Joint Elements Research Articles

How safe are partial squats after the anterior cruciate ligament reconstruction? A finite element analysis

BackgroundPartial squats are a part of many rehabilitation programs. Progress to deeper squats can only be performed through the partial squat position. However, squats safety, onset time, and rational depth are still controversial. Most previous studies have not considered the influence of posterior tibial slope (PTS) and anterolateral ligament (ALL) on the stress on the knee anatomical elements in partial squats. MethodsWe have created the new comprehensive knee computer models, which considered muscle exertions while weight bearing 75, 100, 125, and 150 kg in partial squats, included the ALL, two variants of PTS (5° and 13.9°), and two variants of anterior cruciate ligament (ACL) (a native 6 mm double-bundle ACL and an 8 mm single-bundle ACL graft). Using the finite element analysis, we have analyzed stresses in 14 anatomical elements in each model in partial squats (55° knee flexion and 10° anterior tibia tilt). ResultsPTS change from 5° to 13.9° in a partial squat increases stress 1.2–1.3 times on the native ACL and 1.3–1.4 times on the ALL. In the case of single-bundle ACL reconstruction, PTS growth from 5° to 13.9° results in stress increasing 1.2–1.3 times on the graft and 1.3–1.4 times on the ALL. Thus, increased PTS is a significant risk factor, especially in the early postoperative period. Weight-bearing predictably increases stress on the ACL, ALL, and other joint elements proportional to the weight growth.Patients with thinner grafts after the ACL reconstruction may already reach the risk level for graft rupture in a single load in partial squatting if they weigh 125 kg or more. The risk rises with increasing PTS angle or the patient's weight. Because of the reduction of the graft strength by six weeks after surgery by 27%, partial squats in six weeks are associated with forces that may exceed the maximal ACL load even in patients with 75 kg of weight without additional load. ConclusionIn the early postoperative period, partial squats can put the ACL graft at risk of failure. This risk is proportional to the patient's weight and PTS angle, and inversely proportional to the graft thickness. The choice of physical therapy strategies after ACL reconstruction, exercises, and their initiation timing is complex and cannot be standardized for all patients. Factors like the thickness of the graft, the method of fixation, the patient's weight, the ALL insufficiency, the PTS angle, and the patient's goals in the short and long term should be considered when planning the rehabilitation program.

Erratum for “Development of Nailed Wood Joint Element in ABAQUS” by Jian Xu and J. Daniel Dolan

Erratum for “Development of Nailed Wood Joint Element in ABAQUS” by Jian Xu and J. Daniel Dolan

CONCEPTUAL MODEL OF THE INFLUENCE OF LOW-FREQUENCY VIBRATION ON THE PROCESS OF RESTORATION OF JOINT MOBILITY AFTER IMMOBILIZATION

Disruption of joint mobility (contracture) is a frequent consequence of the treatment of injuries or orthopedic diseases, when the method of immobilization is used in the treatment process. One of the physiotherapeutic methods of preventing contractures and restoring joint mobility after long-term immobilization is vibration therapy. Objective. Create a concept of the effect of low-frequency vibration on joints and peri-articular tissues after immobilization. Methods. The work was performed using a meta-analysis of literature sourcesfrom scientific databases. The publications were analyzed, which considered the impact of vibration on joints or had data on its biologicalimpact on body tissues. Results. The physiological impact of vibration on the body is based on mechanical, physico-chemical and thermal effects. The expression of the physiological response depends on the frequency and amplitude of oscillations, conditions of conducting and localization. The concept is based on the features of the impact of vibration on the structural elements of limbs and joints. The vibration applied to the limb irritates mechanoreceptors, which send a signal to the central nervous system, and thanks to motoneurons, muscle contraction occurs, which affects peripheral blood flow and blood oxygenation. Accordingly, redox processes in tissues are launched. Micromovements caused by vibration contribute to the nutrition of cartilage and metabolism in the synovial fluid, improving the nutrition of periarticular tissues. This contributes to the recovery of both joint and adjacent tissues. Contraction of muscles through motoneurons gives impetus to a gradual increase in their motor activity and strength, restoration of nutrition and cartilage surface - to restoration of mobility. Conclusions. The created conceptual model of the effect of low-frequency vibration on joints with limited mobility due to immobilization takes into account tissue changes under its influence. The concept involves restoration of nutrition of tissues and muscles adjacent to the joint. It is vibration, due to the possibility of transmitting vibrational energy between tissues, that enables the processes of muscle contraction, which increase the blood supply and metabolism of the joint.

