Large Structural Elements Research Articles

Avaliação do risco termo-tensional em elementos de concreto massa: uso de diagramas expeditos

Abstract Large structural elements have been commonly observed in increasingly tall buildings, employing mass concrete elements in their foundations. In these elements, the internal heat generated by the cement hydration can be decisive for the occurrence of pathological manifestations arising from the balance of stresses and also by delayed ettringite formation. This article presents a practical and expedited method, through diagrams, for a preliminary assessment of the thermo-tensional risk involved in the concreting of large-scale elements. For the development of thermal risk diagrams, the commercial software TSA-2D was used, where 64 numerical computational simulations were conducted, varying the parameters with the greatest influence on the concrete thermal phenomenon (minimum dimension of the structural element, cement content per cubic meter, cement hydration heat, concrete placement temperature, and ambient temperature). The result of this methodology, when compared to computational simulations and field monitoring in a specific case study, showed a good correlation, with the potential for application and reproducibility, considering the natural limitations of an expeditious practice that needs to be evaluated on a case-by-case basis, but which provide an important guideline in the early decision-making on-site. Furthermore, the maximum absolute error between the results of computational simulation and field monitoring was only 1.6%.

ПОЛЯ НАПРУЖЕНЬ ТА ГЕОЛОГІЧНА СТРУКТУРА ЗАХІДНОГО ЗАМИКАННЯ ГОРЛІВСЬКОЇ АНТИКЛІНАЛІ ДОНБАСУ ЧАСТИНА 2. ПОЛЯ НАПРУЖЕНЬ І ДЕФОРМАЦІЙ

Background. In tectonophysical studies, particular importance is placed on the mechanism of formation of large complex deformation structural elements, and the Horlivka anticline of the Donets Basin serves as such an example. Its importance lies not only in its complex structural composition and development mechanism but also in its potential impact on safe and efficient coal mining. This study aims to analyse the geological structure, stress and strain fields of the western closure of the Horlivka anticline that could be useful in forecasting geological factors for coal mining operations. Methods. The paleostress analysis was performed on the collected fault orientation and kinematic data using Gushchenko's kinematic method based on the analysis of tectonic displacement vectors along slickensides. Mesoregional stress field characteristics were reconstructed by statistical processing of local stereographic solutions. The relative age chronology and staging of tectonic stresses were studied using the stress monitoring method. The characteristics of the principal axes of the total strain field were processed using the GEOS software. Results. Mesoregional stress field is characterised by a subhorizontal NW–SE-oriented maximum principal stress axis and a subhorizontal NE–SW-oriented minimum principal stress axis. This stress regime is classified as a strike-slip regime and is the youngest one (Alpine orogeny) for the Donets Basin. The evolution of tectonic loading conditions of the studied structure is characterised by a deformation series of six stress regimes from the oldest (normal) to the youngest (strike-slip). Stretching axis of the strain ellipsoid is oriented NW and N–S, and shortening axis is oriented NE, nearly orthogonal to the anticline axis. Strike- and oblique-slip faulting regimes of the total strain field were determined for most of the study area, and the deformation has occurred under shear conditions, as indicated by the Lode–Nadai coefficient. Conclusions. A structural pattern of deformation elements, including a conjugate strike-slip fault system of the shear zone, a dome-shaped fold, and longitudinal thrusts in its limbs, may be interpreted as a single pattern of structural paragenesis developed by right-lateral displacements along the longitudinal strike-slip fault system within the Horlivka anticline paraxial part. Fragments of mutual symmetry between the stress and strain fields can be taken as evidence of their genetic relationship.

