Enhancing Fishing Boat Safety: Optimized Impact Side Beam Design for Improved Hull Protection

Fishing vessel accidents are a significant concern due to the high number of fatalities they cause, emphasizing the need for improved safety measures in the fishing industry. Studies shed light on the patterns and factors influencing these accidents [1, 2] while other research specifically focuses on the operability of traditional small fishing boats in Indonesia, highlighting various operational aspects contributing to accidents [3, 4]. In the realm of ship construction and collision prevention, understanding various factors is crucial [5, 6]. Further research emphasizes the significance of determining the hull girder strength post-damage to assess collision resilience [7, 8]. Analyzing ship collision energy and structural damage across different scenarios provides insights for construction improvements [9, 10]. Additionally, factors like vessel speed and crew number play a role in collision accidents, guiding safety measures and structural enhancements [11, 12].

Preventing ship collisions is paramount for maritime safety [13]. Research focuses on collision damage and energy absorption analysis, while other studies delve into developing collision models for fishing boats and ferry car decks, respectively [14, 15]. These diverse perspectives underscore the multifaceted nature of ship collision prevention, encompassing technological, human, and structural dimensions [16]. This study introduces an innovative approach to installing stiffeners on the sides of ships susceptible to collisions [17]. In maritime applications, integrating such stiffeners on the sides of ships could increase the vessel's resistance to collision forces [18, 19]. This could minimize structural damage and ensure the safety of the crew and cargo. This research aims to explore this concept further, investigating the feasibility and effectiveness of such an approach in improving maritime safety. Future work will involve rigorous testing and analysis to validate the proposed design and assess its impact on overall ship safety. This study contributes to the ongoing efforts in maritime safety research, offering a novel perspective on ship design and collision prevention.

This study employed a combination of simulations using ANSYS and drop test experiments to investigate the design of the side beam impact installation model on the ship's side [20]. The primary objective was to identify a design that maximizes energy absorption, thereby enhancing the safety of fishing vessels during collisions. The ANSYS simulations provided a detailed understanding of the structural behaviour of the side beam impact installation under various collision scenarios [21]. These simulations facilitated the visualization of the design's stress distribution, deformation patterns, and energy absorption characteristics under different impact conditions [22].

Research on structural crashworthiness has been a focal point for many researchers, aiming to enhance the safety of structures under impact loading conditions [23]. Various studies have explored approaches to improve crashworthiness, such as utilizing thin-walled tubular components for energy absorption [24]. Additionally, investigations have been conducted on the crash mechanisms of structures, the impact of uncertainties on crash behaviour, and the optimization of crashworthiness designs for effectiveness and efficiency [25]. Moreover, advancements in crashworthiness applications have led to a shift towards using composite materials in energy-absorbing structures, showcasing their potential for enhancing crashworthiness [26]. Furthermore, specific materials like FRP composites have been studied for improving vehicle crashworthiness by serving as collapsible absorbers of crash energy [27]. Studies have also delved into the crashworthiness of hybrid structures, demonstrating that fibre/metal hybrid materials can offer improved crashworthiness compared to traditional metal structures [28]. Moreover, the crashworthiness of structures like composite hat shapes has been explored for applications in vehicle safety, highlighting their suitability for side-impact crashworthiness [29].

Complementing the ANSYS simulations, drop-test experiments were conducted to validate the simulation results and provide real-world insights into the performance of the side beam impact installation. These experiments involved weighting onto the side beam impact installation and measuring the resulting deformation and energy absorption. The combination of ANSYS simulations and drop test experiments comprehensively evaluated the side beam impact installation design. The findings from this study will contribute to the development of safer and more resilient fishing vessels capable of withstanding collisions and protecting the crew and cargo onboard. This research underscores the importance of innovative design and rigorous testing in enhancing maritime safety.