Cartilage diversification and modularity drove the evolution of the ancestral vertebrate head skeleton

The vertebrate head skeleton has evolved a myriad of forms since their divergence from invertebrate chordates. The connection between novel gene expression and cell types is therefore of importance in this process. The transformation of the jawed vertebrate (gnathostome) head skeleton from oral cirri to jointed jaw elements required a diversity of cartilages as well as changes in the patterning of these tissues. Although lampreys are a sister clade to gnathostomes, they display skeletal diversity with distinct gene expression and histologies, a useful model for addressing joint evolution. Specifically, the lamprey tissue known as mucocartilage has noted similarities with the jointed elements of the mandibular arch in jawed vertebrates. We thus asked whether the cells in lamprey mucocartilage and gnathostome joint tissue could be considered homologous. To do this, we characterized new genes that are involved in gnathostome joint formation and characterized the histochemical properties of lamprey skeletal types. We find that most of these genes are minimally found in mucocartilage and are likely later innovations, but we do identify new activity for gdf5/6/7b in both hyaline and mucocartilage, supporting its role as a chondrogenic regulator. Contrary to previous works, our histological assays do not find any perichondrial fibroblasts surrounding mucocartilage, suggesting that mucocartilage is non-skeletogenic tissue that is partially chondrified. Interestingly, we also identify new histochemical features of the lamprey otic capsule that diverge from normal hyaline. Paired with our new insights into lamprey mucocartilage, we propose a broader framework for skeletal evolution in which an ancestral soxD/E and gdf5/6/7 network directs mesenchyme along a spectrum of cartilage-like features.

Colocated MIMO Radar Waveform-Array Joint Optimization for Sparse Array.

Colocated multiple-input multiple-output (MIMO) radar can transmit a group of distinct waveforms via its colocated transmit antennas and the waveform diversity leads to several advantages in contrast to conventional phased-array radar. The performance depends highly on the degrees available, and element spacing can be deemed as another source of degrees of freedom. In this paper, we study the joint waveform and element spacing optimization problem. A joint waveform and array optimization criterion is proposed to match the transmit beampattern, the suppression range, and the angular sidelobes, under the constraints of minimal element spacing and total array aperture. Meanwhile, the effect of receive beamforming on suppressing mutual correlation between returns from different spatial directions is also incorporated into the optimization criterion. The optimization problem is solved by the sequential quadratic programming algorithm. Numerical results indicate that with more degrees of freedom from array spacings, colocated MIMO radar achieves a better transmit beampattern matching performance and a lower sidelobe level, compared with a fixed half-wavelength spaced array, but the benefits from additional degrees of freedom from array spacing optimization have a limit.

Seismic evaluation of composite moment frames subjected to near-fault ground motions

This paper investigates the seismic behavior of composite special moment frames (CSMF) under near-fault ground motions. For this purpose, two factors, response modification and deflection amplification are chosen. 3-, 9- and 20-story frames of SAC joint venture are modeled in OpenSees software. The nonlinear behavior of the panel zone was modeled using a 2D joint element and a tri-linear relation. FEMA p695 near-fault ground motions are applied in Incremental Dynamic Analysis (IDA). Ultimately, the obtained results are compared to the values recommended by ASCE provisions. The average results indicate that the ASCE provision can appropriately predict the response modification factor; however, in the case of deflection amplitude, IDA results may not show good agreement with ASCE/SEI 7 suggested value. Also, by comparing the results of composite special moment frames with steel moment frames from literature, it has been revealed that, unlike ductility, overstrength increases significantly when concrete filled tube columns are employed in special moment frames.

