Nonlinear Finite Element Method Analysis Research Articles

Influence of overlay strength degradation on bond stresses of bridge deck system

This research paper intends to numerically investigate the impact of selected factors on the strength of the concrete overlay-bridge deck bond, directly and indirectly, using the nonlinear finite element analysis (NLFEA) method. Besides, the research introduces the guidelines necessary to attain adequate bond strength to eliminate the possibility of concrete detachment under the effect of different developed stresses. The NLFEA has been utilized in predicting and correlating the live applied loads and the induced shrinkage stresses at the interfacial region between the concrete overlay and the bridge deck. The developed stresses were related to the overlay's direct tensile bond strength. A total of 336 NLFEA models of overlay-bridge deck slab segments were designed and examined after being properly validated. The parameters of the study were as follows: the overlay degradation level (0 %, 19 %, 36 %, 51 %, 64 %, and 75 %); the ratio of the overlay's relative thickness-to-the bridge deck slab (toverlay/tslab); in addition to the age of the shrinkage induced stresses (early age (3 and 7 days) and moderate age (14 and 28 days)). The NLFEA live load and shrinkage stress values were validated using experimental results from the literature with difference percentages of less than 5 %. The numerical study results recommended that the thickness of the concrete's overlay should be within certain overlay thickness limits to be capable of handling the lower and higher stresses at the service and overloading conditions. The proposed guidelines enable the avoidance of unfavorable detachment between the interface parts under the effect of AASHTO HS-20 truck cyclic and impact loadings, as well as shrinkage loading.

Effects of Mosquito-Imitated Microneedle’s Reciprocating Rotations on Puncture Resistance Forces—Evaluations by Puncturing Experiments and Nonlinear FEM Analyses—

Development of a low-invasive microneedle is currently desired in the medical field to mitigate the patients’ stress and pain. We have paid attention to mosquitoes that puncture the skin without giving humans no feelings of pain. We have observed mosquitoes and found that when their proboscis punctures human skin, they make the following three behaviors: apply tension to human skin; rotate their proboscis; vibrate their proboscis. In our previous studies, we developed a bundled set of three microneedle imitating the mosquito’s proboscis and experimentally proved the usefulness of their alternate vibrations, which is one of the mosquito’s puncturing behaviors. However, the setting of three needles with proper clearances from each other was difficult, making their driving system too complex to practically use it. Therefore, we have developed a simplified microneedle by reducing the number of needles from three to two or one. This paper has focused on the effects of the rotations of a single needle. Using our developed microneedle with a diameter of 90 µm and the thinnest commercial microneedle with a diameter of 180 µm, we evaluated the effect of reciprocating rotation, one of the mosquitoes’ puncturing behaviors, by puncture experiments using artificial skin and nonlinear finite element method (FEM) analysis. As a result, it was found that the reciprocating rotation suppresses the puncture resistance force and the skin deflection.

Comparison of the Mechanical Properties and Approach to Numerical Modeling of Fiber-reinforced Composite, High-Strength Steel and Aluminum

The performance of carbon fiber reinforced polymer (CFRP) composite materials under quasi-static and high strain rate loading can be predicted with a high level of accuracy using the non-linear finite element analysis (FEA) method. Experimental validation tests under uniaxial tensile loading have shown a good correlation with FEA predictions for thermoset polymer composites, using commercially available epoxy resin MTM710 with carbon fiber reinforcement and for comparative tests on DP600 steel and aluminum alloys (AC170 and 5754 series). The physical and numerical results comparison of composite, aluminum, and high-strength steel indicates that the composite may be used as an alternative to aluminum and high-strength steel since the composite was shown to have almost the same strength as steel and higher strength than aluminum with the advantage of being lightweight and possessing similar mechanical behavior under quasi-static conditions. The results demonstrated that the strain rate range used did not significantly affect the strength of the composite materials. The selection of materials can be optimized reliably by FEA based on mechanical properties, cost, and weight. This will significantly reduce the new product introduction timescale, which is essential for the wider use of polymer composites for structural applications, especially in the automotive industry.

