Method for verifying dead load of stern ramp

Abstract

The invention discloses a method for verifying the dead load of a stern ramp. The method comprises the following steps: preparing a first connecting section, a second connecting section and a third connecting section of the stern ramp in a preparation workshop of a ship; sequentially hinging the first connecting section, the second connecting section and the third connecting section in the preparation workshop in the horizontal direction so as to construct a complete stern ramp; fixing the constructed stern ramp on a test platform for simulating a ship stern support structure; according to the designed rated static load of the stern ramp, carrying out graded loading verification on the stern ramp; after the highest-grade loading is completed and the load holding is finished, unloading in a grading manner according to the sequence opposite to the loading grade; and comparing the monitoring data with the design allowable value. According to the invention, the problems that the verification efficiency is low and the requirement of high efficiency of ship building cannot be met due to the fact that the stern ramp is tested after being connected to the ship main body at present can be effectively improved.

Description

Technical Field

[0001] This application relates to the field of shipbuilding technology, and in particular to a method for verifying the static load of a ship's stern ramp. Background Technology

[0002] During shipbuilding, the stern ramp, as a crucial functional structure, directly impacts the ship's operational performance through its installation quality and testing results. Currently, load tests on stern ramps must be conducted in the dry dock after installation and only after all hull structure welding is completed.

[0003] However, if the load test of the stern ramp fails after the entire hull structure has been welded, a large amount of rework is required, which is detrimental to the normal production of the ship. As a result, the efficiency of testing stern ramps in the dry dock is currently relatively low, making it difficult to meet the high-efficiency requirements of shipbuilding. Summary of the Invention

[0004] The purpose of this invention is to provide a method for verifying the static load of a ship's stern ramp, which can solve the above-mentioned problems existing in the prior art.

[0005] To achieve the above objectives, this application adopts the following technical solution: A method for verifying the static load of a ship's stern ramp is provided, comprising: Step S10: The first connecting section, the second connecting section, and the third connecting section of the stern ramp are prepared in the ship's manufacturing workshop. Step S20: In the preparation workshop, the first connecting section, the second connecting section and the third connecting section are sequentially hinged in the horizontal direction to construct a complete stern ramp. Step S30: Fix the constructed stern ramp onto the test platform simulating the stern support structure of a ship, so that the two ends of the stern ramp correspond to the support points of the test platform, the stern ramp is kept horizontal, and the second connecting section is suspended. Step S40: Based on the design rated static load of the stern ramp, set at least 3 loading levels, including 50%, 80%, and 100% of the rated static load. If the design requirements include overload verification, add a loading level of 120% of the rated static load. At the same time, determine the loading point of each loading level. The loading point shall at least cover the middle stress area of ​​the stern ramp and the area within 200mm on both sides of the hinge of each connecting section. Step S50: Use a hydraulic loading device to apply graded loading to each loading point. After each loading is completed, maintain the load for 15-30 minutes. During this period, use a displacement sensor to monitor the vertical deformation of each loading point and hinge in real time, and use a stress sensor to monitor the stress values ​​of each connection weld and key stress-bearing parts, and record the monitoring data. Step S60: After completing the highest level of loading and holding, unload in stages according to the reverse order of loading level. After unloading, let it stand for 24 hours and measure the residual deformation of the stern ramp again. Step S70: Compare the monitoring data with the design allowable value: If the maximum vertical deformation under each loading level does not exceed the design allowable deformation, the static load verification of the stern ramp is deemed qualified; otherwise, the verification is deemed unqualified, and structural review and adjustment are carried out for the out-of-tolerance parts, and then steps S30-S60 are executed again.

[0006] Preferably, in step S20, the hinges between the first connecting segment and the second connecting segment, and between the second connecting segment and the third connecting segment, are all connected by pins. The pins are made of 40Cr alloy structural steel, and the clearance between the pins and the hinge holes of each connecting segment is controlled at 0.05-0.1mm. A lubrication structure is also provided at the hinge, the lubrication structure including an annular lubricating oil channel opened in the inner wall of the hinge hole and an oil injection nozzle communicating with the lubricating oil channel.