Traces of paleogeodynamic processes in the zone junctions of the Middle and Lower Kura depressions

The territory of Azerbaijan covers the southeastern part of the Greater Caucasus meganticlinorium, the northeastern parts of the mountain systems of the Lesser Caucasus and Talysh, i.e., basins of the Lower and Middle Kura, as well as the southwestern and western zones of the Middle and South Caspian depressions, respectively. The combination of these large structural elements determines the very complex tectonic structure of the territory of Azerbaijan, including the Middle and Lower Kura basins.
 The article presents the results of a study conducted to study the paleotectonic processes that took place in the Cenozoic in the junction zone of the Middle and Lower Kura depressions, according to modern (2017—2018) seismic survey data using the common depth point method. The geological structure of the constituent parts of these depressions is considered, and paleotectonic processes are described that played an important role in their formation and led to the divergence of the geological sections of these depressions in the interval from the end of the Cretaceous to the end of the Lower Pliocene. When comparing the seismic wave pattern representing the geological sections of the Middle and Lower Kura depressions, it becomes clear that the compensation of the volumes of sedimentary material is carried out by Pliocene terrigenous deposits in the Lower Kura and Paleogene sediments in the Middle Kura depressions. At the same time, here, the hypsometry of the Miocene-Maikop interval of the section differs by 1300—1500 m.
 The article presents the author’s positions on the post-Cretaceous tectonic processes of the evolutionary development of the geological structure of these basins in the zone of their junction, where the Mingacheir-Saatli-Talysh transverse Mesozoic uplift (Saatly-Geokchay zone of Mesozoic uplifts) occupies an important place.

Reliability of AMBT and CPT in testing the effectiveness of SCM to mitigate alkali–silica reaction of field concrete

This paper examines the reliability of the Australian Standards accelerated mortar bar test (AMBT) and concrete prism test (CPT), AS 1141.60.1 and 60.2, respectively, and the potential for extending these standard test methods to the determination of the type and dosage of supplementary cementitious materials (SCMs) required to mitigate deleterious alkali-silica reaction(ASR) in a similar manner to the corresponding ASTMC1567 and CSAA23.2-28A. Both AMBT and CPT have their strengths and limitations, however, their overwhelming value is in the availability of laboratory test results and their correlation with long-term performance (up to 20 years) of large concrete blocks and structural elements. Since Australia has no existing field exposure site, this paper uses reported data from CANMET’s and Ontario Hydro’s outdoor exposure sites in Ottawa and Kingston, respectively, in Canada and the 18-year exposure site data from the BRE site in the UK to demonstrate the efficacy of the AMBT and CPT approaches to evaluation of ASR reactivity and ASR mitigation using SCM blended cements. Good correlations are observed for moderately–reactive and highly reactive aggregates used with low-alkali cement and cement with alkali contents up to 0.9 % Na2Oeq. The assessment of reported research demonstrates that both AMBT and CPT have the capacity to predict the long–term performance of structural concrete. In addition, AMBT and 2-year CPT test results for eight Australian reactive aggregates are reported showing the influence of SCMs (fly ash and slag) on mitigation of expansion. Whilst both AMBT and CPT demonstrated their potential for assessing SCMs in mitigation of ASR, AMBT was found to be more conservative than CPT and higher SCM dosages were required to achieve a non-reactive classification. The accelerated test data reported coupled with the correlation of AMBT and CPT to the prediction of long term performance of concretes strongly supports the extension of the Australian test methods AS1141.60.1 and 60.2 for the assessment of ASR mitigation using SCMs.

METHODS OF ADAPTATION OF INDUSTRIAL ARCHITECTURE TO MODERN URBAN PLANNING CONDITIONS

The article explores the principles of renovation of industrial areas in the existing urban environment. The classification of elements of industrial territories by size, type is considered. A study of methods of aesthetic renovation of industrial areas is carried out. The basic principles of functional adaptation of objects of industrial architecture in urban space, taking into account urban planning conditions, are revealed. Industrial facilities in Ukraine over the past 50-70 years were built during the period of mass construction in conditions of cost savings, which sometimes led to the simplification of compositional solutions, monotony and vagueness of the architecture of production and auxiliary buildings of enterprises. Most of them were designed on the outskirts of the city, but with the growth of urban areas were surrounded by residential development. A certain order of spatial construction of territorial elements in the process of formation of production territories has been revealed. The smallest element of the production territory is the site of an industrial enterprise, the next largest structural element is an industrial node, that is, a group of enterprises located according to a single architectural and planning plan. Several mutually connected industrial hubs form an urban industrial area, which is connected to the city by a system of highways. Renovation of industrial buildings and structures in the image of the urban environment is proposed to be carried out taking into account the following parameters: urban planning; historical and cultural; material; natural-ecological. It is determined that the possibilities of further expansion of the urban area are reduced due to the need to preserve natural areas and limit the territorial growth of the city. The transformation of existing urban facilities can be divided into renovation with a change in the function of the territory, reconstruction, and partial reconstruction with elements of improvement. Change of functional purpose is carried out taking into account the adjacent territory and its planned development (microdistrict, district, etc., depending on the size of the industrial areas).