NLFEA of the Behavior of Polypropylene-Fiber-Reinforced Concrete Slabs with Square Opening

The bending behavior of one-war reinforced concrete (RC) slabs with polypropylene fibers (PF) was examined in this study under the effect of different opening ratios using the nonlinear finite element analysis (NLFEA) method. The investigated parameters include the effect of different square opening ratios between 0 and 24% and PF volume percentages between 0 and 1% with 0.1% increments. The objectives of this study were fulfilled using 88 NLFEA models with different combinations of the studied parameters, including 11 control slabs without openings. The slab’s behavior was studied focusing on different structural performance characteristics, such as ductility, using energy-based and deflection-based approaches, stiffness (initial and yielding), cracking, and ultimate load strength. In addition, other structural performance parameters were considered, such as the crack opening, failure modes, and strain values, which were recorded for all specimens during the loading history. Moreover, the load-carrying capacity of the slabs was compared, looking at the NLFEA method’s results and the theoretical prediction results based on the sectional analysis method. However, it was observed that the inclusion of PFs of different percentages has a superior effect on the behavior of RC slabs with small openings (less than 2% opening ratio) compared to the acceptable improvements obtained for sabs with larger opening sizes. Consequently, PF could be utilized as a replacement for conventional steel rebars for RC slabs with small openings. In addition, increasing the PF percentage increases the resulting crack-opening value at failure due to the provided stabilization effect, in addition to increasing the system’s ability to sustain loads.

Evaluation of the Applicability of Digital Photogrammetry-Based Initial Imperfections on NLFEM Ultimate Strength Analysis of Ship- Type Stiffened Plates

In this study, the effects of initial imperfections on the ultimate strength values of ship-type stiffened plate structures are discussed and analysed from the point of view of how the initial imperfection forms are obtained. Ship stiffened panels are subjected to complex loading conditions during their operational lifespan. Accurate prediction of their strength and failure modes necessitates a thorough understanding of the effects of various imperfections on their behavior. Two primary sources of initial imperfections are considered: the buckling mode shapes resulting from linear eigenvalue buckling analysis and measurements based on digital photogrammetry. Buckling mode shapes, arising from the manufacturing process are extracted using linear static structural analysis. Digital photogrammetry is employed to capture and quantify imperfections by analysing high-resolution images of the physical structure. Numerical investigation is conducted by incorporating these two types of initial imperfections into non-linear finite element method (NLFEM) calculations. The buckling mode imperfections are applied as geometric perturbations, while the photogrammetry-based imperfections are incorporated as statistically representative deviations from the ideal geometry. Stiffened panel's structural response is analysed under longitudinal uniaxial compression. A new NLFEM project schematic has been utilized instead of the procedure outlined in the technical circular S.P 01/19 by Türk Loydu, which has been discontinued after ANSYS® Workbench™V.2019R2. This is proven by two validation case studies in ANSYS® Workbench™2022R2 version for considering buckling mode initial imperfections. A case study is then conducted using a 3D model of a stiffened plate panel, which is fabricated in a shipyard located in Trabzon, created by Photomodeler V. 2023.3.0.238 employing the digital photogrammetry method.NLFEM analysis is carried out for both initially deflected model after eigenvalue buckling analysis and naturally deflected model after welding operations. The comparative ultimate strength results are quite consistent, and this shows that the digital photogrammetric modelling method can be used in the analysis of ship structural elements.

Numerical investigation of elastic-plastic buckling performance of circular arched cellular steel beam using nonlinear finite element analysis method

This study presents a numerical investigation of the in-plane elastic-plastic performance, post-buckling mode, and arched web-post shear resistance of a pinned end circular arched cellular steel beam using ABAQUS nonlinear finite element analysis package. The trustworthiness of the finite element analysis results was confirmed by comparing them to the existing experimental investigation results. The main study parameters, such as the effect of a rise-to-span ratio, the radius of curvature, the impact of opening, the types of loading on elastic-plastic performance, and the buckling mode of an arched cellular steel beam, were investigated. Furthermore, the arched web-post finite element model was proposed and the shear resistance of the arched web-post was investigated. Also, the appropriateness of the currently existing different web-post shear resistance analysis approaches was reviewed and evaluated in determining the shear resistance of arched web-posts. The results showed that the web post-structural stiffness of a circular arched cellular steel beam was improved as the rise-to-span ratio increased under the mid-span concentrated load regardless of the rise-to-span ratio. However, under uniformly distributed vertical load, increasing a rise-to-span ratio beyond 0.35 or 140° subtended angles reduces the stiffness of circular arched cellular steel beams. The web post shear resistance analyzing approaches proposed by Panedpojaman et al. and SCI P-100 overestimate and yield unsafe results in determining the web-post shear resistance of arched web post cellular steel of low rise-to-span ratio.