The crashworthiness of alloy fishing boats has been a focal point in research, particularly concerning hull performance and structural integrity during collision scenarios. Computational methods, such as finite element analysis, have significantly contributed to understanding ship hull performance under various conditions, leading to safer and more efficient ship designs [19, 44]. The utilization of computational simulations, especially with ANSYS LS-Dyna, has provided valuable insights into the crashworthiness of alloy fishing boats, offering a deeper understanding of maximum deformation in the crash area and enabling comparative analyses of different collision scenarios [45]

Recent studies have highlighted the effectiveness of incorporating stiffeners, such as longitudinals and brackets, in the hull design of alloy fishing boats to enhance structural integrity under diverse loading conditions. This aligns with findings emphasizing the importance of stiffeners in improving the crashworthiness of these boats. Moreover, the incorporation of stiffeners has been shown to enhance the ultimate compressive strength of panels, with different types of stiffeners like T-bar, flat-bar, and angle-bar being commonly used in shipbuilding. Using stiffeners, in conjunction with advanced computational tools, has proven crucial in optimizing alloy fishing boats' crashworthiness and structural performance under varying conditions. In conclusion, integrating stiffeners and advanced computational simulations, particularly with ANSYS LS-Dyna, plays a vital role in enhancing the crashworthiness of alloy fishing boats by improving hull performance and structural integrity under collision scenarios. These approaches offer valuable insights into deformation patterns, comparative analyses, and the safety of alloy fishing boats, contributing to developing more robust and efficient ship designs.

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Figure 6. E-20 stiffener ID: (a) Crash area, (b) deformation in mm, (c) stress in MPa

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Figure 7. E-30 stiffener ID: (a) Crash area, (b) deformation in mm, (c) stress in MPa

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Figure 8. B-20 stiffener ID: (a) Crash area, (b) deformation in mm, (c) stress in MPa

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Figure 9. Trns-B-30 stiffener ID: (a) Crash area, (b) deformation in mm, (c) stress in MPa

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Figure 10. Trns-T-20 stiffener ID: (a) Crash area, (b) deformation in mm, (c) stress in MPa

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Figure 11. Long-B-20 stiffener ID: (a) Crash area, (b) deformation in mm, (c) stress in MPa

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Figure 12. Trns-T-30 stiffener ID: (a) Crash area, (b) deformation in mm, (c) stress in Mpa

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The presented study used computer simulations to analyze the deformation and stress magnitudes in various ship hull impact models. The results of these simulations are comprehensively illustrated in Figures 6-13. Several models were compared, including a ship hull model without side beam impact reinforcement (Figures 6 and 7) and an alloy fishing boat hull model reinforced transversely and longitudinally. The reinforced model was further examined under two distinct conditions, with impact speeds of 20 and 30 knots, respectively. This multi-faceted approach allowed for a thorough investigation of the influence of speed on the structural resilience of the reinforced ship hull. Insights gained from this study are expected to significantly contribute to ongoing discussions on ship hull design and safety, thereby paving the way for future research and practical applications.

The simulation outcomes, obtained through the utilization of ANSYS, encompass a range of side beams impact variations. These results, which include the degree of deformation, maximum stress, and energy absorption, are comprehensively presented in Table 3 and Figure 14. EA is defined as the total energy absorbed, calculated as the integral of force over deformation. This data provides a robust understanding of the performance characteristics under different reinforcement conditions.

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Figure 14. Energy absorption for variation of side beams impact

An investigation has established a direct correlation between collision speed and the ensuing deformation of a ship’s hull. Notably, a collision speed of 20 knots resulted in a deformation of approximately 51.5 mm, which escalated to an estimated 77 mm at 30 knots. While alterations in profile and angle of impact on the side beam had a lesser effect on deformation magnitude, they significantly influenced EA. This is particularly evident when comparing transverse vs. longitudinal installations, where reinforcement orientation alters load distribution and resulting energy dissipation. These distinctions reflect the theoretical EA model and validate simulation observations with experimental trends.

The study's objective was to evaluate the impact of various types of additional stiffeners on the EA of ship structures under impact loads. EA, the area under the reaction force curve versus deformation, represents the energy the ship structure can absorb before failure [46, 47]. Various ship structures with different configurations of additional stiffeners were analyzed using ANSYS software. The impact speed ranged from 20 to 30 knots, and the EA value was computed for each case. The results confirmed that EA increased with impact speed across all cases. Notably, a key finding is that the transverse installation of bar profiles achieves superior EA at 20 knots, whereas the longitudinal T profile yields the highest EA at 30 knots. This demonstrates a performance–speed synergy between profile type and installation direction, offering a practical optimization strategy [48, 49]. However, the current study was conducted on a scaled-down (1:2) model of the fishing boat hull, which limits the direct applicability to full-scale vessels. The generalizability of these findings to real-world, full-scale applications can be inferred, but further validation with actual-sized hulls is necessary. Furthermore, while 5083-H116 alloy proved optimal in this study, alternative materials (e.g., composites, hybrid alloys) could offer different energy absorption and durability characteristics, warranting future testing.

