Load Redistribution Research Articles

PRIMARY AND POST-OSSEOINTEGRATION STABILITY OF SHORT (ULTRA-SHORT) IMPLANTS ON EDENTULOUS ATROPHIED DISTAL SEGMENTS OF THE MANDIBLE - AN INDICATOR OF IMMEDIATE OR DELAYED LOAD

Introduction. The issue of determining the possibility of immediate or long-term load on the selected type of implants, which will ensure the predictable result of their long-term functionality, remains an ongoing discussion. The results of the resonance frequency analysis, which perfectly characterize the stability of short and ultrashort implants at all stages of their osseointegration and post-osseointegration periods, can serve as such an indicator basis. Aim. To analyze the primary and post-osseointegration stability of short (ultra-short) implants placed by the methods at the level of the cortical bone layer and subcortically in case of bone atrophy caused by acquired final dentition defects. Materials and methods. The primary and post-osseointegration stability of thirty-nine dental short (h = 6.5 mm X b = 4.0 mm – 20 pieces) and ultra-short (h = 5.5 mm X b = 4.0 mm – 19 pieces) implants placed on the edentulous distal segments of the human mandible was studied. According to the clinical assessment that met the aim and objectives of this study, all patients were divided into four study groups: the first group consisted of patients with a preserved dentition who did not require dental implantation; the second group – 25-45 years old, the third group – 46-60 years old, and the fourth group – ≥ 61 years old. Using the resonance frequency analysis (RFA) method by Penguin Instruments, the results were interpreted in declarative units of measurement – the implant stability quotient (ISQ). Results. The installed short (ultrashort) implants, according to the methodology by the level of the cortical layer of bone tissue, are characterized by their high primary stability by anti-rotational force: in the second group of the study (25-45 years old) with a mean number (M) of 87.0 and an error of the mean (± m) of ± 2.3 ISQ; in the third group (46-60 years old) – 76.4 ± 3.0 ISQ; in the fourth group (persons ≥ 61 years old) – 69.8 ± 4.8 ISQ. Low values of primary stability were obtained in implants installed by the subcortical implantation technique in the second age group of the study and amounted to 59.6 ± 2.7 ISQ with a slight increase to 66.0 ± 4.1 ISQ in the third group and 71.7 ± 4.2 ISQ in the fourth group of the study, which do not guarantee the prognosis of functional redistribution of the supra occlusion immediate load on the biological basis, with further preservation of the course of normal physiological processes in the bone tissue around the implanted implants. Conclusions. Rehabilitation of patients with bone atrophy caused by the loss of the masticatory group of teeth is possible using short (h = 6.5-6.0 mm) and ultra-short (h = 5.5 mm) implants, with clinical justification for the choice of methods of immediate or post-osseointegration load, with a detailed resonance frequency analysis as a priority and reliable method – an effective indicator of their stability, at all stages of clinical rehabilitation of patients.

COMPUTER MODELLING OF AERODYNAMIC FLOW OF A COMPLEX OF UNIQUE BUILDINGS

The way large-sized buildings interact with wind flows cannot be analyzed when considering such objects in isolation from their environment. The paper proposes a model representing such objects from the point of view of hydrogasodynamics as a system of bodies united by aerodynamic medium. A quantitative and qualitative assessment of the mutual influence of system objects on aerodynamic characteristics at different locations was performed. The results of computer modeling of the aerodynamic characteristics of two unique buildings in an isolated mode, as well as for various mutual positions in the system, using the methods of a computational experiment based on the numerical solution of non-stationary systems of Navier-Stokes differential equations are presented. The accuracy of the results obtained was monitored by conducting a model experiment in a wind tunnel. For the qualitative assessment of the mutual influence of objects on each other, the characteristics of the vector of the wind pressure force equalizing vector on each of the objects and the value of the equalizing moment at the base of the object most sensitive to its influence were determined. In this way, a quantitative assessment has been made that allows us to judge the redistribution of wind loads and the static characteristics of the system. On the basis of changes in their values the conclusion about the way the objects interact with wind flows depending on their initial geometric parameters and mutual location within the system was given.

