Moment Of Failure Research Articles

Shear Performance in Reinforced Concrete Beams with Partial Aggregate Substitution Using Waste Glass: A Comparative Analysis via Digital Imaging Processing and a Theoretical Approach.

The usage of waste glass aggregate (WGA) associated with the replacement of fine aggregate (FA) and coarse aggregate (CA) is observed to reduce the number of raw materials for sustainable concrete. For this aim, a total of 15 beams were produced, and then investigational experiments were implemented to observe the shear performances. The stirrup spacing and WGA proportion were chosen as the main parameters. FA and CA were exchanged with WGA with weight proportions of 0, 10, and 20%. The experimental investigation results showed that changing stirrup spacing and WGA proportion affected the fracture and shear properties of reinforced-concrete-beams (R-C-Bs). Furthermore, the findings of the test results revealed that the proportion of WGA could be efficiently consumed as 20% of the partial replacement of FA. With the addition of FA to the mixture, the load carrying capacity of R-C-Bs increases. On the other hand, increasing the WGA ratio by more than 10% using CA, together with increasing the stirrup spacing, can significantly reduce the capacity of R-C-Bs. It was observed that the calculated shear strengths of R-C-Bs with inadequate stirrup spacing, based on ACI 318 and EC2 design codes, can be up to 52 and 79% higher than the experimental results for R-C-Bs containing coarse glass aggregate and 21 and 56% higher for R-C-Bs containing fine glass aggregate, respectively. Additionally, an image processing method was applied to describe the damages/microdamages in R-C-Bs. At that point, the findings obtained from the experimental part of the study were confirmed by the results of the image processing method. Although the strains obtained with the image processing method are reliable, it has not been determined exactly where the crack will occur due to the very sudden development of the shear crack at the moment of beam failure.

Evolution characteristics of an induced electric charge signal and identification method of charge for instability failure in loaded coal

A coal-loaded charge induction monitoring system is developed to effectively forecast the dynamic disasters caused by coal failure. Specifically, a digital finite impulse response (FIR) filter is designed to denoise and filter the signal, and the time-frequency domain evolution of induced charge signals is analyzed during coal failure experiments. The quantitative relationships between the induced electric charge and stress-strain energy, and ultimately, between induced electric charge and coal deformation/failure, are revealed. Ultimately, the electric charge sensor exhibits high signal collection frequency and high sensitivity, and the FIR low-pass filter constructed in MATLAB effectively denoises and filters induced charge signals. The main frequency range of the white noise is 50–500 Hz, and the main frequency of the charge signal induced by coal deformation and failure is concentrated in the range of 0–50 Hz. The optimal distances for monitoring cubic and cylindrical raw coal samples using this sensor are 9 mm and 11 mm, respectively. Notably, strain energy is released faster when it can dissipate more readily, and induced charge pulses become denser when more intense signals produce large fluctuations. A method is proposed to identify coal deformation and failure based on changes in the induced electric charge. This study provides a new means of monitoring the early warning signs of dynamic coal mine disasters. Based on our experimental results and conclusions, a new method is proposed to identify coal deformation and failure based on changes in the induced electric charge. The precursor to the moment of coal failure can be identified by monitoring the amplitude of the induced charge, the dynamic trend of fluctuation, and the cumulative number of induced electric charge pulses during the process of coal deformation.

Study on signal characteristics of burst tendency coal under different loading rates

In order to study the mechanics, acoustic emission (AE) and electromagnetic emission (EME) response law of bursting liability coal at different loading rates, uniaxial compression tests were carried out on coal mass from Konggu Coal Mine. The corresponding relations among mechanical properties, AE and EME signals in the process of coal failure under loading were analyzed, and the energy evolution law of coal failure with bursting liability under loading rate was discussed. The results show that within a certain range of loading rate, the higher the loading rate, the higher the compressive strength and peak load of bursting liability coal, and the shorter the time for coal to reach the peak load. Under different loading rates, the mechanics, AE and EME signals of coal samples can be well corresponded. When the loading rate is low, the number of blocks destroyed of coal sample is large and the block size is relatively small, and the blocks are mainly scattered around the test platform. When the loading rate is high, the number of damaged blocks is relatively small and the block size is relatively large, and the blocks are far away from the test bench. When loading at a low rate, the internal cracks in coal can be fully developed and connected, and the energy release rate is relatively uniform in the process of loading and failure of coal sample. In the case of high loading rate, the energy release rate of coal sample in the loading process is much smaller than that in the moment of failure. Combining the above test results with the actual situation of the working face, it can be concluded that the total energy stored in the coal of fast mining increases and the threshold of impact decreases compared with that of slow mining. Therefore, under the disturbance of external dynamic load, rapid mining is more likely to induce rock burst.

