Loss Of Stiffness Research Articles

Foreword to the special issue on new developments in structural stability.

Foreword to the special issue on new developments in structural stability.

Data-driven approach to structural analysis of shaft steelwork under corrosion

Considering the importance of shaft steelworks for the continuity of mining and personnel safety, they are subject to regular and demanding maintenance inspections and corroded member replacements. However, design procedures disregard many important factors because of the lack of accurate structural analysis models for shaft steelwork constructions and operational conditions. Thus, common industrial practices of overdesigning and corroded member replacement lack objective design criteria, while the available maintenance monitoring data are highly underutilized. In this study, the actual load effects and structural resistance of shaft guide tracks were investigated by conducting field and laboratory tests on the guiding forces, carrying capacity, connection stiffness, and corrosion loss. The findings were augmented using finite element and surrogate model simulations and stochastic modeling. The proposed methodology incorporates guiding forces and corrosion-loss maintenance data and offers an innovative solution for shaft-guide structural analysis, reflecting the semi-rigid connections, actual position of the force application point, dynamic amplification effect, local buckling, material strength uncertainty, and random corrosion loss. This novel methodology is consistent with sustainable engineering principles and provides a foundation for modern reliability analysis of shaft steelwork.

Fatigue life analysis and damage evaluation in glass fiber reinforced composite materials based on recycled polyethylene terephthalate

Viability of recycling polyethylene terephthalate (PET) can be enhanced by increasing its usage as a matrix material in manufacturing of composite materials. Structural applications of composite materials almost always involve fatigue loading and evaluation of fatigue behaviour is essential to explore the full potential of composite materials based on recycled PET. With an aim to increase the acceptability of recycled PET based resins, fatigue performance of glass fiber reinforced composite materials based on unsaturated polyester resin derived from recycled PET (rPET-UPR) has been evaluated in the present research. Glass fiber composites laminates of stacking sequence [0/(±45)2/0]T have been fabricated using vacuum infusion process. Fatigue tests were performed at the stress ratio of 0.1, where the stress level varied from 40%–80% of the ultimate tensile strength (UTS). The results of fatigue tests show that the fatigue lives of composites based on rPET-UPR were lower as compared to virgin polyester matrix composites. However, Statistical analysis of the fatigue life data using two parameter Weibull distribution, established that there is no deleterious effect on the scatter observed in fatigue lives of these composites, as compared to composites based on virgin polyester resin. Due to higher degradation of rPET-UPR matrix as well as weak interfacial properties, 13% higher self generated temperature was observed during fatigue loading in comparison to virgin resin based composite materials. A three phase stiffness degradation curve has been observed for these composite materials indicating stiffness loss in the range of 20%–35% till the time of failure, which correlates well with the experimental damage observations. A nonuniform and rapid damage growth was observed at high-stress levels, whereas a more uniform damage zone was observed at the low-stress levels.

“Wood-nacre”: Development of a Bio-inspired Wood-Based Composite for Beam and 3D-Surface Elements with Improved Failure Mechanisms

Following the natural structure of the nacre, the material studied consists of a multitude of hexagonal tiles that are glued together in an offset manner with a ductile adhesive. This so-called “wood nacre” consists of macroscopic tiles of birch wood veneer with a thickness of 0.8 mm and a size of 20 or 10 mm in diameter in order to mimic the aragonite tiles and the ductile PUR-adhesive corresponds to the layers of collagen in between. E-modulus (MOE), bending strength (MOR) and impact bending strength of the samples were determined and compared with reference samples of birch laminated wood. The hierarchical layered structure of the tiles does not cause any relevant loss in stiffness. Like nacre, “wood nacre” also shows tough fracture behaviour and a high homogenization effect. However, strain hardening and high fracture toughness of the natural model could not be fully achieved. The reason for this is the insufficient ratio between the strength and stiffness of the veneer layers and the adhesive. By adjusting the size of the tiles, increasing the strength and surface roughness of the veneers, e.g. by densification, and using more ductile adhesives that can be applied in smaller layer thicknesses, it should be possible to better reproduce the natural ratios of nacre and thus achieve a significant improvement in the material properties of “wood nacre”. In addition to the mechanical properties, the high potential of the new material lies in the possibility of producing 3D shell-shaped elements for lightweight wood hybrid construction.