A Study on the Lateral Ultimate Strength and Collapse Modes of Doubly Curved Stiffened Plates

Bows and stems are often subjected to wave slamming loads. Stiffened plates with curvatures in both longitudinal and transversal directions are the basic members of these structures. As a result, it is important to investigate the lateral ultimate strength of the doubly curved stiffened plates. In this study, the non-linear finite element method (NFEM) is selected to investigate the collapse modes and lateral ultimate strengths of the doubly curved stiffened plates. Additionally, the influences of curvature and geometrical properties on the collapse modes and ultimate strengths of doubly curved stiffened plates are investigated. In the NFEM analysis, a series of numerical simulations, covering different aspect ratios, curvatures, and structural scantlings are performed. Different collapse modes of doubly curved stiffened plates under lateral loading cases are observed. The relationships between the collapse modes and the geometrical properties are then discussed based on the numerical results. Moreover, the results also show that larger curvatures along the stiffeners and stronger stiffeners contribute more to the lateral ultimate strengths. Subsequently, an empirical formula is derived and verified for predicting the lateral ultimate strength of the doubly curved stiffened plates. The results of the empirical formula match well with numerical calculations.

The Effect of Hole Geometry on the Nonlinear Nanomechanics of γ-Graphyne Structures: A Finite Element Analysis.

Graphyne is a material that has unique mechanical properties, but little is known about how these properties change when the material has holes. In this work, the effect of hole geometry, considering circular, triangle, and rhombus hole configurations, on the mechanical nonlinear response of γ-graphyne structures is studied. Graphyne, graphdiyne, graphyne-3, and graphyne-4 structures are under investigation. An efficient nonlinear finite element analysis (FEA) method is adequately implemented under large deformations for this purpose. The study varied the size and shape of the holes to understand how these changes affect the nanostructure's mechanical response. The results indicate that the hole geometry significantly impacts the mechanical nonlinear response of γ-graphyne structures. The holes' size and shape affect the structures' elastic behavior, deformation, and strength. The findings can be used to optimize the design of γ-graphyne structures for specific mechanical applications. The study highlights the importance of considering the hole geometries in the design and fabrication of these materials.

A numerical study on rotational stiffness characteristics of the disk lock joint

Rotational stiffness characteristics of the disk lock joint have a significant effect on the load bearing capacity and stability of disk lock scaffolds. However, experimental researches on scaffold joints are usually expensive and time consuming, especially when different joint connection configurations and loading modes are involved. This paper explores the feasibility and effectiveness of the 3D nonlinear finite element analysis method for studying the rotational stiffness characteristics of the disk lock joint. Detailed geometric models of the disk lock joints are established and the geometric models are meshed with finite elements. The elastoplastic constitutive model based on the isotropic hardening law and the associated flow rule is used to describe the complete deformation process of the material, and the penalty stiffness method is applied to accurately simulate the interaction between different components. Thus the complete finite element models of the disk lock joints are established. Firstly, the loading processes of the one-way disk lock joint are simulated and verified by experiments. To further demonstrate the robustness and effectiveness of the finite element method, the loading processes of disk lock joints under different connection configurations and loading modes are simulated. The influences of connection configurations and loading modes on joint rotational stiffness are also investigated to reveal the load bearing mechanism of the disk lock joint, and thereby contribute to better predictions of the load bearing capacity of the disk lock scaffolds.

Effect of openings on the behaviour of rammed earth structures under quasi-static loading

Rammed earth (RE) is a centuries-old construction technique that uses renewable resources found in the surrounding environment. As for concrete or timber houses, doors and windows are mandatory. Until date, the effect of openings on the mechanical behaviour of RE structures has received little attention. The primary contribution of this research is to assess the impact of opening on the behaviour of RE structures. A three-dimensional finite element models of RE walls were developed and calibrated against three experimental tests by Lilley and Robinson (1995). In the experimental study, RE walls with the geometrical dimensions 2285 mm × 1220 mm × 305 mm (length × height × thickness) were constructed from unstabilized soil and evaluated under in-plane compression loading. The considered walls have two types of openings: arch-type and rectangular shape. The numerical results obtained through non-linear finite element method analysis demonstrate the pertinence of the proposed model for quantifying bearing capacity and failure modes. Using the verified numerical model, a parametric study was carried out to investigate the effects of material characteristics, the geometrical characteristics of the opening and finally the improvement options using lintel reinforcements.

