Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Building & Construction

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 02-18-2014, 05:03 PM   #1
Newbie
 
Join Date: Feb 2014
Posts: 2
Share |
Default

PFC Beam Question


Hi all,

I am part way through a house remodel and the engineer I was using has disappeared ...... oh the joy! Luckily he gave me he structural drawings I paid for but I now have questions with no one to ask - hence this forum

Essentially I am looking to knock out a structural wall and but in a PFC beam. Span is 6m and the engineer has specified a single PFC beam 230mm by 75mm at 25kg/m bolted to the existing wooden floor bearer. Unfortunately this reduces the head height in the room below so I was thinking of using two 150mm by 75mm at 17.7kg/m PFCs with the existing wooden bearer sandwiched in between. That way I get an extra 80mm head height.

Does anyone know if this will have any problems? I am assuming there is a linear relationship in PFC strength but am unsure is this assumption is correct.

That is I assume 1 * 230 PFC with a webbing of 12mm and a flange of 6.5mm will be equivalent of 2 * 150 PFC which each have a webbing of 9.5mm and a flange of 6mm.

Any views?

beechworth is offline   Reply With Quote
Old 02-19-2014, 03:06 AM   #2
Member
 
Join Date: Apr 2012
Location: UK
Posts: 713
Default

PFC Beam Question


Beechworth - it doesn't work like that.
In your case, the critical factor will probably be deflection of the beam, and this has to be kept within certain limits.
All other things being equal, the deflection of a beam is directly proportional to a property of the cross-sction of the beam known as the 'moment of inertia'.
Put simply, the moment of inertia of a 230x75 is 2748 units; the moment of inertia of a 150x75 is 861 units (so the moment of inertia of two 150s will be around 1700 units).
This means that the two smaller beams together will deflect about 1.6 times as much as the deeper beam.
You need to check this with another SE.

tony.g is offline   Reply With Quote
Old 02-20-2014, 04:19 AM   #3
Newbie
 
Join Date: Feb 2014
Posts: 2
Default

PFC Beam Question


Thanks for the quick reply! Great to have the required information. I have done as you said and need to go with two 180PFCs to get a moment of inertia just above what I can achieve with a 230PFC. Cost will be 150% over the 230PFC but the additional 50mm head room will be worth the costs. Thanks again.
beechworth is offline   Reply With Quote
Old 02-20-2014, 08:43 AM   #4
Member
 
Join Date: Apr 2012
Location: UK
Posts: 713
Default

PFC Beam Question


Intended to say that deflection was 'inversely proportional' to 'I', but you appear to have sussed that!
tony.g is offline   Reply With Quote
Reply

Tags
pfc channel


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
OSB Stronger than Plywood? Weathermaker01 Flooring 15 12-22-2012 09:06 AM
Beam Question bcgfdc3 Carpentry 13 07-08-2012 07:18 AM
Beam to post question for a deck... dbldee20 Building & Construction 0 06-04-2012 09:24 AM
Deck Beam Question Giles Building & Construction 13 04-05-2011 10:01 PM
Beam Question cibula11 Building & Construction 8 01-22-2007 12:12 PM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.