Evaluation of the Mechanical Properties of Lightweight Foamed Concrete at Varying Elevated Temperatures

Lightweight foamed concrete (LFC) made from cementitious materials with air pores entrapped in the matrix by mechanically entrained foam in the mortar slurry has several economic and environmental benefits. Most recently, LFC has been heralded as the next generation of lightweight construction industry concrete because of its versatility and technological advancements. Owing to its many desirable qualities, including low density, low cost, low thermal conductivity, low dimensional change, amazing load-bearing capacity, great workability, and low weight, it is considered an adaptable and flexible construction material. Given that LFC is a brittle building material and since fire is among the most frequent catastrophes to affect structures, it is crucial to consider the structural performance of LFC subjected to high temperatures. Hence, this experiment attempts to ascertain the effect of varying elevated temperatures on the LFC’s strength properties. Three LFC densities of 500, 1000 and 1500 kg/m3 were prepared. The LFC specimens were exposed to predetermined ambient and elevated temperatures of 20, 100, 200, 300, 400, 500, 600, 700 and 800 °C, and the LFC samples were assessed for porosity, compressive and flexural strengths. The outcomes of this investigation showed that, regardless of density, the loss of LFC stiffness exposed to elevated temperatures happened primarily after 90 °C. This shows that the underlying process triggering stiffness loss is internal cracking, that transpires when water grows and dissolves from a porous medium. Lowering the LFC dry density diminishes its strength and rigidity. The LFC-normalized strength and stiffness–temperature relationships of various dry densities, on the other hand, are very comparable. From ambient temperature up until 400 °C, all densities exhibit a moderate and constant loss in strength and stiffness. Nevertheless, the decline is faster up to 600 °C or 800 °C, at which point it loses its ability to support any given weight. This study emphasized the necessity for more study and codes’ provisions that take into consideration various LFC constituent types and cutting-edge construction material technologies.

Mechanics and optimization of undulatory locomotion in different environments, tuning geometry, stiffness, damping and frictional anisotropy.

One of the oldest yet most common modalities of locomotion known among limbless animals is undulatory, also recognized for its stability compared to legged locomotion. Multiple forms of active mechanisms, e.g. active gait control, and passive mechanisms, e.g. body morphology and material properties, have adapted to different environments. The current research explores the passive role of body stiffness and internal losses in meeting terrain requirements. Furthermore, it addresses the influence of the environment on the resultant gait and how the interplay between various environments and body properties can lead to different speeds. We modelled undulatory locomotion in a dry friction environment where frictional anisotropy determines propulsion. We found that the body stiffness, the moment of inertia, the dry frictional coefficient ratio between normal and tangential frictional constants, and the internal damping of the body play an essential role in optimizing speed and animal adaptability to external conditions. Furthermore, we demonstrate that various known gaits like swimming, crawling and polychaete-like locomotion are achieved as a result of the interaction between body and environment parameters. Moreover, we validated the model by retrieving a corn snake's speed using data from the literature. This study demonstrates that the dependence between morphology, body material properties and environment can be exploited to design long-segmented robots to perform in specialized situations.

Performance analysis of vibration-based damage indicators under low-modal information structures

There exists a wide range of frequency-based damage indicators, which have been verified under high-modal information structures. Nonetheless, their performance and behaviour under less advantageous conditions remain unanswered. In this work, an original methodology is presented, combining an analysis of the damage detection and a statistical method to assess the damage quantification of each indicator. Furthermore, this study is validated using experimental data from three increasingly complex structures due to the limited modal information. The approach calculates different damage features based on the vibration responses of the structures. Subsequently, the prediction obtained from damage features is compared with the actual condition of the structure. The performance of each damage indicator is quantified using the Area under the Curve. In parallel, a correlation between damage indicator response and stiffness loss is conducted to understand the damage severity quantification of indicators. In addition, the minimum detectable damages are calculated and reported for different confidence intervals. The results showed that matrix-based indicators present advantages over other documented methods. Moreover, the influence of noise and modal information was studied, demonstrating that their diminishing effects do not equally impact all damage indicators. The findings of this work give insights into how each damage indicator performs in different structures and conditions. Finally, this work proposes an objective methodology to compare damage detection strategies.

