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Tendon and ligament disorders are common indications for ankle surgery. Numerous surgeries and related modifications, ranging from simple repairs and debridement to complex reconstructions with tendon transfers or graft, are available. Knowledge of postoperative imaging appearances of common ankle surgeries is critical to identify complications and aid assessment of clinical treatment failure. This comprehensive review article discusses the surgical indications, techniques, imaging appearances, and complications—specifically those related to minimally invasive or arthroscopic surgery—for various ankle and foot conditions. It includes anatomical (Brostrom type) and nonanatomical lateral ligament repairs for ankle instability. Medial compartment procedures are described, such as peroneal tendon and retinacular repairs, as well as treatments for progressive collapsing flatfoot deformity, formerly known as posterior tibial tendon dysfunction or acquired flatfoot deformity. We also examine posterior compartment procedures, focusing on Achilles tendon repairs. Primary imaging modalities covered are magnetic resonance imaging, ultrasound, computed tomography, and radiographs, including expected postoperative appearances and the usefulness of each modality. [ABSTRACT FROM AUTHOR]

Since its introduction, weight-bearing computed tomography (WBCT) has gained prominence due to its ability to produce accurate three-dimensional images under natural loading conditions, making it particularly useful for assessing complex foot deformities. This review aimed to focus on the diseases of the foot and categorized the pathological conditions into forefoot disease (hallux valgus), midfoot disease (Lisfranc injuries and midfoot osteoarthritis), and progressive collapsing foot deformity. For each category, the authors detail how WBCT enhances diagnostic accuracy and informs treatment strategies. In hallux valgus, WBCT allows for more precise measurement of established parameters and reveals crucial information about metatarsal pronation and ray instability. For midfoot pathologies, WBCT's superiority in detecting subtle Lisfranc injuries and characterizing midfoot osteoarthritis is emphasized, highlighting the development of novel measurement techniques. The review extensively covers the application of WBCT in assessing the complex three-dimensional features of PCFD, including hindfoot valgus, midfoot/forefoot abduction, medial column instability, peritalar subluxation, and valgus tilting, presenting several WBCT-specific measurements and the use of distance mapping to quantify joint surface interaction. The authors conclude that WBCT, potentially enhanced through integration with artificial intelligence (AI), represents a significant advancement in foot and ankle care, promising improved diagnostic accuracy, streamlined treatment planning, and, ultimately, better patient outcomes. [ABSTRACT FROM AUTHOR]

The fracture of energy-dissipation components with low-yield-point (LYP) steels under seismic action may cause the progressive collapse of the structures. Therefore, it is essential to predict the fracture of various LYP steel energy-dissipating components under the seismic action and ultra-low cycle fatigue loading. To address this issue, a seismic fracture prediction method for LYP225 steel subjected to cyclic loading was proposed and validated. First, based on updated Voce–Chaboche model and small strain assumption, an improved Voce–Chaboche (IVC) model was proposed to reasonably characterize the stress–strain relation of LYP225 steel under cyclic loading. Five cyclic coupon tests were conducted to validate the proposed IVC model. The proposed IVC model is foundational for accurately predicting the fracture of LYP225 steel under cyclic loading. Second, a general fracture model accounting for the effects of stress states, linearity, nonlinearity, and loading history was developed to predict the fracture of LYP225 steel under cyclic loading. Twenty cyclic tests with various notch details were conducted to validate the proposed fracture model. The experimental results were presented and analyzed in detail, including from the results of scanning electron microscopy. Third, the calibrated fracture model can accurately predict the fracture index and cumulative displacement of fracture initiation point, with an average accuracy of 99.3% and 95.3%, respectively. The proposed fracture model was incorporated into the developed material subroutine to simulate the steel failure. Numerical results were in good agreement with experimental results, and fracture initiation points for all specimens can be reasonably predicted. Finally, the proposed IVC model, fracture model, and their numerical implementation would contribute to reasonably predict the potential failure of steel members, connections, and structures under the seismic actions, fatigue, and cyclic loadings. Due to the high prediction accuracy and practicality of the proposed fracture model, it is recommended to integrate it into finite-element software and use it for engineering applications. This action also would contribute to reduce or avoid potential casualties and property losses in earthquake disasters. [ABSTRACT FROM AUTHOR]

