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Concrete Crane Beam for 40ton Container Crane

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I am analyzing an existing (1974 era) concrete crane beam that
is cracked badly to determine what is causing the cracks.  The
beam is part of a marginal wharf and supports a container crane
used to load 40-ton containers onto ships (see sketch below).

        | ~~~~~~~~~~~~~ |
        |!o  o  o  o  o!|<--5#10 bars
        |!             !|
38"High |!          -->!|<--2" clear to
        |!             !|   #4 stirrups
        |!             !|   on sides and bott.
        |!             !|
        |!o  o  o  o  o!|<--5#10 bars
        | ~~+-------+~~ |   (these basically
        +---|-------|---+    lay on top of pile)
            |       |
            |       |<--20" Octangonal Pile
            |       |   embedded 2" into cap

The cracks run horizontally along the sides of the beam at the
level of the bottom layer of reinforcing.  The length of the
cracks runs almost the entire length of the waterside beam.  The
concrete has even spalled off the beam over many of the piles. 
The landside beam (same except 6" wider) doesn't have any cracks
but doesn't see as much load either.  

The bottom bars are lapped over the piles.  The original
drawings call for a lap length of 24 bar dia. (only 31").  My
copy of CRSI lap length tables for ACI318-71 call for a class B
lap splice to be 72" long (fc=3000psi, fy=60ksi).  This
structure used 40ksi bars so that length can be reduced to 48",
but this is still 50% more than was provided.  For ACI318-95, it
gets worse.  The required lap length goes to 61".

In addition to the lap length apparently being far too short,
I'm not sure how much bond can be attained over the piles since
the bottom bars were essentially placed directly on top of the
piles (pile embeded 2", cover over reinf. 2", see below).  This
leaves no concrete at bottom surface of bars for the bars to
bond to.

I know this is pretty long post, but I wanted to give you all a
good idea of what I'm looking at.  Right now I think the culprit
for the cracks is a bond failure of the bottom bars over the
piles.  I think this opened up the concrete and allowed the bars
to corrode which caused the cracks to propogate even further.  

What do you guys think?  Could I be missing something?  I mean,
the crane hasn't fallen in the river yet, but I think the beam
will need to be replaced.  Any input would be appreciated.

Tripp Howard

Tripp Howard

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