Ship longitudinal strength analysis is critical for ensuring structural integrity and safety throughout the vessel's operational life. This study presents a comprehensive finite element analysis (FEA) of the MST-3 vessel's longitudinal strength using ANSYS software, focusing on hull girder behaviour under extreme loading conditions. The research employed advanced computational methods to evaluate structural response under sagging and hogging conditions, incorporating material nonlinearity, initial imperfections, and residual stresses from welding processes. The MST-3 vessel, with principal dimensions of 185.0m LOA, 28.5m beam, and 15.2m depth, was modelled using 68,530 finite elements (SHELL181 and BEAM188) with 72,840 nodes. The analysis incorporated AH36 steel material properties with yield strength of 355 MPa and considered initial deflections following elastic buckling modes. Boundary conditions were applied using multi-point constraints (MPC) at the model extremities to simulate simply supported conditions. Results demonstrate that the vessel meets all classification rule requirements with significant safety margins. The ultimate bending moment capacity reached 1,245,680 kN⋅m under sagging conditions and 1,187,420 kN⋅m under hogging conditions, exceeding design requirements by 39.1%. Maximum von Mises stress of 284.7 MPa occurred at hatch corner connections, representing 80.2% of yield strength. Critical stress concentrations were identified at deck-side shell junctions (267.3 MPa), engine room bulkheads (245.8 MPa), and cargo hold corners (231.5 MPa). The progressive collapse analysis revealed ductile failure behaviour with adequate post-ultimate strength reserves. Buckling analysis showed minimum safety factors of 1.85 for all structural components, with longitudinal girders exhibiting the lowest buckling margins. The finite element methodology demonstrated excellent correlation with analytical beam theory solutions, validating the computational approach with maximum differences below 1%. Key findings indicate that while the vessel structure is adequate, hatch corner reinforcement is recommended to address stress concentrations. The study concludes that modern finite element techniques provide reliable tools for ship structural assessment when properly validated. The developed methodology offers practical engineering solutions for longitudinal strength evaluation and optimization of marine structures.

The study investigates how different finite element modelling assumptions affect the predicted load-resisting behavior of welded beam-column connections in double-span steel beam systems subjected to column-removal scenarios. Existing numerical studies commonly neglect fracture and material degradation, which may result in unconservative estimates of structural capacity. To address this limitation, nonlinear static analyses were performed in ABAQUS using two simplified modelling approaches: (i) non-fracture models that exclude plasticity damage and element deletion, and (ii) fracture-based models that incorporate ductile damage criteria with element deletion. Structural responses were evaluated in terms of load-displacement relationships, moment-rotation behavior, and the development of tensile catenary action. The results indicate that accounting for plasticity damage and fracture significantly alters the predicted response, leading to markedly lower strength and deformation capacity compared to non-fracture models. In particular, the inclusion of fracture mechanisms resulted in an approximate 50% reduction in load-carrying capacity and catenary resistance. These findings demonstrate that neglecting fracture behavior can substantially overestimate the robustness of welded beam-column connections under extreme loading conditions. The study underscores the importance of structural performance in progressive collapse analyses.

In comparison to the double cable-plane arch bridges, the single cable-plane tied arch bridge is notably susceptible to progressive collapse due to the vulnerability and failure of its unique unilateral cable system during service, highlighting its insufficient structural robustness. The Nanfang’ao Bridge, a collapsed structure located on the seashore of Taiwan, China, featuring a single cable-plane tension-tied arch, was selected as an analytical model for the cable-loss-induced progressive collapse study. A novel robustness assessment methodology, utilising a cable loss block, is proposed for the structural assessment of tension-tied-arch steel bridges after a sudden cable breakage event. The progressive collapse analysis suggests that the single-cable-plane configuration results in inadequate robustness of the weak arch-strong deck bridge, subsequently leading to complete collapse following the fracture of cables due to corrosion. Furthermore, a parametric study on robustness, considering traffic loads, cable pretension, area, and corrosion, reveals that the shortest cables at the bridge ends are critical for robustness, and increasing the cable area improves the structural robustness of the single-arch bridges. Failure risk can be mitigated both by increasing the design bearing capacity of the structural components and by conducting more frequent inspection and maintenance actions.