The structural assessment of masonry construction often requires the use of nonlinear 2D and 3D finite element analysis. This work describes a strategy for using energy outputs from such analyses to accurately assess failure conditions precipitated by increasing lateral load. The methodology relies on the analogy between plastic strains and fracture that is inherent to the concrete damaged plasticity (CDP) macro-model used to represent the quasi-brittle behavior of masonry material. At critical conditions, energy imparted to a structure by loading can no longer be completely stored as elastic strain energy and must be dissipated. This occurs with fractures in masonry, which are represented with plastic strains when using CDP material. The development of plastic dissipation energy can therefore be used as a measure for understanding the progressive collapse of a structure, as we illustrate with the following three case studies analyzed using Abaqus/CAE Explicit: the massive earthen pyramid at Huaca de la Luna (Trujillo, Peru), the Roman pozzolanic concrete vault of Diocletian's Frigidarium (Rome, Italy), and the mixed-material triumphal arch of the San Pedro Apóstol Church of Andahuaylillas (Peru). The method is verified by other measures of failure and has particular applicability for seismic analysis of complex masonry and earthen structures. [ABSTRACT FROM AUTHOR]

AbstractIn the past decades, progressive collapse (PC) has been of growing importance. Better understanding this phenomenon is mandatory to propose ad hoc mitigation and design approaches. Many experimental studies are carried out on sub-assemblies in quasi-static conditions due to setup and cost of full-scale dynamic tests. Numerical simulations describe dynamic responses of whole structures, although result interpretation can prove tricky due to models’ complexity. Recommendations account for dynamic effects, combining static analyses with dynamic amplification factors; however, this cannot be applied to all types of PC scenarios. Thus, a new testing method is proposed: sub-structured pseudo-dynamic experiments are adapted to the PC framework. Sub-structuring couples an experimentally tested critical member with a dynamic finite element model of the whole structure. The latter simulates inertial and viscous forces, while the static contribution of the critical member is tested in quasi-static conditions. This article considers a column removal scenario on a reinforced concrete frame. The structure is modelled using multi-fibre beam finite elements. The tested member consists of the lower floor’s beams, subjected to compressive arch and tensile catenary actions. Pushover and PsD tests are presented, and highlight the interest of the method in providing additional information on the dynamic response. [ABSTRACT FROM AUTHOR]

Flat slabs supported by columns without beams are widely used in construction owing to their economy and efficiency. However, brittle punching shear failure at slab–column connections can cause progressive collapse. UHPC has a higher tensile strength than NSC and, when appropriately reinforced with steel fibers, exhibits strain hardening after initial cracking. These properties make Ultra-High-Performance Concrete (UHPC) ideal for durable, thin, low-cost bridge decking and heavily loaded elements and an excellent choice for improving slab–column connections that have experienced punched shear failure. This study explores the impact of UHPC layers on the punching shear behavior of reinforced concrete slabs. Sixteen slab specimens were tested with variations in UHPC layer thickness, placement, and column shape. Results demonstrate that incorporating UHPC layers significantly enhances punching shear resistance, increasing ultimate load capacity by 27–91% compared to reference specimens. Notably, thicker UHPC layers (75 mm) and bottom-placed layers exhibited superior performance in terms of ductility and toughness. Square columns outperformed circular ones in resisting punching shear. Additionally, thicker layers reduced initial stiffness, while debonding issues in 25 mm layers adversely affected structural performance. This research provides valuable insights for optimizing UHPC configurations to improve the punching shear resistance of concrete slabs, offering promising solutions for high-load structures in modern construction. [ABSTRACT FROM AUTHOR]

The sudden loss of columns due to abnormal loads demonstrates a remarkable example of a localized failure that might ultimately result in the progressive collapse of the complete steel-framed structures. In this study, finite element (FE) simulations are implemented by utilizing ABAQUS-Explicit to investigate the progressive collapse of two-storey steel reduced beam section (RBS) frames with web openings. The reliability and accuracy of the FE models are validated by comparing the obtained results with currently available experimental test results. A numerical investigation is conducted on twenty-eight RBS frames, each with a distinct web opening form (i.e. circular, square, and hexagon holes), different sizes of (D = 75, 90, and 105 mm), and varying distances of (25, 50, and 100 mm) from the center of the flange-reduced to the web opening. The failure modes, load-displacement characteristics, and development of catenary action are evaluated. The results showed that the specimens with square holes showed a greater degree of damage and lower load-carrying capacity compared with the specimens that have circle and hexagonal holes. In addition, an increased opening size resulted in a decrease in load-bearing capacity at small distances, thereby resulting in an increased capacity at a large distance.

