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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3. SEISMIC BEHAVIOUR OF BOLTED END PLATE BEAM-TO-COLUMN STEEL JOINTS<br />
Figure 3.36. Von Mises stress distribution on <strong>the</strong> deformed joint configuration<br />
High tensile residual stresses are known to promote brittle fracture <strong>and</strong> fatigue; <strong>and</strong><br />
for fatigue problems, <strong>the</strong> residual stresses appear as mean stresses imposed on<br />
<strong>the</strong> exterior damage-inducing stress cycles. Thereby, both <strong>the</strong> magnitude <strong>and</strong> <strong>the</strong><br />
distribution <strong>of</strong> residual stresses need to be included to accurately estimate weld<br />
fatigue life (Zhang <strong>and</strong> Dong, 2000). In a view to confirming <strong>the</strong> hypo<strong>the</strong>ses <strong>of</strong> 2D<br />
analyses, a sub-model shown in Figure 3.37 was developed to obtain increased<br />
accuracy in <strong>the</strong> computed local stress-strain state <strong>of</strong> <strong>the</strong> beam flange region <strong>of</strong> <strong>the</strong><br />
connection due to weld residual stress, where <strong>the</strong> connection has <strong>the</strong> <strong>high</strong>est<br />
fracture potential. Figure 3.37 depicts a substructure composed <strong>of</strong> 9314 DC3D20<br />
elements <strong>of</strong> <strong>the</strong> JB1-3 joint, which was subjected to a total effective <strong>the</strong>rmal input<br />
<strong>of</strong> 10.08 kW according to <strong>the</strong> parameters <strong>of</strong> Table 3.7, with a total arc efficiency<br />
equal to 0.9. The displacement results <strong>of</strong> <strong>the</strong> global model are used for <strong>the</strong><br />
boundary conditions around <strong>the</strong> perimeter boundary <strong>of</strong> <strong>the</strong> sub-model.<br />
84<br />
Solid wire<br />
(1,2 mm diameter)<br />
Arc voltage<br />
(V)<br />
Welding current<br />
(A)<br />
Arc travel speed<br />
(mm/s)<br />
AWSA5.18–R70S-6 32 350 5<br />
Table 3.7. Welding parameters adopted for partial fillet welds<br />
The distribution <strong>of</strong> residual stresses provided by <strong>the</strong> substructure along <strong>the</strong> flange<br />
thickness is reported in Figure 3.38, for three different flange sections. One may<br />
observe <strong>the</strong> variability <strong>of</strong> longitudinal stresses along <strong>the</strong> flange width; moreover,<br />
<strong>the</strong> distribution <strong>of</strong> residual stresses exploited in <strong>the</strong> 2D model, is inaccurate only at<br />
<strong>the</strong> top surface <strong>of</strong> <strong>the</strong> end plate.