Improving the seismic robustness of reinforced concrete frames by using locally hybrid steel-concrete columns

The proposed concept consists in placing a steel profile with limited size inside the reinforced concrete column of the first level of the building. This profile is not considered for the design and is essentially assumed to act as a safety belt activated only in case of deficiencies of the concrete under earthquake action, providing thus the requested robustness and limiting the risk of soft-storey mechanisms even in the most unfavorable conditions. Theoretical, experimental and numerical investigations summarized in the present contribution are aiming at demonstrating the efficiency of the concept.