The failure mechanism of the Baishi landslide in Beichuan County, Sichuan, China

The Baishi landslide was located in the western part of Beichuan County, Sichuan Province, China. The landslide experienced multiple minor collapses at the front part, accompanying with numerous tensile cracks. To comprehensively grasp the stability conditions and predict the moment of failure of the landslide, deformation monitoring of the landslide has been carried out from the moment that the landslide was reported until it failed. This study analyzed the different phases of landslide deformation and its failure mechanism through the analysis of monitoring data. The result showed that the failure manifests both the retrogressive and advancing features. The landslide was divided into several zones based on the spatial variation of the deformation characteristics. Moreover, the improved tangential angle criterion is applied to categorize the deformation phases of a landslide. Investigating the surface displacement vectors and vector angles of landslides plays a significant role for ascertaining the failure and sliding mechanism. The monitoring results revealed that the front part of the landslide played a key role in the stability of the landslide. Therefore, the monitoring data from this zone were crucial for predicting the moment of complete landslide failure.

Підвищення ефективності забезпечення працездатності транспортних засобів

Accidental failures, leading to unplanned repairs, significantly increase the cost of their elimination compared to planned measures. A significant part of such failures are not sudden in nature. Gradual failure is preceded by a gradual change in some parameters. The impact of gradual failures on the efficient operation of road freight transport is increasing. Despite the fact that the failure of the engine, clutch or automatic transmission is not dangerous to the life and health of people, their impact on the economic condition of the enterprise is significant. There is a trend of decreasing the size of the rolling stock fleet for most of the country's motor transport enterprises. Therefore, the importance of keeping each car in working condition increases. To increase the accuracy of the prevention of gradual and sudden-gradual failures, a forecasting method based on the diagnosis of trucks with a specialized diagnostic car scanner TEXA Navigator MULTIHUB is proposed. The selection of diagnostic parameters was carried out in accordance with the requirements for compliance with the accuracy, efficiency, and informativeness of the diagnostic parameters. The research was carried out on MAN TG-X, MAN TGA, VOLVO FH 12, DAF 105 XF, and DAF 106 cars. A sequential cylinder shutdown test was conducted to determine the compression and efficiency of all cylinders. A gradual change in the operating parameter is determined based on the obtained decrease in revolutions. In the next test, the correction of the injectors for the amount of fuel injected into the cylinders is checked. The reference value is taken as 0. The correction tolerance for increasing or decreasing the fuel supply time should be within +1 or –1. Based on the received data, the nozzle is determined, in the correction gradually increases, which signals a problem with the nozzle's operation. For the clutch, a test of the position of the start of switching on and off was carried out. By reducing the percentage of idling, you can determine the gradual engagement of the clutch. All the conducted tests make it possible to graphically display a change in a parameter or property and, using extrapolation, to predict the moment of failure. All cars carry out freight transportation in international traffic. Control parameters and data extrapolation made it possible to predict engine, clutch, and automatic transmission failures. Selected diagnostic parameters can be used to predict and prevent failures.

A novel slit damper configuration to enhance ductility and seismic behavior of concentrically braced frames