THREE-DIMENSIONAL DISPLACEMENT COMPATIBLE STRUT AND TIE METHOD FOR THREE-PILE CAPS SUBJECTED TO CONCENTRIC AXIAL LOADS

Pile caps are large structural elements that act as an interface between the superstructure and the pile foundation. The displacement Compatible Strut and Tie Method (C–STM) is an effective nonlinear modelling technique that is mainly used to simulate the behavior of structural reinforced concrete elements having considerable disturbed (D-) regions. Unlike STM, which considers only force equilibrium, C–STM considers displacement compatibility and constitutive material relationships as well. Recently, a three-dimensional (3D) C–STM was formulated and validated for the analysis of four-pile cap specimens of various shapes. In this study, the 3D C–STM is used to predict the complete load-deformation response of three-pile caps under concentric axial loads. The constitutive material relations for concrete and steel used in this study accounts for both concrete softening and tension stiffening. The overall load-deformation behavior simulated using the 3D C–STM agrees well with the experimental data. Moreover, the 3D C–STM also envisages the progression of nonlinear events leading up to the failure of three-pile cap specimen quite well.

THREE-DIMENSIONAL DISPLACEMENT COMPATIBLE STRUT AND TIE METHOD FOR THREE-PILE CAPS SUBJECTED TO CONCENTRIC AXIAL LOADS

Pile caps are large structural elements that act as an interface between the superstructure and the pile foundation. The displacement Compatible Strut and Tie Method (C–STM) is an effective nonlinear modelling technique that is mainly used to simulate the behavior of structural reinforced concrete elements having considerable disturbed (D-) regions. Unlike STM, which considers only force equilibrium, C–STM considers displacement compatibility and constitutive material relationships as well. Recently, a three-dimensional (3D) C–STM was formulated and validated for the analysis of four-pile cap specimens of various shapes. In this study, the 3D C–STM is used to predict the complete load-deformation response of three-pile caps under concentric axial loads. The constitutive material relations for concrete and steel used in this study accounts for both concrete softening and tension stiffening. The overall load-deformation behavior simulated using the 3D C–STM agrees well with the experimental data. Moreover, the 3D C–STM also envisages the progression of nonlinear events leading up to the failure of three-pile cap specimen quite well.

Geological structure and oil and gas potential of Domanik deposits in the central part of the Volga-Ural oil and gas basin

The paper describes the structure and depositional conditions of a domanicoid high-carbon formation (HCF) in the central part of the Volga-Ural oil and gas basin. The structure of the HCF depends on the structural relatedness and paleogeographic conditions of the Late Devonian period, where the time of maximum sea level standing within the basin led to deposition of high organic carbon content intervals. The structural-facies zonation of the HCF distribution area is associated with the zone of relatively deep-water depressions, the zone of slopes, highs and the shallow water shelf with numerous bioherm buildups. The boundaries of the zones were determined by the position of large structural elements of the Tatar and Bashkir arches and depressions of the Kama-Kinel system of troughs. These zones differ not only in the distribution of the thickness of HCF deposits, but also in the nature of the distribution of intervals of the section enriched in organic matter. The maximum number of interlayers enriched by organic matter of the siliceous-carbonate rocks is observed in the section of the Frasnian and Famennian deposits within the central part of the Kama-Kinel system of troughs. Numerous of oil shows from the HCF intervals indicate the potential for further study and spotting of promising areas for hard-to-recover hydrocarbon reserves exploration.