Experimental investigation of a sustainable reinforced cantilever concrete slab exposed to different intensity of temperatures

Recently, several scientists have paid special attention to how high temperatures alter the chemical and physical features of reinforced concrete structural members such as slabs. Cantilever concrete slabs, the impact of cooling regimes, the influence of the crack created during heating, and the residual strength of concrete slabs subjected to extreme temperatures were very limitedly investigated in the reviewed literature. Therefore, this research investigated the behavior of cantilever concrete slabs subjected to elevated temperatures and cooling regimes. Two different slab thicknesses (100 mm and 150 mm), various intensity of temperature (200 °C, 300 °C, 400 °C and 500 °C) and two different cooling conditions (Air and Quench cooling) were examined. The observations made during the thermal loadings were the moisture movement, deformation, crack patterns, and temperature on the slab's exposed (bottom) and unexposed surface (top). The results indicated that the magnitude of temperature influences all the tested specimens. In the quench-cooled condition, the development of cracks was increased in the non-exposed slab surface when heated at 300 °C, 400 °C and 500 °C. The severity of the exposed temperature and cooling regimes also affected the concrete slab's irreversible loss of flexural stiffness. The flexural stiffness reduction of the 100 mm thick slab varied from 1.68% to 35.52% for a temperature range of 200 °C–500 °C under air-cooled conditions, while for the quench-cooled specimens, the stiffness reduction varied between 0.88% and 45.92% for the same temperature range. On the other hand, increasing the slab thickness from 100 to 150 mm decreased the stiffness reduction, where the stiffness reduced by 1.02%–24.61% and 0.28%–32.17% for the cases of air and water coolings, respectively.

Optics-Free, In Situ Swelling Monitoring of Articular Cartilage with Graphene Strain Sensors.

Articular cartilage derives its load-bearing strength from the mechanical and physiochemical coupling between the collagen network and negatively charged proteoglycans, respectively. Current disease modeling approaches and treatment strategies primarily focus on cartilage stiffness, partly because indentation tests are readily accessible. However, stiffness measurements via indentation alone cannot discriminate between proteoglycan degradation versus collagen degradation, and there is a lack of methods to monitor physiochemical contributors in full-stack tissue. To decouple these contributions, here, we developed a platform that measures tissue swelling in full-depth equine cartilage explants using piezoresistive graphene strain sensors. These piezoresistive strain sensors are embedded within an elastomer bulk and have sufficient sensitivity to resolve minute, real-time changes in swelling. By relying on simple DC resistance measurements over optical techniques, our platform can analyze multiple samples in parallel. Using these devices, we found that cartilage explants under enzymatic digestion showed distinctive swelling responses to a hypotonic challenge and established average equilibrium swelling strains in healthy cartilage (4.6%), cartilage with proteoglycan loss (0.5%), and in cartilage with both collagen and proteoglycan loss (-2.6%). Combined with histology, we decoupled the pathologic swelling responses as originating either from reduced fixed charge density or from loss of intrinsic stiffness of the collagen matrix in the superficial zone. By providing scalable and in situ monitoring of cartilage swelling, our platform could facilitate regenerative medicine approaches aimed at restoring osmotic function in osteoarthritic cartilage or could be used to validate physiologically relevant swelling behavior in synthetic hydrogels.

Comment on: Whole grain consumption and risk of radiographic knee osteoarthritis: a prospective study from the Osteoarthritis Initiative.

Dear Editor, We read the recent publication by Liu et al. with great interest [1]. They provided a possible dietary intervention for the prevention of radiographic OA of the knee for people at risk for OA. The researchers showed an inverse association between the risk of developing radiographic knee OA and whole grain consumption in their prospective cohort study. Evidence contributing to the prevention of OA has great value, because it is difficult to manage symptoms related to clinical OA, especially since the prevalence of OA is increasing and more and more people struggle with OA due to increasing obesity and prolonged life expectancy [2]. Even though we appreciate the work of Liu et al. in the prevention of OA, two main questions regarding their methods remain. First, we wonder whether the researchers also considered looking into the development of clinical OA or knee pain in their participants. The results published in the study only focus on the development of radiographic OA. In our opinion, increasing the scope of the study and also looking at clinical symptoms of OA would be a valuable addition, because the presence of radiographic OA is a poor predictor of knee pain in patients [3]. The burden of OA comes from the symptoms a patient experiences, such as pain, stiffness or functional loss. Investigating whether whole grain consumption has an association with the development of OA symptoms would make the results of the study more applicable for clinical practice.