Steel slit dampers are the specific type of metallic yielding dampers used for the structural passive control. They are constructed by introducing a series of openings or slits in a steel plate to control the seismic behavior of structures. These dampers absorb energy through shear yielding, flexural yielding, or a combination of both. In this paper, a new form of steel slit damper is introduced and examined. The novel damper, called the Zipper-shaped Slit Damper (ZSD), is composed of two nested boxes connected through high-strength bolts. There are several steel strips in an external box and L-shaped profiles to prevent out-of-plane buckling, maximize flexural capacity, and ensure optimal lateral force distribution. Additionally, L-shaped profiles are welded to the ends of the steel strips. To assess the structural capacity and seismic behavior, ZSD is modeled in three dimensions using ABAQUS finite element software. The model is first validated against experimental results and then subjected to cyclic nonlinear static analysis, comprising 15 models with different width-to-thickness and height-to-width ratios of steel strips. The failure index (FI), based on equivalent plastic strain, is employed to predict the moment of failure. The results obtained from the FI were analyzed, and the analysis was limited until the moment of the first failure. On average, the novel damper demonstrated improved durability with an increase in the height-to-width ratio, resulting in enhanced ductility up to 8.75. Additionally, within each width -to-thickness ratio group, a 0.5 unit increase in this ratio corresponded to a reduction of approximately 10 % in energy dissipation efficiency. The equivalent viscous damping in the models averaged 42 %. The analysis indicated that all models exhibited stable hysteresis cycles and had high ductility and energy dissipation. Also, considering the obtained results, it can be concluded that the ZSD, due to its replaceable components, ease of construction, and easy installation, can be utilized in concentrically braced frames. Mechanical models, as well as stiffness and force relationships for design and implementation in braced frames, are presented. The findings provide valuable insights for the utilization of this innovative damper in seismic-resistant structural systems.

Investigation on failure characteristics of mode II crack in heat-treated granite specimen subjected to dynamic loading

In order to solve the energy crisis, geothermal energy development has been increasingly valued in recent years. In many geothermal engineering projects, hydraulic fracturing can cause many cracks to appear inside the rock mass during the extraction process of dry hot rock. At present, there have been many studies on mode I cracks and mixed mode I/II cracks. In order to ensure the smooth progress of the project, it is necessary to supplement the research on mode II crack rocks in high-temperature geothermal environments. A series of experiments were conducted using the Split Hopkinson Pressure Bar (SHPB) device and cracked granite specimens treated at different temperatures, the failure modes could be tracked by using a high-speed camera. The dynamic experiment was simulated using software coupling. The Grain Boundary Model (GBM) can well describe the force-thermal coupling damage behavior among various crystal particles. Some analyses were conducted on dynamic fracture toughness, failure mode, strain distribution, thermal damage, and changes in the number of cracks. The research results illustrated that high temperatures lead to a decrease in the mode II fracture toughness of granite, an increase in fracture time, and greater susceptibility to damage. High temperature will increase the maximum strain at the moment of failure. It was also found that the proportion of intra-grain cracks increased with the temperature. After 500 °C, the number of cracks generated during the fracture process is inversely proportional to the temperature.

Estimating the parameter of a geometric distribution from series system data

In a traditional setup of estimation of an unknown parameter of component lifetime distribution, system’s continuous lifetime data is used. In this paper, we propose a simple and competitive estimator that is based on discrete lifetime data, i.e., the number of failed components at the time when the system fails. In particular, we consider the estimation of the parameter of a geometric distribution based on the system’s lifetime data, and the number of failed components upon the failure of the system when the system has a series structure. Two moment estimators that are based on the system lifetime data and the number of failed components at the moment of system failure are obtained and their performances are compared in terms of the mean square error. The associated Bayesian estimators with non-informative priors are also discussed.

Study on the calculation method of the maximum number of bonded steel plates at the bottom of reinforced concrete beams