[0007] Preferably, in step S30, the support structure of the test platform includes at least a plurality of adjustable height support cylinders, and the top of each support cylinder is provided with a support block adapted to the hinge joint of the stern ramp.

[0008] Preferably, in step S40, the number of loading points satisfies: At least two loading points should be set in the mid-stress zone, and these two loading points should be symmetrically distributed along the length of the stern ramp; and One loading point is set on each side of the hinge of each connecting segment, and the distance between the loading point and the hinge is 100mm and 200mm respectively; When a loading level of 120% of the rated static load is added, a loading level of 90% of the rated static load is added between the 80% and 100% rated static load loading levels.

[0009] Preferably, in step S50, the load holding time is adjusted according to the loading level, including: When the load level is 50% or 80% of the rated static load, the holding time is 15 minutes; when the load level is 100% or 120% of the rated static load, the holding time is 30 minutes. The displacement sensor has a measurement accuracy of not less than 0.01 mm, and the stress sensor has a measurement range of 0-300 MPa and a measurement accuracy of ±0.5% FS; and The monitoring data is recorded using an automatic acquisition system with a data acquisition frequency of 1 time / min. The acquisition system has real-time data storage and abnormal alarm functions. When the monitored stress value exceeds 1.05 times the design allowable stress, an alarm signal is automatically issued.

[0010] Preferably, in step S60, during the graded unloading, the load amount of each unloading stage is the same as the load amount of the corresponding loading level, and the unloading stability time is maintained for 5-8 minutes after each unloading stage. In the measurement of residual deformation, a laser rangefinder was used to measure six points: the end, middle, and all hinges of the stern ramp. The maximum deformation value at each point was taken as the final residual deformation. During the 24-hour resting period, the temperature of the test environment was controlled at 20±5℃, the relative humidity was controlled at 40%-60%, and violent vibration sources were avoided around the test platform.

[0011] Preferably, in step S70, the allowable deformation is 1 / 1000 of the length of the stern ramp. If the verification is deemed unqualified, the structural review includes using ultrasonic testing equipment to perform non-destructive testing on the welds in the out-of-tolerance areas to check for welding defects.

[0012] Preferably, when welding defects are found, a structural adjustment plan is implemented, including: If the area exceeding the tolerance is the weld area, increase the weld height by 2-3mm; and If the part exceeding the tolerance is the main body of the connecting section, add a reinforcing rib plate with a thickness of 8-12mm in the corresponding area; The reinforcing rib plate and the connecting section are connected by double-sided fillet welds, and the weld height is not less than 8mm.

[0013] Preferably, it also includes step S101: After step S10 is completed, the surface flatness and weld appearance of each connection section are inspected. The surface flatness error shall not exceed 3mm / m, the weld appearance shall be free of defects such as cracks, porosity, and slag inclusions, and the weld reinforcement shall be controlled within 2-4mm. If the inspection fails, the defective parts shall be repaired before proceeding to step S20.

[0014] Preferably, it also includes a stern verification step, including: An equivalent load is applied at the stern ramp installation location on the stern section of the ship. The equivalent load includes the verification load of the stern ramp and the total weight of the stern ramp.

[0015] The beneficial effects of this application are as follows: 1. By completing the entire process of plank preparation, assembly, and testing in the workshop in advance, parallel construction is achieved, thus shortening the overall construction cycle. Through the design of gradient loading, load observation, anomaly alarms, and reverse unloading, potential risks can be exposed in advance, preventing irreversible damage during testing and use. It can avoid structural fracture caused by a single full-load impact and capture the slow plastic deformation of materials under continuous high loads, thus eliminating the risk of long-term load-bearing hidden damage in advance.

[0016] 2. Through additional stern verification steps, the local strength of the stern installation location is specifically tested using equivalent load-bearing to ensure that the interface load-bearing capacity between the gangplank and the stern meets the standards, thus preventing the gangplank from falling due to insufficient stern support during actual use.