A SIMULATION-BASED APPROACH FOR KINEMATICS EVALUATION AND WORST-CASE DETERMINATION IN HIGHLY DEMANDING ACTIVITIES KNEE WEAR TESTING

Aim of this study was the development of a dynamic FE-framework to identify worst-case size combinations and kinematics in a virtual wear simulator setup covering five daily activities and high, dynamic loads.Two cruciate sacrificing knee designs (D1 & D2) were tested physically on a wear-testing machine prior the model development using a high demanding, daily activity protocol (HDA) [1]. A simplified FE-setup was generated, reduced to the 3D geometries of the assembly whereas the representation of the mechanical wear simulator conditions and the load transmission was achieved by joint elements. Inertial and other time-related effects of the physical situation were compensated by a system of spring- and damper elements.Using a time-series signal optimization approach on the anterior-posterior translation and the internal-external rotation results for each activity, 38 variable parameters were varied in between pre-defined limits in a semiautomatic workflow. For each design, two consecutive cycles of a single activity were analysed and the results of the second cycle were used for the optimization. Based on the determined values, a single set of averaged parameter settings was identified that covers all activity cycles sufficiently.A total of 1010 dynamic analyses were carried out in order to find a sharable set of parameter values.In this study, an efficient simulation workflow for design evaluation was developed. Therefore, a HDA wear-testing machine was simplified to boundary conditions and stabilizing elements, using a single set of parameters for all activities. The calculated kinematics were in a comparable range to the machine output. Further applications of the method were found in systematic analyses of entire implant systems to achieve consistent kinematics over the size compatibility range in the design process of new implant systems.

Osteoarthritis - epidemiology, risk factors and methods of conservative treatment

Osteoarthritis is one of the most common chronic diseases, which is characterized by the destruction of joint cartilage and leads to changes in the structure of other joint elements, the formation of osteophytes and the development of inflammation in the immediate area. Precise assessment of the frequency and distribution of the disease in the population may be difficult due to the inconsistent definition of the disease and the selected diagnostic criteria, but it is estimated that it may occur in up to 60% of the elderly population, more often in women than men. There are many documented risk factors for the occurrence of the disease, such as age or genetic predisposition, but the modifiable ones deserve special attention. Recently, great emphasis in the context of osteoarthritis has been put on the fight against obesity, which not only increases the mechanical load on the joints, but also intensifies the generalized inflammation in the cartilage and its surroundings. This is one of the reasons why non-pharmacological therapy, i.e. patient education and physiotherapy, is a basic element of management, both alone and in combination with pharmacological treatment. The most common drugs used in OA are non-opioid analgesics from the lowest level of the analgesic ladder - mainly NSAIDs, and their proven effectiveness is consistent with the current concept of inflammation as the main pathogenetic factor. As a second-line treatment, injections of glucocorticoids, hyaluronic acid (HA) and platelet-rich plasma (PRP) directly into the joint may be considered. Unfortunately, most randomized studies show that the administration of steroids is effective, but the effects are relatively short-lived, up to a few weeks, while more reliable scientific evidence is needed to confirm the effectiveness of other substances.

The important role of stiffnesses values of circular joints on the stress state developed in the tunnel segmental lining

Under the application of the fluctuating Tunnel Boring Machine (TBM) jack thrust and the non-uniformly distributed total pressure of the slurry around the lining, the bending and the shear deformation occur on the segmental lining along the longitudinal direction, which cause a stress concentration and increase the damage risk of the segmental tunnel lining. The analysis of the circular joint stiffness is a critical step during the evaluation of the stress state of the segmental lining so as to decrease the associated risk of damage. In order to investigate the lining rings and the circular joint separately, an integrated numerical model which is composed of segment elements and joint elements was developed. Furthermore, stiffness equations for describing in the detail the circular joint behaviour of the tunnel segmental lining are derived. The new stiffness equation of the circular joint is also used to analyse the segment lining behaviour based on a well-known indoor test result by the scientific literature, and satisfactory results were obtained. A simplified estimation of the bending stiffness of the circular joint based on the Boltzmann equation is then suggested in order to obtain quickly its calculation. Finally, based on a specific numerical model, the calculated joint stiffnesses are adopted to analyse the vertical displacement of a real case (The Ningbo metro tunnel in China). Through a developed sensitivity analysis, some useful suggestions are proposed to reduce the damage risk of the segmental lining.

