Techno Press

Steel and Composite Structures   Volume 28, Number 6, September25 2018, pages 719-734
Non-invasive steel haunch upgradation strategy for seismically deficient reinforced concrete exterior beam-column sub-assemblages
A. Kanchanadevi and K. Ramanjaneyulu

Abstract     [Full Text]
    Prior to the introduction of modern seismic guidelines, it was a common practice to provide straight bar anchorage for beam bottom reinforcement of gravity load designed building. Exterior joints with straight bar anchorages for beam bottom reinforcements are susceptible to sudden anchorage failure under load reversals and hence require systematic seismic upgradation. Hence in the present study, an attempt is made to upgrade exterior beam-column sub-assemblage of a three storied gravity load designed (GLD) building with single steel haunch. Analytical formulations are presented for evaluating the haunch forces in single steel haunch retrofit. Influence of parameters that affect the efficacy and effectiveness of the single haunch retrofit are also discussed. The effectiveness of the single haunch retrofit for enhancing seismic performance of GLD beam-column specimen is evaluated through experimental investigation under reverse cyclic loading. The single steel haunch retrofit had succeeded in preventing the anchorage failure of beam bottom bars of GLD specimen, delaying the joint shear damage and partially directing the damage towards the beam. A remarkable improvement in the load carrying capacity of the upgraded GLD beam-column sub-assemblage is observed. Further, a tremendous improvement in the energy dissipation of about 2.63 times that of GLD specimen is observed in the case of upgraded GLD specimen. The study also underlines the efficacy of single steel haunch retrofit for seismic upgradation of deficient GLD structures.
Key Words
    gravity load designed; beam-column sub-assemblage; upgradation; steel haunch; energy dissipation; strength and stiffness degradation
(1) CSIR-Structural Engineering Research Centre, Chennai, 600113, Tamil Nadu, India;
(2) Academy of Scientific and Innovative Research (AcSIR), Chennai, 600113, Tamil Nadu, India.

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