Application of the super element model with topology optimization method and genetic algorithm in the design of a large submillimeter telescope

The optimization of the elevation rotation structure (ERS) is one of the critical problems in the design of a large submillimeter telescope (LST). Here, combining the super element model with topology optimization method and genetic algorithm (SEMTOMGA) is proposed for the ERS design of an LST. The SEMTOMGA has three key steps: (1) the super element model is applied to condensing all the degrees of freedom of the large structure elements, which needs no topology optimization, except for the connecting nodes and the objective structure elements; (2) the topology method is applied to optimizing the objective structure; (3) based on the optimization results of the second step, the further whole structure optimization with multiobjective genetic algorithm(GA) is performed. The SEMTOMGA, which exploits the complementary merits of the super element model, topology optimization method, and GA, solves the problem of the ERS design effectively. As an application, a 60-m submillimeter telescope is designed and optimized by SEMTOMGA. The results have shown that the SEMTOMGA not only obtains a lightweight design of the ERS but also has sufficient stiffness. Moreover, the performance of the whole structure has been improved, and the residual half-path length errors of the main reflector have declined from 263.7 to 135.6 μm, which is about half of the original 263.7 μm of the initial design.

An Experimental Campaign on the Use of Natural Fibre-Reinforced Cementitious Matrixes

An experimental campaign has been carried out with the aim of using some natural materials as structural reinforcement. In a first stage, jute fabrics are investigated through uniaxial tensile tests. At this level, the chemical treatment with Ca(OH)2 tends to reduce the strength of the vegetal reinforcement. Nevertheless, this treatment seems to improve the bond between fabric and cementitious matrix. Indeed, the strength of FRCM reinforced with treated jute or flax are larger than those untreated. Similarly to the industrially produced reinforcement, as the bond strength increases, an increasing number of cracks can be observed in FRCM reinforced with vegetal fabrics. When large structural elements, such as existing brick walls, are reinforced by FRCM containing jute or flax, the strength and the fracture toughness is larger than those measured in plain walls. In particular, the increment of ductility is in direct proportion with the number of cracks developed by FRCM under uniaxial tension.

Development of modelling design tool for harpoon for active space debris removal

The level of debris in Earth orbit presents an increasing risk. Active debris removal, involving capture and deorbit of larger items, has been identified as important in controlling future debris population growth. One concept for capturing debris is a harpoon, with low post-penetration residual velocity being a key design requirement. Aluminium sandwich panels are common structural components on typical spacecraft and consequently a probable target structure. An ideal harpooning event is characterised with complete penetration of the sandwich panel and low harpoon residual (post penetration) velocity. This paper presents development of a numerical modelling tool for a harpoon design for active orbital debris removal. The ability to predict the ballistic limit of an aluminium sandwich panel with a honeycomb core representative of a large satellite structural element being the primary requirement for the modelling tool. The modelling approach was validated against the experimental results from normal and oblique impact tests performed for ogive and flat nose projectiles over a velocity range between 50 m/s to 120 m/s. The modelling was based on explicit finite element method, using the commercial LS-DYNA code. An element failure criterion was used to approximate material damage and failure. Sensitivity studies were performed to investigate the influence of model key features on the projectile exit velocity. The features with the strongest influence were the face sheet material model and the projectile-panel friction model. The projectile exist velocities observed in the experiments were used to select the final parameters used. The use of an element deletion criterion that incorporated the influence of stress triaxiality improved the agreement for the plate deformation behaviour between the numerical and experimental results. For the ogive nose projectile, the exit velocity agreed well with the experiments for the range of impact velocities and angles considered. For the flat nose projectile, the model overestimated the exit velocity. In the case of the normal impact this was due to the model's inability to capture the honeycomb crushing ahead of the projectile.

