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

4. SEISMIC RESPONSE OF PARTIAL-STRENGTH COMPOSITE JOINTS
thin end-plate connection, illustrated in Figure 3, has been chosen, which
guarantees predictable and efficient performance for seismic actions. The details of
an exterior beam-to-column joint are illustrated in Figure 4.7. The connections are
partially restrained, or semi-rigid, extended end plate connections. On the basis of
constructional considerations and of the favourable seismic behaviour of the
column web panel, the solution adopted relies on naked steel columns. In detail,
the reinforced concrete encasement is interrupted in the connection, as shown in
Figure 4.7. A pair of stiffening plates, set horizontally and welded to the column,
guarantees full exploitation of the web panel's inelastic resources. Additional φ 12
transverse and longitudinal reinforcing steel is placed in the floor slab at joint
locations so that the slab participates to the transfer of bending moments between
the columns and the beams.
Critical Length
106
Seismic steel rebars
Main
beam
Steel Column
Seismic steel
rebars
270
135
220
Figure 4.7. Details of the beam-column at the exterior joints
150
The transverse beams are IPE240 sections and simple shear connections are
used at their ends. No shear studs are welded to the beams, so that their
contribution to the lateral resistance in the direction of loading is negligible. The
transverse lateral bracing is an X-bracing made with L50x100x8 angles, as shown
in Figure 4.8.
The specifications for the structural materials are:
• Structural steel: Class S235 (fy = 235 MPa, fu = 360 MPa, u = 28%)
• Concrete: Class C25/30 (f’c = 25 MPa)
• Reinforcing Steel: Class B450-C (fy = 450 MPa, fy/fu < 1.35, u = 7.5%)