A Nonconvex Optimization Approach for the Determination of the Capacity Curve and the Performance Point of MR Steel Frames Exhibiting Softening under Seismic Loading

Abstract

After the last catastrophic earthquake in Greece a vast need arized for the assessment of the structural response of existing buildings under seismic loading. To this end the elastic analysis methods which include code static and dynamic lateral force procedures and elastic procedures for the capacity design are insufficient. Although an elastic analysis indicates where first yielding will occur, it cannot predict failure mechanisms and account for the redistribution of forces during progressive yielding. This problem is bypassed in the phase of design of a new structure by the introduction of the behavioral factor of the structure (the well known q-factor) which is selected according to the specific structural typology of a new building. This factor is a divider of the lateral forces applied on the structures and accounts for the elastoplastic behaviour of the structure under seismic loading. At a later stage of the design, the value of the q-factor and the achievement of the predefined elastoplastic behaviour are ensured through the capacity checks of the seismic codes.