Optimization of S-N curve fitting based on neighborhood rough set reduction with improved firefly algorithm

S-N curve fatigue samples of titanium alloy welded joints have such a comparatively significant scatter, that results in the issue that the fatigue life prediction accuracy is not optimal. In this work, the titanium alloy welded joints' fatigue data is used as analysis data, and the neighborhood rough set reduction with improved firefly algorithm efficient method of fitting stress-life curves is set forth. The welded joint's fatigue decision system is built with fatigue data. The continuous iteration of the firefly algorithm is used as the search strategy, the neighborhood rough set is adopted to decrease attributes, and the major deciding elements of welded joints' fatigue life is identified. The fatigue characteristic domains are divided based on the neighborhood rough set reduction with improved firefly algorithm's key factor set, and the S-N curves can then be fitted to each domain individually. According to the goodness-of-fit analysis, the proposed approach can improve fatigue life accuracy and reduce sample scattering from fatigue.

Safety of Steel Arch Support Operation During Rock Bursts Under Explosive Atmosphere Conditions

Abstract Methane and coal dust explosions are among the most common causes of disasters in hard coal mining. Therefore, it is important for occupational safety in hard coal mines operating under methane and coal dust explosion hazards to identify possible ignition sources, whether due to natural or technical factors. One technical source of ignition can be mechanical sparks generated during operation of mechanical equipment and high surface temperatures of equipment components during operation. This paper presents the methodology and results of thermal imaging and strength testing of roadway support elements under dynamic loading. The goal of the tests was to identify the potential explosive atmosphere ignition sources during the operation of the support under the conditions of rock bursts. The scope of testing encompassed the temperature measurements by means of thermal camera of friction prop and yielding support frame sliding joint elements at yield under dynamic impact loading (simulating a burst). Significant joint element heating and mechanical sparking was observed during the testing of arching yielding support frame sliding joints and straight friction prop joints as a result of friction at yield. Some of the aspects defined in standard PN-EN ISO80079-36:2016 include the maximum temperature T max =150°C for a surface that can accumulate a layer of coal dust. Tests of the friction joints have shown that during impact loading, numerous mechanical sparks are produced at the friction joints of sections of the steel prop, with the surface temperature of the sections starting from 169.6°C and reaching up to 234.1°C. During tests it was also to determined emissivites of the tested sliding joints constructed from V29-V32 secrions depending on corrosion products which consist in range 0.842–0.873. Such a high temperature can initiate an explosive mixture consisting of methane, air and coal dust.

Expression of cannabinoid (CB1 and CB2) and cannabinoid-related receptors (TRPV1, GPR55, and PPARα) in the synovial membrane of the horse metacarpophalangeal joint.

The metacarpophalangeal joint undergoes enormous loading during locomotion and can therefore often become inflamed, potentially resulting in osteoarthritis (OA). There are studies indicating that the endocannabinoid system (ECS) modulates synovium homeostasis, and could be a promising target for OA therapy. Some cannabinoid receptors, which modulate proliferative and secretory responses in joint inflammation, have been functionally identified in human and animal synovial cells. To characterize the cellular distribution of the cannabinoid receptors 1 (CB1R) and 2 (CB2R), and the cannabinoid-related receptors transient receptor potential vanilloid type 1 (TRPV1), G protein-related receptor 55 (GPR55) and peroxisome proliferator-activated receptor alpha (PPARα) in the synovial membrane of the metacarpophalangeal joint of the horse. The dorsal synovial membranes of 14 equine metacarpophalangeal joints were collected post-mortem from an abattoir. The dorsal synovial membranes of 14 equine metacarpophalangeal joints were collected post-mortem from an abattoir. The expression of the CB1R, CB2R, TRPV1, GPR55, and PPARα in synovial tissues was studied using qualitative and quantitative immunofluorescence, and quantitative real-time reverse transcriptase PCR (qRT-PCR). Macrophage-like (MLS) and fibroblast-like (FLS) synoviocytes were identified by means of antibodies directed against IBA1 and vimentin, respectively. Both the mRNA and protein expression of the CB2R, TRPV1, GPR55, and PPARα were found in the synoviocytes and blood vessels of the metacarpophalangeal joints. The synoviocytes expressed the mRNA and protein of the CB1R in some of the horses investigated, but not in all. Given the expression of the CB1R, CB2R, TRPV1, GPR55, and PPARα in the synovial elements of the metacarpophalangeal joint, these findings encouraged the development of new studies supporting the use of molecules acting on these receptors to reduce the inflammation during joint inflammation in the horse.

