Ultra large container ship (ULCS) structures feature large deck openings and low torsional rigidity. It is essential to accurately evaluate the maximum loading carrying capacity of ship structures. ...When the ship sails at an oblique heading in rough sea, the horizontal and torsional moments may approach or even exceed the magnitude of vertical bending moment. In such cases, hull girder ultimate strength assessment of container ships under load combinations comprising of vertical bending moment, horizontal bending moment and torsion is necessary in their structural design stage. In this paper, special attentions are thus paid to the hull girder ultimate strength of an ULCS (i.e., a typical 10,000 TEU container ship) subjected to combined three load components mentioned above, which is also a common load case in ships and ship-shaped offshore structures and it is assumed that the three kinds of main loads can be combined each other freely. A series of nonlinear finite element analyses (NFEA) is carried out. Effects of fabrication related initial imperfections are investigated in the present study. Based on the computed numerical results, the 3D hull girder ultimate strength envelope considering initial deformation and incorporating the interaction relationships among three kinds of load components mentioned above is established.
•The ultimate strength nonlinear behaviours of a typical ULCS considering some key influencing factors were performed.•The ultimate strength interaction relationships between two and three load components were studied.•A simple design formula for predicting 3D ultimate strength envelope was proposed.•Effects of initial imperfections on the ultimate strength interaction among three load components were investigated.
The number and size of aluminium non-monohull ships have been steadily increasing over time. This raises growing concerns regarding their structural strength, especially considering the adverse ...effects of the heat-affected-zone (HAZ) on welding connections in aluminium structures. This paper investigates the ultimate strength of welded aluminium stiffened panels under combined biaxial compressive loads and lateral pressure through the application of numerical simulations. Altogether 360 cases are simulated with varied panel lengths, welding patterns and load combinations. The results are presented and discussed with respect to force end-shortening curves, failure modes and ultimate strength. Influences of the combined loads and HAZ effects are summarized. The numerical results are compared to two commonly used design methods in the marine industry, the International Association of Classification Societies (IACS) rule and the Panel Ultimate Limit States (PULS) approach. Their applicability to welded aluminium stiffened panels is discussed, and modifications are suggested with respect to the transverse loads, lateral pressure, and HAZ effects.
•Investigating behaviour of aluminium panel under combined loads considering welding effects.•Comparing results of NLFEM simulations and predictions from design methods.•Identifying incomplete considerations of lateral loads in design methods.•Recommending potential improvements in the IACS rule to better consider transverse loads.•Proposing integration of welding effects into the IACS rule for aluminium structures.
Pitting corrosion poses a threat to plated steel structures serving in aggressive corrosion environments. This paper involves numerical studies on the structural behaviour and ultimate strength ...reduction of plated steel structures due to random pitting damage. Stochastic simulations were used to model the random nature of the pitting corrosion varying pitting shape, depth and distribution. A series of nonlinear analyses were performed on unstiffened plates and stiffened panels to understand the mechanisms of structural collapse due to random pitting damage. Empirical formulae were derived respectively for the prediction of ultimate strength reductions of unstiffened plates and stiffened panels in terms of regression analysis from the numerical results. Random pitting corrosion induces a variation and reduction in ultimate strength, and can lead to a transition in failure mode. The collapse of pitted structures under uniaxial compression has a feature that the onset of plasticity initiates in the areas close to the unloaded edge of the structure, and propagates into a continuous plasticity region linking the pits with highly concentrated stress. The pitted area with intensively stress-concentrated pits undergoes a locally amplified deformation that determines the failure mode, leading to structural failure.
•Develop a modeling method to simulate random pitting damage on unstiffened plates and stiffened panels•Clarify failure mechanism of structure due to random pitting damage•Study probabilistic characteristics of ultimate strengths of pitted plated structure•Regressive analysis of ultimate strength reduction due to actual pitting damage
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•The utilization of 100% materials for load bearing is achieved by elongating a planar structure along load direction.•A series of Chinese Knot lattice structures with nine tubular ...units and sixteen parallel lines are fabricated by SLM.•For CK structures, the tube wall and plate structure maintain stability when thickness exceeds 0.04 and 0.5 mm, respectively.•The specific strength of the CK structure can surpass 330 MPa∙cm3/g, reaching the highest level for TC4 lattice structures.
