Max deflection of beam over bifold doors

[acg83]

Hi,

I'm going for a 5m wide opening in my new 2 storey extension for bifold doors and was wondering what an allowable deflection for the beam to avoid any potential jamming of the doors.

At the moment, my structural engineer has spec'd a beam which will have a max deflection of 14mm under live+static loads (with margins applied).

A google search took me to a website that suggests a limit of 7mm and speaking to a bifold door supplier/manufacturer (albeit to a salesman), he had a figure of 5mm static deflection permitted [not 100% sure the chap fully understood the difference with live and static] although he also said the surveyor would normally allow for 10mm on width and height - presumably to allow for packers to be installed.

My structural engineer says in his experience of 30+ years and plenty of bifold door installs, the 14mm is OK and if it comes to it, really it's only going to be the live loads that would cause the jamming to happen as the door will be installed only once the shell, first floor joist and roof are built so deflection from the static loads will be present when being measured and installed. I assume the packers will be able to account for the nominal static deflection of the beam.

Does anyone have any thoughts or experience in this field? I'm wondering whether to up the spec on the beam to limit it to only 5mm total deflection but I'm mindful that will result in a bigger/heavier beam.

Also, the beam has a 10mm welded plate supporting the outer brickwork. Is it normal for the door frame to be fastened to/through this plate and into the masonry?

Thanks

Adam

 

[chappers]

Just fasten into the steel using tek-screws.
I've always allowed around 25-30 mm on height measured at the beams bearing. Some bi-folds require slightly bowing the frame up at the centre to stop the doors trying to close when opened and for 5m about 10mm bow would be about right

 

[Paulg31]

Hopefully not too late reply to this. Beams would generally be sized for span/360 imposed load deflection and span/250 total (dead+imposed) load deflection.

As you say once site measures only imposed load deflection will occur. I can't the the imposed load defection causing a problem.

Also the 10mm plate which is guess it welded to the bottom flange of a UB section will increase its stiffness, something which will reduce deflections. I bet that hasn't been taken into account in the deflection calc.

 

[JohnWils]

PaulG31, I've posted a post re: bifolds and deflections, and you seem knowledgeable about this kind of thing, would you mind taking a look and seeing if you could help me out at all? It's in the building regs forum.

Thanks