Methods for calculation and experimental evaluation of nucleation and development of the fatigue damages in tin based babbitt and babbitt lining of plain bearings

Fatigue damage to babbitt layers of plain bearings is often manifested during operation. The goal of the study is to develop a model for accumulation of the fatigue damage and destruction of antifriction materials and layers of plain bearings. A generalized fatigue diagram of tin-based babbitts including the main stages of fatigue damage and a diagram of the fatigue damage development in the antifriction layer of plain bearings are presented. The generalized model of V. V. Bolotin for damage accumulation and destruction is modified with regard to antifriction materials containing rather large structural elements. An explicit (direct) modeling of damage processes appeared possible for such materials. The model describes dissipated accumulation of microcracks (interpreted as destruction of the elements of the material structure), initiation and development of a system of short cracks, initiation and development of macro-cracks up to the limit state of the object. The model suggests discretization of the volume into sections with constant levels of complex stress state and discretization of the time axis into the intervals (blocks of loading cycles). The problem of identifying the parameters of a multistage model of the fatigue damage accumulation in the alloy is solved proceeding from the analysis of the results of testing babbitt specimens. We used the simplest optimization procedure, i.e., the method of deformable polyhedron. The parameters of the power function in the dependence of the rate of microdamage accumulation on the level of stresses are obtained. The parameters of the initiation and development of the crack system in the babbitt layer are obtained from the analysis of experimental results of studying steel-babbitt samples. The problem of calculating the durability of antifriction babbitt layers required the development of a new software. The program is examined by comparing calculated and experimental values of the durability of fatigue-tested bearing specimens forced against a rotating shaft by varying cyclic load. The calculated values of the durability match the experimental which confirms the performance of the calculated model.

Material testing and analysis of WAAM stainless steel

AbstractWire and arc additive manufacturing (WAAM) is a method of 3D printing that enables large structural elements to be built, with reasonable printing times and costs, making it well suited to applications in the construction industry. There is currently, however, limited information relating to the structural performance of WAAM material. Uncertainties include the basic mechanical properties, the degree of anisotropy and the influence of the as‐built geometry. Towards addressing this knowledge gap, a comprehensive series of tensile tests on coupons cut from WAAM stainless steel sheets was conducted and the results are presented and analysed herein. As‐built and machined coupons were tested to investigate the influence of the as‐built geometrical irregularity on the stress‐strain characteristics, while material anisotropy was explored by testing coupons produced at 0°, 45° and 90° to the printing layer orientation. Advanced non‐contact measurement techniques were employed to determine the geometric properties and deformation fields of the test specimens, while sophisticated analysis methods were used for post processing the resulting test data. The underlying material stress‐strain response, as determined from the tensile tests on the machined coupons, revealed a significant degree of anisotropy while the effective mechanical properties of the as‐built material were shown to be strongly dependent on the level of geometric variability arising from the printing process.

Hybrid testing of capacity designed RC structural walls for the determination of nonlinear seismic shear amplification

AbstractHybrid testing is an effective experimental method to study the dynamic behavior of structural elements under various types of loads. The hybrid testing method enables the seismic responses of large structural elements to be reproduced, such as the responses of reinforced concrete (RC) shear walls in a laboratory environment without needing to include the large masses typically encountered in multistory buildings. In this study, a test specimen corresponding to the base plastic hinge zone of an eight‐story RC structural wall was tested in a laboratory environment, whereas the remainder of the wall was modeled numerically to evaluate the seismic shear amplification due to nonlinear higher mode effects. A method is presented for controlling three degrees of freedom of a specimen with high axial stiffness and high lateral stiffness at the beginning of the test and the substantially reduced stiffness after cracking and yielding of the specimen. Because the duration of an uninterrupted test would have been very long, a method was used to stop and restart the test at will so that the whole test could be performed over several days. Seismic shear amplification due to nonlinear higher mode effects in a structural wall with yielding occurring at the base is measured for the first time in a hybrid test . The test results clearly present seismic shear amplification that is larger than building codes recommended values.

