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RE: REPOST: Steel Lintel Bearing on Masonry Wall

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Dave,

I will respond below.

Regards,
Harold O. Sprague

> -----Original Message-----
> From:	Dave Nuttall [SMTP:dnuttall(--nospam--at)somervilleinc.com]
> Sent:	Friday, February 22, 2002 7:15 AM
> To:	seaint(--nospam--at)seaint.org
> Subject:	REPOST: Steel Lintel Bearing on Masonry Wall
>
> This is a repost of an earlier listing to which only 1 person initially
> responded.  This is a topic which I am hoping can be further discussed.
>
>
> I would still like to know what the various opinions are regarding the
> bearing of a steel lintel on a masonry wall.
>
> The typical lintel in question consists of a W section with a plate below
> spanning somewhere between 6' and 30'.
>
> Besides calculating the required bearing length, is there a preferred
> method
> of anchorage?
		First of all, I try to avoid steel wide flange lintels just
because the load paths are very difficult when it comes to the out of plane
loads.  I prefer to provide a steel bearing plate with a Teflon sheet,
slotted holes in the WF.  This allows the lintel to move relative to the
bearing.

> Should the lintel truly be anchored to the masonry by welding  it to a
> bearing plate, or should the lintel have provisions to move slightly so as
> not to produce fixity?
		See above.  I have seen to many cracked masonry walls at the
bearing point.

> What complications occur by fixity if the lintel is supporting a cavity
> wall, where the brick wants to expand, and the cmu backup wants to
> contract,
> but the lintel is only bearing on the cmu?
		It will crack.  You need to have more joints in the brick
and use ladder joint reinforcing as opposed to truss type in order for the
brick to move differentially to the CMU.

> Does one method produce a different expansion joint & control joint layout
> over another method?
		At the bearing point, the brick joint and the CMU joint
should be at the end of the steel bearing and then go up to the top of the
wall.  The brick will have closer spaced joints than the CMU.  All of the
joints need to be shown on the elevations.  The trick is how to handle the
out of plane forces.  In the CMU above the lintel bearing, I like to use a
keyed joint to preclude out of plane movement.  To transfer the out of plane
forces transferred through the lintel and into the anchor bolts requires a
special jamb detail for the CMU.  Below the bearing are CMU blocks with a
lot rebar to handle the inadvertent thermal stresses parallel to the steel
lintel, the vertical forces, and the out of plane wind / seismic forces that
will have a torsion component because the bearing is stepped.

> I would also like to know the various details and configurations of the
> different cavity wall lintels used by my peers.
		If possible, I like to use a reinforced CMU for the lintel,
and provide an angle to carry the brick.  The CMU is an A block.  The lintel
itself is the classic U bond beam.  The jambs are reinforced to take the
gravity and out of plane loads.  The US Army Corps of Engineers has some
great details in their publication "Masonry Details", No. 000-90-04
September 1997.  Some of their details are contained in
http://cadlib.wes.army.mil/cgi-shl/dbml.exe?action=Query&template=/detlib/cd
l_str.dbm

> Your opinions are appreciated,
>
> Dave Nuttall, P.E.
> Green Bay, WI
>

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