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Concrete Boat Ramps

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Pat Bachman <BachmanPM(--nospam--at)c-b.com> wrote:

>I must provide guidance on a concrete boat ramp to be subject to fresh
>water level fluctuation. I can think of no special requirements,
>except a toewall to prevent undercutting, and perhaps a low slump mix
>to preclude shrinkage cracking for protecion of the reinforcing
>against corrosion.

>I understand the COE has a document on this, however, I cannot locate
>it on their webserver. Does anyone have a reference on concrete boat
>ramps or any pertinent information that makes them different from a
>typical slab-on-grade from a structural design standpoint. Thanks.

Pat,

The COE has an Engineering Manual (EM1110-2-2104) called Strength
Design for Reinforced Concrete Hydraulic Structures.  Although it doesn't
refer to boat ramps, it does state it's applicable for reinforced concrete
structures subject to submergence, wave action, spray, and other
severe climatic conditions.  It basically refers to ACI 318 with two
significant modifications, both of which are designed to reduce the
chance of corrosion of the reinforcement.  The first modification is that
the service loads are multiplied by a hydraulic factor of 1.3 in addition to
the DL and LL load factors in ACI 318.  This improves crack control by
decreasing the stress in the steel at the service load levels since more
reinforcing steel would be required.  The second modification is that the
concrete cover should be four inches for those structures greater than
24 inches thick, and three inches for those structures 12 to 24 inches
thick.  Less than 12-inch thick structures should conform to ACI 318. 

I hope this helps.

Michael S. Davis, P.E.

Btw, a question for everyone: Did any of you attend the Structural
Engineers World Congress in San Francisco this week?  It was very well
done and quite interesting.