A minimal model for the influence of equilibrium positions on brake squeal

The phenomenon brake squeal has been an ongoing topic for decades, both in the automotive industry and in science. Although there is agreement on the excitation mechanism of brake squeal, namely self-excitation due to frictional forces between the disk and the pad, in the subject of squeal it is very complex to discover all relevant effects and to take them into account. Several of these problems are related to nonlinearities, for example, in the contact between pad and disk or drum or in the behavior of the brake pad material. One of these nonlinear effects, which has been almost completely neglected so far, is that the brake can engage, mainly due to the bushing and joint elements within the brake, different equilibrium positions. This in fact has serious influence on the noise behavior as shown in experimental studies. For example, it is observed in experiments that, despite identical operating parameters, squeal sometimes occurs and sometimes not. In initial experimental studies, this could be related to the engaged equilibrium position. Following these experimental studies, the present paper introduces a minimal model by extending the well-known minimal model by Hoffmann et al. by corresponding elements and nonlinearities allowing the system to engage different equilibrium positions. As will be presented, the stability behavior strongly depends on the engaged equilibrium position. Therefore, the minimal model represents the key experimentally observed issues. Additionally, a limit cycle behavior can also be observed.

An improved numerical model for locomotive tensegrity systems based on vector form intrinsic finite element

Locomotive robot based on tensegrity has recently drawn much attention due to its lightweight and flexibility. This article presents an improved numerical model for locomotive tensegrities. The previously used bar element for struts is replaced by beam element, and rigid joint element is used to consider more details of the tendon–strut connections. The vector form intrinsic finite element (VFIFE) method is adopted to formulate the numerical model and carry out the simulation. The improvement of the proposed model on the prediction of feasible rolling gaits is quantitatively verified by experiments on a six-strut locomotive tensegrity. Mann–Whitney U test is adopted, and the p value between the experimental success rates of the gait primitives generated by the improved model and the rates of the gait primitives generated by the previous model is [Formula: see text]. It is shown that the improved model is more consistent with the experiment by considering the details of the tendon–strut connection.

