Mechanism Of Stress Transmission Research Articles

Mechanism of stress transmission and feasibility of mining the lower coal seam under repeated mining in close-multiple coal seams

Mining in an upper coal seam results in the redistribution of vertical stress within a lower coal seam until a new equilibrium state is attained. Close-multiple coal seams mining faces the occurrence of multi-goafs and a complex stress environment. Based on a case study of close-multiple coal seams with repeated mining in the Qianjiaying coal mine, a stress distribution model of the floor in the coal seam striking range was established by optimizing the load form of the abutment pressure. The floor stress state after primary and repeated mining of upper coal seams was analyzed in a visual and quantitative manner. The concentrations of vertical stress, horizontal stress, and shear stress are all located in the floor under the coal rib after primary and repeated mining. The curve of stresses gradually levels off as the depth of the floor increases, indicating a diminishing influence of mining-induced stress from the upper coal seam. Based on the stress analysis by numerical simulations, the overall lower coal seam remains in a state of large-scale stress relief. Stress relief occurred twice under repeated mining, which indicates that the lower coal seam has favorable mining feasibility. The results of the study can provide scientific guidance to prevent mining accidents.

Construction of microstructure and nutrient transport properties of tibial segmental implant prosthesis

Segmental tibial bone defects caused by bone tumors, open fractures, and non-union of large bone segments are one of the challenges in orthopedic diseases. In existing research on load-bearing implants, it has been found that stress mismatch at the bone/implant interface leading to implant loosening and biological instability due to limited depth of bone ingrowth are key obstacles to the development of tibial implants. Therefore,In this study, the mechanical properties and internal fluid properties of three existing bone scaffold microstructures were investigated by finite element analysis.Based on the requirements of tibial segmental bone defect scaffolds, a composite scaffold with a GDP pore structure is prepared. The stress transmission mechanism of its microstructure model and the influence of internal scaffold microstructure on the transport of nutrients are studied. The newly proposed GDP pore structure is suitable for segmental bone defects similar to the tibial diaphysis.

Did the grandmother’s exposure to environmental stress during pregnancy affect the birth body size of her grandchildren? The Polish evidence

ABSTRACTThis study aimed to examine whether the exposure of grandmothers (G1s) pregnant with their daughters (G2s) to the harsh conditions of the First World War and the Great Depression influenced the perinatal outcomes of their grandchildren (G3s). We use the data on full-term live births in 1951–1953. The following cohorts are selected: grandmothers (G1s), mothers (G2s), and grandchildren (G3s: males and females). Birth body size (weight, length, and birth body mass index) of G3s born to G2s were compared considering G1s’ period of pregnancy: pre-WWI, WWI, post-WWI, and the Great Depression. We use ART ANOVA to assess statistical differences in birth weight, length, and BMI without and with controlling for co-factors, such as: G2s’ age at delivery, and G3’s gestational age, and birth order. The grandmother’s pregnancy during the harsh conditions of WW I and the Great Depression resulted in the blurring of dimorphic differences in the generation of grandchildren in terms of their birth body size, i.e. weight, length, and BMI. The results demonstrate the potential impact of harsh conditions experienced by grandmothers on the perinatal outcomes of their grandchildren. We do not specify the mechanisms of stress transmission to subsequent generations but assume these are likely to stem from epigenetic mechanisms and/or the G2 mothers’ biological status.

On the load bearing mechanisms of cemented granular material: A mesoscale FE approach