At a collision speed of 30 knots, the configurations that yielded the highest EA were Long_T-30, Trans_T-30, Long_B-30, and Trans_B-30. At an impact speed of 20 knots, the configurations were Trans_B-20, Long_B-20, Trans_T-20, and Long-T-20. These results suggest that at a collision speed of 30 knots, the optimal configuration is the longitudinal installation of a T profile. Conversely, at an impact speed of 20 knots, the transverse installation of a bar profile yields superior EA performance compared to other models. Additionally, environmental factors, such as wave motion and corrosion, were not considered in the current study but could affect beam performance over time, especially in real-world marine environments. Corrosion, in particular, might degrade material properties and reduce the long-term effectiveness of the impact side beams. Future studies should address these environmental factors, using full-scale models and long-term testing under simulated marine conditions [50].

Drop test experiments for structures have been extensively studied in the literature. Conducted experimental observations of an 8 m/s drop test of a metallic helicopter underfloor structure onto a hard surface, focusing on crashworthiness and structural engineering [51]. Investigated free-fall drop impact tests using various sensors and established a relationship between strain and impact energy correlated with drop height [52]. Performed an experimental and numerical crashworthiness study on a full-scale composite fuselage section, emphasizing aerospace applications [53]. Developed a new drop-weight impact machine for studying fracture processes in structural concrete, focusing on materials science and dynamic testing [54]. These studies provide valuable insights into methodologies, results, and implications of drop test experiments in structural engineering and materials science.

A drop test was conducted involving a pointed impactor with a mass of 37 kg being dropped from a height of 1.5 meters. The materials tested were Alloy 1101 and mahogany wood, both with a thickness of 4 mm. The experiment was performed at a 1:2 scale. The data obtained from this experiment was plotted in a graph (Figure 15). The graph exhibits an irregular line at the bottom, attributable to significant noise. This noise results from utilizing a drop test capacity of up to 5 tons for testing a load of less than 100 kg. This noise affected the clarity of the results due to the mismatch between the test capacity and the actual load applied [55]. The study by Ratner et al. [56] provided insights into improving the precision of dynamic mechanical properties determined from drop tower impact testing. The research suggests using a diaphragm to minimize transient shock loads, specialized impact absorbers to reduce noise, and high-speed cameras to observe displacement accurately. These measures can help mitigate the impact of noise on test results and enhance the reliability of data obtained from drop tests.

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Figure 15. Noise on drop test experiment

The comprehensive results of the drop test experiment, aimed at demonstrating the crashworthiness of wooden and alloy fishing boat materials both with and without side beam impact reinforcement, are depicted in Figure 16. The graph reveals that the larger the cross-sectional area of the stiffeners, the greater the reaction force of the ship's hull structure can withstand. A larger cross-sectional area results in a larger cross-sectional modulus and a more significant moment of inertia of the stiffener. The cross-sectional area of the stiffeners increases, and the ship's hull structure can withstand greater forces. This relationship is attributed to the larger cross-sectional modulus and increased moment of inertia of the stiffener [57, 58]. The order of magnitude of Force for stiffener ID is as follows: Trans_T(40×20), Long_T(20×20), Trans_T(20×20), Trans_FB40, Long_T(20×20), Long_FB40, Alloy without stiffeners (existing), and Mahogany wood 40 mm. The maximum Force is illustrated in Figure 16 and Table 4. This study provides valuable insights into the structural integrity of fishing boats under various conditions.

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Figure 16. Reaction force for all the specimen on drop test experiment

Table 4. The maximum reaction force on drop test experiments

The incorporation of side beam impact significantly enhances the structural robustness of the ship’s hull, surpassing the performance of hulls constructed from wood or alloy without side beam impact. In particular, the maximum impact load that a ship’s hull with side beams can endure reaches 6161 Newtons for a transverse impact side beam design with a T cross section (40×20×5) and 5785 Newtons for a longitudinal impact side beam design with an identical T cross-section. By contrast, the maximum impact load for alloy and mahogany materials is 3306 Newtons and 2957 Newtons, respectively [59]. Consequently, the increase in load capacity that can be withstood is nearly 100%. A comparison of maximum force values for all drop test models is depicted in Figure 13 and Table 4.

