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

5. SEISMIC BEHAVIOUR OF RC COLUMNS EMBEDDING STEEL PROFILES
For a single-sided joint, or a double-sided joint in which the beam depths are
similar, the design shear resistance of concrete encasement into the column web
panel depends by the following geometrical and mechanical parameters:
( ) θ ( )
A = 0.8⋅ h − 2⋅ t ⋅cos ⋅ b − t
( 5.26 )
c c cf cf cw
Nsd
ν = 0.55⋅ 1+ 2⋅ ≤ 1.1
( 5.27 )
N
pl, Rd
h 2
1 c − ⋅t
− cf
θ = tan
( 5.28 )
z
For connections with contact plates, the center of compression should be assumed
to be in line with the mid-thickness of the compression flange. For connections with
contact plates and only one row of reinforcement active in tension, the lever arm z
should be taken as the distance from the center of compression to the row of
reinforcement in tension. For connections with contact plates and two rows of
reinforcements active in tension the lever arm z should be taken as the distance
from the center of compression to a midway point between these two rows,
provided that the two rows have the same cross-sectional area. In the formulation
above, ν is a multiplier factor which accounts for the column axial load effects on
the joint shear resistance, following the prescriptions of Eurocode 2.
Bearing Failure
The horizontal bearing strength Vjoint,hb is determined through a standard Stress
Block model similar to that used for flexural strength calculation in reinforced
concrete members. The shear resistance and the moment resistance for the
concrete compression strut are calculated as follows:
1 f
V = ⋅ 0.85⋅
⋅a ⋅ b
( 5.29 )
j, hb
1.3
ck , c
γ c
c cf
( )
M = V ⋅ h − a
( 5.30 )
Rd , j, hb j, hb b c
To evaluate this resistance it is of primary importance to be able to guarantee an
adequate concrete confinement inserting a proper ties quantitative which enhances
the concrete performance. Confinement of concrete results in a modification of the
effective stress-strain relationship: higher strength and higher critical strains are
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