Seismic Strengthening of Deficient Reinforced Concrete Frames Using Reinforced Concrete Haunch

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Title: Seismic Strengthening of Deficient Reinforced Concrete Frames Using Reinforced Concrete Haunch

Author(s): Junaid Akbar, Naveed Ahmad, and Bashir Alam

Publication: Structural Journal

Volume: 116

Issue: 1

Appears on pages(s): 225-235

Keywords: joint damage; reinforced concrete haunch; retrofitting; seismic strengthening; shake table

Date: 1/1/2019

Abstract:
Shake-table tests conducted on reinforced concrete frames not conforming to code requirements and ACI 318 detailings have revealed severe susceptibility to beam-column joint damage under seismic excitation. This research considered two 1:3-scale, two-story reinforced concrete frames having construction defects and strengthened with reinforced concrete (RC) haunches mounted at the beam-column connections, considering different application schemes. The structures were subjected to a linearly scaled accelerogram of 1994 Northridge earthquake. The damage mechanism and lateral force-deformation capacity curve of tested frames were obtained. The proposed strengthening technique reduced the joint damageability and enhanced the structural stiffness, strength, and ductility. The response modification factor calculated for the tested frame—5.5 for Model-1 and 7.5 for Model-2—resulted in an increase of 88% for Model-1 and 167% for Model-2 in comparison to as-built tested frames. This low-cost strengthening technique can improve the seismic performance of RC frames having deficient beam-column joints to resist frequent and rare earthquake events.