Purpose When the reinforced concrete beams are reinforced by bonding steel plates to the bottom, excessive use of steel plates will make the reinforced concrete beams become super-reinforced beams, and there are security risks in the actual use of super-reinforced beams. In order to avoid the occurrence of this situation, the purpose of this paper is to study the calculation method of the maximum number of bonded steel plates to reinforce reinforced concrete beams.Design/methodology/approach First of all, when establishing the limit failure state of the reinforced member, this paper comprehensively considers the role of the tensile steel bar and steel plate and takes the load effect before reinforcement as the negative contribution of the maximum number of bonded steel plates that can be used for reinforcement. Through the definition of the equivalent tensile strength, equivalent elastic modulus and equivalent yield strain of the tensile steel bar and steel plate, a method to determine the relative limit compression zone height of the reinforced member is obtained. Second, based on the maximum ratio of (reinforcement + steel plate), the relative limit compression zone height and the equivalent tensile strength of the tensile steel bar and steel plate of the reinforced member, the calculation method of the maximum number of bonded steel plates is derived. Then, the static load test of the test beam is carried out and the corresponding numerical model is established, and the reliability of the numerical model is verified by comparison. Finally, the accuracy of the calculation method of the maximum number of bonded steel plates is proved by the numerical model.Findings The numerical simulation results show that when the steel plate width is 800 mm and the thickness is 1–4 mm, the reinforced concrete beam has a delayed yield platform when it reaches the limit state, and the failure mode conforms to the basic stress characteristics of the balanced-reinforced beam. When the steel plate thickness is 5–8 mm, the sudden failure occurs without obvious warning when the reinforced concrete beam reaches the limit state. The failure mode conforms to the basic mechanical characteristics of the super-reinforced beam failure, and the bending moment of the beam failure depends only on the compressive strength of the concrete. The results of the calculation and analysis show that the maximum number of bonded steel plates for reinforced concrete beams in this experiment is 3,487 mm2. When the width of the steel plate is 800 mm, the maximum thickness of the steel plate can be 4.36 mm. That is, when the thickness of the steel plate, the reinforced concrete beam is still the balanced-reinforced beam. When the thickness of the steel plate, the reinforced concrete beam will become a super-reinforced beam after reinforcement. The calculation results are in good agreement with the numerical simulation results, which proves the accuracy of the calculation method.Originality/value This paper presents a method for calculating the maximum number of steel plates attached to the bottom of reinforced concrete beams. First, based on the experimental research, the failure mode of reinforced concrete beams with different number of steel plates is simulated by the numerical model, and then the result of the calculation method is compared with the result of the numerical simulation to ensure the accuracy of the calculation method of the maximum number of bonded steel plates. And the study does not require a large number of experimental samples, which has a certain economy. The research result can be used to control the number of steel plates in similar reinforcement designs.

Dependability of local power systems based on autonomous generation units

Aim. The paper aims to create and verify methods for predicting the dependability of autonomous power supply to local low-power consumers. Methods. The work uses simulation tools, i.e., computational experiment for predicting the dependability and safe service life of autonomous cluster distributed energy networks that include various power generation installations, power transmission lines and an automated self-regulation system for the purpose of diversifying the risks of failure. Results. Using methods of probabilistic analysis of technical system safety, the dependability of power supply is predicted in terms of possible energy network failures and threats to the life of consumers. The problem can be solved by simulating and predicting the moment of failure of a power network, i.e., critical violation of design conditions, accident, etc. This scenario allows – for long periods of operation – simulating failure situations due to degradation and destruction of elements, units, power lines, as well as failures under multidimensional uncertainty of prediction of dependability and quality of power supply. The key output of simulation is a set of recommendations to ensure energy security. The paper presents simulated dependability indicators, analysis of the effect of structural design solutions underlying a distributed energy network on the dependability and energy security. Conclusion. The use of computational experiments and results of power supply dependability simulation as part of predicting probabilistic indicators of failures of equipment and elements of cluster energy networks, identifying their consequences for the energy security of sparsely populated and remote locations lays the foundation for quality management of energy networks. Additionally, in the future, additional causes and initial events may be included in the model for the purpose of studying the facts of failures. For instance, such causes as uneven generation using renewable sources, finite fuel supply for conventional generation sources, reliability of the power grid personnel. The proposed approach allows verifying promising new energy network design solutions, for example, including energy storage systems into a distributed energy network that – at various points in time – may be either “generators” or “consumers”. Simulation of local energy networks is of practical interest and is important for improving their consumer quality, resistance to hazardous environmental effects.

A Numerical Method for the Dynamics Analysis of Blade Fracture Faults in Wind Turbines Using Geometrically Exact Beam Theory and Its Validation

In pursuit of China’s goals for carbon peak and carbon neutrality, wind turbines are continually evolving to achieve a lower levelized cost of energy. The primary technological focus in the wind power industry is on large-scale, lightweight designs for entire turbines to enhance cost competitiveness. However, this advancement has led to an increased risk of blade fractures under extreme operating conditions. This paper addresses this challenging issue by using geometrically exact beam theory to develop a nonlinear simulation model for long, flexible blades. The model accounts for sudden changes in blade properties at the moment of failure, covering both the extensive motions and deformations of the fractured blade. The validation of the proposed model is carried out by comparing the results from power production cases with bladed simulations and further validating the simulations of blade fracture load cases against measurement data. The methodologies and findings presented in this study offer valuable insights for diagnosing faults in wind turbines.