DEGENERATIVE ARTICULAR CARTILAGE DISEASE, OSTEOARTHROSIS

Introduction: Osteoarthrosis (OA), degenerative articular cartilage disease is a chronic inflammatory arthropathy involving joint elements (subchondral bone, synovial membrane, hyaline cartilage and others). It is due to a disorder in the regulation between degradation and synthesis of the extracellular matrix of cartilage, involving bone and synovial membrane in a biochemical process mediated by growth factors and cytokines which, in turn, intervene in the course of bone remodeling and joint destruction. Objective: to detail the current information related to osteoarthrosis, description, etiology, classification, imaging classification, management and current treatments. Methodology: a total of 52 articles were analyzed in this review, including review and original articles, as well as clinical cases, of which 38 bibliographies were used because the other articles were not relevant for this study. The sources of information were PubMed, Google Scholar and Cochrane; the terms used to search for information in Spanish, Portuguese and English were: arthrosis, osteoartrose, bones, osteoartrosis, articular cartilage. Results: The prevalence of osteoarthrosis increases directly with age 25-35 years 0.1 % 35-65 years 30 % and over 80 years 80-100 %. An improvement of pain and sensitivity is observed with local treatment with capsaicin. Paracetamol can be considered as the basic analgesic in the treatment of most chronic osteoarticular pain in doses of 1 gram four times/day. Opioids have an analgesic effect that almost completely eliminates all kinds of pain regardless of its intensity or site of affection. Short-term and long-term parenteral corticosteroid use is effective in controlling pain and stiffness. Systemic use of corticosteroids in OA is not warranted and only intra-articular injections are advised. Diacerein decreases IL 1Beta production in cartilage as well as nitric oxide levels by antagonizing the catabolic process and stimulates the anabolic process of cartilage. Chondroitin sulfate does not present a clinically relevant effect on joint pain or joint space reduction. Conclusions: osteoarthritis should be considered as a chronic, irreversible and progressive lesion. There are factors that aggravate its prognosis. Many measures are recommended to the patient and his family, especially if it is an elderly patient, in order to avoid the progression of joint damage. Surgical treatment is reserved for patients with severe pain or marked deformity, which occurs in advanced OA. Among the most frequently used procedures are: valgus osteotomy of the proximal tibia, arthroplasty, arthrodesis and amniotic membrane implantation. Bone tissue regenerative currents using tetracyclines that prevent the activation of metalloproteases, autologous chondrocyte implants, hypoxia inducible factor (HIF-1/2a), parathyroid hormone that stimulates chondrocyte multiplication and the use of in situ stem cells, cartilage regeneration and a better understanding of the developmental protein ancestor of osteogenesis, will be part of the medical management protocol, being a promising therapy for future therapy. KEY WORDS: Osteoarthrosis, osteoartrose, bones, osteoartrosis, articular cartilage.

Classification system for inter-modular connections in non-sway corner-supported steel modular buildings

The main difference between the structural design of corner-supported modular buildings with their conventional counterparts lies in the design of their connections. This is because of the different configurations and lack of continuity in joints, resulting in a complex boundary condition for predicting the behaviour of these structures. Because of the ever-increasing demand for building construction using these systems, and a relatively large variety of modular connection types being used in practice, it is of paramount importance to provide criteria ensuring the safety and predictability of the stability performance of these structures. This paper proposes a classification system for horizontal and vertical inter-connections in non-sway frames in terms of stiffness and strength for their rotational components. From the stiffness point of view, the boundaries between rigid and semi-rigid zones are identified and formulated with respect to the variation of relative bending stiffness ratios of elements in joints, such as beams, columns, and connections. Two performance criteria are considered for the classification of inter-modular connections in non-sway corner-supported modular buildings: (i) buckling criterion, where general governing equations for buckling analysis are derived for an idealised and simplified model of braced frame corner-supported modular steel building to classify inter-connections based on the ultimate limit state; and (ii) displacement/drift criterion, for which parametric modelling is conducted using OpenSees for classification based on serviceability limit state. From the strength point of view, the inter-connections are classified into three categories namely, fully-strength, partially-strength, and nominally-pinned based on their ultimate moment capacity. The results are then verified in a case study through the use of data for some existing modular inter-connections, from the literature. Finally, based on the findings of this study, some recommendations for the design of inter-modular connections in non-sway corner-supported modular buildings are presented.

Numerical analysis of traditional Chinese timber structure: Simplified finite element model and composite elements of joints

Mortise-tenon (M-T) joint, column foot joint, and Dou-Gong joint play a key role in the seismic behavior and energy dissipation of traditional timber structures. To simplify the modeling process and predict accurately the hysteretic behaviors of traditional timber joints as well as the global seismic responses of traditional timber structures, three types of composite elements, which were composed of varying non-linear one-dimensional spring elements available in the ANSYS finite element (FE) software, were proposed to characterize the hysteretic performance of the M-T joint, the column foot joint, and the Dou-Gong joint, respectively. The beam element was used for simulating the timber components with large size and not easily damaged. The parameters of the composite elements were identified from the simplified hysteretic model or test hysteretic curve of each type of joint. The simplified FE models of the M-T joint, M-T jointed timber frame, column foot joint, and Dou-Gong joint were developed, and verified using the cyclic loading tests of joints, respectively. Based on the validated composite elements and simplified FE models of varying joints, the three-dimensional simplified bar system FE model of a 1/3.52-scaled palace-style ancient timber structures was established using the ANSYS, and also validated using the shaking table tests, in terms of its dynamic characteristics and responses. Good agreements between the model predictions and test results were observed. Additionally, parametric analyses were performed, while revealing and quantifying the effects of performance degradation for the M-T joint, column foot joint, and Dou-Gong joint on the dynamic responses to the structure. It is found that the damage to the Dou-Gong joint had little effect on the maximum story drift of column frame layer, however, the damage to the M-T joint and column foot joint would significantly increase the maximum story drift of column frame layer. When the damage degree of the M-T joint, Dou-Gong joint, and column foot joint in the structure was up to 60%, the maximum story drift ratios of column frame layer were close to 1/48, 1/50, and 1/39, respectively, the maximum story drift ratios of Dou-Gong layer were approximately 1/164, 1/98, and 1/125, respectively.

