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

4. SEISMIC RESPONSE OF PARTIAL-STRENGTH COMPOSITE JOINTS
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M M − 2⋅
M
V = + − V ( 4.22 )
− + −
pl, Rd , conn pl, Rd , conn gravity
wp, Ed , eff −
z eq
+
z eq
c
where:
M -
pl,Rd,conn is the ultimate strength of the connection for hogging bending
moments;
M +
pl,Rd,conn is the ultimate strength of the connection for sagging bending
moments;
M -
graity is the bending moment, due to dead loads;
z -
eq is the equivalent lever arm in the connection for hogging moment;
z +
eq is the equivalent lever arm in the connection for sagging moment;
Vc is the average shear force at collapse in the web panel equal to:
V
c
V + V M + M
= =
2
z + z
Hc
−
2
− −
column, up column, botton pl, Rd , conn pl, Rd , conn
where Hc is the height of the web panel.
− +
eq eq
( 4.23 )
In obtaining the shear forces in the column segments outside of the panel zone, it
is often assumed that:
(a) the zero-moment points are located in the middle section of the
columns;
M M
= is satisfied.
(b) the equilibrium condition pl, Rd , conn column
4.5.3 Joint rotational capacity evaluation
With regard to rotational capacity, every joint must be able to develop the
necessary plastic rotation upon formation of a global mechanism. Eurocode 8
(2002) prescribes that the rotational capacity θp of the plastic hinges, defined as θ p
= δ / 0.5 L, see Figure 4.14, should be greater than 35 mrad for structures of
ductility class H, and 25 mrad for ductility class M structures, with behavioural
coefficient q > 2. Such values must be obtained for cyclic loads with a reduction in
strength and/or stiffness of less than or equal to 20%, and must be corroborated by
experiments (prEN 1998-1, 2001).
The rotational capacity of the beam-to-column joint was computed using the
component method (Eurocode 4, 2001), suitably modified in order to take into