[0017] 3. By moving the static load test of the stern ramp from the dry dock to the ground and using simulated support points, the support status can be adjusted at any time, reducing the amount of work and construction time in the dry dock. Compared with conducting the stern ramp load test in the dry dock, this can significantly shorten the construction cycle, thereby shortening the undocking cycle. Attached Figure Description

[0018] The present application will now be described in further detail with reference to the accompanying drawings and embodiments.

[0019] Figure 1 This is a flowchart illustrating the method for verifying the static load of the stern ramp according to an embodiment of this application. Figure 2 This is a schematic diagram of the first connecting section, the second connecting section, and the third connecting section of the verification method for static load of the stern ramp described in this application embodiment; Figure 3 This is a schematic diagram of the structure after the first connecting section, the second connecting section, and the third connecting section are connected in sequence in the verification method for static load of the stern ramp described in this application embodiment; Figure 4 This is a schematic diagram of the process of hoisting the stern ramp, which is part of the verification method for the static load of the stern ramp according to an embodiment of this application. Figure 5 This is a schematic diagram of the connection structure between the stern ramp and the supporting hydraulic cylinder in the verification method for static load of the stern ramp according to an embodiment of this application. Figure 6 This is a schematic diagram of the stern ramp installed on a ship, illustrating the verification method for static load of the stern ramp described in this application.

[0020] In the picture: 11. First connecting section; 12. Second connecting section; 13. Third connecting section; 15. Support cylinder; 100. Stern ramp. Detailed Implementation

[0021] To make the technical problems solved by this application, the technical solutions adopted, and the technical effects achieved clearer, the technical solutions of the embodiments of this application are further described in detail below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0022] In the description of this application, unless otherwise expressly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0023] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0024] like Figures 1 to 6 As shown, this disclosure provides a method for verifying the static load of a stern ramp, which can be used to improve the current method of testing the stern ramp 100 after it is connected to the hull of the ship, resulting in low verification efficiency and insufficient to meet the needs of high-efficiency shipbuilding.

[0025] Specifically, the method for verifying the static load of the stern ramp disclosed herein may include the following steps.

[0026] First, step S10 is executed, in which the first connecting section 11, the second connecting section 12, and the third connecting section 13 of the stern ramp 100 are prepared in the ship's fabrication workshop. By preparing the first connecting section 11, the second connecting section 12, and the third connecting section 13 in advance in the workshop, the schedule conflict between the preparation of the stern ramp 100 and the construction of the main body of the ship can be avoided, and the two can be carried out in parallel, significantly reducing the overall ship construction cycle.

[0027] After step S10, the surface flatness and weld appearance of the first connecting section 11, the second connecting section 12, and the third connecting section 13 are inspected. The inspection includes at least ensuring that the surface flatness error does not exceed 3mm / m, that the weld appearance is free of defects such as cracks, porosity, and slag inclusions, and that the weld reinforcement is controlled within 2-4mm. If the inspection fails, the defective areas are repaired before proceeding to step S20. It is understandable that by inspecting the first connecting section 11, the second connecting section 12, and the third connecting section 13, uneven surface conditions of the connecting sections can effectively prevent uneven stress distribution during subsequent connection with the ship's hull, and prevent misjudgment of the stern ramp 100's load-bearing capacity due to basic assembly issues during static load testing.

[0028] In step S20, the first connecting segment 11, the second connecting segment 12, and the third connecting segment 13 are sequentially hinged horizontally in the preparation workshop to construct a complete stern ramp 100. The workshop can use tooling fixtures to fix the horizontal reference, ensuring that the hinge axes of the first connecting segment 11, the second connecting segment 12, and the third connecting segment 13 are coaxial. This avoids misalignment of the hinges due to limited space or the ship's posture on site, thus ensuring accurate movement trajectories of each segment when the stern ramp 100 is unfolded or folded, and reducing the risk of jamming.

[0029] The first connecting section 11, the second connecting section 12, and the third connecting section 13 are hinged to each other, allowing them to be folded together. This facilitates the stern ramp 100 to be folded and stored on the ship, improving space utilization.