Differences in the Microstructures and Tensile Properties of Each Zone of Inertia Friction Welded Joints of TA19 Titanium Alloy

TA19 titanium alloy is a novel medium-temperature, high-strength titanium alloy widely used in the aerospace industry, and its welding performance is very important for the manufacturing of structural parts. In this study, TA19 titanium alloy was connected by inertial friction welding (IFW). After welding, the microstructural and alloying elements of the IFW joints were investigated; the results showed that the microstructures of each zone of the IFW joint were different, and accumulations of the β-stable element Mo were only observed in the base metal (BM) and the heat-affected zone (HAZ). Tensile tests were performed using specially designed specimens with circular grooves to obtain the axial mechanical properties of different zones of IFW joints. The stress–strain curves and tensile fractures of the different specimens were analyzed; the results showed that the tensile strength of the welded joint increased, but the plasticity decreased from BM to WZ.

НЕСУЩАЯ СПОСОБНОСТЬ И ДЕФОРМАТИВНОСТЬ СВАРНЫХ ВЕРТИКАЛЬНЫХ СТЫКОВ КРУПНОПАНЕЛЬНЫХ ЗДАНИЙ НА ЗАКЛАДНЫХ ДЕТАЛЯХ

Analysis of the research results presented in the scientific and technical literature showed the absence of data about the operation of welded vertical joints of large-panel buildings on embedded parts with connecting elements in the form of bent and rolled angle bars. In order to determine the technical parameters necessary for the calculation and design of large-panel buildings, experimental researches of the operation of welded vertical joints on embedded parts with connecting elements in the form of bent and rolled corners under the action of tensile and shear forces were carried out. The static load was applied in stages until the destruction of the prototypes. During the experimental researches, the displacements in the place of bending of the connecting elements of the prototypes were recorded. On the basis of the experimental data obtained, the values of compliance of the connecting elements of the vertical joint on embedded parts were determined. Correction coefficients for the correct definition the compliance of connecting elements in the form of rolled and bent angle bars of a vertical joint on embedded parts are calculated and proposed. A different nature of deformation and destruction of welded vertical joints on embedded parts with connecting elements in the form of rolled and bent angle bars with the same geometric dimensions under the action of tensile and shear forces on the joints is revealed.

Analysis of the functional state of flanged joints

This article discusses related aspects of the formation and provision of the functional quality of the load-bearing elements of frame systems. The subject of the study is the analysis of the state of steel structures with the possible manifestation of violations of the shape of structural elements in flanged joints. The formation and provision of the functional qualities of metal structures and their connections is carried out at all main stages of the life cycle. The scientific hypothesis consists in the assumption that the analysis of the parameters of the stress-strain state in metal structures, characterized by the presence of deviations from the established indicators of functional quality, contributes to an accurate assessment of the parameters of the state and service life. The conditions and circumstances characterizing the possibility of loss of functional qualities of flanged joints of steel structures are determined. A block diagram of the analysis of risks associated with manifestations of the shrinkage distortion of flanges, which reduce the operational reliability of steel structures, has been developed. It is advisable to supplement the methodological basis for the development of design solutions for steel structure units with a forecast (modeling) of the state and operational suitability of a flange connection in the presence of shrinkage distortion of flanges. The results of the analysis of possible states of loss of bearing capacity using a predictive model will contribute to the development of rational parameters of labor intensity and material consumption of manufacturing flanges of steel structures.