Analysis and modelling of the seismic behaviour of high ... - Ingegneria
Analysis and modelling of the seismic behaviour of high ... - Ingegneria
Analysis and modelling of the seismic behaviour of high ... - Ingegneria
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4. SEISMIC RESPONSE OF PARTIAL-STRENGTH COMPOSITE JOINTS<br />
4.5 Seismic design <strong>of</strong> <strong>the</strong> composite joint<br />
For moment resisting frame structures, <strong>the</strong> maximum structural ductility is attained<br />
through <strong>the</strong> formation <strong>of</strong> global mechanisms (Gioncu et al., 2002). To this end, it is<br />
necessary to foresee sufficient overstrength <strong>of</strong> <strong>the</strong> columns satisfying <strong>the</strong> relation:<br />
where<br />
110<br />
M ≥ 1.3 ⋅ M<br />
( 4.3 )<br />
Rc Rb<br />
M Rc is <strong>the</strong> sum <strong>of</strong> moments corresponding to <strong>the</strong> development <strong>of</strong> <strong>the</strong><br />
design values <strong>of</strong> <strong>the</strong> resisting moments <strong>of</strong> <strong>the</strong> columns;<br />
M Rb is <strong>the</strong> sum <strong>of</strong> moments corresponding to <strong>the</strong> development <strong>of</strong> <strong>the</strong><br />
design values <strong>of</strong> <strong>the</strong> resisting moments <strong>of</strong> <strong>the</strong> partial strength<br />
joints.<br />
The ductile <strong>behaviour</strong> <strong>of</strong> <strong>the</strong> joints is guaranteed by defining an appropriate<br />
hierarchy <strong>of</strong> resistance for each component. In this respect, with reference to<br />
sagging moments, <strong>the</strong> end-plate <strong>and</strong> <strong>the</strong> column flange under bending as well as<br />
<strong>the</strong> column web panel in shear have to be considered ductile components;<br />
whereas <strong>the</strong> concrete slab under compression <strong>and</strong> <strong>the</strong> bolts under tension are<br />
assumed to be brittle.<br />
With regard to hogging moments, <strong>the</strong> steel rebars under tension <strong>and</strong>, once again,<br />
<strong>the</strong> end-plate <strong>and</strong> <strong>the</strong> column flange under bending, as well as <strong>the</strong> column web<br />
panel under shear are considered ductile components; while <strong>the</strong> column web panel<br />
<strong>and</strong> <strong>the</strong> beam flanges under compression are assumed to be brittle. Brittle failure<br />
<strong>of</strong> <strong>the</strong> bolts in tension before yielding <strong>of</strong> <strong>the</strong> end plate <strong>and</strong>/or <strong>of</strong> <strong>the</strong> column flange<br />
can be easily averted by satisfying <strong>the</strong> following relation:<br />
f<br />
t ≥ 0.36 ⋅d ⋅ ub<br />
( 4.4 )<br />
f<br />
y<br />
where t is <strong>the</strong> thickness <strong>of</strong> <strong>the</strong> end plate or <strong>of</strong> <strong>the</strong> column flange; d <strong>and</strong> fub are <strong>the</strong><br />
nominal diameter <strong>and</strong> ultimate tensile stress <strong>of</strong> <strong>the</strong> bolts, respectively; <strong>and</strong> fy <strong>the</strong><br />
yielding stress <strong>of</strong> <strong>the</strong> base materials <strong>of</strong> <strong>the</strong> considered component (prEN 1993-1,<br />
2000). For <strong>the</strong> remaining components, we applied <strong>the</strong> capacity design according to<br />
Table 4.2 <strong>and</strong> Table 4.3, respectively. It is also necessary to ensure that <strong>the</strong> joint<br />
possesses adequate resistance <strong>and</strong> rotational capacity.