Wind Damage 1

[dauwerda]

This happened to the building I work at two nights ago in a wind/thunder storm. It happened at night while no one was here so no one was hurt. It's certainly not a good situation (could have been a lot worse), but I can't help but nerd out on reviewing the structural damage and see the failures happening as one might predict.

This is the front corner of the building that took the brunt of the damage. I would guess the garage doors (or framing around the smaller one) failing is what contributed to more of the major damage. The smaller door is part of the original building that was built in the 70's. The larger door is part of an addition that was finished about 6 months ago.

Yes, that is the larger door (24x16 I think) in the ceiling

A view looking back towards the large door opening.

This is just to the left of the previous view

 

[bones206]

Looks like the purlins were experiencing significant uplift.

The new addition purlins seem to be more closely spaced and have solid blocking/bridging. The older side purlins seems to have strap bridging.

 

[Kuhladula]

Agreed - Appears that the purlins experienced an excess of uplift after the overhead doors blew in. Knowing how most PEMBs are designed with cost in mind, I'm assuming that the building was designed as "Enclosed" with a GCpi of +/- 0.18 and should have been "Partially Enclosed" with a GCpi of +/- 0.55 if accounting for failed doors.

 

[dold]

In photos #3,4,5 - particularly in #5 - you can see the girder bottom flange experienced LTB from the huge uplift (at least that's what it looks like to me). Typically you'd expect to see flybracing from the bottom flange to the purlins.

 

[dauwerda]

Agreed with everyone's assessment.
dold, there is (was) flybracing from the perlins to the bottom flange of the girder. In some cases it appears the the flybracing had connection failures and in other cases it is still intact, however with the perlins buckled upward the girder(s) is still rotated in LTB. There were 4 frames in total that appear to have undergone LTB failures due to uplift.

 

[rowingengineer]

Don't know in your part of the world, but in my area, a lot of engineers had assumed lower internal pressure base on the roller doors having sufficient strength. In 2014 we tested a heap of doors and anything about 3m wide was poor and failed. Current day the codes have changed such that the engineer has to check the doors on every job and if the isn't sufficient info on the doors, they have to adopt internal pressure.

 

[hetgen]

According to the Eurocode, even if the roller doors are strong enough to take the external wind pressure, accidental load cases assuming open roller doors should be checked. The loads and material factors are taken as 1.0 when checking accidental load combinations.

 

[dauwerda]

The original part of the building was built in the 70's - I can almost guarantee it was designed as an enclosed building. I know that the door in the new addition (and framing around it) was rated to meet code level winds, I don't know if the smaller door in the original part of the building was though. I also believe that the wind speeds probably met and exceeded the design wind speed (90 mph ASD / 115 Ultimate). We are in a part of the country where tornados and micro bursts happen frequently (and are not typically designed for). The damage here was very localized, however all signs show that it was straight line winds from the west/northwest, so probably some type of microburst. The power lines feeding the building are 250 feet west of that door and 3 of those poles were snapped off at the base. The yard east of the building has lots of steel sections and plates stacked in it and some of the plate (6ftx12ft type sizes from 3/8" to 3/4") were moved around as well. The corn fields directly south, and west were essentially unphased. The cornfield to the east/southeast was destroyed and the center pivot was mangled.

There is no requirement here to design a building as partially enclosed if it has large doors that are rated for the wind speeds - it's more of an engineering judgment thing based on the likelihood of needing the door open during a design event.