High-fidelity finite element model for truck collision-induced progressive collapse analysis of steel frame structures with composite floors

A unified regression model for the force-based dynamic increase factor in relation to progressive collapse analyses of frame structures

The ultimate strength of the hull girder represents one of the key criteria in the design of large thin-walled steel structures such as ships and aircrafts. For large ship structures, the hull girder’s ultimate strength is expressed as the maximum internal vertical bending moment that the hull structure can absorb before collapse. In this paper, a progressive collapse analysis of the hull girder has been performed for several different variants of large steel thin-walled box girders, taken from the literature as benchmark cases, using the nonlinear finite element method (NLFEM), considering both material and geometrical nonlinearity. Results from the performed calculations were compared to the numerical results of other researchers published in the literature, as well as the results of our physical experiment. The influence of initial geometrical imperfection on the value of the ultimate bending moment achieved with NLFEM has been investigated.

To investigate the coupled effects of cable corrosion on the ultimate strength and fatigue performance of cable-stayed bridges, sophisticated numerical simulations incorporating established corrosion mechanisms were conducted. Corrosion-induced degradation was modeled through cross-sectional area reduction and material property deterioration, with specific emphasis on wire elongation capacity attenuation. Three finite element models representing steel cable-stayed bridges with distinct spans (300m, 600m, and 900m) were subjected to progressive collapse analysis and fatigue assessment. The results indicate that: (1) Structural failure consistently manifested through plastic hinge formation and fracture at the mid-span girder across all models, accompanied by partial plastification at the tower base; (2) Increased span length elevated cable stress at failure, thereby amplifying the influence of cross-sectional area reduction on ultimate strength; (3) Reduction of wire elongation rate from 4% to 3% or 2% resulted in marginal ultimate strength reductions, whereas attenuation to 1% induced precipitous capacity decline; (4) Under concurrent minimum cable area and elongation rate conditions, the ultimate load-bearing capacity of all bridge configurations experienced an approximate 50% reduction; (5) Corrosion significantly compromised fatigue performance at all cable positions, with localized pitting corrosion exacerbating stress concentration effects and accelerating cross-sectional degradation, consequently diminishing fatigue life.

This paper explores methods of simulating the behaviour of building structures under progressive collapse conditions through alternative models of different levels of structural idealization. Such models have been applied in many previous studies, but there is insufficient information regarding their reliability and their ability to represent actual structural behaviour as the level of idealization is reduced. To address this, the study adopts the alternative load path method through the well-established concept of notional column removal, performed via nonlinear static analyses of models with different levels of structural idealization. The focus is on the interaction between the directly affected structural members and the surrounding structure, which is shown to significantly influence the overall response under progressive collapse. The results demonstrate that this interaction depends on multiple factors and cannot be reliably captured when the surrounding structure is not explicitly modelled. Building on this finding, the study systematically evaluates how reduced models can be enhanced to better represent these interactions and proposes strategies for defining boundary conditions that preserve global structural behaviour. Overall, the study advances understanding of model idealization effects and provides practical guidance for developing efficient reduced models for progressive collapse simulations without compromising essential aspects of structural response.

Most design codes treat masonry infill walls as non - structural elements, and in the analysis of steel or reinforced concrete (RC) frame structures, their presence is often neglected. However, numerous studies have shown that infill walls significantly inf luence the strength, stiffness and ductility of the structure. Therefore, it is crucial to consider the contribution of infill walls to the building's behavior. Accurate modeling of the infill walls requires knowledge of the mechanical properties of masonry, various interacting parameters, and the contact conditions along the interface between the infill and the surrounding frame. Two prim ary techniques used in the analysis of infilled frame structures are macro - modeling and micro - modeling. Micro - modeling utilizes Finite Element (FE) software to represent the masonry panel as composed of many elements that simulate the bricks and mortar. In contrast, macro - modeling treats the masonry panel as a few elements, typically modeled as one or more compressive diagonal struts. Both techniques aim to capture the nonlinear behavior of the materials. The objective of this study is to assess the influence of the infill walls on the progressive collapse resistance of RC framed structures. To achieve this, an RC frame experimentally tested by Li et al. (2016) is modeled in Abaqus/Explicit software in two configurations: bare frame (without infill walls) an d infilled frame (with infill walls). The frame consists of four bays and two stories, and progressive collapse is triggered by the failure of the middle column from the first story. This failure is simulated through a step - by - step unloading process in a displacement - controlled manner. To evaluate the progressive collapse behavior of the two numerical models, nonlinear explicit dynamic analysis is adopted to simulate the quasi - static loading scheme. The Concrete Damaged Plasticity (CDP) model is used for both concrete and masonry , with the compressive stress - strain relationship following the Kent - Scott - Park constitutive model. The steel reinfor cement bars material properties are specified based on a bilinear stress - strain relationship. Tie - type connections are employed to model the interaction between the RC frame and masonry elements, while general contact is used to simulate th e interaction between masonry elements. The resistance force (applied vertical load) versus the vertical displacement of the middle column is monitored up to a displacement of 500 mm. The progressive collapse behavior of the frame is divided into four stages. The numerical results obtained for both models show good agreement with the experimental ones. It was found that during the first deformation phase (when adjacent and exterior columns moved outward), the infilled frame model resisted a vertical force approximately 4.8 times greater than the bare frame model. In conclusion, completely neglecting the infill walls in the progressive collapse analysis of RC framed structures leads to unrealistic results.