Assessment of the reliability of protective structures made of composite materials

This article discusses the protective structures of dams made of composite materials. The authors propose a method for determining the reliability of structures and illustrate its application using the example of a membrane-cabling structure dam as a system consisting of three main objects: a water-retaining shell, an anchor assembly and an apron. According to this method, the reliability of a structural element is determined by its service life, counted from the start of operation until the moment of failure. It is assumed that the service life of the element is a random variable, and on the basis of this, the distribution law of the service life is chosen, which characterizes the reliability of the element. Based on the analysis of the operating period of membrane-cabling structure dams, new technological solutions of experimental and theoretical studies, the authors have developed scientifically grounded measures to improve the safety and reliability of the operation of the membrane-cabling structure dam. Dependencies are established that characterize the reliability of each element of the dam with a membrane-cabling structure.

Numerical analysis of wood beam bending with verification of breaking force

The work represents the continuation of the research of the maximum bending stress force of a wooden beam up to the moment of failure, which is defined experimentally and with a corresponding mathematical model. The goal was to confirm the accuracy of the mathematical model of the breaking force using numerical simulation and the Solid Works software. Five different types of wood and five different beam thicknesses were used as input parameters whose influence was monitored trough the simulation. The stress deformation state and deflection for the calculated fracture forces were analysed separately for each variant. The breaking force model, which is defined depending on the density of the wood and the thickness of the board, proved to be adequate for defining the maximum stresses and deflections when bending beams.

Effects of fiber orientations on fracture mechanisms in rotary ultrasonic drilling of carbon fiber reinforced plastic laminates

The fracture mechanisms of the carbon fibers seriously depend on fiber orientations which significantly influence the surface quality of carbon fiber reinforced plastics (CFRPs). Rotary ultrasonic drilling (RUD), possessing some excellent characteristics including the superior sidewall quality and high cylindricity error, offers a possibility for the efficient drilling of the CFRP components. In contrast, the effects of fiber orientations on fiber fracture mechanisms are still not fully recognized in RUD of CFRP composites. Incorporated with kinematic characteristics of the abrasive, a novel theoretical model was developed to quantitatively describe the effective orientation of the fiber. Afterwards, the drilling experiments with and without ultrasonic were conducted under the same parameters. The surface topographies of the hole sidewalls at various orientations were comparatively characterized to explore the fiber fracture mechanisms. Subsequently, the influences of these mechanisms and the drilling parameters the surface qualities were also investigated. Moreover, the bending failure mechanisms of the carbon fibers were explored through theoretical analysis. As a result, another fiber fracture mechanism, bending failure, was identified with the smooth fracture and micro-fragmentation topographies at upwind and leeward parts of the fiber cross-section, respectively. Ultrasonic superimposition by means of the immense inertia force of the abrasive promoted the micro-fracture of the carbon fiber. The weaker sustainment from the back-up materials brought about the serious bending failure of fiber oriented at 135°, while the axial load component aggravated the tensile fracture of the carbon fiber with the effective orientation of 45°. The critical moment of the fiber bending failure was also established, by incorporating the beam theory and linear elastic fracture mechanics. The fundamental investigation provided a favorable foundation for further optimizing the parameters to improve the drilling quality and efficiency in formal RUD of CFRP composites.