AbstractThe numerical investigation of cemented granular material (CGM) is a demanding task that requires the combination of various scientific disciplines. At the mesoscale, CGM is decomposed into the constituents of particles, cement matrix and void pores. The combination of these constituents, as found in nature or in civil infrastructure projects, creates a highly heterogeneous structure, whose morphology defines the response of the CGM under mechanical loading. The composite internal structure is quantified by means of x‐ray Computed Tomography, which provides 16‐bit grayscale 3D images of the scanned microsamples. These images are decomposed into the three constituent materials to be investigated and modeled. Still, the ability of simple Cartesian grids to adequately carry information about curved geometries and provide accurate representations is questioned. In order to overcome staircase effect errors, the interfaces of the material inclusions are smoothed and re‐defined, making use of Gaussian blurred signed distance fields (SDF). These level‐set derived interfaces serve as a reference for the volume reconstruction of the image via tetrahedra. The comparison of the raw and the smoothened images to analytical geometry Standards suggests that the above reconstruction alleviates the grid's inherited uncertainities. In addition, a comparison between a non smoothed and a smoothed meshed image is performed in terms of mechanical response, utilizing the Finite Element (FE) Method. The results suggest that even a slight change in the granular contact fabric can alter the unfolding stress transmission mechanisms.

Characterizing Seismogenic Fault Structures of the Lake Pertusillo Reservoir Induced Seismicity (Southern Italy) Using a Relocated Template‐Matching Catalog

AbstractWe present a detailed analysis of the small magnitude (ML < 3) Reservoir Induced Seismicity associated with the Pertusillo water reservoir located in the high seismic hazard zone of Val d'Agri (Southern Italy). We apply template‐matching detection to a 13‐month‐long dense passive survey, obtaining a final high‐precision double‐difference catalog of 5,070 earthquakes (−0.7 < ML < 2.6, MC = 0.2). The new catalog allows precisely tracking the spatiotemporal distribution of the swarm‐seismicity and to map the b‐value of the Gutenberg‐Richter law. We combine seismicity data with available subsurface geophysical data, fostering an improved interpretation of the induced seismicity. We identify four seismicity‐clusters showing rapid changes in seismic rate which correlate to severe seasonal oscillations. Seismicity unravels new km‐scale faults or better define faults partially‐illuminated by template earthquakes. b‐value shows a significant spatial variability, with very‐high b‐value (up to 2) within areas of distributed seismicity and lower (∼1.3) b‐value for on‐fault seismicity featuring larger magnitude events. Seismicity is confined within a brine‐saturated fractured carbonate reservoir, while earthquake distribution and rate are controlled by the fault architecture and rock properties (e.g., inherited fluid pathways, rock fracturing, pore fluid pressure). In particular, most earthquakes reactivate, with extensional kinematics, pre‐existing reverse/transpressional faults favorably oriented in the present‐day extension. All observations suggest that a poroelastic stress transmission mechanism, due to the seasonal water level oscillation, can explain the Pertusillo lake seismicity. This study confirms the importance of investigating the complex interaction among stress changes caused by human activities, pre‐existing faults and local stress field to correctly assess the hazard posed by induced seismicity.

Exploring the consequence of information communication technology-enabled work during non-working hours: a stress perspective

PurposeThis study aims to examine the impact of information communication technology-enabled work during non-working hours (ICT-enabled WNWHs), as a source of stress, on employee behavioral outcomes –in-role job performance, organizational citizenship behaviors (OCBs) that benefit organizations and OCBs that benefit individuals, through emotional responses – work exhaustion, nonwork exhaustion and organization-based self-esteem. As the coronavirus disease 2019 (COVID-19) lockdowns demonstrated that employees frequently engage in ICT-enabled WNWHs, studying stress induced by ICT-enabled WNWHs is essential for understanding employee adaptation to the work-from-home trend that emerged from COVID-19 lockdowns.Design/methodology/approachA quantitative survey comprising 1,178 employees in China was conducted, and the data reliability and validity were confirmed. Partial least squares structural equation modeling analysis was employed to test the hypotheses.FindingsThe study results empirically proved that, although ICT-enabled WNWHs had significant effects on employee behavioral outcomes, the related emotional responses were the mediators of the stress transmission mechanism that directly affected employee behavioral outcomes. Notably, work exhaustion and organization-based self-esteem partially mediate the stress transmission mechanism, while nonwork exhaustion exerts a full mediating effect.Originality/valueThis study proposes the stress transmission mechanism of ICT-enabled WNWHs and delineates emotional responses regarding the work environment attributes of ICT-enabled WNWHs, an approach rarely seen in prior IS studies. To our best knowledge, this study is the first to identify and empirically demonstrate organization-based self-esteem as one among the emotional responses to ICT-enabled WNWHs. Furthermore, it expands understanding of the holistic impacts of ICT-enabled WNWHs, which is lacking in information systems (IS) literature.

