Nonlinear finite element analyses are performed to
determine the ultimate strength of a double hull VLCC under
pure vertical, horizontal and biaxial bending. A parametric finite
element model is developed and the influence of nonlinear
material behavior, mesh size and model length on the hull girder
ultimate strength is demonstrated exemplarily for hogging and
sagging conditions. An appropriate parameter configuration
with respect to numerical efforts and accuracy is used to perform
static implicit analyses for horizontal bending and biaxial load
cases. Convergence is reached by using the full Newton-Raphson
scheme - an incremental iterative solution approach. The results
are validated against the well-established Smith method. Due to
welding, initial deflections and residual stresses are produced.
For the proposed finite element model initial deflections of
plating and stiffeners have been considered. Furthermore, the
influence of welding residual stresses on the ultimate hull girder
strength is demonstrated for the different load cases. Nonlinear
finite element analyses are also performed to determine the
residual strength of the damaged double hull VLCC under
combined loads. Different symmetric grounding damages are
implemented by removing structural components of the model.
Expectedly, the results show that the ultimate strength of the
structure decreases as the damage extent increases
