I am looking for the easiest, lowest cost, safe and code compliant way to shore up a sagging two car garage door roof (residential, Florida).  Recently bought this 30 year old masonry home which has a shingle over-roof (two layers).  The problem is at least several years old.  Lintel, which appears to be concrete beam, is sagging about 2.5" across the 16' span - sag is smooth curve, with some cracking at end fastenings.  Assumming it is due to weak concrete and some overload.  Trying to avoid replacement.

Comments by anyone with experience in this type problem appreciated.  I intend to talk with city engineers first, but I am thinking of underlaying with a steel beam (best type?) with end attachments and center jack-post support.  Need to find double shingle truss roof load data, concrete lintel weight data, and candidate light duty steel beams/data.  I am electrical eng, maybe can do rough calcs, but realize I will probably need a licensed engineer to review.