[0030] It should be noted that the hinges between the first connecting section 11 and the second connecting section 12, and between the second connecting section 12 and the third connecting section 13, are all connected by pins. The pins are made of 40Cr alloy structural steel, and the clearance between the pins and the hinge holes of each connecting section is controlled within 0.05-0.1mm. A lubrication structure is also provided at the hinge, which includes an annular lubricating oil channel formed on the inner wall of the hinge hole and an oil injection port connected to the lubricating oil channel.

[0031] Understandably, 40Cr alloy structural steel was chosen as the material for the pin. This material possesses high strength, good toughness, and wear resistance, capable of withstanding the static load transmission when the stern ramp is fully extended (100%), while also resisting fatigue wear caused by long-term folding or unfolding, preventing pin breakage or deformation. The annular lubrication channel on the inner wall of the hinge hole allows the injected lubricating oil to evenly cover the contact surface between the pin and the hole wall, avoiding insufficient local lubrication caused by traditional "single-point oiling". At the same time, a certain amount of lubricating oil can be stored in the oil channel, extending the lubrication cycle and reducing the need for frequent oiling.

[0032] In step S30, the constructed stern ramp 100 is fixed on the test platform simulating the stern support structure of a ship, so that the two ends of the stern ramp 100 correspond to the support points of the test platform, the stern ramp 100 is kept horizontal, and the second connecting section 12 is suspended.

[0033] Once the stern ramp 100 is manufactured in the preparation workshop, it can be transported using a mobile trolley. When the stern ramp 100 is moved to the vicinity of the test platform, it can be lifted and transferred to the test platform using a hoisting mechanism. This allows for short-distance movement of the stern ramp 100 within the workshop without relying on large lifting equipment, avoiding structural collisions caused by frequent hoisting. Simultaneously, the trolley provides stable support to the bottom of the stern ramp 100, preventing it from loosening in its folded state or deforming at the hinges during transport. When the stern ramp 100 needs to be transferred to the test platform, the hoisting mechanism can lift it smoothly and precisely, especially protecting the pins and lubrication structures at the hinges, preventing damage to the hinge holes and lubrication channels during transport, and ensuring the structural accuracy of the previous assembly is not compromised.

[0034] Furthermore, the support structure of the test platform includes at least a plurality of height-adjustable support cylinders 15, each support cylinder 15 having a support block at its top that fits into the hinge point of the stern ramp 100. The height and levelness of the stern ramp 100 can be adjusted in real time using the height-adjustable support cylinders 15. The support block located between the top of the support cylinder 15 and the stern ramp 100 improves the stability between the support cylinder 15 and the stern ramp 100.

[0035] Step S40: Based on the design rated static load of the stern ramp 100, set at least three loading levels, including 50%, 80%, and 100% of the rated static load. If the design requirements include overload verification, add a loading level of 120% of the rated static load. Simultaneously determine the loading points for each loading level, ensuring that the loading points at least cover the central stress area of ​​the stern ramp 100 and the area within 200mm on both sides of the hinge joints of each connecting section.

[0036] Specifically, starting with a low-level loading of 50% of the rated static load, the structural stability of the stern ramp 100 under low load can be verified first. This includes checking for minor deformations and abnormal noises at the hinges. If problems are found, such as excessive deformation due to localized stress concentration, loading can be stopped immediately and corrective measures taken. This avoids irreversible damage to the stern ramp 100 caused by directly loading to 100% or 120%, significantly reducing testing costs and rework risks. Simultaneously, gradient loading allows for monitoring of deformation and stress values ​​after each loading level, progressively plotting the load-deformation curve of the stern ramp 100. This clearly captures the critical point between elastic and plastic deformation, such as whether minute plastic deformation occurs at 80%-90% load. Compared to testing at full load, this provides a more comprehensive understanding of the actual load-bearing capacity of the stern ramp 100, providing data support for subsequent safe use.

[0037] Understandably, once the stern ramp 100 is installed on the support platform, the strength of the stern ramp 100 can be tested by setting a load on it.

[0038] Specifically, during the actual measurement process, it is permissible to apply a load to the stern ramp 100 according to the designed rated static load.

