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cracking in waffle slab

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I am investigating an existing waffle slab that has
numerous cracks visible from below.  The structure
was built in the late 1950's, and the existing structural
drawings indicate the joist reinforcing, but do not use
the ?column strip, middle strip? distribution.  Our
analysis indicates that the total amount of top
reinforcing across a bay is about 10% low, but the
total positive reinforcing across a bay is 20% high.  It
seems that with moment redistribution, the overall
load carrying capacity is adequate.  A recent core
sample indicated a compressive strength of 3200 psi,
with the original design strength being 3000 psi.

The cracks appear to emanate from the corners of
the solid heads, and mostly run transversely across
the width of the structure.  There are also numerous
cracks at the interface between the joist and the slab
when viewed from below.  Unfortunately, most of the
top slab is covered with asbestos tile, so we cannot
see the crack patterns from above.

The slab is surrounded on all sides by concrete
foundation walls.  It is 3 bays @ 21' wide and 5 bays
@ 21' long.  There is a steel framed structure above
with moment frames that are supported on the
foundation walls.  The structure is located in Fremont,
CA.  An earlier report indicated that the cracks were
due to seismic activity.

Has anyone seen similar patterns of cracks in older
waffle slab structures, and is it possible the cracking
is due to seismic forces?  My concern is the low
concrete strength, however, I feel the cracking does
not indicate any structural distress.  Also, does
anyone have experience with repairing cracks like
these?  The earlier report indicated pressure injected
epoxy, which seems excessive.