Overstrength demands for joints in composite frames with account of the actual European steel production

Srour Nofal (1) , Hugues Somja (1) , Mohammed Hjiaj (1) , Quang Huy Nguyen (1)

1 Geosax [LGCGM]

In the design of moment resisting frames under severe seismic action the dissipation of the earthquake input energy is expected to happen at the beam ends. This can be obtained through the yielding of the ductile components of the connections, or through the formation of a plastic hinge in the member aside the joint. This last solution provides a large amount of plastic deformation and is the most structurally efficient. But plastic hinges can only develop if beam to column joints possess a sufficient overstrength. This is recognised by modern seismic codes, but different values are suggested to ensure this design goal. In the frame of the European RFCS research OPUS the mechanical properties of steel profiles and reinforcement bars produced in several European steel plants have been collected, and the statistical distribution of the resistances of the steel products have been established. Several steel and composite structures have been designed following the EN 1998 rules. Then the effect of the statistical distribution of the steel properties on the design has been analysed. This article focuses on the study of the overstrength needs for joints in composite moment resisting frames. Following EN1998, the non dissipative joints must be designed to resist to the forces Rd = 1.1 ov Rfy, Rfy being the plastic resistance of the dissipative member based on the design value of the yielding stresses. This condition is verified in comparison to the actual European steel production. First the statistical distribution of maximum beam moments in sagging zone is determined through a multifiber model. Then the distribution of the maximum hogging moment is computed through the same model, coupled with the model of Gioncu which provide the post buckling behaviour of the beam. This model is based on the plastic collapse mechanism theory and takes into account the local buckling of the compressed flange. Then the overstrengths needed for the different kind of components of the joint are discussed, taking into account the steel and concrete variability

Domaines: Génie civil

Srour Nofal, Hugues Somja, Mohammed Hjiaj, Quang Huy Nguyen. Overstrength demands for joints in composite frames with account of the actual European steel production. 6th European Conference on Steel and Composite Structures, Aug 2011, Hungary. pp.453-458. ⟨hal-00965656⟩