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RE: Shear Flow

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Charles:

I have had success strengthening some 25' span carpenter style roof trusses
using steel plates and timber rivets. We lifted the truss prior to adding
the timber rivets. There has been a string line on a few trusses, and they
have not moved in over a year. I wonder if timber rivets would work for
wood-steel plate composite beams?

Jeff

|~|-----Original Message-----
|~|From: Charles Greenlaw [mailto:cgreenlaw(--nospam--at)speedlink.com]
|~|Sent: Monday, February 14, 2000 12:30 PM
|~|To: seaint(--nospam--at)seaint.org
|~|Subject: Re: Shear Flow
|~|
|~|
|~|At 01:42 PM 02/14/2000 -0600, you wrote:
|~|>I have a wood glulam beam that I would like to reinforce by
|~|adding a steel
|~|>channel to both sides. I am trying to find the shear flow at
|~|the channel to
|~|>wd beam contact area so that I may figure our how many bolts I need to
|~|>faster the composite beam together.
|~|-----------------------------------------
|~|
|~|For practical reasons, you can't use bolts successfully to
|~|transfer shear to
|~|wood to obtain composite action for flexure. There is too much clearance
|~|space in both the steel and wood around the bolts to obtain
|~|direct bearing
|~|before deflections have become excessive. You cannot use the
|~|bolts as clamps
|~|to obtain shear transfer by friction between the clamped
|~|surfaces, because
|~|the wood swells and shrinks with seasonal moisture changes, and
|~|compresses
|~|cross-grain, and falls loose between the steel members.
|~|
|~|Charles O. Greenlaw  SE   Sacramento CA