Retrofit of Pre-Northridge Moment-Resisting Connections.
Retrofit of Pre-Northridge Moment-Resisting Connections.
(479 K)
Civjan, S. A.; Englehardt, M. D.; Gross, J. L.
Journal of Structural Engineering, Vol. 126, No. 4,
445-452, April 2000.
Keywords:
steels; seismic rehabilitation; steel moment connection;
welded bottom haunch; steel moment connection retrofit
Abstract:
An experimental program was undertaken to evaluate
methods to retrofit existing steel moment connections
for improved seismic performance. Six full-scale
subassemblages were tested under cyclic loading. Typical
pre-Northridge connections were retrofit by the addition
of either a bottom flange dogbone 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 bottom flange dogbone was combined with
replacement of beam flange groove welds with higher
toughness welds. The welded bottom haunch retrofit
showed excellent performance on specimens with a
composite slab, even though the existing low toughness
beam flange groove welds were left in place. The
presence 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 the complete
experimental program.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899