Analysis methodology and design verification for strengthening moment-resisting caisson foundations

Many existing monopole towers rely on caisson foundations to resist the effects of large overturning moments. Increased loading on these towers, coupled with material deterioration and more stringent code requirements, often results in the overloading of the existing caissons. The strengthening of these caissons for additional overturning resistance presents many challenges and typically requires the installation of new piles. A pile cap is commonly used to connect the existing caisson to the new piles. The proper design of the pile cap has a critical importance in ensuring an effective stress transfer and creating a resilient foundation system. While a number of strengthening design approaches are repeatedly used in industry, there is a dearth of guidance and proven analysis methods to verify the performance achieved with these approaches. This study proposes a well-defined analysis methodology for the system-level structural design verification of the strengthened foundation systems. The methodology provides two routes, using either the strut-and-tie or nonlinear finite element analysis methods, to quantify the load, deformation, cracking, and failure responses. The methodology helps expose and address the weak aspects of the design using an iterative design improvement process. A common strengthening design approach from industry, involving a moment-resisting caisson strengthened with four concrete piles and a pile cap, is used as a case study to demonstrate the application of the methodology. The results demonstrate that the methodology provides significant insight into the system-level behavior both at the serviceability and ultimate limit states. The analysis results are found useful in identifying the locations where modified bar detailing could significantly improve the system performance. The improved design from the methodology provided a 56 % increase in the load capacity for the case-study foundation while still using the same amounts of reinforcing steel and concrete as compared to the initial design before the application of the proposed methodology. This paper presents the studies undertaken, conclusions reached, and recommendations made for developing resilient pile cap designs for strengthening moment-resisting caisson foundations.

Numerical simulations of the sliding impact between an ice floe and a ship hull structure in ABAQUS

This paper studies the hull structural responses of a steel grillage subjected to sliding ice loads, which have been rarely investigated in the literature. Sliding ice loads are modelled using nonlinear finite element analysis (NLFEA) method; and Abaqus Explicit is adopted as the numerical solver. Deformations and damages of ice and steel are both considered. A rigid ice model is also simulated for comparison purposes. The hull’s local structural responses under different load cases, including deformation, contact forces, and energy distribution, have been analysed. The effects of static structure-to-structure friction coefficient and the relative stiffness between ice and structure are studied. It is found that the deformation of structures will increase the total friction coefficient, which is defined as the ratio of the friction force (the tangential contact force) to the normal contact force. When the ice floe is considered rigid, the static friction coefficient has little effect on the local structural responses of the hull. If using a higher-strength steel material for hull structures in the ice-classed ship design, the hull’s deflection and total friction decrease, and the hull dissipates less energy as expected. Moreover, stationary load cases with the same loading condition in the normal direction as sliding load cases are also simulated. When using the deformable ice material model, the simulation results show that the hull’s final contact forces and deflection in stationary load cases are larger than those in sliding load cases. Besides, the effect of steel material is more significant in stationary load cases than in sliding load cases.

Seismic Performance of Precast Concrete Frame Beam-Column Connections with High-Strength Bars.

As the construction industry is striding towards the industrialization of green buildings, a precast concrete frame beam-column joint with high-strength reinforcement was proposed. Simulate reversed cyclic loading was carried out on two precast connections and one cast-in-place connection to examine the seismic behavior of the proposed new precast connection. The main test variables between the two precast connections were the strength of the reinforcement at the bottom of the beam. The failure shape, hysteresis curve, skeleton curve, strength, deformation ability, stiffness degradation, and energy dissipation were monitored and compared with the cast-in-place connection. The findings of this paper showed that the precast joints had good strength reserve, and the seismic performance in the later stage of loading even exceeds the cast-in-place joints. It was also found that the plastic hinge zone of the beam could be moved away from the column surface via reinforcement method. Additionally, based on the experiment, a detailed nonlinear finite element analysis (FEA) method was developed to reproduce the test response of specific types of bending moment-resistant precast concrete beam-column connections under a reversed loading test, which provided a theoretical reference for further research of the connections.

Nonlinear 3D Finite Element Model for Square Composite Columns Under Various Parameters

Composite columns are frequently used in constructing high-rise structures because they can minimize the size of the building's columns while increasing the floor plan's usable space. This study aims to create a nonlinear 3D finite element model for square composite columns designed for solid and hollow columns with various multi-skin tubes subjected to loads at eccentricities of (30 and 60) mm, compressive strength, and mesh size using the ABAQUS software. The comparison was based on the experimental data of six references of composite columns. While the compressive strength of concrete increases, the stiffness of the composite column rise. The ratio of concrete compressive strength values for composite column increased by (0, 12.3, 17.8, and 26.7 percent) for (fc'=25, 31.96, 35, and 40) MPa, respectively. The results of the different mesh sizes (20, 40, and 60) mm are showing; The experimental results and the finite element solution developed using the (20 X20) mm element correspond well. The nonlinear finite element analysis method was used, and the finite element outputs results were confirmed to be in favorable agreement with the experimental data