[0039] It should be noted that the number of loading points must meet the following conditions.

[0040] First, at least two loading points are set in the mid-stress area, and these two loading points are symmetrically distributed along the 100mm length of the stern ramp. One loading point is set on each side of the hinge joint of each connecting section, with the loading points 100mm and 200mm away from the hinge joint, respectively. When an additional 120% rated static load loading level is added, a 90% rated static load loading level is added between the 80% and 100% rated static load loading levels.

[0041] Understandably, when 120% overload verification is required, a 90% load level is added between 80% and 100% to further refine the test gradient in the high-load range. This avoids missing critical points due to the large load span from 80% to 100%. For example, a potential hazard appeared on the stern ramp 100 at 85% load, but it went undetected because there was no intermediate level, making the overload verification more accurate and reliable.

[0042] Meanwhile, since the second connecting section 12 is suspended, this area is the region of maximum bending moment when the stern ramp 100 is subjected to static load. When cargo passes through, the middle section is subjected to downward pressure, while the two ends are subjected to supporting forces, making the middle section prone to bending stress. Setting a loading point in the middle stress area can directly verify the strength of the core load-bearing part of the stern ramp 100, avoiding breakage due to insufficient strength in the middle section during actual use.

[0043] Since the hinge is a structurally weak point of the ship's stern ramp 100, it is subjected to shear forces when folded or unfolded. Under static load, local stress concentration will occur on both sides of the hinge due to the force transmission between the connecting sections. By covering the load point within 200mm on both sides of the hinge, the load-bearing capacity of this risk area can be specifically verified to prevent problems such as weld cracking and connecting section deformation near the hinge in actual use.

[0044] In step S50, a hydraulic loading device is used to apply graded loading to each loading point. After each loading is completed, the load is held for 15-30 minutes. During this period, the vertical deformation of each loading point and hinge is monitored in real time by a displacement sensor, and the stress value of each connection weld and key stress-bearing part is monitored by a stress sensor, and the monitoring data is recorded.

[0045] Specifically, the load duration is adjusted according to the load level, including the following conditions.

[0046] First, when the load level is 50% or 80% of the rated static load, the holding time is 15 minutes. When the load level is 100% or 120% of the rated static load, the holding time is 30 minutes. The displacement sensor has a measurement accuracy of no less than 0.01 mm, and the stress sensor has a measurement range of 0-300 MPa and a measurement accuracy of ±0.5%FS.

[0047] Understandably, compared to traditional heavy-load loading, hydraulic loading can achieve a stable force output through pressure regulation, avoiding sudden increases in local stress caused by the impact of the load being dropped. At the same time, it can precisely match the design load at each loading point, ensuring that the loading force value at each stage is without deviation, laying the foundation for the accuracy of subsequent monitoring data.

[0048] Holding the load for 15 minutes under low load allows for rapid verification of the instantaneous stability of the stern ramp 100 under normal loads, such as whether instantaneous elastic deformation occurs or whether there is slight displacement at the hinge. Holding the load for 30 minutes under high load allows for thorough observation of the material's creep effect, i.e., whether the stern ramp 100 exhibits slow plastic deformation under sustained high loads. This includes detecting minor cracks in the weld seams of the connecting sections and slight extrusion deformation between the pin and the hole wall, thus preventing latent damage caused by prolonged load-bearing in actual use and significantly improving the long-term safety of the stern ramp 100.

[0049] It is important to note that the monitoring data is recorded using an automatic data acquisition system at a frequency of once per minute. This system features real-time data storage and anomaly alarm functions; when the detected stress value exceeds 1.05 times the design allowable stress, an alarm signal is automatically issued. The acquisition frequency of once per minute ensures complete recording of stress or displacement trends during each load period. This includes monitoring for patterns such as stress initially rising and then stabilizing under high loads, or a continuous increase, avoiding data gaps caused by manual acquisition. Furthermore, it eliminates errors from manual readings, ensuring data accuracy and traceability, and providing a reliable basis for subsequent qualification assessment of the stern ramp.

