Lutfi,

Could you clarify your question?   
Is it a beam-to-column moment connection?
Where is the 1 to 2 inch gap?  
Why is the gap so big?
If the gap is going to filled with the weld, how is the stresses produced by the cooling weld are going to be mitigated?

Regards

the connection is along the beam span (not beam to column). The gap need to be that large so that the frame can be adjusted to meet strict tolerances. The gap between flanges and webs will remain after the splice plates are welded. It is estimated that the gap will be in the middle of the span (very short span). My intent is to weld the new splice plates to the flanges and webs with fillet welds.

Lutfi,

The AISC's Manual of Steel Construction, ASD, on page 4-100 shows a beam-to-column welded moment connection.   I assume you could use that detail, slightly modified, to make the splice connection.

Further on in the AISC Manual of Steel Construction, ASD, on page 4-129 are examples of welded moment splices. I would think that the use of a backing bar, as shown, would solve your gap problem. The backing bars would have to carry the tension and compression forces due to the moment. Also you would need a shear splice across the web.