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> The load factor for DL alone is 1.4; the load factor
> for DL when used
> in combination with LL is 1.2.  What load factor was used to
> draw the moment
> diagram for the DL?

You are freely interpolating the concept of "moment diagram" with that of
"moment envelope diagram." They are not the same.

The envelope combines all the probable effects of the various load

In fact, it is arguable that it gives a much more realistic picture (really
a "fuzzier" picture) of what the response to the REAL loads will be.

It IS probabilistic, because NATURE is probabilistic.

> Let us also consider in the same situation that the service
> load DL and LL
> moments at that same point are both positive.  But, when we
> apply the load
> factor to the live load, the live load moment at that point
> becomes negative
> (entirely possible particularly for a continuous beam with
> the live load in
> an adjacent span), what do we do?

Again, you seem to be upset that the LRFD design code procedures are
muddying the waters for you.

Too bad.

The fact is that this is a much, much more realistic snapshot of the various
possibilities involved in structure behavior.

That it isn't simple-minded, as ASD code-based procedures would have you
believe, is too bad. Dealing with reality often is.