Seismic Behavior of Nonductile Reinforced Concrete Beam-Column Frame Subassemblies: Fid-Bau Portal

Seismic Behavior of Nonductile Reinforced Concrete Beam-Column Frame Subassemblies

Motter, Christopher J. / Opabola, Eyitayo / Elwood, Kenneth J. / Henry, Richard S.

The 2010–2011 Canterbury Earthquakes in New Zealand highlighted the vulnerability of gravity load resisting reinforced concrete frames in older buildings that do not comply with modern building design standards. Three full-scale reinforced concrete beam-column-joint frame subassemblies, representative of 1980s construction in New Zealand, were constructed and tested to failure to assess the deformation capacity of the subassemblies. The subassemblies differed in the spacing of joint reinforcement and surface roughening at the ends of the precast beams framing into the joint. The circular columns were nominally identical in all tests and were compression-controlled with a transverse reinforcement ratio of 0.0006 and a ratio of spiral reinforcement spacing to an effective depth ( $s / d$ ) of 0.74. The columns were susceptible to flexure-shear failure. Column failure occurred in all tests, with the failure plane propagating along a diagonal crack for two of the three tests. The lateral drifts at the column axial failure were 2.39% and 3.03% for the two columns that failed along a diagonal crack and 4.85% for the column that did not fail along a diagonal crack. It was demonstrated that the difference in performance can be attributed to variability in concrete strength, which is shown to have a significant influence on the likelihood of flexure-shear failure of the columns.