specifically note in drawings that the scope is limited to the trusses?

2. Some of the trusses have no damage at all. If the damaged trusses are repaired, should the undamaged trusses be strengthened as well?

3. Some of the worst damage was caused by a 12" diameter water line installed as an addition in later years to meet fire code. It was placed on top of the bottom chord, near the outer wall, at the end of the truss. My first thought is that the load should be transferred to the top of the top chord... But, should this be moved directly into the wall with brackets?

 

[msquared48]

The walls leaning out concern me too... can you post any pictures or mention a scale of the lateral displacement?

The things that concerns me are two of the possible options here:

1. A failure of the tie mechanism of the concrete walls to the wood diaphragm ( the 200#/ft lateral tie requirement), or

2. A diaphragm chord tie failure due to seismic load.

Either case could be critical in another event. You do need to doeument this in writing. Has the local building official been notified? You do need to do your due dilligence here and stir the pot. Public safety is of tanamount importance here.

Both can be repaired, but the wall may not be able to be put back into the vertical position. The wall should be analyzed for this too though.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[EngineerofSteel]

Thanks, Mike.

The displacement is at a joint, so that two panels are moving outward at the top of the panels. The maximum is about 8 inches. The walls are 20' high.

 

[hokie66]

That's big, and should not be allowed to stay that way. But we would need a lot more information in order to give advice.

 

[msquared48]

I agree with Hokie here, and an additional concern is that if the 8" deflection is only exhibiting itself on one side of the structure, then the failure is at an interior connection. It needs to be identified and repaired.

How did the trusses fail?



Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[EngineerofSteel]

The trusses have failed primarily in two ways:

First, the 12" water line dead load actually broke the bottom chord in one truss. The top chord followed.

The second, more common damage results from a very slight pitch, looks like 1 in 12 or less (will measure if I get the work). Eventually, ponding started, and trusses below the ponds have failed- primarily, diagonal splitting in the bottom and top chords.

Tilt-ups:

The walls that lean are just 10 feet from the adjacent building. Access from the outside (to push into alignment) will not be possible. Access from the inside is available; the inside is 100-ft clear span beneath the trusses.

 

[hokie66]

You still haven't told us why the wall panels are leaning. Are they bent or broken? Do you know why? How are they connected at the base?

 

[dik]

And more interesting... how are they connected at the top? You may have a seriously dangerous condition if they are leaning that far...

Dik