High strength steel in seismic resistant building frames

Seismic resistant building frames designed as dissipative structures, must allow for plastic deformations to develop in specific members, whose behaviour is expected to be predicted and controlled by proper calculation and detailing. Members designed to remain elastic during earthquake, such as columns, are characterized by high strength demands. Dual-steel structural systems, optimized according to a Performance Based Design (PBD) philosophy, in which High Strength Steel (HSS) is used in predominantly "elastic" members, while Mild Carbon Steel (MCS) is used in dissipative members, can be very reliable and cost efficient. Because present seismic design codes do not cover this specific configuration, an extensive European research project [1], HSS-SERF - High Strength Steel in Seismic Resistant Building Frames, was carried out with the aim to investigate and evaluate the seismic performance of dual-steel building frames. On this purpose, and based on a large numerical and experimental program, the following objectives have been focused into the project:
1. to find reliable structural typologies and joint/connection detailing for dual-steel building frames, (e. g. of HSS and MCS members), and to validate them by tests and advanced numerical simulations,
2. to develop design criteria and performance based design methodology for dual-steel structures using high strength steel,
3. to recommend relevant design parameters (i. e. behaviour factor q, overstrength factor Ω) to be implemented in further versions of the seismic design code, EN 1998-1 [1], in order to apply capacity design approach for dual-steel framing typologies,
4. to evaluate technical and economic benefit of dual-steel approach involving HSS.