R&D Report: Optimising the seismic performance of steel and steel-concrete structures by standardising material quality control
The research proposal aimed to assess the influence of material properties’ scattering on final structural performance of steel and steel-concrete composite structures designed in earthquake-prone areas. In particular, the research focused attention on:
- Assessing structural performance considering the variability of material properties (i.e. 'q' factor estimation).
- Defining a model able to represent actual scattering of European production of steel products (i.e. steel profiles, steel reinforcing bars, and steel plates).
- Estimating the structural safety of steel and steel-concrete composite structure explicitly considering variability of material properties and of seismic input (i.e. structural safety considering actual EN1998 design procedure and EN10025 production standard).
- Assessing the influence of imposing an upper limit to the yielding stress (i.e. fictitious additional quality check for EN10025 produced steels) on structural safety.
- Evaluating the sensitiveness of capacity design approach to the factor introduced for taking into account steel over-strength.
Previous research tasks were developed by partners in order to define general indications about a possible road map for defining a harmonisation between production standards and design standards and answering to the following unclear points:
- The benefits produced by upper yielding stress limitation on final structural performance of steel and steel-concrete structures in seismic areas.
- The appropriate values of over-strength factor to be considered as appropriate for the application of capacity design approach.
Research plan and work carried out
The research was organised into 9 work-packages over three phases:
- Phase 1 - devoted to the definition of structural case studies testing the influence of material properties scattering and to the quantification of material properties’ scattering
- Phase 2 - the core part of the research, in which the probabilistic and numerical issues were developed
- Phase 3 - the results coming from numerical simulations executed on structural case studies were compared with actual standards situations and with statistical investigation of material properties’ scattering
© European Union, 2013 - Reproduction is authorised provided the source is acknowledge.
Overview
Modern codes on seismic design, such as Eurocode 8 or FEMA 350, allow for the design of ductile structures able to absorb high plastic deformations for energy dissipation. Eurocode 8 introduces the 'q' coefficient, or behaviour factor, as reduction factor of the seismic action, summarising the parameters that govern the structural response, the inelastic resources, and the sensibility to the second-order effects. The possibility to exploit plastic resources is translated in lower values of design seismic actions defined by the peak acceleration experienced by the structure.