[0050] Step S60: After completing the highest level of loading and holding the load, unload in stages in the reverse order of loading level. After unloading, let it stand for 24 hours and measure the residual deformation of the stern ramp 100 again.

[0051] It is important to note that during staged unloading, the load amount for each stage of unloading is the same as the load amount for the corresponding loading level, and the unloading stability time is maintained for 5-8 minutes after each stage of unloading. Specifically, when measuring residual deformation, a laser rangefinder is used to measure six points at the end, middle, and hinge points of the stern ramp 100. The maximum value of the deformation at each measuring point is taken as the final residual deformation.

[0052] Understandably, during the progressive loading process, stress accumulates from top to bottom at each connecting section, weld, and hinge of the stern ramp 100. Unloading in reverse order of 100%, 80%, and 50% allows the stress to be released gradually from high to low, avoiding the shock of a sudden stress drop caused by a one-time unloading. For example, if unloaded directly from 100% to 0%, the stern ramp 100 may experience rebound vibration due to excessively rapid elastic recovery, causing the hinge pin to collide with the hole wall, the weld to experience instantaneous tensile stress, and even micro-cracks.

[0053] Meanwhile, during the 24-hour settling period, the temperature of the testing environment was controlled at 20±5℃, and the relative humidity was controlled at 40%-60%, while avoiding sources of severe vibration around the testing platform. Since the stern ramp 100 is primarily a metal structure, temperature changes will cause thermal expansion and contraction. If the temperature fluctuation is too large, the measured deformation may include temperature deformation rather than the actual residual deformation. Maintaining relative humidity at 40%-60% avoids slight corrosion of the metal surface caused by high humidity, while also preventing dust adhesion caused by low humidity, ensuring measurement accuracy.

[0054] Step S70: Compare the monitoring data with the design allowable values.

[0055] Specifically, if the maximum vertical deformation at each loading level does not exceed the design allowable deformation, it is determined that the static load verification of the stern ramp 100 is qualified. Otherwise, it is determined that the verification is unqualified, and the structure is rechecked and adjusted for the out-of-tolerance parts, and then steps S30 - S60 are executed again.

[0056] Specifically, in step S70, the design allowable deformation is 1 / 1000 of the length of the stern ramp 100. If it is determined that the verification is unqualified, the structure recheck includes using ultrasonic flaw detection equipment to conduct non-destructive testing on the welds of the out-of-tolerance parts to check for welding defects.

[0057] It can be understood that the determination needs to cover the monitoring data at each loading level, rather than just looking at the highest level. For example, if the deformation at the 100% level is qualified, but local deformation out-of-tolerance has occurred at the 80% level, it indicates that there are already potential hazards in the stern ramp 100 under normal loads. It can be promptly determined as unqualified to avoid the risk of "failure under normal loads" during actual use and ensure that the determination result covers all working conditions.

[0058] Furthermore, when there are welding defects, a structure adjustment plan is executed.

[0059] Specifically, the structure adjustment plan includes: If the out-of-tolerance part is the weld area, increase the weld height by 2 - 3 mm; and If the out-of-tolerance part is the connecting section body, add stiffening plates with a thickness of 8 - 12 mm in the corresponding area; Among them, the stiffening plates and the connecting section are connected by double-sided fillet welds, and the weld height is not less than 8 mm.

[0060] It can be understood that if the out-of-tolerance is only local welds, only the weld height needs to be increased by 2 - 3 mm, and there is no need to disassemble the three connecting sections or replace the materials. If it is a local problem with the connecting section, only small stiffening plates need to be added instead of replacing the entire connecting section. Compared with the repair method of overall scrapping and reworking, it can effectively save material and labor costs. Especially for the stern ramp 100 with the hinge and lubrication structure already assembled, local rectification can retain the previous investment to the greatest extent and significantly improve the economy of shipbuilding.

[0061] In summary, based on the above verification method for the static load of the stern ramp, the strength of the stern ramp 100 can be effectively verified.

[0062] In addition, it also includes a stern verification step, which includes loading equivalent loads at the installation position of the stern ramp 100 on the stern part. The equivalent load includes the sum of the verification load of the stern ramp 100 and the total weight of the stern ramp 100. By verifying the load on the stern, it can be ensured that the stern is in a compliant state after connecting the stern ramp 100.