Numerical Study of Stress Distribution in Soft Clay Treated with Stone Column

This study used a finite element analysis approach employing Plaxis 3D to analyze the stress concentration ratio, a critical parameter in geotechnical engineering, to examine stresses operating on stone columns and soft soils. This study also looked at the effect of the stiffness ratio between the stone column and the neighboring soil. With the same length and three different diameters, 0.8 m, 1.0 m, and 1.2 m, or three area replacement ratios ranging from 7% to 16%, respectively, floating and end-bearing stone columns were used. The influence of soft soil undrained cohesion, cu ranging from 6 kPa to 40 kPa, was also considered in the current study. The stiffness ratio for columns to adjacent soil, end bearing or floating stone column, and area ratio all have a significant impression on the performance of the stone column in treating soft soil and stress transmission mechanisms in the enhanced soil body, according to parametric studies. The average stress concentration ratio in soil improved with an end-bearing stone column of φ= 35° and raised to 2.63 and 4.71 at φ = 50°, ranging from 1.41 to 2.35 for area replacement ratios of 7% and 16%.

Mechanical properties of shear-type hysteretic dampers supported by studs

The shear-type hysteretic damper of an energy-absorbing member reduces the damage to the main member, such as column or beam, by absorbing seismic energy as the shear deformation of steel. As a support element for connecting the damper to the structure, brace-type and stud-type systems are mainly used. In the stud support, the stress transmission mechanism to the damper is simple, and the degrees of freedom of the plane are higher than that of the other support types. For such a shear-type damper, an H-shaped cross-section with a panel made of a highly ductile material, such as a low-yield-point steel, is generally adopted. This study used a low-yield-point steel circular hollow-section damper, which was installed in the frame as a stud support form, and a case was used to receive the in-plane force. For the damper to function effectively in the frame, it was necessary to determine the elastoplastic mechanical properties of the damper and the dampers supported by the stud. The mechanical properties of the damper unit and damper system with the stud were examined by cyclic loading test. An H-shaped shear panel damper was used as the control group with almost the same full plastic shear strength, initial stiffness, and weight as the circular hollow-section damper and the cyclic loading test was conducted under the same conditions. The effectiveness of the low-yield-point steel circular hollow-section damper was examined as a shear-type hysteretic damper by comparing both. In addition, a nonlinear finite element analysis was performed to determine the influence of the initial stiffness on the damper supported by the stud.

STUDY ON STRESS TRANSFER AT BEAM-TO-COLUMN CONNECTIONS COMPOSED OF STEEL AND CONCRETE COMPOSITE COLUMNS AND STEEL BEAMS

The authors have investigated the elastic-plastic behavior of the steel and concrete composite columns (SC column) and the beam-to-column connections composed SC columns and wide flange beams against severe earthquakes. The SC column is an octagonal sectional column composed of cross-shaped steel and concrete. A pulling experiment of connection for SC columns and steel flanges was carried out in order to make clear the difference of welded connection details on the behaviors of connection between a column flange and a beam flange with outer diaphragms and band-plates. The authors have performed FEM analysis and performed a comparison with the experiment behavior, and have made clear the difference of connection details on the behavior of frameworks quantitatively by performing numerical analysis. From these results, we will discuss the design method for beam-to-column connection composed of SC columns and wide flange beam where stress transmission mechanism is clear, and construction is simple.

