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

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