Evaluation of rheological models for concrete submitted to alkali-aggregate reaction based on numerical analysis of damping - free expansion

Abstract The Alkali-Aggregate Reaction (AAR) phenomenon in concrete structures is perceived via expansion and cracking, swelling of gel like material, causing damage and disruption in structural elements. Despite extensive standardization, AAR cases are still persistently occurring worldwide. The literature on susceptibility of concrete to AAR reported examples of false negative and positive results. Hence, long-term prediction is a problem still posing great challenge to engineers. The severity of AAR on the structural integrity can be mostly elucidated by the assessment of the historic of elastic properties. There is consensus that AAR causes decrease in the load capacity concrete, reflected by reduction of elasticity modulus due damage progresses. Non-destructive techniques are often used as first approach, as they can provide relatively fast assessment in situ as well as in large structural elements. Its data interpretation carries certain degree of complexity due intrinsic characteristic of many of these methods. This is the case of Ultrasonic Pulse Velocity (UPV), which have been considered to present several limitations for such purpose. This paper deals the potential use of the Longitudinal Resonance Frequency (LRF) method as tool to evaluate the elastic historic of AAR prone elements. The LRF possesses higher energy than UPV. Also, using modulation of frequency in input signal combined the test geometry, the LRF allow application to larger samples as well as to extract complementary information alongside the dynamic elastic modulus. This way, the LRF was applied to study concrete beams tested under controlled conditions for about 1.5 year. The independent variables to the tests are: time, frequency, aggregate type, cement content, alkali content and water to cement ratio. The dependent variables are: damping, loss factor and elasticity modulus. The analysis associate damage with vibration damping, confirming reduction of elasticity through damage with experimental validation and prediction of AAR under rheological model.

Damage detection in structural elements: Using optimization of fuzzified rules

Damage in forms of hairline cracks may occur during normal operations, deterioration or severe natural events. Due to the occurrence of cracks decreases lifetime of the product or system and in many large structural and machine elements, it may lead to dangerous catastrophic failure. There are various NDT methods which can be used for structural health monitoring but they take much down time and they are not cost effective also. Due to the above mentioned reasons, various researchers are getting attracted towards vibration based methods. For making the vibration based methods more efficient and effective, they can be combined with soft computing methods. In this research paper one of these types of method has been proposed. First the vibration features are collected from finite element analysis (FEA), then they are treated in the proposed method and the results are compared. Though FLS has already been used by several researchers, it has some loopholes. One of such shortcoming has been addressed in this paper while being used in the field of structural damage detection.

The deformation characteristics and flow field around knotless polyethylene netting based on fluid structure interaction (FSI) one-way coupling

Knotless polyethylene (PE) netting is widely used in fisheries because of its excellent hydrodynamic performance and low cost. Netting deformation and the surrounding flow field distribution play an important role in determining the hydrodynamic characteristics of netting in moving water. In order to investigate the effect of solidity ratio and attack angle on drag, netting deformation, and flow field distribution through the netting, a fluid-structure interaction (FSI) model based on a one-way coupling combining the shear stress turbulent (SST) k-omega model and the large deformation nonlinear structural finite element model was evaluated. Our results showed the difference between the parallel and normal drag forces found in the present numerical model and experimental flume tank data were 9.17% and 11.58%, respectively. The mean relative error in the inclined hydrodynamic drag for different flow velocities and attack angles was 8.35%, 6.69%, and 5.37% for the nettings 1, 2, and 3, respectively. These results show that the present numerical simulation based on FSI one-way coupling can be used to examine hydrodynamic forces on netting. The flow simulation results show that there is a noticeable flow velocity decrease through the netting and a rather large velocity reduction region downstream from the netting for different attack angles. These results reveal the existence of turbulent flow due to the netting wake. It was found that the equivalent stress and total deformation increase as the flow velocity increases and solidity ratio decreases.