A comparative analysis of the drop test results for wooden materials, representative of traditional fishing boat materials, and ship hulls with and without 40 mm flat bar side beam impact reinforcement is illustrated in Figure 17. The experimental results reveal distinct behaviours for each material during the drop test. In the mahogany wood case, there was only one peak in the force-time graph, indicating the absence of a second bounce from the impactor on the test specimen. The distance between the maximum force peaks ranged from 0.05 to 0.144, with the maximum force height in the first and second collisions being 2956.91 N and 1831.18 N, respectively. This suggests that the duration of the first collision and the subsequent second collision assisted by the impactor is 0.094 seconds. The maximum force in the first collision is greater than the second, with a difference of 1125.74 N. For the fishing boat hull without side beam impact reinforcement, the short distance between the peaks suggests that the second bounce transpires within a brief time frame, and the height of the impactor bounce is also short, indicative of a low reaction force of the test material. However, in a collision, the maximum force was 3305.70 N, and no second collision was observed, which explains that the plate was immediately deformed far downwards. There was no bounce from the impactor for the second collision to transpire.

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Figure 17. Temporal discrepancy between the first and second collisions

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Figure 18. Reaction force value based on the direction of side beams impact

In contrast, test specimens with 40 mm flat bar reinforced side beams exhibited the highest reaction force value, with the distance between maximum force peaks being longer, indicative of a more robust structure, which caused the impactor to bounce higher and subsequently a second impact. The maximum force value was 4147.10 N, and the time interval between the first and second collisions was 0.198 seconds, indicating a significant difference compared to the mahogany wood and the alloy ship hull without reinforcement [60]. In sequence, the most significant maximum force is the Alloy hull with flat bar reinforcement of 40 mm, followed by the Alloy hull without reinforcement and the mahogany wood ship material with a thickness of 40 mm.

Figures 18-21 present a comparative study of the orientation of Impact Side Beams in mitigating collision loads in ship hull construction. A marginal variation is noticeable between Trans_T(40×20) and Long_T(40×20) designs, with peak impact load values oscillating between 5785 and 6161 Newtons, as depicted in Figure 18. Conversely, the impact of variations in profile shape with an identical cross-sectional area between the Trans_T(20×20) profiles and Trans_FB(20×20) or Long_T(20×20) is also examined. The performance of Trans_FB(20×20) demonstrates marginally higher reaction force values in comparison to the Trans_T(20×20) or Long_T(20×20) models, as illustrated in Figure 19 and Table 4.

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Figure 19. Reaction force value based on the stiffener shape designs

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Figure 20. Reaction force value based on the difference in sectional area and the shape design of the stiffener

Considering different cross-sectional areas, the Trans_T(40×20) and Trans_T(20×20) models exhibit a discrepancy in the maximum force endured, precisely 5785.00 Newtons and 4049.50 Newtons, respectively. Consequently, the T(40×20) cross-sectional profile yields a marginally superior reaction force compared to T(20×20). Conversely, for an identical cross-sectional area between Trans_FB40 and Trans_T(20×20), where FB 40 denotes reinforcement with flat bars of 40mm height, the maximum stress value that can be sustained is 3907 Newtons. This value surpasses the Trans_T(20×20) and Long_T(20×20) models, which possess the same sectional area. This is illustrated in Figures 19, 20, and 21.

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Figure 21. Reaction force value based on the difference in sectional area, direction installation, and shape design of the stiffener

Significant findings have emerged from the drop test experiment. The drop test, conducted at a free fall speed of up to 5.42 meters per second, could generate tangible differences in maximum force across various ship hull reinforcement models (side beams impact). The optimal sequence for reinforcing the ship's hull, based on the maximum force value that the ship's hull model can withstand, is as follows: Long_T(40×20), Trans_FB40, Trans_T(20×20), Long_T(20×20), Alloy (without stiffness), and Mahogany Wood model with a thickness of 40mm. The experimental tests conducted in this research have yet to yield precise values that align with and can be compared to the deformation and stress magnitudes obtained from computer simulation tests (ANSYS). However, the experimental tests replicated the same phenomena and corroborated the simulation results obtained with ANSYS for several simulation test results.

