accidental openings

[rowingengineer]

The Australian wind loading standard is proposing to have a clause that states for cyclonic (Hurricanes and Typhoons)conditions that accidental opening must be included in the assessment of internal pressure.

"In Regions C and D (this is the regions that are considered cyclonic), for parts of buildings that may be subject to debris impact (normally taken as the lower 25 meters above ground), a design case shall include internal pressure coefficients due to accidental openings, taken as the external wall pressure coefficients, unless lower pressures can be justified (e.g. due to permanent vents)."

I find this to be interesting, do they mean accidental as in someone left the back door open and now the building may disappear? or do they mean unintended openings due to impacts from a tree falling or similar.

The past clause referenced opening caused by impacts from windborne debris.

Do you think that this un-probable event should be taken into account of people accidentally leaving a door open that is capable of withstanding the design laods?

http://www.nceng.com.au/

"Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning."

 

[BAretired]

I don't know what they meant, but openings can be a major problem when designing for strong winds. Consider, for example a building designed for washing cars. It has overhead doors front and back.

With two adjacent bays, one could have the door open on the windward side while the other had the door open on the leeward side. The wall separating the bays would have strong positive pressure on one side and strong negative pressure on the other side. Perhaps this is what the Australian code considers as "accidental" openings.

BA

 

[Ron]

RE...similar provisions in our code (ASCE 7). I would consider an "accidental opening" to be one that was caused by impact or insufficiently designed protection of openings, such as having windows that don't meet the wind load requirement, no impact glass, no ancillary protection for the windows (shutters, etc.)

 

[shobroco]

It would seem to me that when you start designing for "accidental" effects, you head down a never-ending path. Do you design columns in an industrial building for "accidental" removal by the towmotor operator? Do you design roof structures for "accidental" aircraft landings?

 

[asixth]

I reckon it means openings cause by debris or openings that were just blown out. I was providing condition assessments after cyclone yasi and it is very easy for and opening to be created when a large branch or tree comes rocketing into the side of the building.

 

[PersonalProfile]

Potentially accidental intends anything other than the design assumption (broken walls, open / broken windows doors etc) - although the design assumptions could have been potentially more robust, hence the update to the standard.

http://aibs.businesscatalyst.com/announcements/upgrade-to-cyclone-resistance-requirements

http://www.qldreconstruction.org.au/u/lib/cms/Part 2 Wind Resistant Housing.pdf

Regards,
Lyle

 

[hokie66]

I believe that most of us already consider windows to be openings, and also things like roller shutters which are not very strong, in spite of what a manufacturer might say.