Vertical load distribution in precast hollow core floors: State of the art and future perspectives

AbstractPrecast prestressed hollow core (HC) floors are widely used in various applications within the construction sector. Such floors are usually designed as single, simply supported elements, although it is known that individual elements forming the floor interact with each other. This article presents the state of the art regarding load redistribution in HC floors in the light of experimental data, current analytical models and code provisions. While this phenomenon is widely known and recognized, only sparse, and often poorly documented experimental data are available, which represent the basis for the assessment and calibration of analytical models. Moreover, even though the available models and code provisions share similar assumptions, their outcomes are in some cases conflicting. Having recognized the existing knowledge gap, the authors outline future perspectives for the development of consistent analytical and numerical approaches supplemented by new experimental data.

Specific Features of Load Redistribution in Cellular Hydraulic Structures Resulting from Seismic Impacts When Surcharging Wet Water-Saturated Soil Infill

Specific Features of Load Redistribution in Cellular Hydraulic Structures Resulting from Seismic Impacts When Surcharging Wet Water-Saturated Soil Infill

Lightworks, a scientific research framework for the design of stiffened composite-panel structures using gradient-based optimization

Efficient structural optimization remains integral in advancing lightweight structures, particularly concerning the mitigation of environmental impact in air transportation systems. Varying levels of detail prove useful for different applications and design phases. The lightworks framework presents a modular approach, for the consideration of individual design parameterizations and structural solvers for the numerical optimization of thin-walled structures. The framework provides the combination of lightweight fibre composite design and the incorporation of stiffeners for a gradient-based optimization process. Therefore, an analytical stiffener formulation is implemented in combination with different continuous composite material parameterizations. This approach allows the analysis of local buckling modes, as well as the consideration of load redistribution between stringer and skin. The flexibility achieved in this way allows a tailored configuration of the optimization problem to the required level of complexity. A verification of the framework’s implementation is carried out using established literature results of a simplified unstiffened wing box structure, where a very good agreement is shown. The accessibility of solvers with different fidelity through a generic solver interface is demonstrated. Furthermore, the usage of the implemented continuous composite parameterizations as design variables is compared in terms of computational performance and mass, providing different advantages and disadvantages. Finally, introducing stringer into the wing box use case demonstrates a 38% mass reduction, showcasing the potential of the inline optimization of stiffeners.

Numerical Simulation on the Leakage-Induced Collapse of Segmental Tunnels

Sudden leakage during tunnel construction poses a great threat to the safety of the tunnel. There are relatively few studies on the mechanism of structural collapse induced by tunnel leakage, so it is difficult to propose effective control measures. To solve this problem, a coupled fluid–solid strata analysis model and a nonlinear FEM tunnel model were established based on model test results to analyze the mechanism of tunnel collapse. The following conclusions were drawn: (1) A DEM-based coupled fluid–solid model combined with a nonlinear FEM tunnel model can effectively simulate the physical process of tunnel collapse. (2) The mechanism of tunnel leakage-induced strata response is the continuous destabilization and reappearance of the soil arching effect, which restricts the erosion of the soil and results in macroscopic soil caves, and finally leads to the impact load of the destabilized soil. (3) The process of the tunnel structure collapse is as follows: firstly, a large deformation of the tunnel structure is caused by the redistribution of external loads generated by the earth arching effect; then, due to the multiple impact loads from the destabilization of the soil, plastic hinges are generated at the tunnel joints, and the tunnel collapses.

A robustness-oriented procedure for the design of tying reinforcement in precast concrete hollow-core floors

Buildings may be subjected during their service life to extreme events which can trigger progressive collapse. On this front, the role played by tying reinforcement in structural members is crucial for an adequate load redistribution and the avoidance of disproportionate collapse. This work proposes a robustness-oriented procedure for the design of tying reinforcement placed in the hollow-core units and beams of precast concrete buildings, where limited studies are available in scientific literature. In particular, the aim is to provide a simple yet reliable approach for the design of concentrated and distributed ties in precast floors by adopting fundamental input parameters such as the system’s chord rotation capacity and dynamic amplification factor, which are not considered in current design codes. Firstly, a flow-chart of the design procedure is proposed and discussed. Secondly, the input parameters are calculated based on recent analytical approaches - proposed by some of the authors - to optimize the tying reinforcement design. Finally, the efficiency of the design procedure is demonstrated with an application example, and a novel detailing scheme is proposed which is aimed at a significant enhancement of structural robustness. Due to its simplicity, the proposed design procedure is contended to be applicable in robustness assessment and design of building structures with precast concrete hollow-core floors.