Lattice structures possess high specific strength, multi-functionality through innovative structural designs. Here, we proposed an efficient method for the construction of lattice structures by elongating two-dimensional planar patterns along the load direction, which enabled the efficient utilization of 100 % materials for load bearing. Inspired by Chinese Knot (CK), a series of meticulously crafted TC4 lattice structures were fabricated by using selective laser melting. These structures feature nine tubular units arranged in a 3 × 3 matrix interconnected by sixteen parallel plates, and their failure modes were subsequently investigated by uniaxial compression tests. The results show that the specific compressive strength of the CK structure enhances as increasing the density. The detachment between the plate and tube, and the buckling of the plate, lead to the premature failure, which in turn leads to substantial variations in strength, estimated at approximately 80 MPa at ∼ 1.5 g/cm3. When the thickness of the plate exceeds 0.5 mm, and the tube wall thickness exceeds 0.04 mm, the CK structures show high stability and exhibit a 45° shear failure mode. Notably, the specific strength of the CK structure can surpass 330 MPa∙cm3/g, which represents the peak level of specific compressive strength compared to the current TC4 lattice structures.
The features of creating porous materials with a given structure based on the use of magnetic nanoparticles are determined. In addition, the process is carried out in a magnetic field with a voltage ...of 1-2 mT. When the content of magnetic nanocomponents increases to 0.3%, the structural characteristics of the material become better. Ultimate strength increases by 2-3 times. The effect of a qualitative change in the structural characteristics of the foamed material when the content of magnetic nanoparticles is increased by more than 0.3-0.35% is proved. At the same time, the strength of the material is significantly reduced. In this way, the optimal content of nanocomponents, which ensures the greatest strength of the material, is determined.
•High-strength concrete is used in FRP-confined concrete-filled steel tube columns.•The failure mode of the stub column is affected by the number of FRP layer.•GFRP has a more evident effect on the ...axial compressive properties of the stub column.•The steel tube and FRP exhibit evident constraint effect after reaching the ultimate strength.•Calculation methods were established for the ultimate strength and peak strain.
In this study, the axial compressive properties of fiber-reinforced plastic (FRP)-confined high-strength concrete-filled steel tube (HSCFST) stub columns were investigated, and the effects of the steel tube thickness, FRP type, concrete strength, and number of FRP layers were analyzed. The results reveal that fracturing of the FRP and bulging deformation of the steel tube are apparent when the stub column fails. An increase in the concrete strength, thickness of the steel tube, and number of FRP layers effectively improve the ultimate strength of the stub column. Compared with carbon fiber-reinforced plastic (CFRP), glass fiber-reinforced plastic (GFRP) has a more evident effect on improving the ultimate strength and delaying the stiffness degradation of stub columns. Further, a finite element model that accurately simulates the axial compressive behavior of FRP-confined HSCFST stub columns was established to better understand the stress development of the high-strength concrete (HSC), steel tube, and FRP. In addition, a calculation method for the peak strain and ultimate strength of FRP-confined HSCFST stub columns subjected to axial compression loads was developed; this method can accurately predict the actual test results.
•The proposed design method, incorporating design curves and empirical formulas, provides a higher safety margin for stiffened plates under limit lateral pressure (Qlim), indicating the need for ...further consideration of span effects in load capacity.•Location and initial deflection shapes greatly impact the limit state analysis of stiffened plates, affecting the predictive ultimate strength under longitudinal compression and combined loads.•Stiffened plates with stiffener web local buckling-shaped deflections (wb) show lower ultimate strengths compared to traditional stiffener sideways deflection (wos), emphasising the significance of wb in realistic welding conditions.
This study presents an advanced methodology for stiffened plates subjected to combined in-plane longitudinal compression and lateral loads. The proposed methodology is based on comprehensive numerical parametric analyses, and it utilises newly developed design curves for the lateral pressure limit and tailored empirical formulae for stiffened plates to increase the precision of ship structural designs. Plate–stiffener combination (PSC) members are used for the limit state analysis, which introduces various positions and initial deflection shapes specific to the PSC models. Local buckling-shaped deflections of the stiffener web are also incorporated into the analysis, which closely mirrors the real-world welding conditions of stiffened plates and provides deeper insight into their load-bearing capacities. These findings highlight the importance of accurately selecting the positions and initial deflections of stiffeners in PSC-based analyses to ensure that structural predictions are safe and reliable. The proposed method is grounded in conservative PSC models and represents a significant advancement in ship structural design in terms of safety and practicality.