Beam-to-column connections are crucial for maintaining robustness of a framed structure against progressive collapse, especially in a fire scenario. Existing studies for component-based methods as a balance between accuracy and efficiency primarily focus on ambient-temperature conditions and individual connection types. This study proposes a high-temperature component-based method for top-and-seat-with-web-angle (TSWA) connections, introducing coefficients to enhance accuracy and incorporating temperature-dependent material properties. The influence of plate thicknesses, bolt diameters, edge distances, end distances and temperatures on the load-bearing behaviour of components are examined. A universal theoretical prediction model for the spring stiffness of components is established, applicable to various connection sizes, loading directions and temperature conditions. The accuracy and efficiency of the proposed method are validated against experimental results, with an error margin within 3 %. The advantage of simplification and generalization makes the proposed method suitable for performance-based structural fire design of steel connections. • A component-based method for TSWA connections under fire conditions has been proposed. • The high-temperature component-based model can be applied to connections of various sizes. • The model can be directly used for the collapse analysis of 3-D frame structures under fire. • The prediction error of the high-temperature component-based model is within 3.2 %. • Compared to the solid element model, it reduces computational costs by at least 15 times. [ABSTRACT FROM AUTHOR]

Masonry arch bridges are highly vulnerable to floods and particularly to scour, as demonstrated by the many collapses that regularly occur in Europe. Scour levels that do not directly cause the collapse of a bridge may result in a significant reduction of their capability to withstand traffic loading. Thus, research on the performance of masonry arch bridges under combined scour and traffic loading, and their structural robustness, is of paramount importance. This study evaluates the behaviour of masonry arch bridges subjected to scour and traffic loading by analysing a representative case study with a three-dimensional finite element model developed in Abaqus according to a macro-modelling approach. Traffic load is selected in accordance with different code-based models, including those provided by Italian guidelines for safety assessment of existing bridges. The scouring process is imposed through the progressive removal of elements at the foundation level. Displacements and internal stress distributions for different bridge components are recorded and the capacity of the masonry bridge is estimated under increasing traffic load for different scour levels. Results are obtained in terms of both local and global response parameters to provide useful information on threshold levels for bridge safety and monitoring. The sensitivity of the bridge structural performance to material properties and traffic load position is also assessed. The study results can be useful to inform the decisions to be taken by bridge stakeholders (e.g. close bridge, limit traffic, keep bridge open) based on scour and/or structural response measurements. • Multi-hazard assessment of masonry arch bridges under scour and traffic loading. • Incorporation of traffic load models from Eurocode 1 and recent Italian guidelines. • Multi-scale assessment based on 3D FE macro-modelling and nonlinear static analyses. • Robustness to scour-induced damage based on residual traffic-load capacity. • Derivation of scour-induced damage thresholds for progressive collapse prevention. [ABSTRACT FROM AUTHOR]

The collapse resistance of prestressed precast concrete frames relies on the tie force of the strands, but the influence of the bond conditions and layout of the strands remains unclear. This study investigates these factors through push-down tests on four beam column substructures under penultimate column removal: one reinforced concrete specimen and three precast specimens (unbonded prestressed, bonded prestressed, and bonded with low-prestress parabolic profile). The results revealed that, compared to the reinforced concrete specimen, the precast specimens exhibited similar performance but were uniformly weaker under compressive arch action. Under catenary action, the precast specimens demonstrated significantly greater ultimate deformation and load-bearing capacity. The unbonded prestressed specimen failed due to wire rupture, impairing the flexural resistance of all its joints. In the bonded prestressed specimen, the bonded strand mitigated this issue but fractured prematurely. The bonded low-prestress specimen achieved the highest deformation and load-bearing capacity due to the enhanced deformation capacity of the low-prestress strand. • Push-down tests on bonded/unbonded prestressed precast concrete substructures. • The effects of strand profile and axial compression of side columns were analysed. • The resistance mechanisms of the precast substructures were revealed. • The comparison between the precast and monolithic substructures was involved. [ABSTRACT FROM AUTHOR]