Hybrid-grained migration method for load redistribution in heavily-loaded fog nodes

Hybrid-grained migration method for load redistribution in heavily-loaded fog nodes

Enhanced whale optimization algorithm for dependent tasks offloading problem in multi-edge cloud computing

In this paper, we introduce the Enhanced Whale Optimization Algorithm (EWA) to optimize dependent task offloading in a multi-edge cloud computing environment. Our proposed algorithm aims to identify the most suitable offloading scenario for dependent tasks, focusing on minimizing total processing latency, energy consumption, and associated costs. We operate within a system comprising many decentralized Mobile Edge Computing servers (MECs) and a centralized cloud server. Two novel improvement operations, namely Frame Shifting (FS) and Load Redistribution Strategy (LRS), are introduced to enhance the performance of the whale algorithm. Through simulation, our results demonstrate the superior performance of EWA. Specifically, compared to the Whale Optimization Algorithm (WOA), EWA achieves a remarkable reduction in latency by 22.84%, a substantial decrease in energy consumption by 78.28%, and a notable reduction in cost usage by 61.47%. These outcomes underscore the efficacy and practical significance of the proposed EWA in addressing the challenges posed by dependent task offloading in the multi-edge cloud computing landscape.

Time-dependent soil–structure interaction analysis using a macro-element foundation model

The delayed settlement of foundations due to soil consolidation, creep or particle breakage can alter the internal load distribution and differential settlements in a superstructure through soil–structure interaction (SSI). The study introduces a novel methodology to simulate time-dependent SSI that overcomes the complexity of incorporating the time-dependent behaviour of foundations into routine SSI analysis. The proposed approach represents the superstructure as a condensed stiffness matrix, and replaces the foundations and underlying soils with macro-element foundation models that encapsulate the foundation–soil interaction into load–displacement relationships derived from constitutive models. To examine the performance of the proposed method, a macro-element model for time-dependent analysis of shallow foundations on sand was integrated with structural analysis to simulate two tests performed in a geotechnical centrifuge on a 3D-printed aluminium framed structure supported by footings on sand. The simulated responses of the superstructure and foundations were found to agree well with those observed in the centrifuge tests. Parametric analyses were conducted to investigate the effect of loading history, load level on the superstructure, and creep tendency of soil on post-construction load redistribution and differential settlements. The findings suggest that creep of foundations on sand facilitates load redistribution in the structure from heavily loaded sections to lightly loaded sections. Moreover, post-construction load redistribution depends on the differential creep between footings and should be considered for structures that are quickly constructed or at high levels of strength mobilisation (low factor of safety). Overall, the study highlights the potential of the proposed methodology in analysing the time-dependent SSI and its applicability in practical SSI analysis.

A model for modifying the S‐N curve considering the effect of boundary conditions on the fatigue crack growth of welded components

AbstractThe present study proposes a novel model to modify master S‐N curves of components according to their load redistribution capability reflected in different boundary conditions (BCs) based on the fracture mechanics analysis. To that end, a comprehensive numerical study was conducted on a Single Edge Notch Bend (SENB) specimen constrained with different kinematic BCs using discrete fatigue crack growth (FCG) simulation. It was observed that BCs indeed can have a significant effect on the crack growth behavior and consequently on the resulting fatigue life under the same nominal loading conditions. The proposed model was applied to the S‐N curve of a T‐welded joint, and the predicted fatigue life was validated against 3D FCG simulations. Finally, FCG tests were conducted on SENB specimens to experimentally corroborate the effect of BCs on the FCG rate.

Biofeedback training for the analysis of gait stereotypes in patients with gonarthrosis

BACKGROUND: The justification of the treatment techniques for patients with gonarthrosis requires the use of modern methods for assessing walking stereotypes.
 AIM: This study aimed to evaluate the biomechanical and podometric gait parameters of patients with gonarthrosis using the C-Mill multifunctional complex with biofeedback.
 MATERIALS AND METHODS: The study included 55 patients who were divided into the following groups: main group (n=35) of patients who had gait disturbances, diagnosed with stage III–IV primary gonarthrosis with varus deformation of the limb axis according to ICD-10, and underwent total knee replacement and control group (n=20) of patients diagnosed with stage I primary gonarthrosis. The average age of patients was 58.7 years in the main group and 47.5 years in the control group.
 RESULTS: In the main group, the decrease in average walking speed was accompanied by decreases in stride length and step frequency (р 0.05). In the stance phase, which is characterized by the contact of the foot of the affected and contralateral lower extremities with the platform surface, the durations of the double stance phase of both extremities in the main group were longer than those in the control group (p 0.05), indicating gait asymmetry and redistribution of excess load on the contralateral lower extremity, which is clinically manifested by lameness. In the main group, gait was characterized by a decrease in voluntary speed, step frequency, and gait pattern changes in various planes, confirming severe clinical and functional disorders in the lower limbs.
 CONCLUSION: The study of the walking stereotype in patients using the C-Mill multifunctional complex with biofeedback can be used to substantiate treatment techniques, followed by drawing up an individual medical rehabilitation plan to restore lower limb functions in the postoperative period, fully monitor treatment dynamics, prevent falls, and improve the quality of life of patients.