Experimental study on infrared thermal response characteristics of water-bearing concrete under drop hammer impact

The dynamic impact damage of concrete will lead to serious safety accidents, and the water environment will aggravate the degree of damage. In this paper, an infrared monitoring experimental system for drop hammer impact damage of water-bearing concrete was designed and established. The mechanical properties, infrared radiation temperature (IRT) and infrared thermography of concrete impact damage with different soak time were tested and analyzed. The influence of water on the infrared generation mechanism of concrete was discussed. The results show that water has an initial weakening effect on concrete, which weakens the cementation between concrete particles and aggregate strength, resulting in a decrease in concrete strength. Compared with dry concrete, the infrared temperature of water-bearing concrete increased more during impact damage. With the increase of soak time, the average infrared temperature (AIRT) and the maximum infrared temperature (MIRT) of water-bearing concrete decreased. When dry concrete was damaged, tensile cracks were mainly produced and accompanied by heat absorption. When water-bearing concrete was damaged, high temperature shear cracks appeared. The high temperature generated at the moment of impact failure of water-bearing concrete may be caused by the cavitation phenomenon of water in the microscopic pores of concrete during the drop hammer impact and the combined effect of concrete microstructure damage. The research results are of great significance for monitoring and evaluating the stability of the dynamic evolution process of concrete structures.

Исследование износостойких покрытий, нанесенных на образцы из конструкционной стали, применяемой для изготовления валов валопровода судов на подводных крыльях

Effective interaction of structural elements and materials from which they are made is one of the most important tasks in the design of parts and mechanisms of ship power plants. The operating experience of Meteor-type vessels has shown that the main cause of propeller shaft breakage and failure may be non-compliance with the technical requirements for the chemical-thermal processing of the shaft necks to the bearings size or poor-quality superficial coating. There has been made a comparative analysis of coating technologies, its results will significantly increase the cyclic wear resistance of the surface layer of the shaft necks of the hydrofoil ship shafting. The technologies of gas-plasma and gas-dynamic spraying, as well as electrospark alloying of the surface are considered. An instrumental assessment of the parameters of the applied protective coating quality is performed. Alloying materials for each of the methods of the surface hardening and modification are also presented. The scheme and design of the stand for testing the applied coatings for cyclic fatigue strength up to the moment of critical failure are given. The coatings deposited on the samples surfaces are studied to assess the surface microgeometry and microhardness. The samples are tested on the stand with a cyclic load at an induction motor shaft speed of 1800 rpm (30 rps). A bearing ball made of steel is used as an indenter. After testing, the focus of the coating destruction is assessed visually using a measuring and computing complex based on an optical microscope. As a result of the tests, it is revealed that the samples processed by the electrospark alloying method have the highest resistance to alternating cyclic effects, the lowest surface roughness and the highest microhardness.

Comparative Studies of the Confined Effect of Shear Masonry Walls Made of Autoclaved Aerated Concrete Masonry Units.

Confined walls are popular in areas exposed to seismic action. The advantage of such structures is increased load-bearing capacity, ductility, and energy dissipation. Confined masonry walls are also used to restrain the intensity of cracking and improve load-bearing capacity in areas exposed to seismic action. This paper describes the research on 18 confined walls and presents a comparison with research on unconfined walls (referenced models). The confined models were classified into three series: HOS-C-AAC-without openings and with confining elements around the perimeter; HAS-C1-AAC with a centrally positioned opening and circumferential confinement; and HAS-C2-AAC with a centrally positioned window opening and additional confinement along the vertical edges of the opening. The area of the window opening was 1.5 m2. All walls were made of autoclaved aerated concrete (AAC) masonry units of the nominal density class of 600. The walls were tested under initial compressive stresses σc = 0.1; 0.75; and 1.0 N/mm2. The reference models without confinement (six models of the series HOS-AAC without openings and the series HAS-AAC with openings) were prepared from the same masonry units, had almost the same outer dimensions, and were tested under the same initial compressive stresses σc. The analysis was performed for the morphology of cracks, stress values at the moment of cracking and failure, stiffness, and angles of shear strain. The morphology of cracks was found to depend on initial compressive stresses and the presence of an opening. A significant increase in compressive stress leading to cracks and failure stresses was observed with increasing values of initial compressive stresses. As the wall behavior was clearly non-linear, the bilinear relationship described by energy dissipation E, stiffness at the moment of cracking Kcr, and maximum displacement uu was proposed to be included in the engineering description of the relationship between horizontal load and displacement of confined walls. Confinement along the vertical edges of the opening having an area of 1.5 m2 (acc. to EN 1996-1-1) increased the maximum forces Pmax by ca. 45% and marginally affected the ductility of the wall when compared to the elements with circumferential confinement.