Computational and experimental study of the stress state of the connecting rod of the opposed compressor to assess the probability of failure-free operation

Fatigue cracks in the piston heads of the connecting rods of opposed compressors can occasionally develop in service. A study of the loading of the connecting rods of the compressors operating in chemical production was carried out to assess the probability of their failure-free operation. Since the experimental study of stresses acting in large structural elements is rather difficult, the study of the stress state was carried out using computational methods with subsequent comparison of the results with the experimental data. When loading the connecting rod, there is an area affected by the distributed load and another area with a gap between the cylindrical surfaces where the contact pressure is absent. The forces acting on the boundary of the contact areas and the gap of the finger with the connecting rod bore are determined: the radial force N, tangential force Q and bending moment M. N and Q are considered functions of the contact angle α. Using numerical experiments, we determined the stresses in the zone from the angle α corresponding to the end of the contact zone to the angle of transition of the head in the shank of connecting rod in conditions of varied operational loads and gaps in the connecting rod — finger coupling. The values and character of changes in the loads affecting the crank mechanism of the compressor during operation are determined experimentally. The distribution of stresses in the sections of the connecting rod and the most loaded cross-sections are specified. the results of the numerical experiment are compared with the experimental data. Comparison of the results of numerical and field experiments has shown that the numerical experiment provides the similar assessment of the stress distribution, moreover, the numerical experiment allows us to estimate the simultaneous effect of both loads and gaps on the stress growth which is almost impossible to be determined by experimental studies.

Provision of the radiation safety for the decomissioning of the heavy-water research nuclear reactor NRC «Kurchatov Institute» – ITEP

The article provides a brief description of organizational and technical measures aimed at ensuring radiation safety during the decommissioning of the heavy-water research nuclear reactor of Institute for Theoretical and Experimental Physics after A.I. Alikhanov of National Research Centre «Kurchatov Institute». Information is provided on the history and features of the operation of the reactor, including parameters and characteristics that are significant for planning and conducting work. The peculiarities of legal regulation in the field of ensuring radiation safety are given; regulatory acts and rules accompanying other activities during decommissioning and directly related to radiation safety are also considered. The paper describes the work done in preparation for dismantling, the initial and current state of the installation, forthcoming work with examples of dismantled equipment. Methods for handling radioactive waste arising during decommissioning are considered, including methods for fragmentation of large structural elements (examples of mechanical devices are given), methods for sorting according to different specific activity (high activity, low activity), radionuclide composition and physical properties (solid, metallic, non-metallic, liquid). A special method for handling liquid radioactive waste is described, which includes the collection and temporary storage system. To assess the radiation situation at workplaces during the dismantling of the reactor structures, calculations of radiation transfer were carried out on the running and shutdown reactor, during which it was established that the expected dose to the personnel when performing activities on decommissioning of TBR is much lower than the limit values, established by regulatory documents. In accordance with the estimated radiation doses, rules and instructions for personnel were determined, including the procedure for using personal protective equipment, the necessary measures for surface decontamination, etc. Information is given on the procedure for radiation monitoring at all stages of dismantling and at the final stages of decommissioning including control of premises, personnel, equipment, waste of various types, atmospheric air.

Partitioned Strong Coupling of Discrete Elements with Large Deformation Structural Finite Elements to Model Impact on Highly Flexible Tension Structures

This article presents a staggered approach to couple the interaction of very flexible tension structures with large deformations, described with the finite element method (FEM), and objects undergoing large, complex, and arbitrary motions discretized with particle methods, in this case the discrete element method (DEM). The quantitative solution quality and convergence rate of this partitioned approach is highly time step dependent. Thus, the strong coupling approach is presented here, where the convergence is achieved in an iterative manner within each time step. This approach helps increase the time step size significantly, decreases the overall computational costs, and improves the numerical stability. Moreover, the proposed algorithm enables the application of two independent, standalone codes for simulating DEM and structural FEM as blackbox solvers. Systematic evaluations of the newly proposed iterative coupling scheme with respect to accuracy, robustness, and efficiency as well as cross comparisons between strong and weak FEM‐DEM coupling approaches are performed. Additionally, the approach is validated against the rest position of an impacting object, and further examples with objects impacting highly flexible protection structures are presented. Here, the protection nets are described with nonlinear structural finite elements and the impacting objects as DEM elements. To allow the interested reader to independently reproduce the results, detailed code and algorithm descriptions are included in the appendix.