Analysis and modelling of the seismic behaviour of high ... - Ingegneria

5. SEISMIC BEHAVIOUR OF RC COLUMNS EMBEDDING STEEL PROFILES
By considering the prescription both of Eurocode 2 and Eurocode 8, within the
critical region the most restrictive of the following conditions should be satisfied.
Eurocode 2
LCR (critical regions length): 720 mm
Hoops spacing in the critical regions: 180 mm
Eurocode 8: to satisfy plastic rotation demands and to compensate for loss of
resistance due to spalling of concrete cover
LCR (critical regions length): 700 mm
Hoops spacing in the critical regions: 150 mm
5.3.5 Design of the fully encased composite columns
To ease and promote the utilisation of composite columns in seismic geographical
areas in order to obviate the Soft Storey type of building failure, the steel profiles
for strong and weak axis bending have been chosen by matching simple design
criteria developed at the University of Liege. This constructional measure should:
• provide ductility;
• maintain axial strength, (plastic) shear and moment resistance, and stiffness
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similar to those of the RC column at the ultimate stage when concrete is locally
crushed.
The following design criteria have been defined, in order to allow the achievement
of the mentioned target.
1. The steel section should at least be able to take alone the design axial force of
the seismic loading case:
NRd > NSd (γgG + γqQ) ( 5.10 )
with:
γg = 1
γq = 0.3
2. The steel section alone (not acting composedly) should be able to substitute
the deficient concrete section:
MRd,steel > MRd,concrete ( 5.11 )
VRd,steel > VRd,concrete ( 5.12 )