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Shortening existing concrete joist

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	I have a condition where I would like to shortening the span of an
existing concrete joist.

Information:	Approx 19 ft (single span) 
		Bearing on loadbearing masonry walls
		Existing drawings only identify joists as an 8" channel
slab, nothing else
		The building was built in the early sixties

		Shortening span approx 3 ft
		Floor use is not increased
		For my reference, I have a 1963 CRSI Design Handbook Vol II.
		No old geezers in the office

	I haven't run any numbers yet, but the joist should be good for
moment and shear (no tapered ends).  The CRSI manual lists bottom and truss
bars, which are both at the bottom of the beam at a distance equal to the
span/7 from each end (in the manual).  As long as the maximum moment isn't
within this distance, the concrete joist should be okay to cut.  Am I right?
Is there anything else that I should check?

	Roland Bokma, E.I.T.
	Grand Rapids, MI