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Openings in Concrete Block

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Question - how to handle a opening in a concrete block?

Concrete block is 42" x 48" x 15" high, with a layer of wood on base. 
Blocks are used to support ships in dry dock - therefore loading is ~ 
uniform over top surface. To allow forklift handling of block, I want to 
embed (2) each 10x4 structural tubes at mid-depth of block. This leaves 
5.5" of concrete above and below the tubes.

I seldom work in concrete design, so have been seriously flailing away at 
trying determine if this is OK. First instinct was to check tube for 
crushing with full load - no good, wall thickness would be excessive. Then 
I analyzed concrete portion as a frame neglecting any effect of tube (may 
rust away anyway) - i.e., 5.5" deep concrete "beam" over tube regions. I 
seemed to be able to get enough re-bar to handle flexure, but couldn't 
handle shear in that region.

If the block were deeper, it seems the concrete area removed by the tubes 
would be irrelevant. I've been pouring through ACI 318 for something on 
holes in webs or through columns, but come up empty handed. Am I making 
this overly complicated?  Help!