Study on the performance of base-isolated structures against progressive collapse and parametric analysis

Progressive collapse analysis of precast frame structures based on discrete element method

The spread of an initial local failure from element to element resulting eventually in the collapse of an entire structure or a disproportionately large part of it, is called as progressive collapse. This review paper provides a comprehensive overview of the progressive collapse of multistorey Reinforced Concrete (RC) buildings, focusing on the causes, analysis methods, and mitigation strategies. The paper synthesizes current research and design guidelines from various codes, highlighting key factors influencing collapse resistance and the role of modern analytical techniques which will be helpful in the assessment of progressive collapse. It also discusses the critical aspects of load redistribution, structural redundancy, and ductility in preventing the severe events.

Disasters cause significant damage to structural elements in the affected regions throughout the service life of buildings. This damage typically manifests as the loss of structural elements or a reduction in load-bearing capacity. Many countries conduct research and publish regulations and analytical methods to minimize such damage. One of the primary references in this context is the UFC 4-023-03 guide, titled "Design of Buildings to Resist Progressive Collapse," issued by the United States Department of Defense. This guide addresses the phenomenon where a structure experiences element loss due to various disasters, potentially leading to progressive collapse. The guide proposes three methodologies for assessing the progressive collapse resistance of structures: the Alternative Path method (AP), the Tie Force method (TF), and the Enhanced Linear Resistance method (ELR). In developing countries such as Türkiye, there are no specific regulations addressing the progressive collapse phenomenon. As a result, structures of critical importance are constructed without such provisions. In this study, a reinforced concrete building was analysed using the Enhanced Linear Resistance method, following the UFC 4-023-03 guidelines and the Turkish Earthquake Code (TEC). The objective is to identify the differences and commonalities between the UFC and the regulatory framework in Türkiye, where structures are not explicitly designed to resist progressive collapse. At the conclusion of the study, shear demand values of structural elements and other relevant parameters were comparatively presented.

This study examines the progressive collapse behavior of curved cable-stayed bridges, evaluating deck curvature (75-175m), pylon types (H-shape, single), and cable systems (fan, harp) using 24 MIDAS Civil finite-element models.Analyses under IRC Class 70R loads reveal deck curvature intensifies torsional demands, with H-pylons experiencing 30-35% higher torsion in harp systems versus fan systems.Single pylons exhibited minimal cable-geometry sensitivity but increased longitudinal moments (Y-direction) under tighter curvatures.H-pylons demonstrated reduced longitudinal moments but higher Zdisplacements in fan systems, while harp systems showed controlled displacements.Time period analysis indicated fan systems' lower stiffness, with periods 10-15% longer than harp systems.Cable failure simulations highlighted inner cables near pylons redistributing 25-40% less force than outer cables, improving collapse resistance.Curved decks induced force imbalances, with curvature-side cables sustaining up to 18% higher pretension.The study advocates harp configurations with H-pylons for curved spans due to balanced load distribution and redundancy, while emphasizing the necessity for curvature-specific IRC guidelines.These findings offer critical insights for optimizing resilience against progressive collapse in geometrically complex cable-stayed bridges, informing design strategies to enhance structural robustness.