Case Studies about Finite Element Modeling and Wireless Sensing of Three Pennsylvania Bridges.

Three Pennsylvanian bridges were studied using finite element and wireless sensor technology. A detailed finite element model of each bridge was created using a commercial software in order to calculate the strains generated by a load that simulates the presence of a standard truck. Pristine and damage scenarios were simulated, and the computed strains were compared to the experimental strains measured with proprietary wireless sensors during a truck test performed by companies not involved in the study presented in this article. The comparison demonstrated the accuracy of the model and the presence of a few non-critical anomalies in terms of load redistribution. In addition, the comparison proved the reliability of the wireless sensing system installed on the bridges, although some drift was observed. The structural monitoring program for the three bridges was also evaluated by processing more than two years of data streamed to a repository.

The use of medial joint opening rather than mechanical axis deviation to determine the clinical outcomes after high tibial osteotomy.

The aim of this study was to evaluate whether achieving medial joint opening, as measured by the change in the joint line convergence angle (∆JLCA), is a better predictor of clinical outcomes after high tibial osteotomy (HTO) compared with the mechanical axis deviation, and to find individualized targets for the redistribution of load that reflect bony alignment, joint laxity, and surgical technique. This retrospective study analyzed 121 knees in 101 patients. Patient-reported outcome measures (PROMs) were collected preoperatively and one year postoperatively, and were analyzed according to the surgical technique (opening or closing wedge), postoperative mechanical axis deviation (deviations above and below 10% from the target), and achievement of medial joint opening (∆JLCA > 1°). Radiological parameters, including JLCA, mechanical axis deviation, and the difference in JLCA between preoperative standing and supine radiographs (JLCAPD), an indicator of medial soft-tissue laxity, were measured. Cut-off points for parameters related to achieving medial joint opening were calculated from receiver operating characteristic (ROC) curves. Patients in whom the medial joint opening was achieved had significantly better postoperative PROMs compared with those without medial opening (all p < 0.05). Patients who were outliers with deviation of > 10% from the target mechanical axis deviation had significantly similar PROMs compared with patients with an acceptable axis deviation (all p > 0.05). Medial joint opening was affected by postoperative mechanical axis deviation and JLCAPD. The influence of JLCAPD on postoperative axis deviation was more pronounced in a closing wedge than in an opening wedge HTO. Medial joint opening rather than the mechanical axis deviation determined the clinical outcome in patients who underwent HTO. The JLCAPD identified the optimal postoperative axis deviation necessary to achieve medial joint opening. For patients with increased laxity, lowering the target axis deviation is recommended to achieve medial joint opening. The target axis deviation should also differ according to the technique of undergoing HTO.

A Flow Graph–Based Scalable Critical Branch Identification Approach for AC State Estimation Under Load Redistribution Attacks

A Flow Graph–Based Scalable Critical Branch Identification Approach for AC State Estimation Under Load Redistribution Attacks

Determining the influence of sandwich-type components on the load of a hatch cover in a universal open wagon

The object of the study reported here is the processes of occurrence, perception, and redistribution of loads in the improved structure of the hatch cover in a universal open wagon. In order to reduce the load on the cover of an open wagon hatch, and, accordingly, to improve its strength, it is proposed to improve its design by introducing sandwich components. The thickness of the sheets that form the hatch cover has been determined. The dynamic loading of the hatch cover in the vertical plane was studied. It was found that the accelerations acting on the hatch cover with the proposed improvement are almost 20 % lower than those acting on the typical structure. The basic strength indicators of the hatch cover under the operational modes of its load have been determined. The results of the calculation showed that the maximum stresses in the hatch cover are 22 % lower than permissible ones. In addition, within the framework of the study, the main indicators of the dynamics of the open wagon equipped with the proposed structure of hatch covers were determined. The movement of the open wagon under the condition of movement in an empty state is rated as "good". At the same time, the maximum accelerations in the center of mass of the supporting structure of an open wagon were 4.6 m/s2, and the coefficient of vertical dynamics was about 0.6. Special features of the results within the framework of this study are that the proposed improvement of the hatch cover helps improve its strength by reducing the dynamic load, and not by strengthening the structure. The scope of practical application of the results is the engineering industry, in particular, railroad transport. The conditions for the practical use of the research results are the use of energy-absorbing material in the sandwich-type components that form the hatch cover. The study reported here could contribute to devising recommendations for the construction of components in the structures of modern freight cars, thereby reducing the costs of maintaining them in operation, as well as increasing the profitability of railroad transportation