Design of a Morphing Compliant Mechanism With Separate Gripping and Retraction Modes Using a Single Actuation

Abstract A key aspect of robotics and automation is continuous repetition of predefined travel and actions. One such example is a robotic gripper, gripping an object, retracting, and displacing it. Usually, two separate actuations are needed to implement the decoupled gripping and retraction modes. In this article, a morphing compliant gripper is proposed that grips an object (X displacement) and retracts it linearly (Y displacement) based on one single actuation, to reduce the input efforts. The mechanism is first designed by the rigid body replacement method and is based on the double-slider mechanism. Morphing is successfully achieved through the use of contact-aided features and a pseudo spring beam to decouple the X and Y displacements. The design is comprehensively analyzed through the nonlinear finite element analysis method and is optimized using the integrated design exploration tools. Simulation results closely match an ideal X and Y displacement path and a displacement-activated transition from X displacement to Y displacement while minimizing the input actuation force. Finally, a 3D-printed prototype is made and preliminarily tested to verify the design.

Cyclic lateral behavior of NLFEA heat-damaged circular CFT steel columns confined at the end with CFRP composites

In this study, the nonlinear finite element analysis (NLFEA) method has been adopted to prove the CFRP's effectiveness in restoring the performance of heat-damaged CFT circular steel columns and controlling the columns' failure mode. The simulated CFT column model was firstly checked for validity using previously-conducted experimental research. Then, the model was extended to investigate the impact of the number of CFRP layers (0, 5, 6, 7, 8, 9, and 10 layers) and elevated temperature (20 °C, 200 °C, 400 °C, and 600 °C). Therefore, this study provides an NLFEA of twenty-eight models for CFT circular steel columns wrapped with various layers of CFRP composites at its end region, which represents the critical location in terms of the lateral load capacity. Also, wrapping the specimens' ends helps prevent the occurrence of outward local buckling, resulting in enhancing the specimens' strength, enlarging net drift, and increasing energy dissipation. The study results showed that using five to ten CFRP layers significantly improved the performance of the NLFEA CFT circular steel column models. Nevertheless, using nine or ten CFRP layers had almost the same impact of using eight layers. The NLFEA results showed that the external repairing of heated damaged CFT column with CFRP composite enhanced the cyclic performance, and the efficiency of CFRP composite increased with the heat damage level.

Computed Tomography-Based Stiffness Measures of Trabecular Bone Microstructure: Cadaveric Validation and In Vivo Application.

ABSTRACTOsteoporosis causes bone fragility and elevates fracture risk. Applications of finite element (FE) analysis (FEA) for assessment of trabecular bone (Tb) microstructural strength at whole‐body computed tomography (CT) imaging are limited due to challenges with Tb microstructural segmentation. We present a nonlinear FEA method for distal tibia CT scans evading binary segmentation of Tb microstructure, while accounting for bone microstructural distribution. First, the tibial axis in a CT scan was aligned with the FE loading axis. FE cubic mesh elements were modeled using image voxels, and CT intensity values were calibrated to ash density defining mechanical properties at individual elements. For FEA of an upright volume of interest (VOI), the bottom surface was fixed, and a constant displacement was applied at each vertex on the top surface simulating different loading conditions. The method was implemented and optimized using the ANSYS software. CT‐derived computational modulus values were repeat scan reproducible (intraclass correlation coefficient [ICC] ≥ 0.97) and highly correlated (r ≥ 0.86) with the micro‐CT (μCT)‐derived values. FEA‐derived von Mises stresses over the segmented Tb microregion were significantly higher (p < 1 × 10−11) than that over the marrow space. In vivo results showed that both shear and compressive modulus for males were higher (p < 0.01) than for females. Effect sizes for different modulus measures between males and females were moderate‐to‐high (≥0.55) and reduced to small‐to‐negligible (<0.40) when adjusted for pure lean mass. Among body size and composition attributes, pure lean mass and height showed highest (r ∈ [0.45 0.56]) and lowest (r ∈ [0.25 0.39]) linear correlation, respectively, with FE‐derived modulus measures. In summary, CT‐based nonlinear FEA provides an effective surrogate measure of Tb microstructural stiffness, and the relaxation of binary segmentation will extend the scope for FEA in human studies using in vivo imaging at relatively low‐resolution. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Impact of sulfate damage on the behavior of full-scale concrete bridge deck slabs reinforced with FRP bars

