The structural state of several cast iron lighthouses in the Netherlands has been deteriorating, as cracks have formed in the cast iron plates of the columns. Current assessment methods of such large cast iron plate structures require a very detailed finite element model, which is time consuming to create and analyse. In this thesis, the use of an orthotropic continuum damage model, the Engineering Masonry Model (EMM) of DIANA FEA in this case, for the structural analysis of cast iron plate structures is explored. The thesis focuses on a specific case: the lighthouse the ‘Lange Jaap’, located in Den Helder, the Netherlands.

First, to obtain the required input parameters for an orthotropic continuum damage model,
detailed models of small plate structures are created. Different loading conditions are applied, and the resulting force-displacement curves are analysed to derive constitutive laws for the structural analysis. Next, a sensitivity study of the size effect of the structure is performed, which resulted in some changes in the failure modes for some of the loading types. This resulted in quite a difference in strength and ultimate strain between the small and large structures. For each load case, a unit structure size should be defined, which should have the same failure modes as those expected to occur in the large structure the study focuses on. After obtaining the input parameters, they are verified and calibrated by using them in equivalent EMM models of the small plate structures.

The final, calibrated input parameters were used in an orthotropic continuum damage model for the cast iron plate structure of lighthouse the Lange Jaap and it was concluded that very similar results were obtained as from a detailed model, when all strains were in the linear-elastic regime. As the obtained values of the bed- and head-joint tensile strengths that were quite low, the tensile stresses exceeded the tensile strength of the material quite quickly in the model of the lighthouse. Once plastic deformations occurred, cracks started to form and the analysis of the model quickly became unstable, so the results were no longer accurate. This shows that, after the calibration of the parameters, the linear-elastic behaviour of the structure is accurately captured in the model, while the plastic behaviour is not.

It is concluded that, by using an orthotropic continuum damage model, the complexity of a structural analysis of a cast iron plate structure is reduced in the following way: reduced total modelling time, reduced complexity of geometry and reduced running time of analysis. The last point is achieved by using regular curved shell elements instead of structural solids, which is the result of the simplification in geometry. Using an orthotropic continuum damage model for similar structures is a very suitable modelling method for studies in which many finite element analyses have to be made for a structure, where small changes are made in every analysis. For the lighthouse structure, a study of the effectiveness of different strengthening solutions for the columns is a very good example.