[0063] Understandably, the stern verification process verifies the strength of the connections at the stern ramp 100. This includes verifying the weld strength of the stern mounting supports, the connection rigidity between the deck and the supports, and the resistance to compression at the hinge points between the supports and the stern ramp 100. This helps prevent the stern ramp 100 from breaking during use due to insufficient local strength at the installation location, thus avoiding the risk of the stern ramp 100 falling.

[0064] In summary, this disclosure provides a method for verifying the static load of a ship's stern ramp. By completing the entire process of ramp preparation, assembly, and testing in the workshop beforehand, parallel construction is achieved, thus shortening the overall construction cycle. Through gradient loading, load observation, anomaly alarms, and reverse unloading, potential risks can be exposed early, preventing irreversible damage during testing and use. This avoids structural fracture caused by a single full-load impact and captures the slow plastic deformation of materials under sustained high loads, eliminating the risk of long-term hidden damage. The additional stern verification step, through equivalent load distribution, specifically tests the local strength of the stern installation location to ensure the interface load-bearing capacity between the ramp and the stern meets standards. This prevents the ramp from falling due to insufficient stern support during actual use.

[0065] By moving the static load test of the stern ramp from the dry dock to the ground and using simulated support points, the support status can be adjusted in real time, reducing the amount of work and construction time in the dry dock. Compared with conducting the stern ramp load test in the dry dock, this can significantly shorten the construction cycle, thereby shortening the undocking cycle.

[0066] In the description herein, it should be understood that the terms "upper," "lower," "left," "right," and other orientations or positional relationships are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used merely for descriptive distinction and have no special meaning.

[0067] In the description of this specification, references to terms such as "an embodiment," "example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example.

[0068] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style of the specification is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0069] The technical principles of this application have been described above with reference to specific embodiments. These descriptions are merely for explaining the principles of this application and should not be construed as limiting the scope of protection of this application in any way. Based on this explanation, those skilled in the art can readily conceive of other specific embodiments of this application without inventive effort, and these embodiments will all fall within the scope of protection of this application.

Claims

1. A method for verifying the static load of a ship's stern ramp, characterized in that, include: Step S10: The first connecting section, the second connecting section, and the third connecting section of the stern ramp are prepared in the ship's manufacturing workshop. Step S20: In the preparation workshop, the first connecting section, the second connecting section and the third connecting section are sequentially hinged in the horizontal direction to construct a complete stern ramp. Step S30: Fix the constructed stern ramp onto the test platform simulating the stern support structure of a ship, so that the two ends of the stern ramp correspond to the support points of the test platform, the stern ramp is kept horizontal, and the second connecting section is suspended. Step S40: Based on the design rated static load of the stern ramp, set at least 3 loading levels, including 50%, 80%, and 100% of the rated static load. If the design requirements include overload verification, add a loading level of 120% of the rated static load. At the same time, determine the loading point of each loading level. The loading point shall at least cover the middle stress area of ​​the stern ramp and the area within 200mm on both sides of the hinge of each connecting section. Step S50: Use a hydraulic loading device to apply graded loading to each loading point. After each loading is completed, maintain the load for 15-30 minutes. During this period, use a displacement sensor to monitor the vertical deformation of each loading point and hinge in real time, and use a stress sensor to monitor the stress values ​​of each connection weld and key stress-bearing parts, and record the monitoring data. Step S60: After completing the highest level of loading and holding, unload in stages according to the reverse order of loading level. After unloading, let it stand for 24 hours and measure the residual deformation of the stern ramp again. Step S70: Compare the monitoring data with the design allowable value: If the maximum vertical deformation under each loading level does not exceed the design allowable deformation, the static load verification of the stern ramp is deemed qualified; otherwise, the verification is deemed unqualified, and structural review and adjustment are carried out for the out-of-tolerance parts, and then steps S30-S60 are executed again.

