In
this paper, the Eurocode 8 design approaches for concentrically braced steel
frames are assessed with respect to observations and findings from shake table
tests on full-scale concentrically braced single storey frames. The stiffness,
resistance and ductility of the frames tested are assessed, and recommendations
for estimating key response parameters are outlined. In particular, measured
frame stiffnesses and natural frequencies are compared with estimates based on
tension and compression brace stiffness. Several sources of member and frame
overstrength, which play an important role in seismic performance and design,
are identified. The tension-based design approach largely adopted in design is
examined together with the member slenderness limits imposed on the bracing
members. It is shown that the overstrength factor specified in Eurocode 8 for
the design of connected non-dissipating elements of the structure may underestimate
the actual behaviour. It is also observed that the bracing members with
slenderness exceeding the codified limits demonstrated generally satisfactory
performance. Despite lower energy dissipation, a higher fracture resistance,
coupled with other practical and design advantages points towards a need to
reassess the codified slenderness limits. Global ductility demands and
capacities are used to assess the behaviour factors recommended for this type
of structure.