RC columns strengthened by steel caging: Cyclic loading tests on beam-column joints with non-ductile details

Abstract

[EN] Beam-column joints suffer intense damage from seismic events and are the cause of many buildings collapsing. These zones present complex behaviour under cyclic loads, including tensile-compression cycles, which make reinforcement adherence worse and cause severe cracking in concrete. Although columns can be strengthened by various methods (e.g. concrete jacketing, fibre-reinforced polymers and steel jacketing-caging), beam column joints require complex systems being applied, but are not always effective. In Europe, fitting steel caging around columns is one of the most frequently used techniques, although its effectiveness against seismic events requires further study. The aim of this work is to analyse the behaviour of beam-column joints strengthened by steel caging subjected to cyclic loading, for which an ambitious experimental campaign was carried out on seven fullscale steel-caged specimens with a variety of strengthening solutions at joints. The results provide insight into the complex behaviour of joints with columns strengthened in this way, used as the basis for practical recommendations for engineers and architects who have to routinely retrofit structures against seismic events.