Installing impact side beams, achieved by adding reinforcing profiles to the ship's hull, can augment the structure's reaction force by nearly 100%. This result was derived from comparing the maximum force without side beam impact (3305.70 N) with the installation of a longitudinal T profile (40×20) with the value of maximum reaction force 6160.65 Newton. A larger cross-sectional area of the profile, for instance, T(40×20) compared to T(20×20), produces a higher force resistance and greater EA. Moreover, transverse installations showed superior performance at lower speeds (under 20 knots) transverse layout and material lightweighting allows enhanced performance with reduced structural mass. This insight supports practical implementation in small fishing vessels requiring both safety and material efficiency.

Generally, the simulation results with ANSYS and drop test experiments for testing the side beam impact design yield several key insights. As the speed increases, so does the deformation, stress, and energy absorption (EA). The simulation test results corroborate this. Computer simulation tests demonstrate that the impact speed significantly influences the amount of deformation, stress, and energy absorption [61]. The energy absorption is the product of the deformation and stress experienced by the ship's hull [62]. The ability of the ship's hull to withstand deformation and stress indicates that the strengthening model with side beam impact can enhance the hull's EA. This is formulated as Eq. (3).

$E A=\int F d x$     (3)

where, F represents the Reaction Force, and dx denotes deformation.

Ship collision simulation tests reveal that the values for deformation and stress are not significantly different for different models with the same cross-sectional area and installation position. This is because the deformation and stress continue to occur within 0.05 seconds at the same speed and have not ceased. The cross-sectional area of the side beam impact influences the magnitude of the Reaction Force, Deformation, and EA stresses, where EA is linear with the cross-sectional area of the side beam impact. This was validated concurrently with computer simulations and drop tests.

The bar profile shape for the simulation test yields a more excellent EA value than the T profile for a collision speed of 20 knots. However, for a collision speed of 30 knots, the T profile exhibits superior performance with a more excellent EA value than the Bar profile. The drop test results with free fall speed for a collision speed of around 10 knots show that the EA value for Flat Bar is better compared to the T profile. Computer simulation tests substantiate this. Theoretically, this can be explained by the fact that the elastic modulus value of the flat bar is higher compared to the T profile, leading to a higher moment of inertia and thus being able to withstand a more significant force compared to a stiffener with a T profile in the direction of impact perpendicular to the construction plane.

The results show distinct EA performance patterns between 20 and 30 knot impacts, with corresponding trends observed in drop test experiments. These patterns validate simulation predictions and reinforce the theoretical correlation between impact velocity and structural energy dissipation. The consistent pattern across both methods highlights the robustness of the model and its suitability for design applications. Taking into account the slight difference in EA value between longitudinal and transverse installation and considering the material requirements and the weight of the construction, the choice of transverse installation is the best with alloy material, which can be saved by more than half, with the side beams impact length for transverse being 0.6 meters, while longitudinal installation is 1.34 meters. Considering that the difference is not significant, Flat Bar, based on computer simulation results, gives the most significant value for EA compared to the T profile at a collision speed of 20 knots. Therefore, the choice of Flat Bar is better, considering easier installation because there is no need to make a T profile to strengthen the hull construction. Drop test experiments support the idea that the transverse flat bar can provide a better reaction force than the T profile.

Further research is needed to explore the influence of impact speed on energy absorption results for the profile shape and installation position of impact side beams. For future research, it is suggested that high-resolution cameras record the deformation during drop tests. This would provide more precise data on deformation at any given time, which could be adjusted to the force data acting on the output load cell. This, in turn, would yield more accurate energy absorption data in the event of a collision between the construction and the impactor. The 1:2 scale used here provides a good preliminary understanding, but scaling up to full-sized models is essential to accurately assess the behavior under real-world impact conditions. Future work should also explore the use of alternative materials, including composites, and examine the influence of environmental factors such as waves and corrosion. These environmental variables can significantly affect the durability and performance of side beams in operational settings, especially in coastal and offshore environments. Overall, the findings of this study underscore the importance of innovative design and material choices in enhancing the crashworthiness of fishing boat hulls, ultimately leading to safer and more efficient maritime operations.