STUDY ON STRESS TRANSFER AT BEAM-TO-COLUMN CONNECTIONS COMPOSED OF STEEL AND CONCRETE COMPOSITE COLUMNS AND STEEL BEAMS

The authors have investigated the elastic-plastic behavior of the steel and concrete composite columns (SC column) and the beam-to-column connections composed SC columns and wide flange beams against severe earthquakes. The SC column is an octagonal sectional column composed of cross-shaped steel and concrete. A pulling experiment of connection for SC columns and steel flanges was carried out in order to make clear the difference of welded connection details on the behaviors of connection between a column flange and a beam flange with outer diaphragms and band-plates. The authors have performed FEM analysis and performed a comparison with the experiment behavior, and have made clear the difference of connection details on the behavior of frameworks quantitatively by performing numerical analysis. From these results, we will discuss the design method for beam-to-column connection composed of SC columns and wide flange beam where stress transmission mechanism is clear, and construction is simple.

The Mental Well-Being of Young Children and Families at the Beginning of the COVID-19 Pandemic in Germany

Abstract. During the spring of 2020, the lockdown in Europe, enacted as a countermeasure to the COVID-19 pandemic, dramatically changed the social and daily life of young families. This online study explored the potential consequences of these unprecedented circumstances for the well-being of young German families. Caregivers completed a standardized questionnaire on their positive mental well-being and open-ended questions referring to their family situation and children. Although there is an emerging body of research describing pandemic-related outcomes in older children, little is known about its impact during early development. Hence, our analyses focused on a subset of caregivers of N = 798 children aged 0 to 23 months. Answers to open-ended questions revealed predominantly negative changes in their children and family life as a whole. During the lockdown, the well-being of the caregivers decreased. Taken together, the data show that social changes caused by the lockdown affected the well-being of young families. Potential mechanisms of stress transmission between parents and children are discussed.

Fiber engagement accounts for geometry-dependent annulus fibrosus mechanics: A multiscale, Structure-Based Finite Element Study

A comprehensive understanding of biological tissue mechanics is crucial for designing engineered tissues that aim to recapitulate native tissue behavior. Tensile mechanics of many fiber-reinforced tissues have been shown to depend on specimen geometry, which makes it challenging to compare data between studies. In this study, a validated multiscale, structure-based finite element model was used to evaluate the effect of specimen geometry on multiscale annulus fibrosus tensile mechanics through a fiber engagement analysis. The relationships between specimen geometry and modulus, Poisson's ratio, tissue stress–strain distributions, and fiber reorientation behaviors were investigated at both tissue and sub-tissue levels. It was observed that annulus fibrosus tissue level tensile properties and stress transmission mechanisms were dependent on specimen geometry. The model also demonstrated that the contribution of fiber–matrix interactions to tissue mechanical response was specimen size- and orientation-dependent. The results of this study reinforce the benefits of structure-based finite element modeling in studies investigating multiscale tissue mechanics. This approach also provides guidelines for developing optimal combined computational-experimental study designs for investigating fiber-reinforced biological tissue mechanics. Additionally, findings from this study help explain the geometry dependence of annulus fibrosus tensile mechanics previously reported in the literature, providing a more fundamental and comprehensive understanding of tissue mechanical behavior. In conclusion, the methods presented here can be used in conjunction with experimental tissue level data to simultaneously investigate tissue and sub-tissue scale mechanics, which is important as the field of soft tissue biomechanics advances toward studies that focus on diminishing length scales.

The multi-modal responses of a physical head model subjected to various blast exposure conditions