Biomechanical analysis of a novel Y-plate designed for the treatment of extraarticular distal humerus fractures

Adult distal humerus fractures are infrequent, yet they account for one-third of all humerus fractures. For the treatment of comminuted and osteoporotic fractures, locking plates are claimed to be biomechanically superior to alternative internal fixing techniques. Treatment remains difficult despite recent advancements and the use of locking plates due to frequent comminution, low bone quality, and limited healing ability in osteoporotic bone. An optimal design of the newly constructed plate and the control model were selected. The biomechanical characteristics of non-osteoporotic and osteoporotic synthetic bone were compared on six models. The biomechanical properties of the new plate were tested and compared on 54 osteoporotic synthetic humerus models. The control models were reconstructive and parallel LCPs. The tests were carried out under static and dynamic axial, lateral and bending loads. Fracture displacements were measured by optical measuring system Aramis. The test model is significantly stiffer for lateral load (p = 0.0007) and for bending load at the moment of model failure (p = 0.0002), while for axial load the LCP model showed greater stiffness (p = 0.0017). During lateral dynamic loading, all three LCP models broke and there was a significant difference compared to the test model (p = 0.0125). The LCP model is dynamically significantly more durable under axial load, while the largest displacements were recorded with the test model (p = 0.029). The displacements induced by all three loads are within the limits that fulfil the parameters of appropriate biomechanical stability. A novel locking plate for extra-articular distal humerus fractures may provide an alternative to the traditional two-plate.

Axial compressive performances of stiffened composite panels: Experimental and numerical study

Axial compressive performances of stiffened composite panel were studied in this manuscript. In experimental study, buckling phenomenon of three specimens appear at 413kN, 403kN and 403kN respectively while catastrophic failure appears at 964kN, 934kN and 970kN respectively. Thus average failure load is 2.35 times average buckling load, which indicate the large postbuckling capacity. Only local buckling appears in skin bay without buckling in stiffeners. Buckling strain and failure strain were proposed by the average value of several typical position strains at buckling and failure moment respectively. Average failure strain is −6483 με, which is 2.75 times buckling strain (-2354 με). The relationship between buckling and failure strain is similar to that of buckling and failure load. Failure modes contain debonding and fracture of stiffeners, the splitting and wrapped skin. In numerical study, finite element model considering the Hashin damage, cohesive element and geometry imperfection were built. Buckling load and failure load by FE results have −1.2% and −3.9% error compared to experimental ones, indicating the FE results have good accuracy. FE results show that debonding initiation is close to the moment of final catastrophic failure, about 92.7% failure load. Moreover, debonding area percentage have an accelerating increase trend with the compressive load increasing.

Experimental and Numerical Investigations of RC Frame Stability Failure under a Corner Column Removal Scenario

In recent decades, interest in the resistance of buildings and structures to progressive collapse has been increasingly sparked in research communities. Although several experimental, numerical, and analytical research projects on the robustness of building frames under a column removal scenario have been implemented, some aspects of this problem remain understudied. These aspects encompass failure mechanisms of reinforced concrete frames with slender columns, as well as criteria used to evaluate such failures. This paper focuses on experimental and numerical investigations of the structural behavior and failure of a scale reinforced concrete frame with slender columns under a sudden corner column removal scenario. In addition, we analyze the stability failure mechanism of a reinforced concrete frame with slender columns and the tangent stiffness criterion, which allow for evaluation of the ultimate state of a structure subjected to an accidental impact. A scale physical model of a reinforced concrete frame of a multistory building was designed and tested using the theory of functional similarity. For numerical study purposes, a finite element model was made that exactly the same as the test frame. We validated the findings by comparing simulation results and experimental data. The studies on the behavior of a reinforced concrete frame subjected to quasistatic loading with unequal concentrated loads identified the load transfer between columns through beams. Although these effects were minor in the frame under consideration, they can become more significant in cases of long-term loading. Numerical simulation and physical modeling of an accidental impact allowed for identification of the mechanism of load capacity exhaustion triggered by stability failure. Such failure was fragile. The moment of stability failure of the column of the experimental frame corresponded to the extremum on the force–displacement curve, indicating that zero tangent stiffness was reached. Hence, a criterion of tangent stiffness can be proposed for evaluation of the ultimate state of a structure subjected to an accidental impact.