A series of structural collapse failures over the last decades have triggered an increasing research interest to identify ways to prevent progressive collapse when structures are subjected to local damage due to foreseen or unforeseen actions. Strong nonlinearities, dynamic effects, and system behavior should be taken into account in progressive collapse analyses. In order to avoid time-consuming nonlinear dynamic analyses, approaches using a dynamic increase factor or the energy-based method to the static pushdown curve are widely adopted. However, in this article it is shown that reinforce concrete (RC) structures may be evaluated as safe according to a static analysis but essentially unsafe when considering a dynamic analysis due to the dynamic snap-through behavior. This phenomenon results in a dynamic sensitive failure mode (DSFM) that should be identified in relation to progressive collapse analyses. Comparing with the static situation, the dynamic instability may result in a much more brittle failure mode in the dynamic situation due to the dynamic effects. Hence, the structure becomes sensitive to the dynamic effects and this may further lead to danger of brittle failure, which should be prevented in practice. An efficient method is proposed to approximately determine the load-displacement region where the DSFM occurs. This region is designated as the DSFM window. A two-linear-spring system, a RC beam-column substructure, and a RC frame structure are employed to illustrate the DSFM and verify the proposed method. The results demonstrate that the proposed approach can effectively determine the DSFM window for RC structures subjected to column removal scenarios. • The phenomenon and mechanism of the dynamic sensitive failure mode (DSFM) during progressive collapse are investigated. • A method without conducting dynamic analyses for determining the DSFM window is proposed and verified. • The relationship between static instability and dynamic instability due to the dynamic snap-through behavior is studied. • The point of losing dynamic instability during progressive collapse is accurately identified by adopting the phase plan method. [ABSTRACT FROM AUTHOR]

A series of dynamic progressive collapse tests using the uniformly distributed load (UDL) was conducted, to analyze the robustness of three precast concrete (PC) beam–column assemblies using dry connections of top-and-seat angles (TSA-D), strengthened top-and-seat angles (STSA-D), and high-ductility reinforcement (DSTSA-D), under a middle column removal scenario. Finite element (FE) models were also developed to accurately simulate the collapse process. Based on the tests and FE models, comparative studies were conducted on dynamic and static collapse responses of the PC assemblies with identical configuration, loading regime, and boundary conditions. The results showed that: the horizontal reaction force developments were similar under dynamic and static collapse scenarios; under dynamic collapse scenarios, the initial stiffness of the PC assemblies increased due to the strain rate effect, while the peak vertical reaction forces under the compressive arch action (CAA) were smaller than those under static collapse scenarios, attributed to dynamic damage; under both dynamic and static collapse scenarios under UDL, the beam deformed in a downward convex curved shape, with local material deformation becoming more concentrated under dynamic collapse scenarios. An energy-based method for calculating dynamic collapse resistance was evaluated and revised: 1) the traditional method, which converts static responses from static analysis into dynamic responses was found to underestimate the resistance under small deformations due to neglecting the strain rate effect, and to overestimate ultimate resistance by ignoring dynamic damage; 2) by using dynamic vertical reaction forces instead, a more accurate prediction of the dynamic collapse resistance was achieved with a single dynamic collapse analysis. Additionally, dynamic amplification factors for the PC assemblies were calculated based on FE models and static test results providing basic knowledge in whole PC structural level research. • Dynamic progressive collapse tests under uniformly distributed load. • High-fidelity finite element models simulating dynamic collapse of PC assemblies. • Comparison between dynamic and static collapse responses of PC assemblies. • Dynamic collapse resistance considering strain rate effect and dynamic damage. • Dynamic amplification factors (DAF) for simplified collapse resisting design. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This study investigates the plastic seismic design of moment-resisting frames using concrete-filled steel tube columns (MRF-CFST) by utilizing the theory of plastic mechanism control (TPMC). Fundamentally, within the rigid-plastic analysis framework, the TPMC relies on a kinematic approach and an equilibrium curve for mechanisms. Employing this theory in the design of steel frames ensures the formation of a global collapse mechanism while deterring undesirable occurrences like a soft story. Using the TPMC, the kinematically admissible multiplier for seismic horizontal forces linked to the global mechanism is the minimum among all the kinematically admissible multipliers for other generic mechanisms. In this study, three methods were used to address the TPMC conditions: (a) Story-based method in which only the sum of the required plastic moments for columns in each story are unknown—identified as Design Method 1 (DM1); (b) Story-based method in which the sum of required plastic moments for both beams and columns in each story are unknown—denoted as Design Method 2 (DM2); and (c) Member-based method in which the demands for all members are unknown—denoted as Design Method 3 (DM3). A linear programming (LP) problem has been formulated for all design methods that incorporate the TPMC conditions as constraints. The DM1 used in previous studies serves as the conventional method for solving the TPMC conditions. A comparison between the three design methods has been conducted. The results show that DM3 stands out as the superior method, effectively minimizing weight and maximizing the strength of structures. Meanwhile, DM2, despite having fewer unknown parameters compared to DM3, yields the results that are comparable to DM3. To show the practical application of the proposed design methods, seismic design of three MRF-CFST with 5, 10, and 15 stories has been conducted. In order to verify the seismic design goal of achieving a global mechanism, both pushover analysis and incremental dynamic analyses (IDA) were utilized. The results illustrate the successful establishment of a global mechanism and the outstanding seismic performance of the designed structures. • This study proposes seismic plastic design of MRF-CFSTs using TPMC. • TPMC ensures a global collapse mechanism, avoiding undesirable plastic mechanisms. • Three design methods (DM1, DM2, DM3) are suggested to address TPMC conditions through linear programming. • Comparison shows that these methods minimize weight while maximizing structural strength. • Practical design examples are verified through pushover and IDA analyses. [ABSTRACT FROM AUTHOR]