2. The method for verifying the static load of the stern ramp according to claim 1, characterized in that, In step S20, the hinges between the first connecting segment and the second connecting segment, and between the second connecting segment and the third connecting segment, are all connected by pins. The pins are made of 40Cr alloy structural steel, and the clearance between the pins and the hinge holes of each connecting segment is controlled at 0.05-0.1mm. A lubrication structure is also provided at the hinge, the lubrication structure including an annular lubricating oil channel opened in the inner wall of the hinge hole and an oil injection nozzle communicating with the lubricating oil channel.

3. The method for verifying the static load of the stern ramp according to claim 1, characterized in that, In step S30, the support structure of the test platform includes at least a plurality of adjustable height support cylinders, and the top of each support cylinder is provided with a support block adapted to the hinge joint of the stern ramp.

4. The method for verifying the static load of the stern ramp according to claim 1, characterized in that, In step S40, the number of loading points satisfies: At least two loading points should be set in the mid-stress zone, and these two loading points should be symmetrically distributed along the length of the stern ramp; and One loading point is set on each side of the hinge of each connecting segment, and the distance between the loading point and the hinge is 100mm and 200mm respectively; When a loading level of 120% of the rated static load is added, a loading level of 90% of the rated static load is added between the 80% and 100% rated static load loading levels.

5. The method for verifying the static load of the stern ramp according to claim 1, characterized in that, In step S50, the load holding time is adjusted according to the loading level, including: When the load level is 50% or 80% of the rated static load, the holding time is 15 minutes; when the load level is 100% or 120% of the rated static load, the holding time is 30 minutes. The displacement sensor has a measurement accuracy of not less than 0.01 mm, and the stress sensor has a measurement range of 0-300 MPa and a measurement accuracy of ±0.5% FS; and The monitoring data is recorded using an automatic acquisition system with a data acquisition frequency of 1 time / min. The acquisition system has real-time data storage and abnormal alarm functions. When the monitored stress value exceeds 1.05 times the design allowable stress, an alarm signal is automatically issued.

6. The method for verifying the static load of the stern ramp according to claim 1, characterized in that, In step S60, during the graded unloading, the load amount of each unloading stage is the same as the load amount of the corresponding loading level, and the unloading stability time is maintained for 5-8 minutes after each unloading stage. In the measurement of residual deformation, a laser rangefinder was used to measure six points: the end, middle, and all hinges of the stern ramp. The maximum deformation value at each point was taken as the final residual deformation. During the 24-hour resting period, the temperature of the test environment was controlled at 20±5℃, the relative humidity was controlled at 40%-60%, and violent vibration sources were avoided around the test platform.

7. The method for verifying the static load of the stern ramp according to claim 1, characterized in that, In step S70, the allowable deformation is 1 / 1000 of the length of the stern ramp. If the verification is deemed unqualified, the structural review includes using ultrasonic testing equipment to perform non-destructive testing on the welds in the out-of-tolerance areas to check for welding defects.

8. The method for verifying the static load of the stern ramp according to claim 7, characterized in that, When welding defects are found, a structural adjustment plan is implemented, including: If the area exceeding the tolerance is the weld area, increase the weld height by 2-3mm; and If the part exceeding the tolerance is the main body of the connecting section, add a reinforcing rib plate with a thickness of 8-12mm in the corresponding area; The reinforcing rib plate and the connecting section are connected by double-sided fillet welds, and the weld height is not less than 8mm.

9. The method for verifying the static load of the stern ramp according to claim 1, characterized in that, It also includes step S101: After step S10 is completed, the surface flatness and weld appearance of each connection section are inspected. The surface flatness error shall not exceed 3mm / m, the weld appearance shall be free of defects such as cracks, porosity, and slag inclusions, and the weld reinforcement shall be controlled within 2-4mm. If the inspection fails, the defective parts shall be repaired before proceeding to step S20.

10. The method for verifying the static load of the stern ramp according to claim 1, characterized in that, It also includes stern verification steps, including: An equivalent load is applied at the stern ramp installation location on the stern section of the ship. The equivalent load includes the verification load of the stern ramp and the total weight of the stern ramp.

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