Normalized energy index-based signal analysis through acceleration trendlines for structural damage detection

Utilizing the Trend line-based Signal decomposing Algorithm (TSA), this paper develops an innovative Structural Health Monitoring (SHM) method to locate damages in structures on the basis of vibration signature analysis. Firstly, a suitable vibration mode of the structure should be selected. The TSA is then used to determine special trend lines of the structural response according to the selected vibration mode. The damage is located through a normalized energy-based damage index calculated for these special trend lines. The accuracy of the developed method is examined using two examples: an experimental five floor laboratory building model, and a numerical arch-tied bridge, both subjected to seismic excitations. For the building model, the seismic excitation was exerted to the building model using a shaking table and the seismic acceleration responses were recorded using a set of wireless accelerometers installed at the center of each floor. For the arch-tied bridge, the numerical simulation was performed in ABAQUS software and the seismic acceleration responses were recorded on the deck near the cables. For the building model, damages were modeled as loss of stiffness in columns on different floors. For the arch-tied bridge, damages were modeled as loss of stiffness in cables. The results show that, provided that the response records and reflects damage-induced changes in the monitored structure, the developed method can accurately locate the damaged floor or damaged cable in both examples. Additionally, using the normalized energy-based method to locate the loss of stiffness in a structure makes the developed method a good candidate for rapid and simple assessment of a structure’s health state.

A deep learning approach for rapid detection of soil liquefaction using time–frequency images

Soil liquefaction – a common hazard during earthquakes – can cause severe damage to infrastructure systems. The excessive pore water pressure induced by underground shaking can result in a sudden loss of soil stiffness and strength, which renders the soil–water mixture to behave temporarily as “liquid”. Identifying liquefaction events and extracting their time of initiation and duration from recorded data are critical capabilities for validating and improving predictive models, and ultimately, effectively mitigating this hazard. The current approach is to conduct on-site investigations or simplified statistical analyses, which are generally time-consuming and bear high uncertainties, except for the most obvious cases. In this study, we utilize a convolutional neural network (CNN), a deep learning method, to predict both the occurrence of a liquefaction event and its triggering time (if it occurred). For this purpose, first, more than one million high-fidelity nonlinear site response simulations with different soil profiles and ground motions are performed. The surface acceleration time-histories are then converted into time–frequency distribution images, which are fed into a CNN as the training inputs. The trained CNN exhibits high prediction accuracy for both training and validation sets, another suite of independent site response simulations, as well as real-life earthquake data.

Effects of mesenchymal stem cells and heparan sulfate mimetics on urethral function and vaginal wall biomechanics in a simulated rat childbirth injury model

Introduction and hypothesisNew treatments are needed for pelvic floor disorders. ReGeneraTing Agent® (RGTA®) is a promising regenerative therapy. Therefore, the objective of this study was to compare regenerative abilities of mesenchymal stem cells (MSCs) and RGTA® on regeneration after simulated childbirth injury in rats.MethodsRats underwent pudendal nerve crush and vaginal distension (PNC+VD) or sham injury. Rats that underwent PNC+VD were treated intravenously with vehicle, MSCs or RGTA® 1 h, 7 days, and 14 days after surgery. Sham rats received 1 ml vehicle at all time points. After 21 days, urethral function and pudendal nerve function were tested. Vaginal tissues were harvested for biomechanical testing and histology. Biaxial testing was performed to measure tissue stiffness.ResultsPNC+VD decreased urethral and pudendal nerve function compared with sham. Vaginal wall stiffness was significantly decreased in longitudinal and transverse tissue axes after PNC+VD compared with sham. MSC or RGTA® did not restore urethral or pudendal nerve function. However, MSC treatment resolved loss in vaginal wall stiffness in both tissue axes and improved collagen content within the vaginal wall. RGTA® treatment increased vaginal wall anisotropy by increasing relative stiffness in the longitudinal direction. PNC+VD (with vehicle or MSCs) enhanced elastogenesis, which was not observed after RGTA® treatment.ConclusionsTreatment with MSCs facilitated recovery of vaginal wall biomechanical properties and connective tissue composition after PNC+VD, whereas treatment with RGTA® resulted in anisotropic biomechanical changes. This indicates that MSCs and RGTA® promote different aspects of vaginal tissue regeneration after simulated childbirth injury.

