To: "Seaint list (E-mail)" <seaint(--nospam--at)seaint.org>
Subject: closure strip connection to wall fixed or hinged? [post tensioned flat plate ]
From: "Haan, Scott M." <HaanSM(--nospam--at)ci.anchorage.ak.us>
Date: Sat, 4 Aug 2001 08:11:14 -0800
I had an experienced engineer indicate to me that there were two typical
ways to design closure strip-to-wall connections [propped cantilever or
continuous]. For a permit I am reviewing there is a continuous wall with a
closure strip along it. The flat plate was designed [distributed tendon
direction] with a hinged connection to the wall but top and bottom mild
steel are anchored into the wall.
There is enough top steel detailed for a shear friction connection and there
are bottom bars doweled into the wall but if a closure strip "propped
cantilever moment" is calculated by multiplying the reaction at the tendon
anchorage by the closure strip width then the top steel is insufficient for
(-) moment strength.
There is self limiting deformation at the connection because there are
supports at both ends of the slab span, and even if the top steel yields
under a "fixed end moment" there is still adequate shear friction for the
situation I am looking at. Also there is dowel action from bottom steel
that is anchored into the wall. Brackets and corbels have a minimum steel
requirement to prevent sudden failure but this condition is not cantilevered
and there is self limiting deformation at the wall.
1) For a closure strip connection to a wall, is it acceptable to assume the
slab has a "hinged" connection to the wall at the cold joint when top and
bottom steel is shown anchored in the wall [steel has to be anchored for
2) Is it acceptable at the cold joint for the slab fixed end negative to
exceed the slab (-) moment strength after the shoring is removed and have
just enough top steel anchored to the wall for a shear friction connection
moment [span is designed hinge supported at wall]?
3) How are these connections typically designed?
4) Is reinforcement corrosion a problem at cold joint intersections of
closure strips and walls in flat plate parking garages [it seems you would
not want your shear friction reinforcement corroding if a crack forms and
water and deicing chemicals get into it]?
5) Are there guidelines on preventing cracking at the intersections of
walls and closure strips?
Scott M Haan P.E.
Plan Review Engineer
Building Safety Division
Development Services Department
Municipality of Anchorage
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