LG
L. García Rebollo
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Hybrid Steel–Composite Box Girders for Naval Vessels
A quasi-static collapse assessment using progressive collapse and finite element models
Composite materials offer opportunities to reduce the structural mass of naval vessels, but their integration into primary hull structures changes the stiffness distribution, load transfer and mechanisms governing collapse. This thesis investigates how selective steel-composite hybridisation of a naval hull girder region influences its quasi-static progressive collapse behaviour and ultimate bending response. The assessment focuses on intact structures subjected to monotonic longitudinal bending.
A Smith-type progressive collapse model was adapted to represent steel and composite component responses, neutral-axis migration and reduced composite participation at the steel-composite interface. An all-steel reference box and three hybrid concepts incorporating Glass-Fibre Reinforced Polymer (GFRP) were evaluated using monolithic laminate and sandwich panels, first as isolated box girders and subsequently within a reference frigate cross-section. The steel formulation was assessed against the published Nishihara MST-3 experimental benchmark. Nonlinear finite element analyses in ANSYS provided component load-shortening curves for comparison within the same sectional solver, while separate complete-box models examined wall interaction and cohesive adhesive behaviour. Sensitivity analyses assessed the influence of material properties, interface participation and modelling assumptions.
Among the investigated concepts, B3, which replaces the side webs with GFRP while retaining the steel deck, bottom flange and corner framing, provided the most favourable balance between mass reduction, bending resistance and dependence on composite participation. In the analytical isolated-box assessment, the monolithic B3 design was 11.6% lighter than the steel reference while meeting or exceeding its sagging and hogging capacities. Following embedding and recalibration within the frigate cross-section, it reduced structural mass by 52.1 kg⋅m−1 relative to the section containing steel reference boxes, maintaining sagging capacity with a 1.17% reduction in hogging capacity. Sandwich variants offered no meaningful mass advantage within the adopted longitudinal-bending model.
The finite element comparisons showed that the predicted resistance depends on how component behaviour and structural interaction are represented. Using finite element component curves produced ultimate moments 0.7–17.5% below the corresponding analytical predictions. This sectional assessment predicted lower sagging resistance for B3 than for the steel reference, while its small hogging advanta
...
A Smith-type progressive collapse model was adapted to represent steel and composite component responses, neutral-axis migration and reduced composite participation at the steel-composite interface. An all-steel reference box and three hybrid concepts incorporating Glass-Fibre Reinforced Polymer (GFRP) were evaluated using monolithic laminate and sandwich panels, first as isolated box girders and subsequently within a reference frigate cross-section. The steel formulation was assessed against the published Nishihara MST-3 experimental benchmark. Nonlinear finite element analyses in ANSYS provided component load-shortening curves for comparison within the same sectional solver, while separate complete-box models examined wall interaction and cohesive adhesive behaviour. Sensitivity analyses assessed the influence of material properties, interface participation and modelling assumptions.
Among the investigated concepts, B3, which replaces the side webs with GFRP while retaining the steel deck, bottom flange and corner framing, provided the most favourable balance between mass reduction, bending resistance and dependence on composite participation. In the analytical isolated-box assessment, the monolithic B3 design was 11.6% lighter than the steel reference while meeting or exceeding its sagging and hogging capacities. Following embedding and recalibration within the frigate cross-section, it reduced structural mass by 52.1 kg⋅m−1 relative to the section containing steel reference boxes, maintaining sagging capacity with a 1.17% reduction in hogging capacity. Sandwich variants offered no meaningful mass advantage within the adopted longitudinal-bending model.
The finite element comparisons showed that the predicted resistance depends on how component behaviour and structural interaction are represented. Using finite element component curves produced ultimate moments 0.7–17.5% below the corresponding analytical predictions. This sectional assessment predicted lower sagging resistance for B3 than for the steel reference, while its small hogging advanta
...
Composite materials offer opportunities to reduce the structural mass of naval vessels, but their integration into primary hull structures changes the stiffness distribution, load transfer and mechanisms governing collapse. This thesis investigates how selective steel-composite hybridisation of a naval hull girder region influences its quasi-static progressive collapse behaviour and ultimate bending response. The assessment focuses on intact structures subjected to monotonic longitudinal bending.
A Smith-type progressive collapse model was adapted to represent steel and composite component responses, neutral-axis migration and reduced composite participation at the steel-composite interface. An all-steel reference box and three hybrid concepts incorporating Glass-Fibre Reinforced Polymer (GFRP) were evaluated using monolithic laminate and sandwich panels, first as isolated box girders and subsequently within a reference frigate cross-section. The steel formulation was assessed against the published Nishihara MST-3 experimental benchmark. Nonlinear finite element analyses in ANSYS provided component load-shortening curves for comparison within the same sectional solver, while separate complete-box models examined wall interaction and cohesive adhesive behaviour. Sensitivity analyses assessed the influence of material properties, interface participation and modelling assumptions.
Among the investigated concepts, B3, which replaces the side webs with GFRP while retaining the steel deck, bottom flange and corner framing, provided the most favourable balance between mass reduction, bending resistance and dependence on composite participation. In the analytical isolated-box assessment, the monolithic B3 design was 11.6% lighter than the steel reference while meeting or exceeding its sagging and hogging capacities. Following embedding and recalibration within the frigate cross-section, it reduced structural mass by 52.1 kg⋅m−1 relative to the section containing steel reference boxes, maintaining sagging capacity with a 1.17% reduction in hogging capacity. Sandwich variants offered no meaningful mass advantage within the adopted longitudinal-bending model.
The finite element comparisons showed that the predicted resistance depends on how component behaviour and structural interaction are represented. Using finite element component curves produced ultimate moments 0.7–17.5% below the corresponding analytical predictions. This sectional assessment predicted lower sagging resistance for B3 than for the steel reference, while its small hogging advanta
A Smith-type progressive collapse model was adapted to represent steel and composite component responses, neutral-axis migration and reduced composite participation at the steel-composite interface. An all-steel reference box and three hybrid concepts incorporating Glass-Fibre Reinforced Polymer (GFRP) were evaluated using monolithic laminate and sandwich panels, first as isolated box girders and subsequently within a reference frigate cross-section. The steel formulation was assessed against the published Nishihara MST-3 experimental benchmark. Nonlinear finite element analyses in ANSYS provided component load-shortening curves for comparison within the same sectional solver, while separate complete-box models examined wall interaction and cohesive adhesive behaviour. Sensitivity analyses assessed the influence of material properties, interface participation and modelling assumptions.
Among the investigated concepts, B3, which replaces the side webs with GFRP while retaining the steel deck, bottom flange and corner framing, provided the most favourable balance between mass reduction, bending resistance and dependence on composite participation. In the analytical isolated-box assessment, the monolithic B3 design was 11.6% lighter than the steel reference while meeting or exceeding its sagging and hogging capacities. Following embedding and recalibration within the frigate cross-section, it reduced structural mass by 52.1 kg⋅m−1 relative to the section containing steel reference boxes, maintaining sagging capacity with a 1.17% reduction in hogging capacity. Sandwich variants offered no meaningful mass advantage within the adopted longitudinal-bending model.
The finite element comparisons showed that the predicted resistance depends on how component behaviour and structural interaction are represented. Using finite element component curves produced ultimate moments 0.7–17.5% below the corresponding analytical predictions. This sectional assessment predicted lower sagging resistance for B3 than for the steel reference, while its small hogging advanta