False Data Injection Attack with Max-Min Optimization in Smart Grid

With the proliferation of information and communication technology (ICT), the smart grid is critically vulnerable to cyber-attacks such as false data injection (FDI), denial-of-service, and data spoofing. The cyber-attackers defunctionalize critical operations of the smart grid by compromising the ICT. The decisions for the critical operation of the smart grid are processed with a state estimator, and ICT makes the state estimator vulnerable to FDI attacks. Hence, vulnerability analysis of the state estimator needs to be investigated for potential FDI attacks to protect it from future cyber-attacks. This work proposes the FDI attack vector construction without the knowledge of bad data detection (BDD) threshold on linear and non-linear state estimators using max-min optimization considering the partial network information. The optimization problem is formulated from the attacker's perspective to target the manipulation of measurements in the attack zone so as to increase the generation cost. The equivalent power injection model is developed for the attack zone to construct the deceptive attacks using DC and AC power flow models. The effectiveness of the proposed framework has been tested on 5 bus PJM network, modified IEEE 30 bus, IEEE 57 bus, and IEEE 118 bus system. The proposed framework is compared with existing state-of-art methods (viz., linear attack policy, non-linear attack policy, load redistribution attack, and line flow attack) to assess its efficacy. It is observed that the developed FDI attack vector successfully bypasses the bad data detectors such as the chi-square test, largest normalized residue, and l2 detector that is normally used by the system operator. Moreover, the study compares and discusses the impact of FDI attacks on the estimated state variables obtained with state estimators and, thereby, the generation cost calculated with the DC & AC optimal power flow tool.

Effect of network topologies and attacking strategies on cascading failure model with power-law load redistribution

Various traffic networks play an important role in daily life and have different topological characteristics such as small-world and scale-free. The factors of traffic congestion, natural disasters and traffic accidents may induce cascading failure in which the load redistribution usually has the characteristic of power-law (that is to say, when a station is broken, the great majority of passengers would evacuate to the nearby stations, but the very few would evacuate to further). Based on them, this paper studies the load-capacity cascading failure model with power-law load redistribution using three kinds of attacking strategies (removing a single node according to the load, removing multiple nodes according to the load and removing multiple nodes randomly) for different network structures (random networks, WS small-world networks and BA scale-free networks). We confirm the robustness of our results by further performing simulations on real-world traffic networks. A quantitative description of network topologies and attacking strategies vs. the cascading failure model with power-law load redistribution is obtained by computer simulation. The results demonstrate that in contrast to removing the node according to the load, network robustness increases with the increase of the load control parameter α when randomly removing the node; when θ is small, the load tolerance parameter β is sensitive to the network robustness in random networks and WS small-world networks when removing a single node according to the load.

Arm Back Support Suit (Abs-Suit) for Parcel Delivery With a Passive Load Redistribution Mechanism

Arm Back Support Suit (Abs-Suit) for Parcel Delivery With a Passive Load Redistribution Mechanism

Experimental-studies using in-plane small-scale steel moment-resisting-frames considering load redistribution capacity during fire

In this study, parametric transient state tests using small-scale substructure specimens of multi-storied steel moment-resisting frames at fire are conducted to examine the effects of the load redistribution capacity (redundancy) on the overall collapse temperature after a heated column local-buckled. Three types of specimens with one, two, and three stories and two spanned steel frames are experimentally analysed, and the centre steel column and beams on the first story are heated using an electric furnace. Test results show that the axial force of the heated column is redistributed to the intact side-columns by the lifting resistance force of the beams, and the collapse temperature of the frame specimen increased. A simple calculation model is proposed to evaluate the overall collapse temperature considering the load redistribution capacity, and the calculation results agree with the test results.