Design of steel flitch plates 1

[FrankHartzell]

Can anyone give me a good reference or two regarding design of steel flitch plates for timber beams and columns?

 

[structman]

Check out Wood Technology in the Design of Structures by Robert J Hoyle, Jr.-- section on Composite Beams--not alot of info, but will get you started. [sig][/sig]

 

[kdhenry]

Also check out:
"Wood Engineering and Construction Handbook" by Faherty & Williamson
and
Timber Design and Construction Handbook bt Timber Engeneering Company.

Both are available on "out of print" search engines.
Both are published by McGraw-Hill and are very good references. [sig][/sig]

 

a design guide for steel flitch plate beams is available from our website Destefanoassociates.com. Click on technical stuff

 

[ZCochrane]

What are the design considerations for a flitch plate that isn't sandwiched between the 2x members but instead is bolted on the face of the 2x beam? Obviously we lose the frictional holding power of having the plate between the two wood members but is this significant? Is there a need to alter bolting patterns?

The plate in question is 16'x 7" on (2)2x8x18' so it stops a foot short of either end of the wood beam.

TIA

 

[andrewc]

hi gents

i'm a uk engineer.

i'm often involved in building alteration, most of which in this country are traditional load bearing masonry.

builders seem to be split fairly evenly whether they want flitch beams or steel beams in alterations.... both camps claim they are easier to install....

anyway... flitch beams... without exception i have never stopped a plate short of its bearing because i design the steel plate to do the entire job and consider the timber either side and the adjacent floor area to be adequately restraining the flitch plate; this is much more straightforward than worrying about the transformed section, which often gives negligible benefit.

with regard the flitch beams where the plate stops short of the end of the beam, the principal considerations are the combined effects of bolt bearing, shear and moment transfer of the bolts into the timbers either side of the plate along the length but mainly at the ends of the plate. the british institution of structural engineers [ISE - www.istructe.org] posted a paper by a chap a short while ago that specifically dealt this this issue, and while i've not used it myself i have read it and it appears quite reasonable; although as i say i prefer to take the plate to the bearings.

if you'd like an extract of the ISE paper, please let me know and i'll post a link to it on my website.

hope that helps

andrew

 

[jwkilgore]

Since the plates are not restrained as in a typical flitch beam, their capacity will be reduced. You'll have to check lateral buckling of the compression side. I.E., if your top bolts are spaced 24" o.c., a conservative design would be to reduce the capacity of the plate assuming an unbraced length of 24". The bolts will restrain against buckling some-what, but I don't know how to calculate this restraint off the top of my head.

Another solution might be to bolt steel channels to the wood beam instead of plates. The top edge will be braced by the top flange, and could reduce the number of bolts you need.