This paper is aimed to analyze the performance of reinforced-with-FRP, sulfate-damaged concrete bridge deck slabs under concentrated loads, using the nonlinear finite element analysis (NLFEA) method. For experimentation purposes, twenty-seven full-scale models have been prepared to simulate concrete bridge deck slabs, with a length of 3000 mm and a width of 2500 mm. The parameters of the study were: (i) type of reinforcement, as three types were tested: glass FRP (GFRP), carbon FRP (CFRP), and steel; (ii) bottom transverse reinforcement ratio (ρ = 0.38, 0.46, and 0.57); and (iii) sulfate damage level, which consisted of three levels: Level 0 (undamaged), level 1 (73 days), and level 2 (123 days). All of the slabs models were equipped with two parallel girders of steel as supporters. To be able to analyze the models' performance up till failure, the load exerted by sustained truck wheels (87.5 kN CL-625 truck) was simulated by subjecting each slab model to a monotonic single concentrated load, with a contact area of 600 × 250 mm, at the center of the models. The simulated models encountered a punching shear mode of failure. The analysis showed that the models that were strengthened with CFRP and GFRP bars exhibited a remarkable improvement in the models': ultimate load, elastic stiffness, post-cracking stiffness, elastic energy absorption, and post-cracking energy; whereas, there was less influence on the models' ultimate deflection, compared to the ones strengthened with steel.

A Compact Mirror-Symmetrical XY Compliant Parallel Manipulator for Minimizing Parasitic Rotations

Abstract The design of XY compliant parallel manipulators (CPMs) remains challenging considering the tradeoff between mirror-symmetry for better constrained undesired rotations and a small footprint, although a significant number of XY CPMs have been reported in extensive applications. This paper presents a new XY CPM using mirror-symmetry without increasing its footprint, mainly aiming to reduce the undesired parasitic rotations of input and output motion stages. The concept of mirror-symmetry is deployed to tackle the parasitic rotations, with the help of using a multilayer compact XY CPM design method. A nonlinear and analytical model of the proposed XY CPM is derived using free body diagrams and the beam constraint model (BCM) to accurately analyze its performance characteristics over a large range of motion. The designed XY CPM is then verified by the nonlinear finite element analysis (FEA) method. Finally, the proposed multilayer design is fabricated using two pieces of aluminum plate and it is mounted in a measurement system to experimentally validate several performance characteristics. The analytical, FEA, and/or experimental results show that the proposed design can sufficiently constrain undesired motions including parasitic rotation of input and output stages, cross-axis coupling error, and actuator isolation index. Compared with exiting designs, the proposed design also shows its merits in large motion range and out-of-plane stiffness.

Strength Analysis Due to the Elongation’s Ladder of Cutter Suction Dredger Ship

The more frequent mining activities are carried out, the deeper the tin on the seabed, therefore many ship owners want to increase the length of the ladder on production suction vessels. The owner of the KIP Timah 8 suction boat will increase the length of the ladder to 70 meters, which previously was only 58 meters. The paper research are the response of the ladder structure before and after being extended, the limit strength of the ladder structure in the pulley area, then the ultimate strength of the longitudinal ladder structure due to the vertical bending moment. Lenght of the ladder construction subsequently increases commencing 58 m, 62 m, 66 m, to 70 m with each increase in length varying the slope angle of the ladder starting from 0o, 30o, 45o, to 60o. This paper uses a numerical method with the help of ansys software. The structure being reviewed is only in the ship ladder area. The response of the ladder structure before and after being extended, the maximum stress value occurs in the strut construction which is 49 meters from the ladder shaft, which is 56.88 N/mm2 and the maximum shift is 14.28 mm when the ladder length is 70 meters and still meets the allowable stress. Investigation of the limit strength using the Nonlinear Finite Element Analysis (NLFEA) method. Based on the results the analysis of the strength longitudinal ladder structure in the hogging and sagging conditions 42 meters from the ladder shaft, the maximum deflection in the column is 131.73 mm from the initial position before being loaded. While at an angle of 60 degrees it will collapse when deflection 66.17 mm. The results of the analysis showed that the load acting on the ladder the pipe load, cutter load and cutter torque the resulting stress still meets the stress that the longer ladder is directly proportional to the resulting stress and deflection value and the greater the slope of the ladder, the smaller stress and deflection.