Characterization of the road profile and the rotational stiffness of supports in a bridge based on axle accelerations of a crossing vehicle

AbstractIn an effort to find more cost‐effective and proactive ways to keep bridges in good condition, the use of instrumented vehicles has gained great interest in the last decade. Two bridge components that can wear rapidly are the bearings and the road surface. However, past research on drive‐by monitoring has placed focus mostly on detecting losses of bending stiffness in the bridge deck, while assuming ideal support conditions that may differ from real cases significantly, and ignoring the characterization of the road profile. Even further, the need for specialized vehicles equipped with high‐tech instrumentation, low speeds, or very good road profiles has been a major obstacle preventing its practical implementation. This paper investigates the use of axle accelerations from an ordinary two‐axle vehicle crossing the bridge to quantify the rotational stiffness of the supports and the height of the road irregularities while overcoming the limitations exposed above. In contrast to previous research where the response of the contact point has been derived from other vehicular locations based on complex differential equations of motion, transfer functions are employed here. The key advantage of transfer functions is their simple algebraic form that can be easily calibrated on the field. The road profile is then obtained by subtracting the displacement of the bridge under each axle from the displacement of the contact point. There is one prediction of the road profile per axle but only a unique value of rotational stiffness at each support that will yield the same prediction by both axles. The algorithm is successfully tested with a half‐car traveling at 5, 10, 15, and 20 m/s, over a 15‐m bridge beam model with ISO road classes “A,” “B,” and “C,” for boundary conditions ranging from simply supported to fixed. The solution's robustness to modeling inaccuracies and noisy data is also investigated.

Fatigue and failure analysis of aluminium and composite automotive wheel rims: Experimental and numerical investigation

This paper deals with the adoption of composites in the design of the wheel rims of a sports car. With particular reference to cornering structural performance, the design of a composite wheel rim, produced via Resin Transfer Moulding (RTM) led to a reduction in mass and to an increase in bending stiffness. The adoption of alternatives to aluminium alloys allows the unsprung masses, as well as the total mass of vehicle to be contained. This paper provides a comprehensive view of the fatigue tests used for the wheel rim type-approval, followed by a rundown of wheel rims designed by Ferrari S.p.A from 2009 to present. These wheel rims have been classified in terms of mass and stiffness, and manufacturing process like casting, forging, or RTM.The failure modes of the reference Ferrari 488 GTB wheel rim were compared to those of the new composite wheel. In addition, the interpretation of the failures is supported by the results of Finite Element analyses. Though some initial defects led to a loss of stiffness of the wheel throughout the cornering fatigue test, the experimental results show that composite wheel rims are considered safe and they comply with the homologation targets and the Ferrari S.p.A. regulations.

Influences of blade crack on the coupling characteristics in a bladed disk with elastic support

In aero-engines, the blades are exposed to severe environments and subjected to complex conditions, which can cause damage and cracks. Existing analytical models focus primarily on the blade crack in a single blade. Even in the cracked-bladed disk system, most theoretical models are based on the rigid disk assumption, and few studies pay attention to the boundary conditions of the disk. A new model is proposed in this paper to compensate for deficiencies in existing theoretical models. The flexible disk and blade are deduced based on Kirchhoff plate and Timoshenko beam theories. The crack-caused stiffness loss is calculated through the released strain energy. In addition, the elastic support on the disk's inner edge is simulated by the linear spring stiffness and torsional stiffness. The accuracy of the developed model is verified by comparing it with the finite element method and experimental test. After that, the influences of the crack depth and crack location on the coupling characteristics of the system are systematically investigated. The results indicate that blade crack mainly affects the blade-predominated modes, leading to the mistuned disk mode shapes, which are symmetrically distributed along the line between the cracked blade and the disk center. Moreover, as the blade crack becomes severe or approaches the blade root, the first natural frequency of the paired orthogonal modes decreases; the first mode shape of the paired tuned high nodal diameter degenerates into mistuned low nodal diameter; the new coupling characteristics between the mistuned disk and elastic support become more stronger. The proposed methodology can serve as a theoretical basis for diagnosing faults and monitoring safety in the bladed disk coupling system.

Beams With a Varying Cross Section in the Generalized Strain Formulation for Flexure Modeling

Abstract Flexure joints are rapidly gaining ground in precision engineering because of their predictable behavior. However, their range of motion is limited due to a stress limitation and a loss of support stiffness in deformed configurations. The support stiffness can be significantly increased by using leafsprings of which the width and thickness vary over the length of the leafspring. This paper presents formulations for two beam elements with a varying cross section that can be used for the efficient modeling of these types of leafsprings. One of these beam-formulations includes the modeling of the warping due to torsion, which is shown to be essential for accurate modeling. The 90% accuracy in stiffness results and 80% accuracy in stress results, in comparison with results of finite element analyses, are sufficient for the evaluation of concept-designs. Optimizations show that the support stiffness of two typical flexure joints can be increased by a factor of up to 4.0 keeping the same range of motion, by allowing the cross section to vary over the length of the leafspring. In these two flexure joints, 98% of this improvement can already be obtained by only varying the thickness, and keeping a constant width.

