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RE: Bridge Expansion Joint Elimination

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I agree with Mr. Turk's explanation of the consequences of skew.  I also
agree with his point that integral abutments are usually dependent on
flexible abutment supports (e.g. a single row of piles or a concrete hinge
at the footing).

However, I must disagree with Mr. Turk's conclusion that the expansion joint
is merely relocated to the joint between the approach slab and the abutment.
Though this may be the case in some designs, none of the details I have seen
(Texas, Ohio, Tennessee and California) relocate the expansion joint to
between the abutment and approach slab; instead, it is moved to the far end
of the approach slab.  This eliminates deck drainage from reaching the
abutment through a failed joint seal, and is one of the major reasons for
using an integral abutment in the first place.

Tony Powers
HDR Engineering, Inc.
916-351-3837
tpowers(--nospam--at)hdrinc.com


> -----Original Message-----
> From:	Roger Turk [SMTP:73527.1356(--nospam--at)compuserve.com]
> Sent:	Friday, March 19, 1999 1:09 PM
> To:	seaint(--nospam--at)seaint.org
> Subject:	RE: Bridge Expansion Joint Elimination
> 
> Tony Powers wrote:
> 
> . > I have also seen abutment joints removed from bridges by casting a 
> . > concrete end diaphragm to encase the girder ends. 
> 
> 
> The philosophy behind integral abutment bridges is that the abutment
> supports 
> are flexible and will permit the abutment to move as expansion and 
> contraction of the bridge occurs.  When this assumption (flexible
> abutments) 
> is valid, it will only "work" for a bridge without a skew.  If the
> abutment 
> is skewed, is only flexible in a direction normal to the axis of the 
> abutment, and is very rigid in the direction of the abutment axis.  As a 
> result, when there is expansion and contraction of the bridge deck, large 
> horizontal shears (even with small skews) have to be developed in the
> bridge 
> deck in order to force the abutment to move in the direction that the deck
> 
> expands and contracts.  These large forces even occur in simply supported 
> bridges with skewed piers.
> 
> Integral abutments do not eliminate the expansion joint, but just relocate
> it 
> to the joint between the approach slab and the abutment.
> 
> A. Roger Turk, P.E.(Structural)
> Tucson, Arizona
> 
>