Seismic performance of RC frames designed for three different ductility levels

The concept of “making structures ductile” has prevailed in modern earthquake-resistant building design. In this context, questions remain regarding the selection of adequate ductility levels and the corresponding seismic force reduction factor q for a specific class of structures, whereas the detailing requirements to ensure the desired ductility continue to be refined. In the current investigation, three simple frames were designed for different ductility levels according to EC8 [Eurocode 8: Design provisions for earthquake resistance of structures. CEN (European Commission for Standardisation)/TC250/SC8, 1994] and their actual performance when subjected to earthquake simulation tests are observed and compared. Results indicate that under the “ductility for seismic force reduction” trade-off scheme, the frame designed for high ductility (thus large q factor) tends to attract more extensive damage due to large yield excursion, resulting in certain performance reduction. Insufficient confinement could lead to degrade hysteretic behaviour in a rather sensitive manner. Satisfactory performance was observed in the frame designed for medium ductility where both the seismic force reduction factor and the overall ductility were in the order of 3–4. In general, the overall and local ductility demands and the q-factors were observed to correlate in a rather predictable manner.