The role of the planar joints without bolts on the structural behaviour of coupled segmental tunnels built in soft soils

This paper aims to evaluate the role of planar joints without bolts on the structural behaviour of segmental tunnels. Segmental tunnels could be vulnerable to deformation problems due to the presence of the joints, such as segment cracking, joint damage and its opening. As a result, the lining presents a limitation of its load capacity and stiffness loss that can jeopardize its safety and durability. Thus, in this paper the joint influence was evaluated on the lining behaviour with different structural parameters. These parameters were relative height of joints, slenderness ratio and pressure ratio of the lining. The lining behaviour was estimated by numerical models that included the nonlinearity of joints and materials using a 3D finite element model. The joint influence was studied through the stiffness, the load capacity and the failure mechanism of the lining. It is concluded that the joints have a main influence on the structural behaviour of the lining. For example, in the bending domain due to the joint opening and the damage by the coupling effects, as the diametral deformation of the lining increases, the stiffness decrements. This stiffness loss reached without the reinforcement yields. On the other hand, in the compression domain, the stiffness loss begins with the joint failure by concrete bursting. The joint losses its capacity to transfer load. It develops a failure mechanism of lining at lower deformation. Thus, the design lining should be based on a suitable role of their joints.

Behavior of cross-laminated timber panels during and after an ISO-fire: An experimental analysis

Cross-laminated timber has been used in buildings since the 1990s. In the last years, there has been a growing interest in the use of this technology, especially with the adoption of the product in increasingly taller buildings. Considering that the product is manufactured from a combustible material, wood, authorities that regulate the fire safety in buildings and the scientific community have carried out numerous research and fire tests, aiming to elaborate codes which contemplate the use of cross-laminated timber in tall buildings. This paper discusses the main results obtained from the fire resistance test of a cross-laminated timber slab carried out in the horizontal gas furnace (3.0 m × 4.0 m x 1.5 m) from the University of Sao Paulo. A vertical load of 3 kN/m2 was applied over the slab and the specimens were exposed to the standard fire curve for 30 min. In addition to the 30-min test, the research also evaluated the thermal behavior of the samples during the 24 h after the burners were turned off. Throughout the test, the slab maintained the integrity and the thermal insulation, and no falling-off of the charred layer was observed. However, the 24-h test indicated that it is mandatory to consider the loss of stiffness and strength of timber caused by the thermal wave observed during the decay phase.

ANATOMICAL AND BIOMECHANICAL ROLE OF STATIC STABILIZERS OF THE ACROMIOCLAVICULAR JOINT.

The aim: To determine the anatomical and biomechanical significance of the static stabilizers of the acromioclavicular joint by conducting numerical modeling using the finite element method and experimental investigation. Materials and methods: To ensure the study, modeling of the deformation processes of the clavicle and scapula systems with various combinations of ligament damage was conducted. The COMPAS-3D software package was used to build the simulation model, which allowed obtaining models that are closest to reality. To verify the results of the numerical modeling, corresponding studies of the mechanical characteristics and determination of the stiffness of the investigated systems were carried out using the upgraded TIRAtest-2151 testing stand. Results: The stiffest system is the system in which all ligaments are intact, and the sequence of decreasing stiffness of the system is presented in the following order: damage to lig. trapezoideum; lig. conoideum; lig. claviculo-acoacromiale inferior; lig. claviculo-acoacromiale superior; the coracoclavicular ligament complex; the acromioclavicular ligament complex. Conclusions: Static stabilizers in general, and their components in particular, are characterized by significant anatomical and functional features. The natural stabilization of the acromioclavicular joint is provided by their synergistic interaction, which is the basis for the development and implementation of surgical interventions, the scope of which includes the restoration of both ligament complexes. The loss of stiffness in the «clavicle-scapula» system is significantly more pronounced when lig. acromioclaviculare superior and inferior are damaged (8.5 N/mm) than when lig. conoideum and lig. trapezoideum are damaged (11.6 N/mm).