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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5. SEISMIC BEHAVIOUR OF RC COLUMNS EMBEDDING STEEL PROFILES<br />
The analytical values obtained from <strong>the</strong> previous equations well agree with <strong>the</strong> true<br />
joint shear resistances obtained from <strong>the</strong> experimental tests in <strong>the</strong> case that, an<br />
increase in <strong>the</strong> shear resistance <strong>of</strong> <strong>the</strong> steel web panel (when subjected to <strong>high</strong><br />
cyclic strains) is allowed. Hence, in equation 5.18, <strong>the</strong> factor 1/√3 is substituted by<br />
a value equal to unity:<br />
240<br />
f ym, d , cw<br />
Vj , wps = 0,7 ⋅ ⋅min( Av ; tcw ⋅ ds ) + ∆ Vj<br />
, swp<br />
( 5.74 )<br />
1<br />
Note that, in this phase, <strong>the</strong> single mechanism resistance evaluated by means<br />
<strong>of</strong> <strong>the</strong> analytical model, does not take into account <strong>the</strong> partial safety factor value<br />
equal to 1,3 as prescribed by <strong>the</strong> Capacity Design Principle. Fur<strong>the</strong>rmore, <strong>the</strong><br />
resistance values are determined considering <strong>the</strong> real material strengths obtained<br />
from specific tests conducted on concrete <strong>and</strong> steel samples. In fact, it is intended<br />
to make a direct comparison to establish <strong>the</strong> precision <strong>of</strong> <strong>the</strong> proposed analytical<br />
equations. Of course, at <strong>the</strong> design stage, it is necessary to account for all <strong>the</strong><br />
relevant safety factors as already foreseen in <strong>the</strong> equations previously presented.<br />
By means <strong>of</strong> <strong>the</strong>se modifications it was possible to calibrate <strong>the</strong> proposed<br />
analytical formulas: a substantial increase in <strong>the</strong> accuracy <strong>of</strong> <strong>the</strong> predicted joint<br />
shear resistance compared with that obtained from <strong>the</strong> experimental results. The<br />
difference between <strong>the</strong> analytical <strong>and</strong> experimental results has been modified from<br />
a 20% to a 5% <strong>of</strong> error, as reported in <strong>the</strong> Table.<br />
5.8 Conclusions<br />
This part <strong>of</strong> <strong>the</strong> Ph.D. <strong>the</strong>sis has been written with <strong>the</strong> intent <strong>of</strong> underlining <strong>the</strong><br />
importance <strong>of</strong> <strong>the</strong> studies conducted on Innovative Beam-to-Column Composite<br />
Joints in order to provide <strong>the</strong> reinforced concrete structures <strong>of</strong> <strong>the</strong> necessary<br />
amount <strong>of</strong> ductility in those critical zones usually strongly affected by <strong>the</strong><br />
occurrence <strong>of</strong> <strong>seismic</strong> events. The general recommendation is to reinforce some<br />
strategic points <strong>of</strong> <strong>the</strong> building, as <strong>the</strong> joints <strong>of</strong> <strong>the</strong> 1 st storey, allowing in this<br />
manner to save <strong>the</strong> structure from a global collapse due to localised brittle type <strong>of</strong><br />
failures. Both <strong>the</strong> solutions studied, with long <strong>and</strong> short steel pr<strong>of</strong>ile encased in <strong>the</strong><br />
concrete column, as expected, revealed to be effective in order to greatly improve<br />
<strong>the</strong> performance <strong>of</strong> <strong>the</strong> concrete members in terms <strong>of</strong> strength <strong>and</strong> ductility at large<br />
deformations. In fact, it can be stated that also <strong>the</strong> short steel pr<strong>of</strong>ile stump is able<br />
to guarantee an adequate amount <strong>of</strong> resistance <strong>and</strong> ductility at <strong>the</strong> joint critical