An experimental program was undertaken to evaluate methods to retrofit exis
ting steel moment connections for improved seismic performance. Six full-sc
ale subassemblages were tested under cyclic loading. Typical pre-Northridge
connections were retrofit by the addition of either a bottom flange dogbon
e or a welded bottom flange haunch. Retrofitted specimens were tested both
with and without a composite floor slab. The tests showed poor performance
of the bottom flange dogbone retrofit when the existing low toughness welds
were left in place. Somewhat improved performance was observed when the bo
ttom flange dogbone was combined with replacement of beam flange groove wel
ds with higher toughness welds. The welded bottom haunch retrofit showed ex
cellent performance on specimens with a composite slab, even though the exi
sting low toughness beam flange groove welds were left in place. The presen
ce of the composite slab appeared to help prevent fracture of the existing
top flange weld in the haunch retrofit. This paper provides a summary of th
e complete experimental program.