Depending on the design, the connections of precast concrete (PC) structures can be susceptible to severe damage under large deformation. Consequently, PC structures may behave differently from cast-in-situ reinforced concrete (RC) structures under column loss scenarios. This study focuses on a class of PC structures that utilize splice sleeves (SSs) to assemble the precast components with integrated beam-column connections (IBCCs). This PC design can alleviate rebar congestion issues and minimize the need for post-cast concrete in the connection regions during assembly. The IBCCs are typically designed to mimic the behavior of corresponding RC connections under service loading conditions. However, the extent of structural emulation under column loss scenarios is not immediately clear. In this paper, the collapse behavior of PC structures with IBCCs under an internal column removal scenario is thoroughly assessed using experimental investigations and numerical analyses. Three PC subassemblages and one RC subassemblage are tested experimentally to provide experimental data for the calibration and validation of finite element (FE) models. The collapse behavior of full-span PC and RC subassemblages are next compared numerically under the internal column loss scenario, with an accompanying investigation on the influence of horizontal SSs. It is found that the PC subassemblages exhibit emulative collapse behavior as the RC subassemblage under internal column loss scenarios, provided that the horizontal SSs are located beyond the beam plastic region under the internal column loss scenario. To achieve the latter, a minimum distance of 0.15 L (L is clear beam span before column removal) is recommended for the positioning of horizontal SSs under the internal column loss scenario. Finally, it is shown that the fracture load and corresponding displacement can be enhanced with the incorporation of high ductility rebars. • A comprehensive investigation on the failure response of precast reinforced concrete structures with integrated beam-column connections (IBCC) under column loss. • Compare and contrast the performance of said precast concrete connections against monolithic concrete connections. • The influence of splice sleeve locations is elaborated. [ABSTRACT FROM AUTHOR]

Steel frame structures repaired after fire exposure exhibit markedly different collapse behavior, compared to their performance under ambient conditions, when subjected to extreme loads. This study investigates the progressive collapse resistance of steel frame structures with reduced beam section (RBS) connections in post-fire conditions, using ten beam-column substructures: one tested at room temperature and nine exposed to various fire conditions. Results show that fire exposure shifts the failure from the RBS to the beam-column connection, significantly impairing the RBS's ability to relocate the plastic hinge, especially at higher fire temperatures. Fire temperature significantly affects collapse resistance, especially above 600 °C, whereas fire duration has a comparatively smaller influence on deformation capacity, particularly at 800 °C. Elevated temperatures weaken tensile catenary action (TCA), with substructures exposed to 800 °C for 90 min failing to transition to the TCA-dominated stage. Numerical simulations show that for substructures exposed to 400 °C and 600 °C, collapse resistance increases with greater flange reduction length, while the relationship between collapse resistance and starting reduction distance follows a rise-and-fall pattern. At 800 °C, collapse resistance remains relatively consistent across different starting reduction distances, but increasing the reduction length initially enhances and then reduces resistance. Increasing the reduction depth to 30 mm significantly reduces both the flexural and tensile capacities of the RBS region, shifting the failure mode from the beam-column connection to the RBS region. • The progressive collapse resistance of steel frames with reduced beam section (RBS) connections post-fire is investigated. • The impact of high temperatures on load-displacement behavior and failure modes is analyzed. • The role of welded connections at beam-column interfaces in structural performance is highlighted. • Critical temperature thresholds affecting collapse resistance are identified. • Insights for improving design practices and safety measures in fire-exposed structures are provided. [ABSTRACT FROM AUTHOR]

This correction notice from the International Journal of Concrete Structures & Materials addresses an error in the biography section of an article titled "Progressive Collapse of Typical and Atypical Reinforced Concrete Framed Buildings." The original publication incorrectly listed the affiliation of one of the authors as Debre Markos University in Ethiopia, when it should have been University of Ottawa in Canada. The correction has been made to the article, and the correct information is now reflected. [Extracted from the article]