A coupling framework for impact-induced progressive collapse analysis of RC frame structures

This study investigates the progressive collapse (PC) behavior of three reinforced concrete (RC) structure using the Applied Element Method (AEM), focusing on corner and intermediate edge column removal. The research evaluates AEM’s effectiveness in capturing structural failure mechanisms and its reliability in progressive collapse analysis. A 3×3-bay RC frame with varying story heights (4, 7, and 10 stories) was analyzed in Extreme Loading for Structures (ELS) software. Six different scenarios were examined by varying the number of stories and the removed column locations. The numerical models incorporated TBEC 2018-compliant lap splice extensions, mesh refinement at plastic hinge locations, and slab adjustments. Two progressive collapse scenarios were considered: (1) sudden removal of a corner column and (2) removal of an intermediate edge column. The displacement response at the upper end of the removed section was monitored over 3 seconds, accounting for vibration damping. For this robust structural example, numerical results revealed that taller buildings exhibited greater transient and residual displacements, with the 10-story case reaching up to twice the displacement of the 4-story case. Moreover, intermediate edge column removal consistently led to higher displacement values than corner column removal, especially in taller structures. The results highlight the influence of column location and story height on collapse progression.

The double earthquake that struck Türkiye on February 6, 2023 killed over 50,000 people. It also caused the collapse of thousands of low-rise reinforced concrete structures in the seismic area, resulting in incredible damage. To study the reasons for the progressive collapse of numerous buildings, a nine-story concrete frame structure was established in this study, and the elastic-plastic time-history analysis under the double earthquake was performed. The element failure criterion was defined using the max equivalent compressive strain, refining the damage initiation point and transmission path of the proposed structure. The results showed that: 1. The natural period of vibration of the low-rise concrete frame structure in the seismic area is in the peak spectral acceleration region of the first earthquake, which maximizes the earthquake damage force. 2. The first strong earthquake disabled the main load-bearing columns on the ground floor of the structure, resulting in collapse within a few seconds of the second earthquake. 3. The seismic damage investigation showed that the low-rise frame structure had insufficient longitudinal reinforcement laps, insufficient transverse reinforcement and stirrups, and weak embeddedness between longitudinal bars and concrete. These issues have amplified the damage degree. 4. Despite the comprehensive building seismic regulations in Türkiye, the most pressing problem may be the long-term regulatory failure of the authorities.

Progressive Collapse Analysis of Half-Through Truss Bridges Considering Corrosion Effects

Finite Element Method (FEM) serves as a critical numerical tool for analyzing complex composite and steel structures. This article aims to evaluate the versatility and accuracy of FEM in predicting structural behavior across diverse applications. The study reviews three specific cases: reinforced concrete encased steel columns, haunched gusset plate connections in cold-formed steel, and a mixed element method for progressive collapse analysis. Numerical simulations were validated against experimental data to assess damage mechanisms, ductility, and energy dissipation. The results demonstrate a 42% improvement in lateral capacity for composite structures and a prediction deviation of 25-29% in cold-formed steel connections. Furthermore, the mixed element method exhibited high precision with less than 2% deviation in dynamic analyses. These findings confirm FEM's reliability in optimizing structural design and developing adaptive methods for failure prediction.

In current practice, the analysis of progressive collapse in building structures widely employs the alternate load path method. However, there are very few collapse tests that can be utilized under blast loads, especially for investigating the degradation mechanism of progressive collapse resistance in post-blast building structures. In this study, the degradation mechanisms and methods for damage assessment of reinforced concrete structures under blast loads were investigated through numerical analysis. A substructure model derived from explosion loads based on a drop-hammer testing machine was validated by comparing with test results, and the established model accurately captured three typical failure modes in the substructure columns and confirmed the axial tensile effects of the columns on the adjacent components. A substructure damage assessment method was used to assess the degree of damage in a 5-story reinforced concrete frame structure under different explosion scenarios. The results show that the degree of damage distribution of the reinforced concrete frame structure exhibited an S-shaped distribution under corner column blast scenarios while an arch-shaped distribution was observed for middle column blast scenarios. Furthermore, empirical formulas based on the explosive mass and distance ( M- R) curves were established. These empirical formulas can help to rapidly predict the damage levels of RC frame structures for a given explosion scenario within a certain scope.