This research introduces a novel design methodology for stiffened plates subjected to combined longitudinal compression and lateral loads, leveraging comprehensive numerical parametric analyses. Central to this approach is the newly developed design curves for limit lateral pressure (Qlim) and empirical formulas tailored for stiffened plates, enhancing the precision in ship structural design. A distinctive feature of this study is the utilisation of plate-stiffener combination (PSC) members in the limit state analysis, meticulously considering various locations and initial deflection shapes specific to PSC models. A critical innovation is the incorporation of stiffener web local buckling initial deflection (wb) into the analysis, closely mirroring real-world welding conditions of stiffened plates and thus offering deeper insights into their load-bearing capacities. The findings underscore the necessity of accurately selecting stiffener locations and initial deflections in PSC-based analyses to ensure more reliable and safer structural predictions. The proposed method, grounded in conservative PSC models, presents a significant advancement in the structural design of ship structures, offering both enhanced safety and practical applicability. Display omitted
Composite bolted joints are commonly used in various load-bearing structures. However, inevitable bolt-hole clearances in bolted joints reduce joint performance. Therefore, an experimental study on ...the influence of washer size in alleviating the adverse effects of bolt-hole clearance in single-lap single-bolt composite joint was conducted. Nine different combinations of washer sizes and bolt-hole clearances were examined. This paper presents experimental bearing analysis, SEM micrographs and failure mechanism. The bearing analysis indicated that the detrimental effects of bolt-hole clearances, i.e., reduction in strength, stiffness, and failure strain, could be mitigated by the use of larger washer sizes in bolted joints. In order to better understand the effect of washer size on internal damages and failure mechanism, SEM imaging at various stages of the loading process was conducted. A closer inspection on the failure mechanisms of various configurations revealed that small washer damages were localised. In contrast, large washer configurations exhibited excessive fibre failure, which allows the joint to absorb more energy before the final failure. These results can be used to develop a mechanism-based model of single-lap single-bolt joints under varying washer sizes.
The main objective of this research is to figure out the relationship of the ultimate strength characteristics between the compartment hull girder and the global hull girder, especially focusing on ...the ultimate strength envelope of the global hull girder of a 10,000TEU ultra large container ship subjected to combined loads, which is one of the most important indexes to quantify the safety margin of the container ship. To achieve these aims, both the compartment hull girder and the global hull girder are modeled based on true ship hull girder's configurations. A series of full-scale nonlinear finite element analyses are performed. In addition, to examine the reliability of the elastic-perfectly plastic material models employed in FEA, similar scale model collapse experiments of a compartment hull girder subjected to pure hogging and pure torsion are also presented. Finally, the ultimate strength envelope of the global hull girder of the 10,000TEU ultra large container ship subjected to combined vertical bending and torsion is quantitatively obtained, which can characterize the container ship hull girder's ultimate strength interactions between vertical bending and torsion and quantify the safety margin of the global hull girder of the container ship subjected to combined vertical bending and torsion.
•Ultimate strength envelope of a global ultra large container ship subjected to combined loads was obtained.•Ultimate strength characteristics of the compartment hull girder and the global hull girder were analyzed.•The elastic-perfectly plastic model employed in ultimate strength analysis was validated based on experiment and FEA.
•A hybrid model coupling particle swarm optimization algorithm with group method of data handling is developed.•Results show the hybrid model can provide accurate ultimate strength forecasts.•A ...comparison among the hybrid model, design codes and literature models is conducted.•A graphical user interface is developed.
This study presents a hybrid model coupling particle swarm optimization (PSO) with group method of data handling (GMDH) for predicting the ultimate strength of rectangular concrete-filled steel tube (RCFST) columns. A large database of 490 data samples collected from the existing literature was used to construct the model. Compared with the optimal model among the nine existing models, the coefficient of variation (COV), mean absolute percentage error (MAPE) and root relative squared error (RRSE) values of all datasets of the PSO-GMDH model were decreased by 58.38 %, 69.22 % and 64.27 %, respectively; while the coefficient of determination (R2) and a20-index values were increased by 34.32 % and 8.65 %, respectively. The results show that the predicted results of PSO-GMDH model are in good agreement with the experimental results and can accurately predict the ultimate strength of rectangular RCFST columns. In addition, a graphical user interface (GUI) has been developed to facilitate the application of the PSO-GMDH model.
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