The local and global biomechanical response of the body to a blast wave is the first step of a sequence that leads to the development of stresses and strains which can exceed the tolerance of brain tissue. These stresses and strains may then lead to neuro-physical changes in the brain and contribute to initiate a cascade of events leading to injury. The specific biomechanical pathways by which the blast energy is transmitted through the head structure are, however, not clearly understood. Multiple transmission mechanisms have been proposed to explain the generation of brain stresses following the impingement of a blast wave on the head. With the use of a physical head model, the work presented here aims at demonstrating that the proposed transmission mechanisms are not mutually exclusive. They are part of a continuum of head responses where, depending on the exposure conditions, a given mechanism may or may not dominate. This article presents the joint analysis of previous blast test results generated with the brain injury protection evaluation device (BIPED) headform under four significantly different exposure conditions. The focus of the analysis is to demonstrate how the nature of the recorded response is highly dependent on the exposure characteristics and consequently, on the method used to reproduce blast exposure in a laboratory environment. The timing and magnitude of the variations in intra-cranial pressures (ICP) were analysed relative to the external pressure field in order to better understand the wave dynamics occurring within the brain structure of the headform. ICP waveforms were also analysed in terms of their energy spectral density to better identify the energy partitioning between the different modes of response. It is shown that the BIPED response is multi-modal and that the energy partitioning between its different modes of response is greatly influenced by exposure characteristics such as external peak overpressure, impulse, blast wave structure, and direction of propagation. Convincing evidence of stresses generated from local skull deformation is presented along with evidence of stress transmission through relative brain-to-skull motion. These findings suggest that research aimed at defining exposure thresholds should not focus on a single stress transmission mechanism or use experimental designs unrepresentative of realistic blast loading conditions that may favour a given mechanism over another.

A micro finite-element model for soil behaviour

This paper describes a numerical model that virtualises the fabric of a natural sand obtained from micro computed tomography (μCT) to simulate the mechanical response of the material, termed here a micro finite-element (μFE) model. The grain-to-grain interactions under loading are modelled in a framework of combined discrete–finite-element method. The basis of this approach is that using a true representation of soil fabric and deformable grains will enable a more realistic representation of the physics of granular behaviour. Each individual grain is represented in a numerical mesh and modelled as a continuum body allowed to deform according to a prescribed constitutive model with appropriate friction contact conditions. An important feature of this model is the ability to compute the map of stress distribution inside the grains. A case study of an intact sand subjected to oedometer compression is presented to demonstrate the insights that can be gained into the stress transmission mechanisms and yield initiation within the grains. The displacement field, inertia tensor and active contact number are used to quantify grain kinematics as the virtual fabric deforms. By coupling contact dynamics with contact topology, this approach provides a robust numerical tool to infer important grain scale parameters that link the micro phenomena to the macro response of soil.

Image-based investigation into the primary fabric of stress-transmitting particles in sand

This paper uses three-dimensional images of a natural silica sand to analyse the mechanisms of stress transmission under triaxial compression. As discussed in Fonseca, J., O’Sullivan, C., Coop, M., Lee, P.D., (2012), the irregular morphology and locked fabric that can be found in natural sands lead to the formation of contacts with extended surface areas. However, most of our current understanding of stress-transmission phenomena comes from DEM simulations and photo-elastic experiments using idealised grain shapes and contact topologies. The direct measurement of stress transmission in assemblies of real soil grains is a challenging task. The present study postulates that important insight can be obtained by following the evolution of intergranular contacts as the grains rearrange and by considering how these rearrangements enhance the stability of the material. The methodology consists of measuring the geometrical data of the individual grains and their associated contacts obtained at successive load stages in the post-peak regime (after shear band formation). A statistical analysis of the vectors normal to the contacts reveals a realignment of these vectors in the direction of the major principal stress; this is a clear indication of the formation of force chains. A subsequent analysis shows that these columnar structures of stress-transmitting grains are associated with larger contact surfaces and have distinct patterns in the regions affected by the formation of a shear band. An algorithm based on stability and load-transmission criteria is developed to contribute new insight into the characterisation of load-bearing sand particles.

Highly sensitive nanomechanical assay for the stress transmission of carbon chain

Here, we report the first quantitative experimental study into the molecular basis of the transmission of mechanical signal that originates from biochemical reaction focusing on the length of carbon chain. We designed an experiment by using n-alkanethiols with a same carboxyl group and different chain lengths (n=1, 5, 10 and 15) to immobilize a same receptor molecule on the gold surface of a microcantilever, and detected the nanomechanical response of biochemical reaction. The sensitivity of the microcantilever was found to be greatly influenced by the chain length of linker that is between the receptor molecule and the microcantilever surface. The efficiency of stress transmission increases significantly with decreasing length of carbon chain. At the same time, we develop a label-free microcantilever sensor for highly sensitive detection of Glycyrrhizic acid (GL). The detection limit of the microcantilever sensor for GL is found to be as low as 20pg/mL for the shortest linker (n=1), which is 500 times lower than the longest linker (n=15) and 50 times lower than that of the corresponding icELISA. These findings will provide new insights into the fundamental mechanisms of stress transmission, which may be exploited for biochemical sensor and nanoactuation applications.

