Design of steel and composite structures with limited ductility requirements for optimized performances in moderate earthquake areas (Meakado) : final report

The research project Meakado aims at developing adjusted design approaches for steel and steel-concrete composite structures in regions characterised by a low to moderate seismic activity. The methodology targets an optimal balance between safety and economical concerns. Two parallel ways are followed to achieve this goal. The first one is based on a controlled exploitation of dissipative phenomena that are commonly not explicitly considered in the design (friction in bolted shear connections, ovalization of bolt holes...) while the second one investigates the possibilities of a better tuning of the design requirements recommended by existing seismic codes to the actual demand imposed by a low to moderate seismic action. A design methodology intermediate between the DCL and DCM approaches of Eurocode 8 is proposed, in which a reduced but controlled amount of ductility is accounted for, providing thus the necessary safety with respect to uncertainties on the seismic action, but where for instance the local ductility or structural homogeneity requirements are less stringent than in a conventional EC8-DCM design. The focus is set on intermediate values of behaviour factors (typically q equal 2 to 3) that are often sufficient to reach a suitable design in moderate earthquake zones. Results are achieved with regard to moment-resisting and concentrically braced frames, based on a combination of extensive experimental and numerical studies. Concrete suggestions are finally made for the future revisions of the design codes.