Contact impingement in packings of elastic–plastic spheres, application to powder compaction

High-density compaction of ductile powder particles is characterized by a sharp increase of the inter-particle normal contact force. This is due to both complex contact interactions and plastic incompressibility of the particle constitutive material. A DEM model (OPEN-DEM YADE) using an interaction force-law reproducing this increase has been developed to simulate high-density compaction of ductile powders. Its formulation is derived from a Finite Element Method model (ABAQUS). Macroscopic stresses resulting from compaction tests carried out on a random assembly of spherical grains were computed with both models and then compared. A good agreement between the stress–density curves confirmed the accuracy of the DEM formulation. However, the role of the grain deformation may not be well described using DEM since it is based on an assumption of overlapping rigid particles but allows low calculation costs. To highlight the role of this deformation process, a detailed FEM-based analysis of the influence of contact impingement on the normal contact force is thus presented. It explores the mechanisms of stress transmission between contact zones and quantifies the appearance of contact interactions in terms of both indentation depth and relative density. Results show that contact impingement cannot be neglected at a relative density as low as 0.7 if a local, contact-scale analysis is aimed for (such as density distribution for instance). In such a case, previous models like the one proposed by Storåkers and co-authors, should be used with care. The local solid fraction provides a correct local description of both contact interactions and plastic incompressibility of the constitutive material of the grains up to the maximum density. This would allow the DEM to be successfully applied to large-scale simulations of high-density compaction.

Stress Transmission Mechanism in RC Footing Beam Supporting Exposed-type Corn Base with Unbonded Anchor Bolts

Stress Transmission Mechanism in RC Footing Beam Supporting Exposed-type Corn Base with Unbonded Anchor Bolts

Molecular Biomechanics: The Molecular Basis of How Forces Regulate Cellular Function

Recent advances have led to the emergence of molecular biomechanics as an essential element of modern biology. These efforts focus on theoretical and experimental studies of the mechanics of proteins and nucleic acids, and the understanding of the molecular mechanisms of stress transmission, mechanosensing and mechanotransduction in living cells. In particular, single-molecule biomechanics studies of proteins and DNA, and mechanochemical coupling in biomolecular motors have demonstrated the critical importance of molecular mechanics as a new frontier in bioengineering and life sciences. To stimulate a more systematic study of the basic issues in molecular biomechanics, and attract a broader range of researchers to enter this emerging field, here we discuss its significance and relevance, describe the important issues to be addressed and the most critical questions to be answered, summarize both experimental and theoretical/computational challenges, and identify some short-term and long-term goals for the field. The needs to train young researchers in molecular biomechanics with a broader knowledge base, and to bridge and integrate molecular, subcellular and cellular level studies of biomechanics are articulated.

Stress transmission of retrofitted concrete columns to jackets

Concrete jacketing is one of the most common retrofitting techniques for concrete columns. However, the stress transmission mechanisms of this system are still not fully understood and appropriate design procedures are still not established. In this experimental study eight jacketed columns with different stirrup arrangements and various bonding conditions were tested in order to analyse the failure mechanisms of these members. It was observed that in rectangular columns 60% of the load is transmitted across the corners and the remaining 40% across the sides. The stress transmission from the column to the jacket depends on shear capacity at the interface. The applicability of the ACI 318-05 shear-friction model is also evaluated. According to this model, reinforcement must be provided across the contact surface to resist the relative displacement across it. Despite this limitation, it is shown that the Mattock formulation can be applied with minor modifications for the design of concrete jackets, and that the experimental results show reasonable agreement with calculated values.